Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33403 Publications

Process Metallurgy: A key enabler of a Circular Economy

Reuter, M. A.
Base metals such as copper, lead, nickel, cobalt, zinc etc. form the basic crucial carrier metals for a sustainable society – the Web of Metals. This paper discusses the special and crucial role these metals have in acting as enablers in any recycling efforts as they carry and release important and vital minor elements at the heart of high-tech applications and products. Through examination of the rising needs for such carriers, this paper examines the approach and technologies which need to be considered by any producer of base metals. Attention is paid to the limits and extent of this carrier role in the typical processing of materials.
Examples of specialised technology and flowsheet needs are presented with consideration given to a “whole of chain” or Systems-Integrated Metal Production (SIMP) approach as a cornerstone of a circular economy. Also outlined are the challenges facing not only producers, but legislators who need to consider the balance between providing our societal needs with baseline technology infrastructure requirements for valuable metals extraction. In summary, the message of this paper states simply that not only is the criticality of metals important but the criticality of the infrastructure (Infrastructure Criticality) that can recover metals from complex designed “mineral” mixtures. Base metals are at the heart of a Circular Economy, therefore key enablers of the Internet-of-Metallurgical-Things.
Keywords: Resource efficiency base metals, Recycling, System integration, Design for Recycling (DfR)
  • Invited lecture (Conferences)
    Resourcing Future Generations Symposium / International Geological Conference ICG35, 27.08.-04.09.2016, Kapstadt, Südafrika

Permalink: https://www.hzdr.de/publications/Publ-24577
Publ.-Id: 24577


Formation of Co nanodisc with enhanced perpendicular magnetic anisotropy driven by Ga+ ion irradiation on Pt/Co/Pt films

Sakamaki, M.; Amemiya, K.; Sveklo, I.; Mazalski, P.; Liedke, M. O.; Fassbender, J.ORC; Kurant, Z.; Wawro, A.; Maziewski, A.
The origin of magnetic phase transition from in-plane to perpendicular magnetic anisotropy (PMA) of Pt/Co/Pt thin film by Ga+ ion irradiation at fluences of 1-5 x 10(15) ions/cm(2) is investigated by means of x-ray magnetic circular dichroism (XMCD) and extended x-ray absorption fine structure (EXAFS) analyses. We find that Pt and Co atoms are mixed with each other and that Co is oxidized near the surface due to removal of the Pt overlayer. Furthermore, polarization-dependent EXAFS analysis shows that Co is firstly dispersed as separated single-atom-thick sheets in a Pt matrix at 1 x 10(15) ions/cm(2), then the Co sheets are divided into a few angstrom clusters at 5 x 10(15) ions/cm(2), which are regarded as nanodiscs parallel to the film plane. This process is accompanied by the appearance of an out-of-plane magnetization component and a remanence peak is observed. Because we do not observe an enhancement in anisotropy of Co orbital moment which leads to change in magnetic anisotropy through the transition at about 5 x 10(15) ions/cm(2), it might be possible that such nanodisc formation induces increase of magnetic anisotropy via a shape effect. By comparing with the phase transition observed at lower fluence [Phys. Rev. B 86, 024418 (2012)], we find that the mechanism of two transitions is different, i.e., the transition at lower fluence is caused by anisotropy of orbital moment due to structural strain, while the present transition is possibly by shape effect due to nanodisc formation.

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Permalink: https://www.hzdr.de/publications/Publ-24576
Publ.-Id: 24576


Opportunities and limits of metal recycling within a circular economy

Reuter, M. A.
Metallurgy is at the heart of developing a circular economy as metals all have strong intrinsic recycling potentials. Moving towards closed material-loops requires for the metallurgical industry to continue to refine its processing methods and adapt to the changing and ever complicating waste fractions.
  • Invited lecture (Conferences)
    Metal recycling, opportunities and limits / MiMa Meeting, 26.05.2016, Copenhagen, Denmark

Permalink: https://www.hzdr.de/publications/Publ-24575
Publ.-Id: 24575


Stability of uranium(VI) doped CSH phases in high saline water

Wolter, J.-M.; Schmeide, K.; Stumpf, T.
To evaluate the long-term stability of U(VI) doped CSH phases at high saline conditions, leaching experiments with NaCl, NaCl/Na2SO4 and NaCl/NaHCO3 containing solutions were performed. Time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR) and X-ray powder diffraction (XRD) were applied to study the U(VI) binding onto the CSH phases and to get a deeper understanding of structural changes due to leaching. Results indicate that neither NaCl nor Na2SO4 affect the structural stability of CSH phases and their retention potential for U(VI). However, carbonate containing solutions lead to a decomposition of CSH phases and thus, to a release of uranium.
Keywords: CSH, stability, uranium, U(VI), saline water, sodium chloride, carbonate, sulfate, TRLFS, IR, PXRD
  • Lecture (others)
    Kompetenzzentrum Ost für Kerntechnik Seminar für Doktoranden und Nachwuchswissenschaftler, 08.12.2016, Dresden-Rossendorf (HZDR), Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24574
Publ.-Id: 24574


Transient eddy current flow metering: a calibration-free measurement technique for liquid metals

Krauter, N.; Forbriger, J.; Stefani, F.
Eddy Current Flow Meters (ECFM) are widely used for the contactless measurement of the velocity of conductive fluids, but extensive calibration is necessary in order to get accurate results. The measured magnitudes or phase shifts are also influenced by the temperature dependent electrical conductivity. A new approach to this kind of velocity measurement is Transient Eddy Current Flow Metering (TEC-FM), which yields the fluid velocity without prior calibration. With this sensor concept it is possible to track the position of an imprinted eddy current system, which is moving with the same velocity as the conductive fluid, and thereby eliminating the need for additional calibration and temperature compensation. We delineate the basic principle of the technique, present one specific sensor configuration, and discuss first experimental results.
Keywords: inductive flow measurement, eddy current, calibration-free
  • Contribution to proceedings
    10th PAMIR International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italien
    Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, University of Cagliari: Department Electrical and Electronic Engineering, 978-88-90551-93-2, 48-51
  • Lecture (Conference)
    10th PAMIR International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italien

Permalink: https://www.hzdr.de/publications/Publ-24573
Publ.-Id: 24573


Accumulative Magnetic Switching of Ultrahigh-Density Recording Media by Circularly Polarized Light

Takahashi, Y. K.; Medapalli, R.; Kasai, S.; Wang, J.; Ishioka, K.; Wee, S. H.; Hellwig, O.; Hono, K.; Fullerton, E. E.
Magnetization control of ferromagnetic materials only by circularly polarized light has received increasing attention both as a fundamental probe of the interactions of light and magnetism but also for future highdensity magnetic recording technologies. Here we show that for granular FePt films designed for ultrahighdensity magnetic recording, the optical magnetic switching by circularly polarized light is an accumulative effect from multiple optical pulses. The measured results can be reproduced by a simple statistical model where the probability of switching a grain depends on the helicity of the optical pulses.We further show the deterministic switching of high-anisotropy materials by the combination of circularly polarized light and modest external magnetic fields, thus, revealing a pathway towards technological implementation.

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Permalink: https://www.hzdr.de/publications/Publ-24572
Publ.-Id: 24572


Helicity and field dependent magnetization dynamics of ferromagnetic Co/Pt multilayers

Tsema, Y.; Kichin, G.; Hellwig, O.; Mehta, V.; Kimel, A. V.; Kirilyuk, A.; Rasing, T.
We present helicity and field dependent magnetization dynamics of ferromagnetic Co/Pt multilayers, suitable for all-optical helicity-dependent switching. Employing single-shot time-resolved magnetooptical Kerr effect imaging, our study demonstrates an ultra-fast quenching of the magnetization after a single 60 fs laser pulse excitation followed by a recovery. Full demagnetization occurs within 1 ps after laser excitation. The magnetization dynamics reveals a small helicity dependence caused by magnetic circular dichroism. When an external magnetic field is applied, a heat-assisted magnetization reversal occurs on a nanosecond time scale.

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Permalink: https://www.hzdr.de/publications/Publ-24571
Publ.-Id: 24571


Untersuchungen zum Komplexierungsverhalten modifizierter Calix[4]arene gegenüber Uran(VI) und Thorium(IV)

Bauer, A.; Schmeide, K.
Projekttreffen des BMBF Verbundprojektes "SE-FLECX"
Präsentation spektroskopischer und mikrokalorimetrischer Studien zur Wechselwirkung von Calix[4]aren-basierten Liganden mit Uran(VI) und Thorium(IV).
Keywords: Calix[4]arene, Uran(VI), Thorium(IV)
  • Lecture (others)
    Projekttreffen des BMBF Verbundprojektes "SE-FLECX", 15.11.2016, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24570
Publ.-Id: 24570


Influence of chemical ordering on the thermal conductivity and electronic relaxation in FePt thin films in heat assisted magnetic recording applications

Giri, A.; Hunwee, S.; Jain, S.; Hellwig, O.; Hopkins, P. E.
We report on the out-of-plane thermal conductivities of tetragonal L10 FePt (001) easy-axis and cubic A1 FePt thin films via time-domain thermoreflectance over a temperature range from 133K to 500K.
The out-of-plane thermal conductivity of the chemically ordered L10 phase with alternating Fe and Pt layers is ~23% greater than the thermal conductivity of the disordered A1 phase at room temperature and below. However, as temperature is increased above room temperature, the thermal conductivities of the two phases begin to converge. Molecular dynamics simulations on model FePt structures support our experimental findings and help shed more light into the relative vibrational thermal transport properties of the L10 and A1 phases. Furthermore, unlike the varying temperature trends in the thermal conductivities of the two phases, the electronic scattering rates in the out-of-plane direction of the two phases are similar for the temperature range studied in this work.

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Permalink: https://www.hzdr.de/publications/Publ-24569
Publ.-Id: 24569


Model-based magnetization retrieval from holographic phase images

Röder, F.; Vogel, K.; Wolf, D.; Hellwig, O.; Wee, S. H.; Wicht, S.; Rellinghaus, B.
The phase shift of the electron wave is a useful measure for the projected magnetic flux density of magnetic objects at the nanometer scale. More important for materials science, however, is the knowledge about the magnetization in a magnetic nano-structure. As demonstrated here, a dominating presence of stray fields prohibits a direct interpretation of the phase in terms of magnetization modulus and direction. We therefore present a model-based approach for retrieving the magnetization by considering the projected shape of the nano-structure and assuming a homogeneous magnetization therein. We apply this method to FePt nano-islands epitaxially grown on a SrTiO3 substrate, which indicates an inclination of their magnetization direction relative to the structural easy magnetic [001] axis. By means of this real-world example, we discuss prospects and limits of this approach.
Keywords: off-axis electron holography, magnetic imaging, FePt nano-structured film

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Permalink: https://www.hzdr.de/publications/Publ-24568
Publ.-Id: 24568


Ultrafast dynamics in VO2 under high pressures

Braun, J. M.; Schneider, H.; Helm, M.; Boatner, L. A.ORC; Marvel, R. E.; Haglund, R. F.; Pashkin, A.
Ultrafast dynamics in VO2 under high pressures
Keywords: optical pump - THz probe spectroscopy, insulator-to-metal transition, high pressure, diamond anvil cell, vanadium dioxide, VO2, pressure-induced metallization
  • Poster
    NextGen@Helmholtz 2016 Conference, 28.-30.09.2016, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24567
Publ.-Id: 24567


Structural and functional properties of ion-irradiated graphene-reinforced elastomers

Jagielski, J.; Ostaszewska, U.; Kozinski, R.; Hassa-Zaloba, A.; Romaniec, M.; Kurpaska, L.; Kosinska, A.; Grambole, D.; Jozwik, I.
Since more than half century ion beams are used for modification of functional properties of various materials: after semiconductors, metals and ceramics ion irradiation appeared recently as an interesting method of modification of organic materials, especially for friction and wear properties. Among polymeric materials the newest area of applications of ion beams is their use for modification of elastomers, commonly known as rubbers. Main structural effect caused by heavy ions in polymers is a massive loss of hydrogen from the surface layer, this leads to a smoothening and shrinking of the sample surface. The paper describes the results obtained in several rubbers modified by ion beams. Both, pristine and graphene-reinforced rubber samples were used, graphene doping led to the strengthening of the material bulk whereas ion irradiation allowed for surface property improvement. In the first part of the paper the hydrogen release from irradiated elastomers is shortly presented. Mechanical properties (hardness and friction) are discussed in the second part.

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Permalink: https://www.hzdr.de/publications/Publ-24566
Publ.-Id: 24566


TOPFLOW-Experimente, Modellentwicklung und Validierung zur Qualifizierung von CFD-Codes für Zweiphasenströmungen - Abschlussbericht

Lucas, D.; Beyer, M.; Banowski, M.; Seidel, T.; Krepper, E.; Liao, Y.; Apanasevich, P.; Gauß, F.; Ma, T.
Der vorliegende Bericht gibt einen zusammenfassenden Überblick der im Vorhaben erreichten Ergebnisse. Ziel war die Qualifikation von CFD-Methoden für Zweiphasenströmungen mit Phasenüber¬gang. Dafür werden neuartige experimentelle Daten benötigt. Diese können an der TOPFLOW-Anlage des HZDR generiert werden, da die Anlage Experimente in für die Reaktorsicher-heits¬forschung relevanten Skalen und Parametern mit innovativen Messtechniken verbindet.
Die experimentellen Arbeiten umfassen Untersuchungen zu Strömungen in vertikalen Rohren mit Hilfe der ultraschnellen Röntgentomographie, zu Strömungen mit und ohne Phasenübergang in einem Testbassin sowie zur Gegenstrombegrenzung in einem Heißstrangmodell. Diese werden im vorliegenden Bericht nur kurz dargestellt, da es zu allen 3 Versuchsserien ausführliche Dokumentationen in separaten Berichten gibt.
Ein wichtiges Ergebnis der Arbeiten zur CFD-Qualifizierung ist der Erstellung des Baseline-Modellkonzepts sowie die Erstellung des Baseline-Modells für polydisperse Blasenströmungen. Damit wird ein wesentlicher Beitrag zur Erhöhung der Vorhersagefähigkeit von CFD-Codes auf Basis des Zwei- oder Mehr-Fluid-Modells erreicht.
Das innovative Generalized Two-Phase Flow Konzept (GENTOP) zielt hingegen auf eine Erweiterung der Einsatzmöglichkeiten der Zweiphasen-CFD. In vielen Strömungen treten unterschiedlicher Morphologien der Phasen bzw. Strömungsformen parallel in einer Strömungsdomäne auf. Außerdem gibt es Übergänge zwischen diesen Morphologien. Mit dem GENTOP-Konzept wurde erstmals ein Rahmen geschaffen der die Simulation solcher Strömungen auf konsistente Art und Weise ermöglicht. Spezielle Modellentwicklungen erfolgten mit dem Ziel einer besseren Modellierung des Phasenübergangs.
Keywords: CFD, Zweiphasenströmung, Experiment, Phasenübergang, Blasenströmung, separierte Strömung
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-077 2016
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-24565
Publ.-Id: 24565


Two-Phase Flow Experiments on Counter-Current Flow Limitation in a model of the Hot Leg of a Pressurized Water Reactor (2015 test series)

Beyer, M.; Lucas, D.; Pietruske, H.; Szalinski, L.
Counter-Current Flow Limitation (CCFL) is of importance for PWR safety analyses in several accident scenarios connected with loss of coolant. Basing on the experiences obtained during a first series of hot leg tests now new experiments on counter-current flow limitation were conducted in the TOPFLOW pressure vessel. The test series comprises air-water tests at 1 and 2 bar as well as steam-water tests at 10, 25 and 50 bar. During the experiments the flow structure was observed along the hot leg model using a high-speed camera and web-cams. In addition pressure was measured at several positions along the horizontal part and the water levels in the reactor-simulator and steam-generator-simulator tanks were determined.
This report documents the experimental setup including the description of operational and special measuring techniques, the experimental procedure and the data obtained.
From these data flooding curves were obtained basing on the Wallis parameter. The results show a slight shift of the curves in dependency of the pressure. In addition a slight decrease of the slope was found with increasing pressure. Additional investigations concern the effects of hysteresis and the frequencies of liquid slugs. The latter ones show a dependency on pressure and the mass flow rate of the injected water.
The data are available for CFD-model development and validation.
Keywords: experiment, CFD, two-phase flow, counter-current flow limitation, flooding characteristic, slug frequency
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-076 2016
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-24564
Publ.-Id: 24564


Experiments on vertical gas-liquid pipe flows using ultrafast X-ray tomography

Banowski, M.; Beyer, M.; Lucas, D.; Hoppe, D.; Barthel, F.
For the qualification and validation of two-phase CFD-models for medium and large-scale industrial applications dedicated experiments providing data with high temporal and spatial resolution are required. Fluid dynamic parameter like gas volume fraction, bubble size distribution, velocity or turbulent kinetic energy should be measured locally. Considering the fact, that the used measurement techniques should not affect the flow characteristics, radiation based tomographic methods are the favourite candidate for such measurements. Here the recently developed ultrafast X-ray tomography, is applied to measure the local and temporal gas volume fraction distribution in a vertical pipe. To obtain the required frame rate a rotating X-ray source by a massless electron beam and a static detector ring are used.
Experiments on a vertical pipe are well suited for development and validation of closure models for two-phase flows. While vertical pipe flows are axially symmetrically, the boundary conditions are well defined. The evolution of the flow along the pipe can be investigated as well.
This report documents the experiments done for co-current upwards and downwards air-water and steam-water flows as well as for counter-current air-water flows. The details of the setup, measuring technique and data evaluation are given. The report also includes a discussion on selected results obtained and on uncertainties.
Keywords: experiment, CFD, two-phase flow, pipe flow, tomography
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-075 2016
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-24563
Publ.-Id: 24563


Major and Trace Element Geochemistry of the European Kupferschiefer – An Evaluation of Analytical Techniques

Rahfeld, A.; Wiehl, N.; Dreßler, S.; Möckel, R.; Gutzmer, J.
Simple and rapid techniques are needed for routine quantitative chemical bulk-rock analyses of Kupferschiefer, a black shale containing variable amounts of silicates, base metal sulphides, carbonates and an organic content of up to 30 weight percent. In this study, WD-XRF, TXRF, and ICP-OES of acid- as well as peroxide-digested samples were tested as potential techniques based on their availability and adaptability to analyse major (Si, Ti, Al, Mg, Ca, Fe, K, but also Cu, Zn, Pb) and selected trace (Ag, As, Ba, Co, Mo, Ni, V) element concentrations. Because of the absence of a suitable reference material, a comparative study was undertaken using instrumental neutron activation analysis to ascertain the accuracy of different approaches. Our results suggest that data from ICP-OES were much higher in accuracy compared to INAA than those from WD-XRF and TXRF, independent of the digestion procedure. The choice of digestion procedure is reflected in low detection limits but an underestimation of Cu, Ag, Co, and V concentrations reported by ICP-OES relative to those obtained by INAA in the case of acid digestion and increased detection limits coupled with a loss of over 25 % Ag relative to INAA for peroxide digestion.
Keywords: black shale, ICP-OES, WD-XRF, INAA, whole-rock geochemistry, sulphides, copper ores

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Permalink: https://www.hzdr.de/publications/Publ-24562
Publ.-Id: 24562


Untersuchungen zum Komplexierungsverhalten der modifizierten Calix[4]arene gegenüber Uran(VI)

Bauer, A.; Schmeide, K.
Vortrag zum Projekttreffen des BMBF Verbundprojektes "SE-FLECX".
Präsentation erster Ergebnisse zu Wechselwirkungsstudien von Uran(VI) mit Calix[4]arenen in nichtwässrigen Sytemen.
  • Lecture (others)
    Projekttreffen des BMBF-Verbundprojektes "SE-FLECX", 26.11.2015, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24561
Publ.-Id: 24561


Numeric simulations of a liquid metal model of a bloom caster under the effect of rotary electromagnetic stirring

Barna, M.; Javurek, M.; Willers, B.; Eckert, S.; Reiter, J.
At the voestalpine Stahl Donawitz GmbH the continuous casting of round steel blooms is commonly supported by electromagnetically induced stirring of the liquid steel flow. A number of beneficial effects are attributed to electromagnetic stirring in the mould region (M-EMS), e.g. the enhanced transition from columnar to equiaxed solidification, the homogenization of the liquid steel flow or the reduction of surface and subsurface defects. Although the positive effects of M-EMS can be seen on the blooms (e.g. in etchings), the link between electromagnetic stirring of the steel melt and the quality of the solidified bloom is not sufficiently understood. Theoretical considerations are often limited to general cases and their results are therefore not directly applicable to real continuous casting geometries. On the other hand, plant measurements can only be performed to a limited extent due to the harsh conditions and other restrictions (e.g. safety regulations). In this work an alternative approach is used to investigate the steel flow in a round bloom caster under the influence of M-EMS. In a 1:3 scale Perspex model of a round bloom strand, measurements of the flow under the influence of a rotating magnetic field can be conducted. These measurements provide a validation benchmark for the numeric simulations. A numeric model of the before mentioned 1:3 scale model is implemented, encompassing the strand, the submerged entry nozzle as well as the M-EMS device. In the modelling approach, the bidirectional coupling between liquid steel flow and the electromagnetic field/forces has to be considered because otherwise the resulting tangential velocities will be overestimated. With the validated modelling approach, simulations of real casting machines can then be conducted, stirring parameter influences can be shown and conclusions for the real casting process can be drawn.
Keywords: electromagnetic stirring, round bloom caster, numeric simulations, tangential velocities, eutectic alloy GaInSn, flow measurement, ultrasound doppler velocimetry

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Permalink: https://www.hzdr.de/publications/Publ-24560
Publ.-Id: 24560


Hydrometallurgy: It’s role in a Circular Economy

Reuter, M. A.
Metals play a significant role in industrialisation and technological advancements.
The depletion of natural rich ore deposits coupled with a fall in grade, a decline in productivity, rising operational and energy costs, concerns on sustainability and environmental impact of mining and metal related activities have been affecting the mining and metals industry in the recent past. Unless innovative methods that look at the smart use and recovery of metals from metal resources are developed, the world will be faced by a metal supply risk that will impact on future economic growth and technological development.
  • Invited lecture (Conferences)
    Sustainable Hydrometallurgical Extraction of Metals / Hydrometallurgy Conference 2016, 31.07.-03.08.2016, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-24559
Publ.-Id: 24559


Possibilities and limitations of cfd simulation for flashing flow scenarios in nuclear applications

Liao, Y.; Lucas, D.
The flashing phenomenon is relevant to nuclear safety analysis for example by loss of coolant accident and safety release scenarios. It has been studied intensively by means of experiments and simulations with system codes, but CFD simulation is still at the embryo stage. Rapid increasing computer speed makes it possible to apply the CFD technology in such complex flow situations. Nevertheless, a thorough evaluation on the limitation and restriction is still missing, which is however indispensable for the further development. In the present work, the commonly used two-fluid model with different mono-disperse assumptions are used to simulate various flashing scenarios. With the help of available experimental data, the results are evaluated and limitations are discussed. A poly-disperse method is found necessary for a reliable prediction of mean bubble size and phase distribution. First attempts to trace the evolution of bubble size distribution by means of poly-disperse simulations are made.
Keywords: Flashing; CFD simulation; Two-Fluid-Model; Mono-disperse; Poly-disperse

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Permalink: https://www.hzdr.de/publications/Publ-24558
Publ.-Id: 24558


Distinguishing magmatic and metamorphic processes in peralkaline rocks of the Norra Kärr complex (Southern Sweden) using textural and compositional variations of clinopyroxene and eudialyte-group minerals.

Atanasova, P.; Marks, M. A. W.; Kraise, J.; Gutzmer, J.; Markl, G.; Heinig, T.
The 1.49 Ga old Norra Kärr complex in Southern Sweden contains rocks characterized by a very high ratio of (Na+K)/Al ≥ 1.2 and a complex and highly unusual mineralogy, including rock-forming catapleiite, eudialyte-group minerals as well as minor rinkite- and britholite-group minerals. In contrast to other well-studied examples of agpaitic rocks, the Norra Kärr rocks have been deformed and partially metamorphosed during the Sveconorvegian/Grenvillian orogeny, and are now preserved in a westward dipping synform.
Magmatic and metamorphic processes at the Norra Kärr complex are distinguished by combining rock fabrics of clinopyroxene and eudialyte-group minerals. Both mineral groups are stable over a large P-T range, which makes them excellent monitors of the geochemical evolution of such systems and enables the reconstruction of magmatic and subsequent metamorphic conditions.
The magmatic mineral assemblage crystallized from a subsolvus syenite at continuously decreasing temperatures (700 - 450ºC) and silica activity (0.6 - 0.3). Due to initially relatively low peralkalinity and reducing conditions, Zr was first incorporated in Zr-aegirine. Subsequent destabilization of the latter indicates increasing peralkalinity, oxygen fugacity and water activity, which resulted in the crystallization of early magmatic catapleiite. Crystallization of presumably later magmatic Mn- and REE-poor eudialyte-group minerals, happened as soon as sufficient Cl, REE and HFSE were enriched in the residual melt.
Metamorphic conditions during the Sveconorvegian/Grenvillian orogeny are constrained to T between 400 - 550ºC and aSiO2 range of 0.25 - 0.4. Due to deformation and interaction with fluids, post-magmatic Al-rich aegirine as well as post-magmatic eudialyte-group minerals enriched in REE, Y and Mn formed. Subsequently, the eudialyte-group minerals were destabilized and decomposed to post-magmatic catapleiite and secondary REE-bearing minerals. During the whole history of the complex, aSiO2 remains very similar, indicating very little interaction with the surrounding granitic rocks.
Regardless of the intense deformation due to folding of the Norra Kärr body during the Sveconorvegian/Grenvillian orogeny, indications for primary magmatic layering of the intrusion are retained on the deposit scale. In addition, the compositional changes of magmatic eudialyte-group minerals from the outer to the inner subunit indicate a primary geochemical evolution feature due to fractional crystallization.
Keywords: deformed nepheline syenite; rare earth elements; clinopyroxene, eudialyte-group minerals

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Permalink: https://www.hzdr.de/publications/Publ-24557
Publ.-Id: 24557


Deutschland auf dem Weg in die Kreislaufwirtschaft?

Reuter, M. A.
In Anbetracht des Wachstums der Weltbevölkerung, des wirtschaftlichen Aufholens der Schwellen- und Entwicklungsländer sowie der fehlenden Entkopplung des Wachstums vom Ressourcenverbrauch in den Industrieländern kommt der Kreislaufwirtschaft eine entscheidende Rolle zu: Sie ist mehr als nur die konsequente und umfassende Erfassung und Wiederverwertung aller Wertstoffe. Kreislaufwirtschaft beginnt bereits beim intelligenten Design von Produkten und Werkstoffen, das es ermöglicht, ein Produkt am Ende seines Lebenszyklus möglichst vollständig zu verwerten und die in ihm enthaltenen Rohstoffe zurückzugewinnen. Insbesondere für Deutschland als hochindustrialisiertes Land liegen hier enorme ökonomische Potentiale. Die Ressourcenproduktivität stellt auch zukünftig ein wichtiges Element der Wettbewerbsfähigkeit deutscher Firmen und der Sicherung von Beschäftigung dar. Je nach Perspektive ergibt sich ein differenziertes Bild über die deutschen Fortschritte in diesem Bereich. Mit Blick auf die abfallwirtschaftliche Seite der Kreislaufwirtschaft gehört Deutschland in Bezug auf Recyclingquoten zu den absoluten Vorreitern. Ein deutlich anderes Bild ergibt sich jedoch, wenn man den Blick weitet und die tatsächliche Kreislaufführung von Abfällen betrachtet: Zwei Drittel aller Abfälle werden noch nicht als Ressource genutzt. Auch im Bereich der inneren Kreisläufe besteht in Deutschland noch Nachholbedarf, im Fokus stehen hier Aktivitäten wie die Reparatur und Verlängerung der Nutzungsdauer von Produkten.
Eine neue Studie der Friedrich-Ebert-Stiftung hat den Stand der Kreislaufwirtschaft in Deutschland untersucht, bislang noch ungenutzte Potentiale identifiziert und Handlungsempfehlungen gemacht, wie die Ressourcenproduktivität verbessert werden kann.
  • Invited lecture (Conferences)
    Deutschland auf dem Weg in die Kreislaufwirtschaft?, 10.06.2016, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24556
Publ.-Id: 24556


Metamorphic control on REE redistribution in alkaline complexes – the Norra Kärr example

Atanasova, P.; Marks, M. A. W.; Krause, J.; Gutzmer, J.; Markl, G.
During the last decade the economic interest on rare earth elements (REE) rapidly increased due to their broad application in high-tech products. Beside carbonatites and lateritic deposits, alkaline and peralkaline rocks comprise one of the most promising sources for future REE supply, in particular heavy REE (HREE). As a reaction of global demand, a large amount of relatively unknown and/or difficult to access occurrences have been intensely explored and large geological data sets have been generated providing detailed insight into hidden/unknown geologic formations.
The Norra Kärr alkaline complex in Southern Sweden is a very good example of this development. It represents one of the largest resources of (REE) in Europe. The Norra Kärr rocks are characterized by a very high ratio of (Na+K)/Al ≥ 1.2 and a complex and highly unusual mineralogy, including rock-forming catapleiite, eudialyte group minerals (EGM) as well as minor rinkite and britholite group minerals. EGM incorporate significant concentrations of more than 30 different elements, including the group of 14 naturally occurring lanthanides, Y and Zr. Catapleiite hosts large amounts of Zr, but is essentially REE-free. The Norra Kärr body intruded at around 1.49 ± 0.01 Ga [2]. In contrast to other well-studied examples of so-called agpaitic rocks, such as the Ilímaussaq complex (Greenland) or the Lovozero Complex (Kola peninsula/Russia), it has been deformed during the Sveconorvegian/Grenvillian orogeny and is preserved within a westwards dipping synform. This specific feature has now been used to amplify the restricted knowledge on the behavior of agpaitic rocks during metamorphism. Earlier work on deformed agpaitic rocks in Canada and Malawi (e.g. [1] & [3]) mainly used compositional changes of clinopyroxene (CPX) to trace magmatic and metamorphic processes in agpaitic rocks. Our study investigates additionally textural and compositional features of the main ore-forming minerals (EGM) to provide direct insight into ore formation and subsequent REE (re-)distribution due to metamorphism.
Magmatic and metamorphic processes in the Norra Kärr complex are distinguished based on rock textures and textural and compositional changes of CPX and EGM. CPX is invariably sodic, but is characterized by early magmatic Zr-rich cores, overgrown by presumably late magmatic Zr-poor aegirine. Both are anhedrally overgrown by Al-rich aegirine (jadeite) of metamorphic origin. EGM show complex distribution patterns of major and minor elements suggesting multiphase influence of fractional crystallization, recrystallization, fluid-induced re-mobilization and late-stage alteration. Oscillatory and sector zoned as well as porous areas of EGM are enriched in Zr, but depleted in Si, Ca, REE, Y, and Cl and are interpreted to be of magmatic origin. In contrast, presumably metamorphosed areas are characterized by either Ce-rich flamy textures or Y-rich, but Ce-depleted poikilitic textures, cracks, veins and/or vugs, and rim areas of single crystals. Furthermore, we observe a general increase of REE, Y, Nb and/or Mn content with increasing degree of deformation.
  • Lecture (Conference)
    35th International Geological Congress, 27.08.-04.09.2016, Cape Town, Republic of South Africa
  • Poster
    Gordon Research Conference on Geochemistry of Mineral Deposits, 19.-24.06.2016, Les Diablerets, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-24555
Publ.-Id: 24555


Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions

Kraus, D.; Vorberger, J.; Pak, A.; Hartley, N. J.; Fletcher, L. B.; Frydrych, S.; Galtier, E.; Gamboa, E. J.; Gericke, D. O.; Glenzer, S. H.; Granados, E.; Macdonald, M. J.; Mackinnon, A. J.; Mcbride, E. E.; Nam, I.; Neumayer, P.; Roth, M.; Saunders, A. M.; Sun, P.; van Driel, T.; Döppner, T.; Falcone, R. W.
The effects of hydrocarbon dissociation and subsequent diamond precipitation on the internal structure and evolution of icy giant planets like Neptune and Uranus have been discussed for more than three decades. Inside these celestial bodies, gravity compresses mixtures of light elements to densities of several grams per cubic centimeter while the temperature reaches thousands of Kelvins resulting in thermal energies on the order of chemical bonding and above.
Under these conditions, simple hydrocarbons like methane, which are highly abundant in the atmospheres of these planets, are believed to undergo structural transitions that release molecular hydrogen from deeper layers and may lead to compact stratified cores. Indeed, the isentropes of Uranus and Neptune intersect temperature-pressure conditions where first polymerization occurs, and then, in deeper layers, a phase separation into diamond and hydrogen may be possible.
Here we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene samples dynamically compressed to 150GPa and 5000 K, which resembles the environment ~10,000 km below the surfaces of Neptune and Uranus. Our findings demonstrate the necessity of high pressures for initiating carbon-hydrogen demixing and imply that diamond precipitation may require ~10x higher pressures than previously suggested by experiments investigating non-isolated hydrocarbons. Besides underlining the general importance of chemical processes inside giant planets, these results will inform evolutionary models of Uranus and Neptune, where carbon-hydrogen demixing can be a significant source for the convection necessary to explain their unusual magnetic fields.
Additionally, our experiment demonstrates an alternative path for producing nanodiamonds for scientific and industrial applications that may be superior to current methods using oxygen-deficient explosives.
Keywords: x-ray scattering, x-ray free electron laser, shock compression, warm dense matter, mixtures, phase separation, demixing, planets, neptune, uranus, carbon, hydrogen, diamond, nano-diamond

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Permalink: https://www.hzdr.de/publications/Publ-24554
Publ.-Id: 24554


Organische Chemie I, Struktur, Nomenklatur und Analyse

Mamat, C.
Liebe Studierende,
mit diesem und den folgenden Studienheften tauchen Sie in die wundervolle Welt der organischen Chemie ein. Wir werden uns sehr intensiv damit beschäftigen, was organische Chemie überhaupt ist. Sie werden am Anfang die wichtigsten Stoffklassen kennen lernen und wie organische Verbindungen generell bezeichnet werden. Wir werden uns Grundreaktionen anschauen, mit denen Sie über 90% der organischen Chemie beschreiben können. Am Ende werden wir an die klassischen Grenzen der organischen Chemie gelangen und sehen, wie sie korrespondiert und überlappt beispielsweise mit der anorganischen Chemie, der physikalischen Chemie, der analytischen Chemie oder auch der Biochemie.
  • Book (Authorship)
    Heidelberg: Springer Verlag, 2016
    0036 Seiten

Permalink: https://www.hzdr.de/publications/Publ-24553
Publ.-Id: 24553


Ultrafast dynamics in VO2 under high pressures

Braun, J. M.; Schneider, H.; Helm, M.; Boatner, L. A.ORC; Marvel, R. E.; Haglund, R. F.; Pashkin, A.
Vanadium dioxide (VO2) is a classic example of a strongly correlated system demonstrating a sharp insulator-to-metal transition (IMT) at Tc = 340 K. Since the IMT occurs just above room temperature, VO2 has a high potential for applications in optoelectronic and electrical devices. Nevertheless, the microscopic mechanism of the IMT in VO2 is not yet fully understood. In particular, the roles played by the electronic correlation and the lattice distortion during the IMT are still under debate.
A pressure-induced metallization of VO2 above 10 GPa has been reported by Arcangeletti et al. using infrared spectroscopy [1]. Remarkably, high-pressure Raman spectra do not reveal qualitative changes indicating that the pressure-driven IMT in VO2 is not coupled to any structural distortion. Recently, the first time-resolved pump-probe study of VO2 under pressure has, indeed, revealed a nonequilibrium metallic phase with the monoclinic structure inherent to the insulating phase. [2]
Here, we report a systematic study of ultrafast pump-probe response in VO2 under pressure at different excitation fluences in order to clarify the nature of the pressure-induced changes in this material. The pump-probe measurements with 400 nm pump and 800 nm probe wavelengths were performed on single VO2 crystals mounted inside a diamond anvil cell. CsI has been used as a pressure-transmitting medium in order to ensure contact between the sample and the diamond anvil.
At low pressures of a few GPa, the photoexcited electrons relax on a time scale of about 0.5 ps. With increasing pressure, the relaxation time gradually becomes faster reaching the value of about 0.15 ps beyond 10 GPa. Furthermore, the application of pressure reduces the amount of pump energy which is required to induce a metastable metallic state. However, even close to 12 GPa, the sample demonstrates a dynamics typical of the insulating VO2. These preliminary results agree with recent high-pressure resistivity measurements that show a gradual crossover to the metallic state which is reached only above 30 GPa. [3]
References:
[1] E. Arcangeletti et al., Phys. Rev. Lett. 98, 196406 (2007).
[2] W.-P. Hsieh et al., Appl. Phys. Lett. 104, 021917 (2014).
[3] L. Bai et al., Phys. Rev. B. 91, 104110 (2015).
Keywords: pump-probe spectroscopy, insulator-to-metal transition, high pressure, diamond anvil cell, vanadium dioxide, VO2, pressure-induced metallization
  • Poster
    54th European High Pressure Research Group (EHPRG) International Meeting on High Pressure Science and Technology, 04.-09.09.2016, Bayreuth, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24552
Publ.-Id: 24552


Ultrafast nonlinear response of GaAs under high pressures

Braun, J. M.; Schmidt, J. F.; Seletskiy, D. V.ORC; Schneider, H.; Helm, M.; Pashkin, A.
Applying hydrostatic pressure leads to dramatic changes in the band structure of semiconductors. In particular, it enables a continuous tuning of the bandgap energy. Here we study the nonlinear response of bulk gallium arsenide (GaAs) in the vicinity of its bandgap. The optical pump-probe experiment is performed in a non-collinear reflection geometry at pressures up to 3GPa generated inside a diamond anvil cell. By increasing pressure we observe pronounced slowing down of the relaxation dynamics of photoexcited charge carriers: the time constant of the dominating relaxation process increases from about 10 ps at ambient pressure to 35 ps above 0.7GPa. These time scales are by an order of magnitude shorter than the recombination time determined using optical pump - THz probe spectroscopy. Thus, the fast dynamics observed in the optical pump-probe measurements is governed by the cooling of hot electron distribution and not by the recombination process. Furthermore, at pressures above 2GPa the bandgap energy of GaAs is above the excitation spectrum of our experiment. The sample becomes transparent for the femtosecond pulses leading to a transient pump-probe signal with a negative sign due to the third order nonlinear response of GaAs.
Keywords: pump-probe spectroscopy, recombination dynamics, high pressure, diamond anvil cell, gallium arsenide, GaAs
  • Lecture (Conference)
    DPG-Frühjahrstagung 2016, 06.-11.03.2016, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24551
Publ.-Id: 24551


Interaction of hydrogen with Fe60Al40 thin films

Ehrler, J.; Bali, R.; Grenzer, J.; Böttger, R.; Potzger, K.
The effects of ion implantation on the structural and magnetic properties of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated by means of X-ray diffraction and Vibrating sample magnetometry. The studies show that the magnetic properties of the 250 nm thick Fe60Al40 films depend on the structural order only. The chemical disorder induced evolution of ferromagnetism comes along with an abrupt disappearance of the (100)-superlattice peak.
The irradiation of paramagnetic B2 Fe60Al40 with H+, He+ or Ne+ ions with different fluences at low temperatures led to an increase of saturation magnetization (MS) going along with a lattice expansion induced by structural disorder. This effect did not appear for proton irradiation at elevated temperatures (250 ∘C) where the ordered B2 phase was retained. Upon low temperature hydrogen implantation of disordered A2 Fe60Al40 films, on the other hand, unlike for helium or neon irradiation, the lattice parameter and MS decreased indicating a little ordering. This might offer the possibility of H+ irradiation induced ordering of chemically disordered alloy thin films well below the ordering temperature.
  • Lecture (Conference)
    HZDR PhD Seminar, 17.-19.10.2016, Oberwiesenthal, Germany

Permalink: https://www.hzdr.de/publications/Publ-24550
Publ.-Id: 24550


Interaction of hydrogen with Fe60Al40 thin films

Ehrler, J.; Bali, R.; Grenzer, J.; Böttger, R.; Potzger, K.
The effects of ion implantation on the structural and magnetic properties of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated by means of X-ray diffraction and Vibrating sample magnetometry. The studies show that the magnetic properties of the 250 nm thick Fe60Al40 films depend on the structural order only. The chemical disorder induced evolution of ferromagnetism comes along with an abrupt disappearance of the (100)-superlattice peak.
The irradiation of paramagnetic B2 Fe60Al40 with H+, He+ or Ne+ ions with different fluences at low temperatures led to an increase of saturation magnetization (MS) going along with a lattice expansion induced by structural disorder. This effect did not appear for proton irradiation at elevated temperatures (250 ∘C) where the ordered B2 phase was retained. Upon low temperature hydrogen implantation of disordered A2 Fe60Al40 films, on the other hand, unlike for helium or neon irradiation, the lattice parameter and MS decreased indicating a little ordering. This might offer the possibility of H+ irradiation induced ordering of chemically disordered alloy thin films well below the ordering temperature.
  • Lecture (Conference)
    Seminar der Professur für Werkstofftechnik, 18.-19.11.2016, Altenberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-24549
Publ.-Id: 24549


Interaction between hydrogen and Fe based ally thin films: Influence of defects

Ehrler, J.; Bali, R.; Otalora, C.; Yildirim, O.; Anwand, W.; Trinh, T. T.; Liedke, M. O.; Böttger, R.; Heller, R.; Cornelius, S.; Yuan, Y.; Grenzer, J.; Potzger, K.
The effect of H treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The treatment was realized by H+ irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm−2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation spectroscopy (PAS) indicates an increase of the open volume defect concentration. Superparamagnetic B2-Fe60Al40 films were annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 µb/Fe atom, as well as a shift in the blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations may be mostly due to structural changes.
  • Lecture (Conference)
    Seminar der Professur Werkstofftechnik, 01.-02.04.2016, Krippen, Germany

Permalink: https://www.hzdr.de/publications/Publ-24548
Publ.-Id: 24548


Influence of Hydrogen on Magnetic and Defect Properties of Fe60Al40 thin films

Ehrler, J.; Bali, R.; Anwand, W.; Trinh, T. T.; Liedke, M. O.; Böttger, R.; Yuan, Y.; Grenzer, J.; Potzger, K.
The effect of hydrogen treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The H treatment was realized by proton irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm-2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation spectroscopy (PAS) indicates an increase of the open volume defect concentration.
Superparamagnetic B2-Fe60Al40 films were capped with 10 nm Pd and annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 µb/Fe atom, as well as a shift in the superparamagnetic blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations in magnetic properties may be mostly due to structural changes.
  • Poster
    International Hydrogen Conference, 11.-14.09.2016, Jackson Lake, Wyoming, USA

Permalink: https://www.hzdr.de/publications/Publ-24547
Publ.-Id: 24547


Rapid Data Processing for Ultrafast X-Ray Computed Tomography Using Scalable and Modular CUDA based Pipelines

Frust, T.; Wagner, M.; Stephan, J.; Juckeland, G.; Bieberle, A.
Ultrafast X-ray tomography is an advanced imaging technique for the study of dynamic processes basing on the principles of electron beam scanning. A typical application case for this technique is e.g. the study of multiphase flows, that is, flows of mixtures of substances such as gas-liquid flows in pipelines or chemical reactors. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a number of such tomography scanners are operated. Currently, there are two main points limiting their application in some fields. First, after each CT scan sequence the data of the radiation detector must be downloaded from the scanner to a data processing machine. Second, the current data processing is comparably time-consuming compared to the CT scan sequence interval. To enable online observations or use this technique to control actuators in real-time, a modular and scalable data processing tool has been developed, consisting of user-definable stages working independently together in a so called data processing pipeline, that keeps up with the CT scanner's maximal frame rate of up to 8 kHz. The data processing stages are arbitrarily programmable and combinable. In order to achieve the highest processing performance all relevant data processing steps, which are required for a standard slice image reconstruction, were individually implemented in separate stages using Graphics Processing Units (GPUs) and NVIDIA's CUDA programming language. Data processing performance tests on different high-end GPUs (Tesla K20c, GeForce GTX 1080) and external computer clusters (Tesla P100) showed excellent performance.
Keywords: Computed tomography; Image reconstruction; Multithreading; Parallel algorithms; Pipeline processing; Real-time systems

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Permalink: https://www.hzdr.de/publications/Publ-24546
Publ.-Id: 24546


Hydrogen treatment of Fe60Al40 thin films

Ehrler, J.; Bali, R.; Otalora, C.; Anwand, W.; Trinh, T. T.; Liedke, M. O.; Böttger, R.; Yuan, Y.; Grenzer, J.; Cornelius, S.; Potzger, K.
The effect of hydrogen treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The H treatment was realized by proton irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm-2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation Spectroscopy (PAS) indicates an increase of the open volume defect concentration.
Superparamagnetic B2-Fe60Al40 films were capped with 10 nm Pd and annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 μb/Fe atom, as well as a shift in the superparamagnetic blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations in magnetic properties may be mostly due to structural changes.
  • Poster
    IEEE Magnetics Society Summer School 2016, 10.-16.07.2016, Tohoku University, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-24545
Publ.-Id: 24545


Sloshing instability and electrolyte layer rupture in liquid metal batteries

Weber, N.; Beckstein, P.; Herreman, W.; Horstmann, G. M.; Nore, C.; Stefani, F.; Weier, T.
Liquid metal batteries (LMBs) are discussed today as a cheap grid scale energy storage, as required for the deployment of fluctuating renewable energies. Built as a stable density stratification of two liquid metals separated by a thin molten salt layer, LMBs are susceptible to short-circuit by fluid flows. Using direct numerical simulation, we study a sloshing long wave interface instability in cylindrical cells, which is already known from aluminium reduction cells. After characterising the instability mechanism, we investigate the influence of cell current, layer thickness, density, viscosity, conductivity and magnetic background field. Finally we study the shape of the interface and give a dimensionless parameter for the onset of sloshing as well as for the short-circuit.

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Permalink: https://www.hzdr.de/publications/Publ-24544
Publ.-Id: 24544


Hydrogen treatment of Fe60Al40 thin films

Ehrler, J.; Bali, R.; Otalora, C.; Yildirim, O.; Anwand, W.; Trinh, T. T.; Liedke, M. O.; Böttger, R.; Heller, R.; Cornelius, S.; Yuan, Y.; Grenzer, J.; Potzger, K.
The effect of H treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The treatment was realized by H+ irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm−2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation spectroscopy (PAS) indicates an increase of the open volume defect concentration. Superparamagnetic B2-Fe60Al40 films were annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 µb/Fe atom, as well as a shift in the blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations may be mostly due to structural changes.
  • Poster
    80. Jahrestagung der DPG und DPG-Frühjahrstagung, 06.-11.03.2016, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-24543
Publ.-Id: 24543


Thermal Rayleigh-Marangoni convection in a three-layer liquid-metal-battery model

Köllner, T.; Boeck, T.; Schumacher, J.
The combined effects of buoyancy-driven Rayleigh-B\'{e}nard convection (RC) and surface tension-driven Marangoni convection (MC) are studied in a triple-layer configuration which serves as a simplified model for a liquid metal battery (LMB). The three-layer model consists of a liquid metal alloy cathode, a molten salt separation layer, and a liquid metal anode at the top. Convection is triggered by the temperature gradient between the hot electrolyte and the colder electrodes, which is a consequence of the release of resistive heat during operation. We present a linear stability analysis of the state of pure thermal conduction in combination with three-dimensional direct numerical simulations of the nonlinear turbulent evolution on the basis of a pseudospectral method. Five different modes of convection are identified in the configuration, which are partly coupled to each other: RC in the upper electrode, RC with internal heating in the molten salt layer, MC at both interfaces between molten salt and electrode as well as anti-convection in the lower electrode. The linear stability analysis confirms that the additional Marangoni effect in the present setup increases the growth rates of the linearly unstable modes, i.e. Marangoni and Rayleigh-B\'{e}nard instability act together in the molten salt layer.
The critical Grashof and Marangoni numbers decrease with increasing middle layer thickness. The calculated thresholds for the onset of convection are found for realistic current densities of laboratory-sized LMBs. The global turbulent heat transfer follows scaling predictions for internally heated RC. The global turbulent momentum transfer is comparable with turbulent convection in the classical Rayleigh-B\'{e}nard case. In summary, our studies show that incorporating Marangoni effects generates smaller flow structures, alters the velocity magnitudes, and enhances the turbulent heat transfer across the triple-layer configuration.
Keywords: Marangoni convection, Free convection, Interfacial flows, Turbulent convection

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Permalink: https://www.hzdr.de/publications/Publ-24542
Publ.-Id: 24542


Evaluating Moisture and Geometry Effects on L-Band SAR Classification Performance over a Tropical Rain Forest Environment

Liesenberg, V.; Souza Filho, C. R.; Gloaguen, R.
Multitemporal single (HH) and dual-polarization (i.e., HH, HV) L-band spaceborne synthetic aperture radar (SAR) scenes were evaluated under different moisture conditions caused by precipitation prior to data acquisition at varying incidence angles. The changes affecting backscattering intensity, polarimetric decomposition, backscattering mechanism, and land use/land cover classification performance were evaluated. The study area is a shifting-cultivation environment in the eastern Amazon (Brazil). Several data input scenarios were proposed in the classification scheme (i.e., backscattering intensity alone and combined with alpha/entropy decomposition parameters, band ratios, and textural parameters) using a random forest classifier framework. Integration with optical data was also examined. The classification accuracy scores were then compared with accumulated precipitation data. The results showed that the variation in both the vegetation moisture and incidence angle increases the backscattering intensity for pasture, riparian forest and young regenerated forest by at least 1 dB compared with old successional forest stages due to its more uniform vertical structure and the landscape's increased dielectric constant. The overall classification accuracy proved low for each SAR acquisition date compared with the performance of the Landsat data. Based on SAR data, misclassification occurs for the young successional forest stages and increases in scenes with higher moisture conditions. The classification performance benefits from data integration only for one SAR scene acquired in the dry season. The results highlight the importance of selecting proper temporal intervals for the different SAR polarization modes of the forthcoming SAR missions. Further investigations should address both multitemporal at a single frequency as well as multifrequency SAR approaches.
Keywords: secondary forest, Advanced land observing satellite (ALOS)-phased-arrayed L-band synthetic aperture radar (PALSAR), eastern Amazon, L-band, polarization modes, random forest
  • IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9(2016)12, 5357-5368
    DOI: 10.1109/JSTARS.2016.2617120

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Permalink: https://www.hzdr.de/publications/Publ-24541
Publ.-Id: 24541


Cenozoic intracontinental deformation and exhumation at the northwestern tip of the India-Asia collision—southwestern Tian Shan, Tajikistan, and Kyrgyzstan

Käßner, A.; Ratschbacher, L.; Jonckheere, R.; Enkelmann, E.; Khan, J.; Sonntag, B.-L.; Gloaguen, R.; Gadoev, M.; Oimahmadov, I.
Along the Ghissar-Alai Range of the southwestern Tian Shan (southwestern Kyrgyzstan, northern Tajikistan), the deformation front of the India-Asia collision—the Pamir-Tibet orogen—is interacting with the intracontinental Tian Shan orogen without the intervening Tarim Craton. Apatite fission track (n = 33, ~3.3–145.6 Ma, 27% <10 Ma) and (U-Th)/He (n = 32, ~1.9–26.1 Ma, 56% <10 Ma) thermochronologic ages suggest approximate isothermal holding (very slow cooling to weak reheating) during relative tectonic quiescence between ~150 and 15 Ma. Accelerated exhumation (~0.2–1.0 km/Myr, median ~0.5 km/Myr) and cooling (11–16°C/Myr) occurred over the last ~10 Myr. Geomorphologic parameters—incision, river steepness, and concavity—confirm the youth of the southwestern Tian Shan's mountain building. High exhumation/cooling rates are correlated with pronounced local relief, produced by Cenozoic faults reactivating inherited (Late Paleozoic) structures. Regions with similarly young exhumation are centered along rims of rigid crustal blocks in the central and eastern Tian Shan. Structurally, the Ghissar-Alai Range is a broad, east trending zone of dextral transpression that includes the northern Tajik Basin (Illiak Fault Zone) and the Pamir Thrust System of the frontal northern Pamir. It is the particular deformation field at the northwestern tip of the India-Asia collision—the interaction of the westward gravitational collapse of the Pamir Plateau into the Tajik Basin with the bulk northward motion of the Pamir—that transformed the southwestern Tian Shan into a dextral transpression belt. The dextral transpression in the southwestern Tian Shan contrasts with sinistral strike-slip shear localized along inherited fault zones, accommodating dominant north-south shortening, in the central and eastern Tian Shan. The deformation field influenced by the Pamir and the associated young exhumation make the Ghissar-Alai Range a unique feature in the Tian Shan orogen.

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Permalink: https://www.hzdr.de/publications/Publ-24540
Publ.-Id: 24540


10Be Surface-Exposure Age Dating of the Last Glacial Maximum in the Northern Pamir (Tajikistan)

Grin, E.; Ehlers, T. A.; Schaller, M.; Sulaymonova, V.; Ratschbacher, L.; Gloaguen, R.
Knowledge of the spatial and temporal variations in Alpine glaciations is essential for reconstructing the regional and global timing of ice ages. This study investigates glacial deposits at the mouth of the Muksu catchment in the northern Pamir using 10Be surface-exposure age dating. We sampled boulders from the furthest downstream recessional moraine (20 samples) and five lateral moraines (41 samples) near the former terminus of the Fedchenko Glacier, the longest (∼72 km) present-day Alpine glacier of the Pamir. After the identification of outliers, the boulder population of the recessional moraine yielded a mean exposure age of 17.5 ± 1.9 ka. The maximum exposure age of the lateral moraines, collected ∼5 km up-valley of the recessional moraine, is 18.2 ± 1.7 ka. The boulder ages reflect glacial deposition during the Last Glacial Maximum (Marine Isotope Stage 2) in the region; they are in accordance with published glacial deposition ages in the western Tian Shan.
Keywords: Moraine; Cosmogenic radionuclides; Exposure-age dating; Last glacial maximum; Pamir; Fedchenko Glacier

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Permalink: https://www.hzdr.de/publications/Publ-24539
Publ.-Id: 24539


Evaluation of a deformable registration algorithm for subsequent lung computed tomography imaging during radiochemotherapy

Stützer, K.; Haase, R.; Lohaus, F.; Barczyk, S.; Exner, F.; Löck, S.; Rühaak, J.; Lassen-Schmidt, B.; Corr, D.; Richter, C.
Purpose:

Rating both a lung segmentation algorithm and a deformable image registration (DIR) algorithm for subsequent lung computed tomography (CT) images by different evaluation techniques. Furthermore, investigating the relative performance and the correlation of the different evaluation techniques to address their potential value in a clinical setting.
Methods:

Two to seven subsequent CT images (69 in total) of 15 lung cancer patients were acquired prior, during, and after radiochemotherapy. Automated lung segmentations were compared to manually adapted contours. DIR between the first and all following CT images was performed with a fast algorithm specialized for lung tissue registration, requiring the lung segmentation as input. DIR results were evaluated based on landmark distances, lung contour metrics, and vector field inconsistencies in different subvolumes defined by eroding the lung contour. Correlations between the results from the three methods were evaluated.
Results:

Automated lung contour segmentation was satisfactory in 18 cases (26%), failed in 6 cases (9%), and required manual correction in 45 cases (66%). Initial and corrected contours had large overlap but showed strong local deviations. Landmark-based DIR evaluation revealed high accuracy compared to CT resolution with an average error of 2.9 mm. Contour metrics of deformed contours were largely satisfactory. The median vector length of inconsistency vector fields was 0.9 mm in the lung volume and slightly smaller for the eroded volumes. There was no clear correlation between the three evaluation approaches.
Conclusions:

Automatic lung segmentation remains challenging but can assist the manual delineation process. Proven by three techniques, the inspected DIR algorithm delivers reliable results for the lung CT data sets acquired at different time points. Clinical application of DIR demands a fast DIR evaluation to identify unacceptable results, for instance, by combining different automated DIR evaluation methods.
Keywords: lung segmentation, deformable lung registration, landmarks, inconsistency vector field

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Permalink: https://www.hzdr.de/publications/Publ-24538
Publ.-Id: 24538


Structural control on drainage network and catchment area geomorphology in the Dead Sea area: an evaluation using remote sensing and geographic information systems in the Wadi Zerka Ma’in catchment area (Jordan)

Odeh, T.; Gloaguen, R.; Mohammada, S. H.; Schirmer, M.
The geology of Jordan is characterized by fault systems with three major trends: (1) NW–SE, the oldest, (2) WNW–ESE, and (3) NNW–SSE, the youngest. The drainage network of the Wadi Zerka Ma’in catchment area, located in the middle of the Dead Sea rift, parallels these structural orientations. A regional transtensive fault, with embedded normal faults, bounds the lower and middle part of the catchment area. The topographic profile of the Zerka Ma’in River exhibits two major knickpoints where it crosses two major embedded normal faults. The second major knickpoint developed as a result of the dramatic lowering of the Lisan Lake water level, a lake that pre-dates the Dead Sea. The decreased water level triggered river incision into the clastic sandstone units of Wadi Zerka Ma’in. We performed a morphotectonic analysis study to investigate how the rock structures control the drainage network and the catchment area geomorphology. According to the transverse topographic symmetry factor (T), the catchment area is highly asymmetric. The major basin asymmetry trend is SE-oriented, parallel to the oldest set of fault systems. The catchment area displays a convex hypsometric curve indicating a very recent stage in the geomorphologic cycle. Our study indicates that the Lisan Lake catchment area shrinkage and structures growth controlled and shaped the Wadi Zerka Ma’in catchment area geomorphology. The combined use of a geographic information system (GIS) and remote sensing was shown to be very efficient in unraveling the evolution of the drainage network and catchment area geomorphology.

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Permalink: https://www.hzdr.de/publications/Publ-24537
Publ.-Id: 24537


Recent progress in pulsed laser deposition of iron based superconductors

Haindl, S.; Molatta, S.; Hiramatsu, H.; Hosono, H.
Pulsed laser deposition (PLD) is the most commonly used deposition technique for Fe-based superconductor thin films today. The number of grown compounds using PLD is still quite limited to so-called 11 compounds (FeTexSy, FeSe1−xTex) and 122 compounds (primarily Co-and P-substituted BaFe2As2). Especially in the growth of Fe-chalcogenides, PLD is challenged by the strong volatility of the elements and their non-negligible vapour pressure. In addition, in situ PLD of the high-temperature superconducting F-doped iron oxypnictides seemed to be feasible only under reactive deposition and stayed disregarded for some time. Here, we summarise the progress that was recently made in the growth of Fe-based superconducting thin films towards an improved control of thin film stoichiometry and the in situ growth of F-doped iron oxypnictides. The presented new ideas deviate from the standard approach of an adjustment of target composition. We first focus on the growth of FeSe1−xTex films, where the introduction of a buffer layer of same composition decreased surface roughness and allowed epitaxial film growth at reduced deposition temperatures with enhanced reproducibility. Second, we illustrate how F-doping in iron oxypnictide thin films can be obtained during in situ PLD using a diffusive reaction between substrate and the growing film.

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Permalink: https://www.hzdr.de/publications/Publ-24536
Publ.-Id: 24536


Reply to the comment of Mitchell et al. on “Geomorpho-tectonic evolution of the Jamaican restraining bend” by L. Domínguez-González, L. Andreani, K.P. Stanek and R. Gloaguen [Geomorphology, 228 (2015) 320–334]

Domínguez-González, L.; Andreani, L.; Stanek, K. P.; Gloaguen, R.
We reply to the comments of Mitchell et al. on our paper entitled “Geomorpho-tectonic evolution of the Jamaican restraining bend”. The comments contain statements about the methods that need to be balanced. We agree that the interpretation of the modeled drainage network in some karstified parts of the Jamaican island is difficult, but this does not affect the validity of our analysis elsewhere. We consider that our geomorphic analyses (which also include topographic profiles and morphometric maps) are still valid. The view expressed by Mitchell et al. that we used serially developed landscapes to ‘date’ progressive uplift is an oversimplification of our discussion. We highlighted the differences between the geomorpho-tectonic provinces of Jamaica, and we proposed to explain these differences by a model which involves (1) a westward propagation of the restraining bend and (2) a difference in tectonic styles between the different provinces of Jamaica. Our interpretation does not contradict existing models based on seismotectonic data, provenance analysis or on the origin of Jamaican bauxite. There is a disagreement between James-Williamson et al. (2014), which suggested that central Jamaica was already being uplifted by the end of the Late Miocene, and Domínguez-González et al. (2015), which proposed a Pliocene to present onset of the NE-trending compression toward the SW. However, the timing of the deformation in central and western Jamaica is still poorly constrained and, at this time, any interpretation of the uplift history of central Jamaica should be considered as hypothetical.
Keywords: Landscape models; GIS; Digital elevation models

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Permalink: https://www.hzdr.de/publications/Publ-24535
Publ.-Id: 24535


Geomorphic analysis of transient landscapes in the Sierra Madre de Chiapas and Maya Mountains (northern Central America): implications for the North American–Caribbean–Cocos plate boundary

Andreani, L.; Gloaguen, R.
We use a geomorphic approach in order to unravel the recent evolution of the diffuse triple junction between the North American, Caribbean, and Cocos plates in northern Central America. We intend to characterize and understand the complex tectonic setting that produced an intricate pattern of landscapes using tectonic geomorphology, as well as available geological and geophysical data. We classify regions with specific relief characteristics and highlight uplifted relict landscapes in northern Central America. We also analyze the drainage network from the Sierra Madre de Chiapas and Maya Mountains in order to extract information about potential vertical displacements.

Our results suggest that most of the landscapes of the Sierra Madre de Chiapas and Maya Mountains are in a transient stage. Topographic profiles and morphometric maps highlight elevated relict surfaces that are characterized by a low-amplitude relief. The river longitudinal profiles display upper reaches witnessing these relict landscapes. Lower reaches adjust to new base-level conditions and are characterized by multiple knickpoints.

These results backed by published GPS and seismotectonic data allow us to refine and extend existing geodynamic models of the triple junction. Relict landscapes are delimited by faults and thus result from a tectonic control. The topography of the Sierra Madre de Chiapas evolved as the result of (1) the inland migration of deformation related to the coupling between the Chiapas Massif and the Cocos forearc sliver and (2) the compression along the northern tip of the Central American volcanic arc. Although most of the shortening between the Cocos forearc sliver and the North American Plate is accommodated within the Sierra de Chiapas and Sierra de Los Cuchumatanes, a small part may be still transmitted to the Maya Mountains and the Belize margin through a "rigid" Petén Basin.

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Permalink: https://www.hzdr.de/publications/Publ-24534
Publ.-Id: 24534


Room-temperature tetragonal non-collinear Heusler antiferromagnet Pt2MnGa

Singh, S.; D'Souza, S. W.; Nayak, J.; Suard, E.; Chapon, L.; Senyshyn, A.; Petricek, V.; Skourski, Y.; Nicklas, M.; Felser, C.; Chadov, S.
Antiferromagnetic spintronics is a rapidly growing field, which actively introduces new principles of magnetic storage. Despite that, most applications have been suggested for collinear antiferromagnets. In this study, we consider an alternative mechanism based on long-range helical order, which allows for direct manipulation of the helicity vector. As the helicity of long-range homogeneous spirals is typically fixed by the Dzyaloshinskii–Moriya interactions, bi-stable spirals (left- and right-handed) are rare. Here, we report a non-collinear room-temperature antiferromagnet in the tetragonal Heusler group. Neutron diffraction reveals a long-period helix propagating along its tetragonal axis. Ab-initio analysis suggests its pure exchange origin and explains its helical character resulting from a large basal plane magnetocrystalline anisotropy. The actual energy barrier between the left- and right-handed spirals is relatively small and might be easily overcome by magnetic pulse, suggesting Pt2MnGa as a potential candidate for non-volatile magnetic memory.

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Permalink: https://www.hzdr.de/publications/Publ-24533
Publ.-Id: 24533


Implementing a Thomson parabola spectrometer for laser driven ions

Brack, F.-E.; Kraft, S.; Kroll, F.; Metzkes, J.; Obst, L.; Schlenvoigt, H.-P.; Zeil, K.; Schramm, U.
Durch die Fokussierung eines ultrakurzen und hochintensiven Laserpulses auf ein Festkörpertarget können Pulse von Protonen und anderen positiv geladenen Ionen erzeugt werden. Auf Basis des etablierten TNSA (target-normal sheath acceleration) Prozesses konnten am Helmholtz-Zentrum Dresden-Rossendorf mit dem 150 TW Ultrakurzpulslaser DRACO Protonenpulse mit Energien bis zu 20 MeV erzeugt und charakterisiert werden. Die Charakterisierung dieser Teilchenstrahlung erfordert die Identifizierung der Ionenspezies und die Bestimmung ihrer spektralen Verteilung möglichst nach jedem Puls, wofür standardmäßig Thomsonspektrometer verwendet werden.
In den letzten Jahren wurde das DRACO-Lasersystem bis zu einer Pulsleistung über 500 TW erweitert. Aufbauend auf dem bisherigen Spektrometerdesign wurde in dieser Arbeit ein kompaktes Spektrometer für einen höheren Energiebereich bis über 150 MeV entworfen und in Betrieb genommen. Zusätzlich wurde für die Identifizierung möglicher das Messergebnis verfälschender Sekundärstrahlungsquellen Monte-Carlo Simulationen durchgeführt.
  • Lecture (others)
    Annual Meeting of the LIGHT collaboration, 26.-27.09.2016, GSI Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24532
Publ.-Id: 24532


Preparation of Animal Irradiation Experiments with Laser-Accelerated Protons and Pulsed High-Field Magnets

Kroll, F.; Beyreuther, E.; Brack, F.; Karsch, L.; Kraft, S.; Pawelke, J.; Schlenvoigt, H.-P.; Schürer, M.; Zeil, K.; Schramm, U.
Particle therapy with energetic proton or heavy ion beams is considered as beneficial for a multitude of radiotherapy patients. The facility and operation costs as well as size and construction demands are considerably higher than for in-room radiotherapy systems based on generation of bremsstrahlung from an electron beam. Laser-acceleration has been considered a potential alternative for conventional accelerators like cyclotrons or synchrotrons and thus could provide a more compact and cost-efficient particle therapy solution in the future. The beam properties of laser accelerated beams strongly differ from the quasi-continuous beams generated by conventional accelerators. Laser accelerated beams exhibit fs to ps bunch length, carry up to 1013 particles with broad energy spectrum and are highly divergent. Furthermore, fluctuations of the said beam parameters on a shot-to-shot basis are inherent to the acceleration mechanism. Thus, special measures are required to make use of the novel particle source, especially considering the goal of a future medical application.

Pulsed high-field magnets, as also facilitated within the LIGHT collaboration, are a versatile and efficient way of shaping laser-accelerated beams both spatially and spectrally for application. Nevertheless, the bunches remain short and therefore intense, leading to high dose rates when stopped in matter. These dose rates make special demands for dosimetry and are a core aspect for radiobiological studies.

We performed experiments with the PW beam of the Draco laser to investigate the feasibility of worldwide first controlled volumetric tumour irradiations with laser-accelerated protons. Therefore, a setup of up to two solenoid magnets was used to efficiently capture and shape the beam, which was then analysed by means of spectrometer, electronic dosimeter and radiochromic film.

The talk will focus on reliable generation of homogeneous dose distributions lateral and in depth. Practical issues, like magnet repetition rate and stability, mean dose rate and future radiobiological challenges will be critically discussed. We will close with an outlook on the volumetric tumour irradiation study with specifically developed tumour model of LN229 cells, grown on the ears of nude mice. The radiobiological endpoint that will be investigated is the radiation induced tumour growth delay.
  • Lecture (others)
    Annual Meeting of the LIGHT collaboration, 26.-27.09.2016, GSI Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24531
Publ.-Id: 24531


Boat based mapping of geological features using 3D-Photogrammetry and hyperspectral imaging system (Case study: Greenland)

Salehi, S.; Jakob, S.; Vest Sørensen, E.
Artic environments provide a challenging ground for geological mapping and mineral exploration. Inaccessibility and harsh conditions complicate ground surveys and a dense cover of ice, vegetation, and lichens hinders supportive remote sensing surveys. Steep coastal cliffs are often the only accessible major outcrops, but are mostly not observable by air- or space-borne remote sensing data due to their off-nadir viewing angle. Former studies of those cliff sections focused on the manual interpretation of ground- or boat-based RGB images. However, detailed spectral and morphological data is missing, which is essential for common semi-automatic remote sensing data processing and interpretation of mineralogy and structures.
This contribution introduces an approach for photogrammetry and hyperspectral remote sensing of near-vertical cliff sections of geological outcrops in central west Greenland. A 3D image-based surface reconstruction technique is developed to enable a more automated outcrop evaluation. The focus lies hereby on the integration of digital photogrammetry with boat-based hyperspectral imaging to complement Digital Outcrop Models (DOM) with quantitative information about mineral variations in the outcrop. The project focuses on: 1) integration of hyperspectral images with the photogrammetry derived DOM´s, 2) geometric distortion correction of boat-based hyperspectral images, 3) extraction and mapping of geological features from close range hyperspectral images. The extreme off-nadir (nearly horizontal) scanning view and the resulting scan geometry need to be taken into account during processing. This contribution also highlights future possibilities for rapid semi-automatic interpretation of the data and advances in technology.
Our approach provides a promising workflow for off-nadir remote sensing campaigns in coastal artic environments including photogrammetry and hyperspectral imagery even in remote regions, which are only accessible by boat and can hardly be observed by classic geological mapping.
Keywords: Hyperspectral Remote Sensing, 3D-Digital Photogrammetry, Spectral Mapping
  • Lecture (Conference)
    GRSG 27th Annual Conference - Future of Geological Remote Sensing: Innovation and Challenges, 07.-09.12.2016, London, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-24530
Publ.-Id: 24530


Direct numerical simulation-based Reynolds-averaged closure for bubble-induced turbulence

Ma, T.; Santarelli, C.; Ziegenhein, T.; Lucas, D.; Fröhlich, J.
Budgets of the turbulent kinetic energy from direct numerical simulations (DNS) of disperse bubbly channel flows are used to develop a new model for bubble-induced turbulence in the Euler-Euler Reynolds-averaged framework.

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Permalink: https://www.hzdr.de/publications/Publ-24529
Publ.-Id: 24529


Processing of Drone-Borne Hyperspectral Data for Geological Applications

Jakob, S.; Zimmermann, R.; Gloaguen, R.
Unmanned Aerial Systems (UAS) are used increasingly to close the gap between space- or airborne and field spectral data. They are able to provide high-resolution hyperspectral images within a short time. However, complex geometric and radiometric corrections are required. These correction steps are crucial, especially when the data should be used in geological applications such as detection of raw materials. Thus, in the following paper we present a new toolbox for processing drone-borne hyperspectral data. Processing steps comprise automatic co-registration, mosaicking and geo- referencing as well as topographic and illumination correction. For the first time we show the applicability of drone-borne hyperspectral data for geological surveys.
Keywords: hyperspectral data, Unmanned Aerial Systems, drone-borne remote sensing, processing toolbox, Acidic Mine Drainage
  • Lecture (Conference)
    8th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 21.-24.08.2016, Los Angeles, United States of America
  • Contribution to proceedings
    8th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 21.-24.08.2016, Los Angeles, United States of America
    DOI: 10.1109/WHISPERS.2016.8071689

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Permalink: https://www.hzdr.de/publications/Publ-24528
Publ.-Id: 24528


Modelling of turbulence modulation in bubbly flows with the aid of DNS data

Ma, T.; Santarelli, C.; Ziegenhein, T.; Lucas, D.; Fröhlich, J.
Budgets of the turbulent kinetic energy from direct numerical simulations of disperse bubbly channel flows are used to develop a new model for bubble-induced turbulence in the Euler-Euler framework. Appropriate scales for the bubble-induced turbulence are determined and the corresponding source terms in the Shear Stress Transport Model are derived from the data. This yields a closure which can be readily used in many existing methods. The model is validated by dedicated Euler-Euler simulations.
  • Poster
    14th Multiphase Flow Conference and Short Course, 08.-10.11.2016, Dresden, Deuschland

Permalink: https://www.hzdr.de/publications/Publ-24527
Publ.-Id: 24527


Turbulence modelling in bubbly flows

Ma, T.
Different turbulence modelling approaches in bubbly flows is introduced.
  • Invited lecture (Conferences)
    The 25th annual meeting of GCPD, 01.-02.10.2016, Aachen, Deuschland

Permalink: https://www.hzdr.de/publications/Publ-24526
Publ.-Id: 24526


The twofold nature of Coulomb scattering in graphene

König-Otto, J. C.; Mittendorff, M.; Winzer, T.; Kadi, F.; Malic, E.; Knorr, A.; Berger, C.; de Heer, W. A.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.
The ultrafast dynamics in graphene, which is of great interest from both a fundamental as well as an application oriented point of view, has been studied intensively during the last years and ascinating effects such as carrier multiplication have been found. Here we focus on the Coulomb scattering dynamics in the energetic vicinity of the Dirac point. Utilizing an optical anisotropy, we reveal the twofold nature of Coulomb scattering in graphene by polarization resolved pump-probe experiments. Coulomb scattering is the main mechanism that transforms an optical excited non-equilibrium carrier distribution into a thermalized one and dominates the initial carrier dynamics. Many publications report extremely fast Coulomb scattering rates and thermalization times in the order of tens of fs often only estimated because of limited time resolution in experiments. This is comprehensible as the linear band structure of graphene allows carriers to scatter along a line easily since this inherently fulfils energy and momentum conservation. However, in case of excitation with linearly polarized light, the initial carrier distribution is anisotropic in k space. This means thermalization needs also a redistribution in momentum direction additionally to the equilibration in energy. When scattering with optical phonons is suppressed by photo excitation at low energy, noncollinear Coulomb scattering is limiting the thermalization time to surprisingly long times (several ps) [1]. This contrasting behaviour, namely a fast equilibration in energy but a slow one in momentum space, is what we refer to as the twofold nature of Coulomb scattering in graphene.

[1] J. C. König-Otto, M. Mittendorff, T. Winzer, F. Kadi, E. Malic, A. Knorr, C. Berger, W. A. de Heer, A. Pashkin, H. Schneider, M. Helm, and S. Winnerl, Phys. Rev. Lett. 117, 087401 (2016).
Keywords: graphene, ultrafast dynamics, anisotropy, Coulomb scattering
  • Poster
    Workshop on Science of “From Matter to Materials and Life”, 14.-16.12.2016, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24525
Publ.-Id: 24525


Circular Economy Engineering - Metallurgy & its infrastructure are key enablers of a CE - Recycling towards Recycling 4.0

Reuter, M. A.
• Circular Economy - SIMP
– System integrated metal production – SIMP
– Rigorous quantification of Resource Efficiency (RE)
• Digitalization - Recycling 4.0
– Internet-of-Metallurgical-Things
– Link all stakeholders in material cycle
• Circular Economy Engineering - CEE
– Metallurgical infrastructure & deep knowledge key
– Inform society in an understandable manner
  • Invited lecture (Conferences)
    Steel in Circular Economy / 3rd European Scientific Steel Panel, 29.04.2016, Düsseldorf, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24524
Publ.-Id: 24524


Four-Wave Mixing in Landau-Quantized Graphene

König-Otto, J. C.; Wang, Y.; Belyanin, A.; Berger, C.; de Heer, W. A.; Orlita, M.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.
For Landau-quantized graphene, featuring an energy spectrum consisting of a series of nonequidistant Landau levels, theory predicts a giant resonantly-enhanced optical nonlinearity. We verify the nonlinearity in a time-integrated degenerate four-wave mixing (FWM) experiment in the mid-infrared spectral range, involving the Landau LL_{-1}, LL_{0} and LL_{1}. A rapid dephasing of the optically induced microscopic polarization on a timescale shorter than the pulse duration (~4 ps) is observed, while a complementary pump-probe experiment under the same experimental conditions reveals a much longer lifetime of the induced population. The FWM signal shows the expected field dependence with respect to lowest order perturbation theory for low fields. Saturation sets in for fields above ~6 kV/cm. Furthermore, the resonant behavior and the order of magnitude of the third-order susceptibility are in agreement with our theoretical calculations.
Keywords: Graphene, Landau-quantized graphene, THz, Spectroscopy, Dynamics, nonlinear Dynamics

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Permalink: https://www.hzdr.de/publications/Publ-24523
Publ.-Id: 24523


Electronic transport in helium-ion-beam etched encapsulated graphene nanoribbons

Nanda, G.; Hlawacek, G.ORC; Goswami, S.; Watanabe, K.; Taniguchi, T.; Alkemade, P. F. A.
We report the etching and electronic transport in nanoribbons of graphene sandwiched between atomically flat hexagonal boron nitride (h-BN). The etching of ribbons of varying width was achieved with a focused beam of 30 keV He+ ions. Using in-situ electrical measurements, we established a critical dose of 7000 ions nm−2 for creating a 10 nm wide insulating barrier between a nanoribbon and the rest of the encapsulated graphene. Subsequently, we measured the transport properties of the ion-beam etched graphene nanoribbons. Conductance measurements at 4 K show an energy gap, that increases with decreasing ribbon width. The narrowest ribbons show a weak dependence of the conductance on the Fermi energy. Furthermore, we observed power-law scaling in the measured current-voltage (I-V) curves, indicating that the conductance in the helium-ion-beam etched encapsulated graphene nanoribbons is governed by Coulomb blockade.
Keywords: Helium Ion Microsope, Graphene, h-BN, Bandgap, Graphene Nanoribbons, Electronic Transport
  • Open Access Logo Carbon 119(2017), 419-425
    DOI: 10.1016/j.carbon.2017.04.062
  • Invited lecture (Conferences)
    User Meeting Kleindiek, 25.-26.04.2017, Reutlingen, Deutschland
  • Lecture (Conference)
    FOR3NANO, 25.-30.06.2017, Helsinki, Finland

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Permalink: https://www.hzdr.de/publications/Publ-24522
Publ.-Id: 24522


Evaluation of GENTOP concept for the buoyancy-driven motion of a single bubble

Schlegel, F.; Gauß, F.; Krepper, E.; Lucas, D.
Different approaches for numerical simulations of multiphase flows have been developed, e.g., Volume-of-Fluid methods (VoF) for free surface flows and Euler-Euler (EE) methods for disperse flows. Nevertheless, most industrial applications involve interfacial structures, which have different morphologies. Therefore, hybrid approaches combining resolved interfaces between the gaseous and liquid phases with EE methods would be desirable. A recent development with promising results is the GENTOP concept (Hänsch et al., 2012), which is based on the multi-fluid concept and statistically resolved interfaces that are formed by a separate liquid and gas phase. The present contribution investigates the differences between VoF methods and the GENTOP framework using the example of a buoyancy-driven motion of a single bubble. Different CFD solvers are compared as well as different density ratios, Eötvös numbers, Morton numbers and grid resolutions. Finally, all results are checked against experiments and data obtained by more advanced methods, e.g., level-set methods. For instance is known from one-fluid approaches (e.g. VoF) that at least 20 – 30 cells per bubble diameter are required to reflect the bubble motion sufficiently. Despite a much coarser grid resolution, GENTOP shows a good agreement with experimental results.
  • Lecture (Conference)
    ICMF 2016 International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien

Permalink: https://www.hzdr.de/publications/Publ-24521
Publ.-Id: 24521


Programmability of Co-antidot lattices of optimized geometry

Schneider, T.; Langer, M.; Alekhina, J.; Kowalska, E.; Oelschlägel, A.; Semisalova, A.; Neudert, A.; Lenz, K.; Potzger, K.; Kostylev, M. P.; Fassbender, J.ORC; Adeyeye, A. O.; Lindner, J.; Bali, R.
Programmability of stable magnetization configurations in a magnetic device is a highly desirable feature for a variety of applications, such as in magneto-transport and spin-wave logic. Periodic systems such as antidot lattices may exhibit programmability; however, to achieve multiple stable magnetization configurations the lattice geometry must be optimized. We consider the magnetization states in Co-antidot lattices of ≈ 50 nm thickness and ≈ 150 nm inter-antidot distance. Micromagnetic simulations were applied to investigate the magnetization states around individual antidots during the reversal process. The reversal processes predicted by micromagnetics were confirmed by experimental observations. Magnetization reversal in these antidots occurs via field driven transition between 3 elementary magnetization states – termed G, C and Q. These magnetization states can be described by vectors, and the reversal process proceeds via step-wise linear operations on these vector states. Rules governing the co-existence of the three magnetization states were empirically observed. It is shown that in an n × n antidot lattice, a variety of field switchable combinations of G, C and Q can occur, indicating programmability of the antidot lattices.
Keywords: Magnetic devices, Periodic systems, Antidot lattices, Magnetization reversal

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Permalink: https://www.hzdr.de/publications/Publ-24519
Publ.-Id: 24519


Laser-driven formation of transient local ferromagnetism in FeRh thin films

Ünal, A. A.; Parabas, A.; Arora, A.; Ehrler, J.; Barton, C.; Valencia, S.; Bali, R.; Thomson, T.; Yildiz, F.; Kronast, F.
The magnetic phase transition from antiferromagnetic to ferromagnetic order in FeRh can be induced globally by heating the material above its phase transition temperature, applying mechanical strain or magnetic fields. To induce this phase transition locally requires a confined source of energy such as a focused laser beam. Here we combine optical excitation with X-ray magnetic imaging to determine the effect of laser heating on the magnetization of FeRh using time-resolved photoelectron emission microscopy. Excitation by a 100 fs laser pulse generates a ferromagnetic state within 0.6 ns which recovers its initial antiferromagnetic state within a further 2 ns. The form of magnetic domains during the growth and disappearance of magnetization suggests an intrinsic speed limit for magnetic and structural changes.

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Permalink: https://www.hzdr.de/publications/Publ-24518
Publ.-Id: 24518


Positive magnetic patterning using ion beams – principles and device applications

Bali, R.; Hlawacek, G.; Liersch, V.; Röder, F.; Wintz, S.; Semisalova, A.; Fassbender, J.ORC
Magnetic data-storage, spintronic and magnonic devices have driven the need for producing well-defined nanoscale magnets of complex geometries. We show how ion-beams can be used to generate nanomagnets in thin films of certain alloys such as B2 ordered Fe60Al40 and Fe50Rh50.[1,2] In these materials a large increase of the saturation magnetization is achieved by inducing subtle atomic displacements caused by collision cascades of penetrating light ions. The ions knock atoms from their ordered sites, generating antisite defects and causing an increase of the Fe-Fe nearest-neighbour interactions which are linked to the increasing magnetization. For instance, a weak magnetization of 0.04 μB per Fe-atom in B2-Fe60Al40 can be increased to 1.67 μB per Fe-atom by the irradiation of light noble gas ions such as He+ or Ne+.
The above ion-induced increase of magnetization can be manifested at the local scale and is termed positive magnetic patterning. Patterning can be performed either by irradiation through lithographed masks,[1] or by a direct writing process using the highly focused ion-beam of a Gas Field Ion-Source.[3] Lateral magneto-resistive devices and magnetic arrays produced by ion-irradiation will be described. The application of ion-assisted magnetic writing opens vast opportunities not only in the field of nanomagnetism and devices, but also in the study of disorder-induced magnetic phase transitions at the nanoscale.
[1] R. Bali et al., Nano Letters (2014) 14 435.
[2] A. Heidarian et al., Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms (2015) 358 251.
[3] F. Röder et al., Scientific Reports (2015) 5 16786.
  • Lecture (Conference)
    20th International Conference on Ion Beam Modification Of Materials, 30.10.-04.11.2016, Wellington, New Zealand
  • Invited lecture (Conferences)
    603. WE-Heraeus-Seminar: Magnonics – Spin Waves Connecting Charges, Spins and Photons, 06.-08.01.2016, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-24517
Publ.-Id: 24517


Digitalizing the Circular Economy-System-Integrated-Material-Production

Reuter, M. A.
Metals have always been a pillar of society. Presently more so than ever, as they are key to enabling our sustainability aspirations. The complex Web of Metals (WoM) is the crucial basis for enabling a sustainable Circular Economy (CE) society. Digitalization and quantification of the WoM (or Internet-of-Metallurgical-Things (IoMT)) are keys to driving CE innovation. Examples of specialized technology and flow sheet needs are presented with consideration given to a “whole of chain” or Systems-Integrated-Metal-Production (SIMP) approach. Examples enabling SIMP include: system, metallurgical process and reactor simulation (e.g. CFD, thermodynamics, flowsheeting, LCA), big data analysis (AI, black box techniques), process control, Design for Recycling/Sustainability, etc. Also outlined are the challenges facing legislators who need to consider the balance between providing our societal sustainability needs with key baseline technology infrastructure requirements for economically viable valuable metals extraction from resources flowing within society. Digitalization enables the IoMT of a CE.
  • Invited lecture (Conferences)
    Distinguished Lecturer Award, 16.02.2016, Nashville, USA

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Publ.-Id: 24516


Simulation of Boil-off Scenarios in Spent Fuel Pools

Oertel, R.; Hanisch, T.; Krepper, E.; Lucas, D.; Rüdiger, F.
The thermo-hydraulic analysis of Spent Fuel Pool accident scenarios is predominantly carried out using one-dimensional codes, based on simplified assumptions for the flow paths around the storage racks and inside the reactor building. Here, CFD is employed to investigate these convective phenomena in order to study their relevance for the cooling of the individual fuel assemblies. A partial exposure of the fuel assemblies is anticipated.
  • Invited lecture (Conferences)
    Fachtagung der KTG-Fachgruppen, 17.-18.11.2016, Eggenstein-Leopoldshafen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24515
Publ.-Id: 24515


Mountain rivers may need centuries to adjust to earthquake-triggered sediment pulses, Pokhara, Nepal

Stolle, A.; Korup, O.; Schwanghart, W.; Bernhardt, A.; Adhikari, B. R.; Andermann, C.; Wittmann-Oelze, H.; Merchel, S.
Mountain rivers respond to strong earthquakes by not only adjusting to changes in local base level, but also by rapidly aggrading to accommodate excess sediment delivered by co- and post-seismic landslides. A growing number of detailed sediment budgets suggests that it takes rivers several years to decades to recover from such seismic disturbances, depending on how recovery is defined. We test this notion and study how rivers adjusted to catastrophic sedimentation triggered by at least three medieval earthquakes in the central Nepal Himalaya. In the vicinity of Pokhara, the nation’s second largest city, rapid aggradation formed a large fan covering 150 km2 of mountainous terrain over a length of some 70 km. The fan prograded into several tributary valleys, rapidly infilling their lower reaches with several tens of meters of sediment from a major point source tens of kilometers away. A robust radiocarbon chronology of these valley fills provides an ideal framework for gauging average rates of fluvial incision and adjustment. We use high-resolution digital elevation data, geodetic field surveys, aerial photos documenting historic channel changes, and several re-exhumed tree trunks in growth position to define dated geomorphic marker surfaces. We compare various methods of computing the volumes lost from these surfaces to arrive at net sediment yields averaged over decades to centuries. We find that contemporary rates of river incision into the medieval earthquake debris are between 160 and 220 mm yr–1, with corresponding sediment yields of 103 to 105 t km–2 yr–1, several hundred years after the last traceable seismic disturbance. These rates greatly exceed the density-adjusted background rates of catchment-wide denudation inferred from concentrations of cosmogenic 10Be in river sands sampled in different tributaries. The lithological composition of active channel-bed load differs largely from local bedrock and confirms that rivers are still busy with excavating medieval valley fills. Pronounced knickpoints and epigenetic gorges at tributary junctions add to the picture of a drawn-out fluvial response, while the re-exhumed tree trunks indicate that some distal portions of the earthquake-derived sediment wedge have been incised to near their base. Our results challenge the notion that mountain rivers recover within years or even decades following earthquake disturbance. We caution against generalizing the spectrum of fluvial response in this context, as the valley fills around Pokhara document the possibility of a more protracted fluvial response that may have been ongoing for as long as 900 years despite the high and aggressive erosion that characterizes Himalayan rivers. Beyond the scientific community, our results may motivate some rethinking of post-seismic hazard appraisals and infrastructural planning during the rehabilitation phase in earthquake-struck regions.
Keywords: AMS, landslides, earthquake, Nepal, Himalalya
  • Poster
    European Geosciences Union (EGU) General Assembly, 23.-28.04.2017, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-24514
Publ.-Id: 24514


CFD Simulation of Spent Fuel Pool Accidents resulting in partially uncovered Fuel Assemblies

Oertel, R.; Krepper, E.; Lucas, D.
The thermal-hydraulic analysis of Spent Fuel Pool accident scenarios is predominantly carried out using one-dimensional system or severe accident codes. Within these codes, very simplified assumptions are made for the flow paths around the storage racks and inside the reactor building. This work presents CFD simulations which deliver a more detailed insight into these convective phenomena, given the scenario of partially uncovered fuel assemblies. It is shown that the spatial distribution of the fuel assemblies in the pool with respect to their decay heat production plays a subordinate role in the development of the large scale flow paths in the pool atmosphere.
  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology (AMNT 2016), 10.-12.05.2016, Hamburg, Deutschland
  • Invited lecture (Conferences)
    47th Annual Meeting on Nuclear Technology (AMNT 2016), 10.-12.05.2016, Hamburg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24513
Publ.-Id: 24513


Digitalizing the Circular Economy - The role of process metallurgical systems

Reuter, M. A.
Metallurgy is a key enabler of a Circular Economy (CE), its digitalization the metallurgical Internet-of-Things (m-IoT). In short: Metallurgy is at the heart of a CE as metals all have strong intrinsic recycling potentials.Process metallurgy as a key enabler for a CE will help much to deliver its goals. The first principles models of process engineering help quantify the Resource Efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first principles environmental information to empower tax paying consumer society, policy, legislators and environmentalists. It provides the details to detail Capital and Operational Expenditure (CAPEX & OPEX) estimates. Through this path the opportunities and limits of a CE, recycling and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE.The digital integration of metallurgical reactor technology and systems, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops i.e. the metallurgical Internet of Things (m-IoT). It is the linkage of the global carrier metallurgical processing system infrastructure, that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure. This will be illustrated through:

System optimization models for multi-metal metallurgical processing. These map large scale m-IoT systems, which link to Computer Aided Design (CAD) tools of the Original Equipment Manufacturers (OEMs), and then establish a recycling index (RI) through the quantification of RE.
Reactor optimization and industrial system solutions to realize the “CE (within a) Corporation - CEC”; realizing the CE of society.
Real-time measurement of ore and scrap properties in intelligent plant structures, linked to the modelling, simulation and optimization of industrial extractive process metallurgical reactors and plants for both primary and secondary materials processing.
Big-data analysis and process control of industrial metallurgical systems, processes and reactors by the application of among others artificial intelligence (AI) techniques and computer aided engineering (CAE).
Minerals processing and process metallurgical theory, technology, simulation and analytical tools, which are all key enablers of the CE.
Visualizing the results of all the tools used for estimating the RE of the CE system in a form that the consumer and general public can understand.
The smart integration of tools and methods that quantify RE and deliver sustainable solutions, named in this paper Circular Economy Engineering (CEE).
  • Invited lecture (Conferences)
    Fostering a synergistic environment in engineering simulation, 17.-18.10.2016, Parma, Italien

Permalink: https://www.hzdr.de/publications/Publ-24512
Publ.-Id: 24512


A multi-field two-fluid concept for the simulation of two-phase flow regime transitions

Oertel, R.; Schlegel, F.; Ziegenhein, T.; Lucas, D.
Multiphase flows feature a range of regimes, which can roughly be categorized into disperse and segregated flows. The past research in the simulation of multiphase flows mainly focused on establishing methods that are appropriate within a well-defined regime. This work aims at the development of a framework for the simulation of multiphase flows with largely varying interfacial length scales, allowing the simulation of flow regime transitions. The basis forms the Euler-Euler concept, which is widely accepted for the simulation of disperse flows and allows for coarse computational meshes. It is also capable to handle complete phase inversion as in stratified flows. In vertical two-phase pipe flow, small disperse elements may exist alongside larger gas structures. The goal of this work is to formulate a hybrid solution procedure which allows treating the former in terms of a probability density and the latter in an interface-resolving manner. The development of the method is conducted using the open source CFD toolbox OpenFOAM.
  • Lecture (others)
    Vortrag im Rahmen eines Gastaufenthaltes am Paul-Scherrer-Institutes, 02.12.2016, Villigen, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-24511
Publ.-Id: 24511


Developing Rapid and Advanced Visualisation of Magnetic Structures Using 2-D Pixelated STEM Detectors

Nord, M.; Krajnak, M.; Bali, R.; Hlawacek, G.; Liersch, V.; Fassbender, J.ORC; Mcvitie, S.; Paterson, G. W.; Maclaren, I.; Mcgrouther, D.
In Transmission Electron Microscopy (TEM) electron diffraction patterns, imaged from the back focal plane of the objective lens, reveal rich information about the structure of materials. The sharpest patterns are obtained using a parallel (semi-convergence angle < 1 mrad) electron beam which typically illuminate an area with a diameter of 100 nm. In Scanning Transmission Electron Microscopy (STEM) the electron beam is focused to form a fine probe, potentially with sub-Ångström diameter, where image signals are collected by detectors which integrate single intensity values for each scan position from two-dimensional scattering in the back focal plane. A key aspect to obtaining high resolution information is that the performance of scanning and detection should be performed rapidly in order to provide live imaging for the user but to also to mitigate for instabilities and specimen drifts.

Recently, advances in fast direct electron counting systems have enabled the development of 2-D pixelated detectors that can operate at fast acquisition speeds. Applying these to the STEM technique enables imaging of the contents of the back focal plane at high frame rates, i.e. the full diffraction pattern can be acquired for every scan position in a STEM dataset. This yields a 4 dimensional dataset: two spatial probe position dimensions, and two reciprocal detector positions. While this opens up many new and exciting research avenues, there are still many challenges in how to use the 4-D datasets optimally. In this work we focus on solutions for performing live or near-live magnetic imaging using a fast pixelated STEM detector. The experimental work was performed on a probe corrected Jeol ARM200cF equipped with a Medipix3 fast pixelated detector capable of acquiring at 1100 frames per second. To image magnetic induction in the materials the STEM was operated in Lorentz mode[1], which involves turning off the objective lenses so that the sample resides in a near field free environment. A custom aberration corrector mode was utilised to enable probe semi-convergence angles from 0.4-3.0 mrad with corresponding probe diameters from < 1 nm to 6 nm[1]. For magnetic samples, the Lorentz interaction with the beam results in electron wave phase changes and beam deflections proportional to the magnetic induced phase gradients across the sample. Using a pixelated detector the direction and strength of the integrated magnetic induction for the sample can be quantitatively measured by tracking the angular deflection of the bright field disc. This presentation will focus on solutions for live imaging of magnetic structures in FeAl thin films patterned with Ne + ions, shown in Fig. 1. An example of magnetic contrast is shown in (c-h), where the areas within the circle (seen in Fig 1a) are ferromagnetic, while the area outside is paramagnetic. The light and dark magnetic contrast is due to deflection of the electron beam, and the figures show two different methods for extracting this deflection. In (c-f), only a single pixel at the edge of the STEM disk is used from each diffraction pattern, with the different figures having the pixel at different places on the disk (marked by the points in (b)). For (g-h), a more advanced edge detection is performed. Here, cross correlation is used to determine the position of the disk. As seen in Fig. 1(g-h), the edge detection techniques clearly produce increased level of magnetic contrast and better signal to noise, but is much more computationally demanding. Thus for live imaging, the more simple method is more suited.

We will also show how offloading the data processing to central and graphical processing units allows for rapid processing with different methods. This includes the single pixel and edge detection methods explained above, as well as centre of mass methods. Lastly, the output data is transferred into Digital Micrograph using open and standard network components, which enables both control of the detector system and live imaging to be performed on a single machine. The presentation will also touch on file formats chosen for data storage and ways of visualising the 4-D datasets.

[1] S. McVitie, et al, “Aberration corrected Lorentz scanning transmission electron microscopy”, Ultramicroscopy, Volume 152, May 2015, Pages 57-62
  • Lecture (Conference)
    Microscopy & Microanalysis 2016 Meeting, 24.-28.07.2016, Columbus, Ohio, USA
  • Open Access Logo Microscopy and Microanalysis 22(2016)S3, 530-531
    DOI: 10.1017/S1431927616003500

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Permalink: https://www.hzdr.de/publications/Publ-24510
Publ.-Id: 24510


Evolution of the local environment and magnetism in Fe60Al40 films under Ne+ irradiation

Smekhova, A.; La Torre, E.; Eggert, B.; Cöster, B.; Szyjka, T.; Walecki, D.; Salamon, S.; Ollefs, K.; Bali, R.; Lindner, J.; Rogalev, A.; Weschke, E.; Banerjee, R.; Sanyal, B.; Schmitz-Antoniak, C.; Wende, H.
X-ray absorption spectroscopy has been applied to study the consequential changes of the local environment around Fe and its magnetic moments in Fe60Al40 thin films of 40 nm thickness along the order-disorder (B2 → A2) phase transition initiated by 20 keV Ne+ ion-irradiation with fluences of (0.75-6)×1014 ions*cm−2. The analysis of EXAFS spectra measured at the Fe K-edge at room temperature revealed an increased number of Fe-Fe nearest-neighbors from 3.47(7) to 5.0(1) and ∼ 1% of volume expansion through the transition. The visualization of the Fe and Al nearest-neighbours rearrangement in the first coordination shell of Fe absorbers was done by wavelet transformations. The observed structural changes will we related to the magnetic properties of the studied samples. The results of self-consistent DFT calculations using VASP and SPR-KKR program packages on relaxed Fe60Al40 structures are consistent with the experimental findings for the ordered (B2) and the disordered (A2) phases.
  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany
  • Lecture (Conference)
    DPG-Tagungen 2018, 12.-16.03.2018, Berlin, Deutschland
  • Lecture (Conference)
    9th Joint European Magnetic Symposia (JEMS) Conference 2018, 03.-07.09.2018, Mainz, Deutschland
  • Contribution to proceedings
    2018 IEEE International Magnetic Conference (INTERMAG), 23.-27.04.2018, Singapore, Singapore
    Proceedings of the 2018 IEEE International Magnetic Conference (INTERMAG): IEEE
    DOI: 10.1109/INTMAG.2018.8508108

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Permalink: https://www.hzdr.de/publications/Publ-24509
Publ.-Id: 24509


A generalized multi-field two-fluid concept for the numerical simulation of two-phase flows

Oertel, R.; Schlegel, F.; Ziegenhein, T.; Lucas, D.
Multiphase flows occur in a variety of industrial applications, e.g. in chemical engineering or in nuclear safety research. An important feature of these flows is the formation of different flow patterns depending on the relative flow rates of the phases. These patterns are not explicitly defined by the conduit and have different characteristics. Past research on the simulation of multiphase flows mainly focused on establishing methods that are appropriate within a well-defined flow regime. The present contribution aims at the development of a generalized framework in OpenFOAM for the simulation of industrial scale multiphase flows with largely varying interfacial length scales, which has the capability to reproduce the mechanisms of flow pattern transitions. For the simulation of disperse flows, the two-fluid approach, where each phase is represented by its own phase-averaged velocity field, is widely accepted.
This concept serves as a basis and is extended to allow interface-resolving simulations for large gas structures, while disperse phase elements are still represented in terms of a number density function.

The present contribution focuses on two parts. Firstly, one feature of multiphase flow pattern transitions is the inherent polydispersity of the occurring gas structures. The difference in diameter between the smallest and the largest elements spans over at least one order of magnitude. In general, this aspect is taken into account by population balance modeling. A successful and stable method for this purpose is the method of classes which will be utilized here, following the ideas of the GENTOP-approach of Hänsch et al. (2012). Since lift-force induced separation of bubbles according to their size is considered as an important mechanism for the transition from bubbly to slug flow, particular emphasis is put on employing a class method which also takes different velocity fields for the disperse phase into account.

The second part focuses on the handling of interface-resolving gas structures within the two-fluid model. Beside the aspect of interface sharpening to counteract the numerical diffusion, the momentum exchange between the separate velocity fields is important. In reality, the phases share a single velocity field and a no-slip condition is present at the interface. This condition can also be met in a two-fluid model by forcing the velocity of the two phases to be equal at interface. However, as such a method requires a high grid resolution, we introduce a direction depended model for the momentum exchange at the interface, that accounts separately for pressure and friction induced drag. Finally, the presented framework allows the simulation of multiphase flow problems close to an industrial scale and gives realistic predictions, even on a coarse grid.

Haensch, S.; Lucas, D.; Krepper, E. & Hoehne, T. A multi-field two-fluid concept for transitions between different scales of interfacial structures, International Journal of Multiphase Flow, 2012, 47, 171-182
  • Invited lecture (Conferences)
    4th Annual OpenFOAM User Conference 2016, 11.-13.10.2016, Köln, Deutschland

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Publ.-Id: 24508


An elementspecific investigation of the disorder induced phase transition in Fe60Al40 thin films driven by ion irradiation

Eggert, B.; La Torre, E.; Szyjka, T.; Smekhova, A.; Bali, R.; Ollefs, K.; Salamon, S.; Wilhelm, F.; Bannerjee, R.; Rogalev, A.; Weschke, E.; Lindner, J.; Sanyal, B.; Schmitz-Antoniak, C.; Wende, H.
Chemically ordered Fe60Al40 in the B2 structure presents a paramagnetic ordering, while the chemical disordered phase with the A2 structure exhibits a ferromagnetic state. This phase transition leads to a change of the effective number of nearest Fe neighbors [1] and of the lattice constant [2]. This phase transition can be driven by ion irradiation [3]. In this work we investigate Fe60Al40 thin films before and after 20 keV Ne+ irradiation by means of x-ray magnetic circular dichroism (XMCD) at the Fe L2,3- and K-edge to analyze the microscopic magnetic structure. For a comparison macroscopic magnetometry was used concerning the depth-profile of the induced magnetism [1]. These results are correlated to the modified structural properties.
  • Poster
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-24507
Publ.-Id: 24507


Ein Eckstein der Industrie 4.0

Reuter, M. A.
Seit vielen Jahrhunderten ist Freiberg weltweit führend in den Bereichen Bergbau, Aufbereitung und Metallurgie. Heute spielt die Stadt außerdem eine wichtige, innovative Rolle in der nachhaltigen Rohstoffnutzung. Ein maßgeblicher Schlüssel für eine nachhaltige Nutzung der Rohstoffe wird unter dem Begriff „Industrie 4.0“ zusammengefasst, zu deren Kernbausteinen die Prozessmetallurgie sowie ihre Digitalisierung gehören.

Der Vortrag beschreibt die Rolle Freibergs in der Gestaltung einer nachhaltigen Kreislaufwirtschaft mit dem Ziel, Energie- und Ressourceneffizienz miteinander in Einklang zu bringen.
  • Lecture (Conference)
    19th-krueger-colloquium, 09.06.2016, Freiberg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24506
Publ.-Id: 24506


Ferromagnetism of Fe60Al40 thin films under a magnifying glass of hard X-rays

in Russian
Smekhova, A.; Eggert, B.; Cöster, B.; La Torre, E.; Szyjka, T.; Ollefs, K.; Bali, R.; Potzger, K.; Cornelius, S.; Liedke, M. O.; Lindner, J.; Salamon, S.; Rogalev, A.; Wende, H.
Формирование дальнего ферромагнитного порядка в сплавах FeAl, наведенного химическим разупорядочением кристаллической решетки, интенсивно исследуется в течение более 40 лет [1]. В настоящее время это явление успешно используется для создания магнитных структур на основе тонких пленок Fe60Al40 с контролируемыми магнитными свойствами [2], приготовленных при помощи технологии ионного облучения. Однако до сих пор вопрос о наиболее существенной причине возникновения этого эффекта –локального окружения атомов железа [3] и/или изменений параметров решетки [4] – остается открытым.
В нашей работе методами элементно-селективной спектроскопии поглощения EXAFS и XMCD в жесткой рентгеновской области исследовались тонкие пленки Fe60Al40 (40 нм)/SiO2/Si, приготовленные при помощи магнетронного напыления с последующим отжигом и облучением ионами Ne+ с энергией 20 кэВ как предложено в [2]. Предварительные XRD, MOKE и VSM магнетометрия показали, что облучение ионами разрушает химическое упорядочение в системе при сохранении структурной целостности, и что химически разупорядоченная А2 фаза обладает дальним ферромагнитным порядком, в то время как упорядоченная B2 фаза является парамагнитной.
Анализ EXAFS и XMCD спектров, измеренных на К крае поглощения Fe при комнатной температуре, показал, что увеличение химического беспорядка, обусловленного дозой облучения, ведет к кардинальному изменению ближайшего локального окружения атомов железа с преимущественным расположением атомов Fe в качестве ближайших соседей и к увеличению степени магнитной поляризации 4p состояний железа, определяющей его ор- битальный момент. Вопрос о природе поляризации 4р состояний обсуждается.
Измерения на ESRF были проведены в рамках проекта НС-1811 на линии ID12
1. G. P. Huffman et al., J.Appl. Phys. 38, 735 (1967).
2. R. Bali et al., Nano Lett. 14, 435 (2014).
3. L. Zamora et al., Phys. Rev. B 79, 094418 (2009).
4. J. Nogués et. al., Phys. Rev. B 74, 024407 (2006).
  • Invited lecture (Conferences)
    50th School PNPI condensed matter physics, 14.-19.03.2016, St. Petersberg, Russian Federation

Permalink: https://www.hzdr.de/publications/Publ-24505
Publ.-Id: 24505


Magnetism and structural changes in Fe60Al40 films under Ne+ irradiation

Smekhova, A.; Szyjka, T.; Eggert, B.; Cöster, B.; La Torre, E.; Walecki, D.; Salamon, S.; Ollefs, K.; Bali, R.; Lindner, J.; Rogalev, A.; Weschke, E.; Banerjee, R.; Sanyal, B.; Schmitz-Antoniak, C.; Wende, H.
XANES, EXAFS and XMCD techniques have been applied to probe substantial changes in Fe magnetic moments and the local environment in Fe60Al40 films along the order-disorder phase transition caused by Ne+ irradiation of different fluence and energies. An increased magnetic polarization, drastic changes of coercivity, a rearrangement in the expanded unit cell and structural distortions were observed.
  • Poster
    Eighth Joint BER II and BESSY II User Meeting, 07.-09.12.2016, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-24504
Publ.-Id: 24504


Driving properties of magnetic nanostructures

Mazalski, P.; Kisielewski, J.; Jakubowski, M.; Kurant, Z.; Tahir, N.; Bali, R.; Wojciechowski, T.; Sveklo, I.; Fassbender, J.ORC; Wawro, A.; Spiridis, N.; Maziewski, A.
No abstract available.
  • Poster
    European XFEL Users' Meeting 2016, 27.-29.12.2016, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-24503
Publ.-Id: 24503


Life Cycle Assessment of Metallurgical Processes Based on Physical Flowsheet Models

Scheidema, M.; Reuter, M. A.; Roine, A.
Simulation combined with Life Cycle Assessment (LCA) can be used to quantify the environmental impact of metals production processes. The results for different processing options, as well as the effect of having the same plant at different locations can be evaluated and compared. HSC SIM 8, which is linked with GaBi, or other LCA software can be used to carry out this work. The material flows are calculated using HSC SIM, and they are then converted to environmental indicators. The refining of silver using the High Current Density (HCD) electrorefining process is used as an example in this paper in order to show the link between simulation software and LCA.
Keywords: Process Modeling, Environmental Footprints, LCA, Recycling
  • Book chapter
    Apelian, D., Blanpain, B., Howarter, J., Kvithyld, A., Meskers, C., Mishra, B., Olivetti, E., Spange: REWAS 2016, Schweiz: Springer International Publishing, 2016, 978-3-319-48768-7, 179-185
    DOI: 10.1007/978-3-319-48768-7_26

Permalink: https://www.hzdr.de/publications/Publ-24502
Publ.-Id: 24502


Eco-efficiency indicator framework implemented in the metallurgical industry: part 1 - a comprehensive view and benchmark

Rönnlund, I.; Reuter, M. A.; Horn, S.; Aho, J.; Päällysaho, M.; Ylimäki, L.; Pursula, T.
The purpose of this work was to develop an indicator framework for the environmental sustainability benchmarking of products produced by the metallurgical industry. Sustainability differentiation has become an important issue for companies throughout the value chain. Differentiation is sometimes not attainable, due to the use of average data, lack of comparative data, certain issues being overshadowed by others, and a very narrow palette of indicators dominating the current sustainability assessments. There is a need for detailed and credible analyses, which show the current status and point out where improvements can be made. The indicator framework is developed to give a comprehensive picture of eco-efficiency, to provide methods that enable relevant comparisons as well as the tools for communicating the results. In this way, the methodology presented in this study aims to make differentiation easier and thus aid companies in driving the development toward more sustainable solutions.
Methods

The framework is based on the existing indicator framework Gaia Biorefiner, which is primarily intended for bio-based products. In this work, the framework was further developed for application in the metallurgical industry. The indicator framework is built by first looking at the issues, which are critical to the environment and global challenges seen today and which the activities of the metallurgical industry may have an impact on. Based on these issues, suitable indicators are chosen if they exist and built if they do not. The idea is that all indicators in a group form a whole, showing areas of innovation while refraining from aggregating and weighting, which often compromise a comprehensive and objective view. Both qualitative and quantitative indicators are included. The indicators are constructed following the criteria set by the EU and OECD for building indicators. Each indicator further has a benchmark. The rules for building the benchmark are connected to the indicators. Suitable data sources and criteria for the benchmark and the indicators are gathered from literature, publicly available databases, and commercial LCA software. The use of simulation tools for attaining more reliable data is also studied.
Results and discussion

The result is a visual framework consisting of ten indicator groups with one to five indicators each, totaling up to 31 indicators. These are visualized in a sustainability indicator “flower.” The flower can be further opened up to study each indicator and the reasons behind the results. The sustainability benchmark follows a methodology that is based on utilization of baseline data and sustainability criteria or limits. A simulation approach was included in the methodology to address the problem with data scarcity and data reliability. The status of the environment, current production technologies, location-specific issues, and process-specific issues all affect the result, and the aim of finding relevant comparisons that will support sustainability differentiation is answered by a scalable scoping system.
Conclusions

A new framework and its concise visualization has been built for assessing the eco-efficiency of products from the metallurgical industry, in a way that aims to answer the needs of the industry. Since there is a baseline, against which each indicator can be benchmarked, a sustainability indicator “flower” can be derived, one of the key innovations of this methodology. This approach goes beyond the usual quantification, as it is also scalable and linked to technology and its fundamental parameters. In part 2, a case study “A case study from the copper industry” tests and illustrates the methodology.
Keywords: Benchmarking, Circular economy, Indicator, Metallurgy, Process and system simulation, Product environmental footprint, Resource efficiency, Sustainability

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Permalink: https://www.hzdr.de/publications/Publ-24500
Publ.-Id: 24500


Linking dissipation-induced instabilities with nonmodal growth: The case of helical magnetorotational instability

Mamatsashvili, G.; Stefani, F.
The helical magnetorotational instability is known to work for resistive rotational flows with comparably steep negative or extremely steep positive shear. The corresponding lower and upper Liu limits of the shear are continuously connected when some axial electrical current is allowed to flow through the rotating fluid. Using a local approximation we demonstrate that the magnetohydrodynamic behavior of this dissipation-induced instability is intimately connected with the nonmodal growth and the pseudospectrum of the underlying purely hydrodynamic problem.

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Permalink: https://www.hzdr.de/publications/Publ-24499
Publ.-Id: 24499


Phased Array Ultrasound System for Planar Flow Mapping in Liquid Metals

Mäder, K.; Nauber, R.; Galindo, V.ORC; Beyer, H.; Büttner, L.; Eckert, S.; Czarske, J.
Research in magnetohydrodynamics (MHD) aims at a better understanding of the interaction of conductive fluids and time-varying magnetic fields. Controllable magnetic fields can be used to optimize flows in technical and industrial processes involving liquid metals in order to improve quality and yield. However, necessary experimental studies for the investigations on physical models at room temperature are often limited by the performance of flow instrumentation for opaque liquids. With the phased array ultrasound Doppler velocimeter (PAUDV) we present a modular research platform for flow mapping in liquid metals. It consists of a modular electronics unit capable to interface ultrasound arrays with up to 256 channels. Each channel can be individually configured regarding the excitation pattern (three-level quantization, 64 samples) and the delay (1.6 ns resolution). With the individual addressing of channels the phased array technique to dynamically focus the ultrasound beam can be employed. This allows to resolve smaller flow structures in planar measurements compared to fixed-beam sensors. In addition, it enables the use of receive beamforming and plane wave transmission, which allows to significantly increase the time resolution and to perform 2d flow mapping with only one acoustical access via the cross beam technique. Fast electrical traversing of the measurement volume allows to obtain and visualize turbulence statistics. The capabilities of this research platform are demonstrated on measurements in the alloy gallium-indium-tin at room temperature. 2d velocity measurements of a flow in a cubic vessel influenced by a rotating magnetic field (RMF) are shown and compared to results of a semi-analytical simulation. Furthermore, two-point correlation functions of the velocity field for different magnitudes of the RMF are presented and discussed.
Keywords: Ultrasound Velocimeter, Liquid Metals,. Rotating Magnetic Fields

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Permalink: https://www.hzdr.de/publications/Publ-24498
Publ.-Id: 24498


Scattering-type scanning near-field infrared microscopy at low temperatures

Lang, D.; Döring, J.; Kuschewski, F.; Kehr, S. C.; Eng, L. M.; Winnerl, S.; Schneider, H.; Helm, M.
We present a combination of a versatile low-temperature scattering-type near-field infrared microscope (LT-s-SNIM ) with a tunable infrared free-electron laser (FEL). Our s-SNIM operates over a broad temperature range from 15 - 300 K and is unique in being tunable over a broad frequency range, thanks to the FEL. The over-all LT-s-SNIM functionality down to lowest temperature was tested on both standard gold and structured silicon dioxide samples, revealing net near-field contrasts and no topography cross-talk. Secondly, we investigated several ferroelectric phase transitions in barium titanate single crystals at 273 K and 193 K, allowing to associate clear near-field resonances to every phase and each ferroelectric domain; here, the clear benefit of our LT-s- SNOM pays off, being able to record s-SNOM, PFM, KPFM and topographic data with one and the same tip from every sample surface spot. Thirdly, we used the Jahn-Teller-Transition in the piezoelectric material GVS to quantify the local temperature increase under the AFM tip upon IR irradiation.
Keywords: infrared, spectroscopy, low-temperature, s-SNOM, FEL, near-field, microscopy, phase transition
  • Poster
    Smaller and Faster: Infrared and Terahertz Spectral-Imaging at the Nanoscale with Synchrotron Radiation and Free Electron Laser Sources, 01.-02.12.2016, Trieste, Italia

Permalink: https://www.hzdr.de/publications/Publ-24497
Publ.-Id: 24497


Product-Centric Simulation-based design for recycling: case of LED lamp recycling

Reuter, M. A.; van Schaik, A.
This paper will illustrate how a product-centric simulation approach to recycling is core to Design for Recycling (DfR) & Design for Resource Efficiency. This approach is underpinned by rigorous recycling rate calculations, building on the extensive expertise, knowhow and tools of classical minerals, and metallurgical processing. Process simulation and design tools such as the commercial HSC Sim software are applied to quantify critical DfR rules for a particular product as well as to quantify the recycling rates of all materials and elements in a product. The ten DfR rules we have developed for Waste Electric and Electronic Waste recycling in a study performed for NVMP/Wecycle (the Netherlands) are applied to light emitting diode (LED) lamps. The results produced include recycling and recovery rates, as well as recyclate qualities and quantities, and losses and emissions of materials during recycling for various LED lamp redesigns. Metallurgical processing is also briefly discussed, showing that, in many cases, element recoveries are reduced to zero due to product complexity and ppm levels in the products. Simulation models are linked to life cycle assessment (LCA) and exergy, demonstrating how the applied simulation basis provides the detail to innovate the system. In addition, rigorous environmental assessment is a further outcome of the approach, while at the same time revealing the development that has to occur in LCA databases to improve their value for Ecodesign.
Keywords: Product-centric design for recycling, WEEE system design, Greenprinting, Metallurgy, LED lamp, Ecodesign, Simulation

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Permalink: https://www.hzdr.de/publications/Publ-24495
Publ.-Id: 24495


Simulation-based design for resource efficiency of metal production and recycling systems: Cases - copper production and recycling, e-waste (LED lamps) and nickel pig iron

Reuter, M. A.; Gediga, J.; van Schaik, A.
Purpose
This paper illustrates how a product-centric approach to recycling, building on the extensive expertise, knowhow and tools of the mineral-centric classical minerals and metallurgical processing, should be core to Design for Resource Efficiency (DfRE).

Methods
Process simulation (HSC Sim 1974-2014, Outotec's design tool) and environmental software (GaBi 2014) are applied to quantify resource efficiency (RE) in a rigorous manner. These digitalisation tools are linked and will be used to show how the environmental performance of copper primary production, the processing of residues and the recycling of e-waste, e.g. light emitting diode (LED) lamps as well as the production of nickel pig iron can be evaluated. The paper also shows how technologies can be compared relative to a precise thermodynamic and techno-economic baseline.

Results
The results include simulation-based environmental indicators, exergy, recycling and recovery rates, as well as the qualities and quantities of the recyclates, losses and emissions of materials during production recycling. The complete mass and energy balance simulation provides the mineralogical detail of all streams (both mineral and recyclate as well as offgas and dust) to define and improve environmental assessment, while at the same time revealing the aspects of LCA databases and their results that require improvement. Furthermore, this paper presents an approach for industry to implement life-cycle methods in practice. It shows that the DfRE is all about predicting stream grades and thus is equivalent to Design for Recyclate grade and quality (as this determines whether a recyclate or product stream has economic value and can be treated or processed further). DfRE also reveals especially the grade, composition, minerals etc. of the leakage streams, i.e. diffuse emissions, thus permitting a more precise evaluation of environmental impact.

Conclusions
The prediction of recyclate and stream compositions and grade makes the environmental analysis of systems more precise and will help to expand the detail that defines these flows on environmental databases. This is especially valuable for DfR, where the methodological rigour suggested in this paper is a very necessary addition and requirement for estimating the true environmental impact of product redesigns and the resource efficiency of processing technology and complete recycling systems. The methodology produces mass- and energy-consistent, economically viable best available technique (BAT) process blocks, the inclusion of which on environmental databases will be invaluable in benchmarking technology and systems in terms of estimating the achievable resource efficiency baseline.
Keywords: Copper production and scrap recycling, Design for Resource Efficiency, E-waste and WEEE, Greenprinting, LED lamp recycling, Nickel pig iron (NPI) production, Process metallurgy, Product-centric Design for Recycling (DfR), System design, Ecodesign, LCA

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Permalink: https://www.hzdr.de/publications/Publ-24494
Publ.-Id: 24494


Arbeiten am und für den Grenzbereich

Joehnk, P.
Der experimentelle Nachweis von Hypothesen der Grundlagenphysik ist oftmals nur mit einem gigantischen technologischen Aufwand zu erreichen; CERN in der Schweiz mit seinem Large Hadron Collider ist ein beredtes Beispiel dafür. Die Errichtung und der (sichere) Betrieb solcher Anlagen stellen Forschungszentren und beteiligte Unternehmen vor völlig neue Anforderungen hinsichtlich des Entwurfs wie auch des Betriebs solcher großen Forschungsgeräte. Wenn nicht bereits bei der Planung der sichere Alltagsbetrieb berücksichtigt wurde, bleibt es offen, ob solche Anlagen in der Praxis noch beherrschbar sind bzw. was man tun muss, damit die Risiken für die Betreiber überschaubar bleiben.
Keywords: Wissenschaftliche Großanlagen, Beherrschbarkeit von Technik sicherer Betrieb von Anlagen
  • Book chapter
    in: BeHerrscht die Technik!? Band 3, Reihe: Arbeit und Technik im Wandel, Aachen: Shaker Verlag, 2016, 978-3-8440-4781-3, 55-64

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Permalink: https://www.hzdr.de/publications/Publ-24493
Publ.-Id: 24493


Instabilities and spin-up behaviour of a rotating magnetic field driven flow in a rectangular cavity

Galindo, V.ORC; Nauber, R.ORC; Räbiger, D.; Franke, S.; Beyer, H.; Büttner, L.; Czarske, J.; Eckert, S.
This study presents numerical simulations and experiments considering the flow of an electrically conducting fluid inside a cube driven by a rotating magnetic field (RMF). The investigations are focused on the spin-up, where a liquid metal (GaInSn) is suddenly exposed to an azimuthal body force generated by the RMF, and the subsequent flow development. The numerical simulations rely on a semi-analytical expression for the induced electromagnetic force density in an electrically conducting medium. Velocity distributions in two perpendicular planes are measured using a novel dual-plane, two-component ultrasound array Doppler velocimeter (UADV) with continuous data streaming, enabling long term measurements for investigating transient flows. This approach allows to identify the main emerging flow modes during the spontaneous transition from a stable flow to unstable flow regimes with exponentially growing velocity oscillations using the Proper Orthogonal Decomposition (POD) method.
Characteristic frequencies in the oscillating flow regimes are determined in the super critical range above the critical magnet Taylor number Ta_c=1.3x10^5 , where the transition from the steady double vortex structure of the secondary flow to an unstable regime with exponentially growing oscillations is detected.
The mean flow structures and the temporal evolution of the flow predicted by the numerical simulations and observed in experiments are in very good agreement.
Keywords: Rotating magnetic field, spin-up, flow instabilities, square container

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Permalink: https://www.hzdr.de/publications/Publ-24492
Publ.-Id: 24492


Hyperdoping by Ion Implantation for Extended Infrared Si p-n Photodiodes

Berencen, Y.; Prucnal, S.; Liu, F.; Wang, M.; Rebohle, L.; Zhou, S.; Helm, M.; Skorupa, W.
The development of room-temperature extended infrared Si photodetectors is of great interest for integrated photonics, optical communications, sensing and medical imaging applications [1]. The typical peak photoresponse of traditional Si photodetectors is between 700 and 900 nm, which is mostly limited by the 1.12 eV-Si indirect band gap. Nevertheless, such intrinsic material limitation can be circumvented by introducing transition metals or chalcogens into the Si band gap at concentrations far above those obtained at equilibrium conditions [1, 2]. Ion implantation and short-time annealing have been the adopted methods in those approaches. This new class of hyperdoped materials with a donor impurity band has been postulated as a promising route to extend the Si photoresponse at the short-wavelength infrared spectral region [3].
In this work, we report steady-state room-temperature extended infrared p-n photodiodes at the two primary telecommunication wavelengths from single-crystalline Si hyperdoped with Se concentrations as high as 9×1020 cm-3, which are introduced by a robust and reliable non-equilibrium processing consisting of ion implantation followed by millisecond-range flash lamp annealing (FLA). The FLA approach in the millisecond range allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase eExtended infrared photodetektorpitaxy induced during pulsed laser annealing [2]. The success of our devices is primarily based on the high quality of the developed n-type hyperdoped material, which is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface. A detailed description of the working principle and performance of the photodiodes as well as the main features in the studied wavelength region is provided.
[1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014).
[2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[3] I. Umezu, J. M. Warrender, S. Charnvanichborikarn, A. Kohno, J. S. Williams, M. Tabbal, D. G. Papazoglou, X. C.Zhang, and M. J. Aziz, J. Appl. Phys. 113, 213501 (2013).
Keywords: extended infrared Si photodetector, flash lamp annealing, pulsed laser annealing selenium, doping, ion implantation, solid phase epitaxy, liquid phase epitaxy
  • Lecture (Conference)
    Ion Beam-Enabled Nanoscale Fabrication and Advanced Materials Synthesis, Symposium PM1 at MRS Fall Mtg. 2016, 28.11.-02.12.2016, Boston MA, USA

Permalink: https://www.hzdr.de/publications/Publ-24491
Publ.-Id: 24491


Corrosion phenomena at and nanoscale anticorrosion treatments of pipe organ metallic materials using ion beam based methods

Pelic, B.; Skorupa, W.; Eule, D.
Historical pipe organs with their unique sound and beautiful housing are important objects of the European cultural heritage dating back to the 15th century for the oldest ones being playable yet. But new instruments are built permanently up to the present time. The instruments contain mostly a considerable number of metallic pipes (flute and reed types), which are sometimes prone to heavy corrosion attack, resulting finally in a loss of their voice. Under certain conditions, the atmospheric corrosion of reed pipe tongues as well as flute pipe foots consisting of Cu-Zn alloys (brass) and PbSn-based alloys, respectively, is strongly enhanced by traces of volatile organic compounds (especially acetic acid vapor) and other corrosive gases.
Experiments have been undertaken to explore the corrosion resistance of CuZn and PbSn-based alloys against vapour from an aqueous solution containing high acetic acid concentration (2 – 5 v/v%), by deposition of protective films of either Al2O3 or Al on the nanoscale using pulsed laser deposition (PLD) and magnetron sputtering (MS). Afterwards, in order to improve the adhesion between the deposited layer and the substrate as well as to perform a kind of nitridation of the coatings, the samples were implanted with nitrogen ions using the plasma immersion ion implantation (PI3) process.
Such a nanoscale coating (~50 nm) is then able to withstand stresses and vibrations due to sound generation in organ pipes. Moreover it produces a barrier to volatile organic acids and water vapour. The laboratory corrosion test of the applied protective treatment for lead-tin and brass samples were combined with the field work studies to approach the best conditions for the samples research in real environment. Some of the samples were exposed for 15 months in a small North-German church with a harmful (corrosive) indoor environment.
Modifying the surface of metals and thin film properties on the nanoscale using fundamental phenomena based on ion-solid interactions as well as standard conventional methods can create new technological applications in restoration and conservation to preserve our historical and modern cultural heritage.
Keywords: Ion implantation, Plasma immersion implantation, Brass, Pb-Sn-alloys, Nanotechnology
  • Lecture (Conference)
    Materials Issues in Art and Archaeology, Symposium TC3 at MRS Fall Mtg. 2016, 28.11.-02.12.2016, Boston MA, USA

Permalink: https://www.hzdr.de/publications/Publ-24490
Publ.-Id: 24490


The effect of melt flow on dendritic solidification in Ga–In alloys

Shevchenko, N.; Keplinger, O.; Hoppe, D.; Eckert, S.
Simultaneous study of solidification phenomena on different length scales (dendrite networks - microscale and flow structure - mesoscale) is a main advantage of a conventional X-ray radiography. This work is focused on new benchmark experiments with different modes of melt convection and their effect on the dendritic growth in metallic alloys. The directional solidification of Ga-In alloy within a Hele-Shaw cell was investigated in situ. The visualization experiments with sufficient spatial resolution (5-10 µm) deliver simultaneous information of both the dendrite structure and the flow patterns especially in the mushy zone and ahead of the solidification front. Our results show that convection alters the solutal field near the solidification front, leading to different microstructures or even the formation of freckle defects. Flow patterns, solute concentration, the mushy zone morphology and permeability, dendrite growth velocities were quantified by image analysis. Particular attention was paid to the temporal dynamics of equiaxed grain growth, which plays an important role in grain structure formation in solidifying alloys. Small equiaxed grains frequently appeared in the undercooled melt near a continuous strong plume. Two mechanisms are under discussion: (i) crystal fragments transported by the ascending flow from the mushy zone; (ii) the equiaxed dendrites nucleated in the vicinity of the ascending plume due to modification of the the temperature/ solutal fields. We explored experimentally the size, the velocity and the conditions of formation of these equiaxed dendrites.
Keywords: X-ray radiography, melt convection, directional solidification, equiaxed grains
  • Lecture (Conference)
    6th Decennial Conference on Solidification Processing (SP17), 25.-28.07.2017, Old Windsor, UK

Permalink: https://www.hzdr.de/publications/Publ-24489
Publ.-Id: 24489


Hydrodynamics in cellular grid packed bubble columns disclosed with ultrafast X-ray tomography

Wagner, M.; Möller, C.-O.; Hessenkemper, H.; Bieberle, M.; Hampel, U.; Schlüter, M.
The chemical industry is one of the largest consumers of energy and resources. Therefore, process intensification is a field of high interest. Although the chemical reactor is only part of a highly integrated process, its design can significantly affect the overall process efficiency. A very common reactor type is the bubble column in which a liquid and a gas phase react with each other. The mass transfer across the liquid-gas interface is a crucial parameter regarding the process efficiency and should be as high as possible. It can be increased by higher interfacial area and better mixing of the phases. In the past, various internals like static mixers and structured packings were tested in order to control the bubble hydrodynamics in the column. Recent investigations of the authors showed that periodic open cellular structures (POCS) tend to increase the mass transfer significantly. These internals are three-dimensional regular grids with various geometries.
At the Helmholtz-Zentrum Dresden – Rossendorf the ultrafast X-ray computed tomography (CT) system is used to provide insights into the hydrodynamics of such bubble column internals. This imaging technique produces up to 8,000 cross-sectional images per second and provides a spatial resolution of about 1 mm for gas-water contrast. Two simultaneously scanned measurement planes allow determining vertical velocities and with that the extraction of quasi three-dimensional data sets from the original cross-sectional image data. For varying POCS geometries and gas flow rates, the axial bubble velocities, time-averaged gas hold-ups and the Sauter mean diameter are quantified and compared to measurements of unpacked bubble columns.
Keywords: packed bubble column, ultrafast X-ray CT
  • Contribution to proceedings
    8th WORLD CONGRESS ON INDUSTRIAL PROCESS TOMOGRAPHY, 26.-29.09.2016, Foz do Iguaçu, Brasil
  • Lecture (Conference)
    Hydrodynamics in cellular grid packed bubble columns disclosed with ultrafast X-ray tomography, 27.09.2016, Foz do Iguaçu, Brasil

Permalink: https://www.hzdr.de/publications/Publ-24488
Publ.-Id: 24488


Combining in-situ synchrotron X-ray techniques to study the dendrite morphology in solidifying Ga–In alloys

Shevchenko, N.; Grenzer, J.; Keplinger, O.; Rack, A.; Hoppe, D.; Eckert, S.
The processes involved in the formation of different dendrite morphologies are rather complex and still far from being fully understood. To verify existing micro-structural models in situ, in high resolution, in time and space, X-ray techniques are needed. In this work, in situ synchrotron X-ray radiography and diffraction methods have been combined to study the evolution of dendritic microstructures during the solidification of Ga - In alloys. The in situ directional solidification experiments were performed at the ID19 beamline (ESRF, France) at a high spatial resolution of < 1 µm. The dendritic growth and essential dynamics of the sidearm development were quantified. Melt flow induces various effects on the dendrite and grain morphology primarily caused by the convective transport of the solute. Usually, the morphologies of these dendrites differ from those developing under purely diffusive condition. Our observations show a facilitation of the growth of primary trunks or lateral branches, a suppression of side branching, dendrite remelting and fragmentation. The dendrite morphologies with their random character are difficult to analyse by means of the 2D radiographic projections. The flow-induced variations of the local solute concentration may result in the changes of dendrite crystal orientations. The coupling of in situ X-ray imaging with X-ray diffraction provides additionally information of the crystallographic orientation of the growing dendrites. These measurements show that the Indium dendrites grow along the <110> orientation, typically observed in body-centered metals. The analysis of the diffraction patterns with its complex morphology show that further improvements towards a 3D imaging experiment are needed. These first results demonstrate that the combination of different X-ray techniques can provide new data about the solidification process and help to validate different solidification models.
Keywords: dendritic microstructure, crystallographic orientation, synchrotron X-ray radiography, X-ray diffraction
  • Poster
    6th Decennial Conference on Solidification Processing (SP17), 25.-28.07.2017, Old Windsor, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-24487
Publ.-Id: 24487


X-ray radiography studies of melt convection effects on dendritic evolution in Ga – In alloy

Shevchenko, N.; Roshchupkina, O.; Eckert, S.
X-ray radiography technique is a powerful tool for investigating solidification processes in metallic alloys. In particular, in-situ X-ray visualization enables a general, intuitive understanding of flow phenomena and dendrite formation in opaque systems. Our work is devoted to the in situ investigation of the dendritic growth during a bottom-up solidification of a Ga-25wt%In alloy under natural and forced convections. Natural convection occurs during the bottom-up solidification because a lighter solute is rejected during crystallization. Forced convection has been produced by a specific electromagnetic pump. The direction of forced melt flow is almost horizontal at the solidification front.
Melt flow induces various effects on the dendrite morphology primarily caused by the convective transport of solute. Our investigations show a facilitation of the growth of primary trunks or lateral branches, suppression of side branching, dendrite remelting, fragmentation or freckle formation. Typical radiographs of stabilized segregation freckles are shown in Fig. 1. We demonstrate that the actual manifestation of all phenomena depends sensitively on the dendrite orientation, the local direction and intensity of the flow. Forced flow eliminates solutal plumes and damps local fluctuations of solute. A preferential growth of the secondary arms occurs at the upstream side of the dendrites, whereas high solute concentration at the downstream side inhibits the formation of secondary branches. Flow patterns and local solute concentration were quantified by image analysis and related to the experimental conditions. These in situ experiments provide benchmark data that can be used to validate simulations of dendritic growth or channel segregations.
Keywords: X-ray radiography, solidification, dendrites, segregation, convection, electromagnetic stirring
  • Invited lecture (Conferences)
    The 4th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR2016), 11.-15.05.2016, Xi’an, China

Permalink: https://www.hzdr.de/publications/Publ-24486
Publ.-Id: 24486


Morphology and orientation of growing dendrites in GaIn alloy characterized by synchrotron X-ray techniques

Shevchenko, N.; Grenzer, J.; Roshchupkina, O.; Baehtz, C.; Eckert, S.
The dendrite growth kinetics and morphology have been of great interest in the solidification science and casting industry. A detailed analysis of the particular solidification phenomena requires techniques with a better spatial and temporal resolution. High resolution experimental data are also very important for verification of the existing microstructural models. We demonstrate an advantage of the synchrotron X-ray sources, which allows the unique combination of in situ synchrotron X-ray radiography with a spatial resolution of less than 0.5 µm and synchrotron X-ray diffraction. The directional solidification experiments of Ga–25wt%In alloys were performed at the ROBL beam line (BM20, European Synchrotron Radiation Facility, Grenoble) at an energy of 28.5 keV. The study is especially focused on the sidearm evolution, refraction and detachment, dendrite morphology and orientation. Typical radiographs of sidearm evolution of an indium dendrite are shown in Fig. 1. The development of sidearms is quantified by an image analysis in a manner appropriated for comparison to simulations. Furthermore, we report on first attempt of reconstruction of crystallographic orientation of growing dendrites by using the CaRIne crystallography software.
Keywords: synchrotron X-ray radiography, GaIn alloys, directional solidification, X-ray diffraction, sidearm evolution
  • Poster
    The 4th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR2016), 11.-15.05.2016, Xi’an, China

Permalink: https://www.hzdr.de/publications/Publ-24485
Publ.-Id: 24485


Metalle: Aktivatoren von Kreislaufwirtschaft und Recycling 4.0

Reuter, M. A.
Aktuell stammen etwa 70 % der weltweiten Zinkproduktion aus primärem Bergbau und der Rest aus Recycling und sekundärem Zink (Zn). Der Recyclinganteil steigt von Jahr zu Jahr gemeinsam mit der Technologie von Zn-Produktion und -recycling (Reuter et al. 2015a). Mehr als 50 % des Zinks wird heute aus Produkten am Ende ihrer Lebensdauer (EoL) zurückgewonnen. Beim Pb-Recycling werden etwa 60 % der gesamten Produktionsmenge erreicht (Reuter et al. 2015a). Vom Element Gold (Au) wurde im Zeitfenster von 1995 bis 2014 rund ein Drittel der gesamten Umsatzmenge rezykliert (Hewitt et al. 2015).
Keywords: Recycling, Zink
  • Book chapter
    Kausch, P., Matschullat, J., Bertau, M., Mischo, H.: Rohstoffwirtschaft und gesellschaftliche Entwicklung, Berlin: Springer Berlin Heidelberg, 2016, 978-3-662-48854-6, 73-98
    DOI: 10.1007/978-3-662-48855-3

Permalink: https://www.hzdr.de/publications/Publ-24484
Publ.-Id: 24484


Thermodynamics of Palladium (Pd) and Tantalum (Ta) Relevant to Secondary Copper Smelting

Shuva, M. A. H.; Rhamdhani, M. A.; Brooks, G. A.; Masood, S. H.; Reuter, M. A.
The slag-to-metal distribution ratios of palladium (Pd), Ls/mPd, in the range of oxygen partial pressure (pO2) from 10−10 to 10−7 atm at 1473 K to 1623 K (1200 °C to 1350 °C); distribution ratios of tantalum (Ta), Ls/mTa, in the range of pO2 from 10−16 to 10−12 atm at 1673 K and 1873 K (1400 °C and 1600 °C), have been determined in this study. The Ls/mPd in FeOx-CaO-SiO2-MgO and copper at 1573 K (1300 °C) and pO2 = 10−8 atm is dependant strongly on basicity of slag, i.e. (CaO + MgO)/SiO2 or optical basicity. The current results suggest that Pd presents in the FeOx-CaO-SiO2-MgO slag predominantly as Pd2+. The activity coefficient of PdO in the slag at 1573 K (1300 °C) and pO2 = 10−8 atm was calculated to be in the range of 3.89 × 10−3 to 2.63 × 10−2. The Ls/mPd was also found to increase with increasing of pO2 and with decreasing of temperature. It was observed that Ta mostly partition to slag phase and very small amount of Ta was found in liquid copper at the high temperature and reduced condition studied. It can be suggested that to promote recovery of palladium from Pd-containing e-waste, a slag with lower silica content and basic flux based, high temperature with reducing atmosphere, is highly desired particularly in secondary copper smelting.

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Permalink: https://www.hzdr.de/publications/Publ-24483
Publ.-Id: 24483


Mining of critical and strategic metals in socially and environmentally sensitive areas in Namibia

Tesh, D.; Barakos, G.; Musiyarira, H.; Mischo, H.
Namibia has a rapidly growing minerals industry and is a primary source for numerous valuable commodities, among which are many strategic metals; rare earth elements, tantalum and niobium. The insatiable global demand for such critical and strategic elements can therefore give Namibia an opportunity to become a major player in the market. The country has adopted a mining friendly policy that can attract investments and encourage the development of mining projects. Alongside this, some areas in Namibia are sensitive in terms of cultural heritage both socially and environmentally, whilst tourism grows as part of the competitive industry sectors. Thus, the potential exploitation of rare earths and respective metals may raise issues due to the presence of radioactivity, the use of hazardous chemical compounds and the treatment of their tailings. Under such controversial circumstances, future mining plans require thorough assessments and closer considerations with respect to the special boundary conditions that govern this specific sector of the mining industry. This paper investigates the mineability of three different deposits that are located in respective sensitive areas in Namibia with the use of evaluation indicators. Furthermore, suggestions are made in order to ensure the sustainability of the mining projects while fully satisfying the competing industries and preserving the environmental and cultural balance.
Keywords: Rare earth elements, niobium, strategic metals, environmental sustainability, mining in Namibia
  • Open Access Logo Contribution to proceedings
    24th World Mining Congress - Mining in a World of Innovation, 18.-21.10.2016, Rio de Janeiro, Brasil
    Proceedings of the 24th World Mining Congress, Rio de Janeiro: IBRAM

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Permalink: https://www.hzdr.de/publications/Publ-24482
Publ.-Id: 24482


Electron microprobe petrochronology ofzite-bearing garnet micaschists in the Oetztal-Stubai Complex (Alpeiner Valley, Stubai)

Schulz, B.; Krause, J.; Zimmermann, R.ORC
Monazite dating in metapelites is an emerging method to investigate polymetamorphic areas A protocol for Th–U–Pb dating of monazite by electron microprobe was adopted for a JEOL JXA-8530F. It was applied to the Variscan and Early- Alpine metamorphic Austroalpine Oetztal-Stubai Complex (OSC). In the Alpeiner Valley in the Stubai region, the Schrankogel complex is the eastern succession of the Central Metabasite Zone. In this part, metabasites are alternating with metapelites. In 4 samples from micaschist lenses, dominantly Carboniferous monazite isochrone ages at 335 ± 4 Ma, 320 ± 4 Ma; 319 ± 4 Ma and 319 ± 4 Ma were obtained. The micaschist samples with diverse modal compositions and variable bulk rock Ca contents of calculated assay, display distinct monazite microstructures, as quantified by automated SEM-MLA (mineral liberation analysis) routines. Clusters of small monazite could indicate new crystallization and yielded isochrones at 313 and 304 Ma. In contrast, corona structures of apatite and allanite around large monazites with isochrones between 350 and 315 Ma suggest a decomposition during decreasing temperature. Garnets in metapelitic assemblages display growth zonations with low pyrope contents in the cores and pyrope-rich rims. A prograde metamorphism with high pressure amphibolite-facies peak conditions at * 12 kbar and * 680 °C, and a post Pmax path with decompression to 4 kbar and 640–600 °C was estimated from the micaschists and from zoned Ca-amphiboles in retrogressed amphibolitized eclogites. The P–T path entered the monazite stability field during the decompression. This signals a Carboniferous age of the metamorphism. A minor population in one sample is composed of sporadic Permian single monazite ages. A Creta- ceous monazite population is lacking. In the wide parts of the Austroalpine basement with Carboniferous-to-Cretaceous mica mixing ages, monazite age populations allow to discriminate a distinct Permian metamorphic event.
Keywords: Th–U–Pb-monazite dating; Geothermobarometry; Automated SEM mineral liberation analysis; Variscan; Austroalpine basement; Eastern Alps

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  • Secondary publication expected from 08.11.2020

Permalink: https://www.hzdr.de/publications/Publ-24481
Publ.-Id: 24481


Tracing the Gouy phase shift of focused, radially polarized THz pulses

Kaltenecker, K. J.; König-Otto, J. C.; Mittendorff, M.; Winnerl, S.; Schneider, H.; Helm, M.; Helm, H.; Walther, M.; Fischer, B. M.
THz microscopic imaging is used to extract the Gouy phase shift of the transverse and longitudinal field components of a tightly focused, radially polarized beam. We demonstrate that the applied THz time domain approach allows to observe directly the evolution of the geometric phase as the wave propagates through the focus. Our method yields a Gouy phase shift of 2π for the transverse component and of π for the longitudinal component. In addition, we apply our method to the well-known case of a focused, linearly polarized beam and pinpoint a fundamental connection between the field components of tightly focused, radially and linearly polarized light. The applied procedure is universal and may even allow to determine the geometric phase of arbitrary shaped and polarized propagating waves.
Keywords: Terahertz, Gouy phase
  • Invited lecture (Conferences)
    41st International Conference on Infrared, Millimeter and Terahertz Waves, 25.-30.09.2016, Kopenhagen, Denmark
  • Contribution to proceedings
    41st International Conference on Infrared, Millimeter and Terahertz Waves, 25.-30.09.2016, Kopenhagen, Denmark, 1-3
    DOI: 10.1109/IRMMW-THz.2016.7758577

Permalink: https://www.hzdr.de/publications/Publ-24480
Publ.-Id: 24480


On the experimental investigation of gas-liquid flow in bubble columns using ultrafast X-ray tomography and radioactive particle tracking

Azizi, S.; Yadav, A.; Lau, Y. M.; Hampel, U.; Roy, S.; Schubert, M.
Several techniques have been developed in the past to measure gas and liquid phase dynamics; however, reported data were mostly gathered individually for either liquid velocity, or volume fraction (phase holdup), but never when both are measured in the same system. In this work, arguably for the first time, bubble column hydrodynamics have been investigated using two complementary advanced non-invasive measurement techniques, namely Ultrafast X-ray Computed Tomography (UXCT) and Radioactive Particle Tracking (RPT). The UXCT experimental data in terms of gas phase structure is used in a supportive way to explain the liquid velocity profiles of the RPT data. Results of both experimental techniques are verified in a complementary manner using the mass conservation calculation. The results show good agreement. It is envisioned that the presented data would be helpful in the development and validation of numerical models for better predicting the flow profiles in bubble columns.
Keywords: Gas-liquid flow, Bubble column, Radioactive particle tracking, Ultrafast X-ray computed tomography
  • Lecture (Conference)
    ICMF 2016 International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
  • Chemical Engineering Science 170(2017), 320-331
    DOI: 10.1016/j.ces.2017.02.015

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Permalink: https://www.hzdr.de/publications/Publ-24479
Publ.-Id: 24479


Relation between Bubble Dispersion and Liquid Flow Field in Bubble Columns: A Complementary Study using Ultrafast X-Ray Tomography and Radioactive Particle Tracking

Azizi, S.; Yadav, A.; Yuk Man, L.; Roy, S.; Schubert, M.
Bubble column reactors are widely used in chemical and petrochemical industries due to their simple design and beneficial mass and heat transfer rates. The design of bubble columns requires thoughtful information about the complex gas-liquid hydrodynamics. The bubble size distribution, which results from bubble-liquid interactions, has a crucial impact on the reactor performance. Furthermore, reliable modeling of bubble columns requires validated hydrodynamic information.
In the present work, Radioactive Particle Tracking (RPT) and Ultrafast X-Ray Tomography (XRT) were applied for the first time at one bubble column setup to study the liquid velocity field and the corresponding bubble size distributions at different axial positions. In particular, the relation between the bubble dispersion, i.e. size and velocity, and the liquid flow field will be discussed. The velocity distribution of the liquid phase influences the bubble breakup and coalescence rates and accordingly the bubble size. In turn, turbulence and recirculation of the liquid phase depend on the bubble sizes. This mutual interaction will be revealed based on experiments with different distributer designs.
Keywords: RPT, XRT, Experiment, Bubble column
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations- und Schüttguttechnik, Mehrphasenströmungen und Computational Fluid Dynamics, 29.02.-02.03.2016, Bingen, Germany

Permalink: https://www.hzdr.de/publications/Publ-24478
Publ.-Id: 24478


Multiphase CFD activities at HZDR

Lucas, D.
The poster gives an overview on the main working fields of the CFD department of HZDR.
Keywords: CFD, multiphase, multi-fluid
  • Poster
    14th Multiphase Flow Conference & Short Course, 08.-10.11.2016, Dresden, Deutschland
  • Poster
    16th Multiphase Flow Conference and Short Course, 13.-16.11.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-24477
Publ.-Id: 24477


Validation of the baseline model for poly-disperse bubbly flows

Lucas, D.; Krepper, E.; Rzehak, R.
During the last years a modelling framework for CFD-simulations of poly-disperse bubbly flows using the Euler-Euler approach was formulated at Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The main idea behind is to achieve a consolidation of multiphase CFD by having a fixed set of closures applicable for a range of expected local flow conditions (Lucas et al., 2016). The corresponding closures concern the momentum transfer between liquid and gaseous phases, the influence of gas on the liquid phase turbulence and models for bubble breakup and coalescence (Rzehak et al., 2015, Liao et. al 2015). This baseline model was applied to a large variety of bubbly flows as round and rectangular bubble columns, bubble plumes, airlift reactors and upwards vertical pipe flow with different pipe diameter without any modification or tuning. In the results a good or at least acceptable agreement was found for most of the cases, but for some other cases also clear deviations were observed. Such deficiencies have to be investigated more in detail to improve the models step by step.
In this work the model is applied to co-current upward, counter-current and co-current downward vertical pipe flows recently measured at the HZDR TOPFLOW facility using ultrafast X-ray tomography. The results are discussed in detail.
Keywords: CFD, bubbly flow, downward, counter-current, baseline model, poly-disperse
  • Contribution to proceedings
    Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation (CFD4NRS-6), 13.-15.09.2016, Cambridge, USA
  • Lecture (Conference)
    Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, 13.-15.09.2016, Cambridge, USA

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Permalink: https://www.hzdr.de/publications/Publ-24476
Publ.-Id: 24476


Nuclear Laboratories and Experiments: Overview and HZDR

Bemmerer, D.
I provide an overview of experimental nuclear astrophysics research in Germany. In addition, I review related recent progress at HZDR Dresden.
Keywords: Experimental Nuclear Astrophysics
  • Invited lecture (Conferences)
    Nuclear Astrophysics in Germany - A Community Meeting in Darmstadt, 15.-16.11.2016, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24475
Publ.-Id: 24475


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