Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35836 Publications

The essence of time – fertile skarn formation in the Variscan Orogenic Belt

Burisch, M.; Gerdes, A.; Meinert, L.; Albert, R.; Seifert, T.; Gutzmer, J.

Extending from Northern America to Central China the Variscan belt is a Paleozoic Orogen exceptionally well endowed in magmatic-hydrothermal ore deposits, including skarn deposits. Yet, the genesis of fertile skarns and their distinction from barren equivalents in orogenic zones is only poorly constrained. Here, we present innovative U-Pb laser-ablation inductively-coupled-plasma mass-spectrometry geochronology of garnet from different skarns in the Erzgebirge, a classic metallogenic province in central Europe. Garnet ages obtained not only constrain the timing of fertile skarn formation and associated Sn, W, Fe, Zn, Cu and In mineralization, but also clearly distinguish these from barren skarn bodies. We show that barren skarns formed during times of peak regional metamorphism at ∼340 Ma whereas mineralized skarns are temporally associated with late-orogenic magmatism at ∼325-313 Ma as well as post-orogenic magmatism at ∼308-295 Ma. The recognition of discrete mineralization events associated with the largest and economically most important skarn deposits provides valuable insight into the punctuated evolution of magmatic-hydrothermal systems in ancient collisional orogens on a regional scale; this has important implications to direct future mineral exploration.

Keywords: LA-ICP-MS U-Pb geochronology; metasomatism; hydrothermal ore deposit; garnet; Erzgebirge

Permalink: https://www.hzdr.de/publications/Publ-28403
Publ.-Id: 28403


An introduction to the thematic issue on “Ore deposits in the Variscan basement of Central Europe”

Gutzmer, J.; Markl, G.

Much of the basement geology of Central Europe is characterized by volcanosedimentary successions of Late Precambrian and Early Paleozoic age that have been variably deformed and metamorphosed during the Variscan orogeny, followed by the intrusion of voluminous granites. The Variscan orogen records the closure of the Rheic ocean and the collision of Laurussia with Gondwana to form the Supercontinent Pangaea, and occurred as a series of protracted geotectonic events providing a suitable framework for the formation of a diverse range of ore deposits.

It comes as no surprise that the Variscan basement is host to most significant ore deposits of Central Europe. These ore deposits did not only provide the raw materials needed for industrial development in the past, but their mining yielded the need for scientific research and technological innovation. This need was also expressed by the publication of the world’s first textbook dedicated to economic geology as a distinct subdiscipline of the geosciences (Cotta 1855).

Industrial exploitation of most ore deposits of the Variscan basement in Central Europe ceased towards the end of the 20th century, typically due to subdued metal prices, but not motivated by a lack of mineral resources. Yet, following the demise of the mining sector there was the prevailing perception that Central Europe had little to offer for future exploration. This erroneous perception has seen a surprising reversal in the last decade. Renewed exploration interest is attributable not only to higher commodity prices but also to the realization of the significant geostrategic risk of highly industrialized countries to be entirely dependent on raw materials imports (EU 2008).

Permalink: https://www.hzdr.de/publications/Publ-28402
Publ.-Id: 28402


Neutron transmission imaging studies on particle-laden liquid metal flow driven by a disk-type rotating permanent magnet induction pump

Lappan, T.; Sarma, M.; Heitkam, S.; Mannes, D.; Trtik, P.; Eckert, K.; Eckert, S.

In metallurgy, gas-stirring ladle treatment of aluminum alloys and steels is applied for the control of non-metallic inclu-sion population. The intense mixing of the molten metal bath by the bubbly flow provides the agglomeration of strongly dispersed solid inclusions and subsequently, the entrapment of agglomerates by gas bubbles floating up into the slag.
This work focuses on flow-induced particle agglomeration in liquid metal. We perform model experiments to study particle-laden liquid metal flow around a circular cylinder. The fluid flow is driven by an electromagnetic induction pump. Neutron transmission radiography is employed for time-resolved visualization of the particle trajectories in the opaque liquid metal.
The experimental setup is designed as a closed liquid metal loop shown in Figure 1a. The flat channel, made of welded stainless steel, has a rectangular inner cross section with 3 mm depth, i.e. parallel to neutron beam direction, and 30 mm width. A 5 mm diameter cylindrical obstacle representing a single rising bubble is placed in the mid-dle of the straight channel section. The disk-type rotating permanent magnet induction pump is locat-ed at the lower U-shaped channel section. By controlling the pump rotational speed in the range of 15…95 min-1, the average flow velocity of 6…40 cm/s results during the measurements.
Low-melting gallium alloyed with 7 wt-% tin (Ga-Sn) is employed as model liquid metal, so that the experimental setup can be operated at room temperature without additional heating. Gadolinium(III) oxide particles (Gd2O3) in a grain size range of 400-600 µm serve as model particles, since they have superior attenuation characteristics for neutron radiation compared to the liquid metal. To introduce the solid Gd2O3 particles into the liquid Ga-Sn, a two-step mixing protocol is developed. It includes the initial preparation of a paste-like suspension with high solid content of wetted particles, followed by a second mixing step inside the Ga-Sn-filled channel by means of the electromagnetic pump. In-creased rotational speed up to 550 min-1 combined with changing rotating direction is applied for in-tense stirring and distributing the particles homogenously in the liquid metal.
The neutron imaging studies are performed at the SINQ beamlines NEUTRA and ICON at the Paul Scherrer Institute, Villigen, Switzerland. By imaging with both high spatial (0.1 mm/px) and temporal (100 fps) resolution, the fast-moving particles are captured as single objects. In terms of en-hanced contrast-to-noise ratio between the Gd2O3 particles and the surrounding liquid Ga-Sn, the currently best neutron image quality is achieved on the ICON beamline due to the higher beam aper-ture (80 mm) yielding the maximum neutron flux of 1.4 x 108 cm-2 s-1 mA-1. The neutron transmission image sequences provide raw data on particle positions and motion in the liquid metal loop, in particular in the shear flow around the cylindrical obstacle. By image processing and data analyzing, we investigate the particle behavior depending on various fluid flow rates.

Keywords: neutron transmission imaging; induction pump; inclusions; liquid metal; shear flow

  • Lecture (Conference)
    11th Pamir International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France
  • Contribution to proceedings
    11th Pamir International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France

Permalink: https://www.hzdr.de/publications/Publ-28401
Publ.-Id: 28401


Recovery of REEs, Zr(+Hf), Mn and Nb by H2SO4 leaching of eudialyte concentrate

Balinski, A.; Atanasova, P.; Wiche, O.; Kelly, N.; Reuter, M. A.; Scharf, C.

In this study three hydrometallurgical methods are described for leaching of a eudialyte concentrate with H2SO4: (i) direct leaching, (ii) fast leaching and (iii) water leaching of dehydrated acid/concentrate mixture. It is demonstrated how to obtain a silica free solution, how parameter variations impact the properties of precipitated silica and which processes lead to losses of valuable components during leaching. Furthermore, the acid solubility of gangue minerals in the concentrate is analyzed and the resulting consequences in terms of leach solution contamination and acid consumption are discussed. The best result in terms of the average yield of value components (REEs, Zr(+Hf), Mn and Nb) of 86 % is obtained by direct leaching under mild conditions (cH2SO4=1 mol/L; TL=60 °C). However, released silicic acid does not precipitate and aggregates at pulp density ϱPD,L=100 kg/m3 by gelling. Fast leaching allows the efficient removal of silica at high solid-liquid ratios in the pre-treatment stage. Due to mass transfer limitations, high efficiency stirrers are crucial for achieving high yields in short reaction times. Dehydration of the acid/concentrate mixture before water leaching can be a good alternative if well-defined amount of acid is used; however, high energy input is needed.

Keywords: eudialyte concentrate; silicate raw materials; aggregation of polysilicic acid; kinetic inhibition; gelling; leaching; mass transfer limitations; rare earth elements; zirconium; hafnium; niobium; manganese

Permalink: https://www.hzdr.de/publications/Publ-28400
Publ.-Id: 28400


Bioangeln zum Recycling Seltener Erden Selektive Trennung von Mineralen durch Phagen-gebundene Peptide

Lederer, F. L.

Selten-Erd-Elemente (SEE) sind 17 verschiedene Elemente (Scandium, Yttrium sowie die sog. Lanthanoide), die weltweit in nur wenigen Regionen in abbauwürdigen Mengen zu finden sind. SEE gelten als Schlüsselkomponenten der Hightech-Industrie und werden unter anderem in Windturbinen, Smartphones und Energiesparlampen eingesetzt.

Keywords: SEE; Phage Surface Display

  • GIT Laborfachzeitschrift 69(2019)2, 27-29

Permalink: https://www.hzdr.de/publications/Publ-28399
Publ.-Id: 28399


X-ray and neutron imaging studies on particle-laden liquid metal flow

Lappan, T.; Eckert, S.

In metallurgy, the achievement of inclusion cleanliness is a major challenge for the production of high-performance structural and functional metallic materials like aluminium alloys and steels. Ladle treat-ment of molten metal by gas injection has been employed for a long time as the processing stage is mainly responsible for the control of non-metallic inclusions in metal alloys. In these ladles, inclusion are separated by the combination of settling down and floating up. Since bigger inclusion aggregates are eliminated more easily, agglomeration is supposed to play an essential role. In case of the floata-tion process, the probabilities of collision as well as attachment between gas bubbles and solid in-clusions is strongly dependent on their sizes.
This work is focussed on the visualization of three-phase particle-laden liquid metal flow in model experiments, applying 2D X-ray and neutron transmission imaging. Low-melting gallium-based alloys are employed for the imaging studies at room temperature. Modell particles containing tungsten and gadolinium are used due to their excellent attenuation characteristics for polychromatic X-ray and thermal neutrons, respectively. Injection of inert argon gas drives the liquid metal flow in a rectangular shaped vessel having a gap size of up to 20 mm. For both X-ray and neutron imaging, the time-resolved measurements are performed by means of a scintillation screen in combination with a sCMOS camera. The captured trajectories of rising millimetre-sized gas bubbles and submillimetre-sized solid particles, carried by the bubbly liquid metal flow, are analysed regarding bubble - particle and particle - particle interactions.

Keywords: X-ray transmission imaging; neutron transmission imaging; inclusions; liquid metal

  • Lecture (Conference)
    Materials Science and Engineering Congress 2018 (MSE 2018), 26.-28.09.2018, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28398
Publ.-Id: 28398


Scanning Transmission Ion Detection in the Helium Ion Microscope

Serralta, E.; Klingner, N.; Hlawacek, G.

The helium ion microscope has already proven its value for high-resolution imaging, composition analysis, nanofabrication, and material modification. However, imaging in transmission mode remains not fully explored. Mass-thickness contrast has been studied using a conversion plate below the specimen and collecting secondary electrons with an ET detector. Changing from bright to dark field regime was demonstrated using an annular microchannel plate and changing the acceptance angle by adjusting the distance between the sensor and the sample. Channeling and diffraction phenomena provide information about the crystal structure and can be recorded by a position-sensitive detector. In this report, we present our approach to explore this imaging mode, the challenges and main figures of merit. Our test setup with a position-sensitive detector will be shown, and simulations of the contrast mechanism will be presented.

  • Poster
    2nd international HeFIB conference on Helium and emerging Focused Ion Beams, 11.-13.06.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28397
Publ.-Id: 28397


Application of marine amphiphilic siderophores in froth flotation process

Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.

Siderophores are biomolecules, which can form strong complexes with different metals. They are produced by microorganisms and a biotechnological production of these chelators offers an application in different processing methods. Particularly amphiphilic siderophores are very interesting for the froth flotation process. The hydrophilic part, carrying hydroxamate groups is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested, that siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubbles and avoid additional chemicals and further working steps for making the target mineral particles hydrophobic. The aim of this study is to show the usage of amphiphilic siderophores in froth flotation process in different scales and with different minerals.

  • Lecture (others)
    UCT Biohydrometallurgy meeting, 19.06.2018, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-28396
Publ.-Id: 28396


Enhanced photoresponses of an optically driven VO₂-based terahertz wave modulator near percolation threshold

Zhai, Z.-H.; Zhu, H.-F.; Shi, Q.; Chen, S.-C.; Li, J.; Li, Z.-R.; Schneider, H.; Zhu, L.-G.

We proposed and demonstrated a method to enhance photoresponses in the timescale from nanoseconds to microseconds of an all optically driven VO₂-based terahertz (THz) wave modulator by driving the initial VO₂ close to percolation threshold (via externally heating the initial VO₂ thin film near insulator-to-metal transition temperature). We experimentally realized 10-fold, 3-fold, and 3-fold improvement of photosensitivity, photoresponsivity, and optical modulation bandwidth of the VO₂-based THz wave modulator, respectively. Percolation theory, along with the macroscopic conductivity response, was used to explain the mechanism for photomodulation response enhancement. The enhanced photomodulation response is promising especially for optical modulators and photodetectors. This approach is also compatible with other optimization methods and can be further used to enhance other VO₂-based optoelectronic devices.

Keywords: Vanadiumdioxide; terahertz modulator

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Permalink: https://www.hzdr.de/publications/Publ-28395
Publ.-Id: 28395


Thermodynamic and structural studies on the Ln(III)/An(III) malate complexation

Taube, F.; Drobot, B.; Roßberg, A.; Foerstendorf, H.; Acker, M.; Patzschke, M.; Trumm, M.; Taut, S.; Stumpf, T.

The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi−method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (logβ0, ΔrH0 m,2, ΔrS0 m, ΔrG0 m) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X–ray absorption fine structure spectroscopy complemented with quantum-mechanical ab–initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes. The metal is coordinated by two carboxylate groups and a hydroxyl group. UV–Vis, laser fluorescence and calorimetric studies consistently yielded two complex species having a 1:1 and a 1:2 (metal:malate) stoichiometry. Parallel factor analysis and iterative transformation factor analysis were applied to decompose experimental spectra into their single components and to determine stability constants. The 1:1 and 1:2 Nd(III) malate complexation constants determined by isothermal titration calorimetry were extrapolated to zero ionic strength using the specific ion interaction theory, yielding logβ1 0 and logβ2 0 of about 6 and 9, respectively. The respective complexation enthalpies ΔrH0 m,1 and ΔrH0 m,2 showed average values of 5 kJ·mol−1 which are typical for small organic molecules. The comparison of Nd(III) and Am(III) malate complexes showed that the malate binding motif, the speciation and the thermodynamics can be transferred from lanthanides(III) to actinides(III) supporting the 4f–/ 5f–element homology.

Permalink: https://www.hzdr.de/publications/Publ-28394
Publ.-Id: 28394


Ln(III)/An(III) Retention on CSH Phases and the Influence of Malate

Taube, F.; Roßberg, A.; Acker, M.; Foerstendorf, H.; Taut, S.; Stumpf, T.

Concrete widely serves as an engineering barrier and for waste conditioning in nuclear waste re-positories. Organic additives like poly(hydroxyl)carboxylates are commonly used for tuning the physico-chemical and mechanical properties of fresh concrete. In the worst-case scenario of wa-ter intrusion into the waste repository, the concrete may degrade, so that the soluble organic ad-ditives will be leached out and may form stable radionuclide (RN) complexes. Consequently, for a long-term risk assessment in nuclear waste repositories, the interactions of RNs with cement additives and CSH phases (main phase of cement) must be known. Americium(III) is one of the RN that will determine the radiotoxicity of a waste repository for a long time. As a model com-pound for cement additives malic acid (α-hydroxydicarboxylic acid) was chosen...

  • Lecture (Conference)
    4th International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 06.-09.11.2018, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-28393
Publ.-Id: 28393


β8 integrin mediates pancreatic cancer cell radiochemoresistance

Jin, S.; Lee, W.-C.; Aust, D.; Pikarsky, C.; Cordes, N.

Pancreatic ductal adenocarcinoma (PDAC) stroma, composed of extracellular matrix (ECM) proteins, promotes therapy resistance and poor survival rate. Integrin-mediated cell/ECM interactions are well known to controls cancer cell survival, proliferation and therapy resistance. Here, we identified β8 integrin in a high-throughput knockdown screen in three-dimensional (3D), ECM-based cell cultures for novel focal adhesion protein targets as critical determinant of PDAC cell radiochemoresistance. Intriguingly, β8 integrin localizes with the golgi apparatus perinuclearly in PDAC cells and resection specimen from PDAC patients. Upon radiogenic genotoxic injury, β8 integrin shows a microtubule-dependent perinuclear-to-cytoplasmic shift as well as strong changes in its proteomic interactome regarding the cell functions transport, catalysis and binding. Parts of this interactome link β8 integrin to autophagy, which is diminished in the absence of β8 integrin. Collectively, our data reveal β8 integrin to critically co-regulate PDAC cell radiochemoresistance, intracellular vesicle trafficking and autophagy upon irradiation.

Keywords: Pancreatic cancer; β8 integrin; radiochemoresistance; cell survival

Permalink: https://www.hzdr.de/publications/Publ-28392
Publ.-Id: 28392


Am3+ Malate Sorption on CSH Phases

Taube, F.; Acker, M.; Roßberg, A.; Taut, S.; Stumpf, T.

Concrete widely serves as an engineering barrier and for waste conditioning in nuclear waste re-positories. Organic additives like poly(hydroxyl)carboxylates are commonly used for tuning the physico-chemical and mechanical properties of fresh concrete. In the worst-case scenario of wa-ter intrusion into the waste repository, the concrete may degrade, so that the soluble organic ad-ditives will be leached out and may form stable radionuclide (RN) complexes. Consequently, for a long-term risk assessment in nuclear waste repositories, the interactions of RNs with cement additives and CSH phases (main phase of cement) must be known. Americium(III) is one of the RN that will determine the radiotoxicity of a waste repository for a long time. As a model com-pound for cement additives malic acid (α-hydroxydicarboxylic acid) was chosen...

  • Poster
    2nd Workshop on Calcium-Silicate Hydrates Containing Aluminium: C-A-S-H II, 23.-24.04.2018, Dübendorf, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-28391
Publ.-Id: 28391


Lithium Ion Beams from Liquid Metal Alloy Ion Sources

Pilz, W.; Mazarov, P.; Klingner, N.; Bauerdick, S.; Bischoff, L.

In recent years Focused Ion Beam (FIB) processing has been developed into a well-established and promising technique in nearly all fields of nanotechnology for patterning and prototyping on the µm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the FIB application fields beside all other source concepts. The need of light elements like Li was investigated using various alloys. A promising candidate is a Ga35Bi60Li5 based LMAIS which is introduced in more detail and operates stable for more than 1000 µAh. It enables high resolution imaging and patterning using Li and sample modification using Ga or heavy polyatomic Bi clusters, all coming from one ion source.

Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Source; Li ions

  • Open Access Logo Journal of Vacuum Science & Technology B 37(2019)2, 021802-1-021802-4
    DOI: 10.1116/1.5086271

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Permalink: https://www.hzdr.de/publications/Publ-28390
Publ.-Id: 28390


Is hydroxypyridonate 3,4,3‐LI(1,2‐HOPO) a good competitor of fetuin for uranyl metabolism?

Younes, A.; Creff, G.; Beccia, M. R.; Moisy, P.; Roques, J.; Aupiais, J.; Hennig, C.; Solari, P. L.; Den Auwer, C.; Vitaud, C.

Uranium is widespread in the environment, resulting both from natural occurrences and anthropogenic activities. Its toxicity is mainly chemical rather than radiological. In the blood it is transported as uranyl UO22+ cation and forms complexes with small ligands like carbonates and with some proteins. From there it reaches the skeleton, its main target organ for accumu lation. Fetuin is a serum protein involved in biomineralization processes which was demonstrated to be the main UO22+‐binder in vitro. Fetuin’s life cycle ends in bone. It is thus suspected to be a key protagonist of U accumulation in this organ. Up to now, there has been no effective treatment for the removal of U from the body and studies devoted to the interactions involving chelating agents with both UO22+ and its protein targets are lacking. The present work aims at studying the potential role of the 3,4,3‐LI(1,2‐HOPO) as a promising chelating agent in competition with fetuin. The apparent affinity constant of the 3,4,3‐LI(1,2‐HOPO) was first determined, giving evidence for its very high affinity similarity to that of fetuin. Chromatography experiments, aimed at identifying the complexes formed and quantify their UO22+ content, and spectroscopic structural investigations (XAS) were carried out, demonstrating that the 3,4,3‐LI(1,2‐HOPO) inhibits/limits the formation of fetuin‐uranyl complexes in stoichiometric conditions. But surprisingly, possible ternary complexes stable enough to remain present after the process, were identified for sub stoichiometric conditions of HOPO versus fetuin. These results contribute to the understanding of the mechanisms accounting for U residual accumulation despite the chelation therapy after internal contamination.

Permalink: https://www.hzdr.de/publications/Publ-28389
Publ.-Id: 28389


Compositional Data Analysis - Mineral Chemistry

Frenzel, M.

Short introduction to general principles for the statistical analysis of mineral chemistry data.

  • Lecture (others)
    Forschungsseminar Lagerstättenlehre, 09.10.2018, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28388
Publ.-Id: 28388


Compositional Data Analysis - General Principles

Frenzel, M.

Any data measured (or reported) in terms of proportions of a whole is called ‘compositional’. Virtually all geochemical data falls under this category. Because such data has a number of special properties, specific procedures are required for its statistical analysis. Generally, it cannot be meaningfully analyzed by methods designed for the analysis of multivariate Gaussian data, such as the standard regression analysis still used by many geologists.

This lecture is intended to give a brief overview of the most important mathematical characteristics of compositional data, and what consequences these have for the statistical analysis of such data. It will provide the theoretical foundations for the next lecture(s) in which the specific problems associated to the analysis of mineral chemistry data (lecture 2) and hierarchical data structures (lecture 3) will be considered in somewhat more detail. These later two lectures are intended as more practical guides to actual data analysis.

  • Lecture (others)
    Forschungsseminar Lagerstättenlehre, 18.09.2018, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28387
Publ.-Id: 28387


Chapter 23: fuel cells based on biomass

Hassanzadeh, A.; Behrad Vakylabad, A.

Sustainable source of energy is the emergent necessity for the near future which comes from the simultaneous two issues: The growing request for energy and the necessity to strictly limit and control carbon emissions with warning on global warming. Although there are very terrible statistics of CO2 emission worldwide (110 billion metric tonnes in 2010 with estimated 140 billion metric tonnes by 2035), there are also hopes in that the plants and biomasses may sequester more than 260 Giga tonnes of CO2 annually. Interestingly, approximately 183 Giga tons of CO2 are annually fixed through microalgae to produce about 100 Giga tons of its biomass. These are other great motivations to invest in microalgae-based technologies such as microbial fuel cell (MFC) which are the cells to produce power from simultaneous CO2 sequestration and wastewater treatment. In this chapter, we present an overview of the current status together with the future prospects on the fuel cells based on biomass. Additionally, the necessities for scaling up the MFCs have been discussed. The main motivation for research and developments in this field is highlighted to develop green energy and technology for environmental protection. Specifically, latest researches and achievements in MFC technology are presented. The main constituents of MFC, i.e. anodes, cathodes, substrates, and microorganisms are discussed with the latest researches and developments. As a rule of thumb, for scale-up purposes, there is a threshold volumetric power density of 1 kWm-3, maintaining of which as the lab-scale one is challengeable. However, there are suggestions such as optimizing some key factors, such as and appropriately spacing the electrodes with the specific surface area. In this regard, three-dimensional electrodes with highly surface area for enhanced microbial attachment and anodic performance such as tenuous graphite rods have been introduced.

Keywords: Microbial fuel cell (MFC); CO2 sequestration; chemical oxygen demand (COD); anode; cathode

  • Book chapter
    M. R. Rahimpour, Mohammad K. D. Manshadi: Bioenergy and the Advanced Application of Bio-Products and Microfluidic Devices, Hershey, United States: IGI Global, 2019, 1522575340-1

Permalink: https://www.hzdr.de/publications/Publ-28386
Publ.-Id: 28386


Параллельная реализация псевдоспектрального решателя уравнений Максвелла

Панова, Е. А.; Бастраков, С. И.; Ефименко, Е. С.; Волокитин, В. Д.; Гоносков, А. А.; Мееров, И. Б.

Дискретное быстрое преобразование Фурье (БПФ) позволяет рассчитывать временную эволюцию электромагнитных полей без численной дисперсии и дает ряд других преимуществ, существенных при численном моделировании некоторых физических процессов. Однако существенная нелокальность обработки данных при выполнении БПФ ограничивает возможности создания эффективных, хорошо масштабируемых суперкомпьютерных реализаций этого подхода. В работе проводится анализ перспектив эффективного распараллеливания вычислений на основе локального применения БПФ в пространственных доменах с перекрытиями, позволяющими согласованно переносить все возмущения между доменами за счет ограниченности скорости распространения электромагнитных возмущений.

Keywords: Maxwell's equations; fast Fourier transform; parallel computing; supercomputing technologies

  • Lecture (Conference)
    Параллельные вычислительные технологии (ПаВТ) 2019, 02.-04.04.2019, Калининград, Россия

Permalink: https://www.hzdr.de/publications/Publ-28385
Publ.-Id: 28385


Field-Driven Hopping Transport of Oxygen Vacancies in Memristive Oxide Switches with Interface-Mediated Resistive Switching

Du, N.; Manjunath, N.; Li, Y.; Menzel, S.; Linn, E.; Waser, R.; You, T.; Burger, D.; Skorupa, I.; Walczyk, D.; Walczyk, C.; Schmidt, O. G.; Schmidt, H.

We investigate the hopping transport of positively charged mobile oxygen vacancies V(o)(+)in electroforming-free bipolar memristive BiFeO3 switches by conducting impedance spectroscopy and quasistatic state-test measurements. We demonstrate that BiFeO3 switches with mobile oxygen vacancies (V-o(+)) and fixed substitutional Ti4+ donors on Fe3+ lattice sites close to the bottom electrode have a rectifying top electrode with an unflexible barrier height and a rectifying and/or nonrectifying bottom electrode with a flexible barrier height. The field-driven hopping transport of the oxygen vacancies determines the recon- figuration of the flexible barrier and the dynamics of the resistive switching. Average activation energies of 0.53 eV for trapping and of 0.31 eV for the release of oxygen vacancies by the Ti4+ donors during application of the SET and RESET excitation pulses are extracted, respectively. The larger activation energy during SET is experimentally verified by impedance spectroscopy measurements and evidences the local enhancement of the electrostatic potential profile at the bottom electrode due to the Ti4+ donors on Fe3+ lattice sites.

Keywords: BIFEO3; KINETICS; CONDUCTIVITY; TEMPERATURES; ELECTRODES; FILMS

Permalink: https://www.hzdr.de/publications/Publ-28384
Publ.-Id: 28384


A Novel Statistical Insight to Selection of the Best flotation Kinetic Model

Hassanzadeh, A.; Cagirici, S.; Ozturk, Z.

Many flotation kinetics models have been studied in the literature. Their applicability was extensively investigated and argued in detail. However, model selection criteria were not adequately discussed from the statistical points of view. In this investigation, the kinetic behavior of a complex copper sulfide ore was studied in a mechanical Denver flotation cell focusing on flotation kinetics of chalcopyrite, pyrite and molybdenite. Different flotation kinetics models including nine common empirical models and four mathematical models namely Hill, Chapman (Sigmodial function), single rectangular (Hyperbola equation) and exponential were applied to the experimental data. In addition to assessment of the goodness of fit criterion for each model, a factor of model complexity was considered using information criteria (IC) (i.e. Bayesian information (BIC), low of iterated logarithm (LILC) and Akaike information (AIC) indices). The obtained results showed that the IC indices could simply manifest the best-fitted model to the experimental data. Whereas, the coefficient of determination values (R2) were relatively same for all models. By taking the R2 and model complexity criteria into account, the exponential model was chosen as the best representative mathematical model to demonstrate chalcopyrite kinetic behavior. However, Chapman model was selected as the best one for the flotation of pyrite and molybdenite. In case of the common first-order flotation kinetics models, fast and slow flotation kinetic model (Kelsall) was reasonably fitted the best to the given data of chalcopyrite. However, the gas/solid kinetics adsorption model was chosen as the best-fitted one for pyrite and molybdenite. Furthermore, it was found that mathematical models represent better results in association with flotation kinetic behavior of chalcopyrite, pyrite and molybdenite due to the consideration of more parameters in modeling. Finally, it was concluded that the IC indices must be applied to the process of model selection due to consideration of goodness of fit, complexity of a model and model consistency.

Keywords: Flotation kinetics model; information criteria (IC); modeling; Akaike information criterion (AIC)

  • Contribution to proceedings
    XXIX International Mineral Processing Conference (IMPC), 15.09.-21.12.2018, Moscow, Russia
    A Novel Statistical Insight to Selection of the Best flotation Kinetic Model

Permalink: https://www.hzdr.de/publications/Publ-28383
Publ.-Id: 28383


Estimation of flotation rate constant and particle-bubble interactions considering key hydrodynamic parameters and their interrelations

Hassanzadehmahaleh, A.; Azizi, A.; Kouachi, S.; Karimi, M.; Celik, M. S.

Particle-bubble sub-processes cannot be directly and physically obtained in froth flotation due to the complexity of the process as well as numerous and dynamic interactions of particles and bubbles in an extremely intensive turbulent condition. Therefore, over the last three decades, two fundamental model configurations have been used as an only solution for prediction of particle-bubble collection efficiencies (E-coll). Additionally, the relative intensity of the main flotation parameters on flotation rate constant, particle-bubble interactions together with their interrelations is not adequately addressed in the literature.

The present study attempts in two separate phases to overcome these difficulties. In the first stage, prediction and evaluation of particle-bubble sub-processes are critically discussed by categorizing them in two configurations. The analytical models (approach I) commonly applied generalized Sutherland equation (E-c(GSE)), modified Dobby-Finch (E-a(DF)) and modified Schulze stability (E-s(SC) ) models. The second approach, numerical models, utilized Yoon-Luttrell (E-c(YL)), Yoon-Luttrell (intermediate) (E-a(YL)) and modified Schulze stability (E-s(SC)) models. In the second stage, relative intensity and interrelation of key effective hydrodynamic parameters on the probability of particle-bubble encounter (E-c) and flotation rate constant (k) are obtained and optimized by mea s of the response surface modeling (RSM) based on central composite design (CCD). Five key factors including particle size (1-100 mu m), particle density (1.3-4.1 kg/m(3)), bubble size (0.05-0.10 cm) and bubble velocity (10-30 cm/s) together with turbulence dissipation rate (18-30 m(2)/s(3)) are considered in order to maximize the responses including the k and E-c.

The results obtained show that the E-coll calculated by numerical techniques (configuration (II)) is greater than that of analytical approaches (configuration (I)) due to assumptions involved in using Yoon-Luttrell collision and attachment models. It is also found that under the conditions studied, particle size and bubble velocity are the most effective factors on E-c and k, respectively. Furthermore, not only the relative significance of factors on E-c and k but also the interrelation of cell turbulence and bubble size as well as bubble velocity and turbulence are shown to be inconsistent in the literature and thus require further studies. We briefly reported the main longstanding challenges in flotation kinetic modeling and emphasized on a serious need for fulfilling lack of physical observations. Finally, the presented analyses with respect to three-zone model offer a new concept for the extension of common flotation modeling approach using analytical and numerical techniques.

Keywords: Flotation rate constant; Particle–bubble interactions; Particle density; Turbulence dissipation rate; Response surface modeling

Permalink: https://www.hzdr.de/publications/Publ-28382
Publ.-Id: 28382


On the surface wettability heterogeneities in fine particle separation technologies - inverse Gas Chromatography investigations and interface interaction studies

Rudolph, M.; Sygusch, J.

Fine particle separation is a challenging task and relies on a proper understanding of interfacial properties. In our research the focus lies on the process of flotation, which is a heterocoagulation separation method for fine particles in aqueous dispersions (size range approx. 5 µm < x <200 µm). It has been used in large extent for several decades and with billions of tons of particles processed per annum in the mining industry to separate valuable mineral particles from worthless ones. The main principle of separation is the particles' differences in wettability. This wettability is influenced by controlled selective adsorption of amphiphilic molecules rendering most typically the valuable containing minerals hydrophobic. Usually the particle property "wettability" is being quantified with a water contact angle. However, this value is not only difficult to assess for particles but furthermore through Young's equation a function of the surface free energy, which is a complex parameter as a result of various interatomic/intermolecular interactions. Using iGC we show how to characterize these complex wettability properties of particles assessing the heterogeneity of disperse and acid base specific surface free energies. These complex values are used in accordance to an approach by van Oss to formulate a new wettability parameter for flotation which is the specific free energy of interaction between a particle and a gas bubble immersed in water. We are presenting the general approach and results from various mineral collector systems and give insights to the boundary conditions and the general calculation scheme. In a recent trial we show the predictive power of the results. Furthermore we show how iGC can be put in context to other interaction investigations using flotability, contact angle measurements and colloidal probe atomic force microscopy.

  • Invited lecture (Conferences)
    1st European Symposium on Sorption Science, 05.-07.09.2018, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-28381
Publ.-Id: 28381


The Effect of Tin on the Formation and Properties of Pt/MgAl(Sn)Ox Catalysts for Dehydrogenation of Alkanes

Belskaya, O. B.; Stepanova, L. N.; Nizovskii, A. I.; Kalinkin, A. V.; Erenburg, S. B.; Trubina, S. V.; Kvashnina, K. O.; Leont’Eva, N. N.; Gulyaeva, T. I.; Trenikhin, M. V.; Bukhtiyarov, V. I.; Likholobov, V. A.

The MgAl(Sn) layered double hydroxides (LDH) with the atomic ratios Mg/(Al+Sn) = 3 and Sn/(Sn+Al) = 0, 0.002, 0.005, 0.01, 0.05, 0.1, 0.3, 0.5, 0.7, 1.0 were synthesized and the ratio Sn/(Sn+Al) ≤ 0.1 was shown to provide the formation of systems with uniform phase composition. Mixed oxides derived from LDH retain the high specific surface area of 150-200 m2/g and the basic properties when some aluminium atoms are replaced with tin. It was found that the Sn-containing mixed oxides are able to restore the layered structure during rehydration and intercalate the anion precursors of platinum into the interlayer space of the formed LDH.
The emerging platinum sites initiate the reduction of tin at temperatures below 723 K. TEM, EXAFS and XPS studies demonstrated that tin introduction in the support increases the dispersion of supported platinum. An extreme dependence of the activity of Pt/MgAl(Sn)Ox catalysts in propane and n-decane dehydrogenation on the tin content in the support was revealed. The active catalysts are characterized by the phase and elemental uniformity of the support, highly disperse state of Pt(0), and the absence of a noticeable amount of reduced tin and bimetallic particles.

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Permalink: https://www.hzdr.de/publications/Publ-28380
Publ.-Id: 28380


An investigation of the recovery and kinetics during the flotation of residual petroleum coke in lime calcination exhaust tailings

Vaziri Hassas, B.; Guven, O.; Hassanzadeh, A.

Flotation is one of the feasible separation methods suggested for recovery of petroleum coke from the tailings of lime calcination furnaces. In this study, analyses of ash content and calorific value of petroleum coke in lime calcination tailings were used to measure its floatability and product quality. In addition, seven most common flotation kinetics models were fitted to the obtained experimentalm data. Based on the maximum recovery, minimum ash content, and maximum calorific value of the flotation products, optimum dosages for collector (kerosene) and frother (MIBC) were found 30 g/t and 60 g/t, respectively. Regarding the flotation kinetic modeling and the obtained sum of squared errors (SSEs), Agar and Klimpell models were found to have the best and the poorest fits to the experimental data, respectively. Finally, it was concluded that new statistical concepts such as information criteria (IC) and non-linear generalized least squares estimation (NLGLSE) must be applied to the process of model selection owing to consideration of goodness of fit, complexity of a model and model consistency.

Keywords: Reagent optimization; flotation rate constant; flotation kinetic model; petroleum coke

Permalink: https://www.hzdr.de/publications/Publ-28379
Publ.-Id: 28379


Explaining metal zonation at the Lisheen deposit

Frenzel, M.; Burisch, M.; Röhner, M.; Gilbert, S.; Cook, N. J.; Ciobanu, C. C.; Güven, J.; Gutzmer, J.

  • Lecture (others)
    16th Freiberg Shortcourse in Economic Geology - "Zinc Deposits", 04.12.2018, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28378
Publ.-Id: 28378


Stratified and Segregated Flow Modelling - AIAD 2018

Höhne, T.

Today: Limits in simulating stratified & segregated two phase flow
Algebraic Interfacial Area Density Model (AIAD)
Free Surface Drag
Turbulence Damping
Sub-grid wave turbulence (SWT)
Verification and Validation is going on – more experimental data are required for the validation

Keywords: AIAD; Free Surface Drag; Sub-grid wave turbulence (SWT)

  • Lecture (Conference)
    16th Short Course “Multiphase Flow: Simulation,Experiment and Application", 13.-16.11.2018, Dresden, Deutschland
  • Contribution to proceedings
    16th Short Course “Multiphase Flow: Simulation,Experiment and Application, 13.-16.11.2018, Dresden, Deutschland
  • Poster
    16th Short Course “Multiphase Flow: Simulation,Experiment and Application, 13.-16.11.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28377
Publ.-Id: 28377


Spin-Wave Modes in Transition from a Thin Film to a Full Magnonic Crystal

Langer, M.; Gallardo, R. A.; Schneider, T.; Stienen, S.; Roldán-Molina, A.; Yuan, Y.; Lenz, K.; Lindner, J.; Landeros, P.; Fassbender, J.

Surface-modulated magnonic crystals are the natural link between continuous films with sinusoidal spin-wave eigenmodes and one-dimensional magnonic crystals composed of individual nanowires. Nevertheless, the transformation process of the spin-wave modes in this transition remains yet unclear. Here, spin-wave modes in their entire transition from a flat film to a ‘full’ (one-dimensional) magnonic crystal are studied by ferromagnetic resonance (FMR) and micromagnetic simulations. For this purpose, the surface of a pre-patterned thin permalloy film was sequentially ion milled resulting in hybrid structures, referred to as surface-modulated magnonic crystals, with increasing modulation depth. After each step, FMR measurements were carried out in backward-volume and Damon-Eshbach geometry. The evolution of each spin-wave resonance is studied together with the corresponding mode profile obtained by micromagnetic simulations. Simple rules describing the transition of the modes from the film to the modes of the full magnonic crystal are provided unraveling the complexity of spin-wave states in these hybrid systems.

Keywords: spin waves; ferromagnetic resonance; magnonic crystals; band structure; magnonics; thin films; magnetism

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Permalink: https://www.hzdr.de/publications/Publ-28375
Publ.-Id: 28375


Self-stabilizing exchange-mediated spin transport

Schneider, T.; Hill, D.; Kakay, A.; Lenz, K.; Lindner, J.; Faßbender, J.; Upadhyaya, P.; Liu, Y.; Wang, K.; Tserkovnyak, Y.; Krivorotov, I. N.; Barsukov, I.

Long-range spin transport in magnetic systems can be achieved by means of exchange-mediated spin textures with robust topological winding - a phenomenon referred to as spin superfluidity. Its experimental signatures have been discussed in antiferromagnets which are nearly free of dipolar interaction. In ferromagnets, which present with non-negligible dipole fields, however, realization of such spin transport has remained a challenge. Using micromagnetic simulations, we investigate exchange-mediated spin transport in extended thin ferromagnetic films. We uncover a two-fluidstate, in which the long-range spin transport by spin textures co-exists with and is stabilized by spin waves, as well as a soliton-screened spin transport regime at high spin injection biases. Both states are associated with distinct spin texture reconstructions near the spin injection region and sustain spin transport over large distances.

Keywords: Spin waves; superfluidity; bosons; micromagnetism; dipole-dipole interaction; Landau instability

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Permalink: https://www.hzdr.de/publications/Publ-28374
Publ.-Id: 28374


On the Chemistry and Diffusion of Hydrogen in the Interstitial Space of Layered Crystals h‐BN, MoS2, and Graphite

An, Y.; Kuc, A. B.; Petkov, P.; Lozada-Hidalgo, M.; Heine, T.

Recent experiments have demonstrated transport and separation of hydrogen isotopes in layered materials, such as hexagonal boron nitride and molybdenum disulphide. Here, based on first-principles calculations combined with well-tempered metadynamics simulations, we report the chemical interactions and mobility of protons (H+) and protium (H atoms) in the interstitial space of these layered materials. We show that both H+ and H can be transported between the layers of h-BN and MoS2 with low free energy barriers, while they are immobilized in graphite, in accordance with the experimental observations. In h-BN and MoS2, the transport mechanism involves a hopping process between the adjacent layers, which is assisted by the low- energy phonon shear modes. Defects present in MoS2 suppress the transport and act as traps for H species.

Permalink: https://www.hzdr.de/publications/Publ-28373
Publ.-Id: 28373


Functionalized DNA Origami Structures for Molecular Electronics

Bayrak, T.; Helmi, S.; Ye, J.; Martinez-Reyes, A.; Samano-Tirado, E.; Seidel, R.; Erbe, A.

The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance. The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.

  • Poster
    IHRS NanoNET Annual Workshop, 05.-07.09.2018, Bad Gottleuba, Germany

Permalink: https://www.hzdr.de/publications/Publ-28372
Publ.-Id: 28372


Functionalized DNA Origami Nanostructures for Molecular Electronics

Bayrak, T.; Ye, J.; Helmi, S.; Martinez-Reyes, A.; Samano, E.; Seidel, R.; Erbe, A.

The DNA origami method provides a programmable bottom-up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance . The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.

  • Poster
    CECAM/Psi-k research conference: BioMolecular Electronics (BIOMOLECTRO), 27.-31.08.2018, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-28371
Publ.-Id: 28371


Functionalized DNA Origami Nanostructures for Molecular Electronics

Bayrak, T.; Ye, J.; Helmi, S.; Martinez-Reyes, A.; Samano, E.; Seidel, R.; Erbe, A.

The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nanoelectronics and nanophotonics device fabrications.
This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanoMOLDS are used for the fabrication of nanoelectronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanoMOLDS and create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanoMOLD based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires showed metallic conductance. The other two wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.

  • Poster
    13th HZDR PhD Seminar, 05.-07.11.2018, Usti nad Labem, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-28370
Publ.-Id: 28370


Electrical transport study as a function of temperature on a C-shape gold nanowire templated by a DNA origami

Bayrak, T.; Martinez-Reyes, A.; Ruiz-Arce, D.; Kelling, J.; Samano, E.; Erbe, A.

Small DNA origami templates 90 nm x 70 nm DNA origami nanosheets with three functionalized sides holding a total of eight capture strands for decoration with gold nanoparticles were fabricated. Electroless gold growth is applied to selectively grow the gold nanoparticles until they merge into continuous nanowires. Finally, this work demonstrates the application of shape-controlled C-shaped gold wires as precisely tailored metal contacts to single, isolated nanowires to better understand the charge transport characteristics at different temperatures.

  • Lecture (Conference)
    DNA Mitteldeutschland, 24.05.2018, Leibniz IPHT Jena, Germany

Permalink: https://www.hzdr.de/publications/Publ-28369
Publ.-Id: 28369


DNA Origami templated assembly of metallic nanowires

Bayrak, T.; Erbe, A.

The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds1,2 and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance.1 The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.

  • Lecture (Conference)
    PhD Seminar HZDR, 07.05.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-28368
Publ.-Id: 28368


DNA origami sheet based C-shaped conducting nanowires

Bayrak, T.; Martinez-Reyes, A.; Ruiz-Arce, D.; Kelling, J.; Samano, E.; Erbe, A.

Small DNA origami templates 90 nm x 70 nm DNA origami nanosheets with three functionalized sides holding a total of eight capture strands for decoration with gold nanoparticles were fabricated. Electroless gold growth is applied to selectively grow the gold nanoparticles until they merge into continuous nanowires. Finally, this work demonstrates the application of shape-controlled C-shaped gold wires as precisely tailored metal contacts to single, isolated nanowires to better understand the charge transport characteristics at different temperatures.

  • Lecture (Conference)
    BAC Retreat, 25.06.2018, Rathen, Germany

Permalink: https://www.hzdr.de/publications/Publ-28367
Publ.-Id: 28367


Functionalized DNA Origami Nanostructures for Molecular Electronics

Bayrak, T.; Helmi, S.; Ye, J.; Kelling, J.; Schönherr, T.; Erbe, A.; Seidel, R.

The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nanoelectronics and nanophotonics device fabrications.
This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanoMOLDS are used for the fabrication of nanoelectronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanoMOLDS and create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanoMOLD based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires showed metallic conductance. The other two wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.

  • Poster
    DPG Meeting Berlin, 11.-16.03.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-28366
Publ.-Id: 28366


Functionalized DNA Origami Nanostructures for Molecular Electronics

Bayrak, T.; Helmi, S.; Ye, J.; Martinez-Reyes, A.; Samano-Tirado, E.; Seidel, R.; Erbe, A.

The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds1,2 and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance.1 The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.

  • Lecture (Conference)
    3rd Functional DNA Nanotechnology Workshop, 06.-08.06.2018, Rome, Italy

Permalink: https://www.hzdr.de/publications/Publ-28364
Publ.-Id: 28364


Thermal dependence of large scale freckle defect formation

Kao, A.; Shevchenko, N.; Alexandrakis, M.; Krastins, I.; Eckert, S.; Pericleous, K.

The fundamental mechanisms governing macroscopic freckle defect formation during directional solidification are studied experimentally in a Hele-Shaw cell for a low melting point Ga-25wt.%In alloy, and modelled numerically in 3D using a microscopic parallelised Cellular Automata lattice Boltzmann method. The size and distribution of freckles (long solute channels, or chimneys) is shown to be strongly dependent on the thermal profile of the casting, with flat, concave and convex isotherms being considered. For the flat isotherm case, no large-scale freckles form, while for concave or convex isotherms large freckles appear but in different locations. The freckle formation mechanism is as expected buoyancy-driven, but the chimney stability, its long-term endurance and its location, are shown to depend critically on the detailed convective transport through the inter-dendritic region. Flow is generated by curved isopleths of solute concentration. As solute density is different from that of the bulk fluid, gravity causes ‘uphill´ or ‘downhill’ lateral flow from the sample centre to the edges through the mush, feeding the freckle. An excellent agreement is obtained between the numerical model and real-time x-ray observations of a solidifying sample under strictly controlled temperature conditions.

Keywords: Freckle defect formation; Ga-In alloy; Convective transport

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Permalink: https://www.hzdr.de/publications/Publ-28363
Publ.-Id: 28363


Organische Chemie XV - Stereoselektive Reaktionen, Naturstoffsynthese, Syntheseplanung - Retrosynthese

Mamat, C.

Im ersten Teil dieses letzten Studienheftes wollen wir uns mit Reaktionen vertraut machen, bei denen aus einer prochiralen Verbindung selektiv chirale Verbindung gebildet wird, bei der ausschließlich eines der beiden Stereoisomere mit Chiralitätszentrum entsteht. Aus den Studienheften davor wissen wir schon, dass aus nichtchiralen Verbindungen mit prochiralem Zentrum meist Racemate entstehen. Faktoren, die zu einer Bevorzugung eines der beiden Stereoisomere führen, werden wir uns genau anschauen.
Im zweiten Teil wollen wir uns mit Retrosynthese und Syntheseplanung beschäftigen. Ausgehend von teils komplizierten Molekülen und Strukturen werden Sie sehen, wie durch eine gedankliche „Rückwärtsreaktion“ (Zerlegung in Bestandteile) ein Syntheseplan erstellt werden kann. Dazu wird das Zielmolekül immer weiter in seine Bestandteile, also hypotetische Ausgangsstoffe, zerlegt.

Keywords: Wittig-Reaktion; Walden-Umkehr; Auxiliar; Zerlegung; Totalsynthese

  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    44 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28362
Publ.-Id: 28362


Organische Chemie XIV - Metallorganische Verbindungen und Übergangsmetallkatalyse

Mamat, C.

Elementorganische Verbindungen sind uns schon ganz am Anfang dieses Studiums seit dem ersten Studienheft über den Weg gelaufen. Bisher haben wir uns auf Substanzen beschränkt, die Hauptgruppenmetalle wie Magnesium, Natrium oder Lithium beinhalten. Denken Sie dabei zum Beispiel an die Aldol-Reaktion. Aber auch ein typisches Nebengruppenelement, nämlich das Zink, haben wir uns angeschaut.
Für Sie ist wichtig zu wissen, welche Bindungsverhältnisse in diesen metallorganischen Verbindungen vorherrschen. Das betrifft insbesondere die Umpolung der Bindung des Kohlenstoffs, wenn er an Metallen gebunden ist im Vergleich zur Bindung von elektronegativeren Elementen, wie den Halogenen, Stickstoff, Sauerstoff oder auch Schwefel. Damit soll klarwerden, dass dieses Kohlenstoffatom dann carbanionisch reagiert.

Keywords: Grignard; Kreutzkupplung; Metallorganyle; Komplexe; Katalysatoren

  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    0045 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28361
Publ.-Id: 28361


Organische Chemie XIII - Umlagerungen und Elektrocyclische Reaktionen

Mamat, C.

Das Ziel des ersten Teils dieses Studienheftes besteht darin, ein Gefühl beziehungsweise Verständnis von Nebenreaktionen zu bekommen, die beispielsweise bei nucleophilen Substitutionsreaktionen oder Additionen und Eliminierungen auftreten. Diese Nebenreaktionen sind meist Umlagerungen, haben teilweise ihren eigenen Mechanismus und führen vielfach zu unerwarteten Produkten, wie wir schon in der Vergangenheit sehen konnten. Wir werden uns intensiv damit beschäftigen, ob und wie diese Umlagerungen beeinflusst werden können und welche Varianten es gibt.
Des Weiteren werden wir schauen, welche weiteren Umlagerungen existieren und welche Produkte zu erwarten sind. Am Ende werden wir einen Blick auf elektrocyclische Reaktionen werfen und sehen, dass durch deren Übergangszustände und Zwischenstufen stereoselektiv Produkte gebildet werden.

Keywords: Wasserstoffwanderung; Alkylgruppenwanderung; Claisen-Reaktion; Cope-Reaktion; Abbaureaktionen

  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    0043 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28360
Publ.-Id: 28360


Organische Chemie XII - Stereoisomerie

Mamat, C.

Nachdem wir uns in der Organischen Chemie I in der Hauptsache mit Stoffklassen, funktionellen Gruppen und wichtigen Reaktionen beschäftigt haben und in der Organischen Chemie II die Reaktionsmechanismen genau beleuchteten, wollen wir uns im dritten Teil mit speziellen Themen der organischen Chemie beschäftigen. In diesem Studienheft wollen wir uns einzig und allein mit der Anordnung der Atome in Molekülen und den damit verbundenen Besonderheiten dieser Moleküle beschäftigen. Doch warum brauchen wir das ganze Wissen über den exakten Aufbau der Moleküle? Es ist speziell für die Pharmazie und Biochemie von grundlegender Bedeutung, genau zu wissen, wie Moleküle aufgebaut sind. Denn mit exakt der gleichen Summenformel, selbst mit gleicher Aneinanderreihung der Atome können unterschiedliche Wirkungen auftreten.
Deshalb werden wir noch einmal genau beleuchten, was Isomere sind und welche Arten es gibt. Dann werden wir uns die Auswirkungen anschauen, die vier unterschiedliche Substituenten an einem Kohlenstoffatom haben. Wichtig ist, dass Sie verstehen, dass unterschiedliche Stoffe oder Verbindungen da sind, wenn Sie die Stellung (Anordnung) der Substituenten im Molekül „vertauschen“. Zudem sollten Sie mit dem Begriff Stereoisomerie sicher umgehen können und wissen, was für Isomere da existieren und was das für Folgen auf die Reaktivität des Moleküls hat. Darauf aufbauend finden wir Moleküle, in denen mehr als ein Chiralitätszentrum existiert. Welche Auswirkungen das auf die Eigenschaften des Moleküls hat, werden wir am Schluss sehen.

Keywords: Isomere; Enantiomere; prochiral; Chiralität

  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    0039 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28359
Publ.-Id: 28359


Symmetry Breaking of Azimuthal Magnetorotational Instability Caused by Thermal Boundary Conditions

Seilmayer, M.; Stefani, F.

The first evidence of azimuthal magnetorotaional instability was given some years ago by Seilmayer et al. (2014). A Taylor Couette Setup, filled with liquid metal, was exposed to magnetic field Bφ ~ r^ -1. The necessary current was supplied by a large frame of copper rods which caused a residual m=1 field disturbance. This imperfection caused a stationary dominant background flow. Since then, several changes took place to circumvent external asymmetries and influences. The main improvement was the symmetric current return path which eliminates the m=1 background flow and reduces stray fields. Now the AMRI wave is mainly located at the top of the cylinder, which is surprising since the theoretical prediction allows a symmetric wave with m=±1 configuration. However, the wave component from below is missing. Recent work indicate that thermal convection could be a possible source of symmetry breaking. We present experimental results which give evidence to the strong dependency on thermal boundary conditions which affect AMRI action in the volume.

Keywords: AMRI; MRI; Taylor Couette; magnetorotational instability

  • Poster
    MHD Days and GDRI Dynamo Meeting, 26.-28.11.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28358
Publ.-Id: 28358


Thallium pollution in China and removal technologies for waters: A review

Liu, J.; Luo, X.; Sun, Y.; Tsang, D. C. W.; Qi, J.; Zhang, W.; Li, N.; Yin, M.; Wang, J.; Lippold, H.; Chen, Y.; Sheng, G.

Thallium (Tl) is a typical toxic metal, which poses a great threat to human health through drinking water and the food chain (biomagnification). China has rich Tl-bearing mineral resources, which have been extensively explored and utilized, leading to release of large amounts of Tl into the environment. However, research on Tl pollution and removal techniques is relatively limited, because Tl has not been listed within the scope of environmental monitoring in China for several decades. This paper reviewed Tl pollution in wastewater arising from various industries in China, as well as the latest available methods for treating Tl-containing industrial wastewater, in order to give an outlook on effective technologies for controlling Tl pollution. Conventional physical and chemical treatment technologies are efficient at removing trace amounts of Tl, but it proved to be difficult to achieve the stringent environmental standard (≤0.1–5 μg/L) cost-effectively. Adsorption by using newly developed nanomaterials, and metal oxide modified polymer materials and microbial fuel cells are highly promising and expected to become next-generation technologies for remediation of Tl pollution. With the potential for greater Tl contamination in the environment under accelerated growth of industrialization, researches based on lab-scale implementation of such promising treatment technologies should be further expanded to pilot and industrial scale, ensuring environmental protection and the safety of drinking water for sustainable development. Comprehensive insights into experiences of Tl pollution in China and in-depth perspectives on new frontier technologies of Tl removal from wastewaters will also benefit other nations/regions worldwide, which are susceptible to high exposure to Tl likewise.

Keywords: Thallium pollution; Industrial wastewater treatment; Anthropogenic source; Nanomaterials

Permalink: https://www.hzdr.de/publications/Publ-28357
Publ.-Id: 28357


High contamination risks of thallium and associated metal(loid)s in fluvial sediments from a steel-making area and implications for environmental management

Liu, J.; Ren, S.; Zhou, Y.; Tsang, D. C. W.; Lippold, H.; Wang, J.; Yin, M.; Xiao, T.; Luo, X.; Chen, Y.

Thallium (Tl) is an uncommon toxic element, with an even greater toxicity than that of As, Hg and Cd. Steel-making industry has been identified as an emerging new significant source of Tl contamination in China. This paper presents a pilot investigation of the contamination and geochemical transfer of Tl and associated metal(loid)s in river sediments affected by long-term waste discharge from the steel-making industry. The results uncovered an overall Tl contamination (1.96 ± 0.42 mg/kg) across a sediment profile of approximately 1.5 m in length, even 10 km downstream the steel plant. Highly elevated contents of Pb, Cu, Cd, Zn and Sb were found in the fluvial sediments, displaying strong positive correlations with Tl contents. Elevated levels of geochemically mobile Tl as well as Cd, Zn, Cu and Pb occurred in the fluvial sediments, signifying anthropogenic imprints from steel production activities at high temperature. Levels of contamination and ecological risk were calculated to be moderate to considerable for Tl, Cu, Zn and high to very high for Cd, Pb, Sb. The results highlight that there is a great challenge in view of potentially considerable Tl pollution due to continuous massive steel production in many other parts of China. It is high time to initiate process-based management of Tl contamination control for the ambient aquifer system in the steel-making area.

Keywords: Thallium; Sediment; Steel-making plant; Ecological risk; Geochemical fractionation

Permalink: https://www.hzdr.de/publications/Publ-28356
Publ.-Id: 28356


Fine grinding characteristics of a cassiterite-bearing skarn ore

Buchmann, M.; Leißner, T.; Kern, M.; Schach, E.; Tolosana-Delgado, R.; Rudolph, M.; Gutzmer, J.; Peuker, U. A.

The grinding characteristic of a cassiterite-bearing skarn ore was investigated for the fine particle size range using an agitated ball mill. The applicability of Mineral Liberation Analyzer was investigated for the fine particle range. The appropriate liberation of cassiterite was determined with the help of tangible parameters such as the degree and coefficient of liberation and grade-recovery diagrams. The liberation of cassiterite was found to be in a satisfying range for downstream upgrading. A more etailed analysis of the liberation characteristics of the potential valuables together with a better understanding of the breakage characteristics of the gangue minerals will help to optimize the operation of the subsequent upgrading process. Therefore, the breakage behavior of the most important gangue minerals was analyzed. The effect of selectivity in breakage for the different minerals became visible.
A clear spreading for the mineral recovery versus size class indicated a mineral specific accumulation during milling. These trends lead to the assumption that the separation of the minerals into different particle size classes can be optimized by applying a specific energy input.

  • Contribution to proceedings
    European Mineral Processing and Recycling Congress (EMPRC) 2018, 22.06.2018, Essen, Germany

Permalink: https://www.hzdr.de/publications/Publ-28355
Publ.-Id: 28355


Evaluation of Magnetic Separation Efficiency on a Cassiterite-Bearing Skarn Ore by Means of Integrative SEM-Based Image and XRF–XRD Data Analysis

Buchmann, M.; Schach, E.; Tolosana-Delgado, R.; Leißner, T.; Astoveza, J.; Kern, M.; Möckel, R.; Ebert, D.; Rudolph, M.; van den Boogaart, K. G.

Image analysis data obtained from scanning electron microscopy provided data for a detailed evaluation of the separation efficiency for various processes involving the beneficiation of particulate materials. A dry magnetic separation by a drum type magnetic separator served as a case study to visualize effects of processing of a skarn ore with a high content of cassiterite as ore mineral (~4 wt%). For this material, iron oxides and silicates are the main gangue mineral groups. Based on the obtained data, partition curves were generated with the help of local regression.
From the partition curves, the separation efficiency was evaluated and the relevant particle properties deduced. A detailed analysis of the bias of the quantitative mineralogical data is presented. This bias was monitored and further analyzed in detail. Thorough analysis of feed and products of magnetic separation enabled identification of the most important factors that control losses of cassiterite to the magnetic product, namely the association with iron oxides and particle sizes below ~40 µm.
The introduced methodology is a general approach applicable for the optimization of different separation processes and is not limited to the presented case study.

Keywords: SEM-based image analysis; MLA (Mineral Liberation Analyzer); magnetic separation; cassiterite; partition curve; local regression

Permalink: https://www.hzdr.de/publications/Publ-28354
Publ.-Id: 28354


Optimal sensor selection for sensor-based sorting based on automated mineralogy data

Kern, M.; Tusa, L.; Leißner, T.; van den Boogaart, K. G.; Gutzmer, J.

Assessing the success of sensor-based sorting in the raw materials industry currently requires time-consuming and expensive empirical test work. In this contribution we illustrate the prospects of successful sensor selection based on data acquired by scanning electron microscopy-based image analysis. Quantitative mineralogical and textural data from more than 100 thin sections were taken to capture mineralogical and textural variability of two different ore types from the Hammerlein Sn-In-Zn deposit, Germany. Parameters such as mineral grain sizes distribution, modal mineralogy, mineral area and mineral density distribution were used to simulate the prospects of sensor-based sorting using different sensors. The results illustrate that the abundance of rock-forming chlorite and/or density anomalies may well be used as proxies for the abundance of cassiterite, the main ore mineral.
This suggests that sorting of the Hammerlein ore may well be achieved by either using a short-wavelength infrared detector - to quantify the abundance of chlorite - or a dual-energy X-ray transmission detector to determine the abundance of cassiterite. Empirical tests conducted using commercially available short-wave infrared and dual-energy X-ray transmission sensor systems are in excellent agreement with simulation-based predictions and confirm the potential of the novel approach introduced here.

Keywords: Sensor-Based Sorting; Dual Energy X-ray Transmission; Short-Wave Infrared; Spectroscopy; Automated Mineralogy; Cassiterite; Predictive Geometallurgy

Permalink: https://www.hzdr.de/publications/Publ-28353
Publ.-Id: 28353


The inherent link between ore formation and geometallurgy as documented by complex tin mineralization at the Hämmerlein deposit (Erzgebirge, Germany)

Kern, M.; Kästner, J.; Tolosana-Delgado, R.; Jeske, T.; Gutzmer, J.

A comprehensive quantitative mineralogical study on the Hämmerlein tin deposit in the Erzgebirge, Germany, not only yields insights into the genesis of Sn mineralization but also provides also important clues for beneficiation. The lithological units of the skarn and greisen deposit show significant differences in modal mineralogy and Sn deportment. These systematic differences are attributed to several stages of ore formation. Of greatest significance is a paragenetically late cassiterite-chlorite-fluorite-sulfide assemblage. This assemblage replaces pre-existing skarn lithologies and also forms stockwork mineralization in greisen-type ores developed at the expense of mica schist that surrounds the skarn. The co-genetic formation of the cassiterite-chlorite-fluorite-sulfide assemblage is captured by the mineral association parameter—a parameter that can be easily quantified from data acquired during automated mineralogy studies. To document the preferred mineral association, a ratio is introduced that illustrates how closely cassiterite—the only Sn mineral of economic relevance—is associated with chlorite, fluorite, and sulfides. This socalled MAMA ratio illustrates the strongly preferred association between cassiterite and chlorite. The results also illustrate that the abundance of rock-forming chlorite may be used as a proxy for the abundance of the much less common cassiterite. This proxy is well-suited to sort ore from poorly mineralized/unmineralized rock fragments early during the beneficiation process. Such separation may well be achieved by using a short wave infrared detector that is already deployed in commercially available sorting equipment. The case study illustrates the inherent link between the processes responsible for ore genesis, the definition of geometallurgical domains, and the selection of suitable beneficiation strategies.

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Permalink: https://www.hzdr.de/publications/Publ-28351
Publ.-Id: 28351


Reconfigurable spin-wave non-reciprocity induced by dipolar interaction in a coupled ferromagnetic bilayer

Gallardo, R. A.; Schneider, T.; Chaurasiya, A. K.; Oelschlägel, A.; Arekapudi, S. S. P. K.; Roldáan-Molina, A.; Hübner, R.; Lenz, K.; Barman, A.; Fassbender, J.; Lindner, J.; Hellwig, O.; Landeros, P.

Non-reciprocity of wave phenomena describes the situation where wave dispersion depends on the sign of the wave-vector, i.e., counter-propagating waves exhibit di↵erent wavelengths for the same frequency. Such behavior has been recently observed in heavy-metal/ferromagnetic interfaces with Dzyaloshinskii-Moriya coupling, and has also been known for coupled magnetic bilayers, where non-reciprocity is enhanced when the two layers are antiparallel aligned. Besides the conventional uses of spin-waves, non-reciprocity adds further functionalities, such as its potential applications in communications technologies and logical operations. In the current manuscript, we thus examine the spin-wave non-reciprocity induced by dipolar interactions in a coupled bilayer consisting of two ferromagnetic layers separated by a non-magnetic spacer. We derive an easy-to-use formula to estimate the frequency di↵erence provided by the non-reciprocity, which allows for choosing an optimal system in order to maximize the e↵ect. For small wave-numbers, non-reciprocity scales linearly, while for larger wave-vectors the non-reciprocity behaves non-monotonically, with a well-defined maximum. The study is carried out by means of analytical calculations that are complemented by micromagnetic simulations. Furthermore, we confirmed our model by experimental investigation of the spin-wave dispersion in a prototype antiparallel-coupled bilayer system. Since the relative magnetic orientation can be controlled through a bias field, the magnon non-reciprocity can be then turned on and o↵, which lends an important functionality to the coupled ferromagnetic bilayers.

Keywords: non-reciprocity; spin waves; ferromagnetic resonance; Brillouin Light Scattering; magnetism; Dzyaloshinskii-Moriya interaction; dispersion relation

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Permalink: https://www.hzdr.de/publications/Publ-28349
Publ.-Id: 28349


Synthese von deuterierten Oxocortisolderivaten

Hocke, V.

Ziel dieser Masterarbeit war die Synthese der Steroidderivate 18-Oxocortisol (8a) und dessen deuteriertes Analogon 1,2-2H2-18-Oxocortisol (8b). Die Darstellung erfolgte ausgehend vom strukturell ähnlichen Prednisolon (1). Dazu mussten zunächst orthogonale Schutzgruppen eingeführt werden, um selektiv Modifizierungen an der Steroidstruktur vornehmen zu können. Im Anschluss musste die 18-Methylgruppe funktionalisiert werden um die Einführung der Aldehydfunktion zu ermöglichen. Nach der darauffolgenden Entschützung sollte Derivat 7 erhalten werden, das sich von 8a und 8b lediglich in der C=C-Doppelbindung zwischen den Kohlenstoffatomen C-1 und C-2 unterschiedet und durch selektive Hydrierung oder Deuterierung dieser zu den Zielverbindungen umgesetzt werden kann.

Keywords: 18-Oxocortisol; Deuterium

  • Master thesis
    HTW Dresden, 2018
    Mentor: Dr. habil. Constantin Mamat
    0063 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28348
Publ.-Id: 28348


Process Analytical Techniques

Hampel, U.

The lecture gives an introduction to modern process analytical techniques in the industry and research.

Keywords: process analytical techniques

  • Invited lecture (Conferences)
    TOMOCON 1st Summer School, 26.-28.09.2018, Lublin, Poland

Permalink: https://www.hzdr.de/publications/Publ-28347
Publ.-Id: 28347


High-Resolution Flow Measurement Techniques for the Generation of Validation Data in Nuclear Thermal Hydraulics Experiments

Hampel, U.

The past years have seen a tremendous increase in computational power and hence a trend to employ more and more advanced numerical tools for the analysis of nuclear thermal hydraulics. Primary applications are accident analyses as well as safety assessment for new reactor systems and prominent directions are 3D computational multiphase fluid dynamics, coupled codes, and advanced BEPU analyses. While years ago it was believed that one day such tools may be able to replace experiments fully or in part, it is meanwhile commonly accepted, that a focus must be given on validation experiments for single effect problems and that such validation experiments should be preferably at original system t/h conditions to account for difficult upscaling conditions, and that such experiments need new instrumentation in order to get CFD grade data. The latter means field quantities of phase fraction, velocity and temperature at high spatial and temporal resolution.
The lecture gives an in-depth overview over novel field measuring techniques for nuclear thermal hydraulics experiments. We will briefly touch the field of distributed sensors for phase fraction, temperature and velocity and then dive into the field of advanced imaging techniques. We will discuss the application of well-known imaging techniques, such as high speed videometry, PIV and IR thermography and then come to computed tomography techniques, which are very useful to study multiphase problems. The methodological description of the basic physics and technology will be accompanied by application examples in nuclear safety research being pursued at the TOPFLOW facility at Helmholtz-Zentrum Dresden-Rossendorf.

Keywords: Flow measurement; multiphase flow; reactor safety; nuclear thermal hydraulics; tomography

  • Invited lecture (Conferences)
    The Frédéric Joliot / Otto Hahn Summer School on Nuclear Reactors "Maximizing the Benefits of Experiments for the Simulation, Design and Analysis of Reactors", 22.-31.08.2018, Aix en Provence, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-28346
Publ.-Id: 28346


Recent developments and future trends in tomographic imaging for multiphase flows

Hampel, U.

The presentation gives a overview over recent activities in the field of tomographic imaging for multiphase flows.

Keywords: Multiphase flow; imaging techniques; process tomography

  • Invited lecture (Conferences)
    International Workshop on Multiphase Flow Imaging and Measurement, 13.-14.08.2018, Tianjin, China

Permalink: https://www.hzdr.de/publications/Publ-28345
Publ.-Id: 28345


TOMOCON: A Marie Skłodowska-Curie European Training Network on Tomography-based Control in Industrial Processes

Hampel, U.; Wondrak, T.; Fjeld, M.; Mudde, R.; Portela, L. M.; Kenjeres, S.; Legendre, D.; Link, G.; Koiranen, T.; Hlava, J.; Babout, L.; Jackowska-Strumiłło, L.; Soleimani, M.; Vauhkonen, M.; Lähivaara, T.; Rymarczyk, T.; Trepte, M.; Voutilainen, A.; Rodriguez, M.; Bos, J.; Betz, S.; Hysky, J.; Pennerstorfer, P.; Goldammer, M.; Matten, C.; Hoffmann, R.; Gingras, J.-P.; van der Plas, D.; Veenstra, P.; Nurmi, J.; Pudack, C.; Da Silva, M. J.

The European Doctoral Training Network “Smart Tomographic Sensors for Advanced Industrial Process Control (TOMOCON)” gathers academic and industrial partners from different sectors with the mission to develop new fundamentals and technological solutions of advanced industrial control by tomographic sensors. It has received funding by the EU under the Marie Skłodowska-Curie scheme as an Innovative Training Network. It runs from September 2018 to August 2022 with 15 Early Stage Researchers, who are working as PhD students in 10 different European academic institutions. Within their research projects the doctoral students receive an extensive training in various fields of engineering and natural sciences being carried out in the frame of so called secondments at different industrial and academic partners as well as via three dedicated Summer Schools. The network is further supported by an Advisory Board with members from leading institutions in the field of process tomography.

Keywords: Marie Skłodowska-Curie Innovative Training Network; Process Tomography; Process Control; Process Modelling; Doctoral Education and Training

  • Lecture (Conference)
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK
  • Open Access Logo Contribution to proceedings
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK
    Proceeding of the 9th World Congress on Industrial Process Tomography

Permalink: https://www.hzdr.de/publications/Publ-28344
Publ.-Id: 28344


Simulation of the transient behavior of tubular solid oxide electrolyzer cells under fast load variations

Fogel, S.; Kryk, H.; Hampel, U.

Solid oxide electrolyzer cells pose a promising technology for the production of hydrogen gained from renewables, such as wind and PV. Due to the fluctuating nature of these sources, the transient behavior of SOEC under various load cases plays a crucial role in terms of their long-time stability, degradation behavior, conversion efficiency and application. This study presents a dynamic, 2D-FEM model of a single tubular SOEC. The transient operational behavior of the cell under fast load variations and different flow configurations is assessed based on the conducted simulations.

Keywords: Tubular SOEC; Load variation; Dynamic simulation; Proton conducting SOEC; Fast transient response

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Permalink: https://www.hzdr.de/publications/Publ-28343
Publ.-Id: 28343


Leaching of U(VI) and Cm(III) doped calcium (aluminum) silicate hydrate gel (C-(A)-S-H) and tobermorite in saline brines

Wolter, J. M.; Schmeide, K.; Huittinen, N.; Bok, F.; Weiss, S.; Brendler, V.; Stumpf, T.

To evaluate the retention potential of concrete inside a nuclear waste repository for actinides under saline and hyperalkaline conditions, leaching experiments with actinide doped cementitious phases were performed in repository-relevant brines. Therefore, U(VI) and Cm(III) doped calcium silicate hydrate (C-S-H) phases with different calcium-to-silicon (C/S) ratios (1.0−2.0) were synthesized directly in presence of either U(VI) or Cm(III) and characterized by time-resolved laser-induced luminescence spectroscopy (TRLFS), infrared (IR) spectroscopy, powder X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The time-dependent release of Ca, Si, U or Cm from CSH phases into brines that contained either 2.5 M NaCl, 2.5 M NaCl/0.02 M Na₂;SO₄, 2.5 M NaCl/0.02 M NaHCO₃ or 0.02 M NaHCO₃ for U(VI) doped CSH phases or 2.5 M NaCl/0.02 M NaHCO₃ or 0.02 M NaHCO₃ for Cm(III) doped CSH phases was monitored in batch leaching experiments for 30 to 60 days. Subsequently, leaching induced changes of the C-S-H structure and of the U(VI) or Cm(III) coordination environment were investigated with TRLFS, IR spectroscopy and XRD. Results indicated that the U(VI) retention by C-S-H phases is maintained in the presence of NaCl rich solutions due to the formation of uranophane [1]. The presence of carbonate in saline leaching solutions increased the U(VI) mobility due to formation of Ca₂UO₂(CO₃)₃(aq) at moderate alkaline pH values [1]. Furthermore, an influence of the secondary CaCO₃ phases calcite, vaterite and aragonite was detected. Calcite contributed to the U(VI) retention which was shown with TRLFS [1]. The binding study of Cm(III) incorporated into C-S-H gel revealed at least two Cm(III) species: (i) Cm(III) substituted against Ca2+ from the C-S-H interlayer and (ii) Cm(III) incorporated in the polyhedral CaO plane of the C-S-H structure. Additionally, a luminescence line narrowing effect was observed indicating variations of the local surrounding of Cm(III) in C-S-H gel. Leaching experiments showed that Cm(III) is not mobilized by carbonate but becomes partially incorporated into secondary CaCO₃ phases. Recently, we started to investigate the Al and U(VI) incorporation into C-S-H phases at different Al/Si ratios (0.025−0.2) and synthesis temperatures (25°C or 200°C). The obtained phases were investigated with ² ⁷Al NMR, TRLFS, XRD and Raman microscopy. First results indicated an influence of the Al starting material and synthesis temperature on the Al incorporation.

Keywords: C-S-H; Aluminum; TRLFS; XRD; Raman; IR; Leaching; Saline; Carbonate

  • Contribution to proceedings
    5th International Workshop on Mechanisms and Modelling of Waste/Cement interactions, 25.-27.03.2019, Karlsruhe, Deutschland
    Proceedings of the 5th International Workshop on Mechanisms and Modelling of Waste/Cement interactions
  • Poster
    5th International Workshop on Mechanisms and Modelling of Waste/Cement interactions, 25.-27.03.2019, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28342
Publ.-Id: 28342


Lattice relaxation effects of the spin-ice Dy2Ti2O7

Stoeter, T.; Nomura, T.; Granovsky, S.; Doerr, M.; Petrenko, O. A.; Balakrishnan, G.; Zherlitsyn, S.; Wosnitza, J.

Dy2Ti2O and Ho2Ti2O7 have attracted enormous scientific interest because of the unusual spin-ice ground state and exotic excitations – magnetic monopoles. In this work, we investigated how the lattice reacted to the change of the monopole density from the spin-ice through the Kagome ice to the saturated monopole phase and whether the very slow monopole dynamics predicted in theory were also detectable in lattice effects. We have performed magnetostriction and thermal-expansion measurements with a capacitive dilatometer on Dy2Ti2O7 at temperatures down to 0.28 K to explore the lattice effects in the different regimes: Indeed, we have observed a field-dependent lattice anomaly and have found lattice relaxation effects which could be related to previously proposed monopole dynamics. This research has been supported by the DFG within project C01 of SFB 1143.

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28341
Publ.-Id: 28341


Magnetic ground state of the cubic perovskite Ba3NiNb2O9

Yamamoto, S.; Aslan Cansever, G.; Gottschall, T.; Uhlarz, M.; Blum, C. G. F.; Wolter-Giraud, A.; Aswartham, S.; Wurmehl, S.; Herrmannsdörfer, T.; Seiro, S.

We investigated the magnetic spin-1 perovskite Ba3NiNb2O9 by means of complex ac susceptibility measurements at extreme sample conditions. Ba3NiNb2O9 with cubic perovskite structure (Pm-3m) has a random occupation of Nb(66 %)/Ni(33 %) at the center of the cubic perovskite unit cell. Different from the isostoichiometric sister compound, Ba3NiNb2O9 with P-3m1 structure which shows both uud-spin configuration and multiferroicity, the magnetic properties of the investigated system have not been studied below 2 K yet. For our single crystals, we observe a spin freezing transition at around 0.7 K. Furthermore, the peak of 𝜒’ is suppressed by applying an external dc field of 200 mT and 𝜒” shows a sudden onset near the freezing temperature.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28340
Publ.-Id: 28340


Thermal and thermal-Hall conductivity study of SrCu2(BO3)2

Arsenijevic, S.; Dabkowska, H.; Gaulin, B.; Stern, R.; Wosnitza, J.

We present measurements of the thermal and the thermal-Hall conductivity as a function of temperature and magnetic field in the twodimensional dimer spin system SrCu2(BO3)2. The thermal conductivity in zero magnetic field shows a pronounced peak around 4 K which is ascribed to a spin-gap opening. The low-temperature maximum is strongly suppressed by the application of magnetic field. This result implies that the majority of heat is conducted by phonons which interact with the magnetic excitations. Furthermore, a theoretical study predicted a strong thermal Hall signature due to anisotropies originating from the Dzyaloshinskii-Moriya interactions which lead to a topological character of triplon excitations [1]. Our detailed experimental investigation did not reveal such effect disproving the existence of topological transitions in the triplon band structure.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28339
Publ.-Id: 28339


Inverted hysteresis within the antiferromagnetic all-in-allout state of the pyrochlore Nd2Hf2O7

Opherden, L.; Bilitewski, T.; Hornung, J.; Herrmannsdörfer, T.; Samartzis, A.; Islam, A. T. M. N.; Anand, V. K.; Lake, B.; Moessner, R.; Wosnitza, J.

We report the observation of an anisotropic and inverted hysteresis loop in the antiferromagnetic all-in-all-out ordered phase of Nd2Hf2O7 having a negative remnant magnetization. The hysteresis emerges once exceeding a characteristic magnetic-field strength 𝐻(𝑇) below the Neél temperature. The very unusual appearance of a negative remnant magnetization is observed for a field parallel to the [111] and [110] direction. However, for field parallel to [001] no hysteresis can be seen. For this orientation the projection of the field onto all four local spin directions is equal and, hence, both realizations of the all-in-all-out state gaining equal Zeeman energy through a canting of their spins. We show further, that the underlying all-in-all-out phase is established in Nd2Hf2O7 for temperatures below 𝑇𝑁 = 0.48 K and persists up to fields of 0.27 T. We account for the inverted hysteresis in terms of a theory of uncompensated domain-wall spins of spherical Domains forming inside a fully polarized single-domain state.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28338
Publ.-Id: 28338


Electronic structure of the B20 compound CrGe

Klotz, J.; Götze, K.; Bruin, J.; Geibel, C.; Weber, K.; Schmidt, M.; Rosner, H.; Wosnitza, J.

CrGe is a nonmagnetic transition-metal germanide with the B20 noncentrosymmetric cubic structure. In contrast, the isostructural MnGe and FeGe both show a helical spin order. We present dHvA-effect data on CrGe that were obtained employing capacitive torque Magnetometers in a 18 T/30 mK and a 33 T/340 mK system. In combination with our fplo calculations, we provide a detailed picture of the Fermisurface topology of CrGe. Furthermore, by comparing the calculated band structures of CrGe and MnGe, we discuss possible reasons for the absence of magnetic order in CrGe. Finally, our calculations indicate that substituting Ge by As or Sn will not lead to magnetic order.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28337
Publ.-Id: 28337


Reversibility of minor hysteresis loops in magnetocaloric Heusler alloys

Gottschall, T.; Stern-Taulats, E.; Manosa, L.; Planes, A.; Skokov, K. P.; Gutfleisch, O.; Skourski, Y.; Wosnitza, J.

The unavoidable existence of thermal hysteresis in these magnetocaloric materials is one of the central challenges limiting their implementation in cooling devices. Transforming the material in minor loops of the thermal hysteresis, however, allows achieving significant reversible effects even when the hysteresis is relatively large. In this work, we focus on the magnetocaloric properties of Heusler alloys under cycling. We compare thermometric measurements of the adiabatic temperature change in low magnetic fields and pulsed field experiments with calorimetric measurements of the isothermal entropy change when moving in minor hysteresis loops driven by magnetic fields [1, 2].

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berline, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28336
Publ.-Id: 28336


Exploring the Quantum Limit of Weyl semimetal candidates

Förster, T.; Klotz, J.; Wosnitza, J.; Shekhar, C.; Yan, B.; Felser, C.

Non-centrosymmetric transition-metal mono-pnictides such as NbAs, NbP and TaAs attracted a lot of attention because their bandstructures show linear non-degenerate band crossings, dubbed Weyl nodes [1,2]. Additionally, for certain magnetic-field orientations, the highest de Haas-van Alphen frequencies observed are smaller than 50 T. For that reason, all bands are expected to be in the quantum limit at fields easily reachable by pulsed magnetic fields. Thus, these semimetals constitute an ideal playground to study the quantum limit by electric transport and magnetic-torque measurements. Our first results for NbP show an unexpected linear increase in magnetic-torque measurements. In our contribution we show the results of our magnetic-torque measurements on NbP, NbAs, TaP and TaAs in pulsed fields up to 70 T.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28335
Publ.-Id: 28335


NMR of the two-dimensional 𝑆 = 1/2 Heisenberg antiferromagnet CuPOF

Dmytriieva, D.; Zhang, Z. T.; Uhlarz, M.; Landee, C. P.; Wosnitza, J.; Kühne, M.

The metal-organic compound [Cu(pz)2(2-OHpy)2](PF6)2 (CuPOF) is a molecular-based analog of the two-dimensional quantum 𝑆 = 1/2 Heisenberg antiferromagnet (2D QHAF) with well-isolated Cu(pz) layers and a very low 𝑘𝐵𝑇𝑁/𝐽 = 0.21 ratio (𝐽/𝑘𝐵 = 6.8 K, 𝑇𝑁 = 1.38 K). We present a focus study of the low-temperature phase transition to long-range order performed via 1H and 31P nuclear magnetic resonance (NMR), as well as high-field magnetometry. A low-temperature Minimum of the temperature-dependent local and uniform magnetizations at 𝑇𝑚𝑖𝑛 indicates a presence of the magnetic order. Within the ordered state, a splitting of the 1H NMR spectra reveals commensurate AF order, presumably of checkerboard type. The phase transition, manifested as a sharp maximum of the temperature-dependent 31P nuclear spin-lattice relaxation rate 1/𝑇1, occurs at temperatures slightly lower than 𝑇𝑚𝑖𝑛, indicating an easy-plane anisotropy as well as a crossover between isotropic and XY behavior.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28334
Publ.-Id: 28334


Exploring the magnetic phase diagram of a metal-organic S = 1 triangular spin system.

Chattopadhyay, S.; Herrmannsdörfer, T.; Kanungo, S.; Zvyagin, S.; Uhlarz, M.; Manna, K.; Schnelle, W.; Sannigrahi, J.; Wosnitza, J.; Patra, R.

We report on magnetic properties of a novel metal-organic S = 1 antiferromagnetic triangular spin compound with isolated Ni2+ triangles entitled as BHAP-Ni3. Specific heat measurements reflect an onset of magnetic correlation at low temperatures without any long-range order down to 300 mK, indicating the presence of an unusual magnetic ground state. ESR measurements performed at 1.5 K advocate this ground state to be a gapped one. Field-dependent magnetization measured on the single crystal shows anisotropic behavior with field applied parallel and perpendicular to the triangle plane. However, a clear plateau-like region is seen in both directions above 8 T which corresponds to half of the fully polarized value of Ni2+ moment. The presence of such half-magnetization plateau is quite unusual in the family of triangular magnets. High-field magnetization measurements using pulsed magnet show another field-induced plateau above 30 T corresponding to the fully polarized state of S = 1 triangles.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28333
Publ.-Id: 28333


High-field ESR studies of the honeycomb-lattice material 𝛼-RuCl3

Ponomaryov, A. N.; Schulze, E.; Wosnitza, J.; Lampen-Kelley, P.; Banerjee, A.; Yan, J. Q.; Bridges, C. A.; Mandrus, D. G.; Nagler, S. E.; Kolezhuk, A. K.; Zvyagin, S.

We present high-field electron spin resonance (ESR) studies of the honeycomb-lattice material 𝛼-RuCl3, a prime candidate to exhibit Kitaev physics. Two modes of antiferromagnetic resonance were detected in the zigzag ordered phase, with magnetic field applied in the 𝑎𝑏 plane. A very rich excitation spectrum was observed in the field-induced Quantum paramagnetic phase. The obtained data are compared with results of recent numerical calculations, strongly suggesting a very unconventional multiparticle character of the spin dynamics in 𝛼-RuCl3. The frequency-field diagram of the lowest-energy ESR mode is found consistent with the behavior of the field-induced energy gap, revealed by thermodynamic measurements. This work was supported by DFG (project ZV 6/2-2).

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28332
Publ.-Id: 28332


A brief discussion of the magnetocaloric effect in thin films of manganite doped with chromium.

Campillo, G.; Figueroa, A. I.; Arnache, O.; Osorio, J.; Marín Ramírez, J. M.; Fallarino, L.

In this work we report on the magnetocaloric effect of La2/3Ca1/3MnO3 (LCMO) and La2/3Ca1/3Mn0.94Cr0.06O3 (LCMCrO) manganite thin films grown by DC magnetron sputtering on LaAlO3 (100) substrates. X-ray diffraction shows that both doped and undoped films crystallize in the orthorhombic structure. Magnetic measurements show a decrease in both the Curie temperature, TC, and the saturation magnetization, MS, for the LCMCrO sample. The change in the magnetic entropy (deltaSm) was extracted from hysteresis loops at different temperatures around the ferromagnetic to paramagnetic transition, displaying a maximum of entropy change (deltaSm)max near TC in both films. Moreover, a shift in (deltaSm)max toward temperatures above TC with increasing magnetic field and a broadening of the entropy change curve were observed. Results of refrigeration cooling power show a lower efficiency for LCMCrO. In order to obtain a local insight into the magnetic interactions of these films, measurements of X-ray absorption spectroscopy and X-ray magnetic circular dichroism (XMCD) were performed. XMCD suggests that an antiferromagnetic coupling between Mn4+ - Mn3+ is favored with Cr3+ incorporation, which reduces the Mn L2,3 XMCD signal and results in a decrease of MS and (deltaSm)max in LCMCrO films.

Keywords: Magnetocaloric effect; epitaxial La2/3Ca1/3MnO3 (LCMO) thin films; epitaxial La2/3Ca1/3Mn0.94Cr0.06O3 (LCMCrO) thin films

  • Open Access Logo Contribution to proceedings
    VI Congreso Nacional de Ingeniería Física, 22.-26.10.2018, Bucaramanga, Colombia
    Journal of Physics: Conference Series (JPCS).: IOP
    DOI: 10.1088/1742-6596/1247/1/012013

Permalink: https://www.hzdr.de/publications/Publ-28331
Publ.-Id: 28331


Magnetoelastic phenomena in antiferromagnetic uranium intermetallics: The UAu2Si2 case

Valiska, M.; Saito, H.; Yanagisawa, T.; Tabata, C.; Amitsuka, H.; Uhlirova, K.; Prokleska, J.; Proschek, P.; Valenta, J.; Misek, M.; Gorbunov, D. I.; Wosnitza, J.; Sechovsky, V.

Thermal expansion, magnetostriction, and magnetization measurements under magnetic field and hydrostatic pressure were performed on a UAu2Si2 single crystal. They revealed a large anisotropy of magnetoelastic properties manifested by prominent length changes, leading to a collapse of the unit-cell volume accompanied by breaking the fourfold symmetry (similar to that in URu2Si2 in the hidden-order state) in the antiferromagnetic state as consequences of strong magnetoelastic coupling. The magnetostriction curves measured at higher temperatures confirm a bulk character of the 50K weak ferromagnetic phase. The large positive pressure change of the ordering temperature predicted from Ehrenfest relation contradicts the more than an order of magnitude smaller pressure dependence observed by the magnetization and specific heat measured under hydrostatic pressure. A comprehensive magnetic phase diagram of UAu2Si2 in magnetic field applied along the c axis is presented. The ground-state antiferromagnetic phase is suppressed by a field-induced metamagnetic transition that changes its character from second to first order at the tricritical point

Permalink: https://www.hzdr.de/publications/Publ-28330
Publ.-Id: 28330


Chronic low dose ethanol induces an aggressive metastatic phenotype in TRAMP mice, which is counteracted by parthenolide

Morel, K.; Ormsby, R.; Solly, E.; Tran, L.; Sweeney, C.; Klebe, S.; Cordes, N.; Sykes, P.

Despite advances in prostate cancer therapy, dissemination and growth of metastases results in shortened survival. Here we examined the potential anti-cancer effect of the NF-B inhibitor parthenolide (PTL) and its water soluble analogue dimethylaminoparthenolide (DMAPT) on tumour progression and metastasis in the TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model of prostate cancer. Six-week-old male TRAMP mice received PTL (40mg/kg in 10% ethanol/saline), DMAPT (100mg/kg in sterile water), or vehicle controls by oral gavage thrice weekly until palpable tumour formation. DMAPT treatment slowed normal tumour development in TRAMP mice, extending the time-to-palpable prostate tumour by 20%. PTL did not slow overall tumour development, while the ethanol/saline vehicle used to administer PTL unexpectedly induced an aggressive metastatic tumour phenotype. Chronic ethanol/saline vehicle upregulated expression of NF-B, MMP2, integrin 1, collagen IV, and laminin, and induced vascular basement membrane degradation in primary prostate tumours, as well as increased metastatic spread to the lung and liver. All of these changes were largely prevented by co-administration with PTL. DMAPT (in water) reduced metastasis to below that of water-control. These data suggest that DMAPT has the potential to be used as a cancer preventive and anti-metastatic therapy for prostate cancer. Although low levels of ethanol consumption have not been shown to strongly correlate with prostate cancer epidemiology, these results would support a potential effect of chronic low dose ethanol on metastasis and the TRAMP model provides a useful system in which to further explore the mechanisms involved.

Keywords: Parthenolide; DMAPT; Metastasis; TRAMP; Prostate cancer; Ethanol

Permalink: https://www.hzdr.de/publications/Publ-28329
Publ.-Id: 28329


Investigations on potential methods for the long-term monitoring of the state of fuel elements in dry storage casks

Hampel, U.; Kratzsch, A.; Rachamin, R.; Wagner, M.; Schmidt, S.; Fiß, D.; Reinicke, S.

Extended dry storage of spent nuclear fuel is a relevant issue in many countries operating nuclear power plants. Beside regulatory and security aspects there are questions with respect to the long-term integrity of the spent fuel as this is of relevance for final transportation and reloading to final waste repository casks. Within the frame of the BMWi project DCS-MONITOR, we investigate the potentials of different methods for non-intrusive monitoring of dry cask storage containers with spent nuclear fuel. These are thermography, radiation-based methods, and acoustic methods. For all of them we study the sensitivity and cross-sensitivity with respect to defined changes in the nuclear fuel distribution inside the containers. The analyses are mainly based on numerical simulations but also include some dedicated experimental studies.

Keywords: extended storagy; spent fuel; monitoring

  • Open Access Logo Kerntechnik 83(2018)6, 513-522
    DOI: 10.3139/124.110949
  • Lecture (Conference)
    2nd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel, 06.-08.06.2018, Garching, Deutschland
  • Contribution to proceedings
    2nd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel, 06.-08.06.2018, Garching, Germany
    Proceedings of 2nd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-28328
Publ.-Id: 28328


Effect of neutron flux on the microstructure of irradiated RPV steels

Ulbricht, A.; Bergner, F.

This invited talk about the effect of neutron flux on the microstructure of irradiated RPV steels was given to the participants of a Training School in the Framework of the European project SOTERIA.

Keywords: Pressure vessel steels; neutron irradiation; neutron flux; microstructure

  • Invited lecture (Conferences)
    International SOTERIA Training School, 03.07.-07.09.2018, Valencia, Spain

Permalink: https://www.hzdr.de/publications/Publ-28327
Publ.-Id: 28327


Metallische Verbundwerkstoffe mit funktionellen Eigenschaften

Weissgärber, T.; Schubert, T.; Hutsch, T.; Hilger, I.; Bergner, F.; Kieback, B.

Der Vortrag umfasst Aspekte der Herstellung, Mikrostruktur, Eigenschaften und Anwendung von pulvermetallurgisch hergestellten Werkstoffen. Als Beispielsysteme werden ODS-Fe-Cr-Legierungen, Verbundwerkstoffe für die Elektronikkühlung und Aluminiumverbundwerkstoffe betrachtet.

Keywords: ODS Legierungen

  • Invited lecture (Conferences)
    7. Dresdner Werkstoffsymposium 2018, 06.-07.12.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28326
Publ.-Id: 28326


Cm(III) retention by calcium silicate hydrate (C-S-H) gel and secondary alteration phases in carbonate solutions with high ionic strength: A site-selective TRLFS study

Wolter, J.-M.; Schmeide, K.; Huittinen, N. M.; Stumpf, T.

We studied the Cm(III) retention by calcium silicate hydrate (C-S-H), portlandite (Ca(OH)2) and their alteration products calcite, vaterite, and aragonite in high ionic strength carbonate-containing solutions representing specific formation waters. For this, we synthesized C-S-H gels with calcium to silicon (C/S) ratios of 1.0 and 2.0 in the absence and presence of Cm(III), resulting in Cm(III)-free and Cm(III) doped C-S-H gel, respectively. For phase identification purposes we applied X-ray diffraction (XRD) while for the identification of the Cm(III)/C-S-H binding mode we applied site-selective time-resolved laser-induced luminescence spectroscopy (TRLFS). The stability of Cm(III) doped phases under repository-relevant conditions was evaluated by studying the time-dependent release of Cm(III) from the Cm(III) doped C-S-H gel into leaching solutions containing 0.02 M NaHCO3 or 2.5 M NaCl/0.02 M NaHCO3 over 60 d. Speciation changes of Cm(III) due to leaching were followed with TRLFS while C-S-H structure alterations and secondary phase formation were monitored with XRD. From the results it could be concluded that Cm(III) is not mobilized by aqueous carbonate but either remains incorporated in the C-S-H structure and portlandite or becomes partially re-immobilized into secondary CaCO3 phases. The presence of NaCl led to an accelerated conversion of metastable secondary CaCO3 phases into calcite.

Keywords: curium; C-S-H; portlandite; calcite; site-selective TRLFS; luminescence line narrowing effect; high ionic strength

Permalink: https://www.hzdr.de/publications/Publ-28325
Publ.-Id: 28325


Comparative assessment of different image processing methods to determine the gas-liquid interfacial area in froth regimes of sandwich packings from ultrafast X-ray tomography image data

Sohr, J.; Bieberle, M.; George, G. R.; Flechsig, S.; Kenig, E. Y.; Schubert, M.; Hampel, U.

Sandwich packings consist of alternatingly stacked structured packing layers of different specific surface area. In such packings froth two-phase flow appears when the packing is operated between the loading limits of the layers. For this highly agitated flow regime, there is a lack of hydrodynamic data, in particular on gas-liquid interfacial area. Ultrafast X-ray tomography, a cross-sectional imaging technique with a frame rate of more than 1000 cross-sectional images per second, is applied to visualize the gas-liquid flow and to extract the gas-liquid interfacial area data via image post-processing methods. For that, we assessed different segmentation methods, that are, level set and gray level contour techniques.

Keywords: Sandwich packing; ultrafast X-ray tomography; image segmentation; gas-liquid interfacial area

Permalink: https://www.hzdr.de/publications/Publ-28324
Publ.-Id: 28324


Machbarkeitsstudie zur MRT-integrierten Protonentherapie: Strahlablenkung, Sekundärteilchen und Bildqualität

Schellhammer, S. M.; Gantz, S.; Lühr, A.; Pawelke, J.; Karsch, L.; Smeets, J.; Quets, S.; Burigo, L. N.; Oborn, B.; Bussmann, M.; Hoffmann, A. L.

Einleitung
Ungefähr 50% der Krebspatienten werden durch Strahlentherapie behandelt, und die Protonentherapie (PT) bietet hier aufgrund der begrenzten Eindringtiefe und des steilen Dosismaximums eine sehr gezielte Behandlungsform mit potentiell reduzierten Nebenwirkungen. Die Treffgenauigkeit der Protonentherapie kann jedoch durch Bewegungen und anatomische Veränderungen während der Therapie stark kompromittiert werden. Eine gleichzeitige Bildgebung mittels Echtzeit-Magnetresonanztomographie (MRT) wäre deshalb ideal. Bis heute existieren jedoch keine kombinierten Systeme für MRT und PT. Ziele dieser Studie waren die erste Integration eines MR-Scanners in eine PT-Strahlführung, die experimentelle Verifizierung der Ablenkung des Strahls und der Sekundärteilchen im Magnetfled des MRT-Scanners, die Überprüfung der Machbarkeit einer gleichzeitigen MR-Bildgebung und Bestrahlung, und die Kontrolle der MR-Bildqualität mit und ohne Strahleinfluss.

Material & Methoden
Ein offener MR-Scanner mit einem vertikalen Magnetfeld von 0.22 T (MRJ2200, Paramed Medical Systems SpA) wurde an einer strahldüsenlosen horizontalen Strahlführung (Ion Beam Applications SA) installiert, und durch einen kompakten Faraday-Käfig von Hochfrequenz-Interferenzen abgeschirmt (Abb. 1). Die Strahlablenkung und der Einfluss des Magnets auf die Sekundärteilchen im Strahl wurden mithilfe an einem PMMA-Phantom befestigter radiochromischer Filme (EBT3, Ashland) in einem 1 T Magneten gemessen und mit Monte-Carlo-simulationsbasierten Vorhersagen verglichen. Zur Überprüfung der MR-Bildgebung wurden anatomische MR-Bilder eines Probanden bei ausgeschalteter Strahlführung sowie MR-Bilder eines Gewebephantoms und eines dedizierten Bildqualitätsphantoms mit und ohne Strahleinfluss (bei 125 MeV und 5 nA) aufgenommen.

Ergebnisse
Die gemessene Ablenkung des Strahls sowie lokale Dosiserhöhung durch Sekundärteilchen im Magnetfeld waren gering (< 1 cm bzw. 2%) und zeigten sehr gute Übereinstimmung mit simulationsbasierten Vorhersagen. Die MR-Aufnahmen (Abb. 2) zeigten die für den verwendeten Scanner übliche Bildqualität. Es wurde keine Veränderung der Bildqualität durch die Strahlführungsmagneten und den Protonenstrahl beobachtet, jedoch eine gleichförmige, korrigierbare Bildverschiebung (< 1 mm) in Frequenzkodierrichtung.

Diskussion
Die Integration eines offenen MR-Scanners in den experimentellen Strahlengang einer Protonentherapie-Anlage war erfolgreich. Die Einflüsse des Magnetfelds des MRT-Scanners auf den Strahl sind vorhersagbar und eine gleichzeitige MR-Bildgebung und Bestrahlung ohne Bildverzerrung ist möglich. Dies rechtfertigt die Entwicklung eines ersten Prototyps für die MRT-integrierte Protonentherapie.

  • Poster
    1. Deutscher KrebsForschungsKongress (DKFK) | 1st German Cancer Research Congress (GCRC), 04.-05.02.2019, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28323
Publ.-Id: 28323


Including anatomical variations in robust optimization for head and neck proton therapy can reduce the need of adaptation

Cubillos-Mesías, M.; Troost, E. G. C.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.

Background and purpose: Classical robust optimization considers uncertainties in patient setup and particle range. However, anatomical changes occurring during the treatment are neglected. Our aim was to compare classical robust optimization (cRO) with anatomical robust optimization (aRO), to quantify the influence of anatomical variations during the treatment course, and to assess the need of adaptation.
Materials and methods: Planning CT and weekly control CTs (cCTs) from 20 head and neck patients were analysed. Three intensity-modulated proton therapy (IMPT) plans were compared: conventional PTV-based plan; cRO, using solely the planning CT, and aRO, including additionally the first 2 cCTs in the optimization. Weekly and total cumulative doses, considering anatomical variations during the treatment, were calculated and compared with the nominal plans.
Results: Nominal plans fulfilled clinical specifications for target coverage (D98% ≥ 95% of prescribed dose). The PTV-based and cRO approaches were not sufficient to account for anatomical changes during the treatment in 10 and 5 patients, respectively, resulting in the need of plan adaptation. With the aRO approach, in all except one patient the target coverage was conserved, and no adaptations were necessary.
Conclusion: In 25% of the investigated cases, classical robust optimization is not sufficient to account for anatomical changes during the treatment. Adding additional information of random anatomical variations in the optimization improves plan robustness.

Keywords: Robust optimization; head and neck cancer; proton therapy; treatment planning; anatomical variations; dose accumulation; plan adaptation

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Permalink: https://www.hzdr.de/publications/Publ-28322
Publ.-Id: 28322


McSAFE - High Performance Monte Carlo methods for safety demonstration

Vocka, R.; Sanchez, V.; Mercatali, L.; Malvagi, F.; Smith, P.; Dufek, J.; Seidl, M.; Milisdorfer, L.; Leppänen, J.; Hoogenboom, E.; Kliem, S.; van Uffelen, P.; Kerkar, N.

The main objective of the McSAFE project is the development of the Monte Carlo based multiphysics coupled methodologies for reactor analysis and safety investigations of different reactor systems. Key-research areas are e.g. advanced depletion methods, optimal coupling of MC-codes to thermalhydraulic solvers, time-dependent Monte Carlo and methods and algorithms for massively parallel simulations. The project has started in September 2017 under the coordination of KIT. Among the other partners are European research institutes and technical support organizations (VTT, JRC, CEA, HZDR, NRI, KTH,WOOD), electricity providers (CEZ, PreussenElektra) and consultants (DNC). The software developed within the project should allow for the high precision evaluation of core safety parameters and will be applicable also to VVER reactor types.

  • Contribution to proceedings
    28. Symposium of AER, 08.-12.10.2018, Olomouc, Czech Republic
    Proceedings of the 28. Symposium of AER, Budapest: MTA EK, 9789637351303, 237-238

Permalink: https://www.hzdr.de/publications/Publ-28321
Publ.-Id: 28321


Development of highly affine 18F-labelled radiotracers for PET imaging of the adenosine A2A receptor

Lai, T. H.; Schröder, S.; Ludwig, F.-A.; Fischer, S.; Moldovan, R.-P.; Scheunemann, M.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Steinbach, J.; Brust, P.

Objectives: The adenosine A2A receptor (A2AR) is a G-protein-coupled-receptor which is mainly expressed in the basal ganglia (including striatum) of the brain and in cells of the immune system. Radiotracers for A2AR imaging have emerged as promising candidates for the diagnosis of neurodegenerative and neurooncological diseases. Aiming at the development of such radiotracer with improved molecular imaging properties, a library of 21 fluorinated pyrazolo[2,3-d]pyrimidine derivatives was synthesized based on a recently published lead compound [1]. Among those, the highly affine 4 fluorobenzyl derivate 1 (Ki(hA2A) = 5.3 nM; Ki(hA1) = 220 nM) and the 2 fluorobenzyl derivate 2 (Ki(hA2A) = 2.1 nM; Ki(hA1) = 147 nM) were chosen for 18F isotopoic labelling although the introduction of 18F at non-activated aromatic positions is challenging. Herein, we report on the radiosyntheses of [18F]1 and [18F]2 via an alcohol-enhanced copper-mediated one-step radiofluorination and their first biological evaluation.

Methods: Three different labelling strategies for the synthesis of [18F]1 have been investigated (Fig. 1). The first two were using [18F]fluorobenzaldehyde ([18F]B) as intermediate, which was produced by nucleophilic radiofluorination of a trimethylammonium precursor of type A (step a). Compound [18F]B was used either in a reductive amination reaction (step b) or it was further reduced to the corresponding alcohol (step c) followed by an Appel bromination to get [18F]C (step d) which was finally used in a benzylation reaction (step e). The third strategy, a one-step approach, started from the boronic acid pinacol ester precursor of type D employing [18F]TBAF and Cu(OTf)2(py)4 in n-BuOH/DMA (step f). The specific binding of [18F]1 and [18F]2 was evaluated in vitro by autoradiography of mice brain slices using 1, 2 and ZM241385 as different blocking agents.

Results: The two- and four-step labelling strategies resulted in an overall radiochemical yield of only 1.4% and 10%, respectively for [18F]1 (non-isolated). Therefore, [18F]1 and [18F]2 were prepared by an alcohol-enhanced copper-mediated one-step radiolabelling approach starting from the corresponding boronic acid pinacol ester precursor D. Compound [18F]1 was obtained with a radiochemical yield of 52+7% (n = 5, EOB), a molar activity of 135+64 GBq/µmol (n = 4, EOS) and a radiochemical purity of >98%. Compound [18F]2 was synthesized with a radiochemical yield of 9+1% (n = 2, EOB), a molar activity of 132 GBq/µmol (n = 1, EOS) and a radiochemical purity of >98%. In vitro autoradiography performed with [18F]2 showed high binding in the striatum, which could be blocked by selective A2AR ligands thus proving the specificity of the new radiotracer (Fig. 1).

Conclusions: An efficient copper-mediated one-step radiolabelling procedure was established for two new highly affine A2AR radiotracers. In a first in vitro study on mice brain slices, [18F]2 demonstrated excellent imaging properties. Further biological in vitro and in vivo investigations are needed to completely evaluate the potential of both A2AR radiotracers.

Acknowledgments: This work has been supported by the the European Regional Development Fund and Sächsische Aufbaubank (project no. 100226753).

References: [1] Gillespie et al., Bioorg. Med. Chem. Lett. 2008, 18, 2924-2929.

Keywords: adenosine; A2A; PET; 18F; radiofluorination

  • Lecture (Conference)
    The 23rd International Symposium on Radiopharmaceutical Sciences (ISRS2019), 26.-31.05.2019, Peking, China

Permalink: https://www.hzdr.de/publications/Publ-28320
Publ.-Id: 28320


Synthesis, Receptor Affinity, and Antiallodynic Activity of Spirocyclic σ Receptor Ligands with Exocyclic Amino Moiety

Bergkemper, M.; Kronenberg, E.; Thum, S.; Börgel, F.; Daniliuc, C.; Schepmann, D.; Nieto, F. R.; Brust, P.; Reinoso, R. F.; Alvarez, I.; Wünsch, B.

In order to detect novel σ receptor ligands, the rigit spiro [[2]benzopyran-1,1'-cyclohexan]-4'-one was connected with amino moieties derived from σ2 receptor preferring lead compounds resulting in mixtures of trans- and cis-configured amines 6, 18, and 27. In a four step synthesis the methyl acetals 6 were converted into fluoroethyl derivatives 13 and 30. The most promising σ2 receptor ligand is the methyl acetal 6a bearing a 2,4-dimethylbenzylamino moiety. The fluoroethyl derivatives 13c and 13d reveal high σ1 affinity but moderate selectivity over the σ2 subtype. In mice 13c and 13d showed antiallodynic activity that is stronger than that of the reference σ1 antagonist BD-1063 (34). Since the antiallodynic activity of 13c could only be partially reversed by the σ1 agonist PRE-084 (35), it is postulated that a second mechanism contributes to its overall antiallodynic effect. In contrast, the antiallodynic effect of its diastereomer 13d can be totally explained by a σ1 antagonism.

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Permalink: https://www.hzdr.de/publications/Publ-28319
Publ.-Id: 28319


The Serial Interface Package -- v2.0

Seilmayer, M.

The 'serial' package as an extension to the programming language R enables reading and writing binary and ASCII data to RS232/RS422/RS485 or any other virtual serial interfaces of the computer.

Keywords: serial interface; RS232; RS422; RS485; R

  • Software in external data repository
    Publication year 2018
    Programming language: R
    System requirements: Windows, Mac, Unix
    License: GPL-2
    Hosted on r-project.org: Link to location

Permalink: https://www.hzdr.de/publications/Publ-28318
Publ.-Id: 28318


Characterization and beneficiation of pyrolyzed black mass from spent lithium ion batteries

Vanderbruggen, A.

The lithium-ion battery (LiB) market is growing rapidly which leads to a considerable increase of LiB wastes. Despite the enhancement in graphite consumptions, there is no graphite recycling process from LiBs so far. Thus, graphite usually remains in slags from the metallurgical treatments.
The LiB components contain cobalt (Co), lithium (Li) and graphite, counted as critical materials. The aim of the present thesis is to increase the recycling recovery of the LiBs by developing a new innovative process, which minimizes metal losses and is able to recover graphite. By using flotation two valuable products, one of graphite and one with the valuable metals, are recovered in the light of their integration to the value chain of LiB production.
Mineral liberation analysis (MLA), x-ray fluorescence (XRF) and x-ray diffraction (XRD) were used for characterization of the black mass to understand the liberation behavior of the crushed LiB particles. Flotation tests were carried out in an Outotec GTK Labcell, the main studied parameters are the pre-treatment with attritioning, the flotation pH and the reagents dosages. Kerosene was used as a promoter for graphite and MIBC as a frother.
It was found that graphite particles were fully liberated from the copper foils, and the organic layer on the active particles was removed which increases the separation efficiency. However, only 62 wt. % of the cathode active particles are liberated from the aluminum foil. Based on this characterization results, particularly the liberation degree, a new flowsheet is designed to concentrate all the active material (graphite, Co, Ni, Mn and Li) in the < 50 μm fraction without current foil particles. Flotation studies show that pretreatment, such as attritioning, improved the process efficiency while preserving the spherical shape of graphite. Graphite recovery is +98 % with a grade of 72 wt. % and the tailings recover more than 90% of the precious metals Co, Ni and Li from the spent LiBS, with the respective grades 27 wt. % Co, 7 wt. % and 2.5 wt. % Li. Most of the concentrate impurities are fine particles from cathode active materials, which could be removed with a desliming process and flotation cleaner stages. This research is at its beginning and is expected to bring about an innovative and useful process for the recycling industry, despite the challenges involved. This process can recover the graphite and the lithium, which are usually ending the slags. At present, there might be legitimate questions regarding the expense and benefits of graphite recycling. However, the treatment of LiBs will become necessary in the near future due to environmental issues as well as the scarcity and criticality of LiB components. Consequently, graphite will become a valuable and needed by-product from the metals recycling. The dependence on imports of graphite from China would be reduced, providing a solution to meet the significant predicted demand of battery grade graphite. Moreover, LiB as a key driver of the transition away from a carbon-based economy, it is necessary to ensure a truly positive impact over the lifecycle of LiB, and consequently to reach a closed-loop system.

Keywords: Attritionning; black mass; characterization; flotation; graphite; mineral liberation analysis (MLA); pre-treatment; recycling; spent lithium-ion battery; surface analysis

  • Master thesis
    TU Freiberg, 2018
    Mentor: Dr. Martin Rudolph

Permalink: https://www.hzdr.de/publications/Publ-28317
Publ.-Id: 28317


Characterization and beneficiation of pyrolyzed black mass from lithium ion batteries

Vanderbruggen, A.; Gilbricht, S.; Möckel, R.; Rudolph, M.

The lithium-ion battery (LiB) market is growing rapidly. Consequently, LiB wastes will increase in the future and LiB components such as Co, Li, but also graphite, are forecast to be critical materials. These critical materials are contained in the black mass produced by LiBs recycling. This original research focuses on graphite beneficiation from cathode lithium metal oxides by flotation. Detailed characterization of the pyrolyzed black mass (inculding MLA, XRF and XRD) shows that the graphite particles are fully liberated from the copper foils, and the organic layer PVDF is removed. Batch flotation shows that pretreatment, such as attritioning, improves process efficiency while preserving the shape of spheriodized graphite. Concentrate impurities mainly comprise fine particles from cathode active materials, which can be removed with desliming and flotation cleaner stages. As an outlook, this reasearch is expected to bring about an innovative and useful process for the recycling industry.

Keywords: Attritionning; black mass; characterization; flotation; graphite; mineral liberation analysis (MLA); pre-treatment; recycling; spent lithium ion battery; surface analysis

  • Poster
    Minerals Engineering International (MEI) conference: Process Mineralogy '18, 19.-21.11.2018, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-28316
Publ.-Id: 28316


Serpent solution of the X2 VVER-1000 benchmark fresh core experiments

Bilodid, Y.; Fridman, E.

The X2 VVER-1000 benchmark describes first 4 fuel cycles of the Khmelnitsky NPP 2nd unit with VVER-1000 reactor as well as some operational transients. The benchmark specifications contain description of the reactor core material, geometry and operational history supplemented by measured operational data and startup experiments. In this work, the hot zero power experiments conducted during the fresh core startup are modelled with the Serpent-2 Monte Carlo code. The numerical results are validated against the available measured core data. The calculated and measured values of a critical boron concentration, temperature reactivity effect, and control rod worth are in a very good agreement while the deviations lay within the measurement uncertainties. Since the power distribution was not measured at the hot zero power state, the obtained Serpent solution could be used as a reference for a deterministic codes verification.

Keywords: X2 benchmark; VVER-1000; Serpent

  • Contribution to proceedings
    PHYSOR 2018: Reactor Physics Paving The Way Towards More Efficient Systems, 22.-26.04.2018, Cancun, Mexico, 1982-1989

Permalink: https://www.hzdr.de/publications/Publ-28315
Publ.-Id: 28315


Doping issues in silicon nanowires by ion implantation and flash lamp annealing

Berencen, Y.; Prucnal, S.; Wang, M.; Rebohle, L.; Helm, M.; Zhou, S.; Skorupa, W.

Semiconducting nanowires (NWs) hold promises for functional nanoscale devices. Although several applications have been demonstrated in the areas of electronics, photonics and sensing, the doping of NWs remains challenging. Ion implantation is a standard doping method in top-down semiconductor industry, which offers precise control over the areal dose and depth profile as well as allows for the doping of all elements of the periodic table even beyond their equilibrium solid solubility. Yet its major disadvantage is the concurrent material damage. A subsequent annealing process is commonly used for the healing of implant damage and the electrical activation of dopants. This step, however, might lead to the out-diffusion of dopants and eventually the degradation of NWs because of the low thermal stability caused by the large surface–area-to-volume ratio.

In this work, we report on non-equilibrium processing (flash lamps) for controlled doping of drop-casted Si/SiO2 core/shell NWs with shallow- and deep-level dopants below and above their equilibrium solid solubility. The approach lies on the implantation of either shallow-level dopants, such as B and P, or deep-level dopants like Se followed by millisecond flash lamp annealing. In case of amorphization upon high-fluence implantation, recrystallization takes place via a bottom-up template-assisted solid phase epitaxy. Non-equilibrium Se concentrations lead to intermediate-band Si/SiO2 core/shell NWs that have room-temperature sub-band gap photoresponse when configured as a photoconductor device [1]. Alternatively, the formation of a cross-sectional p-n junction is demonstrated by co-implanting P and B in individual NWs at different depth along the NW core.
[1] Y. Berencén, et al. Adv. Mater. Interfaces 2018, 1800101

Keywords: doping; nanowires; semiconductor; silicon; ion implantation; flash lamp annealing

  • Lecture (Conference)
    22nd International Conference on Ion Implantation Technology, 16.-21.09.2018, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28313
Publ.-Id: 28313


Hydrodynamics, mixing and mass transfer in a pilot-scale bubble column with dense internals

Möller, F.; Lavetty, C.; Schleicher, E.; Löschau, M.; Hampel, U.; Schubert, M.

Bubble column reactors with exothermic reactions are often equipped with dense tube bundle heat exchangers. While there is some knowledge about the impact of such internals on hydrodynamics and mass transfer for narrow columns, its role in pilot-scale columns is less clear. In this paper we report on a study of hydrodynamics and mass transfer in a BCR of 4.2 m height and 0.392 m diameter. We investigated different tube arrangements with triangular and square pitch and tube diameters of 32×10-3 m and 45×10-3 m at the same cross-sectional coverage (~25%). The column was operated at homogeneous and heterogeneous flow conditions. A customized three-layer wire-mesh sensor was utilized to visualize gas phase dynamics and liquid mixing characteristics in the column’s cross-section. We found that sub-channel size is the most crucial geometric design parameter. Tracer mixing experiments reveal that internals enhance the liquid dispersion due to induction of large-scale liquid circulation. Mass transfer was studied with the oxygen stripping method. Here we found, that the effect of the internals on the gas-liquid mass transfer is almost negligible. Eventually, correlations for gas holdup, axial liquid dispersion and the volumetric gas-liquid mass transfer coefficient are given, which take the internals’ geometry into account.

Keywords: Pilot-scale bubble column; Heat exchanger internals; Hydrodynamics; Liquid mixing; Mass transfer; Wire-mesh sensor

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Permalink: https://www.hzdr.de/publications/Publ-28312
Publ.-Id: 28312


Advanced doping issues using nonequilibrium processing

Skorupa, W.; Rebohle, L.; Prucnal, S.; Berencen, Y.; Zhou, S.; Helm, M.

In this talk I will introduce with a short view on the background of the transistor invention as a key element driving the topic of semiconductor doping. After that I will discuss examples of advanced doping including ion beam based and other methods: doping and alloying of germanium, hyperdoping of silicon, doping from deposited layers, doping of silicon nanowires, doping from deposited layers. In all cases the experiments were performed in correlation to nonequilibrium thermal processing using flash lamps in the millisecond time range.

Keywords: semiconductor doping; ion beam based methods; flash lamp annealing

  • Lecture (others)
    Eingeladener Seminarvortrag an der Marie-Curie-Universität Lublin/Polen, 11.10.2018, Lublin, Polen

Permalink: https://www.hzdr.de/publications/Publ-28311
Publ.-Id: 28311


Dataset on characterization, ion irradiation and nanoindentation of ODS Fe14Cr-based alloys

Bergner, F.

The dataset comprises raw data of the nanoindentation tests and processed data on the ion irradiations and irradiation-induced hardness changes. File formats are excel, word, origin and ascii.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-12-04
    DOI: 10.14278/rodare.72

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Permalink: https://www.hzdr.de/publications/Publ-28310
Publ.-Id: 28310


Bonding and stability analysis of tetravalent f-element complexes with mixed N-, O-donor ligands

Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.

The contribution of the f-orbitals leads to a very rich chemistry of the f-elements[1] where it is known that this contribution is less important for lanthanides. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands re- flecting natural bonding motifs.
This study shows the different bonding behaviour of tetravalent f-elements with Schiff bases, like salen (see Fig. 1) and derivatives, by means of real-space bonding analysis. This includes the popular quantum theory of atoms in molecules (QTAIM), plots of the non-covalent inter- actions (NCI)[2] and density differences complemented by natural population analysis (NPA). Thermodynamic calculations on the stability of these complexes are presented. The obtained results are a direct consequence of the different interaction strengths of the f-elements.
First studies reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the inter- action between the actinides and the nitrogen of salen is much weaker.
By acquiring knowledge about the different behaviours of bonding and complexation it is possi- ble to understand the chemical properties of the f-elements and predict yet unknown complexes.

Keywords: Bonding analysis; Theoretical Chemistry; DFT; QTAIM; Actinides

  • Poster
    Symposium on Theoretical Chemistry, 17.-20.09.2018, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28309
Publ.-Id: 28309


Nanoindentation of single- (Fe) and dual-beam (Fe and He) ion-irradiated ODS Fe-14Cr-based alloys: Effect of the initial microstructure on irradiation-induced hardening

Heintze, C.; Hilger, I.; Bergner, F.; Weissgärber, T.; Kieback, B.

Although the view that nm-sized oxide particles modify and essentially improve the irradiation resistance of Fe-Cr-based alloys is widely accepted, the correctness of this view has only been demonstrated in singular cases. An extension of the field of considered microstructures, irradiation conditions, and measures of irradiation resistance is required. The present study is focused on nanostructured ferritic Fe-14%Cr-based alloys, with and without the addition of 0.6 wt% Y2O3, produced via mechanical alloying and consolidation by spark plasma sintering. The materials were exposed to single-beam (Fe) and dual-beam (Fe+He) ion irradiations at room temperature. The initial microstructures were characterized, bimodal grain size distributions were observed and nanoindentation was applied to measure irradiation hardening for fine-grained and coarse-grained areas separately. We have found that grain size governs irradiation hardening for single-beam irradiation, while oxide nanoparticles play a dominant role for dual-beam irradiations. This sheds a light on the role of particle-matrix interfaces on helium management.

Keywords: Nanostructured ferritic alloys; oxide dispersion strengthening; ion irradiation; dual-beam irradiation; helium; nanoindentation; irradiation hardening

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-28308
Publ.-Id: 28308


Bonding and stability analysis of tetravalent actinide and lanthanide complexes with N,O-donor ligands

Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.

The contribution of the f-orbitals leads to a very rich chemistry of the f-elements[1] where it is known that this contribution is less important for lanthanides. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study shows the different bonding behaviour of tetravalent actinide and lanthanide complexes with Schiff bases, like salen (see Fig. 1) and derivatives, by means of real-space bonding analysis. This includes the popular quantum theory of atoms in molecules (QTAIM), plots of the non-covalent interactions (NCI)[2] and density differences complemented by natural population analysis (NPA). Thermodynamic calculations on the stability of these complexes are done being a direct consequence of the different interaction strengths of the f-elements.
First studies reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker.
By acquiring knowledge about the different behaviours of bonding and complexation it is possible to understand the chemical properties of the f-elements and predict yet unknown complexes.

Keywords: Bonding; Salen; Actinides; theoretical chemistry; DFT; QTAIM

  • Lecture (Conference)
    International Symposium on Nano and Supramolecular Chemistry, 09.-12.07.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28307
Publ.-Id: 28307


The Study and Development of Pulsed High-field Magnets for Application in Laser-plasma Physics

Kroll, F.

The thesis at hand addresses design, characterization and experimental testing of pulsed high-field magnets for utilization in the field of laser-plasma physics. The central task was to establish a technology platform that allows to manipulate laser-driven ion sources in a way that the accelerated ions can be used in complex application studies, e.g. radiobiological cell or tumor irradiation.

Laser-driven ion acceleration in the regime of target normal sheath acceleration (TNSA) offers the unique opportunity to accelerate particles to kinetic energies of few 10MeV on the micrometer scale. The generated bunches are short, intense, show broad exponentially decaying energy spectra and high divergence. In order to efficiently use the generated particles, it is crucial to gain control over their divergence directly after their production. For most applications it additionally is favorable to reduce the energy spread of the beam. This work shows that the developed pulsed high-field magnets, so-called solenoids (cylindrical magnets), can efficiently capture, transport and focus laser-accelerated protons. The chromaticity of the magnetic lens thereby provides for energy selection.

Three prototype solenoids, adapted to fit different application scenarios, and associated current pulse drivers have been developed. The magnets generate fields of several 10 T. Pulse durations are of the order of one millisecond and thus the fields can be considered as quasi-static for laser-plasma interaction processes taking place on the ps- to ns-scale. Their high field strength in combination with abandoning magnetic cores make the solenoids compact and light-weight.

The presented experiments focus on a solenoid magnet designed for the capture of divergent laser-driven ion beams. They have been carried out at the 6MV tandetron accelerator and the laser acceleration source Draco of Helmholtz-Zentrum Dresden – Rossendorf as well as at the PHELIX laser of GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The results show that the developed technology platform breaks ground for a variety of practical applications of laser ion acceleration. It is shown that laser-driven ion beams can be efficiently injected into conventional accelerator structures to allow for phase space modulation. Furthermore, first practical studies on medical beam guidance systems are presented. Hence, the developed magnets allow to investigate feasibility and potential of the frequently proposed laser-based ion beam therapy of tumor diseases. The pulsed high-field magnets bring us one step closer to the realization of this ambitious endeavor, as they pave the way for compact and efficient beam guidance toward the patient but also, in the phase of translational research, allow to study the radiobiological properties of the novel particle source. In this context, worldwide first irradiation studies with laser-accelerated protons on volumetric tumors in the mouse model have been prepared and their feasibility studied, identifying already met radiobiological criteria and hurdles yet to overcome.

Keywords: Pulsed magnets; high-field magnets; beam transport; laser-acceleration; laser acceleration; TNSA; laser particle acceleration; laser-radiooncology

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-094 2018
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-28306
Publ.-Id: 28306


Photo-induced THz response of VO2 under high pressures

Braun, J. M.; Schneider, H.; Helm, M.; Mirek, R.; Boatner, L. A.; Marvel, R. E.; Haglund, R. F.; Pashkin, A.

We apply ultrafast optical pump – THz probe spectroscopy in order to investigate the nature of the high pressure metallic state of VO2 single crystal. The pump excitation was performed using near-infrared pulses at the wavelength of 800 nm. The probe pulses with a frequency of 30 THz were generated by difference frequency mixing and focused on the sample mounted inside a diamond anvil pressure cell. Using the probe photon energy far below the bandgap of VO2 we were able to explore the response of free charge carriers near the Fermi level.

  • Lecture (Conference)
    Non-equilibrium Dynamics of Condensed Matter in the Time Domain, 03.-06.09.2018, Kerkrade, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-28305
Publ.-Id: 28305


Photoinduced non-thermal insulator-to-metal transition in NbO2 epitaxial thin films

Rana, R.; Klopf, M. J.; Grenzer, J.; Schneider, H.; Helm, M.; Pashkin, A.

Ultrafast insulator-to-metal transition in the correlated oxides such as vanadium dioxide (VO2) has been extensively explored for rich physics and potential applications. In this regard, its isovalent counterpart niobium dioxide (NbO2) with considerably higher transition temperature (Tc = 1080 K) can be envisaged as a potential candidate. We have performed time-resolved optical pump – terahertz (THz) probe measurements on NbO2 epitaxial thin at room temperature.
The onset of the THz conductivity is followed by an exponential decay on a timescale of 400 fs. The photoinduced change in THz transmission at later delay times exhibits excitation threshold of 17.5 mJ/cm2. Notably, in contrast to VO2, the pump energy required for the switching into a metastable metallic state is smaller than the energy necessary for heating NbO2 up to Tc providing a strong evidence for the non-thermal character of the photoinduced insulator-to-metal transition in this system. The transient optical conductivity in the metastable state can be modelled using the Drude model confirming its metallic character.

  • Lecture (Conference)
    DPG-Frühjahrstagung 2018, 11.-16.03.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-28304
Publ.-Id: 28304


Development of a new 18F-labeled radioligand for imaging of sigma2 receptors by positron emission tomography

Ludwig, F.-A.; Fischer, S.; Moldovan, R.-P.; Deuther-Conrad, W.; Kranz, M.; Schepmann, D.; Jia, H.; Wünsch, B.; Brust, P.

Objectives: Sigma2 receptors (S2R) have been found in CNS, liver, kidney, as well as endocrine glands and are suggested to play important roles in the regulation of cell differentiation. Besides their overexpression in various tumor cell lines, derived from e.g. breast, brain, colon, lung, pancreas, and prostate, they show a 10-fold higher expression in the proliferating vs quiescent status and thus are possible markers of solid tumor’s proliferative status. To quantify the S2R availability in living subjects, we aim for the development of a new class of S2R ligands that could be labeled by fluorine-18.
Methods: Starting from structural motifs known for S2R ligands [1, 2], we modified the indole ring system in A and synthesized a novel series of fluorine containing indole and aza-indole derivatives (1a-d and 2-6 in Fig. 1). Their binding affinities towards sigma2 and sigma1 receptors were determined by radioligand-binding assays, and 2 was selected for synthesis of a boronic acid pinacol ester precursor for radiolabeling. Synthesis of [18F]2 was optimized starting from 100-500 MBq of 18F-fluoride, using Kryptofix (K2.2.2.)/ K2CO3 (0.18-1.8 µmol/ 0.04-0.35 µmol) as well as TBAHCO3 (2.3 and 7.5 µmol) and 2-4 mg of precursor 7, in the presence of Cu(OTf)2py4 (0.4-6.8 eq.) in various solvent systems at 80-135 °C, monitored for 5-20 min. For monitoring, several analytical methods (radio-UHPLC, -HPLC, and -TLC) have been established, e.g. on the basis of RP18 und RP8 stationary phases for LC systems. Besides, different techniques for purification and isolation were investigated, including a substitution of semi-preparative HPLC by time-saving cartridge systems.
Results: By altering the heterocyclic system of A, a small series of fluorinated aza-indoles was synthesized (Fig. 1), of which 2 showed most promising binding affinity and selectivity (Ki(S2R) = 1.6 nM; Ki(S1R) = 691 nM). Radiosynthesis of [18F]2 was achieved with RCYs in a range of 20-45% (n = 2, all non-isolated, radio-UHPLC) by use of 2.0 mg of precursor 7 (4.1 µmol) and 3.6 eq. of Cu(OTf)2py4 at 115 °C within 10 min. The reaction was accompanied by the formation of a by-product (bp) which increased over time. Using the K2.2.2./ K2CO3 system resulted in RCYs of 21.5% (bp 5.5%) and 27.7 % (bp 4.6%), in DMF and DMA/ n-BuOH, respectively. Application of TBAHCO3 showed further increased conversions, represented by a RCY of 44.8% (bp 9.1%) in DMA/ n-BuOH. For subsequent semi-preparative HPLC, separation conditions were optimized, but still lack from low recoveries. As an alternative, SPE procedures using cartridge systems (SiO2, RP18) are being established and could be used as a time saving technique for the isolation of [18F]2.
Conclusions: A novel S2R-affine aza-indole derivative 2 was synthesized and radiofluorination of the appropriate boronic acid pinacol ester precursor afforded [18F]2 in RCYs of up to 45% (non-isolated). The optimal parameters for the radiosynthesis, conducted in a synthesis automat or module, have to be determined to setup a procedure for the production of [18F]2, which enables detailed preclinical in vitro and in vivo studies of this promising radioligand.
Acknowledgement: The authors would like to thank the Deutsche Forschungsgemeinschaft (DFG) for financial support (BR 1360/13-1).
References:
[1] Georgiadis, M.-O. et al. Molecules 2017, 22, 1408;
[2] Wang, L. et al. Bioorg Med. Chem. 2017, 25, 3792-3802

Keywords: Positron emission tomography; PET; fluorine-18; sigma2; indole; aza-indole

  • Poster
    23. International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Peking, China
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 62(2019), 181

Permalink: https://www.hzdr.de/publications/Publ-28303
Publ.-Id: 28303


Electron dynamics in InxGa1-xAs shells around GaAs nanowires probed by terahertz spectroscopy

Fotev, I.; Balaghi, L.; Schmidt, J.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, A.

We present the electrical properties of GaAs/InxGa1-xAs core/shell nanowires measured by ultrafast optical pump - terahertz probe spectroscopy.
This contactless technique was used to measure the photoconductivity of nanowires with shell compositions of x = 0.20, 0.30 and 0.44. The results were fitted with the model of localized surface plasmon in a cylinder in order to obtain electron mobilities, concentrations and lifetimes in the InxGa1-xAs NW shells.
The estimated lifetimes are about 80 - 100 ps and the electron mobility reaches 3700 cm2/Vs at room temperature. This makes GaAs/InGaAs nanowires good candidates for the near-future realization of InGaAs based high-electronmobility transistor.

Keywords: GaAs nanowires; terahertz spectroscopy; ultrafast dynamics; electron mobility; plasmon; carrier lifetime

Permalink: https://www.hzdr.de/publications/Publ-28302
Publ.-Id: 28302


Nonthermal nature of photo-induced insulator-to-metal transition in NbO2

Rana, R.; Klopf, J. M.; Grenzer, J.; Schneider, H.; Helm, M.; Pashkin, A.

We study the photo-induced metallization process in niobium dioxide NbO2. This compound undergoes the thermal insulator-to-metal transition at the remarkably high temperature of 1080 K. Our optical pump ¬– terahertz probe measurements reveal the ultrafast switching of the film on a sub-picosecond timescale and the formation of a metastable metallic phase when the incident pump fluence exceeds the threshold of ~10 mJ/cm2. Remarkably, this threshold value corresponds to the deposited energy which is capable of heating NbO2 only up to 790 K, thus, evidencing the non-thermal character of the photo-induced insulator-to-metal transition. We also observe an enhanced formation of the metallic phase above the second threshold of ~17.5 mJ/cm2 which corresponds to the onset of the thermal switching. The transient optical conductivity in the metastable phase can be modeled using the Drude-Smith model confirming its metallic character. The present observation of non-thermal transition in NbO2 can serve as an important test bed for understanding photo-induced phenomena in strongly correlated oxides.

Keywords: metal-insulator transition; pump-probe spectroscopy; transition metal oxides

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Permalink: https://www.hzdr.de/publications/Publ-28301
Publ.-Id: 28301


Optical Pump – THz Probe Response of VO2 under High Pressure

Braun, J. M.; Schneider, H.; Helm, M.; Mirek, R.; Boatner, L. A.; Marvel, R. E.; Haglund, R. F.; Pashkin, A.

We present the ultrafast THz response of VO2 under high pressures. A clear anomaly is observed around 8 GPa indicating a pressure-induced phase transition. Our observations can be interpreted in terms of a bandwidth-controlled Mott-Hubbard transition.

Keywords: metal-insulator transition; high pressure; VO2; pump-probe spectroscopy

  • Open Access Logo Contribution to proceedings
    XXI International Conference on Ultrafast Phenomena, 15.-20.07.2018, Hamburg, Deutschland
    Proceedings of Ultrafast Phenomena XXI, 91944 Les Ulis cedex A - France: EDP Sciences Web of Conferences
    DOI: 10.1051/epjconf/201920504003

Permalink: https://www.hzdr.de/publications/Publ-28300
Publ.-Id: 28300


Optical Pump – THz Probe Response of VO2 under High Pressure

Braun, J. M.; Schneider, H.; Helm, M.; Mirek, R.; Boatner, L. A.; Marvel, R. E.; Haglund, R. F.; Pashkin, A.

We present the ultrafast THz response of VO2 under high pressures. Pump-probe signals and a photoexcitation threshold are detected even in a metallic state. Our observations can be described as a pressure-driven Mott-Hubbard transition.

Keywords: vanadium dioxide; high pressure; pump-probe spectroscopy

  • Lecture (Conference)
    XXI. International Conference on Ultrafast Phenomena, 15.-20.07.2018, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28299
Publ.-Id: 28299


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