Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34293 Publications

Multiconfigurational calculations of ground state and excited states of tetravalent uranium complexes

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

The peculiarities of computational actinide chemistry concerning the ground and excited state require state-of-the-art electronic structure methods. Currently, the most popular one is the CASSCF- method for the inclusion of static correlation in combination with CASPT2 for dynamic correlation and CASSI for spin-orbit coupling. This combination is used for the evaluation of excited state energies and transitions for simulating electronic spectra and comparing with experimental findings. Furthermore, for the evaluation of a proper active space the DMRG method is used for a choice based on objective reasonings. It is found, that the CASSCF+CASPT2+CASSI combination is able to recover experimental values quite well even for a small basis set. However, the DMRG method reveals that the active space could potentially be improved by not only considering the two electrons in the seven 5f-orbitals but also including C-N-pi and corresponding C-N-pi* orbitals.

Keywords: CASSCF; DMRG; electron correlation; actinides; uranium; tetravalent; coordination chemistry

  • Lecture (Conference)
    Theory Frontiers in Actinide Sciences, 02.-05.02.2020, Santa Fe, USA
  • Invited lecture (Conferences)
    XIIIth Workshop on Modern Methods in Quantum Chemistry, 02.-05.03.2020, Mariapfarr, Österreich

Permalink: https://www.hzdr.de/publications/Publ-31745
Publ.-Id: 31745


Multisystem combined uranium resistance mechanisms and bioremediation potential of Stenotrophomonas bentonitica BII-R7: Transcriptomics and microscopic study

Pinel-Cabello, M.; Jroundi, F.; Lopez Fernandez, M.; Geffers, R.; Jarek, M.; Jauregui, R.; Link, A.; Vílchez-Vargas, R.; Merroun, M. L.

The potential use of microorganisms in the bioremediation of U pollution has been extensively described.
However, a lack of knowledge on molecular resistance mechanisms has become a challenge for the use of these technologies. We reported on the transcriptomic and microscopic response of Stenotrophomonas bentonitica BII-R7 exposed to 100 and 250 μM of U. Results showed that exposure to 100 μM displayed up-regulation of 185 and 148 genes during the lag and exponential phases, respectively, whereas 143 and 194 were down-regulated, out of 3786 genes (>1.5-fold change). Exposure to 250 μM of U showed up-regulation of 68 genes and down-regulation of 290 during the lag phase. Genes involved in cell wall and membrane protein synthesis, efflux systems and phosphatases were up-regulated under all conditions tested. Microscopic observations evidenced the formation of U-phosphate minerals at membrane and extracellular levels. Thus, a biphasic process is likely to occur: the increased cell wall would promote the biosorption of U to the cell surface and its precipitation as U-phosphate minerals enhanced by phosphatases. Transport systems would prevent U accumulation in the cytoplasm. These findings contribute to an understanding of how microbes cope with U toxicity, thus allowing for the development of efficient bioremediation strategies.

Permalink: https://www.hzdr.de/publications/Publ-31740
Publ.-Id: 31740


Message from the Guest Editor of the 17th Multiphase Flow Conference Special Issue

Lucas, D.

Selected contributions of the 17th Multiphase Flow Conference at HZDR were published in a special issue of the Open Access Journal Experimental and Computational Multiphase Flow. In this contribution an overview on the conference and a short introduction to the single papers is given.

Keywords: multiphase flow; conference

  • Open Access Logo Abstract in refereed journal
    Experimental and Computational Multiphase Flow 3(2021)3, 137-138
    DOI: 10.1007/s42757-020-0087-x

Permalink: https://www.hzdr.de/publications/Publ-31735
Publ.-Id: 31735


Data for: Bonding Trends in Tetravalent Th–Pu Monosalen Complexes

Radoske, T.; März, J.; Patzschke, M.; Kaden, P.; Walter, O.; Schmidt, M.; Stumpf, T.

[AnCl2(salen)(Pyx)2] (H2salen=N,N′‐bis(salicylidene)ethylenediamine; Pyx=pyridine, 4‐methylpyridine, 3,5‐dimethylpyridine) + An(IV) with An=Th, U, Np, and Pu.

EA data, QC calculation results, NMR spectra and data analysis.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-09
    DOI: 10.14278/rodare.585

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31730
Publ.-Id: 31730


Quantification of the Inconvenient Truths about the Circular Economy (CE) Digital Twinning of Very Large Systems

Bartie, N. J.; Reuter, M.

We discuss the limitations to material flows from recycling in the circular economy, using as a case the simulation-based analysis of the CdTe Photovoltaic cells. It is important to use a simulation basis for the analysis, since this permits the quantification of all material losses both in terms of exergy and energy simultaneously i.e. 1st and 2nd law of thermodynamics. Harmonizing this with the power supply flowing into the system and minimizing energy usage as well as exergy losses will maximize the resource efficiency.

  • Open Access Logo Contribution to external collection
    Dagmar Boedicker, Sebastian Jekutsch, Dietrich Meyer-Ebrecht: FIfF-Kommunikation 3/2020 Technologie und Ökologie, Bremen: FIfF e.V., 2020, 0938-3476, 43-48

Permalink: https://www.hzdr.de/publications/Publ-31726
Publ.-Id: 31726


Convection in Liquid Metal Batteries

Weier, T.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Weber, N.

The quest for renewable energy sources entails an increasingly intermittent electricity supply.
Transmission grid updates can only partially account for balancing the resulting variations and large-scale stationary storage will gain importance in future energy landscapes dominated by volatile sources.
Today’s battery technologies were, with the notable exception of redox-flow batteries, mainly designed for and driven by mobile applications. Those prioritize properties (energy density, power rating) that are less important for stationary storage. Thus, battery technologies developed from the ground up to meet the needs of stationary storage have the potential to much better address the specifics of huge capacity installations.
Liquid metal batteries (LMBs) are a new technology for grid-scale energy storage. They consist of all liquid cells that operate with liquid metals as electrodes and molten salts as electrolytes. The liquids separate into three stably stratified layers by virtue of density and mutual immiscibility. This conceptually very simple and self-assembling structure has the unique advantage to allow for an easy scale-up at the cell level: single-cell cross sections can potentially reach several square-meters. Such cell sizes enable highly favourable and otherwise unattainable ratios of active to construction material because of the cubic scaling (volume) of the former and the quadratic scaling (surface) of the latter. The total costs should therefore largely be determined by those of the active materials.
The talk will start with a general introduction to LMBs and then focus on the fluid mechanics in these devices. Electric currents, magnetic fields, and heat and mass transfer are tightly coupled with the cells’ electrochemistry. First a number of fluid dynamic instabilities will be discussed in relation to operational safety. The remainder of the talk will deal with transport phenomena in the positive electrode. While transport in most modern battery systems is typically dominated by diffusion and migration in micrometer-scale liquid layers and solids, convection - with exception of the aforementioned redox-flow batteries - rarely plays a role. This is in stark contrast to LMBs were mediated by the fully liquid interior fluid flow can be driven by various mechanisms. The influence of solutal convection on the cycling behavior of a cell will be demonstrated. Electromagnetically induced convection can be used to improve mixing thereby mitigating diffusion overpotentials.

  • Invited lecture (Conferences) (Online presentation)
    Liquid Metal Technologies, 20.11.2020, Morelia, Mexiko

Permalink: https://www.hzdr.de/publications/Publ-31723
Publ.-Id: 31723


Accurate determination of quasi-particle electronic and optical spectra of anatase titanium dioxide

Sruthil Lal, S. B.; Devaraj, M.; Posselt, M.; Sharan, A.

The electronic structure and quasi-particle absorption spectra of anatase titanium dioxide has been calculated by employing state of the art density functional theory(DFT) and Many-Body Perturbation Theory methods(MBPT) within the framework of Hybrid Density Functional(HSE). GW methods are used in combination with Bethe-Salpeter Equation (BSE) to determine the Quasi Particle energy levels and the role of excitons in optical absorption spectra. Accurate optical and electronic band gap are determined from these methods. In addition to it an analysis of charge redistribution within the anatase unit cell is also presented within the PBE - DFT to analyze the orbital hybridization patterns and the character of chemical bonds.

Keywords: Anatase Titanium Oxide; Density Functional Theory; Electronic structure; Optical Spectra

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Permalink: https://www.hzdr.de/publications/Publ-31722
Publ.-Id: 31722


Tailoring Particle-enzyme Nanoconjugates for Biocatalysis at the Organic-organic Interface

Sun, Z.; Cai, M.; Hübner, R.; Ansorge-Schumacher, M. B.; Wu, C.

Nonaqueous Pickering emulsions (PEs) are a powerful platform for catalysis design, offering both a large interface contact and a preferable environment for water-sensitive synthesis. However, up to now, little progress has been made to incorporate insoluble enzymes into the nonaqueous system for biotransformation. Herein, we present biocatalytically active nonaqueous PEs, stabilized by particle-enzyme nanoconjugates, for the fast transesterification and esterification, and eventually for biodiesel synthesis. Our nanoconjugates are the hybrid biocatalysts tailor-made by loading hydrophilic Candida antarctica lipase B onto hydrophobic silica nanoparticles, resulting in not only catalytically active but highly amphiphilic particles for stabilization of a methanol-decane emulsion. The enzyme activity in these PEs is significantly enhanced, ca. 375-time higher than in the nonaqueous biphasic control. Moreover, the PEs can be multiply reused without significant loss of enzyme performance. With this proof‐of‐concept, we reasonably expect that our system can be expanded for many advanced syntheses using different enzymes in the future.

Keywords: biphasic biocatalysis; nonaqueous Pickering emulsions; solvent-free reactions; enzyme catalysis; nanoconjugates

Permalink: https://www.hzdr.de/publications/Publ-31721
Publ.-Id: 31721


Mechanosynthesis of polymer-stabilized lead bromide perovskites: insight into the formation and phase conversion of nanoparticles

Jiang, G.; Erdem, O.; Hübner, R.; Georgi, M.; Wei, W.; Fan, X.; Wang, J.; Demir, H. V.; Gaponik, N.

The application of polymers to replace oleylamine (OLA) and oleic acid (OA) as ligands for perovskite nanocrystals is an effective strategy to improve their stability and durability especially for the solution-based processing. Herein, we report a mechanosynthesis of lead bromide perovskite nanoparticles (NPs) stabilized by partially hydrolyzed poly(methyl methacrylate) (h-PMMA) and high-molecular-weight highly-branched poly(ethylenimine) (PEI-25K). The as-synthesized NP solutions exhibited green emission centered at 516 nm, possessing a narrow full-width at half-maximum of 17 nm and as high photoluminescence quantum yield (PL QY) as 85%, while showing excellent durability and resistance to polar solvents, e.g., methanol. The colloids of polymer-stabilized NPs were directly processable to form stable and strongly-emitting thin films and solids, making them attractive as gain media. Furthermore, the roles of h-PMMA and PEI-25K in the grinding process were studied in depth. The h-PMMA can form micelles in the grinding solvent of dichloromethane to act as size-regulating templates for the growth of NPs. The PEI-25K with large amounts of amino groups induced significant enrichment of PbBr2 in the reaction mixture, which in turn caused the formation of CsPb2Br5-mPbBr23-Cs4PbBr6-nCsBr NPs. The presence of CsPbBr3-Cs4PbBr6-nCsBr NPs was responsible for the high PL QY, as the Cs4PbBr6 phase with a wide energy bandgap can passivate the surface defects of the CsPbBr3 phase. This work describes a direct and facile mechanosynthesis of polymer-coordinated perovskite NPs and promotes in-depth understanding of the formation and phase conversion for perovskite NPs in the grinding process.

Keywords: lead bromide perovskites; mechanosynthesis; polymer ligands; polymer micelles; poly(ethyleneimine)-i

Permalink: https://www.hzdr.de/publications/Publ-31720
Publ.-Id: 31720


Nonlinear IR and THz Spectroscopy of Semiconductor Nanowires

Helm, M.; Fotev, I.; Balaghi, L.; Lang, D.; Rana, R.; Winnerl, S.; Schneider, H.; Dimakis, E.; Pashkin, A.

We report nonlinear charge-carrier response in GaAs/InGaAs core/shell nanowires that are driven by intense THz pulses. In the first experiment, half-cycle THz pulses emitted from an organic DSTMS crystal lead to a red-shift of the plasmon Peak indicating intervalley transfer of the electrons. In the second experiment, a single, highly electron doped nanowire is investigated by scattering near-field infrared microscopy using intense free-electron laser (FEL) pulses. Here the observed red shift of the mid-infrared plasma resonance depends on the pulse energy and can be explained by heating the electron system in the nonparabolic conduction band.

Keywords: nanowire; THz; infrared; free-electron laser; near-field microscopy; nonlinear

  • Invited lecture (Conferences) (Online presentation)
    45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2020), 08.-13.11.2020, Buffalo, USA

Permalink: https://www.hzdr.de/publications/Publ-31719
Publ.-Id: 31719


"CFD-grade" Experimental data for Solid-liquid Flow in a Stirred Tank

Sommer, A.-E.; Rox, H.; Eckert, K.; Shi, P.; Rzehak, R.

A solid-liquid flow in stirred tanks occurs frequently in different branches of process engineering where particles need to be suspended in a liquid. Computational Fluid Dynamics (CFD) simulations of such flow on industrial scales are feasible if the closure models implemented therein are appropriate. A large number of closure models exist, but due to a lack of data sources for validation, no systematic assessment of these different models has appeared so far. The present dataset aims to accumulate a comprehensive ''CFD-grade'' database based on experiments of the single-phase and two-phase flows in a standardized stirred tank with a diameter of 90 mm. The velocity fields of the liquid (deionized water) and, in the two-phase case, the solid phase were measured with Particle Image Velocimetry (PIV) and Particle Shadow Velocimetry (PSV), respectively. The experiments cover a range of parameters to achieve an extensive database. A narrow particle distribution of nearly neutrally buoyant particles (polyethylene spheres), as well as heavy particles (glass spheres) in the suspension, are considered over a wide range of particle diameter (63µm-500µm), solid volume fraction (0.025 vol% - 0.1vol%), as well as impeller rotation speed (650rpm - 1500rpm). The transient flow field on the plane midway between two baffles was recorded over 50 impeller rotations to achieve statistical significance. The time-averaged (resp. angle-resolved) mean and fluctuation velocities were then obtained by averaging the transient data in the laboratory frame of reference (resp. the frame of reference rotating with the impeller). The data is organized and analyzed as described in the corresponding journal publication "Solid-liquid Flow in Stirred Tanks: ”CFD-grade” Experimental Investigation".

Keywords: stirred tanks; solid-liquid flow; Particle Image Velocimetry (PIV); Particle Shadow Velocimetry (PSV); "Computational Fluid Dynamics (CFD)-grade" database

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-15
    DOI: 10.14278/rodare.263

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Permalink: https://www.hzdr.de/publications/Publ-31713
Publ.-Id: 31713


Broad Beam-Induced Fragmentation and Joining of Tungsten Oxide Nanorods: Implications for Nanodevice Fabrication and the Development of Fusion Reactors

Rajbhar, M. K.; Möller, W.; Satpati, B.; Manju, U.; Chaudhary, Y. S.; Chatterjee, S.

In this work, for the first time, fragmentation and joining of tungsten oxide (WO3) nanorods induced by a broad ion beam are reported. Although at low energy (5 keV) and moderate ion fluence, nanorods fragment into smaller pieces along the length, at higher ion energies (50-100 keV), a contrary process occurs, which leads to the joining of the nanorods. A state-of-the-art ion-solid interaction simulation, namely, TRI3DYN, has been invoked to explore the possible mechanisms that reveal subtle contributions of surface defects, ion-beam mixing, and sputtering. High-resolution electron microscopy, photoluminescence study, and X-ray photoelectron spectroscopy support the observed results and proposed mechanisms. Such modifications have interesting effects on the electrical conductivity of the nanorod assembly. The change in sample color upon ion irradiation from initial white to yellow, light blue, deep blue, light green, and cyan shows an excellent and reversible chromatic response of tungsten oxide nanorods to irradiation. Such a property can be exploited to fabricate radiation sensors. The fragmentation and joining at different energy scales have essential implications in nanodevice fabrication through the bottom-up approach as well as for the development of fusion reactors.

Keywords: electrical conductivity; fusion reactor material; ion irradiation; nanofragmentation; nanojoining; radiation sensor; tungsten oxide nanorods; wettability

Permalink: https://www.hzdr.de/publications/Publ-31710
Publ.-Id: 31710


A Molecular Octafluoridoneptunate(IV) anion in (NH₄)₄[NpF₈] and Theoretical Investigations of the [MF₈]₄-System (M = Th - Bk)

Scheibe, B.; Patzschke, M.; März, J.; Conrad, M.; Kraus, F.

Olive-green single crystals of ammonium octafluoridoneptunate(IV), (NH₄)₄[NpF₈], were obtained by converting NpO₂ to a green neptunium tetrafluoride hydrate with hydrofluoric acid and subsequent treatment of the fluoride with an aqueous NH₄F solution. The crystal structure of the compound was determined by single-crystal X ray diffraction and observed to be isotypic to the uranium analogue. In (NH₄)₄[NpF₈], molecular [NpF₈]⁴‾ anions, which can either be described as a distorted square-antiprism or a bicapped trigonal prism, are present which are bound to the NH₄⁺ ions via N−H∙∙∙F hydrogen bonds. Quantum-chemical calculations of [MF₈]⁴‾ anions show that the M−F bonds are highly ionic and the energy differences between different ligand arrangements likely can be overcome by lattice energies of different crystal structures in the solid state.

Keywords: actinide; density functional calculations; neptunium; fluorine; single-crystal X-ray diffraction

Permalink: https://www.hzdr.de/publications/Publ-31705
Publ.-Id: 31705


HIM FIBID dataset for Superconducting properties of in-plane W-C nanowires grown by He+ Focused Ion Beam Induced Deposition

Hlawacek, G.

HIM images and NPVE dataset created during the preparation of the W(CO)6 nanowires.

Keywords: helium ion microscopy; focused ion beam induced deposition

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-11
    DOI: 10.14278/rodare.581
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31704
Publ.-Id: 31704


Superconducting properties of in-plane W-C nanowires grown by He+ Focused Ion Beam Induced Deposition

Orús, P.; Córdoba, R.; Hlawacek, G.; de Teresa, J. M.

Focused Ion Beam Induced Deposition (FIBID) is a nanopatterning technique that makes use of a focused beam of charged ions to decompose a gaseous precursor. So far, the flexible patterning capabilities of FIBID have been widely exploited in the fabrication of superconducting nanostructures, using the W(CO) 6 precursor mostly in combination with a focused beam of Ga+ ions. Here, the fabrication and characterization of superconducting in-plane tungsten-carbon (W-C) nanostructures by He+ FIBID of the W(CO)6 precursor is reported. A virtually unattainable for Ga+ FIBID patterning resolution of 10 nm has been achieved. When the nanowires are patterned with widths of 20 nm and above, the deposited material is superconducting below 3.5 – 4 K. In addition, 60 and 90 nm-wide nanostructures have been found to sustain long-range controlled non-local superconducting vortex transfer along 3 μm. Overall, these findings strengthen the capabilities of He+ FIBID of W-C in the growth and patterning of in-plane superconducting nanodevices.

Keywords: superconductivity; Helium Ion Microscopy; FIBID; nanowires; vortexdynamics; electrical transport properties

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-31703
Publ.-Id: 31703


Evolution of cast iron- and copper- corrosion in "400 day-bentonite-microcosms"

Sushko, V.; Dressler, M.; Neubert, T.; Kühn, L.; Cherkouk, A.; Schierz, A.; Matschiavelli, N.

Copper and cast iron are potential materials for the storage canisters of high-level radioactive waste. We designed slurry-experiments for analyzing the microbial influence on the corrosion process of these metals. These slurry experiments contain the Bavarian B25 bentonite, synthetic Opalinus Clay pore water or diluted cap rock solution as well as copper- or cast iron plates in various combinations. During an incubation time of 400 days under anaerobic conditions at 37 °C cast iron plates corrode very fast. The respective metal surfaces show the formation of iron oxides and –carbonates which could form a passivating film that protects the cast iron from further corrosion.

  • Open Access Logo Lecture (Conference) (Online presentation)
    iCross annual meeting 2020, 25.-26.11.2020, Dresden-Webinar, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31702
Publ.-Id: 31702


PIConGPU setup: PWFA simulations

Pausch, R.; Debus, A.; Steiniger, K.; Widera, R.

This is the PIConGPU source code and setup files for generating PWFA simulations. This setup was used to study wake elongation.

Keywords: PIConGPU, PWFA

  • Software in the HZDR data repository RODARE
    Publication date: 2020-11-10
    DOI: 10.14278/rodare.579
    License: GPL-3.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31697
Publ.-Id: 31697


Influence of precursor thin-film quality on the structural properties of large-area MoS2 films grown by sulfurization of MoO3 on c-sapphire

Spanková, M.; Sojková, M.; Dobrocka, E.; Hutár, P.; Bodík, M.; Munnik, F.; Hulman, M.; Chromik, S.

In recent years, molybdenum disulfide (MoS2) has been investigated due to its unique electronic, optical, and mechanical properties with a variety of applications. Sulfurization of pre-deposited MoO3 layers is one of the methods of the preparation of large-area MoS2 thin films. The MoO3 layers have been grown on c-sapphire substrates, using two different techniques (rf sputtering, pulsed laser deposition). The films were subsequently annealed in vapors of sulfur at high temperatures what converted them to MoS2 films. The quality of MoS2 is strongly influenced by the properties of the precursor MoO3 layers. The pre-deposited MoO3, as well as the sulfurized MoS2, have been characterized by several techniques including Raman, Rutherford backscattering spectroscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. Here we compare two types of MoS2 films prepared from different MoO3 layers to determine the most suitable MoO3 layer properties providing good quality MoS2 films for future applications.

Keywords: Molybdenum disulfide; Sulfurization; Sputtering; Pulsed laser deposition; Structural properties

Permalink: https://www.hzdr.de/publications/Publ-31693
Publ.-Id: 31693


Diffraction techniques in nuclear materials

Bergner, F.

The presentation is aimed at introducing diffraction techniques and their applications in the field of structural nuclear materials. After a brief introduction, three selected experimental techniques are presented in more detail. These are X-ray line profile analysis (XLPA), electron backscatter diffraction (EBSD) and small-angle neutron scattering (SANS). XLPA is applied to derive microstructure parameters such as crystallite size, dislocation density and twin probability of a nanostructured high-entropy alloy processed by means of high pressure torsion. EBSD is shown to be useful for the characterization of the bainitic microstructure in terms of subunits of the prior austenite grains and their orientation relationship with the parent phase. As an example for the application of SANS, the effects of neutron flux and neutron fluence on the volume fraction and mean size of irradiation-induced solue atom clusters are characterized.

Keywords: Diffraction; Scattering; Nuclear materials; Irradiation effects

  • Invited lecture (Conferences) (Online presentation)
    European School on Nuclear Material Science, 09.-13.11.2020, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-31692
Publ.-Id: 31692


Frequency- and magnetic-field-dependent properties of ordered magnetic nanoparticle arrangements

Neugebauer, N.; Hache, T.; Elm, M.; Hofmann, D. M.; Heiliger, C.; Schultheiß, H.; Klar, P. J.

We present a frequency and magnetic field dependent investigation of ordered arrangements of 20 nm magnetic
nanoparticles (MNPs) consisting of magnetite (Fe3O4) by employing micro Brillouin light scattering
microscopy. We utilized electron beam lithography to prepare hexagonally arranged, circularly shaped MNPassemblies
consisting of a single layer of MNPs using a variant of the Langmuir-Blodgett technique. By
comparing the results with non-structured, layered superlattices of MNPs, further insight into the influence
of size and geometry of the arrangement on the collective properties is obtained. We show that at low static
external field strengths, two signals occur in frequency dependent measurements for both non-structured and
structured assemblies. Enlarging the static external field strength leads to a sharpening of the main signal,
while the satellite signal decreases in its intensity and increases in its linewidth. The occurrence of multiple
signals at low external field strengths is also confirmed by sweeping the static external field and keeping the
excitation frequency constant. Micromagnetic simulations unravel the origin of the different signals and their
dependence on the static external field strength, enabling an interpretation of the observed characteristics in
terms of different local environments of an MNPs forming the MNP assembly.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-09
    DOI: 10.14278/rodare.577
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31690
Publ.-Id: 31690


A New Highly Anisotropic Rh-Based Heusler Compound for Magnetic Recording

He, Y.; Fecher, G. H.; Fu, C.; Pan, Y.; Manna, K.; Kroder, J.; Jha, A.; Wang, X.; Hu, Z.; Agrestini, S.; Herrero-Martin, J.; Valvidares, M.; Scurschii, I.; Schnelle, W.; Stamenov, P.; Borrmann, H.; Tjeng, L. H.; Schaefer, R.; Parkin, S. S. P.; Coey, J. M. D.; Felser, C.

The development of high-density magnetic recording media is limited by superparamagnetism in very small ferromagnetic crystals. Hard magnetic materials with strong perpendicular anisotropy offer stability and high recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted magnetic recording was developed, rapidly heating the media to the Curie temperature Tc before writing, followed by rapid cooling. Requirements are a suitable Tc, coupled with anisotropic thermal conductivity and hard magnetic properties. Here, Rh2CoSb is introduced as a new hard magnet with potential for thin-film magnetic recording. A magnetocrystalline anisotropy of 3.6 MJ m−3 is combined with a saturation magnetization of μ0Ms = 0.52 T at 2 K (2.2 MJ m−3 and 0.44 T at room temperature). The magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μB on Co, which is hybridized with neighboring Rh atoms with a large spin–orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its Tc of 450 K, together with a thermal conductivity of 20 W m−1 K−1, make Rh2CoSb a candidate for the development of heat-assisted writing with a recording density in excess of 10 Tb in.−2.

Permalink: https://www.hzdr.de/publications/Publ-31685
Publ.-Id: 31685


Rare earth minerals and rare-earth mining

Lorenz, T.; Bertau, M.; Möckel, R.

The book chapter is about the geology of rare earth elements, their mineral carrier as well as secondary raw materials.

  • Book chapter
    Prof. Dr. Rainer Pöttgen, Prof. Dr. Christian Strassert, Prof. Dr. Thomas Jüstel: Rare Earth Chemistry, Berlin/Boston: Walter de Gruyter, 2020, 978-3110653601, 15-36
    DOI: 10.1515/9783110654929-002

Permalink: https://www.hzdr.de/publications/Publ-31683
Publ.-Id: 31683


Nanoparticle emission by electronic sputtering of CaF2 single crystals

Alencar, I.; Hatori, M.; Marmitt, G. G.; Trombini, H.; Grande, P. L.; Dias, J. F.; Papaléo, R. M.; Mücklich, A.; Assmann, W.; Toulemonde, M.; Trautmann, C.

Material sputtered from CaF2 single crystals by 180 MeV Au ions impinging at different incidence angles were collected on high-purity amorphous C-coated Cu grids and Si100 wafer catcher surfaces over a broad angular range. These catcher surfaces were characterized complementary by transmission electron microscopy, atomic force microscopy and medium energy ion scattering, revealing the presence of a distribution of partially buried CaF2 nanoparticles in conjunction to a thin layer of deposited CaF2 material. Particle size distributions do not follow simple power laws and depend on the angles of ion incidence and particle detection. It is shown that the particle ejection is directly related to the jet-like component of sputtering, previously observed in ionic crystals, contributing significantly to the total yield. This contribution enhances as the impinging ions approach grazing incidence. Possible scenarios for the emission of particles are discussed in light of these observations.

Keywords: Atomic force microscopyCatcher technique; Nanoparticle; Medium energy ion scattering; Electronic sputtering; Swift heavy ions; Transmission electron microscopy

Permalink: https://www.hzdr.de/publications/Publ-31682
Publ.-Id: 31682


Voltage‐driven motion of nitrogen ions: a new paradigm for magneto‐ionics

de Rojas, J.; Quintana, A.; Lopeandia, A.; Salguero, J.; Muñiz, B.; Ibrahim, F.; Chshiev, M.; Nicolenco, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Sireus, V.; Abad, L.; Jensen, C.; Liu, K.; Nogues, J.; Costa-Krämer, J.; Sort, J.; Menéndez, E.

Magneto‐ionics, understood as voltage‐driven ion transport in magnetic materials, has largely relied on controlled migration of oxygen ions. Here, we demonstrate room‐temperature voltagedriven nitrogen transport (i.e., nitrogen magneto‐ionics) by electrolyte‐gating of a CoN film.
Nitrogen magneto‐ionics in CoN is compared to oxygen magneto‐ionics in Co3O4. Both materials are nanocrystalline (face‐centered‐cubic structure) and show reversible voltage‐driven ON‐OFF ferromagnetism. In contrast to oxygen, nitrogen transport occurs uniformly creating a plane‐wavelike migration front, without assistance of diffusion channels. Remarkably, nitrogen magnetoionics requires lower threshold voltages and exhibits enhanced rates and cyclability. This is due to the lower activation energy for ion diffusion and the lower electronegativity of nitrogen compared to oxygen. These results may open new avenues in applications such as brain‐inspired computing or iontronics in general.

Keywords: positron annihilation spectroscopy; magneto-ionics; positron annihilation lifetime spectroscopy; defetcs; nitrogen; Co

Permalink: https://www.hzdr.de/publications/Publ-31678
Publ.-Id: 31678


The dithiol-dithione tautomerism of 2,3-pyrazinedithiol in the synthesis of copper and silver coordination compounds

Henfling, S.; Kempt, R.; Klose, J.; Kuc, A. B.; Kersting, B.; Krautscheid, H.

A promising strategy for new electrically conductive coordination polymers is the combination of d10 metal ions, which tolerate short metal···metal distances, with dithiolene linkers, known for their “non-innocent” redox behavior. This study explores the coordination chemistry of 2,3-pyrazinedithiol (H2pdt) towards Cu+ and Ag+ ions, highlighting similarities and differences. The synthetic approach, starting with the fully protonated ligand, allowed the isolation of a homoleptic bis(dithiolene) complex with formal CuI atoms, [Cu(H2pdt)2]Cl (1). This complex was further transformed to a one-dimensional coordination polymer with short metal···metal distances, 1D[Cu(Hpdt)] (2Cu). The larger Ag+ ion directly built up a very similar coordination polymer 1D[Ag(Hpdt)] (2Ag), without any appearance of an intermediate metal complex. The coordination polymer 1D[Cu(H2pdt)I] (4), like complex 1, bears fully protonated H2pdt ligands in their dithione form. Upon heating, both compounds underwent auto-oxidation coupled with a dehydrogenation of the ligand to form the open shell neutral copper(II) complex [Cu(Hpdt)2] (3) and the coordination polymer 1D[Cu2I2(Hpdt)(H2pdt)] (5), respectively. For all presented compounds, crystal structures are discussed in-depth. Furthermore, properties of 1, 3, as well as of the three one-dimensional coordination polymers 2Ag, 2Cu and 4, were investigated by UV-Vis-NIR spectroscopy, cyclic voltammetry, and variable temperature magnetic susceptibility, and DC-conductivity measurements. The experimental results are compared and discussed with the aid of DFT simulations.

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  • Secondary publication expected from 22.10.2021

Permalink: https://www.hzdr.de/publications/Publ-31674
Publ.-Id: 31674


Asphericity of tumor FDG uptake in non-small cell lung cancer: Reproducibility and implications for harmonization in multicenter studies

Rogasch, J.; Furth, C.; Bluemel, S.; Radojewski, P.; Amthauer, H.; Hofheinz, F.

Background

Asphericity (ASP) of the primary tumor’s metabolic tumor volume (MTV) in FDG-PET/CT is independently predictive for survival in patients with non-small cell lung cancer (NSCLC). However, comparability between PET systems may be limited. Therefore, reproducibility of ASP was evaluated at varying image reconstruction and acquisition times to assess feasibility of ASP assessment in multicenter studies.

Methods

This is a retrospective study of 50 patients with NSCLC (female 20; median age 69 years) undergoing pretherapeutic FDG-PET/CT (median 3.7 MBq/kg; 180 s/bed position). Reconstruction used OSEM with TOF4/16 (iterations 4; subsets 16; in-plane filter 2.0, 6.4 or 9.5 mm), TOF4/8 (4 it; 8 ss; filter 2.0/6.0/9.5 mm), PSF + TOF2/17 (2 it; 17 ss; filter 2.0/7.0/10.0 mm) or Bayesian-penalized likelihood (Q.Clear; beta, 600/1750/4000). Resulting reconstructed spatial resolution (FWHM) was determined from hot sphere inserts of a NEMA IEC phantom. Data with approx. 5-mm FWHM were retrospectively smoothed to achieve 7-mm FWHM. List mode data were rebinned for acquisition times of 120/90/60 s. Threshold-based delineation of primary tumor MTV was followed by evaluation of relative ASP/SUVmax/MTV differences between datasets and resulting proportions of discordantly classified cases.

Results

Reconstructed resolution for narrow/medium/wide in-plane filter (or low/medium/high beta) was approx. 5/7/9 mm FWHM. Comparing different pairs of reconstructed resolution between TOF4/8, PSF + TOF2/17, Q.Clear and the reference algorithm TOF4/16, ASP differences was lowest at FWHM of 7 versus 7 mm. Proportions of discordant cases (ASP > 19.5% vs. ≤ 19.5%) were also lowest at 7 mm (TOF4/8, 2%; PSF + TOF2/17, 4%; Q.Clear, 10%). Smoothing of 5-mm data to 7-mm FWHM significantly reduced discordant cases (TOF4/8, 38% reduced to 2%; PSF + TOF2/17, 12% to 4%; Q.Clear, 10% to 6%), resulting in proportions comparable to original 7-mm data. Shorter acquisition time only increased proportions of discordant cases at < 90 s.

Conclusions

ASP differences were mainly determined by reconstructed spatial resolution, and multicenter studies should aim at comparable FWHM (e.g., 7 mm; determined by in-plane filter width). This reduces discordant cases (high vs. low ASP) to an acceptable proportion for TOF and PSF + TOF of < 5% (Q.Clear: 10%). Data with better resolution (i.e., lower FWHM) could be retrospectively smoothed to the desired FWHM, resulting in a comparable number of discordant cases.

Permalink: https://www.hzdr.de/publications/Publ-31672
Publ.-Id: 31672


Tailoring magnetocaloric effect in all- d -metal Ni-Co-Mn-Ti Heusler alloys: a combined experimental and theoretical study

Taubel, A.; Beckmann, B.; Pfeuffer, L.; Fortunato, N.; Scheibel, F.; Ener, S.; Gottschall, T.; Skokov, K. P.; Zhang, H.; Gutfleisch, O.

Novel Ni-Co-Mn-Ti all- d -metal Heusler alloys are exciting due to large multicaloric effects combined with enhanced mechanical properties. An optimized heat treatment for a series of these compounds leads to very sharp phase transitions in bulk alloys with isothermal entropy changes of up to 38 J kg−1 K−1 for a magnetic field change of 2 T. The differences of as-cast and annealed samples are analyzed by investigating microstructure and phase transitions in detail by optical microscopy. We identify different grain structures as well as stoichiometric (in)homogenieties as reasons for differently sharp martensitic transitions after ideal and non-ideal annealing. We develop alloy design rules for tuning the magnetostructural phase transition and evaluate specifically the sensitivity of the transition temperature towards the externally applied magnetic fields (dTt0dH) by analyzing the different stoichiometries. We then set up a phase diagram including martensitic transition temperatures and austenite Curie temperatures depending on the e/a ratio for varying Co and Ti content. The evolution of the Curie temperature with changing stoi- chiometry is compared to other Heusler systems. Density Functional Theory calculations reveal a correlation of TC with the stoichiometry as well as with the order state of the austenite. This combined approach of experiment and theory allows for an efficient development of new systems towards promising magnetocaloric properties. Direct adiabatic temperature change measurements show here the largest value of -4 K in a magnetic field change of 1.93 T for Ni35Co15Mn37Ti13.

Permalink: https://www.hzdr.de/publications/Publ-31670
Publ.-Id: 31670


Photo-neutron cross-section of natDy in the bremsstrahlung end-point energies of 12, 14, 16, 65, and 75 MeV

Naik, H.; Kim, G. N.; Schwengner, R.; Wooyoung, J.; Hien, N. T.; Kim, K.; Shin, S. G.; Kye, Y.; Junghans, A.; Wagner, A.; Cho, M.-H.

The flux-weighted average cross-sections of natDy(γ, xn)159,157,155Dy reactions were measured at the bremsstrahlung end-point energies of 12, 14, 16, 65 and 75 MeV with the activation and off-line γ-ray spectrometric technique using the 20 MeV Electron Linac for beams with high Brilliance and low Emittance (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany and the 100 MeV electron linac at the Pohang Accelerator Laboratory, Korea. The natDy(γ, xn)157,155Dy reaction cross sections as a function of photon energy were also calculated theoretically using TALYS 1.9 code. Then the flux-weighted average values at different end-point energies were obtained based on the theoretical values of mono-energetic photons. These values were compared with the flux-weighted values of present work and are found to be in general agreement. It was also found that the experimental and theoretical formation cross sections of 159Dy, 157Dy and 155Dy from the natDy(γ, xn) reactions increased from their respective threshold values to a certain energy where other reaction channels opened. After reaching a maximum value, the individual reaction cross-sections slowly decreased with the increase of the bremsstrahlung energy due to the initiation of other competing reactions at higher energy, which indicates the impact of the excitation energy. However, the production cross sections of 157Dy and 155Dy from the natDy(γ, xn) reactions slightly increase in between and then decreased slowly with bremsstrahlung energy, which is due to the contributing reactions of higher mass isotopes.

Keywords: Photonuclear reactions; photoabsorption cross section; photodissociation

Permalink: https://www.hzdr.de/publications/Publ-31669
Publ.-Id: 31669


Dynamic properties of the warm dense electron gas based on ab initio path integral Monte Carlo simulations

Hamann, P.; Dornheim, T.; Vorberger, J.; Moldabekov, Z.; Bonitz, M.

There is growing interest in warm dense matter (WDM), an exotic state on the border between condensed matter and plasmas. Due to the simultaneous importance of quantum and correlation effects, WDM is complicated to treat theoretically. A key role has been played by ab initio path integral Monte Carlo (PIMC) simulations, and recently extensive results for thermodynamic quantities have been obtained. The first extension of PIMC simulations to the dynamic structure factor of the uniform electron gas was reported by Dornheim et al. [Phys. Rev. Lett. 121, 255001 (2018)]. This was based on an accurate reconstruction of the dynamic local field correction. Here we extend this concept to other dynamical quantities of the warm dense electron gas including the dynamic susceptibility, the dielectric function, and the conductivity.

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Permalink: https://www.hzdr.de/publications/Publ-31667
Publ.-Id: 31667


Ion energy-loss characteristics and friction in a free-electron gas at warm dense matter and nonideal dense plasma conditions

Moldabekov, Z.; Dornheim, T.; Bonitz, M.; Ramazanov, T.

We investigate the energy-loss characteristics of an ion in warm dense matter (WDM) and dense plasmas concentrating on the influence of electronic correlations. The basis for our analysis is a recently developed ab initio quantum Monte Carlo– (QMC) based machine learning representation of the static local field correction (LFC) [Dornheim et al., J. Chem. Phys. 151, 194104 (2019)], which provides an accurate description of the dynamical density response function of the electron gas at the considered parameters. We focus on the polarization-induced stopping power due to free electrons, the friction function, and the straggling rate. In addition, we compute the friction coefficient which constitutes a key quantity for the adequate Langevin dynamics simulation of ions. Considering typical experimental WDM parameters with partially degenerate electrons, we find that the friction coefficient is of the order of γ/ωpi=0.01, where ωpi is the ionic plasma frequency. This analysis is performed by comparing QMC-based data to results from the random-phase approximation (RPA), the Mermin dielectric function, and the Singwi-Tosi-Land-Sjölander (STLS) approximation. It is revealed that the widely used relaxation time approximation (Mermin dielectric function) has severe limitations regarding the description of the energy loss of ions in a correlated partially degenerate electrons gas. Moreover, by comparing QMC-based data with the results obtained using STLS, we find that the ion energy-loss properties are not sensitive to the inaccuracy of the static local field correction (LFC) at large wave numbers, k/kF>2 (with kF being the Fermi wave number), but that a correct description of the static LFC at k/kF≲1.5 is important.

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Permalink: https://www.hzdr.de/publications/Publ-31665
Publ.-Id: 31665


Path-integral Monte Carlo simulations of quantum dipole systems in traps: Superfluidity, quantum statistics, and structural properties

Dornheim, T.

We present extensive ab initio path-integral Monte Carlo (PIMC) simulations of two-dimensional quantum dipole few-body systems (2≤N≤7) in a harmonic confinement, taking into account both Bose- and Fermi-statistics. This allows us to study the nonclassical rotational inertia, which can lead to a negative superfluid fraction in the case of fermions [Phys. Rev. Lett. 112, 235301 (2014)]. Moreover, we study in detail the structural characteristics of such systems and are able to clearly resolve the impact of quantum statistics on density profiles and the respective shell structure. Further, we present results for a more advanced center-two-particle correlation function [Phys. Rev. E 91, 043104 (2015)], which allows detection of differences between Fermi and Bose systems even when they are almost absent in other observables like the density. Overall, we find that bosonic systems sensitively react to even small values of the dipole-dipole coupling strength, whereas such a weak interaction is effectively masked for fermions by the Pauli exclusion principle. In addition, the abnormal superfluid fraction for fermions is not reflected by the structural properties of the system, which are equal to the bosonic case even though the moments of inertia diverge from each other. Lastly, we have explored the possibility of fermionic PIMC simulations of quantum dipole systems despite the notorious fermion sign problem, which can be further extended in future investigations in this field.

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Permalink: https://www.hzdr.de/publications/Publ-31664
Publ.-Id: 31664


Restricted configuration path integral Monte Carlo

Yilmaz, A.; Hunger, K.; Dornheim, T.; Groth, S.; Bonitz, M.

Quantum Monte Carlo (QMC) belongs to the most accurate simulation techniques for quantum many-particle systems. However, for fermions, these simulations are hampered by the sign problem that prohibits simulations in the regime of strong degeneracy. The situation changed with the development of configuration path integral Monte Carlo (CPIMC) by Schoof et al. [Contrib. Plasma Phys. 51, 687 (2011)] that allowed for the first ab initio simulations for dense quantum plasmas [Schoof et al., Phys. Rev. Lett. 115, 130402 (2015)]. CPIMC also has a sign problem that occurs when the density is lowered, i.e., in a parameter range that is complementary to traditional QMC formulated in coordinate space. Thus, CPIMC simulations for the warm dense electron gas are limited to small values of the Brueckner parameter—the ratio of the interparticle distance to the Bohr radius—rs=r⎯⎯⎯/aB≲1
. In order to reach the regime of stronger coupling (lower density) with CPIMC, here we investigate additional restrictions on the Monte Carlo procedure. In particular, we introduce two different versions of “restricted CPIMC”—called RCPIMC and RCPIMC+—where certain sign changing Monte Carlo updates are being omitted. Interestingly, one of the methods (RCPIMC) has no sign problem at all, but it introduces a systematic error and is less accurate than RCPIMC+, which neglects only a smaller class of the Monte Carlo steps. Here, we report extensive simulations for the ferromagnetic uniform electron gas with which we investigate the properties and accuracy of RCPIMC and RCPIMC+. Furthermore, we establish the parameter range in the density–temperature plane where these simulations are both feasible and accurate. The conclusion is that RCPIMC and RCPIMC+ work best at temperatures in the range of Θ = kBT/EF ∼ 0.1…0.5, where EF is the Fermi energy, allowing to reach density parameters up to rs ∼ 3…5, thereby partially filling a gap left open by existing ab initio QMC methods.

Permalink: https://www.hzdr.de/publications/Publ-31663
Publ.-Id: 31663


Reconstruction of austenite grain boundaries in bainitic reactor pressure vessel steels by EBSD

Chekhonin, P.; Bergner, F.

The reconstruction of austenite grain boundaries in bainitic reactor pressure vessel (RPV) steels by means of electron backscatter diffraction (EBSD) was done on two examples. In the case of VVER-440 RPV steel the reconstruction works very well, while in JFL RPV steel the reconstruction is faulty due to the accented presence of low angle boundaries.

  • Lecture (Conference) (Online presentation)
    AK-Treffen Mikrostrukturcharakterisierung im REM, 22.10.2020, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-31662
Publ.-Id: 31662


Enhanced spin correlations in the Bose-Einstein condensate compound Sr3Cr2O8

Nomura, T.; Scurschii, I.; Quintero-Castro, D. L.; Zvyagin, A. A.; Suslov, A. V.; Gorbunov, D.; Yasin, S.; Wosnitza, J.; Kindo, K.; Islam, A. T. M. N.; Lake, B.; Kohama, Y.

Combined experimental and modeling studies of the magnetocaloric effect, ultrasound, and magnetostriction were performed on single-crystal samples of the spin-dimer system Sr3Cr2O8 in large magnetic fields to probe the spin-correlated regime in the proximity of the field-induced XY-type antiferromagnetic order also referred to as a Bose-Einstein condensate of magnons. The magnetocaloric effect, measured under adiabatic conditions, reveals details of the field-temperature (H, T ) phase diagram, a dome characterized by critical magnetic-fields Hc1 = 30.4, Hc2 = 62 T, and a single maximum ordering temperature Tmax(45 T) = 8 K. The sample temperature was observed to drop significantly as the magnetic field is increased, even for initial temperatures above Tmax, indicating a significantmagnetic entropy associated with the field-induced closure of the spin gap. The ultrasound and magnetostriction experiments probe the coupling between the lattice degrees of freedom and the magnetism in Sr3Cr2O. Our experimental results are qualitatively reproduced by a minimalistic phenomenological model of the exchange striction by which sound waves renormalize the effective exchange couplings.

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Permalink: https://www.hzdr.de/publications/Publ-31661
Publ.-Id: 31661


Strong anisotropy of the electron-phonon interaction in NbP probed by magnetoacoustic quantum oscillations

Schindler, C.; Gorbunov, D.; Zherlitsyn, S.; Galeski, S.; Schmidt, M.; Wosnitza, J.; Gooth, J.

In this study, we report on the observation of de Haas–van Alphen–type quantum oscillations (QOs) in the ultrasound velocity of NbP as well as “giant QOs” in the ultrasound attenuation in pulsed magnetic fields. The difference in the QO amplitude for different acoustic modes reveals a strong anisotropy of the effective deformation potential, which we estimate to be as high as 9 eV for certain parts of the Fermi surface. Furthermore, the natural filtering of QO frequencies and the tracing of the individual Landau levels to the quantum limit allows for a more detailed investigation of the Fermi surface of NbP, as was previously achieved by means of analyzing QOs observed in magnetization or electrical resistivity.

Permalink: https://www.hzdr.de/publications/Publ-31660
Publ.-Id: 31660


Detection of manufactured nanomaterials in complex environmental compartments – An expert review

Schymura, S.; Hildebrand, H.; Völker, D.; Schwirn, K.; Franke, K.; Fischer, C.

Manufactured nanomaterials (NMs) are materials in which 50% or more of the particles have one or more dimensions between 1 nm and 100 nm. These NMs show interesting properties. However, the same properties that motivate their use in applications are also reason for concern, as NMs can cause toxic reactions and have mobilities in the environment different from bulk materials of the same elements. Despite considerable scientific efforts, the selective detection of manufactured NMs in environmental compartments is still a very complex and challenging task. An expert review of the literature has been conducted to identify relevant methods for nanomaterial detection in complex media in the context of environmental monitoring and a need for action was concluded from the existing body of work.
A literature review was performed using predominantly “Web of Science”. More than 150 scientific publications which themselves refer to more than 10000 sources were evaluated concerning nanoparticle detection methods. The techniques identified through the literature review were evaluated for their capability to detect the relevant NM-related properties such as size, concentration, com- position, shape, etc. of arbitrary NMs in environmental samples.
Evaluating the relevant literature quickly led to the conclusion that while some detection methods will lend themselves more easily towards detection of NMs in a specific environmental compartment, there is no strictly compartment specific method. NMs can be detected with any of the different methods after application of suitable sample preparation techniques. Consequently, a generalized method for NM detection in environmental samples would consist of standardized sampling procedures followed by an extraction step that serves to largely remove the complex matrix followed by a size fractionation step which would then lead into a multi-method analysis depending on the desired information depth.
The need for action for the establishment of routine environmental monitoring of manufactured NMs is thus the development, validation and coupling of suitable extraction, pre-sorting and if necessary pre- concentration procedures, as well, as analysis techniques. One promising combined approach would consist of: CPE, AF4, MALS and sp-ICP-TOF-MS.

Keywords: nanoparticles; detection; environmental compartments

  • Poster (Online presentation)
    Nanosafe 2020, 16.-20.11.2020, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-31659
Publ.-Id: 31659


Assessing nanoparticle release from waste water treatment using radiolabeled nanoparticles

Schymura, S.; Hildebrand, H.; Neugebauer, M.; Lange, T.; Schneider, P.; Franke, K.

Waste water treatment plants (WWTPs) represent an important step in the life cycle of manufactured nanomaterials. A considerable amount of nanoparticles (NPs) that are released from consumer products will end up in WWTPs, so that WWTPs can both serve as a potential end of life point for these nanoparticles, as well as a point of reentry into the environment via the WWTP effluents. It is thus of utmost importance to accurately quantify the fate of manufactured nanomaterials in waste water treatment in order to assess the risk
We used the radiolabeling of nanoparticles to accurately quantify the distribution of nanoparticles between the effluents of a model waste water treatment plant. In order to achieve this TiO2 NP were radiolabeled with V-48 using proton irradiation at our cyclotron. Multi-wall carbon nanotubes (MWCNT) were radiolabeled with Be-7 via recoil at our cyclotron. CdSe/ZnS Quantum dots were radiolabeled with Zn-65 and Se-75 via radiosynthesis. The radiolabeled NPs were used in batch experiments and model waste water treatment plant experiments.
The radiolabeling allowed us to quantify NP distribution between sludge and water phase in the WWTP and in the WWTP effluents. A distribution of about 10000 : 1 between sludge-associated NPs and free NPs in water is reached in the WWTP already shortly after injection of the NPs. Thus the elimination of the NPs from the WWTP is mainly controlled by the removal of surplus sludge taking place every day of operation. The NPs are eliminated from the WWTP with a half-life of about 6 days reflecting the pre-set sludge age. After about 22 days of operation 10 % of the initial NPs remain in the WWTP. Approximately 1 % of the NPs leave the WWTP via the cleared waste water, mainly associated with non-sedimented sludge particles, such that only about 1 ‰ of the NPs leave the WWTP as free particles via the cleared water. An impact of the NPs on the clearing process, as monitored by chemical oxygen demand of the inflow vs. the outflow, was not observed.

Keywords: nanoparticles; waste water treatment; radiolabeling

  • Lecture (Conference) (Online presentation)
    Nanosafe 2020, 16.-20.11.2020, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-31658
Publ.-Id: 31658


Radiolabeling as a versatile tool in nanosafety research – accurate quantification in complex media

Schymura, S.; Hildebrand, H.; Rybkin, I.; Fricke, T.; Neugebauer, M.; Freyer, A.; Rijavec, T.; Lapanje, A.; Strok, M.; Lange, T.; Holzwarth, U.; Gibson, N.; Franke, K.

Accurate quantification of nanoparticles (NPs) in complex media remains a considerable challenge when assessing the risk that manufactured nanoparticles pose for humans and environment. The radiolabeling of nanoparticles is a valuable tool for conducting lab-studies with realistic systems and realistically low NP concentrations.
We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles. The labeling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [13/1419Ce]CeO2, [7Be]MWCNT, [64Cu]SiO2, [44/45Ti]TiO2, etc. for accurate quantification in complex media at environmentally relevant low concentrations.
The nanoparticles labeled by our methods can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary. The methods are adaptable for a wide range of other nanoparticles. The labeled particles have been successfully used in release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.

Keywords: Radiolabeling; Nanoparticles

  • Poster
    Nanosafe 2020, 16.-20.11.2020, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-31657
Publ.-Id: 31657


Series of Tetravalent Actinide Amidinates: Structure Determination and Bonding Analysis.

Kloditz, R.; Fichter, S.; Kaufmann, S.; Brunner, T. S.; Kaden, P.; Patzschke, M.; Stumpf, T.; Roesky, P. W.; Schmidt, M.; März, J.

NMR spectra for the complex series in the publication together with the xyz coordinates of the optimized complexes. An example input-file for ORCA v4.1.2 for the calculation of the wavefunction used for QTAIM is presented as well.

Keywords: actinides; NMR; DFT; QTAIM; NPA; coordination chemistry; transuranium

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-17
    DOI: 10.14278/rodare.517

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Permalink: https://www.hzdr.de/publications/Publ-31654
Publ.-Id: 31654


Data for: Spectral X-ray Computed Micro Tomography: 3-dimensional chemical imaging

Sittner, J.; Da Assuncao Godinho, J. R.; Renno, A.; Cnudde, V.; Boone, M.; de Schryver, T.; van Loo, D.; Merkulova, M.; Roine, A.; Liipo, J.

The files show the data we used for the publication.

Keywords: X-ray computed tomography; Spectral X-ray tomography; Photon counting detector; 3D imaging

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-22
    DOI: 10.14278/rodare.525
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31653
Publ.-Id: 31653


Are two-dimensional materials radiation tolerant?

Krasheninnikov, A.

Two-dimensional (2D) materials have many unique properties, which can be exploited in various applications. In particular, electronic devices based on 2D materials should ideally be suited for the operation in outer cosmic space due to their low weight, small size and low power consump- tion. This brings about the issue of their radiation hardness, or tolerance, which has recently been addressed in a number of studies. The results of these investigations are somewhat counterintu- itive: although one can naively expect that atomically thin structures should easily be destroyed by the beams of energetic particles, the devices made from 2D materials were reported to exhibit extraordinary radiation hardness. In this Focus article, an overview of the recent studies on the subject is given, followed by the discussion of the origin of the reported high tolerance, which is inherently related to the response of 2D materials, the systems with the reduced dimensionality, to irradiation. The analysis of the experimental and theoretical data on the behavior of 2D systems under irradiation indicates that although free-standing 2D materials can indeed be referred to as radiation resilient systems under irradiation conditions corresponding to the outer space, this is generally not the case, as the environment, e.g., the substrate, can strongly influence the radiation tolerance of 2D materials and devices based on these systems.

Keywords: 2D materials; irradiation; radiation tolerance

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  • Secondary publication expected from 18.09.2021

Permalink: https://www.hzdr.de/publications/Publ-31650
Publ.-Id: 31650


Influence of chemical zoning on sandstone calcite cement dissolution: The case of manganese and iron

Trindade Pedrosa, E.; Fischer, C.; Morales, L. F.; Rohlfs, R. D.; Luttge, A.

Chemical zoning of crystals is often found in nature. Crystal zoning can play a role in a mineral's thermodynamic stability and in its kinetic response in the presence of fluids. Dissolution experiments at far-from-equilibrium conditions were performed using a sandstone sample containing calcite cement crystal patches. The surface normal retreat of the calcite crystals was obtained by vertical scanning interferometry (VSI) in their natural position in the rock. Dissolution rate maps showed contrasting surface dissolution areas within the crystals, in the same locations where electron microprobe (EMP) maps showed the presence of manganese (Mn) and iron (Fe) substitutions for calcium in the calcite structure. Iron zoning was only identified in combination with manganese. Maximum registered manganese contents were 1.9(9) wt% and iron were 2(1) wt%. Manganese zoning of only 0.9(5) wt% resulted in around 40% lower dissolution rates than the adjacent pure calcite zones. The combination of both Mn and Fe cation substitutions resulted in one order of magnitude lower dissolution rates compared to pure calcite in the same sample. These results show that mineral zoning can significantly affect reaction rates, a parameter that needs better understanding for the improvement of kinetic geochemical models at the pore scale.

Keywords: Sandstone; Calcite; Dissolution; Zoning; Manganese; Iron

Permalink: https://www.hzdr.de/publications/Publ-31649
Publ.-Id: 31649


Dyke apertures record stress accumulation during sustained volcanism

Thiele, S. T.; Cruden, A. R.; Micklethwaite, S.; Köpping, J.; Bunger, A. P.

The feedback between dyke and sill intrusions and the evolution of stresses within volcanic systems is poorly understood, despite its importance for magma transport and volcano instability. Long-lived ocean island volcanoes are crosscut by thousands of dykes, which must be accommodated through a combination of flank slip and visco-elastic deformation. Flank slip is dominant in some volcanoes (e.g., Kilauea), but how intrusions are accommodated in other volcanic systems remains unknown. Here we apply digital mapping techniques to collect > 400,000 orientation and aperture measurements from 519 sheet intrusions within Volcán Taburiente (La Palma, Canary Islands, Spain) and investigate their emplacement and accommodation. We show that vertically ascending dykes were deflected to propagate laterally as they approached the surface of the volcano, forming a radial dyke swarm, and propose a visco-elastic model for their accommodation. Our model reproduces the measured dyke-aperture distribution and predicts that stress accumulates within densely intruded regions of the volcano, blocking subsequent dykes and causing eruptive activity to migrate. These results have significant implications for the organisation of magma transport within volcanic edifices, and the evolution and stability of long-lived volcanic systems.

Permalink: https://www.hzdr.de/publications/Publ-31648
Publ.-Id: 31648


High Performance Computing: ISC High Performance 2020 International Workshops

Jagode, H.; Anzt, H.; Juckeland, G.; Ltaief, H.

This book constitutes the refereed post-conference proceedings of 10 workshops held at the 35th International ISC High Performance 2020 Conference, in Frankfurt, Germany, in June 2020:
First Workshop on Compiler-assisted Correctness Checking and Performance Optimization for HPC (C3PO); First International Workshop on the Application of Machine Learning Techniques to Computational Fluid Dynamics Simulations and Analysis (CFDML); HPC I/O in the Data Center Workshop (HPC-IODC); First Workshop \Machine Learning on HPC Systems" (MLHPCS); First International Workshop on Monitoring and Data Analytics (MODA); 15th Workshop on Virtualization in High-Performance Cloud Computing (VHPC).

The 25 full papers included in this volume were carefully reviewed and selected. They cover all aspects of research, development, and application of large-scale, high performance experimental and commercial systems. Topics include high-performance computing (HPC), computer architecture and hardware, programming models, system software, performance analysis and modeling, compiler analysis and optimization techniques, software sustainability, scientific applications, deep learning.

Keywords: artificial intelligence; computer hardware; computer networks; computer science; computer systems; distributed computer systems; distributed systems; education; HPC; parallel architectures

Permalink: https://www.hzdr.de/publications/Publ-31647
Publ.-Id: 31647


The resource potential of mine waste – More than metal concentrations

Büttner, P.; Nühlen, J.; Engelhardt, J.

In the last decade, several national and European funding programs addressed the resource potential of mine wastes (including tailings and metallurgical slag dumps), with a clear focus on the development of new sources for critical raw materials (CRM). The European Commission defined CRMs as highly important for the European high tech industry. European and national resource strategies refer to this definition and include the development of new CRM sources as one of their main objectives. The German Federal Ministry for Research and Education (BMBF) funded the program “r3 –strategic metals and minerals – innovative technologies for resource efficiency” that started in 2012. The aim of the program was to ensure the domestic supply of strategically significant metals and minerals. Suitable projects had to act in the fields of recycling and substitution of raw materials as well as in the field of reduced material consumption. Urban mining and the evaluation of resource efficiency were further topics that suited the program. The Helmholtz Institute Freiberg for Resource Technology (HIF) and the Fraunhofer Institute for Environmental, Safety, and Energy Technology (UMSICHT) worked already together in different projects about mine waste characterization and resource extraction in r3.
The Helmholtz Institute Freiberg for Resource Technology pursues the objective of developing innovative technologies for the economy so that mineral and metalliferous raw materials become more available, undergo highly efficient processes and recycle in an environmentally
friendly manner. As a part of the national strategy for raw materials in 2011, the German government initiated the HIF. It is a constituent part of the Helmholtz-Zentrum Dresden-Rossendorf and works in close collaboration with TU Bergakademie Freiberg. The HIF is a core member of the European EIT RawMaterials network, having played a decisive role in its establishment. Fraunhofer UMSICHT is a pioneer for sustainable energy and raw materials management by supplying and transferring scientific results into companies, society and politics. The dedicated UMSICHT team researches and develops, together with partners, sustainable products, processes and services. Together with industry and public partners, such as the Geological Survey of Germany (BGR), UMSICHT and HIF founded the r³-mine-waste-cluster in order to determine a realistic mine waste
potential for Germany and give a reliable resource estimation for secondary raw materials. Nowadays, however, there is a political and public interest beyond the potential of valuable metals from mine wastes. After the catastrophic tailings accident in Vales Corrego do Feijão mine, Brazil, the social pressure to lower these risks raised on the mining industry, on the mine waste owners (e.g. states) and on the politics. With the new Global Industry Standard on Tailings Management a new set of guidelines was developed in order to avoid these accidents in the future. “The International Council
on Mining and Metals (ICMM), the United Nations Environment Programme (UNEP) and the Principles for Responsible Investment (PRI) share a commitment to the adoption of global best practices on tailings storage facilities. They have co-convened this global tailings review to establish an international standard.” Their environmental risks and at the same time their high potential as a source for (critical) raw materials make mine waste projects a complex exercise. There is a need for solutions that respect environmental, technical, civil and economic issues and provide holistic and sustainable approaches. In order to validating and adjusting different approaches, the HIF coordinates the recomine-alliance. Local stakeholders representing environmental, technical, scientific, governmental and civil institutions assemble in recomine for a development of holistic mine waste solutions for a worldwide application.

Keywords: re-mining; resources; HIF; tailings; mine waste; mining; CRM; slag dump; mine water; WIR!; r3; recomine; Freiberg; Network; Alliance; BMBF; holistic; remediation; sustainable

  • World of Mining - Surface & Underground 72(2020)5, 264-269

Permalink: https://www.hzdr.de/publications/Publ-31646
Publ.-Id: 31646


A FDG-PET radiomics signature detects esophageal squamous cell carcinoma patients who do not benefit from chemoradiation

Li, Y.; Beck, M.; Päßler, T.; Lili, C.; Wu, H.; Ha, D.; Amthauer, H.; Biebl, M.; Thuss-Patience, P.; Berger, J.; Stromberger, C.; Tinhofer, I.; Kruppa, J.; Budach, V.; Hofheinz, F.; Lin, Q.; Zschaeck, S.

Detection of patients with esophageal squamous cell carcinoma (ESCC) who do not benefit from standard chemoradiation (CRT) is an important medical need. Radiomics using 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising approach. In this retrospective study of 184 patients with locally advanced ESCC. 152 patients from one center were grouped into a training cohort (n = 100) and an internal validation cohort (n = 52). External validation was performed with 32 patients treated at a second center. Primary endpoint was disease-free survival (DFS), secondary endpoints were overall survival (OS) and local control (LC). FDG-PET radiomics features were selected by Lasso-Cox regression analyses and a separate radiomics signature was calculated for each endpoint. In the training cohort radiomics signatures containing up to four PET derived features were able to identify non-responders in regard of all endpoints (DFS p < 0.001, LC p = 0.003, OS p = 0.001). After successful internal validation of the cutoff values generated by the training cohort for DFS (p = 0.025) and OS (p = 0.002), external validation using these cutoffs was successful for DFS (p = 0.002) but not for the other investigated endpoints. These results suggest that pre-treatment FDG-PET features may be useful to detect patients who do not respond to CRT and could benefit from alternative treatment.

Permalink: https://www.hzdr.de/publications/Publ-31643
Publ.-Id: 31643


Dissolution of donor-vacancy clusters in heavily doped n-type germanium

Prucnal, S.; Liedke, M. O.; Wang, X.; Butterling, M.; Posselt, M.; Knoch, J.; Windgassen, H.; Hirschmann, E.; Berencen, Y.; Rebohle, L.; Wang, M.; Napoltani, E.; Frigerio, J.; Ballabio, A.; Isella, G.; Hübner, R.; Wagner, A.; Bracht, H.; Helm, M.; Zhou, S.

The n-type doping of Ge is a self-limiting process due to the formation of vacancy-donor complexes (DnV with n ≤ 4) that deactivate the donors. This work unambiguously demonstrates that the dissolution of the dominating P4V clusters in heavily phosphorus-doped Ge epilayers can be achieved by millisecond-flash lamp annealing at about 1050 K. The P4V cluster dissolution increases the carrier concentration by more than three-fold together with a suppression of phosphorus diffusion. Electrochemical capacitance-voltage measurements in conjunction with secondary ion mass spectrometry, positron annihilation lifetime spectroscopy and theoretical calculations enabled us to address and understand a fundamental problem that has hindered so far the full integration of Ge with complementary-metal-oxide-semiconductor technology.

Keywords: Ge; vacancies; doping; positron annihilation lifetime spectroscopy; flash lamp annealing

Permalink: https://www.hzdr.de/publications/Publ-31641
Publ.-Id: 31641


Magnetic-field-assisted electrodeposition towards micro- and nano-structured ferromagnetic layers

Huang, M.; Eckert, K.; Mutschke, G.

Micro- or nano-structured ferromagnetic layers often possess superior electrocatalytic properties but are difficult to manufacture in general. The present work investigates how a magnetic field can possibly support local cone growth on a planar electrode during electrodeposition, thus simplifying fabrication. Analytical and numerical studies were performed on conical structures of mm size to elaborate the influence of the magnetic forces caused by an electrode-normal external field. It is shown that, beside the Lorentz force studied earlier in the case of single cones [1], the magnetic gradient force enabled by the field alteration near the ferromagnetic cathode significantly supports cone growth. Detailed studies performed for sharp and flat single cones allow conclusions to be drawn on the support at different stages in the evolution of conical deformations. Furthermore, the influence from neighboring cones is studied with arrays of cones at varying distances apart. Nearby neighbors generally tend to mitigate the flow driven by the magnetic forces. Here, the support for cone growth originating from the magnetic gradient force is less heavily affected than that from the Lorentz force. Our results clearly show that the magnetic field has a beneficial effect on the growth of ferromagnetic conical structures, which could also be useful on the micro- and nanometer scales.

Keywords: metal electrodeposition; magnetic field; surface-structured electrode; Lorentz force; magnetic gradient force; numerical simulation

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  • Secondary publication expected from 30.10.2021

Permalink: https://www.hzdr.de/publications/Publ-31638
Publ.-Id: 31638


Data for: Scanning transmission imaging in the helium ion microscope using a microchannel plate with a delay line detector

Serralta Hurtado De Menezes, E.; Klingner, N.; de Castro, O.; Mousley, M.; Eswara, S.; Duarte Pinto, S.; Wirtz, T.; Hlawacek, G.

  A detection system based on a microchannel plate with a delay line readout structure has been developed to perform scanning transmission ion microscopy (STIM) in the helium ion microscope (HIM). This system is an improvement over other existing approaches since it combines the information of the scanning beam position on the sample with the position (scattering angle) and time of the transmission events. Various imaging modes such as bright and dark field or the direct image of the transmitted signal can be created by post-processing the collected STIM data. Furthermore, the detector has high spatial and time resolution, is sensitive to both ions and neutral particles over a wide energy range, and shows robustness against ion beam-induced damage. A special in-vacuum movable support gives the possibility of moving the detector vertically, placing the detector closer to the sample for the detection of high-angle scattering events, or moving it down to increase the angular resolution and distance for time-of-flight measurements. With this new system, we show composition-dependent contrast for amorphous materials and the contrast difference between small and high angle scattering signals. We also detect channeling related contrast on polycrystalline silicon, thallium chloride nanocrystals, and single crystalline silicon by comparing the signal transmitted at different directions for the same data set.

Keywords: helium ion microscopy; scanning transmission ion microscopy; delay line detector; channeling; bright field; dark field

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-09
    DOI: 10.14278/rodare.515
    License: CC-BY-1.0

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Permalink: https://www.hzdr.de/publications/Publ-31631
Publ.-Id: 31631


Zero-field propagation of spin waves in waveguides prepared by focused ion beam direct writing

Flajšman, L.; Wagner, K.; Vaňatka, M.; Gloss, J.; Křižáková, V.; Schmid, M.; Schultheiß, H.; Urbánek, M.

Metastable face-centered-cubic Fe78Ni22 thin films are excellent candidates for focused ion beam direct writing of magnonic structures due to their favorable magnetic properties after ion-beam-induced transformation. The focused ion beam transforms the originally nonmagnetic fcc phase into the ferromagnetic bcc phase with additional control over the direction of uniaxial magnetic in-plane anisotropy and saturation magnetization. Local magnetic anisotropy direction control eliminates the need for external magnetic fields, paving the way towards complex magnonic circuits with waveguides pointing in different directions. In the present study, we show that the magnetocrystalline anisotropy in transformed areas is strong enough to stabilize the magnetization in the direction perpendicular to the long axis of narrow waveguides. Therefore, it is possible to propagate spin waves in these waveguides in the favorable Damon-Eshbach geometry without the presence of any external magnetic field. Phase-resolved microfocused Brillouin light scattering yields the dispersion relation of these waveguides in zero as well as in nonzero external magnetic fields.

Keywords: Ferromagnetism; Magnetic Anisotropy; Magnetic phase transition; Magnetization Dynamics; Spin Dynamics; Spin Waves; Structural Phase transition; Focused ion beam

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Permalink: https://www.hzdr.de/publications/Publ-31626
Publ.-Id: 31626


Performance investigation of bulk photoconductive semiconductor switch based on reversely biased p+in+ structure

Hu, L.; Xu, M.; Li, X.; Wang, Y.; Wang, Y.; Dong, H.; Schneider, H.

We present an investigation of a low-energy-triggered bulk gallium arsenide (GaAs) photoconductive semiconductor switch (PCSS) that is characterized by powerful avalanche domains. The performance of the switch is investigated using a reversely biased p⁺-i-n⁺ structure with 0.625-mm thickness, and the 8.0-kV, 170-ps bulk PCSS that is triggered by a 905-nm laser at the energy of 5.7 nJ is achieved. In the low-energy-triggered mode, it is found experimentally that the reduction of required energy for switching operation is not always kept by the continuous increase of the bias field in the bulk PCSS due to Franz–Keldysh effect. We also analyze the triggering efficiency depending on the laser wavelength numerically, and results indicate that the earlier formation of the powerful avalanche domains is realized by the increased wavelength, which causes lower laser energy for switching operation. Moreover, the prestudy of high-power microwave (HPM) applications is also introduced utilizing bulk PCSS, and we constructed the basic units for ultrawide-band (UWB) pulse and HPM-driven pulse.

Keywords: photoconductive semiconductor switch; avalanche domain; GaAs

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Permalink: https://www.hzdr.de/publications/Publ-31625
Publ.-Id: 31625


Mode-locked short pulses from an 8 μm wavelength semiconductor laser

Hillbrand, J.; Opačcak, N.; Piccardo, M.; Schneider, H.; Strasser, G.; Capasso, F.; Schwarz, B.

Quantum cascade lasers (QCL) have revolutionized the generation of mid-infrared light. Yet, the ultrafast carrier transport in mid-infrared QCLs have so far constituted a seemingly insurmountable obstacle for the formation of ultrashort light pulses. Here, we demonstrate that careful quantum design of the gain medium and control over the intermode beat synchronization enable transform-limited picosecond pulses from QCL frequency combs. Both an interferometric radio-frequency technique and second-order autocorrelation shed light on the pulse dynamics and confirm that mode-locked operation is achieved from threshold to rollover current. Furthermore, we show that both antiphase and in-phase synchronized states exist in QCLs. Being electrically pumped and compact, mode-locked QCLs pave the way towards monolithically integrated non-linear photonics in the molecular fingerprint region beyond 6 μm wavelength.

Keywords: quantum cascade laser; two-photon QWIP; mid-infrared, frequency comb

Permalink: https://www.hzdr.de/publications/Publ-31624
Publ.-Id: 31624


Wire-mesh sensor measurements of single-phase liquid flows at different temperatures

Wiedemann, P.; de Assis Dias, F.; Schleicher, E.; Hampel, U.

The dataset contains raw data that is related to the investigation "Temperature Compensation for Conductivity-Based Phase Fraction Measurements with Wire-Mesh Sensors in Gas-Liquid Flows of Dilute Aqueous Solutions".

A 16x16 conductivity-based wire-mesh sensor was placed in a single-phase liquid loop with adjustable fluid temperature. The dataset includes the wire-mesh sensor measurements with water at several temperature levels from 12.5°C to 80°C and the corresponding electrical conductivites. Two water samples, namely deionized water and a mixed water sample, were investigated. The latter one is composed of 95% deionized water and 5% local tap water.

Keywords: wire-mesh sensor; temperature compensation; electrical conductivity

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-21
    DOI: 10.14278/rodare.555

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Permalink: https://www.hzdr.de/publications/Publ-31623
Publ.-Id: 31623


Frequency control of auto-oscillations of the magnetization in spin Hall nano-oscillators

Hache, T.

This thesis experimentally demonstrates four approaches of frequency control of magnetic autooscillations in spin Hall nano-oscillators (SHNOs).
The frequency can be changed in the GHZ-range by external magnetic fields as shown in this work. This approach uses large electromagnets, which is inconvenient for future applications.The nonlinear coupling between oscillator power and frequency can be used to control the latter one by changing the applied direct current to the SHNO. The frequency can be controlled over a range of several 100 MHz as demonstrated in this thesis.
The first part of the experimental chapter demonstrates the synchronization (injection-locking) between magnetic auto-oscillations and an external microwave excitation. The additionally applied microwave current generates a modulation of the effective magnetic field, which causes the interaction with the auto-oscillation. Both synchronize over a range of several 100 MHz. In this range, the auto-oscillation frequency can be controlled by the external stimulus. An increase of power and a decrease of line width is achieved in the synchronization range. This is explained by the increased coherence of the auto-oscillations. A second approach is the synchronization of auto-oscillations to an alternating magnetic field. This field is generated by a freestanding antenna, which is positioned above the SHNO.
The second part of the experimental chapter introduces a bipolar concept of SHNOs and its experimental demonstration. In contrast to conventional SHNOs, bipolar SHNOs generate autooscillations for both direct current polarities and both directions of the external magnetic field. This is achieved by combining two ferromagnetic layers in an SHNO. The combination of two different ferromagnetic materials is used to switch between two frequency ranges in dependence of the direct current polarity since it defines the layer showing auto-oscillations. This approach can be used to change the frequency in the GHz-range by switching the direct current polarity.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-21
    DOI: 10.14278/rodare.553
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31619
Publ.-Id: 31619


Raw data: CoFeB beamtime overview

Awari, N.; Deinert, J.-C.

Collection of raw data and evaluated data for the CoFeB experiments carried out in collaboration with Stefano Bonetti et al.

Keywords: Spin dynamics; nutation; CoFeB; Terahertz

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-19
    DOI: 10.14278/rodare.551

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Permalink: https://www.hzdr.de/publications/Publ-31612
Publ.-Id: 31612


Parametric optimization in rougher flotation performance of a sulfidized mixed copper ore

Hassanzadehmahaleh, A.; Azizi, A. A.; Masdarian, M. A.; Bahri, Z. C.; Niedoba, T. D.; Surowiak, A. D.

The dominant challenge of current copper beneficiation plants is the low recoverability of oxide copper-bearing minerals associated with sulfide type ones. Furthermore, applying commonly used conventional methodologies does not allow the interactional effects of critical parameters in the flotation processes to be investigated, which is mostly overlooked in the literature. To tackle this issue, the present paper aimed at characterizing the behavior of five key effective factors and their interactions in a sulfidized copper ore. In this context, dosage of collector (sodium di-ethydithiophosphate, 60–100 g/t), depressant (sodium silicate, 80–120 g/t) and frother (methyl isobutyl carbinol (MIBC), 6–10 g/t), pulp pH (7–11) and agitation rate (900–1300 rpm) were examined and statistically analyzed using response surface methodology. Flotation experiments were conducted in a Denver type agitated flotation cell at the rougher stage. The experimental results showed that increasing the pH (from 8 to 10) at low agitation rate (1000 rpm) enhanced the recovery from 80.36% to 85.22%, while at high agitation rate (1200 rpm), a slight declination occurred in the recovery. Meanwhile, increasing the collector dosage at a lower frother value (7 g/t), caused a reduction of about 4.44% in copper recovery owing to the interactions between factors, whereas at a higher frother level (9 g/t), the recovery was almost unchanged. The optimization process was also performed using the goal function approach, and maximum copper recovery of 92.75% was obtained using ~70 g/t collector, 110 g/t depressant, 7 g/t frother, pulp pH of 10 and 1000 rpm agitation rate.

Keywords: sulfidized copper ore; flotation; interaction effects; recovery; optimization

Permalink: https://www.hzdr.de/publications/Publ-31611
Publ.-Id: 31611


Point and extended defects in heteroepitaxial β-Ga2O3 films

Saadatkia, P.; Agarwal, S.; Hernandez, A.; Reed, E.; Brackenbury, I. D.; Codding, C. L.; Liedke, M. O.; Butterling, M.; Wagner, A.; Selim, F. A.

Ga2O3 is emerging as an excellent potential semiconductor for high power and optoelectronic devices.
However, the successful development of Ga2O3 in a wide range of applications requires a full understanding of the role and nature of its point and extended defects. In this work, high quality epitaxial Ga2O3 films were grown on sapphire substrates by metal-organic chemical vapor deposition and fully characterized in terms of structural, optical, and electrical properties. Then defects in the films were investigated by a combination of depth-resolved Doppler broadening and lifetime of positron annihilation spectroscopies and thermally stimulated emission (TSE). Positron annihilation techniques can provide information about the nature and concentration of defects in the films, while TSE reveals the energy level of defects in the bandgap. Despite very good structural properties, the films exhibit short positron diffusion length, which is an indication of high defect density and long positron lifetime, a sign for the formation of Ga vacancy related defects and large vacancy clusters. These defects act as deep and shallow traps for charge carriers as revealed from TSE, which explains the reason behind the difficulty of developing conductive Ga2O3 films on non-native substrates. Positron lifetime measurements also show nonuniform distribution of vacancy clusters throughout the film depth. Further, the work investigates the modification of defect nature and properties through thermal treatment in various environments. It demonstrates the sensitivity of Ga2O3 microstructures to the growth and thermal treatment environments and the significant effect of modifying defect structure on the bandgap and optical and electrical properties of Ga2O3

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; Doppler broadening; defetcs; Ga2O3

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Permalink: https://www.hzdr.de/publications/Publ-31609
Publ.-Id: 31609


Code, data and supplementary material for: An improved contact method for quantifying the mixing of a binary granular mixture

Papapetrou, T. N.; Lecrivain, G.; Bieberle, M.; Boudouvis, A.; Hampel, U.

This material is related to the publication "An improved contact method for quantifying the mixing of a binary granular mixture", submitted on 13.05.2020 to Granular Matter. The original camera video, an intermediate masked video and the final preprocessed video used in the calculations, made from frames 4-1004 of the masked one, are included. The code used for all calculations in the paper and supplementary material, including the implementation of the mixing index evaluation methods, as well as the static artificial images and the generated data, are also included. All images used in the calculations are stored in the required data form. The figures of the paper are also included, as well as two supplementary materials: a version of Figure 12 with the points of the original contact method, and a discussion on the calculation of the minimum modified contact length.

Keywords: binary particle mixing; rotating drum; image analysis; mixing index; contact method; variance method

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-13
    DOI: 10.14278/rodare.548

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Permalink: https://www.hzdr.de/publications/Publ-31602
Publ.-Id: 31602


The effect of Pd(II) chloride complexes anchoring on the formation and properties of Pd/MgAlOx catalysts

Belskaya, O. B.; Zaikovskii, V. I.; Gulyaeva, T. I.; Talsi, V. P.; Trubina, S. V.; Kvashnina, K.; Nizovskii, A. I.; Kalinkin, A. V.; Bukhtiyarov, V. I.; A. Likholobov, V.

Pd(II) chloride complexes were anchored using magnesium-aluminum layered double
hydroxides (LDHs) with interlayer anions 3 2 and ), which possess different exchange properties, and MgAl mixed oxide during its rehydration. It was shown that the catalysts of the same chemical composition with different size, morphology and electronic state of supported palladium particles can be synthesized by varying the localization of Pd precursor. The properties of Pd/MgAlOx catalysts were studied in aqueous-phase hydrogenation of furfural.
Anchoring of the Pd precursor in the interlayer space of LDHs is accompanied by the formation of non-isometric agglomerated palladium particles which contain less oxidized metal and show a higher activity toward hydrogenation of furfural. Magnesium-aluminum oxides in Pd/MgAlOx catalysts are rehydrated in the aqueous-phase reaction to yield the activated MgAl-LDH species as a support, which promotes the furfural conversion via hydrogenation of the furan cycle.

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  • Secondary publication expected from 08.10.2021

Permalink: https://www.hzdr.de/publications/Publ-31600
Publ.-Id: 31600


Development of New 14 Cr ODS Steels by Using New Oxides Formers and B as an Inhibitor of the Grain Growth

Meza, A.; Macía, E.; García-Junceda, A.; Antonio Díaz, L.; Chekhonin, P.; Altstadt, E.; Serrano, M.; Eugenia Rabanal, M.; Campos, M.

In this work, new oxide dispersion strengthened (ODS) ferritic steels have been produced by powder metallurgy using an alternative processing route and characterized afterwards by comparing them with a base ODS steel with Y2O3 and Ti additions. Different alloying elements like boron (B), which is known as an inhibitor of grain growth obtained by pinning grain boundaries, and complex oxide compounds (Y-Ti-Zr-O) have been introduced to the 14Cr prealloyed powder by using mechanical alloying (MA) and were further consolidated by spark employing plasma sintering (SPS). Techniques such as x-ray diffraction (XRD), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to study the obtained microstructures.
Micro-tensile tests and microhardness measurements were carried out at room temperature to analyze the mechanical properties of the differently developed microstructures, which was considered to result in a better strength in the ODS steels containing the complex oxide Y-Ti-Zr-O. In addition, small punch (SP) tests were performed to evaluate the response of the material under high temperatures conditions, under which promising mechanical properties were attained by the materials containing Y-Ti-Zr-O (14Al-X-ODS and 14Al-X-ODS-B) in comparison with the other commercial steel, GETMAT. The differences in mechanical strength can be attributed to the precipitate’s density, nature, size, and to the density of dislocations in each ODS steel.

Permalink: https://www.hzdr.de/publications/Publ-31597
Publ.-Id: 31597


Feature extraction for hyperspectral mineral domain mapping: A test of conventional and innovative methods

Lorenz, S.; Ghamisi, P.; Kirsch, M.; Jackisch, R.; Rasti, B.; Gloaguen, R.

Hyperspectral (HS) imaging holds great potential for the mapping of geological targets. Innovative acquisition modes such as drone-borne or terrestrial remote sensing open up new scales and angles of observation, which allow to analyze small-scale, vertical, or difficult-to-access outcrops. A variety of available sensors operating in different spectral ranges can provide information about the abundance and spatial location of various geologic materials. However geological outcrops are inherently uneven and spectrally heterogeneous, may be covered by dust, lichen or weathering crusts, or contain spectrally indistinct objects, which is why classifications or domain mapping approaches are often used in geoscientific and mineral exploration applications as a means to discriminate mineral associations (e.g. ore or alteration zones) based on overall variations in HS data. Feature extraction (FE) algorithms are prominently used as a preparatory step to identify the first order variations within the data and, simultaneously, reduce noise and data dimensionality. The most established FE algorithms in geosciences are, by far, Principal Component Analysis (PCA) and Minimum Noise Fraction (MNF). Major progress has been conducted in the image processing community within the last decades, yielding innovative FE methods that incorporate spatial information for smoother and more accurate classification results. In this paper, we test the applicability of conventional (PCA, MNF) and innovative FE techniques (OTVCA: Orthogonal total variation component analysis and WSRRR: Wavelet-based sparse reduced-rank regression) on three case studies from geological HS mapping campaigns, including drone-borne mineral exploration, terrestrial paleoseismic outcrop scanning and thermal HS lithological mapping. This allows us to explore the performance of different FE approaches on complex geological data with sparse or partly inaccurate validation data. For all case studies, we demonstrate advantages of innovative FE algorithms in terms of classification accuracy and geological interpretability. We promote the use of advanced image processing methods for applications in geoscience and mineral exploration as a tool to support geological mapping activities.

Keywords: feature extraction; domain mapping; mineral exploration; image processing; hyperspectral imaging; classification

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  • Secondary publication expected from 22.10.2021

Permalink: https://www.hzdr.de/publications/Publ-31596
Publ.-Id: 31596


Automated mineralogy particle dataset: apatite flotation

Hoang, D. H.; Pereira, L.; Kupka, N.; Tolosana Delgado, R.; Frenzel, M.; Rudolph, M.; Gutzmer, J.

This particle dataset was used for demonstrating the particle-tracking method presented in the paper "Computing single-particle flotation kinetics using automated mineralogy data and machine learning", submitted to Minerals Engineering in 08/10/2020, by Lucas Pereira, Max Frenzel, Duong Huu Hoang, Raimon Tolosana-Delgado, Martin Rudolph, Jens Gutzmer from the Helmholtz Institute Freiberg for Resource Technology.

This data belongs to the flotation tests performed by Duong Huu Hoang, and presented in:

Hoang, D.H., Kupka, N., Peuker, U.A., Rudolph, M., 2018. Flotation study of fine grained carbonaceous sedimentary apatite ore – Challenges in process mineralogy and impact of hydrodynamics. Miner. Eng. 121, 196–204. https://doi.org/10.1016/j.mineng.2018.03.021

For this study, phosphate rock samples from the Lao Cai province, Vietnam, were provided by the Vietnam Apatite Limited Company. The objective of the flotation experiments was to determine the best way to efficiently separate fluorapatite from dolomite, calcite and silicates. After grinding for 8 minutes in a laboratory ball mill to assure a d90 of 67 µm, batch flotation tests were performed in a flotation cell built at the TU Bergakademie Freiberg. Corn starch ((C6H10O5)n) gelatinized with sodium hydroxide (NaOH) was used in combination with sodium silicate (Na2SiO3) to depress gangue minerals. The latter also acts as a fine particle dispersant. Solution pH was kept at 10 using the modifier sodium carbonate (Na2CO3), which can also be regarded as a depressant. Berol 2015 was used as the collector. Four concentrate fractions were collected after 0.75 min (CA), 1.50 min (CB), 3.00 min (CC), and 6.00 min (CD). In addition, a final tailings sample was collected (TD). Five replicates of the test were done to ensure reproducibility and produce enough sample mass for detailed characterization. All samples, including the feed, were wet sieved into four size fractions (-20 µm, +20 to -32 µm, +32 to -50 µm, and +50 µm) before characterization by MLA at the Helmholtz Institute Freiberg for Resource Technology. Samples were analyzed on a FEI Quanta 650F scanning electron microscope equipped with two Bruker Quantax X-Flash 5030 EDX detectors. The SEM was operated at 25 kV overall electron beam accelerating voltage and Extended BSE Liberation Analysis measurement mode. MLA results were validated with ICP-OES chemical assays. Particles from the flotation product samples (concentrate and tailings) are in the Traindata.csv file, while particles from the feed sample are in the FeedData.csv file. The weight distribution of each sample is given below:

Sample | wt.%

CA -20µm | 6.7

CA 20-32µm | 5.8

CA 32-50µm | 4.6

CA +50µm | 2.2

CB -20µm | 6.4

CB 20-32µm | 5.4

CB 32-50µm | 3.9

CB +50µm | 2.8

CC -20µm | 5.8

CC 20-32µm | 4.3

CC 32-50µm | 3.5

CC +50µm | 2.0

CD -20µm | 4.7

CD 20-32µm | 2.8

CD 32-50µm | 2.3

CD +50µm | 1.1

TD -20µm | 11.3

TD 20-32µm | 7.0

TD 32-50µm | 6.7

TD +50µm | 10.7

Feed -20µm | 36.60

Feed 20-32µm | 23.88

Feed 32-50µm | 21.75

Feed +50µm | 17.78

Variable names:

  • Mineral composition: Actinolite, Albite, Almandine, Apatite, Barite, Biotite, Calcite, Chalcopyrite, Clinochlore, Diopside, Dolomite, Fluorite, Hematite, Muscovite, Orthoclase, Plagioclase, Phlogopite, Pyrite, Pyrrhotite, Quartz, Rutile, Sanidine, Sphalerite_Fe, Titanite, Zircon.
  • Surface composition: Actinolite.surf, Albite.surf, Almandine.surf, Apatite.surf, Barite.surf, Biotite.surf, Calcite.surf, Chalcopyrite.surf, Clinochlore.surf, Diopside.surf, Dolomite.surf, Fluorite.surf, Hematite.surf, Muscovite.surf, Orthoclase.surf, Plagioclase.surf, Phlogopite.surf, Pyrite.surf, Pyrrhotite.surf, Quartz.surf, Rutile.surf, Sanidine.surf, Sphalerite_Fe.surf, Titanite.surf, Zircon.surf
  • Size and shape: AspectRatio, Solidity, ECD
  • Sample identifier: Class - In this case, particles identified with "CA20", for example, are the particles from the <20µm size fraction of the first concentrate sample, while "TD50" are the particles from the >50µm size fraction of the final tailings sample.

Keywords: Apatite; Froth flotation; Automated mineralogy; Geometallurgy; Particle-tracking

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-08
    DOI: 10.14278/rodare.542
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31592
Publ.-Id: 31592


Raw data: Magnetic field-induced even-order harmonic generation in the three-dimensional Dirac semimetal Cd3As2

Deinert, J.-C.

Raw files from the TELBE beamtime August 2020 for exchange.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-06
    DOI: 10.14278/rodare.533

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Permalink: https://www.hzdr.de/publications/Publ-31589
Publ.-Id: 31589


Interactive results viewer: Computing single-particle flotation kinetics using automated mineralogy data and machine learning

Pereira, L.; Frenzel, M.; Hoang, D. H.; Tolosana Delgado, R.; Rudolph, M.; Gutzmer, J.

This plotting application allows the reader to interact with all results obtained in the case study presented in the publication

"Computing single-particle flotation kinetics using automated mineralogy data and machine learning", submitted on 07/10/2020 to Minerals Engineering and currently under review.

The interactive plot displays the flotation kinetics modelling outcome (k, Rmax, km) for single-particles. The user is able to filter particles according to their intrinsic properties (modal composition, surface composition, size, and shape), thus allowing the user to understand the influence of every particle property in their process (i.e. flotation) behavior.

The platform contains a help function to guide the user.

It can be accessed here: Pereira et al. 2021 Flotation kinetics platform.

Keywords: Geometallurgy; Particle-tracking; Froth flotation; Automated mineralogy

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-06
    DOI: 10.14278/rodare.535
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31588
Publ.-Id: 31588


BGM MLA data from grinding kinetics experiments

Belo Fernandes, I.

Datasource from two sets of grinding experiments:

- from top size fraction -1600µm+1250µm

- from top size fraction -425µm+315µm

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-05
    DOI: 10.14278/rodare.531

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Permalink: https://www.hzdr.de/publications/Publ-31586
Publ.-Id: 31586


Long-range magnetic order in the S = 1/2 triangular lattice antiferromagnet KCeS2

Bastien, G.; Rubrecht, B.; Haeussler, E.; Schlender, P.; Zangeneh, Z.; Avdoshenko, S.; Sarkar, R.; Alfonso, A.; Luther, S.; Onykiienko, Y. A.; Walker, H. C.; Kühne, H.; Grinenko, V.; Guguchia, Z.; Kataev, V.; Klauss, H.-H.; Hozoi, L.; van den Brink, J.; Inosov, D. S.; Büchner, B.; Wolter, A. U. B.; Doert, T.

Recently, several putative quantum spin liquid (QSL) states were discovered in S󠆶 = 1/2 rare-earth based triangular-lattice antiferromagnets (TLAF) with the delafossite structure. In order to elucidate the conditions for a QSL to arise, we report here the discovery of a long-range magnetic order in the Ce-based TLAF KCeS2 below TN = 0.38 K, despite the same delafossite structure. Finally, combining various experimental and computational methods, we characterize the crystal electric field scheme, the magnetic anisotropy and the magnetic ground state of KCeS2.

Permalink: https://www.hzdr.de/publications/Publ-31585
Publ.-Id: 31585


2D MOFs: A New Platform for Optics?

Arora, H.; Park, S.; Dong, R.; Erbe, A.

With the research on inorganic 2D semiconductors reaching its zenith, the search for new materials beyond these traditional 2D materials is at a rapid pace. In this article, we present an emerging class of 2D semiconductors, so-called metal-organic frameworks, in terms of their synthesis, intrinsic properties, and underlying charge transport mechanisms. Further, we discuss their potential as active elements in optical applications.

Keywords: Metal-organic frameworks; Two-dimensional semiconductors; Photonics; optical applications; photodetectors; high-mobility materials; sensors

Permalink: https://www.hzdr.de/publications/Publ-31584
Publ.-Id: 31584


Protonen als Alternative zur konventionellen Strahlentherapie – Unterschiede und Herausforderungen

Spautz, S.; Stützer, K.

Die externe Strahlentherapie ist eine wesentliche Komponente bei der Behandlung von Tumoren. Üblicherweise wird dafür Photonenstrahlung verwendet. Jedoch hat sich die Protonentherapie auf Grund ihrer physikalischen Eigenschaften zu einer attraktiven Alternative entwickelt. Vor allem ihre überlegene Dosisverteilung ermöglicht im Vergleich zur herkömmlichen Strahlentherapie eine bessere Normalgewebsschonung, wodurch potentiell das Risiko von Nebenwirkungen und Toxizitäten sinkt. Wir geben hier einen einleitenden Überblick zu den physikalischen Protoneneigenschaften und den Möglichkeiten der Dosisformierung. Insbesondere werden auch spezielle Herausforderungen in der Protonentherapie und damit verbundene aktuelle Forschungsschwerpunkte vorgestellt.

Keywords: Protonentherapie; Physikalische Grundlagen; Herausforderungen; Forschungsschwerpunkte

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  • Secondary publication expected from 01.11.2021

Permalink: https://www.hzdr.de/publications/Publ-31582
Publ.-Id: 31582


New reaction rates for the destruction of 7Be during big bang nucleosynthesis measured at CERN/n_TOF and their implications on the cosmological lithium problem

Mengoni, A.; Damone, L. A.; Barbagallo, M.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Caballero, L.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Casanovas, A.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Davies, P. J.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krtička, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; Lerendegui-Marco, J.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Maugeri, E.; Mazzone, A.; Mendoza, E.; Michalopoulou, V.; Milazzo, P. M.; Millán-Callado, M. A.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Quesada, J. M.; Ramos Doval, D.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A. E.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.

New measurements of the 7Be(n,α)4He and 7Be(n,p)7Li reaction cross sections from thermal to keV neutron energies have been recently performed at CERN/n_TOF. Based on the new experimental results, astrophysical reaction rates have been derived for both reactions, including a proper evaluation of their uncertainties in the thermal energy range of interest for big bang nucleosynthesis studies. The new estimate of the 7Be destruction rate, based on these new results, yields a decrease of the predicted cosmological 7Li abundance insufficient to provide a viable solution to the cosmological lithium problem.

Permalink: https://www.hzdr.de/publications/Publ-31579
Publ.-Id: 31579


Status and perspectives of the neutron time-of-flight facility n_TOF at CERN

Chiaveri, E.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, M.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Caballero, L.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Casanovas, A.; Cerutti, F.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krtička, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; Lerendegui-Marco, J.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Maugeri, E.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Millán-Callado, M. A.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Quesada, J. M.; Ramos Doval, D.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A. E.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.

Since the start of its operation in 2001, based on an idea of Prof. Carlo Rubbia [1], the neutron time of-flight facility of CERN, n_TOF, has become one of the most forefront neutron facilities in the world for wide-energy spectrum neutron cross section measurements. Thanks to the combination of excellent neutron energy resolution and high instantaneous neutron flux available in the two experimental areas, the second of which has been constructed in 2014, n_TOF is providing a wealth of new data on neutron-induced reactions of interest for nuclear astrophysics, advanced nuclear technologies and medical applications. The unique features of the facility will continue to be exploited in the future, to perform challenging new measurements addressing the still open issues and long-standing quests in the field of neutron physics. In this document the main characteristics of the n_TOF facility and their relevance for neutron studies in the different areas of research will be outlined, addressing the possible future contribution of n_TOF in the fields of nuclear astrophysics, nuclear technologies and medical applications. In addition, the future perspectives of the facility will be described including the upgrade of the spallation target, the setup of an imaging installation and the construction of a new irradiation area.

Permalink: https://www.hzdr.de/publications/Publ-31578
Publ.-Id: 31578


Measurement of the energy-differential cross-section of the 12C(n,p)12B and 12C(n,d)11B reactions at the n_TOF facility at CERN

Barbagallo, M.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Caballero, L.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Casanovas, A.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krtička, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; Lerendegui-Marco, J.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Maugeri, E.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Millán-Callado, M. A.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Quesada, J. M.; Ramos Doval, D.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A. E.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.

Although the 12C(n,p)12B and 12C(n,d)11B reactions are of interest in several fields of basic and applied Nuclear Physics the present knowledge of these two cross-sections is far from being accurate and reliable, with both evaluations and data showing sizable discrepancies. As part of the challenging n_TOF program on (n,cp) nuclear reactions study, the energy differential cross-sections of the 12C(n,p)12B and 12C(n,d)11 B reactions have been measured at CERN from the reaction thresholds up to 30 MeV neutron energy. Both measurements have been recently performed at the long flight-path (185 m) experimental area of the n_TOF facility at CERN using a pure (99.95%) rigid graphite target and two silicon telescopes. In this paper an overview of the experiment is presented together with a few preliminary results.

Permalink: https://www.hzdr.de/publications/Publ-31577
Publ.-Id: 31577


Measurement of the 242Pu(n, γ) cross section from thermal to 500 keV at the Budapest research reactor and CERN n_TOF-EAR1 facilities

Lerendegui-Marco, J.; Guerrero, C.; Mendoza, E.; Quesada, J. M.; Eberhardt, K.; Junghans, A.; Krtiička, M.; Belgya, T.; Maróti, B.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Barros, S.; Bečvář, F.; Beinrucker, C.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Furman, V.; Göbel, K.; García, A. R.; Gawlik, A.; Glodariu, T.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heftrich, T.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Knapova, I.; Kokkoris, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Musumarra, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, J. I.; Praena, J.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Weigand, M.; Weiss, C.; Wolf, C.; Woods, P. J.; Wright, T.; Žugec, P.; The N_TOF Collaboration

The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project resulted in a 242Pu sample consisting of a stack of seven fission-like targets making a total of 95(4) mg of 242Pu electrodeposited on thin (11.5 μm) aluminum backings. This contribution presents the results of a set of measurements of the 242Pu(n, γ) cross section from thermal to 500 keV combining different neutron beams and techniques. The thermal point was determined at the Budapest Research Reactor by means of Neutron Activation Analysis and Prompt Gamma Analysis, and the resolved (1 eV - 4 keV) and unresolved (1 - 500 keV) resonance regions were measured using a set of four Total Energy detectors at the CERN n_TOF-EAR1.

Permalink: https://www.hzdr.de/publications/Publ-31576
Publ.-Id: 31576


Co(NO3)2 as an inverted umbrella-type chiral noncoplanar ferrimagnet

Danilovich, I. L.; Deeva, E. B.; Bukhteev, K. Y.; Vorobyova, A. A.; Morozov, I. V.; Volkova, O. S.; Zvereva, E. A.; Maximova, O. V.; Solovyev, I. V.; Nikolaev, S. A.; Phuyal, D.; Abdel-Hafiez, M.; Wang, Y. C.; Lin, J.-Y.; Chen, J. M.; Gorbunov, D.; Puzniak, K.; Lake, B.; Vasiliev, A. N.

The low-dimensional magnetic systems tend to reveal exotic spin-liquid ground states or form peculiar types of long-range order. Among systems of vivid interest are those characterized by the triangular motif in two dimensions. The realization of either ordered or disordered ground state in triangular, honeycomb, or kagome lattices is dictated by the competition of exchange interactions, also being sensitive to anisotropy and the spin value of magnetic ions.While the low-spin Heisenberg systems may arrive to a spin-liquid long-range entangled quantum state with emergent gauge structures, the high-spin Ising systems may establish the rigid noncollinear structures. Here, we present the case of chiral noncoplanar inverted umbrella-type ferrimagnet formed in cobalt nitrate Co(NO3)2 below TC = 3 K with the comparable spin and orbital contributions to the total magnetic moment.

Permalink: https://www.hzdr.de/publications/Publ-31575
Publ.-Id: 31575


Dataset for: Morphology of flashing feeds at critical fluid properties in larger pipes

Döß, A.; Schubert, M.; Hampel, U.

This data set contains cross-sectional averaged vapor fraction data obtained for flashing refrigerant in the horizontal feed section (inner pipe diameter of 200 mm) of the TERESA facility. The data was obtained with the Wire-mesh Sensor Framework GUI (Version 1.3.0). The archive 'void' contains .epst-files which are organized as a two column table (ASCII). The first column denotes the time step (in seconds), the second column is the cross-sectional averaged vapor fraction in percent.

Allocation of the files to the operational conditions is included separate .csv-file (overview.csv), which contains 12 columns for each measurement. Here the averaged values of the .epst-files are included as well.

In this study, two wire-mesh sensors were operated simultaneously. WMS1 (*_X_Sensor_1.epst) was located in an axial distance of L = 2.5 D from the flash nozzle and WMS2 (*_Y_Sensor_2.epst) was located L = 17.5 D away from the flash nozzle.  

Keywords: TERESA; Flashing feed; Wire-mesh sensor

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-01
    DOI: 10.14278/rodare.418
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31573
Publ.-Id: 31573


Detection of REEs with lightweight UAV-based hyperspectral imaging.

Booysen, R.; Jackisch, R.; Lorenz, S.; Zimmermann, R.; Kirsch, M.; Nex, P. A. M.; Gloaguen, R.

Rare Earth Elements (REEs) supply is important to ensure the energy transition, e-mobility and ultimately to achieve the sustainable development goals of the United Nations. Conventional exploration techniques usually rely on substantial geological field work including dense in-situ sampling with long delays until provision of analytical results. However, this approach is limited by land accessibility, financial status, climate and public opposition. Efficient and innovative methods are required to mitigate these limitations. The use of lightweight Unmanned Aerial Vehicles (UAVs) provides a unique opportunity to conduct rapid and non-invasive exploration even in socially sensitive areas and in relatively inaccessible locations. We employ drones with hyperspectral sensors to detect REEs at the Earth’s surface and thus contribute to a rapidly evolving field at the cutting edge of exploration technologies. We showcase for the first time the direct mapping of REEs with lightweight hyperspectral UAV platforms. Our solution has the advantage of quick turn-around times (<1d), low detection limits (<200ppm for Nd) and is ideally suited to support exploration campaigns. This procedure was successfully tested and validated in two areas: Marinkas Quellen, Namibia, and Siilinjärvi, Finland. This strategy should invigorate the use of drones in exploration and for the monitoring of mining activities.

Permalink: https://www.hzdr.de/publications/Publ-31572
Publ.-Id: 31572


Reducing entrainment in ultrafine particle flotation by selective flocculation of gangue material

Sygusch, J.; Rudolph, M.

Froth flotation is an efficient and well-established separation technique for particles with sizes ranging from 10 µm to 200 µm, but when it comes to the separation of ultrafine particles (< 10 µm) there are still some challenges. This research is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart” and aims at developing a method for the separation of ultrafine particles based on multiple particle properties, such as wettability, morphology (shape or roughness) and size. In this study, the focus lies on the investigation of the effect of particle size on the flotation outcome.
A system consisting of ultrafine size fractions of glass particles as the valuable material and magnetite as the gangue material is used for testing. Wettability analysis is carried out using inverse gas chromatography, whereas size and shape properties are obtained via a combination of laser diffraction and microscopic analysis. In order to investigate the effect of particle size, the magnetite is selectively flocculated using macromolecules as flocculants. A novel flotation apparatus, designed for the flotation of ultrafine particles by combining advantages from column flotation and machine-type froth flotation, is used for all flotation tests.

Keywords: Ultrafine Particles; Flotation; Selective flocculation; Entrainment

  • Poster (Online presentation)
    10. ProcessNet-Jahrestagung und 34. DECHEMA-Jahrestagung der Biotechnologen 2020, 21.-24.09.2020, Online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31571
Publ.-Id: 31571


Better Together: Ilmenite/Hematite Junctions for Photoelectrochemical Water Oxidation

Berardi, S.; Kesavan, J. K.; Amidani, L.; Meloni, E. M.; Marelli, M.; Boscherini, F.; Caramori, S.; Pasquini, L.

Hematite (α-Fe₂O₃) is an Earth-abundant indirect n-type semiconductor displaying a band gap of about 2.2 eV, useful for collecting a large fraction of visible photons, with frontier energy levels suitably aligned for carrying out the photoelectrochemical water oxidation reaction under basic conditions. The modification of hematite mesoporous thin film photoanodes with Ti(IV), as well as their functionalization with an oxygen evolving catalyst, leads to a six-fold increase in photocurrent density with respect to the unmodified electrode. In order to provide a detailed understanding of this behavior, we report a study of Ti-containing phases within the mesoporous film structure. Using X-ray absorption fine structure and high-resolution transmission electron microscopy coupled with electron energy loss spectroscopy, we find that Ti(IV) ions are incorporated within ilmenite (FeTiO₃) near-surface layers, thus modifying the semiconductor-electrolyte interface. To the best of our knowledge, this is the first time that a FeTiO₃/α -Fe₂O₃ composite is used in a photoelectrochemical set-up for water oxidation. In fact, previous studies of Ti(IV)-modified hematite photoanodes reported the formation of pseudobrookite (Fe₂TiO₅) at the surface. By means of transient absorption spectroscopy, transient photocurrent experiments, and electrochemical impedance spectroscopy, we show that the formation of the Fe₂O₃/FeTiO₃ interface passivates deep traps at the surface and induce a large density of donor levels, resulting in a strong depletion field that separates electron and holes, favoring hole injection in the electrolyte. Our results provide the identification of a phase coexistence with enhanced photoelectrochemical performance, allowing for the rational design of new photoanodes with improved kinetics.

Keywords: Photoelectrochemistry; Hematite; Titanium; EXAFS; Electron Microscopy; Transient Absorption Spectroscopy; Heterointerface; Oxygen Evolution Catalyst

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  • Secondary publication expected from 21.10.2021

Permalink: https://www.hzdr.de/publications/Publ-31569
Publ.-Id: 31569


Formation and crystallographic orientation of NiSi2-Si interfaces

Fuchs, F.; Khan, B.; Deb, D.; Pohl, D.; Schuster, J.; Weber, W. M.; Mühle, U.; Löffler, M.; Georgiev, Y. M.; Erbe, A.; Gemming, S.

The transport properties of novel device architectures depend strongly on the morphology and the quality of the interface between contact and channel materials. In silicon nanowires with nickel silicide contacts, NiSi 2-Si interfaces are particularly important as NiSi 2 is often found as the phase adjacent to the silicide-silicon interface during and after the silicidation. The interface orientation of these NiSi 2-Si interfaces as well as the ability to create abrupt and flat interfaces, ultimately with atomic sharpness, is essential for the properties of diverse emerging device concepts. We present a combined experimental and theoretical study on NiSi 2-Si interfaces. Interfaces in silicon nanowires were fabricated using silicidation and characterized by high-resolution (scanning) transmission electron microscopy. It is found that {111} interfaces occur in 〈110»nanowires. A tilted interface and an arrow-shaped interface are observed, which depends on the nanowire diameter. We have further modeled NiSi 2-Si interfaces by density functional theory. Different crystallographic orientations and interface variations, e.g., due to interface reconstruction, are compared with respect to interface energy densities. The {111} interface is energetically most favorable, which explains the experimental observations. Possible ways to control the interface type are discussed.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-31568
Publ.-Id: 31568


Detection of manufactured nanomaterials in complex environmental compartments – An expert review

Schymura, S.; Hildebrand, H.; Völker, D.; Schwirn, K.; Franke, K.; Fischer, C.

Manufactured nanomaterials (NMs) are materials in which 50% or more of the particles have one or more dimensions between 1 nm and 100 nm. These NMs show interesting properties. However, the same properties that motivate their use in applications are also reason for concern, as NMs can cause toxic reactions and have mobilities in the environment different from bulk materials of the same elements. Despite considerable scientific efforts, the selective detection of manufactured NMs in environmental compartments is still a very complex and challenging task. An expert review of the literature has been conducted on behalf of the German Environment Agency (UBA) to identify relevant methods for nanomaterial detection in complex media in the context of environmental monitoring and a need for action was concluded from the existing body of work.

Keywords: Nanoparticle detection; Environment; complex systems

  • Poster (Online presentation)
    Nanosafety 2020, 05.-07.10.2020, Saarbrücken, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31567
Publ.-Id: 31567


Radiolabeling of nanoparticles - A versatile tool in nanosafety research

Schymura, S.; Hildebrand, H.; Rybkin, I.; Strok, M.; Franke, K.

The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. The monitoring of nanoparticles (NPs) in such complex natural systems as soil, natural waters, plants, sewage sludge, etc. very is challenging using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by the use of radiolabeling which provides an easy way of accurately quantifying nanoparticles in complex systems without extensive sample preparation, regardless of any particulate or elemental background.
We have developed various methods of introducing radiotracers into the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles.

Keywords: Radiolabeling; nanoparticles

  • Poster (Online presentation)
    Nanosafety 2020, 05.-07.10.2020, Saarbrücken, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31566
Publ.-Id: 31566


Monitoring laser-induced magnetization in FeRh by transient terahertz emission spectroscopy

Awari, N.; Semisalova, A.; Deinert, J.-C.; Lenz, K.; Lindner, J.; Fullerton, E.; Uhlir, V.; Li, J.; Clemens, B.; Carley, R.; Scherz, A.; Kovalev, S.; Gensch, M.

In this study, a conceptually different approach for investigating magnetic phase transitions in ultra-thin films is presented. THz emission from a laser-excited material is used to monitor the magnetization dynamics during the laser-driven antiferromagnetic to ferromagnetic transition in FeRh. The emitted THz signal is calibrated against static magnetometry data measurements, giving a direct measure of the absolute magnetic moment of the sample on the sub-picosecond timescale. The technique is, therefore, highly complementary to conventional time-resolved experiments such as time resolved magneto-optic Kerr effect (MOKE) or x-ray magnetic circular dichroism.

Keywords: Magnetization dynamics; terahertz; ultrafast; FeRh

Permalink: https://www.hzdr.de/publications/Publ-31565
Publ.-Id: 31565


Experimental data of the ROCOME2.3 experiment

Kliem, S.

The experiment ROCOM E2.3 represents a boron dilution event in a KONVOI-type pressurized lightwater reactor. It was conducted at room temperature with de-mineralized water without boric acid. Underborated water slugs were modelled by adding Ethanol in order to adjust a density difference of 1.22% with respect to the regular coolant inventory. At the beginning of the experiment, the slugs are enclosed between two valves in the cold legs of loops 1 and 2. The volume of the two water slugs accounts for 0.0576 m 3 (57.6 l) each and the slug fronts are located at 1.8 m upstream of the pressure vessel inlet nozzles. The experiment is started by opening the loop valves and running up the circulation pumps. The time dependency of the volumetric flow rates in all four coolant loops can be found in https://doi.org/10.1016/j.nucengdes.2020.110776. During the experiment, the mixing process was recorded by wire-mesh conductivity sensors at various positions within the coolant loops and the pressure vessel.  The nomenclature of the data files as well as the format of the tables are described in the accompanying document DataDescription_ROCOME23.pdf.

Keywords: boron dilution; coolant mixing; pressurized water reactor

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-25
    DOI: 10.14278/rodare.527
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31562
Publ.-Id: 31562


Presence of Bradyrhizobium sp. under continental conditions in Central Europe

Griebsch, A.; Matschiavelli, N.; Lewandowska, S.; Schmidtke, K.

Soil samples from different locations with varied cultivation histories of soybeans were taken from arable fields in 2018 in East Germany and Poland (Lower Silesia) to evaluate the specific microsymbionts of the soybean, Bradyrhizobium japonicum, over the years after inoculation. Soybean was grown in the selected farms between 2011 and 2017. The aim of the experiment is to investigate whether there is a difference in rhizobia content in soils in which soybean was grown over a different period of time and whether this might lead to differences in plant growth of soybean. The obtained soil samples were directly transferred into containers, then sterilized soybean seeds were sown into pots in the greenhouse. After 94 days of growth, the plants were harvested and various parameters such as nodular mass, number of nodules and dry matter in the individual plant parts were determined. In addition, the relative abundance of Bradyrhizobium sp. in soil samples was determined identified by sequencing. No major decline in Bradyrhizobia could be observed due to a longer interruption of soybean cultivation. Soil properties such as pH, P and Mg content had no significant influence on the formation of nodule mass and number, but seem to have an influence on the relative abundance of Bradyrhizobium sp. The investigations have shown that Bradyrhizobium japonicum persists longer in arable soils even under the site conditions of Central Europe and forms an effective symbiosis with soybeans.

Permalink: https://www.hzdr.de/publications/Publ-31561
Publ.-Id: 31561


Zur Untersuchung schwerer Erdalkalimetalle für die radiopharmazeutische Anwendung

Bauer, D.

Ein maßgebliches medizinisches Problem unserer Gesellschaft sind Krebs- und Tumor-erkrankungen. Aus diesem Grund sind die verbesserte Diagnose und Früherkennung von Krebserkrankungen sowie die Entwicklung neuer und effizienterer Therapiemöglichkeiten ein wichtiger Aspekt der gegenwärtigen medizinischen Forschung.
Die zielgerichtete α-Partikel Therapie (TAT, engl. Targeted Alpha-particle Therapy) ist eine spezielle Form der nuklearmedizinischen Behandlung von Krebserkrankungen und ordnet sich im Feld der Radionuklidtherapie ein. Die TAT hebt sich gegenüber anderen Radionuklidtherapien, wie der Behandlung mit β--oder Auger-Elektronen-Emittern, dadurch hervor, dass sie Chemo- und Strahlungsresistenzen überwinden kann, eine hohe biologische Wirksamkeit zeigt, und dabei gesundes Gewebe vergleichsmäßig wenig belastet.
Bei der TAT werden α-emittierende Radionuklide, hauptsächlich Radiometalle, mittels eines Radiopharmakons zielgerichtet an oder in die Krebszellen transportiert, welche dort hochenergetische α-Partikel emittieren, die zum Absterben des entarteten Gewebes führen. Um ein Radiopharmakon auf Basis eines Radiometalls herzustellen, werden die entsprechenden Radionuklide mittels eines Chelators stabil gebunden, welcher wiederum mit einem Vektormolekül verknüpft ist. Vektormoleküle können dabei monoklonale Antikörper oder niedermolekulare Verbindungen sein, welche spezifische Eigenschaften der Krebszelle adressieren und damit das selektive Binden an diese ermöglichen.
Nur wenige α-Emitter erfüllen die Voraussetzungen, um in der TAT eingesetzt werden zu können. Aus der Reihe der schweren Erdalkalimetalle stammen die beiden α-Emitter Radium 223 und Radium-224, welche großes Potential für eine solche radiopharmazeutische Anwendung besitzen. Zusätzlich kann der γ Emitter Barium 131, dessen Element das nächst leichtere Homologe des Radiums ist, zum Therapie-Monitoring eingesetzt werden. Aufgrund der chemischen Ähnlichkeit der Elemente Barium und Radium können beide mittels des gleichen Chelators gebunden und deren Radionuklide im Rahmen eines kombinierten diagnostischen und therapeutischen – eines so genannten theranostischen – Ansatzes in der Onkologie genutzt werden. Da von Radium keine stabilen Isotope existieren, dient Barium auch als ein nicht-radioaktives Surrogat, um Chelatoren initial bezüglich ihrer Komplex-bildungseigenschaften zu untersuchen.
Ziel dieser Arbeit war es, das Potential ausgewählter Radionuklide aus der Gruppe der schweren Erdalkalimetalle für die radiopharmazeutische Anwendung zu erschließen, und dafür die Möglichkeit ihrer stabilen Bindung in einem Radiopharmakon mittels eines geeigneten Chelators zu untersuchen. Der Fokus lag dabei auf Barium 131 und Radium 224. Als potentielle Chelatoren wurden die beiden Substanzklassen der Calix[4]aren-krone-6-Derivate und der Cavitanden untersucht.
Bei diesen Verbindungen handelt es sich um Makrozyklen, welche aus vier aromatischen Einheiten aufgebaut sind. Ihre Anordnung formt eine Kavität, welche auf die Ionengrößen von Barium und Radium zugeschnitten ist. Die beiden Grundstrukturen verfügen jeweils über acht Sauerstoffatome, die für die Koordination an Ba2+- beziehungsweise Ra2+-Ionen, ideale Donoratome darstellen.
Um die Interaktion der Liganden mit (nicht-radioaktiven) Bariumionen untersuchen zu können, wurden analytische Verfahren auf der Basis von NMR- und UV/Vis-Spektroskopie etabliert. Bei diesen Untersuchungen wurde für die Cavitanden trotzt weitreichender Optimierungsversuche keine Einlagerung von Bariumionen festgestellt.
Für die Calix[4]krone-6-basierten Derivate wurden die entsprechenden 1:1 Metallion-Ligand-Chelate mit Bariumionen hergestellt und nachgewiesen. Die Stabilität der Chelate wurde mit einer Titrationsmethode auf Basis von NMR- und UV/Vis Detektion bestimmt. Aufgrund der geringen Wasserlöslichkeit der gewählten Verbindungen wurden die initialen Versuche im Lösungsmittel Acetonitril durchgeführt. In nachfolgenden Optimierungsschritten wurden Calix[4]krone-6-basierte Chelatoren hergestellt, welche in Hinblick auf das HSAB-Konzept noch besser auf schwere Erdalkalimetalle abgestimmt waren. Zusätzlich wurden diese Chelatoren über funktionelle Gruppen mit einem Vektormolekül verknüpft, welches die Wasserlöslichkeit erhöhte.
Für nachfolgende Radiomarkierungsversuche wurden Dünnschichtchromatographie-Systeme etabliert, welche die Untersuchung von [131Ba]Ba2+- und [224Ra]Ra2+-Chelaten im wässrigen Medium sowie unter kompetitiven Bedingungen ermöglichten. Es konnten jedoch für alle Calix[4]krone-6-Derivate unter wässrigen Bedingungen keine Chelate nachgewiesen werden. Anschließende Untersuchungen legten nahe, dass das Radiometall kinetisch nicht ausreichend stabil in den Calix[4]krone-6-Derivate gebunden ist

Keywords: Radium-223; Barium-131; Makrozyklen; targetd Alpha-Therrapy

  • Doctoral thesis
    TU Dresden, 2020
    Mentor: PD Dr. habil. Constantin Mamat
    162 Seiten

Permalink: https://www.hzdr.de/publications/Publ-31560
Publ.-Id: 31560


Nanocytometer for smart analysis of peripheral blood and acute myeloid leukemia: a pilot study

Schütt, J.; Sandoval Bojorquez, D. I.; Avitabile, E.; Oliveros Mata, E. S.; Milyukov, G.; Colditz, J.; Delogu, L. G.; Rauner, M.; Feldmann, A.; Koristka, S.; Middeke, J. M.; Sockel, K.; Faßbender, J.; Bachmann, M.; Bornhäuser, M.; Cuniberti, G.; Baraban, L.

We realize an ultracompact nanocytometer for real-time impedimetric detection and classification of subpopulations ofliving cells. Nanoscopic nanowires in a microfluidic channel act asnanocapacitors and measure in real time the change of theamplitude and phase of the output voltage and, thus, the electricalproperties of living cells. We perform the cell classification in thehuman peripheral blood (PBMC) and demonstrate for thefirsttime the possibility to discriminate monocytes andsubpopulationsof lymphocytes in a label-free format. Further, we demonstrate thatthe PBMC of acute myeloid leukemia and healthy samples grantthe label free identification of the disease. Using the algorithmbased on machine learning, we generatedspecific data patternstodiscriminate healthy donors and leukemia patients. Such a solutionhas the potential to improve the traditional diagnostics approaches with respect to the overall cost and time effort, in a label-freeformat, and restrictions of the complex data analysis.

Keywords: mpedance cytometer; nanosensor; POC diagnostics; PBMCs; acute myeloid leukemia (AML); machine learning for data treatment

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  • Secondary publication expected from 07.08.2021

Permalink: https://www.hzdr.de/publications/Publ-31558
Publ.-Id: 31558


Tailoring the Electronic and Magnetic Properties of Hematene by Surface Passivation: Insights from First-principles Calculations

Wei, Y.; Ghorbani Asl, M.; Krasheninnikov, A.

Exfoliation of atomically-thin layers from non-van der Waals bulk solids gave rise to the emergence of a new class of two-dimensional (2D) materials, such as hematene (Hm), a structure just a few atoms thick obtained from hematite. Due to a large number of unsaturated sites, Hm surface can be passivated under ambient conditions. Using density functional theory calculations, we investigate the effects of surface passivation with H and OH groups on Hm properties and demonstrate that the passivated surfaces are energetically favorable under oxygen-rich conditions. While the bare sheet is antiferromagnetic and possesses an indirect band gap of 0.93 eV, the hydrogenated sheets are half-metallic with a ferromagnetic ground state, and the fully hydroxylated sheets are antiferromagnetic with a larger band gap as compared to the bare system. The electronic structure of Hm can be further tuned by mechanical deformations. The band gap of fully passivated Hm increases monotonically with biaxial strain, hinting at potential applications of Hm in electromechanical devices.

Keywords: Two-dimensional materials; Hematene; Surface Passivation; First-principles Calculations

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  • Secondary publication expected from 24.09.2021

Permalink: https://www.hzdr.de/publications/Publ-31557
Publ.-Id: 31557


Anisotropy of the magnetocaloric effect: Example of Mn5Ge3

Maraytta, N.; Voigt, J.; Salazar Mejia, C.; Friese, K.; Scurschii, I.; Perßon, J.; Salman, S. M.; Brückel, T.

We have investigated the field direction dependence of thermo-magnetic behavior in single crystalline Mn5Ge3. The adiabatic temperature change ΔTad in pulsed fields, the isothermal entropy change ΔSiso calculated from static magnetization measurements, and heat capacity have been determined for fields parallel and perpendicular to the easy magnetic direction [001]. The isothermal magnetization measurements yield, furthermore, the uniaxial anisotropy constants in second and fourth order, K1 and K2. We discuss how the anisotropy affects the magneto-caloric effect (MCE) and compare the results to the related compound MnFe4Si3, which features an enhanced MCE, too, but instead exhibits strong easy plane anisotropy. Our study reveals the importance of magnetic anisotropy and opens new approaches for optimizing the performance of magnetocaloric materials in applications.

Permalink: https://www.hzdr.de/publications/Publ-31553
Publ.-Id: 31553


Pulsed laser deposition of Fe-oxypnictides: Co- and F-substitution

Haindl, S.; Sato, M.; Wurmehl, S.; Büchner, B.; Kampert, W. A. G.

The majority of thin film studies that were devoted to Fe-oxyarsenides has focused so far on F-substituted (i.e. indirectly electron doped) LnOFeAs (Ln = La, Nd, Sm). Here we turn our attention towards Co-substituted (i.e. directly electron doped) LaOFeAs and SmOFeAs in order to investigate its growth on different substrate materials by using pulsed laser deposition (PLD). We detected dominant LnOFeAs phase formation and discuss the occurrence of minor impurity phases in the different films on different substrates. The lack of a superconducting transition in LnOFe0.85Co0.15As films on MgO(100) could be due to strain, since we observe an onset of superconductivity in SmOFe1−xCoxAs (x = 0.07, 0.15) films on other oxide substrates. In addition, Co-substitution (i.e. within the Fe2As2 layers) and F-substitution (i.e. within the Ln2O2 layers) leading to direct and indirect electron doping respectively, appears for films deposited on CaF2 substrates. In contrast to the F-substituted but Co-free Fe-oxyarsenides, the co-doped SmO1−xFxFe0.85Co0.15As film has experimentally accessible upper critical fields down to the lowest temperatures and may serve as an ideal test bed for further theoretical modeling of Fe-oxyarsenides.

Permalink: https://www.hzdr.de/publications/Publ-31552
Publ.-Id: 31552


Preparation of γ-Al₂O₃/α-Al₂O₃ ceramic foams as catalyst carriers via the replica technique

Shumilov, V.; Kirilin, A.; Tokarev, A.; Boden, S.; Schubert, M.; Hampel, U.; Hupa, L.; Salmi, T.; Murzin, D. Y.

This work describes an effective method for the preparation of open-cell ceramic foams for their further use as catalyst supports. The polyurethane sponge replica technique was applied using a ceramic suspension based on a mixture of α-alumina, magnesia and titania and polyvinyl alcohol solution as a liquid component. The polyurethane sponge was etched with NaOH and covered with colloidal silica to obtain better adhesion of the slurry to the walls of the polymeric material onto it. The surface area of the ceramic carrier was increased by adding a layer of γ-alumina. Deposition of an active catalytic phase (Pt) was done by impregnation. Properties of the carriers and the final catalyst were investigated by a number of physico-chemical methods such as TEM, SEM, XRD and computer tomography. Hydrogenation of ethyl benzoylformate was performed to elucidate the catalytic properties of foam catalysts illustrating their applicability.

Keywords: γ-Al₂O₃/α-Al₂O₃; catalytic foams; macroporous ceramics; hydrogenation of ethylbenzoylformate

Permalink: https://www.hzdr.de/publications/Publ-31551
Publ.-Id: 31551


Single-Shot Measurement of Post-Pulse-GeneratedPre-Pulse in High-Power Laser Systems

Kon, A.; Nishiuchi, M.; Kiriyama, H.; Kando, M.; Bock, S.; Ziegler, T.; Püschel, T.; Zeil, K.; Schramm, U.; Kondo, K.

In this study, a detailed investigation of the dynamics of the generation of pre-pulse bypost-pulses is presented, using single-shot self-referenced spectral interferometry (SRSI). The capabilityof SRSI in terms of the single-shot measurement of the temporal contrast of high-power lasersystems has been experimentally demonstrated. The results confirm that the energy levels of thepre-pulses increase proportional to the square of the B-integral parametrizing the nonlinearity of theamplifier chain.

Keywords: laser pulse contrast; high-intensity lasers; B-integral

Permalink: https://www.hzdr.de/publications/Publ-31549
Publ.-Id: 31549


Supplementary simulations for laser foil experiments on TOD variation

Göthel, I.

Simulations made with PIConGPU in 2d geometry with a longitudinally modified gaussian laser on a foil.
The laser has been modified to reproduce the main features of the pulse shape seen in the experiments as a result of modifying TOD and GVD.
The three main features, which were enabled with varying strength in the simulations:
 - an exponential ramp on the timescale of 300fs before the gaussian main pulse
 - a postpulse with around 100fs delay and around 0.2 of the total pulse energy
 - a skewness of the gaussian - modelled by two gaussian halves for the rising and falling part

From the spectra of the accelerated protons the cutoff energy is measured. The main result is, that the variations of the spectra are much smaller than those observed in the experiments, suggesting more complex mechanisms than those modelled here.

Keywords: laser particle acceleration

  • Software in the HZDR data repository RODARE
    Publication date: 2020-09-22
    DOI: 10.14278/rodare.521
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31548
Publ.-Id: 31548


Single-shot diagnostics development for high power laser driven relativistic plasma experiments at the Helmholtz-Zentrum Dresden-Rossendorf

Bock, S.; Püschel, T.; Helbig, U.; Gebhardt, R.; Oksenhendler, T.; Bernert, C.; Couperus Cabadağ, J. P.; Ziegler, T.; Schöbel, S.; Zeil, K.; Irman, A.; Toncian, T.; Cowan, T.; Schramm, U.

At the HZDR TO-AC contrast measurement tools and newly developed single-shot diagnostics characterizing laser pulses are applied for laser improvements and particle acceleration experiments. An overview of the applied techniques and recent results is presented.

  • Invited lecture (Conferences) (Online presentation)
    CLEO 2020, 11.-15.05.2020, San Jose, California, USA

Permalink: https://www.hzdr.de/publications/Publ-31547
Publ.-Id: 31547


Control of magneto-optical properties of cobalt-layers by adsorption of α-helical polyalanine self-assembled monolayers

Sharma, A.; Matthes, P.; Soldatov, I.; Arekapudi, S. S. P. K.; Böhm, B.; Lindner, M.; Selyshchev, O.; Thi, N. H. N.; Mehring, M.; Tegenkamp, C.; Schulz, S. E.; Zahn, D. R. T.; Paltiel, Y.; Hellwig, O.; Salvan, G.

The adsorption of chiral molecules was recently shown to trigger a change in the magnetisation of mesoscopic magnetic domains in a ferromagnetic underlayer. In this work, we investigated the macroscopic (magneto-)optical response of chemisorbed α-helical polyalanine self-assembled monolayers (SAMs) on a gold and gold-capped-cobalt thin film on Au substrates using spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy and microscopy. The optical and magneto-optical spectra reveal selective chemisorption of the α-helical polyalanine molecules depending on the orientation of the substrate remanent magnetisation during the SAMs process. Moreover, a sign change of the magneto-optical response was observed in some of the magnetic substrates after the chiral SAMs formation.

Permalink: https://www.hzdr.de/publications/Publ-31546
Publ.-Id: 31546


Characterization of Accumulated B-Integral of Regenerative Amplifier Based CPA Systems

Bock, S.; Marie Herrmann, F.; Püschel, T.; Helbig, U.; Gebhardt, R.; Johannes Lötfering, J.; Pausch, R.; Zeil, K.; Ziegler, T.; Irman, A.; Oksenhendler, T.; Kon, A.; Nishuishi, M.; Kiriyama, H.; Kondo, K.; Toncian, T.; Schramm, U.

We report on a new approach to measure the accumulated B-integral in the regenerative and multipass amplifier stages of ultrashort-pulse high-power laser systems by B-integral-induced coupling between delayed test post-pulses and the main pulse. A numerical model for such non-linear pulse coupling is presented and compared to data taken at the high-power laser Draco with self-referenced spectral interferometry (SRSI). The dependence of the B-integral accumulated in the regenerative amplifier on its operation mode enables optimization strategies for extracted energy vs. collected B-integral. The technique presented here can, in principle, be applied to characterize any type of ultrashort pulse laser system and is essential for pre-pulse reduction.

Keywords: Petawatt laser; temporal pulse contrast; B-integral; self-referenced spectral interferometry

Permalink: https://www.hzdr.de/publications/Publ-31545
Publ.-Id: 31545


Fluid Mechanics of Liquid Metal Batteries

Weier, T.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Weber, N.

The quest for renewable energy sources entails an increasingly intermittent electricity supply.
Transmission grid updates can only partially account for balancing the resulting variations and large-scale stationary storage will gain importance in future energy landscapes dominated by volatile sources.
Today’s battery technologies were, with the notable exception of redox-flow batteries, mainly designed for and driven by mobile applications. Those prioritize properties (energy density, power rating) that are less important for stationary storage. Thus, battery technologies developed from the ground up to meet the needs of stationary storage have the potential to much better address the specifics of huge capacity installations.
Liquid metal batteries (LMBs) are a new technology for grid-scale energy storage, see [1] for a comprehensive review. They consist of all liquid cells that operate with liquid metals as electrodes and molten salts as electrolytes. The liquids separate into three stably stratified layers by virtue of density and mutual immiscibility (see the two upper left inserts in Fig. 1a). This conceptually very simple and self-assembling structure has the unique advantage to allow for an easy scale-up at the cell level: single-cell cross sections can potentially reach several square-meters. Such cell sizes enable highly favourable and otherwise unattainable ratios of active to construction material because of the cubic scaling (volume) of the former and the quadratic scaling (surface) of the latter. The total costs should therefore largely be determined by those of the active materials.
The talk will start with a general introduction to LMBs and then focus on the fluid mechanics in these devices [2]. Electric currents, magnetic fields, and heat and mass transfer are tightly coupled with the cells’ electrochemistry. First a number of fluid dynamic instabilities will be discussed in relation to operational safety. The remainder of the talk will deal with transport phenomena in the positive electrode. While transport in most modern battery systems is typically dominated by diffusion and migration in micrometer-scale liquid layers and solids, convection - with exception of the aforementioned redox-flow batteries - rarely plays a role. This is in stark contrast to LMBs were mediated by the fully liquid interior fluid flow can be driven by various mechanisms. The influence of solutal convection on the cycling behavior of a cell (Fig. 1a) will be demonstrated. Electromagnetically induced convection can be used to improve mixing (Fig. 1b) thereby mitigating diffusion overpotentials.

Keywords: liquid metal batteries; electro-vortex flows; mass transfer; solutal convection

  • Invited lecture (Conferences) (Online presentation)
    Department Seminar Mechanical Engineering Department, 16.10.2020, Dearborn, MI, USA

Permalink: https://www.hzdr.de/publications/Publ-31544
Publ.-Id: 31544


Investigation of Mild Steel Corrosion in the Cement Production Associated with the Usage of Secondary Fuels

Thieme, M.; Bergmann, U.; Kiesewetter, A.; Wehry, T.; Potzger, K.; Zarzycki, A.; Marszalek, M.; Worch, H.

The present work deals with the corrosion of mild steel (1.0037) used as the outer construction material of the preheater of a modern industrial cement production facility. The facility uses secondary fuels, which introduce considerable amounts of corrosive species. The situation at the examination sites in the preheater zone is tracked over a period of two years including operation and shut-down periods. The investigation is focused on (i) the acquisition of the underlying physicochemical conditions, such as moisture, temperature, and contamination data at the examination site of the preheater, (ii) the multianalytical identification of the formed corrosion products using scanning electron microscopy combined with energy-dispersive X-ray analysis, infrared spectrometry, Raman spectrometry, X-ray diffractometry, and Möβbauer spectrometry, and (iii) voltammetric and EIS laboratory investigations using model solutions. It was evidenced that corrosion takes place at a temperature level of about 100°C in the presence of moisture and oxygen as well as chloride ion as a consequence of the usage of secondary fuels. Typical hot-gas corrosion could be excluded under the current conditions. Appearance, structure, and nature of the corrosion products were found to be not mainly dependent on the varied length of exposure, but on the conditions of the hosting preheater intake. In addition to different FeOOH phases and hematite, magnetite was found, dependent on the oxygen concentration in the process gas. The decisive role of oxygen as key factor for the corrosion rate was electrochemically confirmed.

Keywords: Mössbauer spectroscopy; corrosion

Permalink: https://www.hzdr.de/publications/Publ-31541
Publ.-Id: 31541


Dosimetry with the ability to distinguish pulsed and non-pulsed dose contributions

Makarevich, K.; Beyer, R.; Henniger, J.; Ma, Y.; Polter, S.; Sommer, M.; Teichmann, T.; Weinberger, D.; Kormoll, T.

The concept of an active dosimetry system for pulsed radiation dose rate measurements is presented. Real-time distinction of pulsed and non-pulsed radiation contributions is based on the time structure of a single interaction. A fast tissue equivalent plastic scintillator is exploited to minimize the pile-up effect influence on absorbed energy measurements. Being connected to a fully digital signal processing board, the detector creates an active dosimetry system with adjustable parameters. With this system, absorbed dose rate measurements were carried out in a photon field with a time structure mimicking a radiotherapeutic beam, but also in the presence of a constant radiation field. Measurements show a linear dependence of a pulsed radiation contribution on the accelerator current in the investigated range of the total dose rate up to 8 μGy h⁻¹. While increasing the accelerator current by 1 μA, the pulsed radiation dose rate grows by (26.2±0.9) nGy h⁻¹ when considering pile-up events.

Keywords: gELBE; dosimetry

Permalink: https://www.hzdr.de/publications/Publ-31540
Publ.-Id: 31540


Comprehensive analysis of tumour sub-volumes for radiomic risk modelling in locally advanced HNSCC

Leger, S.; Zwanenburg, A.; Leger, K.; Lohaus, F.; Linge, A.; Schreiber, A.; Kalinauskaite, G.; Tinhofer, I.; Guberina, N.; Guberina, M.; Balermpas, P.; Von, D. G. J.; Ganswindt, U.; Belka, C.; Peeken, J.; Combs, S.; Böke, S.; Zips, D.; Richter, C.; Krause, M.; Baumann, M.; Troost, E. G. C.; Löck, S.

Radiomics aims to characterise the tumour phenotype using advanced image features to predict patient-specific outcome. ...

Keywords: radionmic; image-based risk modelling; machine learning; personalised therapy; radiation oncology

Permalink: https://www.hzdr.de/publications/Publ-31539
Publ.-Id: 31539


CT-based attenuation correction of whole-body radiotherapy treatment positioning devices in PET/MRI hybrid imaging

Taeubert, L.; Berker, Y.; Beuthien-Baumann, B.; Hoffmann, A. L.; Troost, E. G. C.; Kachelrieß, M.; Gillmann, C.

Objective To implement Computed Tomography (CT)-based attenuation maps of radiotherapy (RT) positioning hardware and radiofrequency (RF) coils to enable hybrid positron emission tomography/magnetic resonance imaging (PET/MRI)-based RT treatment planning. Materials and Methods The RT positioning hardware consisted of a flat RT table overlay, coil holders for abdominal scans, coil holders for head and neck scans and an MRI compatible hip and leg immobilization system. CT images of each hardware element were acquired on a CT scanner. Based on the CT images, attenuation maps of the devices were created. Validation measurements were performed on a PET/MR scanner using a 68Ge phantom (48 MBq, 10 min scan time). Scans with each device in treatment position were performed. Then, reference scans containing only the phantom were taken. The scans were reconstructed online (at the PET/MRI scanner) and offline (via e7tools on a PC) using identical reconstruction parameters. Average reconstructed activity concentrations of the device and reference scans were compared. Results The device attenuation maps were successfully implemented. The RT positioning devices caused an average decrease of reconstructed PET activity concentration in the range between -8.3 ± 2.1 % (mean ± SD) (head and neck coil holder with coils) to -1.0 ± 0.5 % (abdominal coil holder). With attenuation correction taking into account RT hardware, these values were reduced to -2.0 ± 1.2 % and 0.6 ± 0.5 %, respectively. The results of the offline and online reconstructions were nearly identical, with a difference of up to 0.2 %. Conclusion The decrease in reconstructed activity concentration caused by the RT positioning devices is clinically relevant and can successfully be corrected using CT-based attenuation maps. Both the offline and online reconstruction methods are viable options.

Permalink: https://www.hzdr.de/publications/Publ-31536
Publ.-Id: 31536


Wafer-scale 4H-silicon carbide-on-insulator (4H–SiCOI) platform for nonlinear integrated optical devices

Yi, A.; Zheng, Y.; Huang, H.; Lin, J.; Yan, Y.; You, T.; Huang, K.; Zhang, S.; Shen, C.; Zhou, M.; Huang, W.; Zhang, J.; Zhou, S.; Ou, H.; Ou, X.

4H-silicon carbide-on-insulator (4H–SiCOI) serves as a novel and high efficient integration platform for nonlinear optics and quantum photonics. The realization of wafer-scale fabrication of single-crystalline semi-insulating 4H–SiC film on Si (100) substrate using the ion-cutting and layer transferring technique was demonstrated in this work. The thermodynamics of 4H–SiC surface blistering is investigated via observing the blistering phenomenon with a series of implanted fluences and annealing temperatures. Surface tomography and the depth dependent film quality of the 4H–SiC have been extensively studied by employing scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, X-ray diffraction (XRD) was carried out and the diffraction spectrum reveals a narrow peak with a full width at half maximum (FWHM) of 75.6 arcsec, indicating a good maintenance of the single-crystalline phase for the prepared thin film of 4H–SiC as compared to its bulk counterpart. With the single-crystalline 4H–SiCOI, we have successfully fabricated a micro-ring resonator with a quality factor as high as 6.6 × 104. The reported 4H–SiCOI wafer provides a feasible monolithic platform for integrated photonic applications.

Permalink: https://www.hzdr.de/publications/Publ-31534
Publ.-Id: 31534


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