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41709 Publications

Theoretical Prediction of Mass Transfer Coefficients in Two-Phase and Slurry Bubble Columns

Nedeltchev, S.

Abstract

Two-phase and slurry bubble columns are characterized with high volumetric mass transfer coefficients kLa at low energy input. The design, modelling, optimization and scale-up of these reactors require precise knowledge of the mass transfer parameters. The mass transfer coefficients determine the efficiency and dimensions of (slurry) bubble columns. Nedeltchev et al. (2007) developed a correlation for prediction of mass transfer coefficients in gas-liquid bubble columns operated in the homogeneous flow regime. It was based on experimental gas holdups. On the other hand, Nedeltchev and Schumpe (2008) developed a correlation for prediction of gas holdups in gas-liquid bubble columns operated in the homogeneous regime. In this work, the theoretically calculated gas holdups were substituted in the mass transfer model (in the correlation for the interfacial area) of Nedeltchev et al. (2007) and the mass transfer coefficients were recalculated by means of a purely theoretical approach. The same gases and liquids (18 pure organic liquids, 14 adjusted liquid mixtures and tap water) were used and 263 kLa values (only in the homogeneous regime) were successfully predicted at ambient and high pressures (up to 1 MPa).
The same approach was tested in a slurry bubble column. Nedeltchev et al. (2014) predicted successfully the experimental mass transfer coefficients in a slurry bubble column based on bubble sizes which depended on the experimental gas holdups. On the other hand, Nedeltchev (2014) established a new approach for predicting the gas holdups in a slurry bubble column. When these theoretical gas holdups were substituted in the mass transfer model (in the correlations for prediction of bubble size and interfacial area), a purely theoretical kLa values in a slurry bubble column were obtained. The predictions were good not only in the homogeneous regime but also in the heterogeneous regime. The theoretical approach was applicable up to relatively high (18 %) solids concentrations. Six different liquid-solid systems were used and 66 kLa values were successfully predicted. In both mass transfer models, correction factors (a function of Eӧtvӧs numbers) were introduced due to the non-spherical (ellipsoidal) shape of the bubbles.

Keywords: Mass transfer coefficients; Penetration theory; New contact time; Gas-liquid bubble columns; Slurry bubble columns

  • Lecture (Conference)
    12th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS12), 28.06.-01.07.2015, New York, USA

Permalink: https://www.hzdr.de/publications/Publ-22237


Hydrothermal Alteration of Trachyte Satellite Intrusions in the Cripple Creek District

Rahfeld, A.; Kelly, N.; Monecke, T.

Abstract

The Cripple Creek deposit located in southwestern Colorado represents one of the largest epithermal gold deposits hosted by alkaline volcanic rocks. A petrographic study of the mostly barren satellite intrusions surrounding the deposit was undertaken to investigate and identify regional alteration patterns. Transmitted light, optical cathodoluminescence, and scanning electron microscopy, integrated with whole-rock geochemical data, revealed a complex history of fluid-rock interaction.
Early albitization of trachyte is preserved within weakly potassic-altered rocks. In more intensely altered rocks, potassium feldspar pervasively replaced the sanidine-dominated groundmass. Late alteration of the trachyte involved the formation of white mica and later kaolinite. The mineralogical changes imply a change in the physiochemical conditions of alteration from early sodic to later potassic alteration, followed by alteration caused at progressively decreasing temperatures and increasing acidity.
Tephrite intrusions within the trachyte satellite bodies have not been influenced by these styles of alteration. The tephrite has been altered to Fe-hydroxide minerals and biotite, most likely caused by influx of Fe-rich fluids. Within the mineralized trachyte of the main diatreme, Au-Te mineralization is at least locally associated with this style of Fe-rich alteration.

Keywords: Alkaline rocks; epithermal deposits; Cripple Creek; hydrothermal Alteration

  • Poster
    13th SGA Biennial Meeting (SGA2015), 24.-27.08.2015, Nancy, Frankreich
  • Contribution to proceedings
    13th SGA Biennial Meeting (SGA2015), 24.-27.08.2015, Nancy, Frankreich
    Mineral resources in a sustainable world. 13th SGA Biennial Meeting (SGA2015)

Permalink: https://www.hzdr.de/publications/Publ-22236


Geochemical and Mineralogical Analysis of Kupferschiefer

Rahfeld, A.; Möckel, R.; Gutzmer, J.

Abstract

Kupferschiefer, i.e. very fine-grained and disseminated polymetallic Cu-Ag ores of the extensive stratabound deposits of the Central European Copperbelt is well known for its mineralogical complexity and the challenges surrounding its characterization. It is marked by a combination of high metal sulfide contents (up to 25 wt%) and organic matter (up to 30 wt%) within a matrix predominantly composed of fine-grained clay and carbonate minerals. Conventional analytical procedures often yield unreliable results of this very complex raw material. Regardless, recent research into the hydrometallurgical and microbiological beneficiation of Kupferschiefer has raised the demand for supplying reliable quantitative data of the mineralogy and the geochemistry for both the raw material and process samples. A research project was thus initiative to establish a robust analytical procedure to quantify both mineralogical as well as geochemical attributes of Kupferschiefer-type ores. A combination of analytical techniques is employed for this purpose, including quantitative X-ray diffraction (QXRD), image analysis based on scanning electron microscopy/mineral liberation analysis (MLA), XRF, ICP-AES, and INAA. Method development was based on selected Kupferschiefer samples obtained from Sangerhausen (Germany) and Polkowice-Sieroszowice (Poland) deposits.

QXRD by Rietveld refinement is particularly well-suited to determine the modal mineralogy of fine-grained samples. Five types of layer silicates were identified in Kupferschiefer samples. These are being characterized in detail in order to build crystal structure files needed to enable a full quantification of the minerals present. The necessary characterization of this set of layer silicates has been inhibited by the presence of organic matter, requiring chemical pre-treatment of the raw material that is specifically developed for this purpose.
SEM-based mineral liberation analysis (MLA) on grain mounts of crushed aliquots of the powder samples used for QXRD is used to verify mineral identification and to determine the amounts, liberation, and types of sulphide minerals contained in the samples. This technique is not suited to determine the abundance of the silicate minerals due to their fine-grained and intimately intergrown texture. Further obstacles, such as misidentification of disordered carbonate minerals by XRD or copper sulfides by MLA, are encountered often and can only be recognized and minimized by verifying results using multiple analytical methods. Independent observations from microscopy or bulk geochemistry by fusion XRF are useful in ensuring a high data quality and to test for consistency.
Whole rock trace element data are acquired using INAA, XRF, and ICP-OES. While INAA can guarantee a full analysis without requiring a problematic digestion treatment, the procedure itself is not available for routine measurements. XRF analysis of pressed pellets has been inhibited by the variable content of organic material and matrix effects caused by high sulfide concentrations. ICP-AES/MS analysis is considered to be the most appropriate technique in this case. Different combinations of hydrogen peroxide, nitric acid, and perchloric acid digestion techniques are tested to identify an optimal procedure for the acid digestion of the diverse sulfide compounds as well as the organic matter contained in Kupferschiefer.

Keywords: Kupferschiefer; Analysis; XRD; MLA; XRF; TXRF; ICP-OES; INAA

  • Poster
    The 9th International Conference on the Analysis of Geological and Environmental Materials - Geoanalysis 2015, 10.-13.08.2015, Leoben, Östereich

Permalink: https://www.hzdr.de/publications/Publ-22235


Multiscale structural characterizations of mixed U(IV)-An(III) oxalates (An(III) = Pu or Am) combining XAS and XRD measurements

Arab-Chapelet, B.; Martin, P.; Costenoble, S.; Delahaye, T.; Scheinost, A. C.; Grandjean, S.; Abraham, F.

Abstract

Mixed actinides(III,IV) oxalates of general formula M2.2UIV1.8AnIII0.2(C2O4)5·nH2O (An = Pu or Am and M = H3O+ and N2H5+) have been quantitatively precipitated by oxalic precipitation in nitric medium (yield> 99%). Thorough multiscale structural characterizations by XRD and XAS measurements evidenced the existence of oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium are kept during the precipitation step. The local environments around U+IV, Pu+III and Am+III determined by EXAFS measurements are similar and show that cations are surrounded by five oxalate ligands. The mean metal-oxygen distances by XAS measurements are in agreement with those calculated from XRD lattice parameters. Finally, these An(III)-An(IV) oxalate solid solutions can be used to synthetize mixed actinide oxides characterized by a high homogeneity at molecular scale.

Keywords: Plutonium; Americium; XAFS; XRD; nuclear fuel; transmutation

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Permalink: https://www.hzdr.de/publications/Publ-22234


Extremely large magnetoresistance and ultrahigh mobility in the topological Weyl semimetal candidate NbP

Shekhar, C.; Nayak, A. K.; Sun, Y.; Schmidt, M.; Nicklas, M.; Leermakers, I.; Zeitler, U.; Skourski, Y.; Wosnitza, J.; Liu, Z.; Chen, Y.; Schnelle, W.; Borrmann, H.; Grin, Y.; Felser, C.; Yan, B.

Abstract

Recent experiments have revealed spectacular transport properties in semimetals, such as the large, non-saturating magnetoresistance exhibited by WTe2. Topological semimetals with massless relativistic electrons have also been predicted as three-dimensional analogues of graphene. These systems are known as Weyl semimetals, and are predicted to have a range of exotic transport properties and surface states, distinct from those of topological insulators. Here we examine the magneto-transport properties of NbP, a material the band structure of which has been predicted to combine the hallmarks of a Weyl semimetal with those of a normal semimetal. We observe an extremely large magnetoresistance of 850,000% at 1.85 K (250% at room temperature) in a magnetic field of up to 9 T, without any signs of saturation, and an ultrahigh carrier mobility of 5x106 cm2 V-1 s-1 that is accompanied by strong Shubnikov–de Haas (SdH) oscillations. NbP therefore presents a unique example of a material combining topological and conventional electronic phases, with intriguing physical properties resulting from their interplay.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22233


Controllable Broadband Absorption in the Mixed Phase of Metamagnets

Pregelj, M.; Zaharko, O.; Zorko, A.; Gomilsek, M.; Sendetskyi, O.; Günther, A.; Ozerov, M.; Zvyagin, S. A.; Luetkens, H.; Baines, C.; Tsurkan, V.; Loidl, A.

Abstract

Materials with broad absorption bands are highly desirable for electromagnetic filtering and processing applications, especially if the absorption can be externally controlled. Here, a new class of broadband-absorption materials is introduced. Namely, layered metamagnets exhibit an electromagnetic excitation continuum in the magnetic-field-induced mixed ferro-and anti-ferromagnetic phase. Employing a series of complementary experimental techniques involving neutron scattering, muon spin relaxation, specific heat, ac and dc magnetization measurements, and electron magnetic resonance, a detailed magnetic phase diagram of Cu3Bi(SeO3)2O2Br is determined and it is found that the excitations in the mixed phase extend over at least ten decades of frequency. The results, which reveal a new dynamical aspect of the mixed phase in metamagnets, open up a novel approach to controllable microwave filtering.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22232


Depth Resolved Structural and Compositional Characterization of Ion-Implanted Polystyrene that Enables Direct Covalent Immobilization of Biomolecules

Bilek, M. M. M.; Kondyurin, A.; Dekker, S. A.; Steel, B. C.; Wilhelm, R. A.; Heller, R.; Mckenzie, D. R.; Weiss, A. S.; James, M.; Möller, W.

Abstract

A polystyrene film spun onto polished silicon substrates was implanted with argon ions using plasma immersion ion implantation (PIII) in order to activate its surface for single step immobilization of biological molecules. The film was subsequently investigated by X-ray and neutron reflectometry, ultraviolet (UV)-visible (VIS) and Fourier transform infrared (FTIR) ellipsometry, FTIR and Raman spectroscopy, as well as nuclear reaction analysis to determine the structural and compositional transformations associated with the surface activation. The ion irradiation resulted in a significant densification of the carbon structure, which was accompanied by hydrogen loss. The density and hydrogen profiles in the modified surface layers were found to agree with the expected depths of ion implantation as calculated by the Stopping and Range of Ions in Matter (SRIM) software. The data demonstrate that the reduction in film thickness is due to ion-induced densification rather than the removal of material by etching. Characterization by FTIR, atomic force microscopy (AFM), ellipsometry and X-ray reflectometry shows that polystyrene films modified in this way immobilize dense layers of protein (tropoelastin) directly from solution. A substantial fraction of the immobilized protein layer remains after rigorous washing with sodium dodecyl sulfate solution, indicating that its immobilization is by covalent bonding.

Keywords: Plasma immersion ion implantation; polystyrene; protein immobilization; nuclear reaction analysis; X-ray reflectometry; neutron reflectometry; spectroscopic ellipsometry; Raman and FTIR spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-22230


An investigation of the interactions of Eu3+ and Am3+ with uranyl minerals: implications for the storage of spent nuclear fuel

Biswas, S.; Steudtner, R.; Schmidt, M.; Mckenna, C.; Vintró, L. L.; Twamley, B.; Baker, R. J.

Abstract

The reaction of a number of uranyl minerals of the (oxy)hydroxide, phosphate and carbonate types with Eu(III), as a surrogate for Am(III), have been investigated. A photoluminescence study shows that Eu(III) can interact with the uranyl minerals Ca[(UO2)6(O)4(OH)6]·8H2O (becquerelite) and A[UO2(CO3)3]·xH2O (A/x = K3Na/1, grimselite; CaNa2/6, andersonite; and Ca2/11, liebigite). For the minerals [(UO2)8(O)2(OH)12]·12H2O (schoepite), K2[(UO2)6(O)4(OH)6]·7H2O (compreignacite), A[(UO2)2(PO4)2]·8H2O (A = Ca, meta-autunite; Cu, meta-torbernite) and Cu[(UO2)2(SiO3OH)2]·6H2O (cuprosklodowskite) no Eu(III) emission was observed, indicating no incorporation into, or sorption onto the structure. In the examples with Eu3+ incorporation, sensitized emission is seen and the lifetimes, hydration numbers and quantum yields have been determined. Time Resolved Laser Induced Fluorescence Spectroscopy (TRLFS) at 10 K have also been measured and the resolution enhancements at these temperatures allow further information to be derived on the sites of Eu(III) incorporation. Infrared and Raman spectra are recorded, and SEM analysis show significant morphology changes and the substitution of particularly Ca2+ by Eu3+ ions. Therefore, Eu3+ can substitute Ca2+ in the interlayers of becquerelite and liebigite and in the structure of andersonite, whilst in grimselite only sodium is exchanged. These results have guided an investigation into the reactions with 241Am on a tracer scale and results from gamma-spectrometry show that becquerelite, andersonite, grimselite, liebigite and compreignacite can include americium in the structure. Shifts in the U=O and C-O Raman active bands are similar to that observed in the Eu(III) analogues and Am(III) photoluminescence measurements are also reported on these phases; the Am3+ ion quenches the emission from the uranyl ion. An unusual structure of a 3D uranyl framework is also reported.

Keywords: uranium; europium; emission spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-22229


Polymer and cluster chemistry of tetravalent cerium in aqueous solutions - Comparison with tetravalent actinides

Ikeda-Ohno, A.; Weiss, S.; Hennig, C.

Abstract

Cerium (Ce) is known to be the only lanthanide (Ln) which can be stabilized in the tetravalent state (i.e., Ce(IV)) in aqueous solutions. Owing to this chemical specificity, the aqueous chemistry of Ce(IV) shows unique characters as compared to that for the other Ln. For instance, due to its high charge density, the aqueous chemistry of Ce(IV) is predominantly characterised by strong hydrolysis. This strong hydrolysis results in the formation of a variety of hydroxide species even under acidic conditions.1 Moreover, the hydrolysis of Ce(IV) is often a primary step of many wet syntheses to yield nano-sized CeO2 particles which have many technological applications. Despite these chemical uniqueness and importance in applications, the aqueous chemistry of Ce(IV) is poorly understood even to date. Based on this background, this study aims to comprehensively understand the chemical behaviour of Ce(IV) in aqueous solutions by combining several spectroscopic (XAS, HEXS, DLS) and microscopic (TEM) techniques.

Keywords: f-elements; lanthanides; actinides; tetravalent; hydrolysis; aqueous solution; X-ray spectroscopy; TEM

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  • Lecture (Conference)
    The 9th International Conference on f-Elements (ICfE 9), 08.09.2015, Oxford, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-22228


Bimodal grain size distribution of nanostructured ferritic ODS Fe-Cr alloys

Hilger, I.; Bergner, F.; Weißgärber, T.

Abstract

Oxide dispersion strengthened Fe-Cr alloys produced by mechanical alloying and spark plasma sintering were found to form different heterogeneous hardness distribution and microstructures depending on the milling parameters. Microstructure investigations by means of electron diffraction techniques and atom probe tomography revealed the presence of large particle-free zones in one material, which is, together with the inhomogeneous deformation at short milling times, considered the main reason for the formation of a heterogeneous microstructure. The inhomogeneous temperature distribution in the sample volume during the sintering process is also expected to contribute to the formation of a heterogeneous grain size distribution in the final material.

Keywords: Spark plasma sintering; bimodal grain size; EBSD; Atom probe tomography; Nanoindentation; microstructure

Permalink: https://www.hzdr.de/publications/Publ-22227


Response of GaN to energetic ion irradiation: conditions for ion track formation

Karlušić, M.; Kozubek, R.; Lebius, H.; Ban-D’Etat, B.; Wilhelm, R. A.; Buljan, M.; Siketić, Z.; Scholz, F.; Meisch, T.; Jakšić, M.; Bernstorff, S.; Schleberger, M.; Šantić, B.

Abstract

We investigated the response of wurzite GaN thin films to energetic ion irradiation. Both swift heavy ions (92 MeV Xe23+, 23 MeV I6+) and highly charged ions (100 keV Xe40+) were used. After irradiation, the samples were investigated using atomic force microscopy, grazing incidence small angle x-ray scattering, Rutherford backscattering spectroscopy in channelling orientation and time of flight elastic recoil detection analysis. Only grazing incidence swift heavy ion irradiation induced changes on the surface of the GaN, when the appearance of nanoholes is accompanied by a notable loss of nitrogen. The results are discussed in the framework of the thermal spike model.

Keywords: GaN; swift heavy ion; highly charged ion; ion track; thermal spike

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Permalink: https://www.hzdr.de/publications/Publ-22226


Formation of shallow boron emitters in crystalline silicon using flash lamp annealing: Role of excess silicon interstitials

Riise, H. N.; Schumann, T.; Azarov, A.; Hübner, R.; Skorupa, W.; Svensson, B. G.; Monakhov, E.

Abstract

Shallow, Boron (B)-doped p+ emitters have been realized using spin-on deposition and Flash Lamp Annealing (FLA) to diffuse B into monocrystalline float zone Silicon (Si). The emitters extend between 50 and 140 nm in depth below the surface, have peak concentrations between 9x1019 cm-3 and 3x1020 cm-3, and exhibit sheet resistances between 70 and 3000 Ohm/Square. An exceptionally large increase in B diffusion occurs for FLA energy densities exceeding approximately 93 J/cm2 irrespective of 10 or 20 ms pulse duration. The effect is attributed to enhanced diffusion of B caused by Si interstitial injection following a thermally activated reaction between the spin-on diffusant film and the silicon wafer.

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Permalink: https://www.hzdr.de/publications/Publ-22225


Indium als Beiprodukt – Bedeutung von Geometallurgie und Rohstoffcharakterisierung

Frenzel, M.; Krause, J.; Bachmann, K.; Gutzmer, J.

Abstract

Anhand des Beispiels von Indium wird gezeigt wie geometallurgische Denkweisen und Methoden auf typische Beiprodukte angewendet werden können. Besonders für Elemente wie Gallium, Germanium, Selen und Tellur fehlen bisher leider ähnliche Arbeiten völlig. Es wäre daher wünschenswert, dass solche an ausgewählten Lagerstätten durchgeführt werden. Auch für typische Strafelemente wie Cadmium oder Arsen könnte dies sinnvoll sein. Allerdings würde der Fokus bei letzteren eher auf der Vermeidung ihrer Anreicherung in den Konzentraten liegen. Die hier vorgestellte Arbeit könnte für solche Studien als Muster dienen.

  • ACAMONTA - Zeitschrift des Vereins der Freunde und Förderer der TU Bergakademie Freiberg 22(2015), 25-28

Permalink: https://www.hzdr.de/publications/Publ-22224


Petrographic characterization of REE-Nb-Zr mineralization at the Dubbo trachyte, NSW Australia

Müller, C.; Mentoren: Schulz, B.; Atanasova, P.; Gutzmer, J.

Abstract

This thesis was the first study which intensively investigated the mineralisation and described the mineral transition between the supergene alterated and the main Toongi trachyte. Compared to other works on this trachyte the identified ore minerals differ. The works of Ramsden [1990, 1992] as well as the actually published mineral lists of Alkane resources Ltd. primarily deal with minerals of the supergene alterated zone. Within all three mineral lists there are major differences (cf. Table 5).
Due to the fact that this thesis, as well as the works of Ramsden, only used EDS measurements, a final evaluation is not possible.
The observed ore minerals often occur as small grains and as impregnation-like patches within the alterated matrix. Within the supergene alterated trachyte LREE are primary hosted by REEphosphates (monazite (Ce)) and zircon minerals, REE-fluorites (bastnaesite (Ce)) are not so important. HREE are primarily hosted by a Nb-Ta mineral. Major Nb hosting minerals are columbite and a Nb-Ta mineral. Zr is hosted by various Zr silicates, especially zircon. Within the main trachyte, LREE are hosted by REE-fluorites (bastnaesite (Ce)) and Zr-silicates (especially poikiloblastic zircon), REE-phosphates are not so important. HREE are primarily hosted by HREEY-(As) minerals. Major Zr hosting minerals are zircon and poikiloblastic zircon. Nb is primarily hosted by a Nb-Na mineral (natroniobite/lueshite) and less by a Nb-REE mineral. Most of the valuable minerals have a hydrothermal origin or they are products of alterated ores, respectively.
Only poikiloblastic zircon and Nb-Na-mineral have a magmatic origin.
Further investigations should confirm the mineral names by using more accurate measurements like X-Ray microanalysis. To determine the composition and temperature of the hydrothermal fluids the fluid inclusions should be investigated. Further investigations of samples out of the depths between 12 and 25 m (between sample DUB 5 and 6) could show the process of supergene mineral transformation more detailed.

Keywords: rare earth elements; metal deportment; trachyte

  • Master thesis
    TU Bergakademie Freiberg, 2015
    Mentor: Bernhard Schulz, Petya Atanasova, Jens Gutzmer
    116 Seiten

Permalink: https://www.hzdr.de/publications/Publ-22223


Distinguishing magmatic and metamorphic processes in the Norra Kärr alkaline complex, Southern Sweden

Atanasova, P.; Marks, M.; Krause, J.; Markl, G.; Gutzmer, J.

Abstract

The Norra Kärr rare metal deposit in Southern Sweden represents one of the largest resources of rare earth elements (REE) in Europe. The mineralization is hosted by deformed agpaitic nepheline syenites covering an area 350 by 1100 m in size. REE-bearing minerals include eudialyte-group minerals (EGM) and minor mosandrite and britholite-group minerals. Zr is hosted by catapleiite and EGM.
The intrusion was emplaced between 1.55-1.40 Ga within the Transscandinavian Igneous Belt in an anorogenic (post Svecofennian) environment and deformed and metamorphosed during the Sveconorwegian (Grenvillian) orogeny between 1.25-0.85 Ga (e.g. Andersson et al., 2007). Microtextures and compositional variations in clinopyroxene and EGM are used to distinguish magmatic and metamorphic processes during the evolution of this rare metal mineralization.
Clinopyroxenes are invariably sodic and are characterized by early magmatic Zr-rich cores, euhedrally overgrown by presumably late magmatic aegirine, anhedrally overgrown by metamorphic Al-rich aegirine (jadeite). Similarly, EGM show complex distribution patterns of major and minor elements suggesting multiphase influence of fractional crystallization, recrystallization, fluid-induced re-mobilization and late alteration.

  • Open Access Logo Contribution to proceedings
    Goldschmidt 2015, 17.-21.08.2015, Prag, Tschechische Republik
    Goldschmidt2015 Abstracts: Cambridge Publications, 138-138
  • Poster
    Goldschmidt 2015, 20.08.2015, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-22222


Mass of GaAsN in Pulsed Magnetic Fields up to 60 T with Free-Electron Laser IR Radiation

Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Helm, M.

Abstract

We use the unique combination of the widely tunable (4 μm – 250 μm) Free-Electron laser (FEL) FELBE and pulsed magnetic fields up to 60T of the High Magnetic Field Laboratory HLD to perform spectroscopic investigations on the dilute nitride system GaAsN. We carry out systematic cyclotron resonance (CR) spectroscopy and analyze the dependence of the electron effective mass on the nitrogen content. The red triangles in Figure 1 illustrate our findings for the illumination wavelength 46 μm at 100 K. We observe a slight increase of the effective mass with nitrogen content, which is in very good agreement with the Band Anti-Crossing (BAC) model [1], the empirical Tight Binding (TB) calculations [2] and the Two band BAC model [3], which are represented in Figure 1 by dashed, dotted and dash-dotted black lines, respectively. We compare our results with magneto-photoluminescence (PL) investigations performed by Alberi et al. [4] and Masia et al. [5], which are presented with blue circles and stars respectively. Magneto-PL investigations reveal a very fast increase of the effective mass with nitrogen content, well above the mentioned models [1-3], but consistent with the modified k·p calculations by Lindsay and O’Reilly [6]. Our magneto-PL study (not shown) exhibits a very similar behavior as shown by Alberi et al. and Masia et al., which allows us to exclude the different samples as a source for the deviation.
It is well known that nitrogen tends to form pairs and clusters during the growth, which is only considered in the modified k·p calculations [4]. Magneto-PL is a method which is very sensitive to localization of the neighboring atoms and thus to clusters. For this reason the magneto-PL results are consistent with [4], but cannot be described by [1-3], which do not take clusters into account. On the other hand, CR spectroscopy is only sensitive to delocalized states and this is why our results are in such good agreement with [1-3].

[1] J. Wu et al. Phys. Rev. B 64, 085320 (2000).
[2] N. Shtinkov et al. Phys. Rev. B 67, 081202(R) (2003).
[3] Tomic et al. Phys. Rev. B 69, 245305 (2004).
[4] Alberi et al. Phys. Rev. Lett. 110, 156405 (2013).
[5] Masia et al. Phys. Rev. B 73, 073201, (2006).
[6] A. Lindsay and E. P. O’Reilly Phys. Rev. Lett. 93, 196402 (2004).

Keywords: GaAsN; effective mass; cyclotron resonance spectroscopy; THz spectroscopy in pulsed magnetic fields

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  • Lecture (Conference)
    RHMF 2015; International Conference on Research in High Magnetic Fields 2015, 01.-04.07.2015, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-22221


Constraining big bang lithium production with recent solar neutrino data

Takács, M. P.; Bemmerer, D.; Szücs, T.; Zuber, K.

Abstract

The 3He(α, γ)7Be reaction affects not only the production of 7Li in Big Bang nucleosynthesis, but also the fluxes of 7Be and 8B neutrinos from the Sun. This double role is exploited here to constrain the former by the latter. A number of recent experiments on 3He(α,γ)7Be provide precise cross section data at E = 0.5-1.0 MeV center-of-mass energy. However, there is a scarcity of precise data at Big Bang energies, 0.1-0.5 MeV, and below. This problem can be alleviated, based on precisely calibrated 7Be and 8B neutrino fluxes from the Sun that are now available, assuming the neutrino flavour oscillation framework to be correct. These fluxes and the standard solar model are used here to determine the 3He(α,γ)7Be astrophysical S-factor at the solar Gamow peak, Sν (23+6 keV) 34 −5 = 0.548±0.054 keVb. This new data point is then included in a re-evaluation of the 3He(α,γ)7Be S-factor at Big Bang energies, following an approach recently developed for this reaction in the context of solar fusion studies. The re-evaluated S-factor curve is then used to re-determine the 3He(α,γ)7Be thermonuclear reaction rate at Big Bang energies. The predicted primordial lithium abundance is 7Li/H = 5.0 ×10−10, far higher than the Spite plateau.

Keywords: solar neutrinos; S34; Big Bang; Standard Solar Model

Permalink: https://www.hzdr.de/publications/Publ-22220


Cyclotron Resonance Spectroscopy of GaAsN in Pulsed Magnetic Fields up to 60 T with Free-Electron Laser IR Radiation

Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Pettinari, G.; Helm, M.

Abstract

The unique combination of the high magnetic field laboratory Dresden (HLD) and the free-electron laser facility FELBE allow us to perform cyclotron resonance spectroscopy experiments with tunable, intense, coherent infrared radiation of high brilliance in the range of 4 - 250 µm in pulsed magnetic fields up to 60 T. The material system of interest is the dilute nitride GaAsN, a promising candidate for electro-optical applications, because of its band gap tunability. The incorporation of a few percent of nitrogen into GaAs enables the gradual decrease of the band gap, which is proportional to the nitrogen content. The description of the band structure and in particular of the effective mass are still challenging despite the number of experimental works (e.g. [1, 2]) that have been performed on this system. In order to contribute to a clarification of this problem, we apply different investigation methods on one sample series of GaAsN with different nitrogen contents (0%; 0.1%; 0.2%).
Probably the most direct and reliable method for the investigation of the effective mass is cyclotron resonance spectroscopy, which has never been applied to bulk GaAsN layers before, according to our best knowledge. Figure 1 illustrates our CR spectroscopy investigation of three samples with different nitrogen contents illuminated with the FEL at wavelengths of 30 µm and 70 µm. These wavelengths have been chosen intentionally to investigate the effective mass behavior below and above the Reststrahlenband of GaAs. We discuss the significance of these CR studies, which were conducted using a range of temperatures, illumination wavelengths and n-type doping of the GaAsN layers. Using a simple Drude-like absorption model we deduce the electron CR mass, the electron mobility, the density of free carriers and the electron relaxation time.

References
[1] F. Masia et al., Phys. Rev. B 73, 07320 (2006).
[2] K. Alberi et al., Phys. Rev. Lett. 110, 156405 (2013).

Keywords: GaAsN; effective mass; cyclotron resonance spectroscopy; THz spectroscopy in pulsed magnetic fields

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  • Lecture (Conference)
    EDiSON'19 19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures, 29.06.-02.07.2015, Salamanca, España

Permalink: https://www.hzdr.de/publications/Publ-22219


THz free-electron laser investigation of GaAsN in pulsed magnetic fields up to 60 T

Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Helm, M.

Abstract

We use the unique combination of the free-electron laser FELBE and the High Magnetic Field Laboratory Dresden to perform cyclotron resonance (CR) spectroscopy on the dilute nitride alloy GaAsN. FELBE is a tunable (4 – 250 µm) laser source of high brilliance, which can be used in pulsed magnetic fields up to 60 T. Our CR studies enable us to measure fundamental electronic properties of GaAsN, a very interesting candidate for optoelectronic applications because of the tunability of its band gap energy in the range of 1.4 eV – 0.9 eV by the incorporation of a small concentration of N-atoms (~ 1%). Figure 1 illustrates a typical CR spectrum and our values of the CR electron mass at 100 K and 6.5 THz. We observe a slight increase of the electron CR mass with nitrogen content. This dependence is in very good agreement with that described by the band anticrossing (BAC) model [1] and the empirical tight binding (TB) calculations [2], which are represented in Figure 1 by dashed and dotted black lines, respectively. The comparison with magneto-photoluminescence (PL) investigations performed by Alberi et al. [3] and Masia et al. [4] reveal instead a steep increase of the electron effective mass with nitrogen content, which is consistent with a modified k·p calculation by Lindsay and O’Reilly [5]. This model assumes that nitrogen can form pairs and clusters, not considered in [1,2]. Since PL is very sensitive to carrier localization effects, the results in [3,4] can be well described by [5]. In contrast, CR spectroscopy is only sensitive to delocalized states, which explains the good agreement of the present results with [1,2].

[1] J. Wu et al. Phys. Rev. B 64, 085320 (2000).
[2] N. Shtinkov et al. Phys. Rev. B 67, 081202(R) (2003).
[3] Alberi et al. Phys. Rev. Lett. 110, 156405 (2013).
[4] Masia et al. Phys. Rev. B 73, 073201, (2006).
[5] A. Lindsay and E. P. O’Reilly Phys. Rev. Lett. 93, 196402 (2004).

Keywords: GaAsN; effective mass; cyclotron resonance spectroscopy; THz spectroscopy in pulsed magnetic fields

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  • Poster
    German THz Conference 2015, 08.-10.06.2015, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22218


Triadic resonances in nonlinear simulations of a fluid flow in a precessing cylinder

Giesecke, A.; Albrecht, T.; Gundrum, T.; Herault, J.; Stefani, F.

Abstract

We present results from three-dimensional non-linear hydrodynamic simulations of a precession driven flow in cylindrical geometry. The simulations are motivated by a dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in which the possibility of generating a magnetohydrodynamic dynamo will be investigated in a cylinder filled with liquid sodium and simultaneously rotating around two axes.
In this study, we focus on the emergence of non-axisymmetric time-dependent flow structures in terms of inertial waves which – in cylindrical geometry – form so-called Kelvin modes. For a precession ratio Γ = Ωp /Ωc = 0.014 considered by us, the amplitude of the forced Kelvin mode reaches up to one fourth of the rotation velocity of the cylindrical container confirming that precession provides a rather efficient flow driving mechanism even at moderate values for Γ.
More relevant for dynamo action might be free Kelvin modes with higher azimuthal wave number. These free Kelvin modes are triggered by non-linear interactions and may constitute a triadic resonance with the fundamental forced mode when the height of the container matches their axial wave lengths. Our simulations reveal triadic resonances at aspect ratios close to those predicted by the linear theory except around the primary resonance of the forced mode. In that regime we still identify various free Kelvin modes, however, all of them exhibit a retrograde drift around the symmetry axis of the cylinder and none of them can be assigned to a triadic resonance.
The amplitudes of the free Kelvin modes always remain below the forced mode but may reach up to 6% of the of the container’s angular velocity. The properties of the free Kelvin modes, namely their amplitude and their frequency, will be used in future simulations of the magnetic induction equation to investigate their ability to provide for dynamo action.

Keywords: Precession; DRESDYN; Dynamo

Permalink: https://www.hzdr.de/publications/Publ-22217


Design of compensated ferrimagnetic Heusler alloys for giant tunable exchange bias

Nayak, A. K.; Nicklas, M.; Chadov, S.; Khuntia, P.; Shekhar, C.; Kalache, A.; Baenitz, M.; Skourski, Y.; Guduru, V. K.; Puri, A.; Zeitler, U.; Coey, J. M. D.; Felser, C.

Abstract

Rational material design can accelerate the discovery of materials with improved functionalities. This approach can be implemented in Heusler compounds with tunable magnetic sublattices to demonstrate unprecedented magnetic properties. Here, we have designed a family of Heusler alloys with a compensated ferrimagnetic state. In the vicinity of the compensation composition in Mn–Pt–Ga, a giant exchange bias (EB) of more than 3 T and a large coercivity are established.
The large exchange anisotropy originates from the Exchange interaction between the compensated host and ferrimagnetic clusters that arise from intrinsic anti-site disorder. Our design approach is also demonstrated on a second material with a magnetic transition above room temperature, Mn–Fe–Ga, exemplifying the universality of the concept and the feasibility of room-temperature applications. These findings may lead to the development of magneto-electronic devices and rareearth-free exchange-biased hard magnets, where the second quadrant magnetization can be stabilized by the exchange bias.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22216


Preferential adsorption of Cu in a multi-metal mixture onto biogenic elemental selenium nanoparticles

Jain, R.; Dominica, D.; Jordan, N.; Rene, E. R.; Weiss, S.; van Hullebusch, E. D.; Hübner, R.; Lens, P. N. L.

Abstract

Preferential adsorption of Cu contained in wastewaters is desirable as the Cu can then be reprocessed and reused more easily. In this study, biogenic elemental selenium nanoparticles (BioSeNPs) were assessed for their ability to preferentially adsorb Cu from an equimolar mixture containing Cu, Cd and Zn. Both metal to BioSeNPs ratio and initial metal solution pH have been shown to affect the preferential adsorption capacity of BioSeNPs towards Cu. BioSeNPs adsorbed 2.3 times more Cu from an equimolar mixture of Cu, Zn and Cd at an initial metal solution pH of 5.2 and metal to BioSeNPs ratio of 0.21 mg mg−1, while adsorbing more than 78% of added Cu. Infrared spectroscopy revealed that the Cu, Cd and Zn were interacting with hydroxyl and carboxyl surface functional groups of the BioSeNPs. The modeling of BioSeNPs' acid-base titration revealed the presence of high concentrations of carboxylic groups (C = 60.26 mol Kg−1) with a pKa of 3.9 providing, further evidence of their interaction with Cu. The adsorption of Cu resulted in a lower colloidal stability of the BioSeNPs as indicated by less negative ζ-potential values. BioSeNPs showed good preferential adsorption capacity towards Cu when compared to oxidized carbon nanotubes. This study provides proof-of-concept for preferential adsorption of Cu onto BioSeNPs which are present in the effluent of a bioreactor treating selenium oxyanions containing wastewater.

Keywords: preferential adsorption; biogenic; selenium nanoparticles; heavy metals; FT-IR

Permalink: https://www.hzdr.de/publications/Publ-22215


Ga, Ge, In and other trace elements in sphalerite from different geological deposit types, with reference to mineralisation events at Freiberg.

Frenzel, M.

Abstract

Sphalerite (ZnS) is an important source of a number of high-tech metals. However, while a large amount of analytical data on trace and minor element concentrations in sphalerite has been collected over the last decades, our understanding of the geological controls on their enrichment or depletion remains limited. No comprehensive meta-analysis of this data has ever been conducted. This talk presents the results of such a meta-analysis, based on an extensive collection of data from the scientific literature. Nine elements (Ag, Cd, Co, Cu, Fe, Ga, Ge, In and Mn) were considered. For five of these elements (Fe, Ga, Ge, In, Mn) significant differences were found between different geological types of deposits. The regularity of these differences suggests the operation of a single underlying control parameter – possibly formation temperature – with obvious implications for the identification of future sources of these elements.

  • Lecture (others)
    BHMZ Seminar, 06.05.2015, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22214


The role of geoscientists in securing the future supply of high technology minerals and metals

Gutzmer, J.; Birtel, S.; Frenzel, M.

Abstract

The availability of minerals and metals required for high technology applications has in recent years been widely recognized as being of strategic importance for future development - especially for highly industrialized economies. Because the absolute tonnage of such high technology minerals and metals in industrial products is typically small, inventories in the technosphere will remain limited and widely disseminated. This will significantly hamper recycling efforts. As a direct consequence, primary resources will need to be utilized to secure supply into the foreseeable future. Tapping primary resources appears as a reasonable approach, as these are readily available for most high technology metals. Geoscientists will have to make an important contribution – not only towards exploration and discovery, but also to the implementation of technological concepts for comprehensive resource utilization, i.e., mining operations that are not only economic, but also resource-efficient and environmentally benign.

Keywords: High technology metals; criticality; exploration; mineral systems analysis; geometallurgy

  • Lecture (Conference)
    12th Biennial SGA Conference, 12.-15.08.2013, Uppsala, Sverige

Permalink: https://www.hzdr.de/publications/Publ-22213


A general method for the assessment of the geological and technological limitations to high-tech metal supply

Frenzel, M.; Tolosana-Delgado, R.; Gutzmer, J.

Abstract

The demand for some of the rarer elements in the Earth's crust for high-tech applications is increasing rapidly. Many of these elements are produced exclusively as by-products resulting in potentially significant supply limitations. However, despite their increasing importance, reliable assessments of these limitations are not readily available. Gallium, germanium, indium, tellurium and rhenium are good examples of such elements.
In this work, a general methodology is presented for the estimation of the supply potential of by-product elements as a function of their distribution in the relevant raw materials, the state of technology and market prices. Geochemical data from the scientific literature is used to generate numerical models of the distribution of the elements over separable production volumes, while data on the partitioning behaviour of the elements during the production of the main products is used to assess the fraction which is profitably extractable as a function of cut-off grade in a waste or intermediate process stream. The exact value of this cut-off grade may be taken to reflect both the current state of extraction technology as well as market prices for the element in question. A combination of the distribution and process behaviour models in Monte Carlo-type numerical simulations yields a median estimate and confidence interval for the supply potential as a function of the cut-off grade.
The results can be presented in the form of availability curves. This allows not only for the assessment of the current situation but also enables simple adaptation to changed technological and market conditions. Furthermore it makes it possible to assess the chief supply limitations, i.e. whether they are geological or technological, as well as the magnitude of inefficiencies in the markets of these metals. A simple example is used to illustrate the application of the method.

  • Lecture (Conference)
    The 17th annual conference of the International Association for Mathematical Geosciences, 05.-12.09.2015, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22212


Mineralogical deportment of indium in the Neves-Corvo deposit - Implications for recovery and extraction

Frenzel, M.; Bachmann, K.; Krause, J.; Carvalho, J. R. S.; Relvals, J. M. R. S.; Pacheco, N.; Gutzmer, J.

Abstract

Neves-Corvo is a world-class volcanic-hosted massive sulphide (VHMS) deposit located in the Iberian Pyrite Belt (IPB). It is both one of the largest and richest deposits in the IPB. Besides its size, other notable features include its high tin content and the unusual ore types within which most of this tin was originally hosted. High indium concentrations (30 - 50 ppm in whole ore) also make it an attractive source of this rare metal. However, the mine does not currently profit from this potential.

It was the aim of this study to generate the data required for a detailed quantitative evaluation of different valorisation options for indium at Neves-Corvo. In addition to data on the spatial distribution of the element, this also requires a detailed understanding of its mineralogical deportment. While previous studies had reported elevated indium concentrations in a number of different minerals (e.g. stannite, sphalerite, cassiterite, tetrahedrite-tennantite, chalcopyrite) as well as the occurrence of two discrete indium minerals (roquesite, CuInS2, and sakuraiite, (Cu, Zn, Fe)3(In,Sn)S4), modal mineralogy and consequently the deportment of indium in the studied samples were never quantified.

In the present work, a combination of whole ore geochemistry, automated scanning electron microscope (SEM)-based image analysis and electron probe microanalysis (EPMA) was used to study the mineralogical deportment of indium in a representative set of more than 70 ore and process samples. It was found that, depending on ore type, sphalerite and/or chalcopyrite are the most important host minerals while stannite, roquesite and sakuraiite are not important due to their generally low abundance. Indium concentrations in sphalerite are highly variable, but are usually 2 - 3 times higher than in coexisting chalcopyrite. The exact concentrations depend on the total concentration of indium in the ore in relation to the abundance of these two minerals. This apparent equilibrium partitioning behaviour is thought to be mostly a consequence of the extensive syntectonic recrystallisation of the ore minerals.

The clear dominance of sphalerite and chalcopyrite as indium carriers has obvious consequences for valorisation options at the mine. First, the indium contained in the ores should be recoverable from the ores with the zinc and copper concentrates. Second, the production of separate concentrates enriched to the minimum concentrations required by smelters will only be possible by the separate processing of indium-rich ores.

To the best knowledge of the authors, this is the first detailed deportment study for indium ever conducted. The results have obvious implications not only for indium valorisation at Neves-Corvo, but also in other massive sulphide deposits affected by extensive tectonically induced recrystallisation. They should therefore be of interest to the wider geometallurgical and economic geology communities.

This is a contribution to the ZHINC project (PTDC/CTE-GIX/114208/2009). Thanks are due to the authors' host institutions for the provision of the funding and infrastructure necessary to conduct this work.

  • Poster
    SEG 2015 - World-Class Ore Deposits: Discovery to Recovery, 27.-30.09.2015, Hobart, Australia

Permalink: https://www.hzdr.de/publications/Publ-22211


Concentration of Ga, Ge, In and Fe in sphalerite as a function of deposit type – A meta-analysis

Frenzel, M.; Hirsch, T.; Gutzmer, J.

Abstract

The statistical analysis of a comprehensive collection of analytical data compiled from the scientific literature shows that significant differences exist in the mean concentrations of Ga, Ge, In and Fe in sphalerite samples from different types of Pb-Zn deposits. A systematic trend is present in these mean concentrations: going from Mississippi Valley-type via vein-type to high-temperature hydrothermal replacement deposits, mean Ga and Ge concentrations decrease, while Fe and In concentrations increase. The same trend is observed going from Mississippi Valley-type via sediment-hosted massive sulphide to volcanic-hosted massive sulphide deposits. The two trends are virtually indistinguishable and seem to reflect a general increase in the magmatic contribution to the ore-forming process. While the exact geological controls remain unclear, this trend constitutes an important observation with immediate implications for the exploration for new resources of Ga, Ge and In.

Keywords: Sphalerite; mineral chemistry; trace elements; high-tech metals

  • Poster
    13th Biennial SGA Conference, 24.-27.08.2015, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-22210


On the current and future availability of gallium

Frenzel, M.; Ketris, M. P.; Seifert, T.; Gutzmer, J.

Abstract

By-product availability curves were constructed for the production of gallium (Ga) from bauxite, sulphidic zinc ores and coal. They were used to assess both the current nature of its supply regime, as well as its potential future development. Not only was the current situation found to be firmly in the elastic supply regime for all three raw materials, indicating that significant future increases in primary Ga production are possible without increases in the production of the corresponding main products, but it was also found that estimated current supply potential from bauxite and sulphidic zinc ores alone is at least five times larger than actual primary production. Coal offers a significant additional supply potential (currently at least ~ 1.5 times primary Ga production). An extrapolation of growth trends in the primary production of Al, Zn and Ga into the future indicates that the minimum supply potential of Ga will not be exhausted before 2050. Once this point is reached, additional increases in Ga production relative to the production of Al and Zn will be possible via decreases in the relevant cut-off grades for its extraction. No significant shortages are therefore expected in the foreseeable future. Our results clearly refute the widely-held notion that the supply of certain by-product metals is currently limited by the production of the corresponding main products. Rather, the chief limitation appears to be installed production capacity.

Keywords: High-tech metals; by-products; long-term supply; reserves; resources

Permalink: https://www.hzdr.de/publications/Publ-22209


Gallium, germanium, indium, and other trace and minor elements in sphalerite as a function of deposit type - A meta-analysis

Frenzel, M.; Hirsch, T.; Gutzmer, J.

Abstract

While a significant amount of analytical data on trace and minor element concentrations in sphalerite has been collected over the last six decades, no meta-analysis of this data has ever been conducted. In this study, the results of such an analysis are presented. While the study focusses on Ga, Ge and In, data for six other elements (Ag, Cd, Co, Cu, Fe and Mn) was also included.
The results show that there are systematic, statistically significant differences in the mean concentrations of Fe, Ga, Ge, In and Mn in sphalerite from different deposit types, while Cd and Cu concentrations show no such differences, and Ag and Co concentrations are only significantly different for vein-type deposits. A principal component analysis demonstrates that the differences between deposit types are approximately one-dimensional, being expressible in terms of a single number. This number correlates strongly with the homogenisation temperature of fluid inclusions (R2 = 0.82, p < 2∙10-16). It may be expressed as follows:

PC 1*=ln((C_Ga^0.22⋅C_Ge^0.22)/(C_Fe^0.37⋅C_Mn^0.20⋅C_In^0.11 ))

with Ga, Ge, In and Mn concentrations in ppm, and Fe concentration in wt.%. The relationship is sufficiently strong to be used as a geothermometer (GGIMFis). The empirical relationship between PC 1* and the homogenisation temperature, T, is:

T(°C)=(54.4±7.3)⋅PC 1*+(208±10)

Our results indicate a strong control of sphalerite chemistry by fluid temperature, particularly for the concentrations of Ga (R2 ~ 0.40), Ge (R2 ~ 0.65), Fe (R2 ~ 0.30) and Mn (R2 ~ 0.60), and to a lesser degree In (R2 ~ 0.10). The concentrations of Ag, Cd, Co and Cu appear to be independent of temperature.
As a consequence of the strong temperature control on PC 1*, metamorphic overprinting of Pb-Zn deposits, even by lower greenschist facies events, may lead to significant changes in sphalerite composition, namely a relative decrease in Ga and Ge concentrations, and increase in Fe, Mn and, to a lesser degree, In concentrations. The closure temperature of sphalerite in regional metamorphic events appears to be around 310 ± 50°C, such that higher-grade events will not be reflected in its composition.
Factors other than temperature, such as differences in fluid salinity or source-rock composition, do not appear to be responsible for differences between deposit types, but rather appear to cause differences between individual deposits. Particularly, the Cu activity in ore-forming systems appears to have a strong influence on In concentrations in sphalerite.
The observed trends in sphalerite compositions provide a useful tool for future studies of different types of Pb-Zn deposits, as well as for mineral exploration. They should be particularly relevant for the identification of new resources of Ga, Ge and In.

Keywords: High-tech metals; By-products; Fluid salinity; Sphalerite geothermometer; Fluid inclusions; Homogenisation temperature; GGIMFis thermometer

Permalink: https://www.hzdr.de/publications/Publ-22208


Assessing the supply potential of high-tech metals - A general method

Frenzel, M.; Tolosana-Delgado, R.; Gutzmer, J.

Abstract

The demand for some of the rarer elements in the Earth's crust, mostly from high-tech applications, is increasing rapidly. Many of these elements are produced exclusively as by-products resulting in potentially significant supply limitations. In this article, a general method for the assessment of the supply potential of such elements is developed from a conceptual model of the supply-chain. Namely, statistical and deterministic models are introduced to quantify both the variability in by-product concentrations in the relevant raw materials, as well as the effects of this variability on achievable recoveries. The assessment of uncertainties is implemented via Monte-Carlo-type simulations. Presentation of the results in availability curves ensures adaptability to future changes in market conditions, while extensive documentation of the assessment method, available as electronic supplementary material with this article, ensures reproducibility.
A simple example is used to illustrate the complete estimation process. It shows that in addition to ensuring future adaptability of the results, availability curves are also useful for the assessment of the current supply regime of a given by-product. An elastic and inelastic regime might be distinguished – in the elastic regime, significant demand-driven increases in by-product supply are possible without increases in the production of the main product, while in the inelastic regime this is not the case. The method presented in this article is the first to enable such an assessment to be made in a reliable and transparent manner.

Keywords: Electronic metals; Availability; By-products; Germanium; Reserves; Resources

Permalink: https://www.hzdr.de/publications/Publ-22207


Lattice location of deep level impurities in hyperdoped Si by ion implantation and short-time annealing

Liu, F.; Prucnal, S.; Gao, K.; Heller, R.; Skorupa, W.; Helm, M.; Zhou, S.

Abstract

Impurities play an important role in determining the electrical, optical and structural properties of semiconductors. It has been proposed that deep level impurities, such as Titanium (Ti) or chalcogens in Si, can induce an impurity band inside the bandgap at high enough doping concentration. The insertion of an impurity band can enhance the absorption at a broader wavelength range and leads to applications in the so-called intermediate band solar cell. However, deep level impurities have relatively low solid solubility limit in Si. We prepared deep level impurities doped silicon to above the Mott insulator concentration by ion implantation followed by sub-second annealing. The degree of crystalline lattice recovery in implanted layers and the lattice location of impurities in Si were analyzed by Rutherford backscattering spectrometry/Channeling. Our results show that S and Se atoms are occupying substitutional lattice sites in Si [1], while Ti impurities have no ordered lattice occupation [2].

[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, W. Skorupa and M. Helm, Scientific Report 5, 8329 (2015).
[2] F. Liu, et al., in preparation (2015).

Keywords: Ion implantation; deep level impurities

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  • Poster
    Jaszowiec 2015, 20.-25.06.2015, Wisła, Poland

Permalink: https://www.hzdr.de/publications/Publ-22206


Lattice location of deep level impurities in hyperdoped Si by ion implantation and short-time annealing

Liu, F.; Prucnal, S.; Gao, K.; Heller, R.; Skorupa, W.; Helm, M.; Zhou, S.

Abstract

Impurities play an important role in determining the electrical, optical and structural properties of semiconductors. It has been proposed that deep level impurities, such as Titanium (Ti) or chalcogens in Si, can induce an impurity band inside the bandgap at high enough doping concentration. The insertion of an impurity band can enhance the absorption at a broader wavelength range and leads to applications in the so-called intermediate band solar cell. However, deep level impurities have relatively low solid solubility limit in Si. We prepared deep level impurities doped silicon to above the Mott insulator concentration by ion implantation followed by sub-second annealing. The degree of crystalline lattice recovery in implanted layers and the lattice location of impurities in Si were analyzed by Rutherford backscattering spectrometry/Channeling. Our results show that S and Se atoms are occupying substitutional lattice sites in Si [1], while Ti impurities have no ordered lattice occupation [2].

[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, W. Skorupa and M. Helm, Scientific Report 5, 8329 (2015).
[2] F. Liu, et al., in preparation (2015).

Keywords: Ion implantation; deep level impurities

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  • Poster
    IBA 2015 - 22nd International Conference on Ion Beam Analysis, 14.-19.06.2015, Opatija, Croatia

Permalink: https://www.hzdr.de/publications/Publ-22205


Use of a Cyclone 18/9 for Radiolabelling of Nanoparticles

Franke, K.; Hildebrand, H.; Schymura, S.

Abstract

Nanosafety research requires versatile tools for detection of nanoparticles in living and non-living media within a wide range of concentration. This is a great challenge due to the very low environmentally relevant concentration of (engineered) nanoparticles expected and the presence of background concentrations of the respective elements. Radiolabelling of nanoparticles offers an excellent alternative to enable nanoparticle detection in these complex media down to trace amounts. Even online in situ tracing and visualisation techniques are accessible.

In this work we present different techniques for the radiolabelling of nanoparticles (Ag0, TiO2, CeO2, MWCNT) including activation of NP, radiosynthesis of NP, radiolabelling of NP, self-diffusion of radioisotopes into NP and recoil labelling. A cyclotron Cyclone 18/9 was used for the radiolabelling of the nanoparticles via proton activation (Ti-48(p,n)V-48, Ce-140(p,2n)Pr-139  Ce-139), Be-7 - recoil labelling (Li 7(p,n)Be-7) and the radioisotope production. Different targets were developed and different labelling strategies were tested. As a result, labelling yields and labelling stabilities were determined and the influence of the labelling procedure on the particle properties was evaluated.

These radiolabelled nanoparticles are successfully used in comprehensive environmental studies. Our recent studies with application of the radiolabelled nanoparticles focus on nanoparticle uptake in plants, distribution and mobility of nanoparticles in sewage sludge, and fate of nanoparticles in wastewater treatment processes.

  • Lecture (Conference)
    International Conference on Nuclear Analytical Methods in the Life Science (NAMLS11), 23.-28.08.2015, Delft, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-22204


High temperature stable transparent conductive oxides for solar thermal applications

Lungwitz, F.; Schumann, E.; Guillen, E.; Escobar, R.; Krause, M.; Gemming, S.

Abstract

In solar thermal energy conversion systems, receivers containing the heat transfer fluid are coated by a solar selective coating which must exhibit high absorption in the solar region and low thermal emittance. Additionally, the coating materials have to be structurally, optically, and mechanically stable at high temperatures. Nowadays, temperatures of up to 450 °C and up to 550°C are reached using parabolic trough arrays and solar tower absorbers, respectively, whereas temperatures up to 800 °C could be reached if the receiver materials were stable enough. Solar selective coatings can be formed by a transparent conductive oxide (TCOs) film deposited on a black body absorber to have both, high absorption in the ultraviolet, visible and near infrared spectral range (300 nm – 2500 nm) as well as high reflectivity in the infrared (> 2500 nm). The former is to absorb as much sunlight as possible, the latter for preventing thermal radiation losses from the system to the environment. In this work Ta:TiO2 and Ta:SnO2 TCOs thin films are reactively magnetron sputtered from tantalum doped metallic targets. The oxygen flow during deposition is precisely controlled by a plasma emission unit which is crucial to obtain optimal electrical and therefore also optical properties by maintaining high sputtering rates. While the as-deposited films are amorphous and non-conductive, they are crystallized and therefore electrically activated upon a subsequent thermal treatment at 425 °C for 1 hour. The correlation between structural, optical, and electrical properties is shown by Rutherford Backscattering Spectroscopy (RBS), X-ray Diffraction (XRD), Raman Spectroscopy, Spectroscopic Ellipsometry (SE) (both at room- and high- temperatures), UV-VIS spectrometry, and Hall Effect measurements. Preliminary tests show that optical constants of Ta:TiO2 films are maintained after annealing at 700ºC.

Keywords: TCO; transparent conductive oxide; solar thermal; magnetron sputtering; TiO2; Cluster Tool; solar selectivity; high temperature

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  • Lecture (Conference)
    ICMAT 2015 & IUMRS - ICA 2015, 28.06.-03.07.2015, Singapore, Singapore

Permalink: https://www.hzdr.de/publications/Publ-22203


Optical and electrical characterization of TiO2- based transparent conductive oxides

Lungwitz, F.; Schumann, E.; Wenisch, R.; Neubert, M.; Guillen, E.; Escobar, R.; Krause, M.; Gemming, S.

Abstract

Transparent conductive oxides (TCOs) are already widely used in the optoelectronic industry e.g. as electrodes for liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), or thin film solar cells. Less attention has been devoted to their optical properties and thermal stability until now.
In this work, Tantalum doped TiO2 and SnO2 TCO films are investigated with respect to their structural, optical, and electrical properties at temperatures from RT to 700°C. The films are prepared at room temperature by direct current reactive magnetron sputtering from metallic as well as ceramic targets and subsequently isothermally annealed at temperatures of 425°C. For compositional and structural analysis x-ray diffraction (XRD), Raman spectroscopy, and Rutherford backscattering spectroscopy (RBS) are used. The optical properties are determined by spectroscopic ellipsometry, spectral photometry, and subsequent modelling. Hall effect measurements are used to determine the electrical properties of the TCO films.
The as-deposited layers are amorphous and isolating. By thermal annealing they are activated and become conductive.

Keywords: TCO; transparent conductive oxide; solar-thermal; thin film; high temperature; magnetron sputtering; energy materials; Cluster Tool

Involved research facilities

Related publications

  • Poster
    Frühjahrstagung der DPG, 19.03.2015, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22202


Contactless magnetic excitation of acoustic cavitation in liquid metals

Grants, I.; Gerbeth, G.; Bojarevics, A.

Abstract

A steady axial magnetic field is applied to a liquid metal zone heated by induction currents. The resulting alternating Lorentz force causes pressure oscillations that being strong enough lead to cavitation in the molten metal. Amplitude of the pressure oscillations is proportional to the product of the induced currents and the steady axial magnetic field induction. We follow an approach where the acoustic pressure is maximized by the induction currents. The onset of cavitation is identified by the occurrence of sub-harmonics of the drive frequency in sound recorded at the surface of the experimental cell. It is demonstrated that cavitation in a liquid metal may be excited by a superimposed axial magnetic field of a moderate 0.5 T induction.

Keywords: ALUMINUM-ALLOYS; SOLIDIFICATION; ULTRASOUND; DYNAMICS

Permalink: https://www.hzdr.de/publications/Publ-22199


Macro segregation formation mechanism of the primary silicon phase in directionally solidified Al-Si hypereutectic alloys under the impact of electric currents

Zhang, Y.; Miao, X.; Shen, Z.; Han, Q.; Song, C.; Zhai, Q.

Abstract

Understanding the macro segregation formed by applying electric currents is of high commercial importance. This paper investigates how electric currents control the solute distribution in the directionally solidified Al-20.5wt%Si hypereutectic alloy. Experimental results show that a severe macro segregation of the primary silicon phase occurs at the initial solidification stage of the samples. This is accompanied by two interface transitions in the mushy zone: quasi planar → upwards V-shaped → quasi planar. The corresponding numerical simulations present a vortex ring flow pattern as a consequence of the electric current distortion in the mushy zone. The peculiar macro segregation phenomenon can be fully explained by considering the effect of the forced flow on the solute distribution. At the initial growth of the samples, the forced flow generates a rigorous solute exchange between the mushy zone and the bulk melt and encourages the primary silicon to continuously precipitate and segregate. As the solute content in the bulk melt gradually approaches the eutectic point, the precipitation of primary silicon is profoundly reduced. Eventually, a significant segregation of the primary silicon phase is observed in the initial directional growth. The present study not only presents a new approach to control the solute distribution by applying an electric current through a generated forced flow, it also facilitates the understanding of the underlying grain refinement mechanism and the growth of crystals in the solute that are controlled by the electric currents.

Keywords: Al-Si alloys; directional solidification; external electric field; macro segregation; melt convection

Permalink: https://www.hzdr.de/publications/Publ-22197


Quantitative cross-sectional measurement of solid concentration distribution in slurries using wire-mesh sensor

Dos Santos, E. N.; Schleicher, E.; Reinecke, S.; Hampel, U.; Da Silva, M. J.

Abstract

Wire'mesh sensors have so far been widely applied in gas'liquid flows where resistance or capacitance distributions are measured and converted into gas or liquid holdup distributions. In this work we report on the qualification of the wire'mesh imaging technique for the measurement of cross'sectional solid concentrations in solid–liquid mixtures. As the dielectric constants of solid particles are different from those of gas, water or oil in the flow, measuring this property can be used as an indication of solids distribution. Experiments were performed in a stirred tank of 100 mm diameter equipped with a capacitance wire'mesh sensor. The wire'mesh sensor was operated 4000 frames per second acquisition speed and has a spatial resolution of 6.25 mm. As solids we used silica sand particles (diameter ~ 105 μm) which were stirred with water in a volume concentration range of 1% to 35% to form slurries. By varying the stirring speed, different solid concentration distributions were produced and investigated. In order to convert the measured relative permittivity distribution into a solid concentration distribution, an empirical approach was employed.

Keywords: wire-mesh sensor, slurry flow; solid fraction measurement, flow visualization

Involved research facilities

  • TOPFLOW Facility

Permalink: https://www.hzdr.de/publications/Publ-22196


Regenerative amplification in Yb3+-doped fused silica

Röser, F.; Loeser, M.; Siebold, M.; Albach, D.; Grimm, S.; Langner, A.; Schötz, G.; Schramm, U.

Abstract

We report to our knowledge the first short pulse generation experiment
in bulk volume Yb-doped fused silica utilizing a Q-switched cavity.

  • Contribution to proceedings
    CLEO/Europe-EQEC Conference 2015, 21.-25.06.2015, München, Deutschland
  • Poster
    CLEO/Europe-EQEC Conference 2015, 21.-25.06.2015, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22195


Code intercomparison and benchmark for muon fluence and absorbed dose induced by an 18-GeV electron beam after massive iron shielding

Fasso, A.; Ferrari, A.; Ferrari, A.; Mokhov, N. V.; Mueller, S. E.; Nelson, W. R.; Roesler, S.; Sanami, T.; Striganov, S. I.; Versaci, R.

Abstract

In 1974, Nelson, Kase, and Svenson published an experimental investigation on muon shielding using the SLAC high energy LINAC. They measured muon fluence and absorbed dose induced by a 18 GeV electron beam hitting a copper/water beam dump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical mode ls available at the time. In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes MARS15, FLUKA2011 and GEANT4 to model the experimental setup and run simulations. The results will then be compared between the codes, and with the SLAC data.

  • Open Access Logo Contribution to proceedings
    Shielding Aspects of Accelerators, Target and Irradiation Facilities – SATIF 12, 28.-30.04.2014, Batavia (Illinois), USA
    Workshop Proceedings, Online: OECD Nuclear Energy Agency, 240-247

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Permalink: https://www.hzdr.de/publications/Publ-22194


Fermi surface of SrCo2P2: A strongly enhanced Pauli paramagnet

Götze, K.; Klotz, J.; Bergmann, C.; Geibel, C.; Kraft, I.; Lorenz, V.; Rosner, H.; Sheikin, I.; Mccollam, A.; Bruin, J.; Wosnitza, J.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • Poster
    RHMF 2015, 11th International Conference on Research in High Magnetic Fields, 02.-04.07.2015, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-22193


NMR of the Shastry-Sutherland lattice SrCu2(BO3)2

Stern, R.; Kohlrautz, J.; Haase, J.; Kühne, H.; Green, E.; Zhang, Z.; Wosnitza, J.

Abstract

SrCu2(BO3)2 is a prominent realization of the Shastry-Sutherland lattice model [1]. In this quasi-two-dimensional compound, Cu2+ ions form orthogonal spin-singlet dimers with strong geometrical frustration of the next-nearest and nearest neighbor exchange interactions. SrCu2(BO3)2 has been studied extensively using a variety of techniques, such as nuclear magnetic resonance (NMR) spectroscopy, or recent magnetization measurements up to 118 T. These experiments reveal a complex sequence of magnetization plateaus with differing commensurate magnetic superstructure, stemming from a stripe type order of triplet states [2-4]. Due to its highly sensitive local probe character, NMR can provide deep insight into the spin-coupling mechanisms and excitations at highest magnetic fields. We present 11B NMR spectra measured in pulsed magnetic fields up to 56 T, and compare those with prior results obtained in highest static magnetic fields. Herewith, we prove the feasibility and efficacy of this new technique, yielding the capability for extended studies at highest magnetic fields up to the 100 T regime that determine the spin structure in the 1/3 magnetization plateau and beyond.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • Poster
    RHMF 2015 - 11th International Conference on Research in High Magnetic Fields, 02.-04.07.2015, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-22192


Solid-state NMR in pulsed magnetic fields

Kühne, H.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • Invited lecture (Conferences)
    EMFL 2015 User Meeting, 01.07.2015, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-22191


III-V:Mn Ferromagnetic semiconductors prepared by ion implantation

Yuan, Y.; Sawicki, M.; Helm, M.; Zhou, S.

Abstract

Ferromagnetic semiconductors (FSs) have been under intensive investigation during the last decade. Until now, the prototype ferromagnetic semiconductor GaMnAs has revealed a variety of unique features induced by the combination of its magnetic and semiconducting properties. As a non-equilibrium process, ion implantation can overcome the difficulty that the Mn concentration in ferromagnetic III-V (FS) is far beyond the solid solubility of Mn in III-V compounds. However, the activation of dopants remains challenging due to the clustering of implanted ions during post-annealing. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. On the other hand, one notes that the solubility limit in the liquid phase is generally much larger than that in the solid phase. Short-time annealing within nanoseconds regime allows the epitaxial growth from a liquid phase. The approach combining ion implantation and pulsed laser melting allows us to prepare ferromagnetic semiconductors covering the full spectrum of III-V compound semiconductors.
We have successfully synthesized ferromagnetic Mn doped III-V from InAs and GaAs to InP and GaP with different bandgaps. The results of magnetization, magnetic anisotropy, resistivity, anomalous Hall effect, magnetoresistance and x-ray magnetic circular dichroism obtained from the synthesized samples confirm the intrinsic origin and the carrier-mediated nature of the ferromagnetism. Moreover, in different III-V hosts we observe distinct differences regarding the magnetic anisotropy and conduction mechanism which are related with the intrinsic parameters such as the lattice mismatch, energy gap and the acceptor level of Mn. These results could allow a panorama-like understanding of III-V:Mn based ferromagnetic semiconductors.

Involved research facilities

Related publications

  • Poster
    Jaszowiec 2015, 20.06.2015, Wisla, Poland

Permalink: https://www.hzdr.de/publications/Publ-22190


Hydrodynamic and mass transfer properties of a bubble column with vertically inserted tube bundles

Šimić, N.; Breiler, K.; Schubert, M.

Abstract

The objective of this study is to examine the influence of different vertical tube bundle designs on the bubble dynamics and on the mass transfer rates in a bubble column. The studies in the open literature examining the performance of bubble columns with vertically inserted tube bundles have focused primarily on the coverage of the cross-sectional area of the bubble column by the tube bundle (CSA). The most frequently used coverages are the 5% and the 25% (± 3%) which mimic the heat exchangers utilized in the processes of methanol and Fischer-Tropsch syntheses. Other than that, the designs of tube bundles seem to be arbitrarily chosen and feature a number of different configurations of layouts, tube diameters and tube lengths. From the current state of research, it is thus rather difficult to draw conclusions on the optimal design of a heat exchanger suitable for use in bubble columns (Youssef et al., 2013). Intuitively, it can be concluded that the most important design features of tube bundles affecting the flow are the distance between the tubes and the unit cell area enclosed by the tubes in their respective arrangements. Accordingly, the study aims on a systematic analysis on the effect of these geometric parameters.

Keywords: bubble column; internals; heat exchanger; tube bundle; hydrodynamics; gas holdup; bubble size distribution; mass transfer; X-ray tomography

Involved research facilities

  • TOPFLOW Facility
  • Poster
    12th International Conference on Gas-Liquid & Gas-Liquid-Solid Reactor Engineering (GLS12), 28.06.-01.07.2015, New York City, USA

Permalink: https://www.hzdr.de/publications/Publ-22189


Macroscopic and spectroscopic characterization of uranium(VI) sorption onto orthoclase and muscovite and the influence of competing Ca2+

Richter, C.; Müller, K.; Drobot, B.; Steudtner, R.; Großmann, K.; Stockmann, M.; Brendler, V.

Abstract

The uranium(VI) sorption onto orthoclase and muscovite, representing feldspars and micas as important components of the earth crust, was investigated in the presence and absence of Ca2+ under aerobic conditions. Batch experiments were accompanied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) as well as in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy. The results indicate that the U(VI) sorption is reduced by Ca2+ at pH ≥ 8 up to 30% due to the formation of the neutral aqueous Ca2UO2(CO3)3 complex. TRLFS measurements on the supernatant confirmed the predominance of this Ca2UO2(CO3)3 complex in accordance with thermodynamic calculations. Furthermore, TRLFS measurements on the mineral suspension as a function of pH (4 – 9) and Ca2+ revealed the existence of several species. Parallel factor analysis (PARAFAC) indicated the formation of three surface species totally. In the absence of Ca2+, the ≡XO UO2+ and ≡XO UO2CO3– surface complexes were formed, whereas the presence of Ca2+ leads to the formation of ≡XO UO2+ and ≡XO UO2OH as the formation of the aqueous Ca2UO2(CO3)3 complex reduces the free UO22+ concentration in the solution. Additional, ATR FT-IR confirmed an outer-sphere surface species in the absence of Ca2+. These experimental results were used for the assessment of surface complexation parameters to improve the basis for a mechanistic modeling of the sorption processes of U(VI) onto orthoclase and muscovite including the influence of Ca2+. Namely, log K≡XO-UO2+ = 1.69 and log K≡XO-UO2CO3− = 8.96 were determined for sorption onto orthoclase, whereas log K≡XO-UO2+ = 0.41 and log K≡XO-UO2CO3− = 8.71 best describe sorption onto muscovite.

Keywords: Sorption; uranium; orthoclase; muscovite; calcium; TRLFS; ATR FT-IR; PARAFAC; SCM

Permalink: https://www.hzdr.de/publications/Publ-22187


Ultra-fast X-ray tomographic measurement of activated sludge aerated by membrane and monolithic spargers

Sommer, A.-E.; Wagner, M.; Reinecke, S. F.; Bieberle, M.; Barthel, F.; Hampel, U.

Abstract

The removal of nitrogen and organic components by micro-organisms is an essential step in the biodegradable wastewater treatment plants. These biological reactions take place in large aerated cross flow reactors. In fact, up to 80 % of the total energy budget of wastewater treatment plants is consumed by the aeration process. Engineering and design of the plants are mostly based on empirical knowledge and limited instrumentation for single points of measurement. Thus, the complex hydrodynamic and biochemical processes in the large-scale vessels are not well understood, and there is a high potential for optimization of these processes. Recently, numerical tools, such as CFD, have been used for the design and prediction of improved operation of the reactors. However, the models used in the software show a significant deviation from experimental data and need improvement due to the complexity of the multiphase flows of aerated sludges (bubbles, microbial flakes, water). A detailed study has been carried out in a vertical column of 3.5 m in height at HZDR to obtain an improved understanding of the hydrodynamics of aerated sludges. To capture the temporal evolution of the rising bubbles in the opaque liquors the ultra-fast electron beam X-ray tomography system of HZDR was used. The target parameters are bubble size distribution, equivalent sauter diameter of the bubbles, bubble rise velocity and local gas hold-up under the variation of sparger type (rubber, monolithic material), gas flow rate, rheology of the fluid (deionized water, salty water, sludge) and height in the liquid column. Therefore enhanced image analysis algorithms, developed at HZDR, were applied to the reconstructed tomographic images, which are also presented in the paper. In the future, the experimental data set will be used as reference data for the improvement of numerical models of CFD software.

Keywords: ultra-fast X-Ray tomography; activated sludge; aeration

Involved research facilities

  • TOPFLOW Facility
  • Lecture (Conference)
    7th International Symposium on Process Tomography (ISPT7), 01.-03.09.2015, Dresden, Deutschland
  • Contribution to proceedings
    7th International Symposium on Process Tomography (ISPT7), 01.-03.09.2015, Dresden, Deutschland
    Proceedings of the 7th International Symposium on Process Tomography

Permalink: https://www.hzdr.de/publications/Publ-22186


Macro-Mixing characterisation of a stirred model fermenter of non-NEWTONIAN liquid by flow following sensor particles and ERT

Reinecke, S.; Deutschmann, A.; Jobst, K.; Hampel, U.

Abstract

Investigation of the fluid circulation and the macro-mixing process in a stirred model fermenter of non-NEWTONIAN liquid was conducted by the comparative use of flow following sensor particles and ERT. Average fluid circulation times were estimated from (i) the measured vertical position of the sensor particle, (ii) the fluctuating ERT signals of single ERT planes and (iii) the measured mixing times of ERT-NaCl tracer experiments. The estimated average circulation times of all the three methods are comparable for the two investigated impeller positions. Furthermore, axial residence profiles of the sensor particles were extracted, which reveal the impact of the impeller configuration to the axial mixing homogeneity. Moreover, the results confirm the conclusions about the effect of the lifted impeller position derived by Reinecke et al. (2012) in a 1000 L pilot fermenter. The excellent detectability of the particles and the consistent results confirm the feasibility of the combined method for further investigation of the complex flows in biogas fermenters.

Keywords: macro mixing; circulation time; hydrodynamics; stirred tank; biogas fermenter; flow follower; sensor particle; ERT

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Permalink: https://www.hzdr.de/publications/Publ-22185


Instrumentierte Strömungsfolger mit erweiterter Positionsdetektion und Auftriebseinheit

S. Reinecke; Hampel, U.

Abstract

Zur Untersuchung der ablaufenden Prozesse in großen Behältern, wie z. B. Biogasfermentern, Bioreaktoren und Belebtschlammbecken, wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt [1]. Die Sensorpartikel werden als auftriebsneutrale Strömungsfolger eingesetzt und erfassen dabei kontinuierlich Prozessparameter. Diese Daten werden nach der Rückgewinnung der Sensorpartikel aus dem Prozess einem computergestützten Analysesystem zur Verfügung gestellt. Die erweiterten Sensorpartikel bestehen aus robusten Kapseln, welche mit einer integrierten Messelektronik und einer mechanischen Auftriebseinheit ausgestattet sind (siehe Abb. 1). Das Systemkonzept berücksichtigt derzeit miniaturisierte Sensoren für die Umgebungstemperatur, die Eintauchtiefe als Funktion des hydrostatischen Drucks, die Beschleunigung, die Drehrate und das Magnetfeld. Das Konzept ist zudem offen für die Einbindung ergänzender miniaturisierter Messfühler, wie z. B. für pH-Wert und Gelöst-Sauerstoff. Die Auftriebseinheit erlaubt eine automatisierte Tarierung der Sensorpartikel im ruhenden Prozessmedium, wodurch ein aufwändiges manuelles Justieren der Partikelmasse entfällt. Zudem ist mit der Auftriebseinheit eine erleichterte Rückgewinnung der Sensorpartikel von der Flüssigkeitsoberfläche nach Beendigung der Messung möglich.
Im Beitrag werden das erweiterte Konzept zur Positionsdetektion der Strömungsfolger und erste Testergebnisse vorgestellt. Es werden zum einen die Signale der Beschleunigung, der Drehrate und der magnetischen Flussdichte zur Rekonstruktion von Positionsveränderungen genutzt. Weiterhin ist die Detektion von externen Positionsmarkern, wie z. B. dem Signal einer Tauschspule, möglich. Beide Varianten wurden in praxisrelevanten Szenarien getestet. Zudem wird sowohl die Dimensionierung und der Aufbau der integrierten Auftriebseinheit als auch der Test unter realen Strömungsbedingungen vorgestellt.

Involved research facilities

  • TOPFLOW Facility
  • Open Access Logo Contribution to proceedings
    12. Dresdner Sensor-Symposium, 07.-09.12.2015, Dresden, Deutschland, 978-3-9813484-9-1
    DOI: 10.5162/12dss2015/P8.2
  • Poster
    12. Dresdner Sensor-Symposium, 07.-09.12.2015, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22184


Instrumentierte Strömungsfolger zur Prozessdiagnose in gerührten Fermentern

Reinecke, S.

Abstract

Die Erzeugung von Energie aus Biogas ist ein wichtiger Baustein unseres zukünftigen Energiekonzepts. Das Biogas dafür wird in Biogasfermentern gewonnen. In den letzten Jahren ist die Anzahl solcher Anlagen allein in Deutschland auf etwa 8.000 gestiegen. Allerdings zeigt sich, dass die bisherige Ausnutzung des Potenzials, das das Biogas bietet, bisher sehr gering ist. Biogasanlagen verwenden nahezu keine Instrumentierung, um die Anlagentechnik geeignet steuern und damit effizient betreiben zu können. Dadurch ist auch das Wissen über die Mischvorgänge in Biogasfermentern und die entscheidenden Einflüsse auf die Prozessführung völlig unzureichend. Es wurde untersucht, wie man durch strömungsfolgende Sensoren, die in Biogasfermentern eingebracht werden und dann die relevanten Prozessparameter räumlich verteilt messen, Kenntnis über die ablaufenden Mischprozesse erlangt. Damit lassen sich einerseits direkte Schlussfolgerungen für den Betrieb von Biogasfermentern ableiten, andererseits aber auch theoretische Prozessmodelle entwickeln, validieren und anpassen, um Biogasanlagen zukünftig viel effizienter betreiben zu können.

Involved research facilities

  • TOPFLOW Facility
  • Invited lecture (Conferences)
    3. Fachkolloquium am Institut für Energie und Prozesstechnik der FH-Münster, 10.03.2015, Steinfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22183


High Curie temperature and perpendicular magnetic anisotropy in homoepitaxial InMnAs films

Yuan, Y.; Wang, Y.; Gao, K.; Khalid, M.; Wu, C.; Zhang, W.; Munnik, F.; Weschke, E.; Baehtz, C.; Skorupa, W.; Helm, M.; Zhou, S.

Abstract

We have prepared the dilute magnetic semiconductor (DMS) InMnAs with different Mn concentrations by ion implantation and pulsed laser melting. The Curie temperature of the In1−xMnxAs epilayer depends on the Mn concentration x, reaching 82K for x = 0.105. The substitution of Mn ions at the indium sites induces a compressive strain perpendicular to the InMnAs layer and a tensile strain along the in-plane direction. This gives rise to a large perpendicular magnetic anisotropy, which is often needed for the demonstration of the electrical control of magnetization and for spin-transfer-torque induced magnetization reversal

Keywords: dilute magnetic semiconductors; InMnAs; ion implantation; pulsed laser melting; perpendicular magnetic anisotropy

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-22182


Magnetic phase transitions and large magnetic entropy change with a wide temperature span in HoZn

Li, L.; Yuan, Y.; Zhang, Y.; Poettgen, R.; Zhou, S.

Abstract

CsCl-type HoZn undergoes two successive magnetic phase transitions: (i) paramagnetic to ferromagnetic (FM) at T-C similar to 72 K and (ii) a spin reorientation (SR) at T-SR similar to 26 K. Magnetization and modified Arrott plots indicate that HoZn undergoes a second-order magnetic phase transition around T-C. The obtained critical exponents have some small deviations from the mean-field theory, indicating a short range or a local magnetic interaction which is properly related to the coexistence of FM and SR transitions at low temperature. Two successive magnetic transitions in HoZn induce one broad pronounced peak together with a shoulder in the temperature dependence of the magnetic entropy change -Delta S-M(T) curves, resulting in a wide temperature range with a large relative cooling power (RCP). For a field change of 0-7 T, the maximum value of -Delta S-M is 15.2 J/kg K around T-C with a large RCP value of 1124 J/kg. The large reversible magnetocaloric effect (MCE) and RC indicate that HoZn is a good candidate for active magnetic refrigeration.

Keywords: HoZn compound; Magnetocaloric effect; Critical exponent; Large refrigeration capacity; Active magnetic refrigeration materials

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-22181


Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya

Schwanghart, W.; Bernhardt, A.; Stolle, A.; Hoelzmann, P.; Adhikari, B. R.; Andermann, C.; Tofelde, S.; Merchel, S.; Rugel, G.; Fort, M.; Korup, O.

Abstract

Geomorphic footprints of past large Himalayan earthquakes are elusive, though urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes. We present evidence of catastrophic valley infill following at least three medieval earthquakes in the Nepal Himalayas. Radiocarbon ages from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments near Pokhara, Nepal’s second largest city, match the timing of nearby M~8 earthquakes in ~1100, 1255, and 1344 AD. The upstream dip of these valley fills and X-ray fluorescence spectrometry of their provenance rule out any local source. Instead, geomorphic and sedimentary evidence is consistent with catastrophic debris flows that had invaded and plugged several tributaries with tens of meters of calcareous sediment from a Higher Himalayan source >60 km away.

Keywords: accelerator mass spectrometry; earthquake

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Permalink: https://www.hzdr.de/publications/Publ-22180


P1402 - Kontrolle einer therapeutischen Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl

Enghardt, W.; Fiedler, F.; Helmbrecht, S.

Abstract

Die Erfindung betrifft Verfahren und Einrichtungen zur Kontrolle einer therapeutischen Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl mittels eines Positronen-Emissions-Tomografen. Diese zeichnen sich insbesondere dadurch aus, dass eine therapeutische Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl mittels eines Positronen-Emissions-Tomografen während der Bestrahlung kontrollierbar ist. Dazu werden wahre Koinzidenzen mittels – des durch die erlaubte Zeitdifferenz des Auftreffens zweier Photonen in verschiedenen Detektoren des Tomografen bestimmten Koinzidenzzeitfensters und – der Differenz zwischen prompten Fenster und verzögerten Fenster ohne wahre Koinzidenzen ermittelt. Dabei sind sowohl das Koinzidenzzeitfenster als auch die Zeitdifferenz zwischen prompten und verzögerten Fenster ein ganzzahliges Vielfaches der durch die Frequenz der beschleunigenden Wechselspannung des Hochfrequenzbeschleunigers gegebenen Zeitdauer einer Mikropulsperiode des Teilchenstrahls. Die Mikropulsperiode ist durch den Mikropuls und die Pause zwischen Mikropulsen definiert. Diese Zeitdauer ist durch die Frequenz der die Teilchen des Teilchenstrahls beschleunigenden Wechselspannung gegeben und damit zu wählen.

Involved research facilities

Related publications

  • Patent
    DE102014202828 - Erteilung 02.07.2015, Nachanmeldung: WO, JP

Permalink: https://www.hzdr.de/publications/Publ-22178


Grid studies for the simulation of resolved structures in an Eulerian two-fluid framework

Gauss, F.; Lucas, D.; Krepper, E.

Abstract

The influence of the grid size on the rise velocity of a single bubble simulated with an Eulerian two-fluid method is investigated. This study is part of the development of an elaborated Eulerian two-fluid framework, which is able to predict complex flow phenomena as arising in nuclear reactor safety research issues. Such flow phenomena cover a wide range of interfacial length scales. An important aspect of the simulation method is the distinction into small flow structures, which are modeled, and large structures, which are resolved. To investigate the requirements on the numerical grid for the simulation of such resolved structures the velocity of rising gas bubbles is a good example since theoretical values are available. It is well known that the rise velocity of resolved bubbles is clearly underestimated in a one-fluid approach if they span over only few numerical cells. In the present paper it is shown that in the case of the two-fluid model the bubble rise velocity depends only slightly on the grid size. This is explained with the use of models for the gas–liquid interfacial forces. Good approximations of the rise velocity and the bubble shape are obtained with only few grid points per bubble diameter. This result justifies the resolved treatment of flow structures, which cover only few grid cells. Thus, a limit for the distinction into resolved and modeled structures in the two-fluid context may be established.

Keywords: multiphase flow; grid study; single rising bubble; Eulerian two-fluid method; Volume of Fluid method; terminal rise velocity

Permalink: https://www.hzdr.de/publications/Publ-22177


Biomimetic Magnetic Silk Scaffolds

Samal, S. K.; Dash, M.; Shelyakova, T.; Declercq, H. A.; Uhlarz, M.; Banobre-Lopez, M.; Dubruel, P.; Cornelissen, M.; Herrmannsdörfer, T.; Rivas, J.; Padeletti, G.; de Smedt, S.; Braeckmans, K.; Kaplan, D. L.; Dediu, V. A.

Abstract

Magnetic silk fibroin protein (SFP) scaffolds integrating magnetic materials and featuring magnetic gradients were prepared for potential utility in magnetic-field assisted tissue engineering. Magnetic nanoparticles (MNPs) were introduced into SFP scaffolds via dip-coating methods, resulting in magnetic SFP scaffolds with different strengths of magnetization. Magnetic SFP scaffolds showed excellent hyperthermia properties achieving temperature increases up to 8 °C in about 100 s. The scaffolds were not toxic to osteogenic cells and improved cell adhesion and proliferation. These findings suggest that tailored magnetized silk-based biomaterials can be engineered with interesting features for biomaterials and tissue-engineering applications.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22176


Capture Gamma-Ray Spectroscopy and Related Topics, Proceedings of the Fifteenth International Symposium

Schwengner, R.; Zuber, K.; (Editors)

Abstract

The Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15) was organized by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Technische Universität (TU) Dresden and held at TU Dresden from August 25 to August 29, 2014.
CGS15 was the fifteenth symposium in a series that started in 1969.
This conference continued the general themes of earlier meetings with special emphasis on gamma-ray spectroscopy used in neutron capture and also in a wider context in nuclear structure, nuclear reactions, nuclear astrophysics, statistical properties of nuclei, nuclear probes for fundamental physics, nuclear data, novel techniques and applications.
These proceedings include a collection of articles from all these topics.

Keywords: Gamma-ray spectroscopy

Involved research facilities

Related publications

  • Open Access Logo Book (Editorship)
    France: EDP Sciences, 2015
    ISBN: 978-2-7598-1794-8

Downloads

Permalink: https://www.hzdr.de/publications/Publ-22175


Design of a 18F-labeled purinergic P2Y1 receptor (P2Y1R) ligand for brain imaging

Moldovan, R.-P.; Dukic-Stefanovic, S.; Wenzel, B.; Teodoro, R.; Deuther-Conrad, W.; Brust, P.

Abstract

Objectives: Purine nucleotides such as ATP and ADP are important extracellular signaling molecules in almost all tissues. Via P2Y1R activation they mediate brain functions by trophic effects like differentiation and proliferation but also via fast synaptic transmission. The understanding of its role in brain disorders is limited because of lack of suitable brain-penetrating P2Y1R-selective drugs. Chao and co workers recently reported the first non-nucleotidic, diarylurea ligands with high affinity and selectivity for the P2Y1R[1]. We selected this scaffold for the development a 18F labeled P2Y1R ligand for brain imaging.

Methods: Based on the lead compounds 1-3 (Ki = 6-8 nM),[1] we designed derivative 5, suitable for aliphatic radiofluorination using the corresponding tosyl precursor 4. The radiolabeling was systematically optimized (eg. phase transfer catalyst, solvent, temperature, amount of precursor and heating method) and [18F]5 successfully provided for subsequent evaluation. The lead structure was further modified by fluorinating pyridine at the 2-position, replacing the urea subunit C with 2 aminothiazole, and substituting ring D with various fluoroaromatic and non-aromatic rings.

Results: Reference compound 5 has been synthesized from the tosylate 4 in 62% yield. Under optimized conditions, [18F]5 has been obtained in high radiochemical yield (30%) and purity (≥99%) at a specific activity of ~182 GBq/µmol. A series of 30 new fluorinated derivatives has been synthesized.

Conclusions: The first 18F-labeled P2Y1R ligand, [18F]5 has been successfully synthesized. To evaluate the newly designed compounds, an in vitro binding assay using stably transfected P2Y1R-1321N1 cells and [18F]5 is currently developed.

Literature: [1] Chao et al. J. Med. Chem. 2013, 56, 1704−1714

  • Lecture (Conference)
    23. Jahrestagung der AG Radiochemie / Radiopharmazie, 10.-12.09.2015, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22174


Network-like arrangement of mixed-valence uranium oxide nanoparticles after glutathione-induced reduction of uranium(VI)

Kretzschmar, J.; Haubitz, T.; Hübner, R.; Weiss, S.; Husar, R.; Brendler, V.; Stumpf, T.

Abstract

Glutathione (GSH), a ubiquitous intracellular reducing tripeptide, is able to reduce hexavalent uranium, U(VI), to its tetravalent form, U(IV), in aqueous media in vitro, inducing the formation of nanocrystalline mixed-valence uranium oxide particles. After initial reduction to U(V) and subsequent dismutation, yielded U(IV) rapidly hydrolyses at near-neutral conditions forming 2–5 nm sized nanoparticles. The latter further aggregate to 20–40 nm chain-like building blocks that finally arrange as network-like structures.

Keywords: glutathione; uranium; redox reaction; uraninite; nanocrystal; TEM; environmental science

Related publications

Permalink: https://www.hzdr.de/publications/Publ-22173


Advanced tomographic imaging for multi-phase flow investigations in industrial apparatuses

Bieberle, M.; Barthel, F.; Rabha, S.; Schubert, M.; Bieberle, A.; Hampel, U.

Abstract

Investigations on two- and multiphase flow phenomena inside technical apparatuses or feedings are of highest interest for designers and operators since the knowledge helps to understand the fundamental physics behind processes, e.g. in chemical and process engineering. It expedites the development of safer and more efficiently operated industrial facilities. Furthermore, measured data are used to validate new models developed for multiphase flow simulation, e.g. CFD. For non-intrusive two-phase flow investigations, two radiation-based computed tomography (CT) scanners are operated at the Helmholtz-Zentrum Dresden - Rossendorf (HZDR) at the department of Fluid Dynamics: a high-resolution gamma-ray computed tomography scanner (HireCT) and an ultrafast electron beam X-ray CT scanner (ROFEX). They are able to recover non-superimposed cross-sectional material distributions of the scanned plane or volume section within the flow as time averaged images or time resolved image sequences. The capabilities of both CT systems are demonstrated exemplarily at experiments on an industrial scale bubble column, a fluidized bed and a static mixer.

Keywords: computed tomography; multi-phase flow; CFD

Involved research facilities

  • TOPFLOW Facility
  • Contribution to proceedings
    Fachtagung “Lasermethoden in der Strömungsmesstechnik”, 08.-10.09.2015, Dresden, Deutschland
    Lasermethoden in der Strömungsmesstechnik, Karlsruhe: Deutsche Gesellschaft für Laser-Anemometrie, 978-3-9816764-1-9, 8-1-8-8
  • Lecture (Conference)
    Fachtagung “Lasermethoden in der Strömungsmesstechnik”, 08.-10.09.2015, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22172


Commissioning and first RF results of the second 3.5 cell SRF gun for ELBE

Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Eremeev, G. V.; Kneisel, P.; Stirbet, M.; Turlington, L.

Abstract

As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation at Helmholtz-Zentrum Dresden-Rossendorf, it turned out that the specified performance to realize an electron energy of 9.4 MeV has not been achieved. Instead, the resonator of the gun was limited by field emission to about one third of this value and the measured beam parameters remained significantly below its expectations.

However, to demonstrate the full potential of this electron source for the ELBE linear accelerator, a second and slightly modified SRF gun was developed and built in collaboration with Thomas Jefferson National Accelerator Facility.

We will report on commissioning and first RF results of this new SRF gun. This includes in particular the characterization of the most important RF properties as well as their comparison with previous vertical test results. Additionally, investigations are presented that try to explain a particle contamination that happened recently during the first cathode transfer.

Keywords: SRF gun; superconducting radio frequency electron injector; ELBE linear accelerator

Involved research facilities

Related publications

  • Lecture (Conference)
    The 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 07.-12.06.2015, Stony Brook, NY 11794, USA

Permalink: https://www.hzdr.de/publications/Publ-22171


Radiation Effects in Solid Nitrogen and Nitrogen-Containing Matrices: Fingerprints of N4+ Species

Savchenko, E. V.; Khyzhniy, I. V.; Uyutnov, S. A.; Barabashov, A. P.; Gumenchuk, G. B.; Beyer, M. K.; Ponomaryov, A. N.; Bondybey, V. E.

Abstract

The radiation effects and relaxation processes in solid N2 and N2-doped Ne matrices, preirradiated by an electron beam, have been studied in the temperature range of 5–40 and 5–15 K, respectively. The study was performed using luminescence methods: cathodoluminescence CL and developed by our group nonstationary luminescence NsL, as well as optical and current activation spectroscopy methods: spectrally resolved thermally stimulated luminescence TSL and exoelectron emission TSEE. An appreciable accumulation of N radicals, N+, N2 + ions, and trapped electrons is found in nitrogen-containing Ne matrices. Neutralization reactions were shown to dominate relaxation scenario in the low-temperature range, while at higher temperatures diffusion-controlled reactions of neutral species contribute. It was conceived that in α-phase of solid N2, the dimerization reaction (N2 + + N2 → N4 +) proceeds: “hole self-trapping”. Tetranitrogen cation N4 + manifests itself by the dissociative recombination reaction with electron: N4 + + e → N2*(a’1Σu ) + N2 → N2 + N2 + hν. In line with this assumption, we observed a growth of the a’1Σu → X1Σg + transition intensity with an exposure time in CL spectra and the emergence of this emission in the course of electron detrapping on sample heating in the TSL and NsL experiments.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22170


Dependence of the inverse magnetocaloric effect on the field-change rate in Mn3GaC and its relationship to the kinetics of the phase transition

Scheibel, F.; Gottschall, T.; Skokov, K.; Gutfleisch, O.; Ghorbani-Zavareh, M.; Skourski, Y.; Wosnitza, J.; Cakir, Ö.; Farle, M.; Acet, M.

Abstract

We study the dependence of the magnetocaloric effect on the magnetic field-change-rate the first order magnetostructural transition in Mn3GaC by measuring the adiabatic temperature change ΔT at three different time scales: 11 mTs-1, 700 mTs-1, and ~1000 Ts-1. We find that the Maximum adiabatic temperature-change of about 5 K is reached in the 11 mTs-1 and 700 mTs-1 rates, whereas for the ~1000 Ts-1 the transition lags the change in the magnetic field so that the maximum adiabatic temperature-change is not attained.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22169


Optical conductivity evidence of clean-limit superconductivity in LiFeAs

Lobo, R. P. S. M.; Chanda, G.; Pronin, A. V.; Wosnitza, J.; Kasahara, S.; Shibauchi, T.; Matsuda, Y.

Abstract

We measured the optical conductivity of superconducting LiFeAs. In the superconducting state, the formation of the condensate leads to a spectral-weight loss and yields a penetration depth of 225 nm. No sharp signature of the superconducting gap is observed. This suggests that the system is likely in the clean limit. A Drude-Lorentz parametrization of the data in the normal state reveals a quasiparticle scattering rate supportive of spin fluctuations and proximity to a quantum critical point.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22168


Doping effects of Sb in FeTe1-xSbx single crystals

Wang, X. F.; Zhang, Z. T.; Chen, X. L.; Kan, X. C.; Li, L.; Sun, Y. P.; Zhang, L.; Xi, C. Y.; Pi, L.; Yang, Z. R.; Zhang, Y. H.

Abstract

We investigated the doping effects of Sb on the magnetic, transport and structural properties in FeTe1-xSbx single crystals. Resistivity, magnetic susceptibility and heat capacity experiments consistently reveal that the magnetic/structural transition temperature TN ~ 70 K in undoped Fe1.05Te is gradually suppressed by Sb doping, but no superconductivity is observed for x up to 10%. It is found that the electronic heat capacity coefficient gamma increases with Sb content, implying the increase of the density of states at Fermi level. Referring to previous calculation reports, this means that the Sb substituent plays a role of hole carrier doping, which is consistent with our measurements on Hall coefficient. Structural Analysis shows that Sb doping induces an expansion of the lattice along the a axis and a shrinkage along the c axis. Our work suggests that the antiferromagnetism in Fe1+yTe may be different in nature with other parent compounds of FeAs-based systems.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22167


Experimental and numerical investigation of flow structure and heat transfer during high pressure condensation in a declined pipe at COSMEA facility

Geißler, T.; Szijarto, R.; Beyer, M.; Hampel, U.; Prasser, H.-M.; Walther, M.; Leyer, S.

Abstract

Reliability and safety are perpetual topics in the development of nuclear installations. Generation III reactor concepts contain additional passive safety systems for improved accident control and mitigation. Main aspect of these passive systems is to operate with a minimum of external energy and signals. One example is the emergency condenser of the KERENA reactor concept, which removes heat from the core passively, e.g. after a station blackout. The governing natural circulation flow with condensation is only coarsely understood and current simulation methods need to be improved. During the condensation process a complex interaction between flow structure and heat transfer takes places and this determines the total efficiency of the passive safety system and hence the reliability in managing an incident.
The experimental facility COSMEA (condensation test rig for flow morphology and heat transfer studies) at HZDR is designated to provide experimental results to support the further development of CFD calculation methods. The test rig consists of a 3 m long emergency condenser pipe (ID 43 mm) which is 0.76° inclined and cooled by forced water flow. The experiments are conducted in a pressure range between 5 bar and 65 bar with steam mass flow rates up to 1 kg/s. Measurements of pressure, temperature, flow rate and condensation rate deliver integral understanding of the process. To investigate the details of the resulting stratified flow structures, x-ray tomography is applied. Parallel temperature measurements inside the heat transferring wall provide information about the azimuthal distribution of the heat flux.
A phase injection system was developed to operate the experiment in a stepwise condensation mode, which allows the measuring of condensation rates, flow morphologies and heat transfer distribution for different steam fraction values. The combination between cross sectional images from x-ray tomography and the azimuthally resolved heat transfer clarify the coupling between flow structure and heat transfer during condensation.
The experimental results are supported by a system code calculation. The COSMEA facility was modeled with the RELAP5 code. The original condensation model of the code was modified such that the heat transfer coefficient depends on the local mass fraction of the flow field. The experimental and calculation results agreed well for the steady state condensation process in the condensation rate, secondary side temperature and the heat flux data.

Keywords: two-phase flow; passive safety system; TOPFLOW; heat transfer; condensation; COSMEA; x-ray tomography

Involved research facilities

  • TOPFLOW Facility
  • Contribution to proceedings
    NURETH-16, 16th International Topical Meeting on Nuclear Reactor Thermalhydraulics, 30.08.-04.09.2015, Chicago, USA
    Proceedings of NURETH-16
  • Lecture (Conference)
    NURETH-16, 16th International Topical Meeting on Nuclear Reactor Thermalhydraulics, 30.08.-04.09.2015, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-22166


First evidence of low energy enhancement in Ge isotopes

Renström, T.; Nyhus, H.-T.; Utsunomiya, H.; Larsen, A. C.; Siem, S.; Guttormsen, M.; Filipescu, D. M.; Gheorghe, I.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Glodariu, T.; Görgen, A.; Hagen, T. W.; Lui, Y.-W.; Negi, D.; Ruud, I. E.; Sahin, E.; Schwengner, R.; Shima, T.; Takahisa, K.; Tesileanu, O.; Tornyi, T. G.; Tveten, G. M.; Wiedeking, M.

Abstract

The γ-strength functions and level densities of 73,74 Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74 Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ~ 1-13 MeV for 74 Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ~ 3 MeV towards lower γ energies. The obtained data show that both 73,74 Ge display an increase in strength at low γ energies.

Keywords: gamma-ray strength

Permalink: https://www.hzdr.de/publications/Publ-22165


Analysis of pion production data measured by HADES in proton-proton collisions at 1.25 GeV

Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A. V.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Dybczak, A.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Göbel, K.; Golubeva, M.; González-Díaz, D.; Guber, F.; Gumberidze, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Morinière, E.; Mousa, J.; Müntz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Vasiliev, T.; Weber, M.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.

Abstract

Baryon resonance production in proton-proton collisions at a kinetic beam energy of 1.25 GeV is investigated. The multi-differential data were measured by the HADES collaboration. Exclusive channels with one pion in the final state (nπ+ and pπ0) were put to extended studies based on various observables in the framework of a one-pion exchange model and with solutions obtained within the framework of a partial wave analysis (PWA) of the Bonn-Gatchina group. The results of the PWA confirm the dominant contribution of the Δ(1232), yet with a sizable impact of the N(1440) and non-resonant partial waves. The obtained resonance production cross sections provide a useful normalization for the further analysis of the Δ+ -> pe+e- Dalitz decay.

Permalink: https://www.hzdr.de/publications/Publ-22164


Low-Energy Magnetic Radiation

Frauendorf, S.; Beard, M.; Mumpower, M.; Schwengner, R.; Wimmer, K.

Abstract

A pronounced spike at low energy in the strength function for magnetic radiation (LEMAR) is found by means of Shell Model calculations, which explains the experimentally observed enhancement of the dipole strength. LEMAR originates from statistical low-energy M1-transitions between many excited complex states.
Re-coupling of the proton and neutron high-j orbitals generates the strong magnetic radiation. LEMAR is predicted for nuclides with A ~ 132 participating in the r-process of element synthesis. It increases the reaction rates by a factor of 2.5. The spectral function of LEMAR follows Planck's Law. A power law for the size distribution of the B(M1) values is found.

Keywords: Magnetic dipole radiation; shell model

Permalink: https://www.hzdr.de/publications/Publ-22163


Poly-disperse simulation of condensing steam-water flow inside a large vertical pipe

Liao, Y.; Lucas, D.

Abstract

The condensation of saturated steam bubbles in sub-cooled water inside a vertical pipe is studied by poly-disperse CFD simulations. Six test cases with varied pressure, liquid sub-cooling and diameter of the gas injection orifices are investigated. Baseline closures presented for non-drag forces in previous work are found to be reliable also in non-isothermal cases. The effect of bubble coalescence and breakup is negligible in cases with small orifice diameter. The Ranz-Marshall correlation leads to a global under-estimation of the condensation rate, especially at high pressure levels.

Keywords: Poly-disperse; CFD simulation; Condensation; Steam-Water

Involved research facilities

  • TOPFLOW Facility

Permalink: https://www.hzdr.de/publications/Publ-22162


Experimental and theoretical study on the co-current two-phase downflow regime transition in open solid foam packed reactors

Möller, F.

Abstract

The main objective of this Diploma thesis was to determine the regime transition between trickling and pulsing flow for solid ceramic foams made of silicium carbid with extra silicium coating (SiSiC). Two pressure transducers were used in order to determine this transition. Additional to the experimental determination, a predictive model was developed after the idea of Grosser et al. (1988) as well as Attou and Ferschneider (2000). Therefore, bed specific parameters (specific surface area, pressure drop parameters, static liquid holdup, porosity of the bed) and fluid specific parameters (gas and liquid density and viscosity, surface tension) had to be known. Since these models were only validated for conventional FBRs with a packing of spheres, modifications have been carried out in order to fit the model to foam related parameters.
In order to describe the regime transition through the models, further experiments had been carried out. The static liquid holdup as well as the singe phase (gas phase) pressure drop were investigated and afterwards modeled though different approaches.
To obtain the influences of changing the surface tension as well as the viscosity on the regime transition, additional experiments with tergitol and glycerin were carried out.
Three different pore sizes (20 PPI, 30 PPI and 45PPI) as well as two different foam diameters (0.05m and 0.1 m) were investigated with two different spray systems. For the change of viscosity and surface tension, only foams with a diameter of 0.1m had been used.

Keywords: Solid foam packing; trickle-bed reactor; flow regime transition; relative permeability concept; static holdup

Involved research facilities

  • TOPFLOW Facility
  • Diploma thesis
    TU Dresden, 2015
    Mentor: Zalucky, J., Schubert, M.
    124 Seiten

Permalink: https://www.hzdr.de/publications/Publ-22161


Neutron-capture experiment on 77Se with EXILL at ILL Grenoble

Lorenz, C.; John, R.; Massarczyk, R.; Schwengner, R.; Blanc, A.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Simpson, G.; Soldner, T.; Urban, W.; Valenta, S.; Belgya, T.

Abstract

The neutron capture reaction at 77 Se has been studied with cold neutrons in the course of the EXILL campaign at the high-flux reactor of the Institut Laue-Langevin Grenoble. A simulation of the detector array with Geant4 has been accomplished and evaluated. The detector response has been deduced and measured spectra were unfolded, which have been compared with simulations using γDex to determine strength functions.

Keywords: Neutron capture; gamma-spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-22160


Investigation of dipole strength up to the neutron separation energy at γELBE

Massarczyk, R.; Schwengner, R.; Bemmerer, D.; Beyer, R.; Hannaske, R.; Junghans, A. R.; Kempe, M.; Kögler, T.; Schramm, G.; Wagner, A.

Abstract

The bremsstrahlung facility at the ELBE accelerator offers the possibility to investigate dipole strength distributions up to the neutron-separation energies with photon up to 16 MeV in energy. The facility and various results for nuclides measured during recent years are presented. One example is the study of the N = 80 nuclide 136 Ba. The other presented example is the study of the chain of xenon isotopes from N = 70 to N = 80 which aimed to investigate the influence of nuclear deformation an neutron excess on the dipole strength in the pygmy region. An overview of the analysis is given. GEANT4 simulations were performed to determine the non-nuclear background that has to be removed from the measured spectra. This opens up the possibility to take into account also the strength of unresolved transitions. Simulations of gamma-ray cascades were carried out that consider the transitions from states in the quasi-continuum and allow us to estimate their branching ratios. As a result, the photoabsorption cross sections obtained from corrected intensities of ground-state transitions are compared with theoretical predictions and results within the chain of isotopes. With the help of the measured dipole distribution it is possible to describe gamma-ray spectra following neutron capture more precisely.

Keywords: photon scattering; nuclear structure; photon strength

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-22159


Combined study of the gamma-ray strength function of 114Cd with (n,γ) and (γ,γ’) reactions

Belgya, T.; Massarzyk, R.; Szentmiklósi, L.; Schramm, G.; Schwengner, R.; Junghans, A. R.; Wagner, A.; Grosse, E.

Abstract

Collaboration on strength function measurements and level density determinations is ongoing between the Budapest Prompt Gamma Neutron Activation Analysis and the ELBE Nuclear Physics groups within the framework of EU FP6 EFNUDAT project. The idea is to prove that good theoretical fits to the measured gamma-ray spectra collected in the (n,γ) and (γ,γ’) reactions can be carried out using common photon strength and level density functions over a wide spectral energy range from 1 to 10 MeV for the same residual nucleus. Here, preliminary results on the isotope pair of 113,114Cd are presented for which the neutron capture state in 114Cd has 1+ or 0+ spin and parity.

Keywords: electromagnetic strength function; neutron capture; resonance fluorescence

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-22158


Spin decoherence processes in the S=1/2 scalene triangular cluster (Cu3(OH))

Ponomaryov, A. N.; Kim, N.; Jang, Z. H.; van Tol, J.; Koo, H.-J.; Law, J. M.; Suh, B. J.; Yoon, S.; Choi, K. Y.

Abstract

We report the synthesis and magnetic properties of the molecular cluster Cu33−OH)(μ-OH)(μ-O2Ar4F-Ph)2(py)3(OTf)2, abbreviated as (Cu3(OH)). Using magnetization, electron paramagnetic resonance and spin dimer analysis, we derive a microscopic magnetic model of (Cu3(OH)) and measure the electron T1 and T2 relaxation times. The Cu2+ ions are arranged to form a distorted triangular structure with the three different exchange coupling constants J1 = −43.5 K, J2 = −53.0 K, and J3 = −37.7 K. At T = 1.5 K T1 is of the order of 10−4 s and T2 is evaluated to be 0.26 μs. We find that the temperature dependence of 1/T1 and 1/T2 is governed by Orbach process and spin bath fluctuations, respectively. We discuss the role of spin–phonon mechanism in determining a spin decoherence time in a class of spin triangular clusters.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22157


Paramagnetic moments and time effects in melt-textured NdBaCuO system with Nd422 inclusions

Dias, F. T.; Vieira, V. N.; Silva, D. L.; Wolff-Fabris, F.; Kampert, E.; Almeida, M. L.; Mesquita, F.; Hneda, M.; Roa, J. J.

Abstract

We have performed magnetic measurements in two melt-textured NdBa2Cu3O7-δ samples with Nd422 inclusions under magnetic fields from 0.05 up to 14 T, applied parallel to the ab planes. The measurements were made with a superconducting quantum interference device (SQUID) and a vibrating sample magnetometer (VSM). Paramagnetic moments could be observed during FCC (field-cooled cooling) and FCW (field-cooled warming) experiments. This effect, known as Paramagnetic Meissner Effect (PME), persisted up to 14 T and strong irreversibilities were observed among FCC and FCW experiments, revealing the presence of time effects. These time effects were confirmed by specific magnetic relaxation experiments in different cooling rates and temperatures, showing an anomalous and curious paramagnetic behavior. We explain our results based on the flux-compressed state generated within nonsuperconducting regions of the sample, such as the Nd422 inclusions dispersed into the superconducting matrix. These inclusions may produce a strong vortex pinning that stabilize the paramagnetic state, allowing the admission of extra vortices into the sample responsible for the positive moments during the relaxation experiments.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22156


Electron-tunneling measurements of low-Tc single-layer Bi2+xSr2−yCuO6+δ: Evidence for a scaling disparity between superconducting and pseudogap states

Jacobs, T.; Katterwe, S. O.; Motzkau, H.; Rydh, A.; Maljuk, A.; Helm, T.; Putzke, C.; Kampert, E.; Kartsovnik, M. V.; Krasnov, V. M.

Abstract

We experimentally study intrinsic tunneling and high magnetic field (up to 65 T) transport characteristics of the single-layer cuprate Bi2+xSr2−yCuO6+δ, with a very low superconducting critical temperature Tc ≲ 4 K. It is observed that the superconducting gap, the collective bosonic mode energy, the upper critical field, and the fluctuation temperature range are scaling down with Tc, while the corresponding pseudogap characteristics remain the same as in high-Tc cuprates with 20 to 30 times higher Tc. The observed disparity of the superconducting and pseudogap scales clearly reveals their different origins.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-22155


Charakterisierung der Oberflächenkomplexe der Oxoanionen von Se(VI) und Tc(VII) an Mineral-Waser Grenzflächen

Foerstendorf, H.; Heim, K.; Franzen, C.; Jordan, N.

Abstract

79Se und 99Tc sind als Spaltprodukte im nuklearen Brennstoffkreislauf für die Sicherheitsanalyse eines zukünftigen Endlagers von besonderem Interesse. Eine Abschätzung der Migration dieser Elemente im Nah- und Fernfeld eines geologischen Tiefenlagers ist nur möglich auf der Basis der umfassenden Kenntnis der Wechselwirkungen der Spezies mit mineralischen Oberflächen. Insbesondere die Oxoanionen Se(VI)O4 2– und Tc(VII)O4 gelten auf Grund ihrer hohen Löslichkeit und negativen Ladung als besonders mobile Spezies in Aquiferen.
Die Oberflächenreaktionen von in Wasser gelösten Oxoanionen an Mineraloberflächen können mittels in situ Schwingungsspektroskopie dezidiert untersucht werden. Dabei können sowohl die Sorptions- als auch die Desorptionsreaktionen der gelösten Ionen an einer stationären mineralischen Phase in Echtzeit erfasst werden. [1–2]
Für das Selenation wurden an zwei verschiedenen Mineralphasen unterschiedliche Arten von außersphärischen Oberflächenkomplexen gefunden. Obwohl die makroskopischen Eigenschaften dieser Oberflächenkomplexe an beiden Mineralen auf eine außersphärische Anbindung (Physisorption) schließen lassen, zeigen die Infrarotspektren eine signifikant abweichende spektrale Signatur, die nur mit unterschiedlichen Molekülsymmetrien erklärt werden kann. So zeigen die Spektren je nach Mineraloberfläche, dass das Selenat mit einer leicht verzerrten – der aquatischen Spezies sehr ähnlichen – tetraedrischen bzw. mit einer bidendaten C2v Symmetrie an die Oberfläche sorbiert wird. Diese Spezies können demnach als „erweiterte“ bzw. als „klassische“ außersphärische Komplexe bezeichnet werden. [3–4]
Entsprechende Experimente mit dem isostrukturellen Tc(VII)O4 -Anion zeigen, dass auch dieses Ion vorwiegend außersphärische Oberflächenkomplexe an verschiedenen Mineraloberflächen bildet. Dabei weisen die ersten Ergebnisse auf eine geringere Spezifizität des TcO4 bei der Anbindung an die verschiedenen Oberflächen hin.

[1] Foerstendorf, H. et al. (2012) J. Colloid Interface Sci. 377, 299–306. [2] Müller, K. et al. (2015) Environ. Sci. Technol. 49, 2560–2567. [3] Jordan, N. et al. (2011) Geochim. Cosmochim. Acta 75, 1519–1530. [4] Jordan, N. et al. (2013) Geochim. Cosmochim. Acta 103, 63–75.

  • Poster
    GDCh-Wissenschaftsforum Chemie 2015 Chemie verbindet, 30.08.-02.09.2015, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22154


Sub-pixel resolution with a color X-ray camera

Nowak, S. H.; Bjeoumikhov, A.; von Borany, J.; Buchriegler, J.; Munnik, F.; Petric, M.; Radtke, M.; Renno, A. D.; Reinholz, U.; Scharf, O.; Wedell, R.

Abstract

The color X-ray camera SLcam® is a full-field, single photon detector providing scanning-free, energy and spatially resolved X-ray imaging. Spatial resolution is achieved with the use of polycapillary optics guiding Xray photons from small regions on a sample to distinct energy dispersive pixels on a charged-coupled device detector. Applying sub-pixel resolution, signals from individual capillary channels can be distinguished. Therefore, the SLcam® spatial resolution, which is normally limited to the pixel size of the charge-coupled device, can be improved to the size of individual polycapillary channels. In this work a new approach to a sub-pixel resolution algorithm comprising photon events also from the pixel centers is proposed. The details of the employed numerical method and several sub-pixel resolution examples are presented and discussed.

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Permalink: https://www.hzdr.de/publications/Publ-22153


Analysis of mononuclear uranyl(VI) hydroxo complexes using TRLFS and PARAFAC

Drobot, B.; Bauer, A.; Steudtner, R.; Tsushima, S.; Raff, J.; Brendler, V.

Abstract

Speciation analysis of fast equilibrium processes is often challenging. Metal hydrolysis is one example of such a system. It is the basis for more complex aquatic systems and thus a deep understanding of those systems is indispensable. In the case of uranyl(VI) hydrolysis spectroscopic studies are hindered by low solubility over an wide pH range. Additionally occurrence of polynuclear complexes further complicates the system when working close to the solubility limit (e.g. 10-5 M uranyl(VI)). In a previous study we demonstrated that a combination of luminescence spectroscopic methods together with state of the art data analysis (parallel factor analysis; PARAFAC) and quantum chemical calculations is a powerful setup to gain information on that system [1]. Since uranyl(VI) has high affinities to several minerals and biopolymers systems containing trace metal concentrations have to be considered. In the present study we focus on this low concentration range (10-8 M uranyl(VI)).
We were able to extract thermodynamic constants for this system [(UO2(OH)(H2O)4+), (UO2(OH)2(H2O)3), (UO2(OH)3(H2O)2-)] using optimized data processing. Furthermore, advanced deconvolution of individual luminescence spectra demonstrates the correlation of luminescence spectroscopy and vibrational spectroscopy. Raman frequencies result from symmetrical stretching of the uranyl(VI) unit. We could show that features of individual emission spectra are separated by the same energy. Thus a further luminescence signal to chemical structure correlation is demonstrated which was missing for that system.

  • Poster
    GDCh-Wissenschaftsforum Chemie 2015, 30.08.-02.09.2015, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22152


Repeatability of tumor SUV quantification: the role of variable blood SUV

van den Hoff, J.; Hofheinz, F.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-22151


Novel (pyrazolyl)benzenesulfonamides with a nitric oxide-releasing moiety as selective cyclooxygenase-2 inhibitors

Bechmann, N.; Kniess, T.; Köckerling, M.; Pigorsch, A.; Steinbach, J.; Pietzsch, J.

Abstract

Inhibition of cyclooxygenase-2 (COX-2) is a promising anti-inflammatory therapeutic strategy, but longterm medication with COX-2-inhibitors (coxibs) may be associated with adverse cardiovascular effects. Functionalization of existing lead structures with nitric oxide (NO)-releasing moieties is an auspicious approach to minimize these effects. In this regard, an organic nitrate (–O–NO2) substituent was introduced at a (pyrazolyl)benzenesulfonamide lead structure. The novel NO-coxibs selectively inhibited COX-2 in a low micromolar range (IC50(COX-2): 0.22–1.27 lM) and are supposed to be promising antiinflammatory compounds with, in parallel, positive effects on vascular homeostasis.

Keywords: Anti-inflammatory therapy; Cardiovascular side effects; Celecoxib; Direct/indirect NO coupling; Griess assay; Organic nitrate

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-22150


Rational design of dual peptides targeting ghrelin and Y2 receptors to regulate food intake and body weight

Kilian, T. M.; Klöting, N.; Bergmann, R.; Els-Heindl, S.; Babilon, S.; Clément-Ziza, M.; Zhang, Y.; Beck-Sickinger, A. G.; Chollet, C.

Abstract

Ghrelin and Y2 receptors play a central role in appetite regulation inducing opposite effects. The Y2 receptor induces satiety, while the ghrelin receptor promotes hunger and weight gain. However, the food regulating system is tightly controlled by interconnected pathways where redundancies can lead to poor efficacy and drug tolerance when addressing a single molecule. We developed a multitarget strategy to synthesize dual peptides simultaneously inhibiting the ghrelin receptor and stimulating the Y2 receptor. Dual peptides showed dual activity in vitro, and one compound induced a slight diminution of food intake in a rodent model of obesity. In addition, stability studies in rats revealed different behaviors between the dual peptide and its corresponding monomers. The Y2 receptor agonist was unstable in blood, while the dual peptide showed an intermediate stability compared to that of the highly stable ghrelin receptor inverse agonist.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-22149


On the relation between Kaiser-Bessel blob and tube of response based modelling of the system matrix in iterative PET image reconstruction

Lougovski, A.; Hofheinz, F.; Maus, J.; Schramm, G.; van den Hoff, J.

Abstract

We investigate the question of how the blob approach is related to tube of response based modelling of the system matrix. In our model, the tube of response (TOR) is approximated as a cylinder with constant density (TOR-CD) and the cubic voxels are replaced by spheres. Here we investigate a modification of the TOR model that makes it effectively equivalent to the blob model, which models the intersection of lines of response (LORs) with radially variant basis functions ('blobs') replacing the cubic voxels. Implications of the achieved equivalence regarding the necessity of final resampling in blob-based reconstructions are considered. We extended TOR-CD to a variable density tube model (TOR-VD) that yields a weighting function (defining all system matrix elements) which is essentially identical to that of the blob model. The variable density of TOR-VD was modelled by a Gaussian and a Kaiser-Bessel function, respectively. The free parameters of both model functions were determined by fitting the corresponding weighting function to the weighting function of the blob model. TOR-CD and the best-fitting TOR-VD were compared to the blob model with a final resampling step (BLOB-RS) and without resampling (BLOB-NRS) in phantom studies. For three different contrast ratios and two different voxel sizes, resolution noise curves were generated. TOR-VD and BLOB-NRS lead to nearly identical images for all investigated contrast ratios and voxel sizes. Both models showed strong Gibbs artefacts at 4 mm voxel size, while at 2 mm voxel size there were no Gibbs artefacts visible.
The spatial resolution was similar to the resolution with TOR-CD in all cases. The resampling step removed most of the Gibbs artefacts and reduced the noise level but also degraded the spatial resolution substantially. We conclude that the blob model can be considered just as a special case of a TOR-based reconstruction. The latter approach provides a more natural description of the detection process and allows for modifications that are not readily representable within the blob framework.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-22148


Positron-Annihilation Lifetime Spectroscopy using Electron Bremsstrahlung

Wagner, A.; Anwand, W.; Butterling, M.; Cowan, T. E.; Fiedler, F.; Fritz, F.; Kempe, M.; Krause-Rehberg, R.

Abstract

A new type of an intense source of positrons for materials research has been set up at the superconducting electron linear. The source employs hard X-rays from electron-bremsstrahlung production generating energetic electron-positron pairs inside the sample under investigation. CW-operation allows performing experiments with significantly reduced pile-up artefacts in the detectors compared to pulsed mode operation in conventional accelerators. The high-resolution timing of the accelerator with bunch lengths below 10 ps full width at half maximum (FWHM) allows positron annihilation lifetime spectroscopy (PALS) measurements with high time resolution. A single-component annihilation lifetime of Kapton has been measured as (381.3 ± 0.3) ps. Employing segmented detectors for the detection of both annihilation photons allows for the first time to perform a 4D tomographic reconstruction of the annihilation sites including the annihilation lifetime.

Keywords: positrons materials research ELBE linac superconducting tomography

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Permalink: https://www.hzdr.de/publications/Publ-22147


Response of Multi-Strip Multi-gap Resistive Plate Chamber

Datta, U.; Chakraborty, S.; Rahaman, A.; Basu, P.; Basu, J.; Bemmerer, D.; Boretzky, K.; Elekes, Z.; Kempe, M.; Münzenberg, G.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.

Abstract

A prototype of Multi-strip Multi-gap Resistive Plate chamber (MMRPC) with active area 40 cm x 20 cm has been developed at SINP, Kolkata. Detailed response of the developed detector was studied with the pulsed electron beam from ELBE at Helmholtz-Zentrum Dresden-Rossendorf. In this report the response of SINP developed MMRPC with different controlling parameters is described in details. The obtained time resolution of the detector after slew correction was 91.5 +- 3 ps. Position resolution measured along x and across y the strip was 2.8+-0.6 cm and 0.58 cm, respectively. The measured absolute efficiency of the detector for minimum ionizing particle like electron was 95.8+-1.3 %. Better timing resolution of the detector can be achieved by restricting the events to a single strip. The response of the detector was mainly in avalanche mode but a few percentage of streamer mode response was also observed. A comparison of the response of these two modes with trigger rate was studied.

Keywords: Multi-strip Multi-gap Resistive Plate chamber (MMRPC) ELBE

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Permalink: https://www.hzdr.de/publications/Publ-22146


Combined phase distribution and particle velocity measurement in spout fluidized beds by ultrafast X-ray computed tomography

Bieberle, M.; Barthel, F.

Abstract

The spout fluidized bed is a very successful combination of spouted and fluidized bed, which is most interesting for processing particles with larger or varying diameter. However, the more complex hydrodynamics of the combined configuration is yet not fully understood. Here, we propose the application of ultrafast X-ray computed tomography (CT), which has proven to be a valuable measurement technique for the analysis of highly dynamic processes, for example multiphase flows. It is able to resolve material distributions with up to 8,000 frames per second and a spatial resolution down to 1 mm. Especially for opaque systems, such as fluidized beds, ultrafast X-ray CT can reveal details, which are not recoverable by e.g. optical measurement techniques. Besides the recovering of the dynamic phase distribution, determining local particle velocities is essential to understand the complex flow in fluidized beds. As we will demonstrate here for the first time, this is possible via a dual-plane ultrafast X-ray CT by using suitable marker particles. In this article, the methodology for determining particle velocities under highly dynamic conditions within a cylindrical spout fluidized bed is presented. Complementary analysis techniques for different flow conditions have been combined to increase confidence in the velocity data.

Keywords: velocity; spout fluidized bed; ultrafast; X-ray; computed tomography

Involved research facilities

  • TOPFLOW Facility

Permalink: https://www.hzdr.de/publications/Publ-22142


Coulomb Dissociation Experiment of P-27

Marganiec, J.; Beceiro-Novo, S.; Typel, S.; Wimmer, C.; Alvarez-Pol, H.; Aumann, T.; Boretzky, K.; Casarejos, E.; Chatillon, A.; Cortina Gil, D.; Datta-Pramanik, U.; Elekes, Z.; Fulop, Z.; Galaviz, D.; Geissel, H.; Giron, S.; Greife, U.; Hammache, F.; Heil, M.; Hoffman, J.; Johansson, H.; Kiselev, O.; Kurz, N.; Larsson, K.; Le Bleis, T.; Litvinov, Y.; Mahata, K.; Muentz, C.; Nociforo, C.; Ott, W.; Paschalis, S.; Plag, R.; Prokopowicz, W.; Rodriguez Tajes, C.; Rossi, D.; Simon, H.; Stanoiu, M.; Stroth, J.; Sümmerer, K.; Wagner, A.; Wamers, F.; Weick, H.

Abstract

The 26Si(p;gamma)27P reaction, which might play an important role in the rp process, was studied by the Coulomb Dissociation method. The experiment was performed at GSI, Darmstadt. A secondary 27P ion beam of 500 MeV/nucleon was directed onto a Pb target. From this experiment, the Coulomb Dissociation cross section will be deduced and then converted to the photoabsorption cross section, and the radiative-capture cross section. Also information on the structure of 27P will be obtained. The analysis is in progress.

Keywords: Coulom dissociation; radiative-capture; radioactive beams

Permalink: https://www.hzdr.de/publications/Publ-22141


Depth-resolved slow positron beam analysis of ECR proton and argon implanted graphite and boron nitride system

Ganguly, B. N.; Menon, R.; Yalagoud, N. P.; Bandyopadhyay, S. K.; Anwand, W.; Brauer, G.

Abstract

Layered materials and sp2 hybridized structures like graphite and hexagonal-boron nitride (h-BN) have been subjected to electron cyclotron resonance (ECR) ion beam implantation of proton and argon ions at different fluences and studied primarily employing slow positron beam technique using positron annihilation Doppler broadening spectroscopy (DBS). The results show remarkable structural perturbation effects in the implantation areas around the depth of 200–300 nm from the top surface, in both the systems but with glaring differences in the trends of the line shape analysis in terms of S and W parameters. Due to proton and argon ion implantation, structurally damaged lattice with open volume defects exists in graphite. But, for both the ion implantations at the high fluence, profound clustering effect of the respective atoms within the interstitial space are evident in h-BN. The structural effects of both graphite and h-BN lattice after the said implantation have been studied and corroborated through grazing incidence X-ray diffraction (GI-Xray) method and Raman scattering spectroscopy as complementary analytical techniques.

Keywords: BN; graphite; grazing incidence X-ray diffraction; positron beams; Raman spectroscopy; slow positrons

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Permalink: https://www.hzdr.de/publications/Publ-22140


How radio-ecological research helps to develop innovative nanobiomaterials

Raff, J.; Weinert, U.; Matys, S.; Vogel, M.; Suhr, M.; Günther, T.; Drobot, B.; Lehmann, F.; Kutschke, S.; Pollmann, K.

Abstract

The presentation introduces the Institute of Resource Ecology and the Helmholtz Institute Freiberg for Resource Technology and provides an insight into the work of the Biotechnology Group.

Keywords: radio-ecology; resource technology; nano-biotechnology

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  • Lecture (others)
    Arbeitskreisseminar Technische Chemie, 03.07.2015, Paderborn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22139


Investigating hadronic resonances in pp interactions with HADES

Przygoda, W.; Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, K.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc3, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.

Abstract

In this paper we report on the investigation of baryonic resonance production in proton-proton collisions at the kinetic energies of 1.25 GeV and 3.5 GeV, based on data measured with HADES. Exclusive channels npπ+ and ppπ0 as well as ppe+e− were studied simultaneously in the framework of a one-boson exchange model. The resonance cross sections were determined from the one-pion channels for Δ(1232) and N(1440) (1.25 GeV) as well as further Δ and N* resonances up to 2 GeV/c2 for the 3.5 GeV data. The data at 1.25 GeV energy were also analysed within the framework of the partial wave analysis together with the set of several other measurements at lower energies. The obtained solutions provided the evolution of resonance production with the beam energy, showing a sizeable non-resonant contribution but with still dominating contribution of Δ(1232)P33. In the case of 3.5 GeV data, the study of the ppe+e− channel gave the insight on the Dalitz decays of the baryon resonances and, in particular, on the electromagnetic transition form-factors in the time-like region. We show that the assumption of a constant electromagnetic transition form-factors leads to underestimation of the yield in the dielectron invariant mass spectrum below the vector mesons pole. On the other hand, a comparison with various transport models shows the important role of intermediate ρ production, though with a large model dependency. The exclusive channels analysis done by the HADES collaboration provides new stringent restrictions on the parameterizations used in the models.

Permalink: https://www.hzdr.de/publications/Publ-22138


Specific binding biomolecules

Raff, J.; Weinert, U.; Matys, S.; Vogel, M.; Suhr, M.; Günther, T.; Hofinger, J.; Drobot, B.; Lehmann, F.; Kutschke, S.; Pollmann, K.

Abstract

During evolution nature has evolved different kinds of specific binding macro-molecules being crucial for cell metabolism and their interaction with the environment. Most important examples therefore are proteins and nucleic acids. But beside biogenic molecules, specific proteins and nucleic acids can also be selected by doing an in vitro evolution using large molecule libraries. In this way specific ligands for various targets can be obtained allowing the development of new materials for different industrial applications.

Keywords: Sepcific binding; proteins; peptides; aptamers

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  • Invited lecture (Conferences)
    Professur-Seminar Biomaterialien, 01.07.2015, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22137


Developed turbulence and nonlinear amplification of magnetic fields in laboratory and astrophysical plasmas

Meinecke, J.; Tzeferacos, P.; Bell, A.; Bingham, R.; Clarke, R.; Churazov, E.; Crowston, R.; Doyle, H.; Drake, R. P.; Heathcote, R.; Koenig, M.; Kuramitsu, Y.; Kuranz, C.; Lee, D.; Macdonald, M.; Murphy, C.; Notley, M.; Park, H.-S.; Pelka, A.; Ravasio, A.; Reville, B.; Sakawa, Y.; Wan, W.; Woolsey, N.; Yurchak, R.; Miniati, F.; Schekochihin, A.; Lamb, D.; Gregori, G.

Abstract

The visible matter in the universe is turbulent and magnetized. Turbulence in galaxy clusters is produced by mergers and by jets of the central galaxies and believed responsible for the amplification of magnetic fields. We report on experiments looking at the collision of two laser-produced plasma clouds, mimicking, in the laboratory, a cluster merger event. By measuring the spectrum of the density fluctuations, we infer developed, Kolmogorov-like turbulence. From spectral line broadening, we estimate a level of turbulence consistent with turbulent heating balancing radiative cooling, as it likely does in galaxy clusters. We show that the magnetic field is amplified by turbulent motions, reaching a nonlinear regime that is a precursor to turbulent dynamo. Thus, our experiment provides a promising platform for understanding the structure of turbulence and the amplification of magnetic fields in the universe.

Keywords: galaxy clusters; laboratory analogues; lasers; magnetic fields; turbulence

Permalink: https://www.hzdr.de/publications/Publ-22136


Retention of trivalent Actinides by structural Incorporation

Schmidt, M.; Peschel, S.; Hofmann, S.; Walther, C.; Bosbach, D.; Stumpf, T.

Abstract

The incorporation of radionuclides into a host mineral’s crystal structure is a particularly efficient means of retention, due to the fact that the incorporated radionuclide is removed from the water path. The process is relevant, both, naturally occurring under repository conditions[1], and as a technical means for the sequestration of actinide waste streams. Consequently, it is of utmost importance to understand the processes leading up to the incorporation, as well as the structural properties of the formed solid solution at the molecular level[2].
We will give an overview on the incorporation of trivalent actinides and lanthanides into Ca- and Ln-bearing mineral phases of technical and geochemical relevance. The minor actinides dominate the radiotoxicity in a nuclear waste storage site over hundreds of thousands of years. For Am and Cm the trivalent oxidation states is the only relevant oxidation in aqueous solutions, and even Pu may be present as Pu(III) under reducing repository conditions. The trivalent actinides have ionic radii closely matched to their lanthanides homologues as well as calcium, making mineral phases with these host cations ideal matrices for the incorporation of the trivalent minor actinides.
To identify and characterize actinides in solid solutions at the trace concentration level, we make use of time-resolved laser fluorescence spectroscopy (TRLFS). TRLFS allows for speciation of Cm(III) at concentrations below 10-9 mol/L, or 1 ppm in the solid state. Cm TRLFS can be complemented by experiments with Eu(III), which, while less sensitive, are more sensitive to changes in the local coordination geometry of the fluorescent probe.
An overview will be given on the characterization of solid solutions of secondary phases relevant under repository conditions. We will compare a phase formed close to equilibrium (calcite) with a metastable phase undergoing a phase transition (vaterite[3]), as well as a phase from high-temperature synthesis (powellite[4]). The effect of various reaction parameters on the reactions, and their implications for the stability of the formed solid solutions, and hence the retention of the radionuclides will be discussed.
[1] T. Stumpf and Th. Fanghänel, J. Colloid Interf. Sci. 249, 119 (2002).
[2] H. Geckeis, et al., Chem. Rev. 113, 1016 (2013).
[3] M. Schmidt, et al., J. Colloid Interf. Sci. 351, 50 (2010).
[4] M. Schmidt, et al., Dalton Trans. 42, 8387 (2013).

Keywords: acitnides; solid solutions; TRLFS; calcite

  • Poster
    MIGRATION 2015: 15th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 13.-18.09.2015, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-22135


Recycling of magnesium chips

Ohmann, S.; Ditze, A.; Scharf, C.

Abstract

Magnesium chips were processed by means of re-melting. An important requirement of re-melting the chips is the removal of oil and moisture. The results show that using acetone in a soxhlet as an organic solvent is a more efficient method to obtain good results compared to vacuum distillation with a rotational evaporator. The subsequent re-melting has been successfully performed without the addition of flux between temperatures of 580 °C and 600°C. At this temperature range, the exothermic reaction of magnesium with the oxygen present in the surrounding atmosphere was avoided. Results show that more than 95 % of the magnesium chips were able to be recovered as metal. Experiments were performed at different scales to obtain production parameters for the recycling process. Larger particle size of magnesium chips were able to be faster remelted than the smaller ones. In the case of added lime for oil removal, the yield of recovered magnesium was lower due to the reaction towards magnesium foam. The ability of re-melting at low temperatures without the need for flux demonstrates the possibility of recovering virtually all of the metal from the chips.

Keywords: Magnesium; Chips; Recycling; Remelting; Analysis

  • Contribution to proceedings
    European Metallurgical Conference, 14.-17.06.2015, Düsseldorf, Germany
    EMC 2015 Volume 1: GDMB Verlag GmbH, 978-3-940276-61-2, 429-442

Permalink: https://www.hzdr.de/publications/Publ-22134


Understanding Cu mobilisation from Kupfershale leaching: [64Cu]CuS: Ligand identification, kinetic rates and modelling Preliminary Results.

Lippmann-Pipke, J.; Barthen, R.; Gründig, M.; Karimzadeh, L.; Schössler, C.; Mansel, A.; Grenzer, J.; Scholz, A.; Bischoff, L.; Schymura, S.; Kulenkampff, J.; Franke, K.; Lippold, H.

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  • Poster
    General Meeting 3, Ecometals, 23.-24.06.2015, Halle/Saale, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22133


Liquid phase epitaxy of binary III-V nanocrystals in thin Si layers triggered by ion implantation and flash lamp annealing

Wutzler, R.; Rebohle, L.; Prucnal, S.; Bregolin, F.; Hübner, R.; Voelskow, M.; Helm, M.; Skorupa, W.

Abstract

The integration of III-V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III-V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO2/Si/SiO2 layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of the III-V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.

Keywords: ion implantation; flash lamp annealing; III-V integration into silicon; nanostructure; liquid phase epitaxy; compound semiconductor

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Permalink: https://www.hzdr.de/publications/Publ-22132


Flash-Enhanced Atomic Layer Deposition: Basics, Opportunities, Review, and Principal Studies on the Flash-Enhanced Growth of Thin Films

Henke, T.; Knaut, M.; Hossbach, C.; Geidel, M.; Rebohle, L.; Albert, M.; Skorupa, W.; Bartha, J.

Abstract

Within this work, flash lamp annealing (FLA) is utilized to thermally enhance the film growth in atomic layer deposition (ALD). First, the basic principles of this flash-enhanced ALD (FEALD) are presented in detail, the technology is reviewed and classified. Thereafter, results of our studies on the FEALD of aluminum-based and ruthenium thin films are presented. These depositions were realized by periodically flashing on a substrate during the precursor exposure. In both cases, the film growth is induced by the flash heating and the processes exhibit typical ALD characteristics such as layer-by-layer growth and growth rates smaller than one angstrom/cycle. The obtained relations between process parameters and film growth parameters are discussed with the main focus on the impact of the FLA-caused temperature profile on the film growth.

Similar, substrate-dependent growth rates are attributed to the different optical characteristics of the applied substrates. Regarding the ruthenium deposition, a single-source process was realized. It was also successfully applied to significantly enhance the nucleation behavior in order to overcome substrate-inhibited film growth. Besides, this work addresses technical challenges for the practical realization of this film deposition method and demonstrates the potential of this technology to extend the capabilities of thermal ALD.

Keywords: flash lamp annealing; atomic layer deposition

Permalink: https://www.hzdr.de/publications/Publ-22131


Uranyl(VI) hydrolysis studied by luminescence spectroscopy

Drobot, B.; Steudtner, R.; Raff, J.; Brendler, V.; Geipel, G.; Tsushima, S.

Abstract

Speciation constitutes the basis for actinide complexation studies. These systems can be very complex and challenging especially because of the polynuclear species. An advanced combination of theoretical and experimental methods is proposed here. Continuous wave (CW) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) data of uranyl(VI) hydrolysis were analyzed using parallel factor analysis (PARAFAC). Distribution patterns of five major species were thereby derived under a fixed uranyl concentration (10-5) over a wide pH range from 2 to 11. UV (180 nm to 370 nm) excitation spectra were extracted for individual species. Time-dependent density functional theory (TD-DFT) calculations revealed ligand excitation (water, hydroxo, oxo) in this region and ligand-to-metal charge transfer (LMCT) responsible for luminescence. Thus excitation in the UV is extreme ligand sensitive and highly specific. Combining findings from PARAFAC and DFT the [UO2(H2O)5]2+ cation (aquo complex, 1:0) and four hydroxo complexes (1:1, 3:5, 3:7 and 1:3) were identified. Refined structural and thermodynamical data of uranyl(VI) hydrolysis is thus acquired.

  • Poster
    Second Joint Student Workshop on f-Element Chemistry, 09.-10.06.2015, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22130


Mikoskopische Lithiumverteilung in Pfadfinder-Mineralien

Neri, G.; Gernhäuser, R.; Lichtinger, J.; Renno, A. D.; Rugel, G.; Kudejova, P.; Revay, S.; Winkler, S.; Seiler, D.; Bendel, M.

Keywords: FRM II; Prompte Neutronenaktivierung; Lithium

  • Poster
    Tag der Physikerinnen, 23.06.2015, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22129


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