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33168 Publications

High-fluence Si-implanted diamond: formation of SiC nanocrystals and sheet resistance

Weishart, H.; Heera, V.; Eichhorn, F.; Pécz, B.; Barna, Á.; Skorupa, W.;
The sheet resistance and structural properties of high-fluence Si-implanted diamond were investigated. In order to minimize the radiation damage and to facilitate SiC formation the implantation was performed at 900 °C. All samples were subsequently annealed in an rf-heated furnace at 1500 °C for 10 minutes in order to remove defects and thermally unstable phases. X-ray diffraction, infrared absorption spectrometry and high-resolution cross-sectional transmission electron microscopy revealed the formation of a buried layer inside the implanted diamond, which contains SiC nanocrystallites. These SiC nanocrystals have a cubic structure and are nearly perfectly aligned with the diamond lattice. Raman spectroscopy was applied to analyze radiation-damage-induced graphitization in dependence on the implantation conditions. The sheet resistance of the samples was measured as function of temperature by four point probe technique in van-der-Pauw geometry. The decrease of the sheet resistance with increasing ion fluence unambiguously shows the influence of implantation-induced damage. The behavior of the sheet resistance can strongly be modified by additional nitrogen implantation The resulting higher conductivity is interpreted as partial incorporation of the nitrogen donor into the SiC nanocrystals. However, when the Si fluence exceeds a critical value of 5.3×1017 Si+cm-2 at 900 °C the diamond is irreversibly damaged and defect related conductivity dominates.
Keywords: silicon carbide (SiC), diamond crystal, ion bombardment, electrical conductivity

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Permalink: https://www.hzdr.de/publications/Publ-5313
Publ.-Id: 5313


Specific Humic Acid Model Substances for the Study of the Redox Behavior of Humic Acids in the Environment

Sachs, S.; Geipel, G.; Heise, K.-H.; Bernhard, G.;
The mobility of actinides in the environment is determined by their speciation which is strongly influenced by their oxidation states. Humic acids (HA) influences the speciation of actinides by complexation. However, they have also significant redox properties which can affect the oxidation states of actinides and consequently their migration in the environment. Thus, it is very important to understand both the complexation and the redox properties of HA in natural systems.
In order to study the redox behavior of HA in more detail we synthesized HA model substances with distinct redox functionalities based on the oxidation of diphenolic compounds in the absence and presence of amino acids. These humic acid-like model substances are characterized by elemental compositions and structural elements that are comparable to natural HA. However, they show phenolic/acidic OH group contents that are higher than those of natural HA. For characterization of the redox properties of these synthetic products, their Fe(III) and ferricyanide redox capacities (RC) were determined at pH 3 and pH 9.2, respectively, and compared to that of purified natural HA from Aldrich. The synthetic products show RC that are up to a factor of 11 and 4 higher than that of Aldrich HA at pH 3 and pH 9.2, respectively. Additionally, we modified, i.e., etherified the phenolic OH groups of these HA by methylation with diazomethane. Applying these modified HA we verified the dominating role of phenolic OH groups in the redox behavior of these HA.
The synthesized HA model substances with distinct redox functionalities are applied to further improve the knowledge on the impact of HA on the redox stability of actinides in the environment. We study the redox stability of uranium(VI) complexes of these HA depending on pH. Uranium(IV) that is formed due to the redox process is spectroscopically determined both directly by laser-induced photoacoustic spectroscopy and indirectly in form of the uranium(IV) arsenazo(III) complex.
Keywords: Humic substances, humic acids, actinides, migration, redox behavior, redox stability, uranium
  • Lecture (Conference)
    9th International Conference on Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere Migration '03, Gyeongju, Korea, 21.-26.September 2003

Permalink: https://www.hzdr.de/publications/Publ-5312
Publ.-Id: 5312


Effect of film thickness on a-Si:H properties grown with hydrogen diluted silane

Danesh, P.; Pantchev, B.; Grambole, D.; Schmidt, B.;
a-Si:H films prepared by plasma-enhanced CVD with 10% SiH4 in hydrogen have been studied concerning the effect of film thickness on the hydrogen concentration, interconnected void network and mechanical stress. The hydrogen concentration was determined by nuclear reaction analysis. The interconnected void network was studied by the method of ion exchange in glass substrate. The films were prepared at a substrate temperature in the range of 150 - 270°C. The results show that at the substrate temperature of 150°C the film structure develops as the void network decreases with the film thickness. At the substrate temperature of 270°C the film starts to grow with a dense structure and its structural improvement is manifested by the increase of the intrinsic compressive stress with the film thickness. The hydrogen concentration does not depend on the film thickness at any substrate temperature.
  • Applied Physics Letters, 80 (2002) 2463.

Permalink: https://www.hzdr.de/publications/Publ-5311
Publ.-Id: 5311


Uptake of Trivalent Actinides (Cm(III)) and Lanthanides (Eu(III)) by Calcium Silicate Hydrates: A Wet Chemistry and Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) Study

Tits, J.; Stumpf, T.; Rabung, T.; Wieland, E.; Fanghänel, T.;

The interaction of the two chemical homologues (Cm (III) and Eu(III)) with calcium silicate hydrates (CSH phases) at pH 13.3 has been investigated in batch-type sorption studies using Eu(III) and complemented with time-resolved laser fluorescence spectroscopy (TRLFS) using Cm(III). The sorption data for Eu(III) reveal fast sorption kinetics and a strong uptake by CSH phases with distribution ratios of (6±3)·105 L kg-1. Three different Cm(III) species have been identified: A non-fluorescing species, which was identified as a curium hydroxide (surface) precipitate, and two fluorescing Cm(III)/CSH sorbed species. The fluorescing sorbed species have characteristic emission spectra with main peak maxima at 618.9 nm and 620.9 nm and fluorescence emission lifetimes of 289 ± 11 µs and 1482 ± 200 µs, respectively. From the fluorescence lifetimes it was calculated that the two fluorescing Cm(III) species have one to two and no water molecules left in their first coordination sphere suggesting that these species are incorporated into the CSH structure. A structural model for Cm(III) and Eu(III) incorporation into CSH phases is proposed based on the substitution for Ca at two different types of sites in the CSH structure.
Key words : curium, europium, CSH, sorption, incorporation, TRLFS

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Permalink: https://www.hzdr.de/publications/Publ-5310
Publ.-Id: 5310


Change of the dipole strength distributions between the neighboring Gamma-soft nuclei 194Pt and 196Pt

Linnemann, A.; von Brentano, P.; Eberth, J.; Enders, J.; Fitzler, A.; Fransen, C.; Guliyev, E.; Herzberg, R.-D.; Käubler, L.; Kuliev, A. A.; von Neumann-Cosel, P.; Pietralla, N.; Prade, H.; Richter, A.; Schwengner, R.; Thomas, H. G.; Weisshaar, D.; Wiedenhöver, I.;
A nuclear resonance fluorescence experiment with two highly efficient EUROBALL Cluster detectors has been performed on the Gamma-soft nucleus 194Pt. Dipole excitations were observed between 2 and 4 MeV excitation energy. They are tentatively interpreted as the main fragments of the scissors mode based on the measurec excitation strengths and a comparison to microscopic calculations in the framework of the quasiparticle random phase approximation (QRPA). The data indicate large differences to the neighbouring isotope 196Pt: a doublingof the observed dipole strength and a shift of the energy centroid by about 600 keV. None of the currently available models is able to reproduce these features consistently in both nuclei.
Keywords: 194Pt(Gamma, Gamma'); Observed dipole strength for E&x;<4MeV; Deduced M1 scissors mode strength and energy centroid; Comparison ton ¹96;Pt
  • Physic letters B 554(2003)15-20

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Permalink: https://www.hzdr.de/publications/Publ-5309
Publ.-Id: 5309


Crack initiation determination for Charpy size specimens

Dzugan, J.;
An investigation in the field of the crack initiation determination for Charpy size specimens was carried out. An extensive literature survey of published methods for the crack initiation was performed. Methods based on the stretch zone width measurement, blunting line, multiple gauge measurement, electric potential drop, compliance changing rate, acoustic emission, ultrasonic method and magnetic emission are discussed in the theoretical part of the report. Analytical methods for the critical J-integral evaluation were also taken into account, as well as the expressions for the J-integral calculation. On the basis of the theoretical survey suitable measurement methods were chosen and applied in the experimental programme to several different materials. Namely blunting line related methods, multiple gauge methods, electric potential drop and compliance changing rate methods were used. The initiation J-integrals were evaluated with use of wide range of evaluation procedures and compared together in order to find a reliable method for the crack initiation determination. There was not found a universal method for the crack initiation determination. The performance of the methods was varying in dependence on the investigated material, so the results enable to choose perspective method for considered case.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-366 Februar 2003

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Permalink: https://www.hzdr.de/publications/Publ-5308
Publ.-Id: 5308


Nanocrystals synthesized by ion implantation into single crystals

Eichhorn, F.; Keywords: nanocrystals, x-ray diffraction, structural study, materials research
  • Lecture (Conference)
    13th ESRF Users' Meeting, February 12, 2003 as a short oral presentation

Permalink: https://www.hzdr.de/publications/Publ-5307
Publ.-Id: 5307


Clonogenic survival of human keratinocytes and rodent fibroblasts after irraditaion with 25 kV X-rays

Panteleeva, A.; Slonina, D.; Brankovic, K.; Spekl, K.; Pawelke, J.; Hoinkis, C.; Dörr, W.;
Low energy X-rays (Eph < 50 keV) are widely used in diagnostic radiology and radiotherapy. However, data on their relative biological effectiveness (RBE) are scarce. Of particular importance for risk estimation are the RBE value of X-rays in the range which is commonly used in mammography (10 - 30 keV). In the present study we have determined clonogenic survival after low-energy X-ray irradiation for 3 cell lines: primary human epidermal keratinocytes (HEKn), mouse fibroblasts (NIH/3T3) and Chinese hamster fibroblasts (V79). Experiments were performed with a 25 kV X-ray tube and compared to 200 kV X-rays as a reference. Compared to the effect of 200 kV X-rays, irradiation with 25 kV X-rays resulted in a decreased survival rate in the murine fibroblasts but not the human epithelial cell line. RBE value was calculated for 10 % surviving fraction. For HEKn cells, RBE was 1.33 ± 0.27, for NIH/3T3 cells 1.25 ± 0.07 and for V79 cells 1.10 ± 0.09. In conclusion, no consistently increased RBE was observed in the various cell lines. Nevertheless, a potential of increased cytogenetic changes has to be considered for risk estimation of low-energy X-rays.

Keywords: Soft X-rays, clonogenic survival, human keratinocytes, rodent fibroblasts, RBE
  • Radiation and Environmental Biophysics 42 (2003) 95-100 Epub 2003 Jun 26.

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Permalink: https://www.hzdr.de/publications/Publ-5305
Publ.-Id: 5305


Institute of Bioinorganic and Radiopharmaceutical Chemistry; Annual Report 2002

Johannsen, B.; Seifert, S.; (Editors)
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-363 Januar 2003

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Permalink: https://www.hzdr.de/publications/Publ-5304
Publ.-Id: 5304


MBE Growth of (Ga,In)As/Al(As,Sb) MQWs for Intersubband Transition Wavelenghts < 3.5 Micron

Biermann, K.; Böttcher, J.; Künzel, H.; Cronenberg, S.; Grahn, H. T.; Schrottke, L.; Georgiev, N.; Dekorsy, T.; Helm, M.;
Intersubband transitions in InP-based (Ga,In)As/(Al,In)As MQWs cover the wavelength range beyond 3.5 micron. Application of enhanced conduction band edge discontinuity allows for a reduced intersubband transition wavelength. This can be accomplished by replacing (Al,In)As by Al(As,Sb) barriers that can be grown lattice-matched to InP. (Ga,In)As/Al(As,Sb) MQWs were deposited by MBE and characterised using a combination of x-ray diffraction, photoluminescence and IR absorption measurements. Influence of well thickness and doping behaviour were systematically investigated. By
comparison with simplified theoretical calculations, the electronic band structure (interband and intersubband system) was deduced. Based on the corresponding results, the potential of (Ga,In)As/Al(As,Sb) MQWs for implementation in quantum cascade lasers will be discussed.
Keywords: quantum well structure, intersubband transition, X-ray diffraction, photoluminescence, IR absorption spectroscopy
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft (DPG) -Tagung, Fachverband Halbleiterphysik, HL3.3, Dresden, 2003

Permalink: https://www.hzdr.de/publications/Publ-5303
Publ.-Id: 5303


A XAS study of the local environments of cations in (U, Ce)O2

Matrin, P.; Ripert, M.; Petit, T.; Reich, T.; Hennig, C.; D'Acapito, F.; Hazemann, J.-L.; Proux, O.;
Mixed Oxide (MOX) fuel is usually considered as a solid solution formed by uranium and plutonium dioxides. Nevertheless, some physico-chemical properties of (U1-y, Puy)O2 samples manufactured under industrial conditions showed anomalies in the domain of plutonium contents ranging between 3 and 15 at.%. Cerium is commonly used as an inactive analogue of plutonium in preliminary studies on MOX fuels. Extended X-ray Absorption Fine Structure (EXAFS) measurements performed at the European Synchrotron Radiation Facility (ESRF) at the cerium and uranium edges on (U1-y, Cey)O2 samples are presented and discussed. They confirmed on an atomic scale the formation of an ideal solid solution for cerium concentrations ranging between 0 and 50 at.%.
  • Journal of Nuclear Materials 312 (2003) 103-110

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Permalink: https://www.hzdr.de/publications/Publ-5301
Publ.-Id: 5301


Double pinhole diffraction of white synchrotron radiation

Leitenberger, L.; Wendrock, H.; Bischoff, L.; Pietsch, U.; Panzer, T.; Grenzer, J.; Pucher, A.;
The spatial coherence of hard X-rays provided by a bending magnet of the storage ring BESSY II was investigated performing Young's interference experiment. The interference pattern was created by the diffraction of two 2 µm pinholes drilled into a thin tantalum foil by focused ion sputtering. Using an energy-dispersive detector with an energy resolution of 200 eV the interference pattern were detected simultaneously between 5 keV < E < 16 keV scanning a 5 µm pinhole through the detector window. The set-up is suitable to characterise the coherence properties of the beamline in a simple manner, i.e. to deduce parameters as the effective source size, the coherence length and the visibility. For the present case the visibility is near 100% at 5 keV and decreases to 20% at 16 keV.
Keywords: double slit experiment, coherent X-rays, white X-ray radiation
  • Lecture (Conference)
    7th. International Conference on X-Ray and Neutron Scattering, Lake Tahoe, California, USA, September 23 - 27, 2002
  • Physica B 336 (2003) 63 - 67

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Permalink: https://www.hzdr.de/publications/Publ-5300
Publ.-Id: 5300


Hard X-ray spatial coherence measurements using a double slit interference

Leitenberger, W.; Wendrock, H.; Bischoff, L.; Pietsch, U.; Panzer, T.; Grenzer, J.;
The spatial coherence of hard X-rays provided by a bending magnet of the storage ring BESSY II was investigated performing Young's interference experiment. The interference pattern was created by the diffraction of two 2 µm pinholes drilled into a thin tantalum foil by focused ion sputtering. Using an energy-dispersive detector with an energy resolution of 200 eV the interference pattern were detected simultaneously between 5 keV < E < 16 keV scanning a 5 µm pinhole through the detector window. The set-up is suitable to characterise the coherence properties of the beamline in a simple manner, i.e. to deduce parameters as the effective source size, the coherence length and the visibility. For the present case the visibility is near 100% at 5 keV and decreases to 20% at 16 keV.
Keywords: double slit experiment, coherent X-rays, white X-ray radiation
  • Lecture (Conference)
    Workshop on Exploiting the Coherence of X-rays, Motzen, Germany, September 23 - 24, 2002

Permalink: https://www.hzdr.de/publications/Publ-5299
Publ.-Id: 5299


Structure of uranium sorption complexes at monmorillonite edge sites

Hennig, C.; Reich, T.; Dähn, R.; Scheidegger, A. M.;
Extended X-ray absorption fine structure (EXAFS) spectroscopy at the uranium LIII-edge was used for determining the structural environment of aqueous uranyl surbed onto montmorillonite. The study reveals that uranyl uptake at pH~5-~7 and at an initial uranyl concentration of 5x10-5M takes place at amphoteric surface hydroxyl sites as inner-sphere complex. The measured bond distances sites between uranium and the equatorial oxygen atoms are in the range of 2.34 A the presence of a U-Al backscattering pair was determined. This backscattering pair indicates that the binding of the uranyl unit to amphoteric surface hydroxyl sites occurs preferred as a bidentate inner-sphere complex on aluminol groups.
  • Contribution to external collection
    Radiochim. Acta 90, 653-657 (2002), Oldenburg Wissenschaftsverlag, München

Permalink: https://www.hzdr.de/publications/Publ-5297
Publ.-Id: 5297


Nichtlineare Suszeptibilität von GaAs im THz Frequenzbereich

Dekorsy, T.; Yakovlev, V. A.; Keilmann, F.; Seidel, W.; Helm, M.;
Die nichtlineare Optik im THz Frequenzbereich ist weitgehend unerforscht [1], da hier keine abstimmbaren, intensiven Lichtquellen zur Verfügung stehen. Abstimmbare Freie-Elektronen Laser mit Emissionsfrequenzen im THz Bereich schließen diese Lücke. Wir haben Frequenzverdoppelung unterhalb der optischen Phononresonanz an dünnen GaAs Kristallen mit dem Freie-Elektronen Laser FELIX, Niederlande, durchfgeführt. Erstmals beobachten wir ein Maximum der nichtlinearen Suszeptibilität 2.Ordnung bei der halben Phononfrequenz (4,4 THz) und ein Minimum oberhalb dieser Frequenz (5,3 THz). Dieses Minimum basiert auf einem Vorzeichenwechsel der nichtlinearen Suszeptibilität bedingt durch konkurrierende elektronische und Gitterbeiträge. Ein Vergleich mit Berechnungen [2] zeigt, dass aus der Frequenz dieses Minimums die Beiträge höherer Ordnung des Gitterpotentials zur nichtlinearen Suszeptibilität quantitativ bestimmt werden können [3].

[1] siehe z.B. F. Keilmann, Infr. Phys. 31, 373 (1991).
[2] C. Flytzanis, Phys. Rev. B 6, 1264 (1972).
[3] T. Dekorsy et al. akzepziert zu Phys. Rev. Lett.
Keywords: nonlinear optics, THz, second harmonic generation, phonon-polariton, GaAs
  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Dresden, 24.-28.3.2003

Permalink: https://www.hzdr.de/publications/Publ-5296
Publ.-Id: 5296


Focused ion beams from alloy liquid metal ion sources

Bischoff, L.;
An overview of the research activities of the FIB group in the Research Centre
Rossendorf is given. More in detail the fabrication technology of alloy LMIS as well
as their characterization is discussed. The FIB system IMSA-100 is briefly
introduced and typical applications are presented: writing implantation of Co ions
into a heated Si target in order to create maskless sub-micron CoSi2 structures,
bombardment of semiconductor materials with different ions in a wide range of
current density, dose and temperature allows to study the damage creation and
dynamic annealing process.
Keywords: alloy LMIS, FIB system IMSA-100, sub-micron CoSi2 structures,dynamic annealing
  • Lecture (others)
    Seminar, Institute of Solid State Physics and Institute of Electronics, Sofia April 19, 2002

Permalink: https://www.hzdr.de/publications/Publ-5295
Publ.-Id: 5295


Epitaxial erbium silicide on Ge+ implanted silicon

Travlos, A.; Boukos, N.; Apostolopoulos, G.; Aidinis, C. J.; Bischoff, L.;

Erbium silicide layers were grown epitaxially on Ge+ ion implanted Si. Epitaxy of ErSi2-x layers was achieved at temperature of 750 C.The layers are grown in the tetragonal phase.The growth of the silicide layers resulted in a drastic decrease of the dislocations in the SiGe layer accompanied by the accumulation of defects at the SiGe/ErSi2-x interface.A small redistribution of the Ge in the SiGe layer was also observed.
Keywords: Erbium silicide, Ge+ implantation, SiGe layer
  • Nuclear Instruments and Methods in Physics Research B 196 (2002) 174 - 179

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Permalink: https://www.hzdr.de/publications/Publ-5294
Publ.-Id: 5294


Solidified liquid metal ion sources - formation of a nanoemitter

Knapp, W.; Bischoff, L.; Teichert, J.;
Solidified liquid metal ion sources (LMISs) operating with Au alloy wetted hair-pin emitters can be used as high-intensity electron point sources with nanometer dimension for electron field emission application. A nanoemitter tip on a solidified LMIS emitter can be formed by quenching during ion emission mode. I-V characteristics and the performance of the electron emitting LMIS are presented.
Keywords: liquid metal ion source, electron emitter, quenching, charcteristics
  • Vacuum 69 (2003) 345 - 349

Permalink: https://www.hzdr.de/publications/Publ-5293
Publ.-Id: 5293


Romanian ancient gold objects studies using nuclear methods

Constantinescu, B.; Cojocaru, V.; Bugoi, R.; Grambole, D.; Herrmann, F.;
The study of trace-elements in archaeological metallic objects can provide important clues about the metal provenance and the involved manufacturing procedures, leading to important conclusions regarding the commercial, cultural and religious exchanges between the antique populations.
Ancient metallic materials are usually inhomogeneous on a scale of 20 microns or less: they contain remains of imperfect smelting, segregated phases in alloys, inclusions.
Due to their exceptional chemical stability, gold artefacts remain essentially unchanged during weathering and aging processes.
Several fragments of ancient gold objects coming from an Eneolithical treasury and from Pietroasa "Closca cu Puii Aur" ("The Golden Brood Hen with ITS Chickens") hoard, unearthed on Romanian territory and two Romanian native gold nuggets samples were analysed using micro-PIXE technique at the Rossendorf TANDETRON microbeam facility.
The purpose of the study was to clarify the metal provenance, establishing if the hypothesis of local gold holds. To reach this goal, trace elements (Cu, Te, Sn, Pb, Hg, As, Zr, Sb) and PEG (Platinum Group Elements) concentrations were determined.
The presence of inclusions (micrometeric size areas of compositions different from surroundings) was also checked. We found some Si, Ca, Fe ones on two Eneolithic samples, and a Ta-Cr one on sample from Pietroasa hoard. The measurements led to conclusions regarding the alluvial origin of the gold for the Eneolithical samples and gave some indications for the possible gold ore sources of Pietroasa treasury, confirming the heterogeneity of this treasury (the two analysed pieces belonged to different stylistic and compositional groups).
21 pieces of gold coins of KOSON type, considered the only kind of gold coins issued by the Daciens, were analysed using EDXRF and PAA (Proton Activation Analysis) methods at Bucharest Institute of Atomic Physics facilities. For EDXRF, three annular excitations sources - Pu 238 (30 mCi), Am 241 (50 mCi) and Am 241 (10 mCi, with nickel window for asorption of soft X-rays) and two X-ray detectors with Be window - a Si(Li) and an HPGe were used. For PAA, each coin was irradiated in vacuum for 5 hours at an incident proton energy of 11 MeV at a current of ca. 50 nA at the 8 MV FN High Voltage Bucharest Tandem and measured using a properly protected Ge(Li) gamma spectrometer. Three groups of coins of different compositions were found, corresponding to simple, complex and no monogram pieces. The gold of Koson coins is not a natural one (electrum) from present Romania's territory, but is similar to the gold of pseudo - Lysimachan staters. Some possible historical conclusions are discussed.
  • Lecture (Conference)
    1st International Symposium on Ancient Gold Technology: America and Europe, 23-25 Oct. 2002 Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-5291
Publ.-Id: 5291


Effect of the fluid convection driven by a rotating magnetic field on the solidification of a PbSn alloy

Willers, B.; Eckert, S.; Michel, U.; Zouhar, G.;
It is already known that the microstructure of a metallic alloy can be affected in a significant way due to the convection in the liquid phase during solidification. A time varying magnetic field can be applied to produce a flow field in the melt which influences the nucleation and growth processes. The aim of our research program is to find a strategy to refine the microstructure of castings by an optimal combination of magnetic field intensity, field frequency and cooling rate. Furthermore, the basic mechanisms controlling the solidification by magnetic fields are investigated.
A cylindrical crucible with a diameter of 50 mm was used to contain the Pb85wt%Sn alloy. A melt height of 60 mm was chosen. The container bottom is positioned on a water cooled copper chill allowing a directed solidification by a vertical heat flux. A rotating magnetic field was generated by an inductor system with 6 coils.
Local temperatures were determined during the solidification process using a set of thermocouples. Cooling curves measured at different locations inside the sample reveal the significant influence of the electromagnetic convection on the local heat transfer. Profiles of the melt velocity were obtained applying the ultrasonic Doppler method..
The Pb-85wt%Sn alloy shows a microstructure with primary tin-crystallites and eutectic. Specimens solidified without a rotating magnetic field showed a columnar dendritic microstructure which is orientated in heat flux direction. The tin crystallites and the eutectic are homogeneously distributed over the whole sample. If the alloy solidifies in a rotating magnetic field the microstructure changes. The shape of the dendrites changes from columnar to equiaxed in direction from the bottom to the top of the specimen and in the same direction the volume content of the eutectic increases.

Keywords: solidification, dendritic growth, convection, rotating magnetic field
  • Lecture (Conference)
    EUROMAT 2003, Lausanne, 01.-05.09.2003
  • Contribution to external collection
    Dieter M. Herlach: Solidification and Crystallization, Weinheim: WILEY-VCH, 2004, 3-527-31011-8, 194-203

Permalink: https://www.hzdr.de/publications/Publ-5290
Publ.-Id: 5290


Effect of Fe and Ni ion implantation on the magnetoresistance of La(0.7)Sr(0.3)MnO(3)

Vlakhov, E. S.; Wieser, E.; Nenkov, K. A.; Groetzschel, R.;
By low dose ion implantation the magnetoresistance of LSMO is enhanced and the temperature of its maximum is shifted to lower values. At implantation of higher doses the LSMO films become semiconducting.
  • Lecture (Conference)
    European Conference Physics of Magnetism ' 02, Poznan, Poland, July 1-5, 2002
  • phys. stat. sol. (a) 196 (2003) 125-128

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Permalink: https://www.hzdr.de/publications/Publ-5289
Publ.-Id: 5289


Investigation of the effect of irradiation with gaseous and metallic ions on the atomic structure of the alloy Fe+15 at.% Cr

Ovchinnikov, V. V.; Goloborodski, B. Y.; Gushchina, N. V.; Chemerinskaya, L. S.; Semionkin, V. A.; Wieser, E.; Möller, W.;
In the metastable solid solution Fe-15at.%Cr short range ordering (decomposition) was caused by irradiation at 723 K using Ar and Fe ions. The short range order parameter was evaluated from Moessbauer spectra. The short range order caused by the irradiation is much higher compared to the effect of only annealing at723 K for the same time without irradiation. The decomposition is not limited to the penetration depth of the ions but extends over the whole sample thickness of 30 µm. Therefore it is explained as due to radiation dynamic long range effects.
  • Lecture (Conference)
    III International Scientific Conference "Radiation Thermal Effects and Processing in Inorganic Materials", Tomsk, Russia, July 29 - August 03, 2002

Permalink: https://www.hzdr.de/publications/Publ-5288
Publ.-Id: 5288


Complex Formation between Uranium(VI) and alpha-D-Glucose 1-phosphate

Koban, A.; Geipel, G.; Bernhard, G.;
The complex formation of uranium(VI) with alpha-D-glucose 1-phosphate (C6H11O6PO32-, G1P) was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at pH 4 and potentiometric titration in the pH range from 3 to 10. Both measurements show the formation of a 1:1 complex at lower pH values. The formation constant of UO2(C6H11O6PO3) was calculated from TRLFS measurements to be log beta11 = 5.72 ± 0.12, and from potentiometric titration log beta11 = 5.40 ± 0.25, respectively.
It was found by potentiometric titration that at higher pH values the complexation changes to a 1:2 complex. The stability constant for this complex was calculated to be log beta12 = 8.96 ± 0.18.

Keywords: Uranium, glucose 1-phosphate, complex formation, potentiometric titration, time-resolved laser-induced fluorescence spectroscopy
  • Radiochimica Acta 91 (2003) 393-396

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Permalink: https://www.hzdr.de/publications/Publ-5287
Publ.-Id: 5287


Migration Case Study: Uranium Mining Waste Rock Pile No. 250 in the Region Schlema/Alberoda (Saxony, Germany)

Schmeide, K.; Geipel, G.; Heise, K. H.; Bernhard, G.;
The overall objective of the EC project "Humic Substances in Performance Assessment of Nuclear Waste Disposal: Actinide and Iodine Migration in the Far-Field" is the determination of the effect of humic substances on the actinide migration in natural systems to assess their impact on the long-term safety of radioactive waste repository sites and abandoned uranium mines. This task includes also the implementation of the present knowledge to real existing natural systems thereby verifying the correlation between important parameters, evaluating their environmental impact and finally, uncovering issues not addressed so far.
Uranium mining waste rock piles in the southern parts of the former East Germany represent a significant long-term environmental concern and liability. Although the uranium mines were decommissioned with the end of the uranium ore production in 1990, the legacy of forty-five years of uranium mining, such as abandoned mines, huge waste rock piles and mill tailings, represents a permanent reservoir and source of radioactive and non-radioactive contaminants. The discharge of radionuclides from the waste rock piles and contamination of the surrounding geosphere has to be minimized.
For the case study presented in this paper, the uranium mining waste rock pile no. 250 in Schlema/Alberoda (Saxony, Germany) was chosen. In many respects, this pile resembles other rock piles of this region. The site is characterized comprehensively with regard to composition and activity inventory of rock material and seepage water, uranium species occurring in the seepage water, TOC content and much more. Some important data of other uranium mining waste rock piles that were located in the vicinity of the rock pile no. 250 are also included in this study, especially the fulvic and humic acid content in the seepage water of rock piles and their loading with uranium. The data presented in this natural system study constitute the basis of performance assessment modeling.
Keywords: Transport, Fulvic acid, Humic acid, Uranium, Mine pile
  • Contribution to external collection
    FZKA 6800, Wissenschaftliche Berichte, Forschungszentrum Karlsruhe, Karlsruhe 2003, pp. 79-98.

Permalink: https://www.hzdr.de/publications/Publ-5286
Publ.-Id: 5286


Range distributions of low-energy carbon ions: a base for subplantation growth models

Neumaier, P.; Dollinger, G.; Bergmaier, A.; Eckstein, W.; Fischer, R.; Görgens, L.; Hofsäss, H.; Jäger, H. U.; Kröger, H.; Ronning, C.;
Range distributions of carbon ions deposited onto tetrahedral amorphous carbon films at kinetic energies between 22 eV and 692 eV are measured utilizing high-resolution elastic recoil detection. These data are compared to range calculations based on binary collision approximation as well as to classical molecular dynamics simulations. Asymmetric range profiles, differences in mean ion ranges and increased range straggling compared to theories are attributed due to self diffusion during thermal spike as well as to intrinsic surface properties of the carbon samples which have to be considered in subplantation growth models.
  • Lecture (Conference)
    Frühjahrstagung des Arbeitskreises Festkörperphysik der Deutschen Physikalischen Gesellschaft (Fachverband Dünne Schichten, Vortrag DS 12.2), 23.-28. März 2003, Dresden

Permalink: https://www.hzdr.de/publications/Publ-5285
Publ.-Id: 5285


Project-Group ESRF-Beamline (ROBL-CRG), Bi-Annual Report 2001/2002, Wissenschaftlich-Technische Berichte

Schell, N.; (Editor)
The third report from the Project-Group ESRF-Beamline of the Forschungszentrum Rossendorf covers the period from January 2001 until December 2002. The Rossendorf BeamLine (ROBL) at the European Synchrotron Radiation Facility (ESRF) in Grenoble performed again well during this time - although we had major staff fluctuations, including two times a change in the project-management: Dr. W. Matz became head of the Technical Infrastructure at FZR, and Dr. T. Reich had been offered a professorship at the University of Mainz. We congratulate both of them. In the beamtime used by the FZR and collaborating institutes 77 different experiments were scheduled, while in the ESRF scheduled beamtime 21 experiments were performed by external groups. Additionally, a distinct amount of beamtime was devoted to commissioning of new equipment.

The report is organised in three main parts. The first part contains extendet contributions on results obtaines at ROBL. The second part gives an overview about the general experimental possibilities, scheduled experiments, publications, guests having visited ROBL with support of the EC, an staff information. Finally, the third part collects the experimental reports of the user groups received.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-364 Januar 2003

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Permalink: https://www.hzdr.de/publications/Publ-5284
Publ.-Id: 5284


Growth mode and texture development in TiN films during magnetron sputtering – an in situ synchrotron radiation study

Schell, N.; Bottiger, J.; Matz, W.; Chevallier, J.;
For the materials research experimental station of the Rossendorf beamline ROBL at the European Synchrotron Radiation Facility in Grenoble, France, a two magnetron sputter deposition chamber for in situ study of film growth by synchrotron X-ray diffraction and reflectivity was developed. It allows high-quality depositions of compound films and multilayers. Heteroepitaxial layer-by-layer growth of TiN on single crystal MgO(0 0 1) was observed by real-time specular X-ray reflectivity showing characteristic oscillations. The pseudomorphic growth was confirmed by high-resolution TEM micrographs. During growth on amorphous SiO2 on Si(0 0 1) substrates, the microstructural development of TiN films was studied in situ as a function of film thickness. With the deposition parameters chosen, a crossover was observed: grains with a (0 0 2) plane parallel to the film surface dominate at small thicknesses, while, at larger thicknesses, (1 1 1) grains dominate. Recrystallisation was identified as a mechanism that controls this texture development.
Keywords: Thin films; Magnetron sputtering; In situ X-ray scattering; TiN
  • Nucl. Instr. & Meth. B 199 (2003) 133-138

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Publ.-Id: 5283


Short-wavelength intersubband transitions in InGaAs/AlAs quantum well

Georgiev, N.; Semtsiv, M.; Dekorsy, T.; Eichhorn, F.; Bauer, A.; Helm, M.; Masselink, W. T.;
InGaAs/AlAs quantum wells (QWs) have the potential for the development of new devices based on intersubband transitions, such as near-infrared detectors, ultra-fast switches and light emitters that operate at the communication wavelength of 1.55 mm.However, the increased strain accommodation in the InGaAs/AlAs system considerably affects the band offsets of these QW structures and the performance of the appropriate devices. We report structural and optical characterization of InxGa1-xAs/AlAs/InyAl1-yAs (x ~ 0.7, y ~ 0.55) QW structures grown on InP substrates. In these structures, we utilize the high conduction band offset provided by AlAs. An increased In content in the wells and in the InyAl1-yAs layers helps to compensate the large AlAs tensile strain. Additionally, the smaller InGaAs band gap results in a shift of the first G-like well subband to lower energies relative to the X-minimum in the barrier layers even in very narrow wells. Intersubband absorption at wavelengths shorter than 2.0 mm is observed in thin single QWs. Also presented are spectra of asymmetric coupled QWs and short-period superlattices.
Keywords: quantum well, strain structures, intersubband transitions
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft (DPG) - Tagung, Fachverband Halbleiterphysik, HL3.3, Dresden, 2003

Permalink: https://www.hzdr.de/publications/Publ-5282
Publ.-Id: 5282


Mechanism of degradation of surface hardening at elevated temperature in TiAlV-alloys by in situ synchrotron radiation diffraction

Berberich, F.; Matz, W.; Kreißig, U.; Schell, N.; Mücklich, A.;
The surface hardness of the technically important alloy Ti–6Al–4V (wt.%) can be improved by nitrogen implantation. The structural mechanisms of hardening and of the stability of the improved hardness at elevated temperatures are studied. Ion implanted (II) and plasma immersion ion implanted (PII) samples were used. The formation of small TiN crystallites was detected in the as-implanted state, but only for the II samples a considerable surface hardness increase (factor 3) is observed. The in situ XRD experiments showed, that the TiN phase is stable up to temperatures of 650 °C for both types of implantation. At higher temperature Ti2N is formed which is stable up to 770 °C. ERDA results indicate a diffusion of nitrogen into the bulk material. The redistribution of N is responsible for the hardness changes: a slight decrease for II samples but an improvement by a factor of 2.5 for PII samples. The improvements/degradations of hardness and wear are discussed in correlation with the nitrogen depth distribution below the surface.
Keywords: Synchrotron radiation; Ion implantation; Hardening; Ti–6Al–4V
  • Nuclear Instruments & Methods B 199 (2003) 54-58

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Permalink: https://www.hzdr.de/publications/Publ-5281
Publ.-Id: 5281


Development of nanosystems in TiO2 by ion implantation

Fromknecht, R.; Wang, L. M.; Zhu, S.; Sun, K.; van Veen, A.; van Huis, M. A.; Weimann, T.; Wang, J.; Niemeyer, J.; Eichhorn, F.; Wang, T.;
Au-ions were implanted into TiO2 single crystals with doses ranging from 2x1016Au+/cm2 to 6x1016Au+/cm2 at RT and 1000 K. At RT implanted samples were then thermally annealed at temperatures of 550 K to 1550 K. The Au-atoms precipitate to nanocrystals already during implantation at RT with an average particle size of 1.5 nm. HRTEM investigations revealed that the Au-nanocrystals, embedded in amorphous TiO2 regions, have a broad size and range distribution varying from large sizes in the near surface region to smaller sizes at larger depths. In the annealing process a reorientation of the Au-nanocrystals is observed, with the main effect of a decrease of the (111) peak and an increase of the (200)-peak in the XRD spectra. After annealing at 1000 K the particle size of the highly textured Au-implant was evaluated to ~ 6 nm; this means that during annealing the particles grow, leading to a partially coherent orientation in the disordered TiO2-matrix. Au implantation at RT performed through a metal mask with holes resulted in a narrow size distribution (2-6 nm) of the Au-nanocrystals in the near surface region.
Keywords: Au nanocrystals, ion implantation, rutile, x-ray diffraction
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft, Frühjahrstagung des Arbeitskreises Festkörperphysik, Dresden, 24.-28.3.2003

Permalink: https://www.hzdr.de/publications/Publ-5280
Publ.-Id: 5280


Cu gettering in ion implanted and annealed silicon in regions before and beyond the main projected ion range

Kögler, R.; Peeva, A.; Lebedev, A.; Posselt, M.; Skorupa, W.; Özelt, G.; Hutter, H.; Behar, M.;
The strong gettering of Cu atoms in single-crystal Si implanted with 3.5 MeV P+ ions was studied after thermal treatment and contamination with low amount of Cu impurity. Cu decorates the remaining damage generated by ion implantation. Three separate Cu gettering layers were detected by secondary ion mass spectrometry: at the main projected ion range, RP, below RP (RP/2 effect) and beyond RP (trans-RP effect). The defects acting as gettering centers at RP/2 and RP are implantation induced excess vacancies and excess interstitials, respectively. Cu profiles fit very well with depth distributions of excess vacancies and excess interstitials simulated by binary collision model for random and channeled ion incidence. The RP/2 and RP gettering layer are implantation induced, whereas the trans-RP gettering layer is formed by thermal treatment. The Cu accumulation in the trans-RP region increases with increasing temperature and/or with increasing annealing time. The RP/2 effect for P+ implantation was found to be significantly reduced in comparison with Si+ implantation. It completely disappears for higher P+ ion fluences. The obtained results are in agreement with the assumption that interstitials carried by P diffusion are the origin of Cu gettering in the trans-RP region.
Keywords: Ion implantation (61.72.Q), Defect formation and annealing (61.72.C), Indirect evidence of defects (61.72.H), Defect diffusion (66.30.L),Cu gettering (61.72.T).

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Permalink: https://www.hzdr.de/publications/Publ-5279
Publ.-Id: 5279


Atomistic simulation of ion-beam-induced defect production within 100 – 1000 ps after ion impact

Posselt, M.;
The formation and evolution of radiation damage by ion bombardment consists of three stages: (i) atomic displacements during ballistic processes, (ii) formation of a (meta)stable defect structure after fast relaxation, and (iii) long-term thermally activated defect rearrangement, migration, recombination and reduction. The first two stages occur on very short time scales and are hardly accessible by available experimental methods. Atomistic computer simulations can contribute to a better understanding of these processes and of their microscopic mechanisms.
In this talk, a combined simulation method is employed to study a relatively simple case, the defect production by a single ion impact in silicon. Processes in the collision cascade with energy transfers above about 100 eV are treated by computer simulations based on the binary collision approximation (BCA). Classical molecular dynamics (MD) calculations are applied to consider processes in certain parts of the cascade which start with energy transfers less than about 100 eV. Detailed investigations are performed to study the temporal evolution of the defect structure until the beginning of the thermally activated phase, and to determine the damage morphology obtained after the fast relaxation. The influence of nuclear energy deposition and target temperature is discussed. The combination of BCA and MD methods allows the effective calculation of the total number and the depth distribution of different defect species (isolated vacancies and self-intersitials as well as more complex defects) formed on average per incident ion after the fast relaxation processes are finished. The procedure yields more realistic initial conditions for the simulation of post-implantation annealing than hitherto used.




Keywords: computer simulation, defect formation, ion implantation
  • Invited lecture (Conferences)
    20th Int. Conf. on Atomic Collisions in Solids (ICACS 20), Puri, India, Jan. 19-24, 2003 (invited talk)

Permalink: https://www.hzdr.de/publications/Publ-5278
Publ.-Id: 5278


Betriebserfahrungen beim Batch-Monitoring mit adaptiven Stoff- und Wärmebilanzen

Hessel, G.; Heidrich, J.; Hilpert, R.; Roth, M.; Schmitt, W.; Seiler, T.; Weiß, F.-P.;
In der Feinchemie- und Pharmaindustrie werden Chemikalien kleinerer Menge meistens durch diskontinuierlich geführte Batch-Prozesse hergestellt. Zur Unterstützung des Bedienungspersonals bei der schwierigen Prozessführung von Batch-Reaktoren (Rührkesselreaktoren) wurde ein Online-Monitoring-System (MoSys) entwickelt, das auf adaptiven Stoff- und Wärmebilanzen basiert. Die Industrieerprobung erfolgte im Rahmen eines entwickelten Batch-Informations-Management-Systems (BIMS), das in einem separaten Industrie-PC implementiert und über den Terminalbus in die vorhandene Automatisierungstechnik einer Mehrzweckanlage der Degussa AG eingebunden wurde. Die Betriebserfahrungen von zwei Produktionskampagnen zeigten, dass das BIMS/MoSys stabil und zuverlässig arbeitete und die Konzentrationsprofile gut mit den erwarteten Konzentrationsverläufen übereinstimmten.

Mit BIMS/MoSys sind folgende praktische Nutzanwendungen möglich:

- Einsparung einer chemischen Online-Prozessanalytik,
- Erweiterung und Archivierung des bestehenden Prozesswissens,
- Verbesserung der Produktqualität bei komplexen Batch-Prozessen,
- Optimierung der Prozessführung durch die genauere Ermittlung von Anlagen- und Prozess- Kenngrößen,
- Fehler- und Ursachenanalyse anhand der archivierten Batches,
- Rückverfolgbarkeit von Batches bei Problemen (z. B. Qualitätsbeanstandungen),
- Aufbau eines automatisierten Batch-Reports.

Darüber hinaus können unerwünschte Betriebszustände mit erhöhter Zwischenproduktakkumulation und verringerter Raum-Zeit-Ausbeute frühzeitig erkannt und dadurch rechtzeitig Gegenmaßnahmen eingeleitet werden, um größere Verluste zu vermeiden. Das auf adaptiven Stoff- und Wärmebilanzen basierende Online-Monitoring-System ist bei allen ausreichend exothermen ( oder endothermen) Semibatch-Prozessen einsetzbar, wenn geeignete Informationen in den Stoff- und Wärmebilanzen enthalten sind.
  • Abstract in refereed journal
    Chemie Ingenieur Technik, (75), 8 (2003) 1141

Permalink: https://www.hzdr.de/publications/Publ-5277
Publ.-Id: 5277


INTERACTION OF URANIUM WITH Desulfovibrio äspöensis (DSM 10631T)

Moll, H.; Merroun, M.; Selenska-Pobell, S.; Bernhard, G.;
The FZR/IRC contributions are focussing on the interactions of actinides with indigenous bacteria in Äspö aquifer. We presenting the first results on interactions of the sulfate-reducing bacterium D. äspöensis (DSM 10631T) with uranium(VI). 80 % of the U(VI), solved initially in a concentration of 0.02 mM in a liquid medium supplemented with lactat (10 mM), was removed by the cells of this strain after 72 h of incubation at pH 5.
Keywords: uranium, desulfovibrio, reduction
  • Other report
    Äspö HRL Annual Report 2002 (2003)

Permalink: https://www.hzdr.de/publications/Publ-5276
Publ.-Id: 5276


Einführung von Facility Management in einer Forschungseinrichtung, Anforderungen, Probleme, Erfahrungen

Joehnk, P.; Keywords: Facility Management, Forschungseinrichtung
  • Lecture (others)
    Workshop Fa. Heinrich Nickel GmbH am 16.01.2003 in Berlin

Permalink: https://www.hzdr.de/publications/Publ-5274
Publ.-Id: 5274


New possibilities of characterizing growing sputter-deposited thin films

Schell, N.; Bottiger, J.; Matz, W.; Chevallier, J.; Petersen, J.; Andreasen, K. P.; Jensen, T.;
wird nachgereicht
  • Contribution to proceedings
    Proceedings of 9th Annual International Conference on Composite Engineering (ICCE/9), San Diego, USA, July 1-6, 2002, ed. Hui, D., p. 697-698

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Permalink: https://www.hzdr.de/publications/Publ-5272
Publ.-Id: 5272


Institute of Ion Beam Physics and Materials Research: Annual Report 2002

von Borany, J.; Helm, M.; Jäger, H.-U.; Möller, W.; Wieser, E.; (Editors)
Summary of the scientific activities of the institute in 2002 including selected highlight reports, short research contributions and an extended statistics overview.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-362 Januar 2003

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Permalink: https://www.hzdr.de/publications/Publ-5271
Publ.-Id: 5271


Influence of annealing on structural properties of metallic multilayers

Hecker, M.; van Loyen, L.; Tietjen, D.; Schell, N.; Schneider, C. M.;
wird nachgereicht
  • Materials Science Forum 378-381 (2001) 370-375

Permalink: https://www.hzdr.de/publications/Publ-5270
Publ.-Id: 5270


Thermal stability of grain structure and defects in submicrocrystalline and nanocrystalline nickel

Klemm, R.; Thiele, E.; Holste, C.; Eckert, J.; Schell, N.;
The grain and defect structure of submicrocrystalline and nanocrystalline nickel produced by equichannel angular pressing or by ball milling, respectively, has been studied by isochronal and isothermal annealing experiments, and Xray investigations. A detailed analysis of the thermal stability of the di.erent types of microstructures will be presented.
  • Scripta Materialica 46 (2002) 685-690

Permalink: https://www.hzdr.de/publications/Publ-5269
Publ.-Id: 5269


Internal strains in single grains of fatigued polycrystalline nickel

Thiele, E.; Bretschneider, J.; Buque, C.; Schell, N.; Schwab, A.; Holste, C.;
Bragg diffraction profiles were measured on single grains of different axial orientation in cyclically deformed Ni polycrystals. Diffraction profile parameters were determined and compared with results from profile measurements on fatigued single crystals, showing the same type of dislocation structure as the grains with corresponding axial orientation. Conclusions are drawn concerning the deformation processes in the grains taking into account the activated slip systems, the dislocation density and long-range residual strains.
  • Materials Science Forum 404-407 (2002) 823-828

Permalink: https://www.hzdr.de/publications/Publ-5268
Publ.-Id: 5268


Ion beam synthesized nanoclusters for silicon-based light emission

Rebohle, L.; von Borany, J.; Fröb, H.; Gebel, T.; Helm, M.; Skorupa, W.;
Strong blue and violet photoluminescence (PL) and electroluminescence (EL) at room temperature has been achieved from thin SiO2 layers implanted with group IV elements. Thermally grown SiO2 .lms with thicknesses between 130 and 500 nm were implanted with Si, Ge or Sn ions followed by di.erent annealing procedures. Based on PL and PL excitation spectra we tentatively interpret the blue–violet PL as due to a T1- S0 transition of an oxygen deficiency center. The strong EL is well visible with the naked eye and reaches a power e.ciency of up to 5E-3 for Ge. Whereas the EL intensity shows a linear dependence on the injection current for Ge-rich layers, the shape of the EL spectrum remains unchanged. It was found that the I–V characteristics shift to lower applied electric fields with increasing implantation
fuence. Furthermore, it is assumed that the luminescence centers will be excited either by field ionization or by the scattering of hot electrons. Finally, the suitability of ion implanted silicon dioxide layers for optoelectronic applications is discussed.
Keywords: Si, Ge, Sn implanted SiO2; Photoluminescence; Optoelectronic application
  • Nuclear Instruments and Methods in Physics Research B 188 (2002) 28–35

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Permalink: https://www.hzdr.de/publications/Publ-5267
Publ.-Id: 5267


In situ high-temperature synchrotron-radiation diffraction studies of Ni and Co–Ni silicidation processes

Rinderknecht, J.; Prinz, H.; Kammler, T.; Berberich, F.; Zschech, E.;
Silicidation processes in nanoscale Ni and CoNi (5at.% Ni) layers on different silicon substrates were investigated using X-ray diffraction. The phase formation sequences as well as the formation and transition temperatures between 200 and 750°C were studied. The impact of different silicon substrates, i.e., polycrystalline Si and (100) oriented Si single-crystal substrates as well as the impact of different species of dopants (As, P) were analysed. The thermal range of the desired low resistance target phases NiSi and Co(0.95)Ni(0.05)Si(2) was determined. The temperatures for phase formation and phase transitions are significantly lowered on polycrystalline Silicon substrates.
Keywords: Ni silicide; Co–Ni silicides; Phase formation, transition temperatures; Impact of dopants, substrate
  • Microelectronic Engineering 64 (2002) 143-149

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Permalink: https://www.hzdr.de/publications/Publ-5266
Publ.-Id: 5266


Plasma immersion ion implantation of nitrogen in Si: Formation of SiO2, Si3N4 and stressed layers under thermal and sputtering effects

Ueda, M.; Beloto, A. F.; Reuther, H.; Parascandola, S.;
Plasma immersion ion implantation of nitrogen in Si: Formation of SiO2,
Si3N4 and stressed layers under thermal and sputtering effects
  • Surface and Coatings Technology 136 (2001) 244-248

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Permalink: https://www.hzdr.de/publications/Publ-5265
Publ.-Id: 5265


Sponge-like and columnar porous silicon implanted with nitrogen by plasma immersion ion implantation (PIII)

Beloto, A. F.; Ueda, M.; Abramof, E.; Senna, J. R.; Da Silva, M. D.; Kuranaga, C.; Reuther, H.; Ferreira Da Silva, A.; Pepe, I.;
Sponge-like and columnar porous silicon implanted with nitrogen by plasma immersion ion implantation (PIII)
  • Surface and Coatings Technology 156 (2002) 267 -271

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Permalink: https://www.hzdr.de/publications/Publ-5264
Publ.-Id: 5264


Bacteria-Based Bioceramics for Bioremediation of Uranium Mining Waste Waters

Raff, J.ORC; Soltmann, U.; Matys, S.ORC; Merroun, M.; Roßberg, A.; Hennig, C.; Böttcher, H.; Pompe, W.; Selenska-Pobell, S.
Uranium mining waste piles are an enormous pool for heavy metal resistant bacteria. Many of these bacteria possess different mechanisms to detoxify metals, e.g. bioaccumulation, biotransformation, biomineralization or biosorption. The latter is of special interest for the development of bioremediation processes. We demonstrated that vegetative cells, spores and purified S-layer of Bacillus sphaericus JG-A12 which was recovered from a uranium mining waste pile near the town of Johanngeorgenstadt, Germany, bind selectively U, Cu, Pb, Al and Cd. In this work sol-gel techniques were used to immobilize cells, spores and stabilized S-layer of B. sphaericus JG-A12 in a porous silicate matrix. Processes of sorption and desorption of U and Cu by the produced biological ceramics (biocers) were investigated and compared with the binding properties of the single components. Localization of the bound metals was carried out using scanning electron microscopy and EDX analysis. Formed metal complexes were characterized by extended X-ray absorption fine structure spectroscopy (EXAFS). Our results demonstrate that spores followed by vegetative cells and the S-layer bind large amounts of U and Cu. The silicate matrix binds only small amounts of U and no Cu. The immobilization of the biocomponents in the bioceramics did not have any negative effect on the cells and S-layer but the metal binding capacity of the spores was strongly reduced. Binding capacity and binding kinetics of the biocers were positively influenced by adding water soluble additives as sorbitol or by freeze drying instead of air drying. The bound metals can be completely removed from the biocers by using aqueous citric acid what makes them reusable. EXAFS spectroscopy of the uranium complexes shows that uranium is bound via phosphate and carboxyl groups of the biocomponents as well as by the silicate and hydroxyl groups of the ceramic matrix. Because biocers possess high mechanical stability and metal binding capacity and are in addition reusable they are suitable for construction of intelligent filters for bioremediation.
Keywords: Keywords: Bacillus sphaericus, bioceramic, biosorption
  • Poster
    Abstrakt zur ASM-Jahrestagung (18.-22 Mai 2003), Washington Q10 Bioremediation of Metals and Bioremediation of Metal-Contaminated Soils

Permalink: https://www.hzdr.de/publications/Publ-5263
Publ.-Id: 5263


Hydrogen Embrittlement of Reactor Pressure Vessel Steels

Uhlemann, M.; Müller, G.; Böhmert, J.;
The embrittlement of reactor pressure vessel steels is mainly effected by the neutron field. However, recently results have pointed out an additional or coupled effect of hydrogen. The aim was to investigate the influence of hydrogen on mechanical behaviour of different unirradiated reactor pressure vessel steels up to the working temperature in dependence on cathodic hydrogen charging conditions in correlation to chemical composition, microstructure, and hydrogen diffusivity and solubility. Diffusivity and solubility of hydrogen were determined by means of permeation measurements, thermodesorption measurements, and hot extraction. Small differences are mainly caused by the chemical composition of the steels. Higher copper and phosphorus contents do not yield an expected higher hydrogen uptake of the unirradiated steels. The mechanical properties were determined by slow tensile tests up to 250°C with simultaneously hydrogen charging in simulated reactor pressure water dependent on strain rate and charging conditions, and by impact tensile tests. The results of the mechanical tests and the corresponding fractographic analysis showed hardly an effect of hydrogen and no significant differences of the steels under the applied charging conditions. The loss of ductility decreases with increasing strain rate and increasing temperature. These results are the staring point for further investigations on irradiated samples.
Keywords: diffusivity, hydrogen, embrittlement, mechanical properties, reactor pressure vessel steels, solubility
  • Lecture (Conference)
    EDEM 2003 - International Conference on Environmental Degradation of Engineering Materials, Bordeaux, 29.06-02.07.2003, Vollversion auf CD
  • Contribution to proceedings
    EDEM 2003 - International Conference on Environmental Degradation of Engineering Materials, Bordeaux, 29.06-02.07.2003, Vollversion auf CD

Permalink: https://www.hzdr.de/publications/Publ-5261
Publ.-Id: 5261


Analysis of a hypothetical boron dilution event by means of the neutron kinetic core model DYN3D using different cross section libraries

Kliem, S.; Mittag, S.;
Stationary and transient core calculations for a hypothetical boron dilution event have been carried out by the nodal code DYN3D. Two different two-group diffusion-parameter libraries, generated by the cell codes HELIOS and CASMO, have been used, in order to assess the influence of these data. Realistic core inlet boundary conditions have been applied using a validated semi-analytical coolant mixing model. The initial deborated-coolant-slug volumes, necessary for reaching recriticality in stationary calculations with both data libraries, differ by some 20 %. Differences are also observed in the height and time point of the power peak in transient calculations. The deviations between the applied data libraries are mainly due to different SCRAM reactivities and Doppler coefficients. Even when assuming a 36 m3 deborated slug, the core is brought back to subcriticality in all calculations.
  • Lecture (Conference)
    Fachtag der KTG-Fachgruppen "Betrieb" und "Reaktorphysik und Berechnungsmethoden" 13.-14.02.2003, Rossendorf, Proceedings CD-ROM
  • Contribution to external collection
    Fachtag der KTG-Fachgruppen "Betrieb" und "Reaktorphysik und Berechnungsmethoden" 13.-14.02.2003, Rossendorf, Proceedings CD-ROM

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Permalink: https://www.hzdr.de/publications/Publ-5260
Publ.-Id: 5260


Electron Microscopy and X-ray Diffraction Study of AlN layers

Kowalczyk, A.; Jagoda, A.; Mücklich, A.; Matz, W.; Pawlowska, M.; Ratajczak, R.; Turos, A.;
AlN nanocrystalline layers and superstructures are used in the modern optoelectronic technology as reflecting mirrors in semiconductor lasers. In the present work the properties of AlN films prepared by sputtering methods from an AlN target in reactive Ar + N plasma were investigated. The characterisation was performed with HRTEM, SEM, glancing angle XRD and RBS methods. The present measurements confirmed the polycrystalline structure of AlN layers and enabled the evaluation of their grain size. The roughness and thickness of the layers were additionally determined by ellipsometric and profilometric measurements.
Keywords: Electron microscopy, X-ray diffraction, RBS
  • Acta Physica Polonica A 102 (2002) 221

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Permalink: https://www.hzdr.de/publications/Publ-5259
Publ.-Id: 5259


RBS and ion channelling study of YBCO/STO and YBCO/LSMO/STO structures. Oxygen content estimated by X-ray diffraction

Grigorov, K.; Tsaneva, V.; Spasov, A.; Matz, W.; Groetzschel, R.; Reuther, H.;
The structure and the elemental depth distributions of Y1Ba2Cu3O7-d (YBCO) and La0.7Sr0.3MnO3 (LSMO) were examined by q-2q XRD, and by 1.7 MeV 4He+ Rutherford Backscattering Spectrometry (RBS) in random and channeling geometry. The YBCO layers were magnetron sputtered, where the only one varying parameters were the oxygen pressure and the annealing time. The layers have high crystalline qualitiy and an almost sharp interface with the substrate as revealed by the analysis. It is shown that the oxygen content influences considerably not only the superconducting behavior, but also the lattice parameters and the cmin parameter (the minimum yield which is the ratio of aligned to random Rutherford backscattering spectra). We have found by high-precision RBS simulation, that independent on the film quality, a disordered interface region of 20 to 30 nm is present in all structures. As a complementary study we have performed also AES depth profiling.
Keywords: HTSC, X-ray diffraction, RBS
  • Vacuum, 69 (2002) 315-319

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Publ.-Id: 5257


YBCO/LSMO and LSMO/YBCO double-layer deposition by off-axis magnetron sputtering and strain effects

Donchev, T.; Tsaneva, V.; Nurgaliev, T.; Gravier, L.; Ansermet, J. P.; Petrov, I.; Petrova, V.; Matz, W.; Groetzschel, R.; Pignard, S.; Vincent, H.;
We report here on ferromagnetic/superconductor FM/SC and SC/FM double layers deposited without a buffer layer between FM and SC. Thin films of La0.7Sr0.3MnO3 (LSMO) are used for the FM, and YBa2Cu3O7-x (YBCO) for the SC. Both films can grow crystalline on SrTiO3 (STO) or LaAlO3 (LAO) substrates in high temperature and in oxygen atmosphere conditions. Magnetic and transport measurements and X-ray diffraction analysis are used to characterise film quality and properties. It is shown that off-axis magnetron sputtering can be used for high-quality double layer deposition. A prerequisite for this is the suppression of the interdiffusion process. This is achieved by lowering the deposition temperature and shortening the deposition time for the top layer. Lattice relaxation for LSMO films deposited on LAO substrates is seen. It is demonstrated that post-deposition annealing or additional top layer deposition enlarges the relaxed part of the lower LSMO film. LSMO films are smooth and free of imperfections and the stress is partly relieved by the formation of misfit dislocations. For YBCO films, SEM, XRD, EDX and magnetisation characterisations show that film lattice relaxation starts when single-element-oxide crystals start to grow into the film. Many experiments give evidence of a critical thickness of about 30 nm of a strained layer, after which the top part of the YBCO film relaxes. Despite the small compositional deviation due to the interdiffusion, the YBCO/LSMO double films demonstrate high enough transport and magnetic properties to allow their application in the investigation of the injection of spin-polarised quasiparticles from FM to SC film. The critical current for YBCO film is Jc~0.7×106 A/cm2 if it is a bottom layer, and Jc~1.7×106 A/cm2 if YBCO is a top layer, whilst our optimal single-layer YBCO films have Jc~(2.5¯5)×106 A/cm2 at 77 K.
Keywords: High Tc superconductor; Ferromagnetic film; Strain effects; Film relaxation
  • Vacuum, 69 (2002) 243-247

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Publ.-Id: 5256


Analysis of the Boiling Water Reactor Turbine Trip Benchmark with the Codes DYN3D and ATHLET/DYN3D

Grundmann, U.; Kliem, S.; Rohde, U.;
The OECD/NRC BWR Turbine Trip Benchmark was analysed by the codes DYN3D and the coupled code system ATHLET/DYN3D. Considering the calculations with given thermal-hydraulic boundary conditions of the core for the Exercise 2 of the benchmark the analyses were performed with the core model DYN3D. Concerning the modelling of the BWR core in the DYN3D code several simplifications and their influence on the results were investigated. The standard calculations with DYN3D were performed with 764 coolant channels (1 channel per fuel assembly), the assembly discontinuity factors (ADF) and the phase slip model of MOLOCHNIKOV. Comparisons were performed with the results obtained by calculations with 33 thermal-hydraulic channels, without the ADF and with the slip model of ZUBER-FINDLAY. It is shown that the influence on core-averaged values of the steady state and the transient is small. Considering local parameters the influence of the ADF or the reduced number of coolant channels is not negligible. For the calculations of Exercise 3 the DYN3D-model validated during the Exercise 2 calculations in combination with the ATHLET system model, developed at GRS for Exercise 1 has been used. Calculations were performed for the basic scenario as well as for all specified extreme versions. They were carried out using a modified version of the external coupling of the codes, the ?parallel? coupling. This coupling shows a stable performance at the low time step sizes, which are necessary for an appropriate description of the feedback during the transient. The influence of assumed failures of different relevant safety systems on the plant and the core behaviour was investigated in the calculations of the extreme scenarios. The calculations of Exercise 2 and 3 contribute to the validation of DYN3D and ATHLET/DYN3D for boiling water reactor systems.
Keywords: neutron kinetics thermal hydraulics nuclear reactors boiling water reactors transients turbine trip benchmark measurements three-dimensional slip model
  • Nuclear Science and Engineering 148(2004), 226-234

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Publ.-Id: 5255


The Integral Equation Method for a Steady Kinematic Dynamo Problem

Xu, M.; Stefani, F.; Gerbeth, G.;
With only a few exceptions, the numerical simulation of cosmic and laboratory hydromagnetic dynamos has been carried out in the framework of the differential equation method. However, the integral equation method is known to provide robust and accurate tools for the numerical solution of many problems in other fields of physics. The paper is intended to facilitate the use of integral equation solvers in dynamo theory. In concrete, the integral equation method is employed to solve the eigenvalue problem for a hydromagnetic dynamo model with a spherically symmetric, isotropic helical turbulence parameter alpha. Three examples of the function alpha(r) with steady and oscillatory solutions are considered. A convergence rate proportional to the inverse squared of the number of grid points is achieved. Based on this method, a convergence accelerating strategy is developed and the convergence rate is improved remarkably. Typically, quite accurate results can be obtained with a few tens of grid points.

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Publ.-Id: 5254


The SHIP Experiment at GDT: Physical Concept and Pre-Calculations

Anikeev, A.; Bagryansky, P.; Ivanov, A.; Noack, K.;
At present, the GDT facility of the Budker Institute for Nuclear Physics Novosibirsk is being upgraded. The first stage of the upgrade is the Synthesised Hot Ion Plasmoid (SHIP) experiment. It aims, on the one hand, at the investigation of plasmas the parameters of which are expected to appear in the region of high neutron production in a GDT based fusion neutron source as proposed by the Budker Institute and, on the other hand, at the investigation of plasmas the parameters of which have never been achieved before in magnetic mirrors. The expected record values of plasma parameters and several peculiarities of the plasma offer a great field
for interesting investigations. In order to simulate the particle fields inside the GDT device and later in a GDT based neutron source an Integrated Transport Code System (ITCS) is being developed in collaboration between Forschungszentrum Rossendorf and Budker Institute. It consists of modules which allow the calculations of neutral gas, background plasma and of the fast ion component considering their mutual interactions. This contribution explains the concept of the SHIP experiment and presents the
results of first calculations by means of the ITCS modules.
Keywords: plasma physics, fusion, neutron source, magnetic mirror, gas dynamic trap, GDT facility, numerical calculation
  • Poster
    29th EPS Conference on Plasma Physics and Controlled Fusion, 17-21 June 2002, Montreux, Switzerland, Proceedings: ECA Vol. 26B, P-4.098 (2002)
  • Contribution to proceedings
    29th EPS Conference on Plasma Physics and Controlled Fusion, 17-21 June 2002, Montreux, Switzerland, Proceedings: ECA Vol. 26B, P-4.098 (2002)

Permalink: https://www.hzdr.de/publications/Publ-5253
Publ.-Id: 5253


Thin layer copper ISE for fluidic microsystem

Hüller, J.; Pham, M. T.; Howitz, S.;
A miniaturised ion selective electrode (ISE) for Cu2+ ions was developed, specially designed for application in a microfluidic system. The electrode was prepared on a silicon wafer substrate coated with a Cu deposit in the thickness range of 50 - 200 nm. The Cu layer was quantitatively converted into CuS by treatment in a sulphidic ambient. The chip electrode has a size of 5x5 mm2 and was mounted on a spacer chip coupled to the fluidic microcell using a chip clip technology. The coupling is liquid proof and reversible, permitting an easy exchange of the chip electrodes. The effective electrode area contacting the liquid of the microsystem flow channel amounts to about 4 mm2.

Sensitivity measurements were performed stationary and in the flow through cell. There was found a good Nernstian response of 29 mV/pCu between pCu 5 and 1 agreeing very well with reference measurements carried out with a commercial ISE.

The rapid response observed even in the dilutest solutions used, is related to the thin, non-porous structure of the CuS layer, minimizing diffusion effects during changing the test solutions. The adhesion of the sensitive CuS layer is different for the substrates Si, SiO2 and Si3N4 and depends on their history, roughness and evaporation conditions.
Keywords: micro electrode, ion selective electrode, copper ion sensor, fluidic micro system, solid-state membrane
  • Sensors & Actuators B. 91(2003) 17-20

Permalink: https://www.hzdr.de/publications/Publ-5252
Publ.-Id: 5252


Synthesis of 4-[18F]fluoroiodobenzene and its application in Sonogashira cross-coupling reactions

Wüst, F.; Knieß, T.;
The first application of a Sonogashira cross-coupling reaction in 18F chemistry has been developed. The reaction was exemplified by the cross-coupling of terminal alkynes (ethynylcyclopentyl carbinol 6, 17alpha-ethynyl-3,17beta-estradiol 7 and 17alpha-ethynyl-3-methoxy-3,17beta-estradiol 8) with 4-[18F]fluoroiodobenzene. 4,4'-Diiododiaryliodonium salts were used as precursors for the synthesis of 4-[18F]fluoroiodobenzene, enabling the convenient access to 4-[18F]fluoroiodobenzene in 13-70 % yield using conventional heating or microwave activation. The Sonogashira cross-coupling of 4-[18F]fluoroiodobenzene with terminal alkynes gave the corresponding 4-[18F]fluorophenylethynyl-substituted compounds [18F]-9, [18F]-10 and [18F]-13 in yields up to 88% within 20 min starting from 4-[18F]fluoroiodobenzene.
  • Journal of Labelled Compounds and Radiopharmaceuticals 2003, 46: 699-713
  • Lecture (Conference)
    15th International Symposium on Radiopharmaceutical Chemistry; Sydney, 07.-18.08.2003.

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Publ.-Id: 5251


Efficient synthesis of the 18F-labelled amino acid 3-O-methyl-6-[18F]fluoro-L-DOPA

Füchtner, F.; Steinbach, J.;
The 18F-labelled amino acid derivative 3-O-methyl-6-[18F]fluoro-L-DOPA ([18F]OMFD) is a potential radiotracer to image tumour tissue using positron emission tomography. The precursor N-formyl-3-O-methyl-4-O-boc-6-trimethyl-stannyl-L-DOPA--ethyl ester enables the direct electrophilic radiofluorination by stereoselective destannylation. After partial hydrolysis, an optimized HPLC purification and sterile filtration the [18F]OMFD obtained with high radiochemical purity is ready for use. The total synthesis time is about 50 minutes and the radiochemical yield achieved is 20-25% (decay corrected, related to [18F]F2). It was demonstrated that [18F]OMFD can be produced routinely and reliably for clinical use. [18F]FDOPA - preparation devices can be used with minor modifications.
Keywords: 3-O-methyl-6-[18F]fluoro-L-DOPA, radiolabelled amino acid, electrophilic 18F-fluorination, PET-radiotracer
  • Applied Radiation and Isotopes 58 (2003) 575-578

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Publ.-Id: 5250


Discontinuity factors for non-multiplying material in two-dimensional hexagonal reactor geometry

Mittag, S.; Petkov, P.; Grundmann, U.;
On the basis of methods developed recently for square-fuel-assembly reactor cores, discontinuity factors for hexagonal VVER (Russian PWR) control absorbers and reflector nodes have been derived. Partial currents from heterogeneous multi-group transport calculations are used for the determination of the discontinuity factors. As shown by suitable benchmark calculations, the application of these quantities in the two-group nodal diffusion code DYN3D clearly improves the results of assembly-power predictions. The advantage of reflector diffusion parameters, including discontinuity factors, over conventional albedos has also been demonstrated.
Keywords: albedo, baffle, benchmark problem, boundary condition, control rod, diffusion equation, discontinuity factor, DYN3D, equivalence theory, fine mesh, fuel assembly, heterogeneity, hexagonal geometry, homogenisation, MARIKO, neutron flux, neutron transport, nodal expansion method, non-multiplying material, nuclear reactor core, partial current, power distribution, reflector, PWR, VVER, VVER-440
  • Annals of Nuclear Energy 30/13 (2003) pp. 1347-1364

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Publ.-Id: 5249


Synthetic Humic Acid Model Substances with Specific Functional Properties for the Use in Complexation and Sorption Experiments with Actinides

Sachs, S.; Heise, K.-H.; Bernhard, G.;
In order to improve the knowledge about the interaction processes between humic acids (HA) and metal ions, e.g., actinide ions, various HA model substances with different functional properties were developed at FZR-IfR. These include synthetic HA with different functional group contents and various structural elements, chemically modified HA with blocked phenolic OH groups as well as 14C-labeled HA. Since start of the project, synthetic HA with distinct redox functionalities are developed.
The report gives an overview about the synthesis, characterization and application of HA with various functional properties. It describes the synthesis and characterization of the melanoidin-based HA type M1 and M42, which are characterized by different carboxyl group contents. In addition, the synthesis and characterization of modified HA with blocked phenolic OH groups as well as of HA with distinct redox functionalities are discussed.
Keywords: Humic acids, Model substances, Synthesis, Characterization, Modification, Carbon-14 labeling, Application, Complexation, Migration, Actinides
  • Contribution to external collection
    Humic Substances in Performance Assessment of Nuclear Waste Disposal: Actinide and Iodine Migration in the Far-Field, First Technical Progress Report, Forschungszentrum Karlsruhe, Wissenschaftliche Berichte, FZKA 6800, Karlsruhe 2003, S. 51-64

Permalink: https://www.hzdr.de/publications/Publ-5246
Publ.-Id: 5246


Thermochromatographische Untersuchungen von Actinidenoxiden

Hübener, S.;
Die Flüchtigkeit von Oxiden der leichten Actiniden Th, Pa, U, Np und Pu im System O2-H2O(g)/SiO2(s) wurde mittels Thermochromatographie im Temperaturbereich 300 - 1475 K untersucht. Th und Pa bilden unter den experimentellen Bedingungen keine flüchtigen Verbindungen. Bei Temperaturen > 1250 K bilden U, Np und Pu flüchtige Oxidhydroxide, deren Flüchtigkeit in der Reihenfolge Pu<Np<U zunimmt. Die Flüchtigkeit des Plutoniums belegt die Oxidation von Plutoniumdioxid durch Sauerstoff/Wasser zum Trioxid.
Keywords: Actiniden, Plutoniumoxid, Thermochromatographie
  • Lecture (others)
    Seminar des Labors für Radio- und Umweltchemie der Universität Bern und des PSI, 24.01.2003, Universität Bern

Permalink: https://www.hzdr.de/publications/Publ-5245
Publ.-Id: 5245


Drug release from polyureaurethane coating modified by plasma immersion ion implantation

Kondyurin, A. V.; Maitz, M. F.; Romanova, V. A.; Begishev, V. P.; Kondyurina, I. V.; Guenzel, R.;
A crosslinked polyurethanurea (PUU) coating was synthesised from a solution on metal vascular stents. In the model system the glucocorticoid prednisolone was inserted into the film by the equilibrium swelling method; after this plasma immersion ion implantation (PIII) was applied to modify the coating for improved release kinetics. This treatment causes the formation of oxygencontaining and unsaturated carbon–carbon groups in the PUU and a destruction of the drug in the surface layer. As a consequence, the release rate of prednisolone to water becomes more stable with time than it is at the untreated coating. In this drug release system PIII treatment prevents an initial toxically high release of the drug. By this it allows the incorporation of a higher amount of the drug and an extended action.
Keywords: stent, polyurethane, drug release, plasma, ion implantation, PIII
  • Journal of Biomaterials Science, Polymer Edition 15(2004)2,145-159

Permalink: https://www.hzdr.de/publications/Publ-5244
Publ.-Id: 5244


Diamond formation in cubic silicon carbide

Pécz, B.; Weishart, H.; Heera, V.; Tóth, L.;
High-dose carbon implantation (3x10e17 and 1x10e18 ions/cm2) into cubic SiC on Si was carriedout at elevated temperatures (600 to 1200 °C) and different dose rates (1x10e13 to 1.5x10e14 cm-2 s-1). Transmission electron microscopy revealed the formation of either graphite or diamond precipitates, depending on the implantation parameters. In all cases, the diamond grains were epitaxial to the SiC lattice, while the graphite was textured. The minimum temperature for diamond formation was 900 °C, while graphite formed at 600 °C. The synthesized phase depends as well on the dose rate; graphite was formed at 900 °C with a high dose rate. Obviously, a criticaltemperature for diamond formation exists and increases with increasing dose rate. This behavior is explained by the competition between the accumulation and dynamic annealing of radiation defects in the SiC lattice, which acts as a template for diamond nucleation. Diamond grains with diametersas large as 10 nm have been observed after implantation at 1200 °C.
Keywords: Diamond, Silicon Carbide, Ion Beam Synthesis, Carbon Implantation, Transmission Electron Microscopy

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Publ.-Id: 5243


On-line concentration estimation during chemical reactions using adaptive heat/ mass balances

Kryk, H.; Hessel, G.; Schmitt, W.; Seiler, T.; Weiß, F.-P.; Hilpert, R.; Roth, M.;
In the fine chemical industry, complex strongly exothermic reactions are usually carried out in semibatch mode in stirred tank reactors. These reactors are characterised by nonsteady-state conditions due to the discontinuous operation. Thus, it is difficult to estimate the actual conversion and to identify undesired process states during the chemical reaction, particularly, if the reactor is not equipped with expensive measuring systems for chemical on-line analysis. Therefore, an on-line monitoring system was developed that is able to estimate the concentration profiles without the need of chemical on-line analysis.
The on-line estimation of the concentration profiles is based on calculations of the thermal and chemical conversion courses during the chemical process using heat and mass balances. In order to consider factors of influence, such as heat losses, heat bridges and systematic measuring errors, adaptive model components are included. The adaptation of the complex model to the target plant is done by software-supported calculations of the adaptive parameters using process data of at least one normal batch course in the chemical plant.
The monitoring system was developed, optimised and tested by means of experiments in a miniplant at laboratory scale. As a test process, the strongly exothermic catalytic hydrogenation of an aromatic nitro compound was chosen. For industrial testing, the monitoring system was integrated into a batch-information-management system which was implemented into the process control system of a multipurpose reactor installation in the fine chemical factory at Radebeul (Degussa, Inc.). The tests showed good agreements of the estimated concentration profiles with analytical measurements in both, the laboratory and the industrial scale. Furthermore, it was found that deviant reaction courses and undesired process states can be recognised very earlier using the on-line monitoring system than with exclusive knowledge of process variables like temperatures, pressures and volume flows.
  • Lecture (Conference)
    4th European Congress of Chemical Engineering, 21-25 September 2003 Granada, Spain, Topic 10 Abstracts, O-10.2-001
  • Contribution to proceedings
    4th European Congress of Chemical Engineering, 21-25 September 2003 Granada, Spain, Topic 10 Abstracts, O-10.2-001

Permalink: https://www.hzdr.de/publications/Publ-5242
Publ.-Id: 5242


RPV Integrity Assessment by Operational Feedback: Post Service Investigations of VVER-type NPPs

Rindelhardt, U.; Böhmer, B.; Böhmert, J.;
The investigation of RPV material from decommissioned NPPs offers the unique opportunity to evaluate the real toughness response. By investigation of material from the decommissioned VVER 440-type Greifswald NPP the evaluation of a standard RPV design and the assessment of the quality of prediction rules and assessment tools will be possible. First results of the investigations are presented in the paper.
  • Lecture (Conference)
    ANS 2003 Annual Meeting, San Diego, June 2003
  • Transactions of ANS, Vol. 88,(2003)p. 547

Permalink: https://www.hzdr.de/publications/Publ-5241
Publ.-Id: 5241


First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions

Förster, A.; Uhlig, F.; Böttcher, I.; Debowski, M.; Dohrmann, F.; Grosse, E.; Koczon, P.; Kohlmeyer, B.; Laue, F.; Menzel, M.; Naumann, L.; Oeschler, H.; Scheinast, W.; Schwab, E.; Senger, P.; Shin, Y.; Ströbele, H.; Sturm, C.; Surowka, G.; Wagner, A.; Walus, W.;
Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 A·GeV. The K-/K+ ratio is found to be nearly constant as a function of the collision centrality. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+ mesons decouple earlier from the fireball than K- mesons.

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Permalink: https://www.hzdr.de/publications/Publ-5240
Publ.-Id: 5240


Evolutionary aspects of the S-layers of Bacillus sphaericus

Schnorpfeil, M.; Raff, J.; Pollmann, K.; Merroun, M.; Selenska-Pobell, S.;
The primary structures of the S-layer proteins of the uranium mining waste pile isolate Bacillus sphaericus JG-A12 and of Bacillus sphaericus NTCC9602 were analysed. The amino acid sequences of the two proteins are almost identical but possess an abrupt homology to some of the other B. sphaericus S-layers studied up to date. This is an indication that a horizontal transfer of genetic information was involved in the evolution of the genes of the mentioned S-layers. An extensive comparative analysis of the S-layer proteins deposited to the GeneBanks demonstrated that several additional S-layers of B. sphaericus and of other Bacillus species were also subjected to late evolutionary events via lateral DNA transfer. The possible mechanism of these events in the case of B. sphaericus will be discussed.
Interestingly, the slight amino acid differences between the S-layer proteins of the strains JG-A12 and NTCC9692 lead to dramatic differences in their ability to interact with metals and also in their stability against proteases. As estimated by using EXAFS spectroscopy phosphorous residues, in addition to the carboxyl groups of the proteins, are involved in the binding of uranium (VI). ICP-MS analysis demonstrated that the two purified and recrystalized S-layer proteins contain phosphorous which indicates that they are phosphorylated. Moreover, the amount of phosphorous found in the S-layer of the strain JG-A12 was six times higher than those found in the S-layer of the reference strain NTCC 9602. This explains the higher ability of the S-layer of the uranium mining waste isolate to complex uranium and other metals. The latter seems to give an advantage to the strain JG-A12 to survive in the heavily polluted with uranium and other toxic metals environment from which it was recovered.













  • Lecture (Conference)
    Abstract in Proceedings of VAAM Jahrestagung 2003

Permalink: https://www.hzdr.de/publications/Publ-5238
Publ.-Id: 5238


Molecular analysis of the S-layer proteins of Bacillus sphaericus strains JG-A12 and NTCC 9602

Raff, J.; Schnorpfeil, M.; Pollmann, K.; Selenska-Pobell, S.;
Uranium mining waste pile isolate Bacillus sphaericus JG-A12 and it's closest relative B. sphaericus NTCC 9602 possess S-layer proteins with a similar size of about 135 kDa and with a square lattice symmetry. The two proteins differ significantly in their ability to interact with metals and in their stability against proteases and pH changes. By using ICP-MS, the "Stain-all" dye, and colourimetric method it was demonstrated that both proteins are phosphorylated but the S-layer of the strain JG-A12 contains six times more phosphorous than those of the reference strain NTCC9602. Surprisingly, the two proteins share an extremely high homology of 98 % in the region of the N-terminal S-layer homologous domains and of 91 % in the region of the central domains. It is noticeable that the minor amino acid differences between the S-layers of the studied strains consist of threonine and serine enrichments in the case of JG-A12. Bearing in mind that the majority of the phosphoproteins are usually modified at threonine and serine residues, our observation explains the higher level of phosphorylation of the S-layer of the uranium mining isolate JG-A12. The higher amount of phosphate groups of this protein explains also it's ability to complex more effectively uranium and other metals.
In addition, there are evidences that the two Bacillus sphaericus strains studied possess an additional S-layer or an S-layer-like copy which seems to be located on large indigenous plasmids.
  • Poster
    Abstract in Proceedings of VAAM Jahrestagung 2003

Permalink: https://www.hzdr.de/publications/Publ-5237
Publ.-Id: 5237


Bacteria-based bioremediation of uranium mining waste waters by using sol-gel ceramics

Raff, J.; Soltmann, U.; Matys, S.; Pompe, W.; Böttcher, H.; Selenska-Pobell, S.;
Sol-gel ceramics with high metal binding capacity were prepared via homogeneous dispersion and embedding of vegetative cells, spores and EDC stabilised surface proteins (S-layers) of Bacillus sphaericus JG-A12. The B. sphaericus JG-A12 strain was recovered from a uranium mining waste pile near the town of Johanngeorgen-stadt, Saxony, Germany (1). The whole cells as well as the purified S-layer protein of this strain possess an ability to bind selectively and very effectively uranium and several other metals such as Cu, Pb, Cd, Al, Pt and Pd (1, 2).
In this work the biosorption of U and Cu by the above mentioned three bacteria-based biological ceramics (biocers) was investigated. In addition, the metal binding capacity of the free SiO2 nanomatrix and of the three individual bacterial components (the vegetative cells, the spores and the S-layers) was studied as well.
Our results demonstrate that the high U and Cu binding capability of the three kinds of biocomponents is influenced by the sol-gel process in a different way. The metal binding properties of the vegetative cells and of the S-layers were not negatively influenced by the sol-gel treatments. The metal binding capacity of the embedded spores was, however, significantly lower than those of the non embedded spores. Very limited amounts of U and no Cu were bound by the silicate matrix alone.
The metal binding capacity of the biocers and also the kinetic of the biosorption were positively influenced by adding water soluble compounds such as sorbitol or by freeze drying instead of air drying. These results are connected to the higher porosity achieved by the mentioned treatments.
Both metals can be completely desorbed and washed from the biocers by using 0.5 M solution of citric acid. Afterwards the biocers can be reused for metal biosorption.
Due to their stability, high metal binding capacity and simple and complete removal of the bound metals described biocers are good candidates for construction of intelligent filters for cleaning of heavy metal contaminated liquid wastes.
The geographic origin of the source of the biocomponents, namely the strain B. sphaericus JG-A12, makes the constructed bioceramics promising for in situ bioremediation of the drain waters of the uranium mining waste piles and mill tailings.

References

1. Selenska-Pobell S., Miteva V., Boudakov I., Panak P., Bernhard G., and Nitsche H. (1999) Selective accumulation of heavy metals by three indigenous Bacillus isolates, B. cereus, B. megaterium and B. sphaericus in drain waters from a uranium waste pile.FEMS Microbiol Ecology 29, 59-67.
2. Raff J (2002) Wechselwirkungen der Hüllproteine von Bakterien aus Uran-abfallhalden mit Schwermetallen PhD Thesis, FZR-Report 358
  • Lecture (Conference)
    Abstract in Proceeding of 21. DECHEMA-Jahrestagung 2003, 2.-4.4.03

Permalink: https://www.hzdr.de/publications/Publ-5235
Publ.-Id: 5235


Uranium Mining Wastes as a Reservoir of Unusual Bacteria Prospective for Bioremediation and Nanotechnology

Selenska-Pobell, S.; Geißler, A.; Merroun, M.; Schnorpfeil, M.; Raff, J.; Radeva, G.; Flemming, K.;
Bacterial communities were studied in several uranium mining waste piles in Germany and in the USA by using 16S rDNA and RISA retrievals. Both approaches revealed extremely high and site-specific bacterial diversity. However, several bacterial groups including also novel lineages seem to be characteristic for the studied heavy-metal-polluted environments.
In parallel with the above mentioned direct molecular approaches, the method of enrichment culturing was applied in order to recover and study particular bacterial strains indigenous for the U wastes. Bacterial isolates belonging to different species representing diverse bacterial groups were recovered and characterized. The resistance and the interactions of these isolates with U and other heavy metals were demonstrated to be species- and even strain-specific. The atomic structures and the cellular location of the complexes formed by the isolates with U(VI) were studied using EXAFS spectroscopy, TEM, and EDX analyses. In all cases phosphate groups were predominantly implicated in the complexation of uranium but the structural parameters and the cellular location of the complexes differed between the studied bacterial groups.
Many of the studied strains possess unusual characteristics as the isolate JG-A12, for instance, which accumulates selectively U, Cu, Pb, Al, and Cd. This strain as well as it's intrinsic S-layer are forming U(VI)-complexes with identical structural parameters in which phosphorous residues in addition to the carboxyl groups are involved. ICP-MS and the "Stain-all" dye methods demonstrated that the S-layer of JG-A12 is phosphorylated. This can explain it's high ability to complex uranium and other metals. The latter seems to give an advantage to the strain to survive in the heavily polluted with uranium and other toxic metals environment from which it was recovered. Pd and Pt metallic nanoclusters were also successfully grown on the sheets of this S-layer. The latter is of interest for the nanotechnology. Interestingly, the S-layer of JG-A12 possesses unusual primary structure which indicates that lateral transfer was involved in the evolution of it's gene.
1848 words.
Keywords: bacterial diversity; S-layer, EXAFS, complexation of uranium

Keywords: Keywords: bacterial diversity; S-layer, EXAFS, complexation of uranium
  • Poster
    103rd ASM General Meeting, May 18 - May 22, 2003, Washington, DC, United States of America
  • Contribution to proceedings
    103rd ASM General Meeting, 18.-22.05.2003, Washington DC, United States of America

Permalink: https://www.hzdr.de/publications/Publ-5234
Publ.-Id: 5234


Elastic modulus of amorphous boron suboxide thin films studied by theoretical and experimental methods

Music, D.; Kreissig, U.; Chirita, V.; Schneider, J. M.; Helmersson, U.;
Boron suboxide BOx thin films have been deposited on Si (100) by reactive rf magnetron sputtering of B powders in an Ar/O2 atmosphere. Elastic recoil detection analysis and x-ray diffraction were used to study the influence of the O incorporation on the film composition and structure and relate them to mechanical properties, which were evaluated by nanoindentation. As x in BOx was increased from 0.08 to 0.18, the elastic modulus of the x-ray amorphous films decreased from 273 to 231 GPa, by 15%. This can be understood using classical molecular dynamics (MD) with a Buckingham-like interaction potential: The increase in the O concentration and corresponding formation of B–O bonds, shown to be longer than the B–B bonds, resulted in larger ionic contributions as well as a density reduction. This increased ionicity was responsible for the observed decrease in elastic modulus. As even more O was incorporated (x>0.18), the H concentration increased, exceeding 0.3 at. %. This may cause the formation of boric acid (H3BO3) as a result of the chemical reaction with H2O upon atmosphere exposure. The presence of van der Waals and hydrogen bonding, associated with H3BO3 formation, provides a reasonable explanation for the extensive decrease in elastic modulus from 231 to 15 GPa, by 94%. The parameterization for the Buckingham-like interaction potential, introduced in this study, can be used for MD simulations of amorphous BOx systems without H3BO3.

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Publ.-Id: 5233


Investigations of the damage structure near the crack tip in Al-alloys by means of small angle x-ray scattering

van Ouytsel, K.; Böhmert, J.; Müller, G.; Roth, S.; Burghammer, M.;
Structural materials, such as bainitic and austenitic steels and aluminium alloys as
used in the nuclear and aircraft industry are subject to external stresses in different environments. Understanding the growth of an assumed preexisting crack under these conditions is of prime importance to prevent extensive crack propagation and failure of the component. The ongoing research aims to investigate the early stages of ductile fracture, the nucleation, growth and coalescence of microvoids and the evolution of the spatial dislocation distribution. Two commercial Al-alloys, alloys 2024-T351 and 6013-T6 used in the aircraft industry were investigated. Within the above framework, a small region around the crack tip of a 2024-T351 specimen was scanned using a microfocused beam of 5 µm in diameter (Esrf, ID13-Microfocus).
The major improvement lies in the strongly diminsihed influence of grain boundary scattering. Information from fracture toughness tests, from the simulation of the distribution of stresses and strains by means of finite element analysis, from scanning and transmission electron microscopy and positron annihilation microprobe experiments, will support the small angle X-ray scattering investigations.
  • Poster
    Posterbeitrag zur XII. International Conference on Small Angle Scattering, 25.-29.08.2002, Venice, Italy

Permalink: https://www.hzdr.de/publications/Publ-5229
Publ.-Id: 5229


Small Angle Scattering Research at FZ Rossendorf

van Ouytsel, K.;
Der Vortrag gab ein allgemeines Bild von den Kleinwinkelstreuuntersuchungen, die am FZ Rossendorf, Abt.Material-und Komponentensicherheit durchgeführt werden, ein Bild von den Materialien (Al-Legierungen und RDB-Stähle) und Techniken/Anlagen, die dazu erforscht/angewandt werden.

  • Lecture (others)
    Vortrag an der TU Delft, 31.10.2002, Delft, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-5228
Publ.-Id: 5228


SAXS near the crack tip in metals

van Ouytsel, K.;
Der Vortrag gab das Ziel des Untersuchungsvorhabens wieder und erteilte allgemeine Informationen über den Stand der Röntgen-Kleinwinkelstreuungsforschung zur Charakterisierung der Rissspitze in Metallen.
  • Lecture (others)
    Vortrag am SCK.CEN, 12. März 2002, Mol, Belgien

Permalink: https://www.hzdr.de/publications/Publ-5227
Publ.-Id: 5227


Electric Field and Drift Characteristics Studies for the Multiwire Chambers of the Third Plane of HADES

Kanaki, K.; (Editor)
Aim of this report is the investigation of suitable operational conditions for the drif{}t chambers MDC III installed in the HADES setup. The simulations performed showed that operating the drif{}t chambers in a mode with nearly constant electron drif{}t velocity in a predominant part of the cell allows a more precise and fast tracking. This is particularly important for electrons and positrons; here the invariant dilepton mass must be reconstructed with high precision to get a resolution of $\Delta M/M\approx 1\%$ for the $\omega$ and $\phi$ mass peaks and thus a chance to verify also small in-medium mass shif{}ts. This helps to realize the physics program at HADES which focuses on the search for such mass shif{}ts to get insight into the in-medium behaviour of hadrons in dense strongly interacting matter.
Keywords: drift cell, drift chamber, drift velocity, equipotential contours, Garfield simulations, HADES, isochrones, Opera simulations
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-365 Januar 2003

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Permalink: https://www.hzdr.de/publications/Publ-5226
Publ.-Id: 5226


Die Simulation des Teilentlastungs-Compliance-Verfahrens mittels eines Finite-Element-Programms zur Rissfortschrittsberechnung an einer 3-Punkt-Biegeprobe

Werner, M.;
Das Verhalten einer 3-Punkt-Biegeprobe mit Anriss unter Belastung kann mittels einem Finite-Element-Modell nachgebildet werden. Das Modell ermöglicht die Berücksichtigung von elastisch-plastischem Materialverhalten entsprechend der jeweiligen materialspezifischen nichtlinearen Spannungs-Dehnungs-Kurve, welche mit dem Modell der multilinearen kinematischen Verfestigung (MKIN) umgesetzt wird. Weiterhin gestattet das Modell die Beschreibung der Rollenkinematik beim Biegevorgang. Unter Einbeziehung eines speziellen Damage-Modells für die Beschreibung des Bruchkriteriums ist das Modell in der Lage sowohl den Beginn des Risswachstums als auch den Rissfortschritt wiederzugeben.
Mit diesem Modell lässt sich auch das Teilentlastungs-Compliance-Verfahren nachbilden. Diese Simulation ermöglicht Korrekturansätze zur experimentellen Risslängenbestimmung über die Compliance-Methode.
Keywords: Compliance, Charpy-Probe, Risswachstum, crack extension
  • Poster
    DVM-Tagungsband "Werkstoffprüfung 2002", Wiley-VCH Verlag
  • Contribution to proceedings
    DVM-Tagungsband "Werkstoffprüfung 2002", Wiley-VCH Verlag

Permalink: https://www.hzdr.de/publications/Publ-5225
Publ.-Id: 5225


Evaluation of Irradiation Embrittlement of Reactor Pressure Vessels (RPV)

Ulbricht, A.; Strunz, P.;
The A533B Cl.1-type RPV steel, designated JRQ, has been used as IAEA reference steel and shows a high sensitivity against radiation embrittlement. Specimens from this material were irradiated to three different levels of neutron fluences. Thus, the investigation allows to realize the dependence of microstructural changes on the fluence and a comparison with results on VVER-type RPV steels, which differ from the Western RPV steel design.
Keywords: SANS radiation embrittlement microstructure
  • Contribution to external collection
    BENSC Experimental Reports 2001, Hahn-Meitner Institut Berlin, HMI-B 584, p. 208, May 2002

Permalink: https://www.hzdr.de/publications/Publ-5224
Publ.-Id: 5224


Kleinwinkelstreuung - ein vielversprechendes Werkzeug zum Nachweis von Strahlenschäden

Böhmert, J.; Große, M.; Ulbricht, A.;
Durch Bestrahlung mit Neutronen entstehen in Konstruktionswerkstoffen nanoskalige Strukturdefekte, die vielfach mit den hochauflösenden, direkt abbildenden Untersuchungsverfahren nicht oder nicht ausreichend nachweisbar sind. Diese Strukturdefekte führen aber zu einer erhöhten Streuung von Neutronen- und Röntgenstrahlen im Kleinwinkelbereich. Aus der Intensitätsverteilung der Kleinwinkelstreuung lassen sich, wenn vereinfachende Annahmen getroffen werden können oder Vorinformationen vorhanden sind, Größenverteilung und Anzahldichte bestimmen. Darüber hinaus sind Hinweise zum Typ und zur Zusammensetzung der Defekte ableitbar. Das Kleinwinkelstreuverfahren ist effektiv, volumenintegrierend, sensitiv im Größenbereich von ~ 1 nm ... 10 nm und unempfindlich gegenüber Präparationsfehlern. Es ist jedoch eine indirekte Methode der Strukturanalyse und sollte deshalb nicht alternativ, son-dern komplementär angewandt werden. Prozedur und Leistungsfähigkeit des Verfahrens wird am Beispiel von Untersuchungen an bestrahlten Reaktordruckbehälterstäh-len gezeigt.
  • Lecture (others)
    Werkstofftag 2002, TU Dresden, Dresden, 04. 10. 2002, eingeladener Vortrag

Permalink: https://www.hzdr.de/publications/Publ-5223
Publ.-Id: 5223


The SHIP Experiment at the GDT Facility - Concept and Results of Calculations

Anikeev, A. A.; Bagryansky, P. A.; Ivanov, A. A.; Noack, K.;
At present, the Gas Dynamic Trap (GDT) facility of the Budker Institute Novosibirsk is being upgraded. The first stage of the upgrade is the Synthesized Hot Ion Plasmoid (SHIP) experiment. It aims, on the one hand, at the investigation of plasmas which are expected to appear in the region of high neutron production in a GDT based fusion neutron source proposed by the Budker Institute and, on the other hand, at the investigation of plasmas the parameters of which have never been achieved before in magnetic mirrors. In parallel to experimental research at the GDT an Integrated Transport Code System (ITCS) is under development in collaboration with the Forschungszentrum Rossendorf. It is to calculate the relevant physical effects which are connected with neutral gas, background plasma and with the high-energetic ion component inside the central cell of the GDT and later inside the neutron source.
This contribution explains the concept of the SHIP experiment and presents the results of first calculations by means of ITCS modules.

Keywords: neutron source, fusion technology, mirror plasma facility, gas dynamic trap, material research, high-energetic ions
  • Lecture (Conference)
    4th Int. Conf. on Open Magnetic Systems for Plasma Confinement, July 1-4, Jeju Island, Korea, Proceedings in: Transactions of Fusion Technology, 43 (2003) 78
  • Contribution to external collection
    4th Int. Conf. on Open Magnetic Systems for Plasma Confinement, July 1-4, Jeju Island, Korea, Proceedings in: Transactions of Fusion Technology, 43 (2003) 78

Permalink: https://www.hzdr.de/publications/Publ-5222
Publ.-Id: 5222


Composition analysis of the insulating barrier in magnetic tunnel junctions by grazing angle of incidence RBS

Wei, P.; Barradas, N. P.; Soares, J. C.; Da Silva, M. F.; Kreissig, U.; Cardoso, S.; Freitas, P. P.;
Spin dependent tunnel junctions (Si/Al2O3/Ta/CoFe/AlNx/CoFe/Ta) were studied with grazing angle of incidence Rutherford backscattering spectrometry experiments using a 1.6 MeV He+ beam. While the sensitivity to light elements is too small to detect the N directly, the thickness and composition of the AlNx insulating barrier can be obtained by carefully simulating the signal of the Al and of two CoFe layers, which can be separated. From the observed Al signal the corresponding energy loss can be calculated, and the extra energy loss required to obtain the observed CoFe layer separation is assigned to the N. Eventual oxidation in the AlNx layer during film deposition can be further identified and quantified by analysing a similar tunnel junction, but deposited on a DLC substrate. A depth resolution of 25 Å at the CoFe layers ensures a highly precise measurement of this complex magnetic system.
Keywords: RBS; Tunnel junction; Insulating barrier; Ultra-thin oxynitrides
  • Nuclear Instruments and Methods B 190 (2002) 684-688

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Publ.-Id: 5221


Ion beam studies of MBE grown GaN films on (111) silicon substrates

Alves, E.; Barradas, N. P.; Monteiro, T.; Correia, R.; Kreissig, U.;
GaN epitaxial films were grown on silicon substrates by molecular beam epitaxy under different conditions. Some of the films were doped with the rare earths (RE) Er, Eu or Tm during the growth, and were studied regarding its composition and crystalline quality. The Rutherford backscattering/channelling and heavy ion elastic recoil detection techniques were combined in order to get information on the depth distribution of all the elements present in the films. The results show that the single crystalline quality of the films improves with increasing substrate temperature and Ga flux. For these conditions the Ga concentration is the one expected for a stoichiometric film. A decrease of the Ga flux or increase in the RE cell temperature allows an increase of the concentration of the RE incorporated during the growth. The light impurity present in all the films studied, within our detection limits, was hydrogen. The angular scans along the <0 0 0 1> reveal that a fraction of the RE is incorporated into regular lattice sites of the wurtzite structure of GaN. Moreover, the optical properties of the films correlate well with the crystalline quality and the Eu doped samples show an intense red luminescence at room temperature.
Keywords: GaN epilayers; RE luminescence; RBS/channelling; ERDA
  • Nuclear Instruments and Methods B 188 (2002) 73-77

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Permalink: https://www.hzdr.de/publications/Publ-5220
Publ.-Id: 5220


Experimental and numerical investigation of one and two phase natural convection

Krepper, E.; Prasser, H.-M.;
Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. Several tests were carried out both with heating from the bottom and with heating from the side walls. The test tank was equipped with thermocouples for measuring the temperature distribution and with needle probes for measuring of the local void fraction.
Calculations were performed using the CFD-code CFX-4. The simulation comprises two phase flow, subcooled boiling at the heated wall and steam release at the tank surface. The paper presents comparisons of measured and calculated temperatures and void fractions. CFX-4 simulations using the implemented boiling model reproduce and explain the observed physical phenomena. Convergence problems occurred with higher vapour volume fractions. As an application measures were investigated, to reduce the temperature stratification. It could be shown, that the insertion of buffle plates reduces and postpones the steam release.
Keywords: Natural convection, heating up, boiling, experiments, CFD simulations
  • Scientific Papers of the Kielce University of Technology, Series Mechanics,Vol. 77, 2003, pp. 33-39

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Permalink: https://www.hzdr.de/publications/Publ-5219
Publ.-Id: 5219


Mechanical properties of thin films in the ternary triangle B-C-N

Linss, V.; Hermann, I.; Schwarzer, N.; Kreissig, U.; Richter, F.;
We report on thin films in the ternary system B–C–N deposited by reactive magnetron sputtering of targets with different B/C ratio in an Ar/N2 gas mixture. First, the proportion of nitrogen in the gas was varied from 0 to 100% with the substrate being at floating potential in order to change the incorporated amount of nitrogen in the films. Secondly, at 50% nitrogen in the gas a negative substrate potential was applied for ion bombardment of the growing film. The film composition was measured by elastic recoil detection analysis. The mechanical properties, Young's modulus and hardness, were determined from nanoindentation measurements. All films were also investigated by Fourier-transformed infrared spectroscopy (FTIR). The mechanical properties show a great variation range in dependence on the film composition (up to a factor of three) and ion bombardment (up to a factor of two), which can be related to the bonding characteristics derived from the FTIR spectra.
Keywords: Reactive magnetron sputtering; BCN; Mechanical properties
  • Surface and Coatings Technology 163-164 (2003) 220-226

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Permalink: https://www.hzdr.de/publications/Publ-5218
Publ.-Id: 5218


Enhanced corrosion resistance of austenitic stainless steel by plasma immersion ion implantation of nitrogen

Pham, M. T.; Ram Mohan Rao, K.; Manna, I.; Richter, E.;
Surface coating on austenitic stainless steel 304 (ASS) was generated by plasma immersion ionimmplantation (PIII) of nitrogen. The corrosion resistance was shown to increase by ca. four orders of magnitude. A barrier layer produced by PIII was observed to restrict the underlaying alloy surface exposed to the corrosion environment.
Keywords: corrosion, stainless steel, surface coating, ion beam treatment
  • Journal of Materials Science Letters 22 (2003) 1099-1100

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Publ.-Id: 5217


Strangeness saturation: energy- and system-size dependence

Cleymans, J.; Kämpfer, B.; Steinberg, P.; Wheaton, S.;
Relativistic heavy-ion collisions lead to a final state which has a higher degree of strangeness saturation than those of elementary collisions. A systematic analysis of this phenomenon, based on the strangeness saturation factor, is made for C+C, Si+Si and Pb+Pb collisions at the CERN SPS collider and for Au+Au collisions at RHIC energies. Strangeness saturation is shown to increase with the number of participants within a colliding system, at both CERN SPS and RHIC energies. The saturation observed in central collisions of lighter nuclei deviates from that seen in peripheral collisions of heavier nuclei with an equivalent participant number, which could be due to the difference in nuclear density.
Keywords: relativistic heavy-ion collisions, strangeness, hadron production
  • arXiv:hep-ph/0212335v1

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Publ.-Id: 5216


Determination of Structural Parameters for Thorium(IV), Neptunium(IV), Neptunium(V) and Plutonium(III) Humate Complexes by Means of XAFS Spectroscopy

Schmeide, K.; Sachs, S.; Reich, T.; Heise, K. H.; Bernhard, G.;
Structural parameters for the near-neighbor surrounding of Pu(III), Th(IV), Np(IV) and Np(V) in complexes with various natural and synthetic humic and fulvic acids were determined by means of X-ray absorption fine structure (XAFS) spectroscopy. Furthermore, the interaction of the actinides with Bio-Rex70, a cation exchange resin having solely carboxylic groups as metal binding functional groups, was studied to determine structural parameters for the interaction of the respective actinide ions with carboxylic groups. Applying chemically modified humic acids with blocked phenolic/acidic OH groups, the influence of phenolic/acidic OH groups on the complexation of Np(V) by humic acids was studied in the neutral pH range. The structural parameters determined for actinide humate complexes were further compared with structural parameters of aqueous ions of the actinides and of solid actinide carboxylates given in the literature. The results indicate that the interaction between the actinide ions and humic acid is dominated by humic acid carboxylate groups. These carboxylate groups act predominantly as monodentate ligands. A contribution of phenolic/acidic OH groups to the complexation of Np(V) by humic acids at pH 7 cannot completely be excluded by EXAFS analysis.
Keywords: Thorium(IV), Neptunium(IV), Neptunium(V), Plutonium(III), Humic acid, Fulvic acid, EXAFS, XANES, Complexation, tetravalent
  • Contribution to external collection
    FZKA 6800, Wissenschaftliche Berichte, Forschungszentrum Karlsruhe, Karlsruhe 2003, S. 65-77.

Permalink: https://www.hzdr.de/publications/Publ-5215
Publ.-Id: 5215


Elastic modulus-density relationship for amorphous boron suboxide thin films

Music, D.; Kreissig, U.; Czigany, Z.; Helmersson, U.; Schneider, J. M.;
Boron suboxide thin films have been deposited on Si(100) substrates by reactive RF magnetron sputtering of a sintered B target in an Ar/O2 atmosphere. Elastic recoil detection analysis was applied to determine the film composition and density. Film structure was studied by X-ray diffraction and transmission electron microscopy. The elastic modulus, measured by nanoindentation, was found to decrease as the film density decreased. The relationship was affected by tuning the negative substrate bias potential and the substrate temperature during film growth. A decrease in film density, by a factor of 1.55, caused an elastic modulus reduction by a factor of 4.5, most likely due to formation of nano-pores containing Ar. It appears evident that the large scattering in the published data on elastic properties of films with identical chemical composition can readily be understood by density variations. These results are important for understanding the elastic properties of boron suboxide, but may also be qualitatively relevant for other B-based material systems.
  • Applied Physics A76 (2003) 269-271

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Publ.-Id: 5214


Factors affecting an efficient sealing of porous low-k dielectrics by physical vapor deposition Ta(N) thin films

Iacopi, F.; Tökei, Z.; Le, Q. T.; Shamiryan, D.; Conard, T.; Brijs, B.; Kreissig, U.; van Hove, M.; Maex, K.;
The deposition of homogeneous thin films on porous substrates has been investigated. The thin film deposition of Ta(N) by physical vapor deposition on porous films with different average pore sizes and material compositions has been studied. The continuity of Ta(N) films on top of porous low-k dielectrics is evaluated by means of ellipsometric porosimetry combined with sheet resistance and atomic force microscopy measurements. Interface reactions are analyzed by x-ray photoelectron spectroscopy profiling. It has been observed that the minimal Ta(N) thickness required to obtain a continuous metal layer on top of the porous film depends, on the one hand, on the porosity and pore size and, on the other hand, on the chemical interaction of the thin film with the porous substrate. The sealing of pores is favored by the presence of carbon in the dielectric matrix. This is explained through a mechanism of local enhancement of the degree of crosslinking in the dielectric matrix, catalyzed by Ta.
  • Journal of Applied Physics 92 (2002) 1548

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Publ.-Id: 5213


Sputterionenquelle

Friedrich, M.; Tyrroff, H.;
Der Erfindung liegt die Aufgabe zugrunde, die Lebensdauer einer Sputterionenquelle zu erhöhen, den Wartungsaufwand zu senken und die Zerstäubung der Teile der Ionenquelle, welche sich in der Nähe des für die Erzeugung der negativen Ionen erforderlichen Kathodeneinsatzes befinden, weitgehend zu verhindern.
Die Erfindung geht aus von den Bauteilen Ionisierer (2), Kathode (3), Sputtereinsatz (4), Formierungselektrode (5), Abschirmkappe (6) und Kathodenisolator (7) in einem vakuumdichten Gehäuse.
  • Patent
    Patentanmeldung 102 41 252.9
  • Patent
    DE 102 41 252 B4
  • Patent
    EP 1 396 870 A3

Permalink: https://www.hzdr.de/publications/Publ-5211
Publ.-Id: 5211


Verfahren zur Reinigung von Wasser mit hohen Uran-Konzentrationen

Walter, M.; Arnold, T.;
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zu entwickeln, dass Uran(VI) aus stark belasteten bergbaulichen Abwässern, Haldensicker-, und kontaminierten Grundwässern kostengünstig und umweltfreundlich in großen Mengen entfernt, wobei zur Uranfixierung ein Barrierematerial eingesetzt werden soll, das eine Beschaffenheit aufweist, die eine langzeitstabile, sichere Endlagerung oder Wiedergewinnung des angereicherten Urans ermöglicht.
Die technische Lösung geht davon aus, dass das Uran(VI) überwiegend als Karbonat, Sulfat oder Hydroxy-Komplex vorliegt und elementspezifische Filtermaterialien in einer geochemischen Barriere eingesetzt werden.
  • Patent
    Patentanmeldung 102 38 957.8
  • Patent
    DE 102 38 957 A!

Permalink: https://www.hzdr.de/publications/Publ-5210
Publ.-Id: 5210


Verfahren zur tomographischen Bildrekonstruktion für ein aus zwei asynchron rotierenden komponeneten bestehendes Objekt

Hoppe, D.;
Die Erfindung betrifft ein Verfahren zur tomographischen Bildrekonstruktion für ein aus zwei asynchron rotierenden Komponenten bestehendes Objekt, wobei an einzelnen Drehwinkelpositionen der Objektkomponenten tomographische Projektionen vorgenommen werden.
Der Erfindung liegt die Aufgabe zugrunde, die beiden mit unterschiedlichen Winkelgeschwindigkeiten gegenüber ihrer Umgebung rotierenden Teilobjekte mit Hilfe eines Tomographen richtig abzubilden.
  • Patent
    Patentanmeldung 102 08 284.7
  • Patent
    DE-OS 102 38 540 A1

Permalink: https://www.hzdr.de/publications/Publ-5207
Publ.-Id: 5207


Bioaktives Material und Verfahren zu dessen Herstellung

Pham, M. T.; Maitz, M. F.;
Die Erfindung betrifft ein bioaktives Material sowie ein Verfahren zu dessen Herstellung. Potentielle Anwendungen sind medizinische Implantologie, Gewebezüchtung und Biotechnologie. Der Erfindung liegt ein von einer Schicht zellausgeschiedener Produkte umgebenes Festkörpermaterial zugrunde.
Der Erfindung liegt die Aufgabe zugrunde, ein Material für Anwendungen in medizinischer Implantologie, Gewebezüchtung und Biotechnologie zu schaffen, bei welchem die Oberfläche für eine breite Klasse von Festkörpermaterialien bei Kontakt mit zellulären Medien zellbiologisch spezifische Wechselwirkungen aktiv vermittelt. Der Erfindung obliegt auch die Aufgabe, ein anwendungswirksames Verfahren zur Herstellung des genannten bioaktiven Materials vorzuschlagen.
  • Patent
    Patentanmeldung 102 05 846.6
  • Patent
    DE 102 05 846 A1

Permalink: https://www.hzdr.de/publications/Publ-5206
Publ.-Id: 5206


P0111 - Biokompositmaterial

Selenska-Pobell, S.; Soltmann, U.; Raff, J.; Böttger, H.; Kallies, K.-H.; Quast, H.; Matys, S.;
Das Biokompositmaterial enthält ein anorganisches Gel und darin homogen verteilte, trocknungsstabile Zellprodukte wie Sporen, Zellwand-Proteine oder abgetötete Zellen. Das Biokompositmaterial ist als Biofilter in der Umwelttechnik zur Entfernung von Schwermetallionen aus wässrigen Lösungen geeignet.
  • Patent
    DE 101 46 375 B4 - 01. Okt. 2009
  • Patent
    DE 101 46 375 A 1

Permalink: https://www.hzdr.de/publications/Publ-5205
Publ.-Id: 5205


Influence of melt convection on the microstructure of levitated and undercooled Nd-Fe-B alloys

Fillip, O.; Hermann, R.; Gerbeth, G.; Priede, J.; Shatrov, V.; Güth, A.; Schultz, L.;
The influence of melt rotation on the microstructure formation of Nd-Fe-B alloys, mainly the volume fraction and grain size of the a-Fe phase, has been investigated using the electromagnetic levitation technique which allows the in-situ measurement of the solidification kinetics containerlessly. Samples were subjected to a strong rotation during levitation and compared to fixed samples without additional sample rotation in the levitation facility. Additionally, experiments have been carried out where specially sealed samples were subjected to a well-defined forced rotation. A distinct reduction of the a-Fe volume fraction in samples with strong rotation was observed by measuring the magnetic moment in a vibrating sample magnetometer (VSM). The influence of cooling rate and undercooling level on microstructure formation and phase distribution has been investigated as well. The melt flow in a levitated droplet is studied numerically under the additional effect of a global sample rotation which may give a strong suppression of internal motions.
  • Lecture (Conference)
    „Int. Conference on Magnetism“, Rom, Juli 2003
  • Journal of Magnetism and Magnetic Materials 272-276(2004)Suppl. 1, 1857-1858

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Publ.-Id: 5203


Microstructure evolution of Nd-Fe-B alloys in consideration of magnetohydrodynamics

Hermann, R.; Filip, O.; Gerbeth, G.; Priede, J.; Schultz, L.;
The solidification process and the resulting microstructure of Nd-Fe-B alloys in consideration of melt convection has been investigated experimentally with a specially designed floating-zone arrangement. A controlled influence on the melt flow is possible via tailored magnetic fields which enable enhancement or suppression of the melt convection. A specially designed magnetic two-phase stirrer offers a strong influence on the melt flow in the floating-zone facility. As a result, the microstructure pattern, mainly the volume fraction and grain size of the a-Fe phase, vary strongly with the strength of the internal flow motion. The melt flow is studied numerically under the additional effect of the two-phase stirrer taking into account the coupled heat and fluid flow fields. The electromagnetically driven flow during the inductive heating turned out to be of strong influence on the resulting microstructure.
  • Lecture (Conference)
    „Int. Conference on Magnetism“, Rom, Juli 2003
  • Journal of Magnetism and Magnetic Materials 272-276(2004)Suppl. 1, 1855-1856

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Publ.-Id: 5202


CFD simulation of a bubbly flow experiment with liquid PbBi eutectic alloy and Nitrogen

Mercurio, G.; Eckert, S.;
This study was carried out in the frame of the ADS European project aimed to the development of Accelerator Driven System technology for nuclear waste transmutation.
The scope is to verify the possibility to simulate a two phase HLM (Heavy Liquid Metal) bubbly flow using the commercial CFD code CFX4.4.
The first stage consisted of an experimental campaign for the measurement of the phase velocities by means of the ultrasound Doppler velocimetry (UDV) and local volume fractions using resistive probes. The eutectic alloy PbBi is located inside a cylindrical container made of stainless steel which is provided with an electrical heater. The measurements reported here were carried out at a fluid temperature of 180°C. Nitrogen (N2) gas was injected into the stagnant liquid metal by means of a single orifice with an inner diameter of 0.5 mm. The orifice is located in the centre of the cross-sectional area of the fluid container. The gas flow rate chosen for these experiments was restricted to values below 1.2 cm3/s in order to guarantee a single bubble flow regime.
The simulation of the experiment was performed using the two fluid Euler/Euler model of CFX-4.4. The implemented drag laws were tested and compared with other drag laws taken from literature. The influence of the "non-drag forces" like the turbulent dispersion force and the lift force was also tested. Finally an advanced interpolation method based on optimization techniques was adopted in order to get the best fitting of the simulated velocity curves with the experimental ones. The results shows in general a good qualitative agreement of the experiment and the calculations, but a much better agreement can be found using the drag law coefficients derived by the above mentioned optimization technique, especially in the cases where the mass flow rates and the bubble mean diameters are relatively small.

Keywords: two-phase flow, gas bubbles, heavy liquid metals, drag force, velocity measurements, UDV technique
  • Lecture (Conference)
    Computational Methods in Multiphase Flow II, A.A.Mammoli, C.A.Brebbia (Eds.), WIT Press 2004, Southampton pp.395-404, (Proc. of the Second International Conference on Computational Methods in Multiphase Flow, Santa Fe, New Mexico, USA, 2003)
  • Contribution to proceedings
    Computational Methods in Multiphase Flow II, A.A.Mammoli, C.A.Brebbia (Eds.), WIT Press 2004, Southampton pp.395-404, (Proc. of the Second International Conference on Computational Methods in Multiphase Flow, Santa Fe, New Mexico, USA, 2003)

Permalink: https://www.hzdr.de/publications/Publ-5201
Publ.-Id: 5201


Berechnung des Notkondensators des argentinischen Integralreaktors CAREM

Schaffrath, A.; Walter, D.; Delmastro, D.; Giménez, M.; Zanocco, P.;
In Argentinien wird das Integralreaktorkonzept CAREM als alternativer Einstieg in die Kerntechnik - speziell für Länder der dritten Welt - entwickelt. Diese sammelten bislang in der Regel ihre ersten Erfahrungen in der Nukleartechnik mit Forschungsreaktoren. Das beim Betrieb der Forschungsreaktoren gesammelte Wissen ist jedoch zu speziell und nicht umfassend genug, um hiermit allein Leistungsreaktoren betreiben zu können. Da das CAREM Konzept sämtliche in großen Leistungsreaktoren vorkommende Systeme beinhaltet, können mit dem CAREM Reaktor bei vergleichsweise ähnlichen - wenn nicht sogar niedrigeren - Kosten wie bei Forschungsreaktoren sämtliche zum Betrieb mittlerer und großer Reaktoren notwendigen Systemkenntnisse erworben werden.
Keywords: ATHLET, CAREM, KONWAR, Notkondensator
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2003, 2003 Tagungsband S. 501 - 506, Inforum Verlag, ISSN 0720-9207
  • atw Internationale Zeitschrift für Kernenergie 48 (2003), Nr. 2, S. 111-115

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Publ.-Id: 5199


Tera-Hertz Radiation in Biological Research, Investigation on Diagnostics and Study on Potential Genotoxic Effects

Seidel, W.; Fahmy, K.; Furlinski, G.; Gippner, P.; Grosse, E.; Piest, H.; Sczepan, M.; Wohlfarth, D.; Wolf, A.; Wünsch, R.;
The radiation source ELBE at Dresden-Rossendorf is centered around a superconducting ELectron accelerator of high Brillance and low Emittance (ELBE) which produces electron beams up tu 40 MeV. This new facility delivers secondary radiation of diffrent kinds. Special emphasis will be given to the production of intense THz radiation from its Free-Electron-Lasers (FEL). This radiation will be used for various research activities including the life sciences. Two additional femtosecond Ti:sapphire lase system allow to exploid different methods of THz generation for such investigatin.
  • Poster
    Proc. Of the THZ-BRIDGE Workshop, Capri Italy Sept 2002
  • Contribution to proceedings
    Proc. Of the THZ-BRIDGE Workshop, Capri Italy Sept 2002

Permalink: https://www.hzdr.de/publications/Publ-5198
Publ.-Id: 5198


RBS and HIRBS studies of nanostructured AgSiO2 sol–gel thin coatings

Kokkoris, M.; Trapalis, C. C.; Kossionides, S.; Vlastou, R.; Nsoulid, B.; Grötzschel, R.; Spartalis, S.; Kordas, G.;
In the present work, composite AgSiO2 thin coatings, containing metal nanoparticles, were prepared on glass substrates by the sol–gel route. The coatings were thermally treated in oxidative and reductive conditions up to 500 °C for metal nanoparticle formation. The coating structure and the nanoparticle formation were studied by atomic force microscopy and Rutherford backscattering spectroscopy (RBS) techniques. In the case of RBS, 1.4 MeV 4He+ ions were used for all samples, and low energy 16O and 12C ions in selected ones (heavy ion RBS, HIRBS), in order to improve the depth resolution for the profiling of the metal component. The antibacterial activity against Escherichia coli is examined by antibacterial drop test. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was reduced with the increase of the particle size of the metal nanoparticles. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity is examined and analyzed. Although further studies are required, RBS and HIRBS seem to be excellent tools for the quality control in the production of sol–gel thin coatings.
Keywords: Rutherford backscattering spectroscopy; Heavy ion Rutherford backscattering spectroscopy; Sol–gel; Antibacterial; XRD; Thin coatings
  • Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volume 188 , April 2002, 67-72

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Publ.-Id: 5197


Post-Test Calculations of Medium Scaled Pressure Vessel Creep Failure Experiments

Willschütz, H.-G.; Altstadt, E.; Weiss, F.-P.; Sehgal, B. R.;
For the calculation of experiments simulating the behavior of the lower head in a core melt down scenario like FOREVER (performed at the Royal Institute of Technology, Stockholm) it is necessary to model the melt pool convection and the temperature field within the vessel as well as creep and plasticity processes. Therefore a 2D Finite Element Model is developed based on the code ANSYS®. The CFD module is used to calculate the thermodynamics. The resulting temperature field of the vessel wall is applied to the mechanical model. To describe the visco-plastic deformation a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. In this way the use of a single creep law, which employs constants derived from the data for a limited stress and temperature range, is avoided. For an evaluation of the failure times a damage model according to an approach of Lemaitre is applied.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analyzing the results of the calculations, it seems to be advantageous to provide a vessel support, which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it may be advantageous to install a passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.
Keywords: core melt down accident, lower head behavior of the RPV, Finite Element Method, creep and damage modeling
  • Lecture (Conference)
    2003 International Congress on Advances in Nuclear Power Plants ICAPP '03 May 4-7, 2003; Congress Palais, Córdoba, SPAIN, Proceedings on CD
  • Contribution to proceedings
    2003 International Congress on Advances in Nuclear Power Plants ICAPP '03 May 4-7, 2003; Congress Palais, Córdoba, SPAIN, Proceedings on CD

Permalink: https://www.hzdr.de/publications/Publ-5196
Publ.-Id: 5196


Modulated CNx films prepared by IBAD

Safran, G.; Kolitsch, A.; Malhouitre, S.; Trasobares, S.; Kovacs, I.; Geszti, O.; Menyhard, M.; Colliex, C.; Radnoczi, G.;
CNx thin films have been prepared by IBAD varying the C-atom to N-ion ratio during deposition. The layers were studied by means of TEM and EELS investigation, ERDA and AES depth profiling. The obtained films were amorphous. The incorporation probality of N into the films was found to depend on the C/N arrival ratio. Large amount of N incorporation was found above and small amount below a N/C arrival rate of 0.3. Due to intentional change in the N/C arrival rate, modulated structures have been produced. The N concentration in the individual layers of modulated samples was found to exhibit distinct values of approximately 5 and 20 at.%. The erosion rate of the various CNx layers upon Ar ion bombardment depends on their N content. The relative erosion rate of the samples containing nitrogen of 20 and 5at.% was found to be r(rel)=1.6. It was determined by XTEM and EELS that the origin of the TEM image contrast marking out the individual sublayers is mainly due to density variations in the modulated structure and partly due to thickness differences of the cross sectional TEM samples as a result of Ar ion milling of layers of various compositions
Keywords: carbon-nitride, ion assited deposition, sputter erosion rate
  • Diamond and Related Materials 11 (2002) 1552-1559

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Publ.-Id: 5195


Relativistic effects in proton-induced deuteron break-up at intermediate energies with forward emission of a fast proton pair

Kaptarii, L. P.; Kämpfer, B.; Semikh, S. S.; Dorkin, S. M.;
Recent data on the reaction pD -> (pp) n with a fast forward pp pair with very small excitation energy is analyzed within a covariant approach based on the Bethe-Salpeter formalism. It is demonstrated that the minimum non-relativistic amplitude is completely masked by relativistic effects, such as Lorentz boost and the negative-energy P components in the 1S0 Bethe-Salpeter amplitude of the pp pair.
Keywords: deuteron break-up, Bethe-Salpeter formalism

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Publ.-Id: 5194


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