Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33397 Publications

Behavior of gas bubbles in liquid metals

Eckert, S.
Due to significant differences in material properties such as density or
surface tension the behavior of gas bubbles reveals some pecularities in
liquid metal applications as compared with ordinary water flows. Moreover,
questions about the wetting of solid surfaces or the role of impurities which
have a minor importance in water systems show a more dominant influence in
metallic melts.
In this lecture some examples with respect to the bubble generation process,
the dispersion of gas bubbles or the momentum and heat transfer properties
of liquid metal bubbly flows will be presented.
The variety of standard measuring techniques to characterize liquid metal
flows is limited due to the nature of metallic melts. A selection of measuring
techniques will be discussed with respect to their capabilities and
restrictions in various applications.
An interesting point is the possibility to control liquid metal two-phase flows
by the application of external magnetic fields. Some examples will be presented
showing the influence of a stationary magnetic field on the generation of gas
bubbles, on the interfacial momentum transfer or on the turbulent dispersion
of gas bubbles.
Keywords: liquid metal two-phase flow, bubble injection, bubble motion, measuring techniques, magnetic fields
  • Lecture (others)
    Lecture series 'Fluid Dynamics in Continous Casting', von Karman Institute for Fluid Dynamics, Brüssel, 23-27 April 2001

Permalink: https://www.hzdr.de/publications/Publ-3552
Publ.-Id: 3552


Das Rigaer Dynamo-Experiment

Gerbeth, G.; Stefani, F.; Gailitis, A.; Lielausis, O.; Platacis, E.
Die Erzeugung eines Magnetfeldes allein durch die Strömung einer leitfähigen Schmelze wird von Astro- und Geophysik allgemein als Quelle kosmischer Magnetfelder akzeptiert. Dieser grundlegende physikalische Mechanismus wurde jedoch bis vor kurzem noch nie in einem Laborexperiment nachgewiesen. Am Institut für Physik Riga (Lettland) wurde in enger Kooperation mit der Abteilung MHD des Forschungszentrums Rossendorf seit etwa 6 Jahren ein solches Experiment aufgebaut, das im wesentlichen aus einer helikalen Strömung flüssigen Natriums besteht. Bei den Messungen im November 99 wurde erstmals der Effekt der Magnetfeldselbsterregung beobachtet: Bei maximaler Strömungsgeschwindigkeit wurde ein allmählich wachsendes Magnetfeld gemessen. Die charakteristischen Werte der gemessenen Magnetfeldsignale (Frequenz und Wachstumsrate) stimmen sehr gut mit den vorausberechneten überein. Weitere Messungen vom Juli 2000 bestätigten diese Ergebnisse und lieferten ein konsistentes Bild des Rigaer Dynamos: exponentielles Anwachsen des Magnetfeldes oberhalb der kritischen Strömungsrate, stabiles Magnetfeld auf Sättigungsniveaus im Bereich einiger Hundert Gauss, und axial veränderliche Sättigungsniveaus auf Grund der Rückwirkung der Lorentzkraft auf die Strömung
  • Lecture (Conference)
    im Greifswalder Physikalischen Kolloquium, Greifswald, 19.10.2000

Permalink: https://www.hzdr.de/publications/Publ-3550
Publ.-Id: 3550


Stability of levitation of solid and liquid conducting spheres in high frequency electromagnetic field

Gelfgat, Y. M.; Mikelsons, A.; Romancuks, A.; Gerbeth, G.
Experimental results for the stability of electromagnetically levitated solid and liquid spheres are presented. It is shown that the stability is solely determined by the non-dimensional frequency as predicted by theory. Quantitative values are derived for the critical frequency threshold above which rotational or oscillatory motions of the levitated sample occur.
  • Magnetohydrodynamics, Vol.36, No.2, 167-179, 2000

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Permalink: https://www.hzdr.de/publications/Publ-3549
Publ.-Id: 3549


Carbon-13 NMR Spectroscopic Studies on Chemically Modified and Unmodified Synthetic and Natural Humic Acids

Sachs, S.; Bubner, M.; Schmeide, K.; Choppin, G. R.; Heise, K. H.; Bernhard, G.
Carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy (13C-CP/MAS-NMR) was applied to study the chemical modification process of humic acids (HA) with diazomethane and the subsequent alkaline hydrolysis of the methylated HA, which results in HA with blocked phenolic OH groups. We investigated different chemically modified and unmodified natural and synthetic HA with carbon-13 of natural abundance. In addition, we studied carbon-13 labeled modified synthetic HA, that were synthesized with [13C]diazomethane as methylation reagent, to confirm the assumed modification process and to determine the type of functional groups that have the highest affinity for methylation.
The results of the NMR studies with carbon-13 labeled HA show that carboxyl and acidic (phenolic) OH groups are methylated with diazomethane. Due to the alkaline saponification of the methylated HA, methyl esters of carboxyl groups are hydrolyzed, whereas phenolic OH groups remain methylated. Carboxyl groups show the highest affinity for methylation.
From the spectra of the modified and unmodified HA with carbon-13 of natural abundance it can be concluded that the applied modification procedure causes only the desired structural changes in HA.
Keywords: Humic Acid, Modification, 13C-CP/MAS-NMR Spectroscopy, Carbon-13 Labeling
  • Talanta, 57, 999-1009 (2002)

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Permalink: https://www.hzdr.de/publications/Publ-3548
Publ.-Id: 3548


Synthese von Radiofluor-markiertem [18F]Perchlorylfluorid im pikomolaren Konzentrationsbereich

Jordanova, A.; Steinbach, J.
Die bildgebende Darstellung funktioneller Vorgänge im lebenden Organismus bei gleichzeitiger Möglichkeit ihrer Quantifizierung ist nur mittels der Positronen-Emissions-Tomographie möglich. Dazu ist die Entwicklung und Anwendung von Radiotracern erforderlich, die mit Positronen emittierenden Radionukliden markiert sind. Das entsprechende Radionuklid mit den günstigsten kernphysikalischen Eigenschaften ist Fluor-18 (Halbwertszeit 110 min)[1]. Eine spezielle Aufgabenstellung ist die Darstellung von Rezeptorarealen, die nur in sehr niedrigen absoluten Stoffmengen vorliegen, weshalb auch der Radiotracer in sehr niedrigen Konzentrationen eingesetzt werden muss. Dementsprechend müssen Fluor-18 - markierte Verbindungen mit einer sehr hohen molaren Aktivität (spez. Aktivität) zum Einsatz kommen. Dies bedeutet ein sehr kleines Verhältnis zwischen den identischen fluorierten Molekülen, die mit nicht-radioaktivem Fluor und Fluor-18 versehen sind.
Anwendungsgebiete sind in der Nuklearmedizin und die Anwendung von deren Methoden in der Pharmakaentwicklung sowie biochemischen Grundlagenforschung.

Der Fluorierungsschritt, die Markierung mit Fluor-18, ist bei der Synthese solcher Radiotracer von besonderer Wichtigkeit.
Zunehmendes Interesse haben Verbindungen, bei denen das Fluoratom an elektrophile Gruppen gebunden ist. Die elektrophile Einführung von Fluor-18 in entsprechende Moleküle wurde bisher stets ausgehend von [18F]F2 durchgeführt, wobei die Zugabe einer großen Menge an nicht-radioaktivem Fluor (10...100 µmol F2) erforderlich ist.

Bei der Suche nach einer Alternative zur Verwendung elementaren Fluors bieten sich elektrophile Fluorierungsmittel an, die ausgehend von [18F]Fluorid ohne Zusatz von nicht-radioaktiven Fluoriden hergestellt werden müssen [2].

Perchlorylfluorid FclO3 ist die einzige elektrophile Verbindung, die z.Zt. ausgehend von Fluorid, d.h. ohne die Verwendung elementaren Fluors, hergestellt werden kann. Ausgehend von Literaturdaten wurde eine Synthese erarbeitet die es gestattet, [18F]FclO3 ohne Trägerzusatz in Stoffmengen von ca. 50 nmol bei einem hohem Radioaktivitätsniveau herzustellen. Ausgangsprodukt ist stets wässrige [18F]HF- Lösung.

Die Umsetzung erfolgt nach Entfernung des Wassers unter streng wasserfreien Bedingungen als Eintopf-Reaktion. Die wasserfreie HclO4 wird durch Destillation durch P4O10 gewonnen, die HF-Lösung mittels Oleum entwässert.
Vorgehensweise: Wasserfreie HclO4 wird in ein Gemisch von Oleum/[18F]HF aqu. eindestilliert. Nach kurzer Wartezeit wird das entstandene [18F]FclO3 (Gl.1) in eine Vorlage abdestilliert, in der sich eine Lösung eines metalliertern Präkursors (Carbanionen in Form von Na-diethylmalonsäurediethylester oder Phenyllithium) befindet. Durch die Umsetzung mit diesen Substanzen (Gl.2, Gl.3) erfolgt gleichzeitig der Nachweis des gebildeten [18F]FclO3 unter Nutzung der Radio-HPLC.

[18F]HF + HClO4 _ _ [18F]FClO3 (1)
[18F]FClO3 + NaCH(COOEt)2 _ [18F]FCH(COOEt)2 (2)
[18F]FClO3 + C6H5Li _ [18F]C6H5F (3)

Der mögliche Mechanismus wird diskutiert.

Die bisher erreichte radiochemische Ausbeute liegt bei 6 % (zerfallskorrigiert). Damit können erstmals elektrophile Radiofluorierungen mit Fluor-18 ohne Trägerzusatz vorgenommen werden.

Literatur:
[1] Yu-Shin Ding, J. Fluorine Chem.101(2000) 291-295
[2] J. Steinbach, Chr. Fischer, K. Neubert, B. Johannsen, XIIth International Symposium on Radiopharmaceutical Chemistry,
Uppsala, Sweden, June 15-19, 1997, Abstracts S. 14-16

  • Lecture (Conference)
    Deutsche Fluortage, Schmitten/Taunus, 24.-27.09.2000

Permalink: https://www.hzdr.de/publications/Publ-3547
Publ.-Id: 3547


Phase transformations in nitrogen implanted iron layers

Jagielski, J.; Kopcewicz, J.; Matz, W.; Grötzschel, R.; Thomé, L.
It has been found that phase transformations in implanted iron may strongly depend on the sample thickness. The effect essentially relies on lower impurity concentration required for given phase formation in thin films when compared with thick layers or bulk samples and most likely should be attributed to the stress formed during layer deposition. The phase transformation in thin films is also more complete, for example full transformation of thin iron layers into iron nitrides was observed, whereas in thick and bulk samples about 20 % of Fe atoms in implanted layer remain in crystalline alpha-Fe phase.
  • Lecture (Conference)
    IBMM 2000 conference, Porto Alegre, Brazil, 2-6 September 2000
  • Nuclear Instruments and Methods in Physics Research B 175-177 (2001) 448-452

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Permalink: https://www.hzdr.de/publications/Publ-3546
Publ.-Id: 3546


Influence of thermal treatment and cyclic plastic deformation on the defect structure in ultrafine-grained nickel

Thiele, E.; Bretschneider, B.; Hollang, L.; Schell, N.; Holste, C.
Ultrafine-grained (UFG) high purity nickel samples produced by equichannel angular pressing were submitted to thermal treatment and cyclic plastic deformation at different temperatures in order to investigate the stability of the defect structure. After annealing recrystallization already occurs in a temperature range between 425K - 475K. Impurities increase the recrystallization temperature. At room temperature cyclic plastic deformation induces a coarsening of grains and subgrains and at 425K a dynamic recrystallization. Additionally , the mean volume expansion, long-range and short-range internal strains, investigated by synchrotron radiation diffraction for the UFG deformation stage are diminished in consequence of cyclic plastic deformation.
Keywords: ultrafine-grained nickel, synchrotron X-ray diffraction, diffraction profile analysis, internal strains and stresses
  • Contribution to HZDR-Annual report
    Investigations and Applications of Severe Plastic Deformation, Proceedings of NATO Advanced Research Workshop, T.C. Lowe and R.Z. Valiev (eds.), Moscow, 2-6 August 1999; Kluwer Academic Publishers, 2000, 173-178.

Permalink: https://www.hzdr.de/publications/Publ-3545
Publ.-Id: 3545


Kalorimetrische und FTIR-Untersuchungen zur sicheren Betriebsführung einer Grignardreaktion

Hessel, G.; Hulzer, G.; Kryk, H.; Schmitt, W.
Für die Bewertung des Gefahrenpotentials bei der Herstellung von Grignard-Reagenzien sind neben der sehr hohen Exothermie der Grignard-Reaktionen vor allem deren spontanes Startverhalten von entscheidender Bedeutung. Um Störfälle in industriellen Chemieanlagen zu vermeiden, darf ein Reaktionsstart nicht mehr bei einer hohen Akkumulation des Arylhalogenids erfolgen. Zu diesem Zweck werden die reaktions-technischen Parameter des Startprozesses am Beispiel einer häufig industriell angewendeten Grignard-Reaktion in einem geschlossenen Reaktionskalorimeter untersucht. Die Ergebnisse zeigen, dass neben online-FTIR-Konzentrationsmessungen auch der Anstieg der Reaktortemperatur und des Druckes zur Überwachung des Startens der Grignard-Reaktion genutzt werden können.
  • Poster
    5. Fachtagung "Anlagen-, Arbeits- und Umweltsicherheit", Köthen 9./10. Nov. 2000, S. 347-352
  • Contribution to proceedings
    5. Fachtagung "Anlagen-, Arbeits- und Umweltsicherheit", Köthen 9./10. Nov. 2000, S. 347-352

Permalink: https://www.hzdr.de/publications/Publ-3543
Publ.-Id: 3543


Investigations on exothermic semi-batch reactions as a basis of the prevention of dangerous operating states

Kryk, H.; Hessel, G.; Schmitt, W.; Seiler, T.; Willms, T.
The aim of the presentation is to give an overview of the equipment and the experimental activities of the Dep. of Experimental Fluid Dynamics relating to the investigations on exothermic chemical processes.
The experimental equipment consists of several reaction calorimeters, analytical instruments and a modular computer controlled miniplant.
With the help of this equipment a number of processes were investigated on the basis of industrial contracts and research projects.
The research results are presented with two examples:
- the calorimetric investigations of the formation of Grignard reagents
- the characterization of reaction pathways and process kinetics of the catalytic hydrogenation process of a special nitroaromatic compound.
The presentation ends with an outlook onto research activities of the Dep. of Experimental Fluid Dynamics in the near future.
  • Lecture (Conference)
    Fall 2000 DIERS Users Group meeting, October 16-18, 2000,Brookline (Boston), MA, USA

Permalink: https://www.hzdr.de/publications/Publ-3542
Publ.-Id: 3542


Verifikation des ATHLET-Rechenprogrammes anhand der Nachanalyse zweier Experimente an der CCTF-Versuchsanlage

Krepper, E.; Schäfer, F.
Im Rahmen der externen Validierung des von der Gesellschaft für Anlagen- und Reaktorsicherheit entwickelten Störfallcodes ATHLET, der in der Version Mod 1.2 Cycle C vorlag, wurden zwei Experimente nachgerechnet und analysiert, die an der japanischen Versuchsanlage CCTF durchgeführt wurden.
Die Versuchsanlage CCTF ist ein 1:25 volumenskaliertes Modell eines 1000 MW Druckwasserreaktors. Bei den Experimenten handelt es sich um die Versuche C2-04/62 und C2-19/79, in denen jeweils ein 2F-Bruch im kalten Strang mit kaltseitiger bzw. kombinierter Notkühleinspeisung simuliert wurde. Die Versuchsanlage wurde so ausgelegt, daß die Wiederfüll- bzw. Wiederflutphase bei Druckwasserreaktor-Störfällen mit großem Leck simuliert werden kann.
Die Auswertung der Rechnungen zeigt, daß die wesentlichen Phänomene im Verlauf der Transiente gut wiedergegeben werden. Das betrifft vor allem das zeitliche Verhalten der Wiederbenetzungsfront und die damit verbundene Kühlung der Brennelemente. Wie eine Analyse der experimentellen Daten zeigt, spielen im Reaktorkern radiale Effekte eine wesentliche Rolle. In der CCTF Anlage wird sowohl eine axiale als auch eine radiale Leistungsverteilung im Kern simuliert. Radiale Effekte treten insbesondere bei der kombinierten Notkühleinspeisung auf. Hier wird die Einspeisung über das Obere Plenum durch den in Gegenrichtung strömenden Dampf teilweise behindert. Die Wiederbenetzungsfront schreitet in den Randbereichen schneller voran als im Zentrum. Dieses Verhalten wurde in den ATHLET-Rechnungen durch eine Zweikanal-Modellierung des Reaktorkerns nachgebildet. Die Ergebnisse der ATHLET Rechnungen zeigen sowohl für das Zentrum als auch für die Randbereiche des Kerns eine gute Übereinstimmung mit den experimentellen Daten.
Die Schwachstellen der Rechnungen liegen vor allem bei der Notkühleinspeisung in der Anfangsphase der Transiente. Hier wird kaltes Notkühlwasser in Volumina mit reinem Dampf eingespeist. Die Rechnungen liefern dabei zu hohe Kondensationsraten, welche mit einer unrealistischen Druckabsenkung verbunden sind. Desweiteren wird der Druckaufbau durch die Verdampfung beim Wiederbenetzen der Brennelemente offensichtlich unterschätzt.
Die Ergebnisse der Rechnungen zeigen darüberhinaus, daß die sicherheitsrelevanten Aussagen der Experimente durch den Code ATHLET reproduziert werden.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-315 März 2001

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Permalink: https://www.hzdr.de/publications/Publ-3541
Publ.-Id: 3541


Mass separated Focused Ion Beams using alloy Liquid Metal Ion Sources

Bischoff, L.; Akhmadaliev, C.; Teichert, J.
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: Focused Ion Beam, Alloy Liquid Metal Ion Source, Mass Separation
  • Lecture (Conference)
    4th European FIB Users Group Meeting (EFUG2000), October 2 , 2000, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-3540
Publ.-Id: 3540


Linearization approaches in VGF models: decoupling global radiation transfer and the Stefan problem

Grants, I.; Gerbeth, G.; Pätzold, O.; Wunderwald, U.; Jenkner, K.
Simplified theoretical models are presented for the highly coupled phenomena of heat transfer, convection and solidification during VGF crystal growth. The models are essential in order to inverse the general approach: optimal conditions at the solidification front can be translated into temperature conditions at the heaters and the corresponding heater regimes. The Stefan problem of the unknown geometry of the solidification front is solved in a simplified analytical way in good approximation with the full numerical solution.
  • Lecture (Conference)
    DGKK-Jahrestagung, Freiberg, 11-12.10.2000

Permalink: https://www.hzdr.de/publications/Publ-3539
Publ.-Id: 3539


Magnetic field self-excitation in the Riga dynamo experiment

Gerbeth, G.; Stefani, F.; Gailitis, A.; Lielausis, O.; Platacis, E.
The theory of magnetic field generation in cosmic bodies due to the homogeneous dynamo effect has been widely elaborated during the last decades. However, an experimental verification of this effect was still missing until recently. At the Riga dynamo facility, self-excitation of a magnetic field in a liquid metal flow has been observed for the first time in November 1999. For increasing rotation rate of the driving propeller, the amplification of an applied magnetic field has been measured. At the highest rotation rate of 2150 rpm, an exponentially increasing 1.3 Hz signal has been detected on the background of the amplified 1 Hz signal. Additionally, after switching off the excitation current at a slightly lower rotation rate, a slowly decreasing eigenmode was observed. The results are shown to correspond convincingly with numerical predictions.
  • Lecture (Conference)
    ICTAM 2000, 20th Int. Congress of Theoretical and Applied Mechanics, Chicago, USA, 27.8.-2.9.2000

Permalink: https://www.hzdr.de/publications/Publ-3538
Publ.-Id: 3538


Cathodic arc deposition of nanoscale multilayers: experiments and computer simulations

Chun, S. Y.; Chayahara, A.; Horino, Y.; Posselt, M.; Möller, W.
Informations can be requested. Email: M.Posselt@fz-rossendorf.de
  • Poster
    12th International Conference on Ion Beam Modification of Materials, Canela, Brazil, September 3-8, 2000

Permalink: https://www.hzdr.de/publications/Publ-3537
Publ.-Id: 3537


Untersuchung der Kühlmittelvermischung in Druckwasserreaktoren

Höhne, T.
Ein wichtiges Thema der Sicherheitsforschung zum Störfallverhalten von Druckwasserreaktoren sind Reaktivitätsstörfälle. Beispiele für solche Transienten sind Lecks im Frischdampfsystem und Borverdünnungstransienten. Wenn zu kaltes Wasser oder Wasser mit einer zu geringen Borkonzentration in den Reaktorkern gelangt, kann es zu einem so hohen Reaktivitätseintrag kommen, dass der abgeschaltete unterkritische Reaktor wieder kritisch wird. Einerseits kann es bei einem Leck auf der Dampferzeuger-Sekundärseite zu einer Unterkühlung des Kühlwassers auf der Primärseite in dem entsprechenden Loop kommen. Die Unterkühlung kann bis zu 100 K gegenüber der normalen Kereintrittstemperatur betragen. Andererseits besteht die Möglichkeit, dass sich bei einem kleinen bis mittleren Leck im Primärkreis bei teilweisen Ausfall der HD-Notkühlung und Reflux-Condenser-Bedingungen Kondensat in den Dampferzeuger-Kollektoren und den Pumpenbögen ansammelt. Nach dem Wiederauffüllen des Kreislaufes und Anlauf der Kühlmittelzirkulation würde unterboriertes Wasser in den Kern gelangen. Ob der zuvor abgeschaltete Reaktor wieder kritisch wird und wie hoch die Leistungsspitze dabei ist, hängt davon ab, wie weit sich das kalte oder zu schwach borierte Wasser auf dem Wege von den Kühlschleifen durch den Ringraum und das untere Plenum zum Reaktorkern mit dem heißeren und hochborierten Kühlmittel im Reaktor vermischt. Aus diesem Grunde werden an der ROCOM-Versuchsanlage im Institut für Sicherheitsforschung des FZR generische Vermischungsuntersuchungen durchgeführt. Sie dienen vorrangig der Validierung von CFD-Berechungen zur Simulation der verschiedenen Vermischungsszenarien.
  • atw 12, S. 774-775

Permalink: https://www.hzdr.de/publications/Publ-3536
Publ.-Id: 3536


Doubly-charged ions from liquid metal ion sources: direct field-evaporation or post-ionization

Mair, G. L. R.; Ganetsos, T.; Bischoff, L.; Teichert, J.
We investigate the temperature dependence of the mass spectrum of the ion beam emitted by an Au77Ge14Si9 liquid metal alloy ion source. Our results strongly point towards the co-existance of two mechanisms for the emission of doubly-charged monomer ions: direct field evaporation and post-ionization.
Keywords: liquid metal alloy ion source, mass spectra, emission mechanism, field evaporation post-ionization
  • Journal of Physics D: Applied Physics; 33 (2000) L86 - L89

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Permalink: https://www.hzdr.de/publications/Publ-3535
Publ.-Id: 3535


Defects remaining in Si after MeV ion implantation and annealing away from the peak of the nuclear energy deposition profile

Kögler, R.; Skorupa, W.; Yankov, R. A.; Posselt, M.; Danilin, A. B.
Informations can be requested. Email: M.Posselt@fz-rossendorf.de
  • Contribution to external collection
    Proc. 1998 Int. Conf. on Ion Implantation Technology, Kyoto, Japan, June 22-26, 1998, eds.: J. Matsuo, G. Takaoka, Y. Yamada; IEEE, Piscataway, USA, 1998, IEEE Publications 98EX144, p. 1117

Permalink: https://www.hzdr.de/publications/Publ-3534
Publ.-Id: 3534


Defect production and evolution during and after ion implantation studied by a combination of time-ordered BCA and MD simulations

Posselt, M.
Informations can be requested. Email: M.Posselt@fz-rossendorf.de
  • Contribution to external collection
    Proc. 1998 Int. Conf. on Ion Implantation Technology, Kyoto, Japan, June 22-26, 1998, eds.: J. Matsuo, G. Takaoka, Y. Yamada; IEEE, Piscataway, USA, 1998, IEEE Publications 98EX144, p. 678

Permalink: https://www.hzdr.de/publications/Publ-3533
Publ.-Id: 3533


Atomistic simulation of ion implantation into different polytypes of SiC

Ster, A.; Posselt, M.; Hallen, A.; Janson, M.
Informations can be requested. Email: M.Posselt@fz-rossendorf.de
  • Poster
    13th International Conference on Ion Implantation Technology, Alpbach, Austria, September 17-22, 2000
  • Contribution to external collection
    Proc. 2000 Int. Conf. on Ion Implantation Technology, Alpbach, Austria, September 17 -22, eds.: H. Ryssel, L. Frey, J. Gyulai, H. Glawischnig, IEEE, Piscataway, USA, 2000, IEEE Publications 00EX432, p. 220

Permalink: https://www.hzdr.de/publications/Publ-3532
Publ.-Id: 3532


Development and calibration of physical models for processes relevant to deep submicron technologies

Erlebach, A.; Benistant, F.; Krause, U.; Matveev, D.; Strecker, N.; Meniailenko, V.; Mickevicius, R.; Simeonov, S.; Al-Bayati, A.; Tandon, S.; Gallo, B.; Foad, M. A.; Ng, B.; Trowbridge, T.; Posselt, M.
Informations can be requested. Email: M.Posselt@fz-rossendorf.de
  • Lecture (Conference)
    13th International Conference on Ion Implantation Technology, Alpbach, Austria, September 17-22, 2000

Permalink: https://www.hzdr.de/publications/Publ-3531
Publ.-Id: 3531


Application of indium ion implantation for halo doping: experimental and simulation results for advanced CMOS devices

Variam, N.; Jeong, U.; Falk, S.; Mehta, S.; Posselt, M.; Feudel, T.; Horstmann, M.; Krüger, C.; Ng, C.-H.
Informations can be requested. Email: M.Posselt@fz-rossendorf.de
  • Lecture (Conference)
    13th International Conference on Ion Implantation Technology, Alpbach, Austria, September 17-22, 2000
  • Contribution to external collection
    Proc. 2000 Int. Conf. on Ion Implantation Technology, Alpbach, Austria, September 17 -22, eds.: H. Ryssel, L. Frey, J. Gyulai, H. Glawischnig, IEEE, Piscataway, USA, 2000, IEEE Publications 00EX432, p. 42

Permalink: https://www.hzdr.de/publications/Publ-3530
Publ.-Id: 3530


Defect formation and evolution in Si within the first nanosecond after ion impact

Posselt, M.
Informations can be requested. Email: M.Posselt@fz-rossendorf.de
  • Invited lecture (Conferences)
    5th International Conference on Computer Simulation of Radiation Effects in Solids, Penn State University, State College, USA, July 24-28, 2000 (invited talk)

Permalink: https://www.hzdr.de/publications/Publ-3529
Publ.-Id: 3529


Magnetic Field Saturation in the Riga Dynamo Experiment

Gailitis, A.; Lielausis, O.; Platacis, E.; Dement'Ev, S.; Cifersons, A.; Gerbeth, G.; Gundrum, T.; Stefani, F.; Christen, M.; Will, G.
After the dynamo experiment in November 1999 had shown magnetic field self-excitation in a spiraling liquid metal flow, in a second series of experiments emphasis was placed on the magnetic field saturation regime. The dependence of the strength of the magnetic field on the rotation rate is studied. Various features of the saturated magnetic field are outlined and possible saturation mechanisms are discussed.
  • Physical Review Letters 86 (2001) 3024-3027

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Permalink: https://www.hzdr.de/publications/Publ-3528
Publ.-Id: 3528


MBE-grown GaAs/AlGaAs and strained InGaAs/AlGaAs/GaAs quantum cascade lasers

Strasser, G.; Gianordoli, S.; Schrenk, W.; Gornik, E.; Mücklich, A.; Helm, M.
We demonstrate the realization of a quantum cascade laser (QCL) based on strained InGaAs/AlGaAs/GaAs grown on GaAs substrate using molecular beam epitaxy. The material is compared to a GaAs/AlGaAs structure with nominally identical radiative transitions. Lasing at 10 microns was achieved in the strained and the unstrained material. The strained material shows an improved temperature performance with a T0=112K between 125 K and 200 K and a maximum working temperature of T=200 K.
Keywords: quantum cascade laser, infrared laser, unipolar laser, intersubband laser, strained InGaAs
  • Journal of Crystal Growth 227-228 (2001) 197-201

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Publ.-Id: 3527


RES3T-Rossendorf Expert System for Surface and Sorption Thermodynamics

Brendler, V.; Arnold, T.; Bernhard, G.; Fanghänel, T.
This paper presents a digitized version of a thermodynamic sorption database, implemented as a relational database with MS Access. It is mineral-specific and can therefore also be used for additive models of more complex solid phases such as rocks or soils. An integrated user interface helps users to access selected mineral and sorption data, to extract internally consistent data sets for sorption modeling, and to export them into formats suitable for other modeling software. Data records comprise of mineral properties, specific surface area values, characteristics of surface binding sites and their protolysis, sorption ligand information, and surface complexation reactions. An extensive bibliography is also included, providing links not only to the above listed data items, but also to background information concerning surface complexation model theories, surface species evidence, and sorption experiment techniques.
  • Journal of Contaminant Hydrology (2003)61, 281-291

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Publ.-Id: 3526


A Study of Positron Properties in Quartz Crystals and Synthetic Silica Glass

Anwand, W.; Brauer, G.; Hasegawa, M.; Dersch, O.; Rauch, F.
The monoenergetic positron beamline ‚SPONSOR' at Rossendorf has been used to investigate the positron behaviour in a naturally grown Brasilian quartz, two synthetic quartz crystals of different origin, and synthetic silica glass. The measurements allow to obtain the positron diffusion length of free positrons and Bloch para-positronium (p-Ps), if formed, in these materials.
In addition, hydrothermal treatment of a synthetic quartz has been used to introduce hydrogen into the crystal up to a certain depth. The presence of hydrogen is found to influence the formation of p-Ps. The depth distribution of hydrogen has been measured independently by nuclear reaction analysis (NRA), and will be discussed in comparison with the depth results deduced from the positron studies.
  • Acta Physica Polonica A 99 (2001) 321-328
  • Lecture (Conference)
    32nd Polish Seminar on PositronAnnihilation, Jarnoltowek, Poland, September 18-22, 2000

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Nutzung der Rauschdiagnostik für Nachweis und Überwachung der Schwingungen von Reaktordruckbehältereinbauten und zur Aufklärung ihrer Ursachen in ostdeutschen Kernkraftwerken mit WWER-440/230-Reaktoren der russischen Baureihe

Schumann, P.
Im vorliegenden Bericht werden Anwendung und Ergebnisse rauschdiagnostischer Untersuchungen von Schwingungen, die zu Beschädigungen der Einbauten des Reaktordruckgefäßes geführt haben, im Detail beschrieben. Sie waren in den Jahren 1975 bzw. 1985 an den WWER-440/230-Reaktoren der russischen Baureihe der Blöcke 1 und 2 des Kernkraftwerkes Greifswald aufgetreten. Der Bericht enthält die wesentlichen Angaben zum Betriebsverhalten während des gestörten Betriebes, die Inspektionsergebnisse, die charakteristischen experimentellen Befunde unter Verwendung rauschdiagnostischer Analysemethoden, die physikalische Aufklärung des Schwingungsprozesses und seiner Ursachen durch spezielle Untersuchungen sowie einige Empfehlungen zur Schwingungsüberwachung und -minimierung.



  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf, FZR-304 Oktober 2000

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Publ.-Id: 3524


Improvement of the High Temperature Oxidation Behaviour of TiAl Alloy by Cl Implantation using PIII

Hornauer, U.; Günzel, R.; Richter, E.; Wieser, E.; Möller, W.; Schumacher, G.; Dettenwanger, F.; Schütze, M.
The intermetallic compound TiAl is very interesting for high temperature application due to its high temperature strength and low density. Above 700 °C, the use in e.g. aircraft engines is hindered because of a low oxidation resistance. Even though the compound contains 50at% Al, this is not sufficient to form a protective Al2O3 scale. Instead, a mixed oxide scale composed of TiO2 and Al2O3 is formed. Extended alloy development has shown, that additional elements which are beneficial for the oxidation often have a bad influence on the mechanical bulk properties. Cl doping has a strong effect even in very low concentrations of about 500 ppm ("Microalloy"). Ion Implantation of 1016 Cl/cm2 protects TiAl at 900 °C for up to 1000 h against oxidation in a wide range of implantation energies.

In order to apply this effect for complicated shaped parts, the high temperature oxidation behavior after plasma immersion ion implantation of chlorine into different TiAl alloys was investigated. A specialized chamber has been setup up for the strongly etching Cl plasma. Particularly with regard to contaminations, the chamber and the RF- antenna had to be made from aluminum. Since it is known that the Cl effect in TiAl requires a well defined Cl concentration, a variation of the implantation parameters has been performed. The resulting depth profiles of Cl are investigated using depth profiling with Auger electron spectroscopy (AES). After treatment (3*105 to 3*106 30 kV pulses of 5µs at a repetition rate from 150 Hz to 1500 Hz), the Cl is located close to the surface. The process is governed by the interplay between etching and implanting during the HV pulses. Therefore the retained dose depends mainly on the temperature during implantation, which is controlled by the repetition rate of the pulses. Oxidation tests at 900°C in air for 100 h showed a strong reduction of the oxidation, which are comparable to conventional beam line im-plantations of Cl.
  • Lecture (Conference)
    PSE 2000, Garmisch Partenkirchen, Germany, 17-21.9.2000

Permalink: https://www.hzdr.de/publications/Publ-3523
Publ.-Id: 3523


Bewertung der Genauigkeit eines Gittersensors zur Visualisierung einer Zweiphasenströmung durch Vergleich mit optischen Hochgeschwindigkeitsaufnahmen

Scholz, D.
In der Energie- und der Verfahrenstechnik spielen Zweiphasenströmungen eine wichtige Rolle. Sie treten in Rohrleitungen und Apparaten auf, und beeinflussen dort chemische Reaktionen, sowie Wärme- und Stoffübergänge. Um die komplexen Vorgänge in den Zweiphasenströmungen modellieren zu können, bedarf es der Ergebnisse umfangreicher Experimente. Zur Ermittlung der charakterisierenden Parameter einer Zweiphasenströmung, wie die Phasenverteilung und die Strömungsgeschwindigkeiten, ist eine Messtechnik notwendig, die eine räumlich und zeitlich hochaufgelöste Visualisierung der Strömung ermöglicht. Für diese Aufgabe eignen sich bspw. konduktive Messverfahren.

Im Institut für Sicherheitsforschung des FZ Rossendorf wurde in den vergangenen Jahren ein Gittersensor zur Untersuchung von Zweiphasenströmungen entwickelt. Dieser basiert auf der Messung der momentanen lokalen elektrischen Leitfähigkeit des Zweiphasengemischs. Er ermöglicht eine hochaufgelöste Visualisierung der Strömung. Bei einer Reihe unterschiedlicher Experimente wurde die Anwendbarkeit des Gittersensors zur Ermittlung der Phasenverteilung in einer Zweiphasenströmung nachgewiesen.

In dieser Arbeit soll die Genauigkeit des Gittersensors bei der Ermittlung von Blasengrößen untersucht werden. Dafür wurde ein Plexiglaskanal angefertigt, in den die Elektroden des Sensors direkt eingebaut wurden. Da es nicht möglich war, für einen Vergleich in der Kanalströmung einzelne Blasen mit einem definierten Volumen zu erzeugen, wurde die Bewegung der Blasen in diesem Kanal mit einer Hochgeschwindigkeits-Videoeinrichtung erfasst. Mit beiden Verfahren wurden synchron Messungen bei unterschiedlichen Strömungsgeschwindigkeiten und mit verschiedenen Blasenvolumen durchgeführt. Mit Hilfe von Rechnerprogrammen wurden aus den Kamerabildern die Durchmesser der Blasen bestimmt und daraus die Volumen berechnet. Damit konnten die ermittelten Blasenvolumen des Gittersensors mit denen der Kameraaufnahmen verglichen werden. Dieser Vergleich ließ qualitative und teilweise quantitative Aussagen über die Genauigkeit des Gittersensors zu.

Keywords: Gittersensor, Hochgeschwindigkeitsaufnahmen
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-300 September 2000

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Publ.-Id: 3522


Experimental Investigations on the Four-Loop Test Facility ROCOM

Höhne, T.; Grunwald, G.; Prasser, H.-M.
For the analysis of the core behaviour during boron dilution transients and main steam line breaks, coupled neutron kinetic / thermal hydraulic codes are necessary. These codes (e.g. DYN3D-ATHLET) must contain models of the coolant mixing on its way from the inlet noz-zles to the core entrance, because the reactivity insertion strongly depends on the distribution of temperature and boron concentration at the core inlet. The coolant mixing mainly happens in the three-dimensional flow field inside the complex geometry of the downcomer and lower plenum. The modelling of coolant mixing was carried out by detailed computational fluid dynamics (CFD) calculations with the code CFX 4.3. For the validation of the computational results, the ROCOM test facility was built, a fluid dynamic 1:5 scaled model of the Konvoi reactor. The reactor vessel is made of Plexiglas for flow visualisation and LDA measure-ments. The use of a system of wire-mesh sensors allows to measure salt concentrations at over 1000 locations with a maximum time resolution of 200 Hz. In case of stationary coolant flow in all loops a disturbance of boron concentration or temperature is transferred to a sector of the core inlet plane, which corresponds to the location of the inlet nozzle. A short plug of boron diluted water experiences a better mixing: due to the vortices in the downcomer different por-tions of the disturbance are transported with different velocities. This causes a dispersion of the front and the end of the plug (axial mixing). Further, experiments and calculations are go-ing on to investigate mixing under transient conditions (start of circulation).
  • Kerntechnik 65/5-6, S. 212-215

Permalink: https://www.hzdr.de/publications/Publ-3521
Publ.-Id: 3521


Surface Processes and Diffusion Mechanisms of Ion Nitriding of Stainless Steel and Aluminium

Möller, W.; Parascandola, S.; Telbizova, T.; Günzel, R.; Richter, E.
Model experiments with low-energy ions under controlled vacuum conditions have been performed in order to identify the surface processes and the diffusion mechanism associated with the nitrogen transport during ion nitriding of stainless steel 316 and pure aluminium. A necessary condition for an efficient nitriding is the transmission of the implanted ions through a surface oxide layer which results from a balance of ion sputtering and re-oxidation from the residual gas. For ion energies around 1 keV and ion current densities around 0.2 mA/cm2, oxygen partial pressures of less than about 3A10-6 mbar and 3A10-7 mbar are required for stainless steel and aluminium, respectively. Diffusion under the influence of traps controls the transport of nitrogen in stainless steel, with dynamic trapping at the Cr atoms of the alloy. In contrast, stoichiometric AlN grows on aluminium due to Al diffusion from the underlying bulk. From the surface and diffusion mechanisms, limitations of plasma nitriding and plasma immersion ion nitriding are derived, and the implications for industrial applications are discussed.

Keywords: Nitriding, Ion Implantation, Diffusion, Plasma Immersion, Wear Reduction
  • Surface and Coatings Technology 136 (2001) 73 - 79

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Publ.-Id: 3520


Synthesis and characterization of novel trigonal-bipyramidal technetium(III) mixed-ligand complexes with SES/S/P coordination (E = O, N(CH3), S)

Pietzsch, H.-J.; Tisato, F.; Refosco, F.; Leibnitz, P.; Drews, A.; Seifert, S.; Spies, H.
Five-coordinate oxotechnetium(V) mixed-ligand complexes [TcO(SES)(S-p-C6H4-OMe)], where SES is a tridentate dithiolato fragment of the type -S(CH2)2E(CH2)2S- (E = O, 1; E = S, 2; E = NMe, 3) are converted via reduction-substitution reactions in the presence of PMe2Ph into the corresponding five-coordinate Tc(III) complexes [Tc(SES)(S-p-C6H4-OMe)(PMe2Ph)] (E = O, 4; E = S, 5; E = NMe, 6). Rearrangement of the original square pyramidal '3 + 1' oxo-species to the trigonal bipyramidal '3+1+1' Tc(III) complexes occurs by placing the three thiolate donors on the basal plane, the phosphine phosphorus and the heteroatom of the tridentate ligand at the apexes of the bipyramid. These Tc(III) complexes are diamagnetic species, thereby allowing multinuclear NMR characterization in solution, which confirm their structures to be identical to those observed in the solid state via X-ray determinations.
Keywords: Oxotechnetium(V) complexes, Tc(III) mixed ligand complexes, NMR spectroscopy, cyclic voltammetry, X-ray structural analysis
  • Inorg. Chem. 40 (2001), 40, 59-64

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Publ.-Id: 3519


Transport of choline and carnitine at the blood-brain barrier in vitro

Friedrich, A.; Ganapathy, V.; Brust, P.
Introduction:
Choline is the metabolic precursor of neurotransmitter acetylcholine and of the membrane phospholipid phosphatidylcholine. This amine is not synthesized by the brain and is therefore taken up from the blood. It is transported by a specific transport system which is much less characterized than the transporter for glucose and amino acids. Carnitine which is important for the intracellular transport of fatty acids has been found to inhibit the choline transport. On the other hand specific transporters for carnitine are known (OCTN1, OCTN2) which have not been described at the blood-brain-barrier (BBB) up to know. Therefore we have studied the transport of the two amines at an in vitro model of the BBB. In this study, we have demonstrated that at least two different transport systems for choline and carnitine are functionally expressed.
Methods:
The RBE4 cell line was used as an in-vitro model of the BBB and it has been shown that these cells express typical BBB markers such as gamma-glutamyltransferase and alkaline phosphatase(1). Tracer uptake studies were performed in 24 multi-well plates using buffers containing either 25 mM Tris/Hepes (pH 8.5 for choline uptake) or 25 mM Hepes/Tris (pH 7.5 for carnitine uptake), supplemented with 0.5% albumin, 5 mM glucose, 5.4 mM KCl, 1,8 mM CaCl2, 0.8 mM MgSO4 and 140 mM NaCl. Whenever Na+-free buffers were used, NMDG chloride replaced NaCl isoosmotically. Cells were washed before starting the uptake and then incubated at room temperature (choline uptake) or 37°C (carnitine uptake) with radiolabeled substrates added to the incubation buffer. Km values and Vmax values were calculated from the uptake data. Specific inhibitors of the transporters were added to the incubation buffer to study the specificity of the process.
An RBE4 cell cDNA library was constructed using the Superscript plasmid system. This plasmid cDNA library, grown on NitroPure transfer membranes, was screened by the colony screening method as described by Vogeli and Kaytes (2). The cDNA probe used for screening was 2.1 kb pair long and consisted of most of the coding region of rOCTN2 cDNA. The probe was labeled with [alpha-32P]dCTP using the ready-to-go oligolabeling kit, and used to screen the RBE4 cDNA library under low stringency conditions. The cDNA was functionally expressed in HeLa cells by vaccinia virus expression system (3). Transport measurements were made at room temperature using the same uptake buffer as described above without albumin.
Results:
The RBE4 cells express a Na+-independent choline transporter. Hemicholinium, an inhibitor for the Na+-dependent choline transporter, also inhibits the choline uptake found in these cells while tetraethylammonium (TEA) does not. The uptake of choline is saturable with a Km value of 22 µM and a Vmax of 515 pmol/(mg protein * 10 min).
We also isolated a full-length OCTN2 clone from the RBE4 cDNA library. HeLa cells transfected with this clone express Na+-independent TEA uptake and Na+-dependent carnitine uptake. These transfected cells also take up fatty acid esters of carnitine like propionylcarnitine and acetylcarnitine. The Km value for the carnitine uptake at 37°C in RBE4 cells is about 50 µM. Specific inhibitors for the OCTN2 transporter (MPP+ and TEA) inhibit the carnitine uptake in RBE4 cells.
Comments:
In summary, we have found two separate transporters for choline and carnitine are expressed in the RBE4 cells. While the choline transporter is expected to supply the brain with choline for neurotransmitter synthesis OCTN2 is described as an carnitine carrier which also transports short fatty acids as carnitine esters through the cell membrane. The expression of OCTN2 at the BBB may help to understand the way of supplying the brain with acetyl groups for the synthesis of acetylcholine ...
  • Poster
    Symposium Signal Transduction in the Blood-Brain Barrier, Potsdam, 22.-24.9.2000

Permalink: https://www.hzdr.de/publications/Publ-3518
Publ.-Id: 3518


Influence of the bubble size distribution on radial gas fraction profiles in vertical pipe flow

Lucas, D.; Krepper, E.; Prasser, H.-M.
The paper presents a method for the prediction of the radial gas fraction profile in vertical pipe flow for a given bubble size distribution. A large number of bubble classes is considered. An equilibrium of the forces acting on a bubble perpendicular to the flow direction is assumed. On basis of the radial profile of the liquid velocity, radial distributions of the volume fraction are calculated separately for all bubble classes according to a given bubble size distribution. The sum of these distributions is the radial profile of the gas fraction. It again influences the liquid velocity. The final solution is obtained by an iteration process, which consideres the feedback between the gas fraction profile and the profile of the liquid velocity. The model is the basis of a fast running one-dimensional steady state computer code. The results of the model are compared with experimental data for a number of gas and liquid volume flow rates.
Keywords: Two-phase flow, Flow regime, Bubble flow
  • Lecture (Conference)
    Second Japanese-European Two-Phase Flow Group Meeting, Tsukuba, Japan, September 25-29, 2000, Proceedings on CD-ROM: K-2.pdf
  • Contribution to proceedings
    Second Japanese-European Two-Phase Flow Group Meeting, Tsukuba, Japan, September 25-29, 2000, Proceedings on CD-ROM: K-2.pdf

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Publ.-Id: 3517


Fast wire-mesh sensors for gas-liquid flows and decomposition of gas fraction profiles according to bubble size classes

Prasser, H.-M.; Krepper, E.; Lucas, D.
The wire-mesh sensor developed by the Forschungszentrum Rossendorf produces sequences of instantaneous gas fraction distributions in a cross section with a time resolution of 1200 frames per second and a spatial resolution of about 2-3 mm. At moderate flow velocities (up to 1-2 m/s), bubble size distributions can be obtained, since each individual bubble is mapped in several successive distributions. The method was used to study the evolution of the bubble size distribution in a vertical two-phase flow. For this purpose, the sensor was placed downstream of an air injector, the distance between air injection and sensor was varied. The bubble identification algorithm allows to select bubbles of a given range of effective diameter and to calculate partial gas fraction profiles for this diameter range. In this way, the different behaviour of small and large bubbles in respect to the action of the lift force was observed in a realistic flow situation.
Keywords: two-phase flow, wire-mesh sensor, gas fraction, bubble size, gas fraction profiles
  • Lecture (Conference)
    Second Japanese-European Two-Phase Flow Group Meeting, Tsukuba, Japan, September 25-29, 2000, proceedings on CD-ROM: D-3.pdf
  • Contribution to proceedings
    Second Japanese-European Two-Phase Flow Group Meeting, Tsukuba, Japan, September 25-29, 2000, proceedings on CD-ROM: D-3.pdf

Permalink: https://www.hzdr.de/publications/Publ-3516
Publ.-Id: 3516


Decel Lens System for Low-Energy Ion Implantation with High Dose Uniformity

Teichert, J.; von Borany, J.
In this paper we report on the design of a decel lens system for low energy ion implantation. The novel lens system consisting of a converging and a diverging lens in a compact arrangement allows to compensate the spherical aberration. Therefore implantation into large areas at low energies can be performed with high dose uniformity. The implantation chamber with the decel lens system is fitted to the beamline 2 of the medium energy implanter DANFYSIK 1090 at the Forschungszentrum Rossendorf. Using a beam energy of 30 keV the ions can be decelerated up to 2 keV with a dose uniformity of < 5% for 100 mm diameter.
Keywords: Ion Implantation, low-energy ion implantation, implantation chamber, implanter, deceleration lens, dose uniformity, decel lens system, electrostatic lens, spherical aberrration
  • Poster
    Proc. Int. Conf. on Ion Implantation Technology, Alpbach, Austria, Sept. 17 - 22, 2000
  • Contribution to external collection
    Proc. Int. Conf. on Ion Implantation Technology, Alpbach, Austria, Sept. 17 - 22, 2000

Permalink: https://www.hzdr.de/publications/Publ-3515
Publ.-Id: 3515


Structural investigation and wear resistance of submicron TiN coatings obtained by a hybride plasma immersion ion implantation Process

Günzel, R.; Shevshenko, N.; Matz, W.; Mücklich, A.; Celis, J.-P.
The ever increasing demands for high precision machining and increased cutting performance, in terms of cutting speed and lifetime, require wear resistant tools of large dimensional accu-racy that have very sharp cutting edges. All these requirements can not be fulfilled by the clas-sic PVD and CVD technologies because they result in rather thick overlay coatings.
In this report, first experiments are presented on a hybride plasma immersed ion implantation process (PIII) for depositing thin TiN coatings on hardened and annealed high speed steel or cemented carbides. The layers were produced using a dc-cathodic arc source with a titanium cathode and a nitrogen feed gas. As the cathodic arc generates additional to the metal plasma, a large amount of liquid metal droplets, the plasma was guided to the samples through a 900 magnetic bending field avoiding the deposition of droplets on the samples. The obtained layer thickness was below 1 µm for deposition times of 2 min.
To improve the adhesion of the deposited layers on the substrate materials, of energetic ions were used during the initial phase of the process. Hereto negative high voltage pulses in the range from zero to 5 kV have been applied to the samples during the deposition. The effect of the energy of these ions on the coating structure was also investigated by SEM, TEM and XRD. Mechanical and functional properties were investigated by hardness measurements and fretting wear tests respectively. Finally cutting performance tests of PIII-treated drills were performed, revealing that a 0.8µm thick TiN PIII-coating increased the lifetime of the drills by a factor of 2.5.

Keywords: cutting tools, coatings, ion implantation, PIII, TiN
  • Lecture (Conference)
    PSE2000, 17.-21.9. 2000, Garmisch-Partenkirchen, Deutschland
  • Surface & Coatings Technology 142-144 (2001) 978-983

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Publ.-Id: 3514


Correlation of vertical transport and infrared absorption in GaAs/AlGaAs superlattices

Helm, M.; Strasser, G.
We have studied the interminiband absorption and the current-voltage characteristics on the same GaAs/AlGaAs superlattices. The Esaki-Tsu type negative differential resistance is observed as well as the thermal (de)population of the minibands. The possibility of mapping the nonequilibrium electron distribution function through infrared absorption measurements under bias is discussed.
Keywords: GaAs, superlattice, infrared absorption, intersubband transition, vertical transport
  • Contribution to proceedings
    Proceedings 25th International Conference on the Physics of Semiconductors (ICPS-25, Osaka, Japan, 17-22 Sept. 2000); Ed. N. Miura & T. Ando, Springer (2001), p. 715

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Publ.-Id: 3513


In-situ Stress Diagnostics

Fukarek, W.; Fitz, C.
Stress is a common property of thin films. After a brief summary of origins and effects of stresses in thin films the particular situation in amorphous and nano-crystalline films is discussed. The problems related to the extremely high compressive stresses in cubic boron nitride (cBN) have been tackled either by the deposition of buffer layers or by attempts to reduce the stress in the film. These approaches are compared and discussed. Intrinsic stress depth profiles in BN films, as well as the influence of post-deposition thermal treatment and ion irradiation on the global stress, as obtained from in-situ cantilever bending measurements, are reviewed. A technique for the growth of cBN films with significantly reduced compressive stress is demonstrated.
Keywords: thin films, stress, boron nitride, IBAD, ion implantation
  • Surface and Coatings Technology 142-144 (2001) 868-873

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Publ.-Id: 3512


Ion Acoustic Microscopy for Imaging of Buried Structures Based on a Focused Ion Beam System

Akhmadaliev, S.; Bischoff, L.; Teichert, J.; Kazbekov, K.
An intensity modulated focused ion beam (FIB) which is hitting the surface of a solid, heats up a small near subsurface region to a temperature which is sufficient for thermal elastic wave generation. The measurement of these waves can be used for analysis and imaging of surface as well as subsurface structures in the material. The modified FIB equipment IMSA-100 working with 35 keV Ga+ and Au+ ions, respectively, and a current of about 3 nA was employed to obtain acoustic images from structures on silicon and glass targets. The acoustic signals were detected using a PZT transducer delivering an output voltage of 50 - 100 nV. The modulation frequency was varied in the range of 60 - 170 kHz. The obtained lateral resolution of the ion acoustic images at these frequencies was about 15 µm on silicon and about 7µm on glass, respectively. Furthermore some estimations due to the reachable resolution and a short description of the set-up is given.
Keywords: Focused Ion Beam, Ion Acoustic Microscopy, Piezoelectric Transducer
  • Lecture (Conference)
    Int. Conf. Micro- and Nano-Engineering 2000, MNE, September 18 - 21, 2000, Jena, Germany
  • Microelectronic Engineering 57-58 (2001) 659-664

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Publ.-Id: 3511


Structural characterisation of hardening of Ti-Al-V alloys after nitridation by plasma immersion ion implantation

Berberich, F.; Matz, W.; Kreissig, U.; Richter, E.; Schell, N.; Möller, W.
The surface hardness of the titanium alloy Ti-6Al-4V, widely used as construction material, can be improved by nitrogen implantation. The paper reports on a complex study of the structural mechanisms of hardening and its loss at higher temperatures with different methods (grazing incidence X-ray diffraction, in-situ high temperature diffraction with synchrotron radiation, ERDA, hardness and surface inspection by SEM). Plasma immersion ion implantation produces a nitrogen profile directly below the surface. The formation of small TiN crystallites is detected but the hardness increase is only about 40%. Annealing leads to the reduction of the TiN phase and the formation of Ti2N deeper in the material. The in-situ XRD study of the phase formation gives information about the temperature range of the changes. The hardness increases after annealing by a factor of 2.5 compared to the unimplanted state. It is explained by precipitation hardening due to the formation of titanium nitrides in different depths of the material.
Keywords: Ti-6Al-4V, plasma immersion ion implantation, XRD, hardness
  • Lecture (Conference)
    11. Arbeitstagung Angewandte Oberflächenanalyse (AOFA 11), Leipzig, 24.-28.9.2000
  • Applied Surface Science 179 (2001) 13-19

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Publ.-Id: 3510


In-situ Characterization of Thin Film Growth: Boron Nitride on Silicon

Fukarek, W.
Real-time ellipsometry (RTE) in combination with particle flux measurement is applied to ion beam assisted deposition (IBAD) of boron nitride (BN) films. RTE is used as a toll for process diagnostic to improve the deposition stability. A novel technique for the determination of absolute density depth profiles from dynamic growth rate data and film forming particle flux is employed. From real-time cantilever curvature measurement and simultaneously recorded film thickness data instantaneous stress depth profiles are derived with a depth resolution in the nm--range. The synergistic effects on the information obtained from RTE, particle flux, and cantilever bending data are demonstrated. The density of turbostratic BN (tBN) is found to increase slightly with film thickness while the compressive stress decreases, indicating an increasing quality and/or size of crystallites in the course of film growth. Refractive index and density depth profiles in cubic BN (cBN) films correspond perfectly to structural information obtained from dark field TEM graphs. The established tBN/cBN 2-layer model is found to be a crude approximation that has to be replaced by a 3-layer model including nucleation, grain growth, and coalescence of cBN. The instantaneous compressive stress in a homogeneous tBN film is found to decrease while the density increases during growth. The instantaneous compressive stress depth profiles in cBN films are more complex and not easy to understand but reliable information on the structural evolution during growth can be extracted.
Keywords: BN, ellipsometry, stress, density, IBAD
  • Journal of Vacuum Science and Technology A 19(4), Jul/Aug 2001

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Publ.-Id: 3509


Ermittlung zähbruchmechanischer Kennwerte unter schlagartiger Belastung mittels Schallemission

Richter, H.
Gegenstand der vorliegenden Arbeit ist die Weiterentwicklung von Verfahren zur Ermittlung der Rißeinleitungszähigkeit (Jid) unter schlagartigen Belastungsbedingungen. Als Indikationsmethode für die duktile Rißinitiierung wurde die Messung der unter Beanspruchung im Werkstoff freigesetzten elastischen Energie - der Schallemission (SE) - genutzt.

Die Eignung dieser Methode wurde im instrumentierten Kerbschlagbiegeversuch an modifizierten ISO-V-Proben geprüft. Als zuverlässige Basis für eine Beurteilung der damit bestimmten Kennwerte wird die physikalische Rißinitiierungszähigkeit angesehen. Dieser Referenzwert wird in Verbindung mit der Messung der Stretchzonenbreite aus der nach der Mehrpro-ben-Spaltbruchmethode ermittelten Rißwiderstandskurve gewonnen. Die Bestimmung des SE-definierten Initiierungswertes wurde mit zusätzlichen dynamischen Einprobenverfahren (Laser-COD, magnetische Emission) und ergänzenden Versuchsanordnungen (invertiertes Pendelschlagwerk, dynamischer Dreipunktbiegeversuch) verifiziert. Die Untersuchungen wurden an Stählen mit unterschiedlichen Festigkeits-Zähigkeitseigenschaften durchgeführt.

Die Ergebnisse lassen sich wie folgt zusammenfassen:
• Nach dem Aufprall des Hammers führen die rasch wechselnden Kontaktbedingungen zwischen Finne, Probe und Widerlager zu „schlagbedingter" SE, die frequenzselektiv nicht eliminiert werden kann. Geringfügige Änderungen der Kontaktgeometrie beeinflussen die schlagbedingte SE.
• Unabhängig von der verwendeten Versuchsanordnung (normal, invertiert) wurden grund-sätzlich vergleichbare SE-Signale erhalten.
• Neben der schlagbedingten SE lassen sich reproduzierbar SE-Ereignisse nachweisen, die mit Verformungs- und Bruchprozessen im Werkstoff in Verbindung stehen. Bei prellfreier Belastung konnten solche SE-Ereignisse im Streckgrenzenbereich nachgewiesen werden.
• Vor dem Kraftmaximum treten „rißbedingte" SE-Ereignisse auf, die im Zusammenhang mit der Schädigungsentwicklung vor der Rißspitze stehen. Die damit definierte Rißinitiierungszähigkeit stimmt gut mit dem nach der Mehrproben-Technik bestimmten Referenzwert überein.
• Rißbedingte SE tritt nicht bei jedem Stahltyp oder -zustand mit gleicher Evidenz auf. Tendenziell zeigte sich, daß mit zunehmender Zähigkeit der Nachweis duktiler Rißinitiierung durch SE schwieriger wird. Der kausale Zusammenhang zwischen SE und mikrostruktureller Schädigung ist nicht eindeutig zu belegen.
• Auf der Grundlage der Ergebnisse können Kriterien zur automatisierbaren SE-Auswertung definiert werden.

Der durch rißbedingte SE definierte Zähigkeitsparameter wurde mit der physikalischen Rißinitiierungszähigkeit verifiziert. Obgleich die riß- von der schlagbedingten SE nicht immer ohne Ermessensspielraum zu trennen ist, werden plausible und im Vergleich zu technischen Parametern konservative Jid-Werte bestimmt.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-299 September 2000

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Helium implantation induced metal gettering in silicon at half of the projected ion range

Peeva, A.; Fichtner, P.; Behar, M.; Koegler, R.; Skorupa, W.
Damage has been observed in 40 keV He ion-implanted Si away from the projected ion range Rp, mainly around Rp/2. Cu gettering has been used for the detection of irradiation defects which are formed during rapid thermal annealing (RTA) of 800°C/10 min. The transmission electron microscopy (TEM) micrographs show no visible defects at Rp/2. The Cu gettering peak at Rp/2 is well known for MeV-ion-implanted and annealed Si (Rp/2 effect). In this study the corresponding effect is observed for low ebergy implantation of a light ion like He.
Keywords: Gettering, Ion implantation, Defects, Gettering, Helium, Bubbles
  • Contribution to proceedings
    IBMM Conference, 3-8 September 2000, Porto Alegre, Brasil
  • Nucl. Instr. Meth. B 175 (2001) 176

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Formation of Ge Nanowires in Oxidized Silicon V-Grooves by Ion Beam Synthesis

Müller, T.; Heinig, K.-H.; Schmidt, B.
The formation of Ge nanowires in V-grooves on (001)Si wafers has been studied experimentally as well as theoretically. The V-grooves were formed by anisotropic etching and subsequent oxidation of their surface. The implantation of 1E17 Ge$^{+}$cm$^{-2}$ at 70 keV into the oxide layer leads to an enrichment of Ge in the V-groove bottom. In this Ge rich bottom region, subsequent annealing in N$_{2}$ atmosphere results in the formation of a nanowire by coalescence of Ge precipitates. STEM-EDX investigations of as-implanted samples have confirmed the Ge accumulation at the V-groove bottom, whereas cross-sectional TEM studies of annealed samples prove the formation of a Ge nanowire. The formation mechanisms were studied theoretically by means of a continuum description of sputtering and kinetic 3D lattice Monte-Carlo simulations of phase separation. The preliminary results indicate the possibility of achieving nanowires being several nanometers wide by further growth optimizations.
Keywords: Ion Beam Synthesis, Nanowire, V-groove, Coalescence
  • Nuclear Instruments and Methods in Physics Research B 175-177 (2001) 468-473
  • Poster
    Ion Beam Modifications of Materials Conference, Porto Alegro, Brazil, August, 2000

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Dendritic receptors for binding and transport of oxyanions

Stephan, H.; Spies, H.; Johannsen, B.; Kauffmann, C.; Schwanke, F.; Vögtle, F.
Due to their unique structural features and properties dendrimers are ideally suited for use in diagnostic imaging and therapy, transfection, and drug delivery systems.1 We are especially interested in efficient binding and controlled release of medicinally and biologically relevant anions with dendrimers tailored. In this context poly(propyleneamine)-dendrimers (POPAM) having anion affecting groups at the periphery seems to be very promising. Thus, we could show that urea-functionalized dendrimers are efficient carriers for oxyanions.2

This paper reports the binding behaviour of POPAM-dendrimers having the pH-switchable unit methyl orange at the periphery I. Furthermore POPAM-dendrimers possessing 2,6-diamidopyridine moieties IIa and IIb are investigated. The extractability of the radioactive pertechnetate TcO4- and the nucleotides AMP, ADP, and ATP with dendrimers are evaluated quantitatively by tracer methods in CHCl3/H2O systems. The extraction efficiency is studied in dependence on time, pH, buffer system, dendrimer concentration and generation. A dendritic effect is clearly visible for all dendrimers investigated. Controlled release of anionic guest molecules from the dendrimer host is allowed by alteration the pH.

[1] D.A. Tomalia, A.M. Naylor, W.A Goddart III, Angew. Chem. Int. Ed. Engl. 1990, 29, 138; Y. Kim, S.C. Zimmermann, Curr. Opin. Chem. Biol. 1998, 2, 733; O.A. Matthews, A.N. Shipway, J.F. Stoddart, Prog. Polym. Sci 1998, 23, 1; M. Fischer, F. Vögtle, Angew. Chem. Int. Ed. Engl. 1999, 38, 884; A.W. Bosman, H.M. Janssen, E.W. Meijer, Chem. Rev. 1999, 99, 1665.
[2] H. Stephan, H. Spies, B. Johannsen, L. Klein, F. Vögtle, Chem. Commun. 1999, 1875-1876
  • Poster
    ISSC XI 2000, XI International Symposium on Supramolecular Chemistry, ACROS FUKUOKA, Fukuoka/Japan, 30.07.- 04.08.2000
  • Contribution to proceedings
    ISSC XI 2000, XI International Symposium on Supramolecular Chemistry, ACROS FUKUOKA, Fukuoka/Japan, 30.07.- 04.08.2000

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Publ.-Id: 3504


Binding and transport of transition metals using tailor-made ligands

Stephan, H.
  • Lecture (others)
    Kolloquium, Department of Applied Chemistry, Saga University, Saga/Japan, 27.07.2000

Permalink: https://www.hzdr.de/publications/Publ-3503
Publ.-Id: 3503


A scissors-like state on top of the quadrupole vibrational state in 88Sr

Käubler, L.
A nuclear resonance fluorescence experiment on the spherical N=50 nucleus 88Sr has been performed with bremsstrahlung of 6.7 MeV endpoint energy using two EUROBALL CLUSTER detectors. Dipole excitations observed in the energy region 4.5 MeV $\leq Ex \leq$ 5.5 MeVare proposed to be scissors-like excitations on top of the dynamically deformed quadrupole vibrational state.
  • Contribution to proceedings
    Proc. of the Conference Bologna 2000 on "Structure of the Nucleus at the Dawn of the Century" Bologna, Italy, May 29 - June 3, 2000, World Scientific 2001, Nuclear Structure, p. 221

Permalink: https://www.hzdr.de/publications/Publ-3502
Publ.-Id: 3502


Metallographic Post Test Investigations for the Scaled Core-Meltdown-Experiments FOREVER-1 and -2

Müller, G.; Böhmert, J.

FOREVER (Failure Of Reactor Vessel Rentention) experiments has been carried out in order to simulate the behaviour the lower head of a reactor pressure vessel under the conditions of a depressurized core melt down scenario. In particular the creep behaviour and the vessel failure mode have been investigated. Metallographic post test investigations have complemented the experimental programme. Samples of different height positions of the vessel of the FOREVER-C1 and -C2 experiments were metallographically examined and characteristic microstructural appearances were identified. Additionally samples with uneffected microstructure were annealed at different temperatures and cooled by different rates and afterwards investigated. In this way the microstructural effects of the temperature regime, the thermo-mechanical loads and the environmental attack could be characterized. Remarkable effects were characteristic for the FOREVER-C2 experiment where the highest-loaded region below the welding joint reached temperatures of approx. 1100°C and a strong creep damage occured. In the FOREVER-C1 experiment creep damage could not be observed and the maximum temperature did not exceed 900°C. Environmental attack generated decarburization and oxidation but the effect was restricted to a narrow surface layer. There was almost no chemical interaction between the oxidic melt and the vessel material.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-298 August 2000

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Signature inversion caused by triaxiality in 72Br and band termination in 73Br

Schwengner, R.; Plettner, C.; Schnare, H.; Käubler, L.; Dönau, F.; Ragnarsson, I.; Afanasjev, A. V.; Algora, A.; de Angelis, G.; Gadea, A.; Napoli, D. R.; Eberth, J.; Steinhardt, T.; Thelen, O.; Hausmann, M.; Müller, A.; Jungclaus, A.; Lieb, K. P.; Jenkins, D. G.; Wadsworth, R.; Wilson, A. N.; Frauendorf, S.
High-spin states in 72Br and 73Br were studied with the EUROBALL III spectrometer.
The negative-parity band observed in 72Br displays a signature inversion around spin I = 16. Fully consistent cranked Nilsson-Strutinsky calculations show that this signature inversion can only be understood if the nuclear shape evolves from a triaxial shape with rotation around the intermediate axis at low spin through a collective prolate shape to a triaxial shape with rotation around the shortest principal axis at high spin. Rotational bands in 73Br
were observed up to spins of I = 65/2 at excitation energies of 26 MeV. Cranked Nilsson-Strutinsky calculations indicate that one of the negative-parity bands terminates at spin 63/2. Since this spin coincides with the maximum spin observed in the corresponding experimental band, we conclude that we observed this band up to its termination.
Keywords: Nuclear structure experiments. Nuclear models. EUROBALL detector.
  • Contribution to HZDR-Annual report
    Proceedings of the Conference Bologna 2000 - Structure of the Nucleus at the Dawn of the Century, 29 May - 3 June, 2000, Bologna, Italy

Permalink: https://www.hzdr.de/publications/Publ-3500
Publ.-Id: 3500


Strange quark matter: mapping QCD lattice results to finite baryon density by a quasi-particle model

Kämpfer, B.; Peshier, A.; Soff, G.
A quasi-particle model is presented which describes QCD lattice results for the 0, 2 and 4 quark-flavor equation of state.
The results are mapped to finite baryo-chemical potentials.
As an application of the model we make a prediction of deconfined matter with appropriate inclusion of strange quarks and consider pure quark stars.

Keywords: deconfined matter, quark-gluon plasma, quasi-particle model
  • Contribution to external collection
    J.Phys.G: Nucl. Part. Phys. 27:535-540,2001, 535c nucl-th/0008058

Permalink: https://www.hzdr.de/publications/Publ-3499
Publ.-Id: 3499


Optimierung der Prozessführung bei der Handhabung von Pulvern durch Insitu-Messung und qualitative Modellierung am Beispiel des Dosierens

Lindau, B.
Der Beitrag ist der Zwischenbericht des von der DFG geförderten gleichnamigen Forschungsvorhabens, Kennwort Prozessführung bei Pulverhandhabung.
Es wird auf folgende Bearbeitungsschwerpunkte näher eingegangen:
- Auswahl und Charakterisierung der für die Untersuchungen ausgewählten Pulver
- Untersuchungen zu Möglichkeiten der Insitu-Messung des Schüttgutverhaltens auf Basis von:
- Haufwerksrückwirkung am Resonanzschwingtopf (s. FWS 00-03)
- Quantifizierung des Förderverhaltens und
- zur Frequenzabhängigkeit des Förderverhaltes (s. FWS 00-02)
- Untersuchungen zum Strecken- und Regelverhalten eines entwickelten Schwingförderers sowie zur Schüttgutabhängigkeit der Reglerparameter, Erprobungsergebnisse eines fuzzy-adaptiven Dosierreglers (s. FWS 00-04)
- Entwurf eines fuzzy-adaptiven und eines Fuzzy-Reglers für die kontinuierliche Dosierung durch masse-Verlaufsregelung im Kleinstdosierbereich (<40mg/s), siehe FWS 00-01
  • Other report
    Arbeitsbericht FWS 00-05 August 2000

Permalink: https://www.hzdr.de/publications/Publ-3498
Publ.-Id: 3498


Regelungstechnische Aspekte am Schwingförderer - Entwicklung eines adaptiven Dosierreglers

Lindau, B.
Es werden die Eigenschaften des Schwingförderers als Förder- und Dosierorgan beschrieben. Aus dem Übertragungsverhalten des Schwingförderers werden die Aufgaben für den Einsatz in einer Dosierwaage formuliert. Anstelle der sonst üblichen Massestrom-Regelung wird die Masse-Verlaufs-Regelung als Folgeregelung eingesetzt, da sie für Dosierprozesse, die eine Zeitsynchronisation und eine Massebilanzierung erfordern, von Vorteil ist. Es wurde als Labormuster eine Dosierwaage, bestehend aus einer kommerziellen Präzisionswaage und einem Schwingförderer (Eigenentwicklung FZR) aufgebaut. Als Dosierregler wurde ein fuzzy-adaptiver PI-Regler entwickelt, der PC-implementiert im Echtzeit- Simulations- und Reglersystem DynStar der Hochschule Zittau realisiert wurde. Damit wurde der Prototyp eines universellen und flexiblen adaptiven Dosierreglers geschaffen, der für die kontinuierliche Dosierung von Pulvern im Kleinstbereich (< 40 mg/s) eingesetzt werden kann.
Der Beitrag entstand im Rahmen des von der DFG geförderten Forschungsvorhabens Prozessführung bei Pulverhandhabung.
  • Other report
    Arbeitsbericht FWS 00-04 August 2000

Permalink: https://www.hzdr.de/publications/Publ-3497
Publ.-Id: 3497


Untersuchungen zur Haufwerksrückwirkung an einem Resonanz-Schwingtopf als Möglichkeit zur Klassifizierung der Schüttguteigenschaften durch Insitu-Messung

Lindau, B.
Es wird ein Messverfahren zur Erfassung der Haufwerksrückwirkung und damit der Schüttguteigenschaften aus den Schwingungsgrößen eines Resonanzsystems beschrieben und Untersuchungsergebnisse an einem aufgebauten Labormuster vorgestellt. Das Verfahren ist zum Patent angemeldet. Es wird gezeigt, dass zwischen Fließverhalten und den am Resonanztopf gemessenen Merkmalen Frequenz und Tastverhältnis ein signifikanter Zusammenhang besteht. Damit kann es für die Klassifizierung und Parameteradaption bei Dosierreglern in Abhängigkeit vom Schüttgut verwendet werden. Das Messverfahren ist geeignet, als Insitu-Messung in eine Prozesslinie zur Schüttgutdosierung zu integrieren.
Der Beitrag entstand im Rahmen des von der DFG geförderten Forschungsvorhabens Prozessführung bei Pulverhandhabung.
  • Other report
    Arbeitsbericht FWS 00-03 August 2000

Permalink: https://www.hzdr.de/publications/Publ-3496
Publ.-Id: 3496


Development of complexing agents for binding Tc(VII) and An(III)

Stephan, H.
  • Lecture (others)
    Kolloquium, Department of Materials Science, Japan Atomic Energy Research Institute, Tokai/Japan, 24.07.2000

Permalink: https://www.hzdr.de/publications/Publ-3495
Publ.-Id: 3495


Untersuchungen zur Förderbarkeit von Pulvern am Schwingförderer

Lindau, B.
Es werden die Eigenschaften des Schwingförderers als Feder-Masse-System beschrieben. Daraus wird das Förderverhalten von Schüttgütern bzw. Pulvern abgeleitet. Für die Förderung bzw. Dosierung von Pulvern kleiner Mengen wird ein speziell entwickelter Förderer, der als Patent angemeldet ist, vorgestellt. Für die Beschreibung des Förderverhaltens wird die empirische Größe Diskontinuität abgeleitet. Es wird anhand von Untersuchungen gezeigt, wie Förderbarkeit und Fließverhalten sowie Förder- und Regelverhalten zusammenhängen. Durch die qualitative Beschreibung des Förderverhaltens ist der Vergleich der Fördergüter mit unterschiedlichen Eigenschaften sowie der Vergleich verschiedener Förderorgane möglich. Es ist vorgesehen, die als Insitu-Messgröße gewonnene Diskontinuität für die Klassifizierung und damit Prozessoptimierung, d.h. für die schüttgutabhängige Parametereinstellung bei Dosierreglern zu verwenden.
Der Beitrag entstand im Rahmen des von der DFG geförderten Forschungsvorhabens Prozessführung bei Pulverhandhabung.
  • Other report
    Arbeitsbericht FWS 00-02 August 2000

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Publ.-Id: 3494


Annealing behaviour of nitrogen implanted stainless steel

Mändl, S.; Günzel, R.; Richter, E.; Rauschenbach, B.; Möller, W.
The phase formation and annealing behaviour are reported after nitrogen PIII in two austenitic stainless steels, DIN 1.4541
(X6CrNiTi18.10) and DIN 1.4571 (X6CrNiMoTi17.12.2), differing only in the Mo content. The treatment parameter were
pulses of 10 s and 40 kV for a nitrogen dose of 4×1018 cm-2 at a temperature of 380°C. In 1.4541, without Mo, the modified
layer is limited to 1.5 m while the 2 wt.% Mo-containing 1.4571 exhibits a layer thickness of 15 m. No difference in the
hardness (corrected for the layer thickness) and the wear behaviour was observed. Using X-ray diffraction (XRD) a lattice
expansion between 5 and 11%, was observed, not correlated with the nitrogen content (as determined by glow discharge
optical spectroscopy ¯¯ GDOS). After annealing at 400 and 425°C for different times, the lattice constant is slightly reduced,
albeit no phase transformation was observed in 1.4571. In 1.4541 at a temperature of 425°C a strong reduction of the lattice
expansion, coupled with an inward diffusion of the nitrogen was observed. No mechanism explaining this behaviour is available
at the moment.
Keywords: PIII; Steel; X-Ray diffraction; GDOS; Nano-indentation; Pin-on-disc
  • Surface & Coatings Technology 128-129 (2000) 423-428

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Publ.-Id: 3493


Nitriding of stainless steel and aluminium alloys by plasma immersion ion implantation

Richter, E.; Günzel, R.; Parascandola, S.; Telbizova, T.; Möller, W.; Kruse, O.
Stainless steels show excellent corrosion resistance, which is lost during conventional hardening processes at temperatures
above 500°C, like gas or plasma nitriding, to improve the low hardness and to reduce the high wear rate. For aluminium alloys
it is impossible to improve the mechanical properties by traditional nitriding. Plasma immersion ion implantation (PIII) of
nitrogen is successfully used for hardening both austenitic stainless steels and aluminium alloys. Compared to the untreated
materials the hardness and the wear resistance can be improved significantly. For austenitic stainless steels an `expanded
austenite' layer of up to several tens of micrometer thickness and for aluminium alloys an AlN layer of more than 10-m
thickness were formed over a few hours. Corrosion tests showed no or only small changes in the corrosion behaviour for
stainless steel. The AlN layer can be used as a supporting layer for the deposition of hard materials like CrN on aluminium
alloys. It is shown that the partial pressure of oxygen in the residual gas in the vacuum chamber plays an important role for the
nitriding of both stainless steel and aluminium alloys
Keywords: Plasma immersion ion implantation; Stainless steel; Aluminium alloys; Nitriding; Mechanical properties
  • Surface & Coatings Technology 128-129 (2000) 21-27

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Local and integral ultrasonic gauges for two-phase flow instrumentation in nuclear reactor and safety technology

Chochlov, V. N.; Duncev, A.; Ivanov, V. V.; Kontelev, V. V.; Melnikov, V. I.; Stoppel, L. K.; Prasser, H.-M.; Zippe, W.; Zschau, J.; Zboray, R.
Das vorliegende Projekt wurde im Rahmen einer Kooperationsvereinbarung zwischen dem Forschungszentrum Rossendorf (FZR) und der wissenschaftlichen Gruppe von Prof. Melnikon von der Technischen Universität Nishny Novgorod (TUNN) der Russischen Föderation durchgeführt. Es ist Teil des Wissenschaftsunterstützungsprogramms / FSU der Bundesregierung im Rahmen der Beratungshilfe für den Aufbau von Demokratie und sozialer Marktwirtschaft (TRANSFORM). Neue Methoden der Instrumentierung für Zweiphasenströmungen wurden entwickelt: Ultraschall-Wellenleitersonden können zur lokalen Gas- bzw. Dampfgehaltsmessung eingesetzt werden. Der neue Ultraschall-Gittersensor erlaubt eine Visualisierung der Zweiphasenströmung mit ca. 250 Bildern/Sekunde. Sowohl die lokalen Sonden als auch der Ultraschall-Gittersensor können erfolgreich unter den Bedingungen von Wasser-Dampf-Gemisch bei hohem Druck und hoher Temperatur, sowie in anderen Fluiden, wie organischen Flüssigkeiten und Kältemitteln, eingesetzt werden. Darüber hinaus wurden berührungslos arbeitende Wellenleitersonden für die Durchschallung von Rohrleitungen und Dichtesensoren, die auf der Messung der Ausbreitungsgeschwindigkeit von Ultraschall in Wellenleitern beruhen, die sich im Messmedium befinden, entwickelt und getestet. Bei dem gegenwärtigen Stand der Entwicklung können die berührungslosen Sensoren lediglich als qualitativer Nachweis von Gas in einer Flüssigkeitsströmung dienen. Die Funktion der Dichtesensoren wurde anhand von Messungen in verschiedenen einphasigen Flüssigkeiten unterschiedlicher Dichte demonstriert. Für einen praktischen Einsatz ist die weitere Verbesserung der elektronischen Signalerfassung erforderlich. Die hauptsächliche Innovation wird durch den Ultraschall-Gittersensor verkörpert, dessen Auflösung mit der von schnellen elektrischen Gittersensoren und ultraschnellen Röntgentomographen vergleichbar ist, während das Gerät selbst sehr robust und preiswert ist.
Keywords: Ultraschallsensoren, Zweiphasenmesstechnik, Gasgehalt, Dampfgehalt, Visualisierung
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-303 November 2000

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Publ.-Id: 3491


Definition of the 6th Dynamic AER Benchmark - Main Steam Line Break in a NPP with VVER-440

Kliem, S.; Seidel, A.; Grundmann, U.
The 6th dynamic benchmark concerns a double ended break of one main steam line (asymmetric MSLB) in a VVER-440 plant. The core is at the end of its first cycle in full power conditions. The control rods of group K6 are at position 175 cm from bottom of the core. All other groups of control rods are out of the core. The initial state conditions of the core in the beginning of the transient are given. The isothermal re-criticality temperature of the core is defined to be 210°C. It should be achieved by tuning the worth of all control rods. Otherwise, own best estimate nuclear data are to be used. The main geometrical parameters of the plant and the characteristics of control and safety systems to be considered are given. Otherwise, own input data decks developed for a VVER-440 plant and for the applied codes can be used. The objective is to calculate the behaviour of the core during this re-criticality event using coupled codes, which combine a three-dimensional neutron kinetics code for the core with a thermohydraulics system code. This benchmark is a logical continuation of the work in the 5th dynamic benchmark. Additional new features include asymmetric operation of the feed water system, effects of coolant mixing in the reactor vessel, and the definition of a fixed isothermal re-criticality temperature for normalising the nuclear data.
  • Lecture (Conference)
    Tenth Symposium of AER on VVER Reactor Physics and Reactor Safety 2000, Moscow (Russia), 18.-22. September 2000, Proceedings pp. 749-762
  • Contribution to proceedings
    Tenth Symposium of AER on VVER Reactor Physics and Reactor Safety 2000, Moscow (Russia), 18.-22. September 2000, Proceedings pp. 749-762

Permalink: https://www.hzdr.de/publications/Publ-3490
Publ.-Id: 3490


Quantitative Radioluminography of Serotonin Uptake Sites in the Porcine Brain

Cumming, P.; Kretzschmar, M.; Brust, P.; Smith, D. F.
The regional density of serotonin uptake sites in porcine brain was determined by quantitative radioluminography. Brain cryostat sections 30 mm thick were cut in the sagittal plane and were incubated with [3H]citalopram for selective labelling of serotonin uptake sites. The autoradiograms were quantified using tritium-sensitive radioluminography. The apparent affinity (KD) of [3H]citalopram for its binding sites in various brain regions ranged from 2.3 - 5.6 nM. The density of serotonin uptake sites was highest (200 - 300 fmol/mg tissue) in the amygdala, superior colliculus and substantia nigra. Intermediate binding (100 fmol/mg tissue) was present in the dorsomedial thalamus, basal ganglia, and entorhinal cortex. Traces of specific binding (10 fmol/mg tissue) were detected in the neocortex and cerebellar cortex. The findings show that the anatomic distribution of serotonin uptake sites in the porcine brain is similar to that reported in other mammals. The density was close to that reported in human brain and in rat brain.

  • Synapse 39 (2001) 351-355

Permalink: https://www.hzdr.de/publications/Publ-3489
Publ.-Id: 3489


Characterization of [11C]McN5652 in various animal species: Implications for tracer development

Brust, P.; Zessin, J.; Kretzschmar, M.; Bergmann, R.; Friedrich, A.; Füchtner, F.; Hinz, R.; Steinbach, J.; Johannsen, B.
Introduction:
Loss of 5-HT transporter (SERT) sites has been implicated in various brain diseases. Therefore, the development of suitable radioligands for neuroimaging of the SERT in the human brain is important. [11C](+)McN5652 is the only PET radioligand which is available for clinical use. However this compound is not optimal because of its rather slow kinetics and high non-specific binding in the human brain. For the evaluation of further radioligands in animal experiments a comparison with [11C](+)McN5652 is recommendable. Therefore we have studied the binding and distribution of [11C](+)McN5652 in various animal species.

Methods:
The in vitro binding of [11C](+)McN5652 was studied on tissue homogenates and slices of rat and porcine brain and on the SERT expressing human placental cell line JAR. The in vivo binding of [11C](+)McN5652 was investigated in rats, mice and pigs. 35 Wistar rats (age: 8 weeks) were injected with 20 MBq [11C](+)McN5652 and sacrificed at 5, 30, 60, or 90 min p.i. 11 rats were treated additionally with 5 mg/kg i.v. fluoxetine or citalopram 5 min before tracer injection. Additionally 6 mice were injected with 80-200 MBq [11C](+)McN5652 and sacrificed at 60 min p.i. The brains were quickly removed and frozen for autoradiography. Three six weeks old farm-bred female pigs were studied with PET (31 frames, 120 min) under general anesthesia (0.5-0.75% isoflurane in N2O/O2. 46-48 arterial blood samples were obtained at defined time points. Additional arterial samples were withdrawn for detection of metabolites using thin-layer chromatography.

Results:
Evidence for a significant binding of [11C](+)McN5652 not only to SERT but also to the norepinephrine (NET) and dopamine transporters (DAT) was found in vitro. IC50 values of 6.6 and 9.4 nM for NET and DAT were measured. Binding equilibrium at JAR cells was reached after about 60 min. Nonspecific binding (defined by 10 µM citalopram) was 76%. In rats a high brain uptake was found with the highest values measured in thalamus, colliculi and olfactory bulb (~1.3 % g-1). Only in these regions a significant inhibition (38-48%) by fluoxetine and citalopram was found. Similar results were obtained by autoradiography in mice. Also the PET data obtained in pigs revealed a high blood-brain transfer of [11C](+)McN5652 (K1: 0.22-0.43 ml g-1 min-1). Rapid metabolism was observed. More than 50% metabolites were found at 12 min p.i. Significant binding of [11C](+)McN5652 was observed in all 23 regions studied (k3: 0.018-0.044 min-1). The highest binding potential was found in thalamus and colliculi. Preinjection of citalopram or fluoxetine reduced k3 by 30-70%.

Comments:
A high consistency exists between the in vitro and in vivo studies in various animal species. The data reveal a displaceable binding in target regions but also a rather high nonspecific binding of [11C](+)McN5652. Binding to other targets such as NET and DAT may contribute to this. The location of serotonin uptake sites in the porcine brain appears to be similar to that found in rats and mice which makes pigs a suitable animal model for the development of radioligands for studying serotonergic functions with PET.
  • Abstract in refereed journal
    NeuroImage Vol. 11 (6Pt2) (2000) S66
  • Lecture (Conference)
    Third International Symposium on Functional Neuroreceptor Mapping, New York, 09.-11.06.2000

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Publ.-Id: 3488


Gettering centres in high-energy ion-implanted silicon investigated by point defect recombination

Kögler, R.; Peeva, A.; Skorupa, W.; Werner, P.; Gösele, U.
Self-interstitials were introduced by additional Si+ implantation into the vacancy-dominated depth range around half of the projected ion range, RP/2, of high-energy ion-implanted Si in order to balance radiation-induced excess vacancies. The undesired gettering of Cu atoms in this region (RP/2 effect) could be suppressed. The threshold was determined necessary to remove the Cu gettering at RP/2. It does approximately agree with the number of the calculated excess vacancies. Additional interstitial-type dislocation loops were formed during annealing at RP/2 as the Si+ fluence exceeds this threshold. Interstitial clusters were not approved to be the gettering centres for Cu trapping
Keywords: Si, Ion implantation, Defects, Gettering, Cu
  • Nuclear Instruments and Methods in Physics Research B 175-177 (2001) 340-344

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Publ.-Id: 3487


Measurements of recovery coefficients for the HR+ and their application in a correction method

Linemann, H.; Will, E.; Beuthien-Baumann, B.; Kutzner, H.

Introduction
The activity concentration of small lesions with diameters comparable to the spatial resolution (FWHM) is underestimated in PET measurements. This resolution is determined by the camera characteristics and also by the reconstruction and filter conditions used. For simple formed lesions the underestimation can be corrected, if the size of the lesion and the spatial resolving in the recon-structed picture are known and appropriate phantom measurements are present.
The aim of the study was to determine the resolution as well as the recovery coefficients( HSRC) for small spheres by phantom measurements and to prove, whether the underestimation is possible to correct by means of the quotient of the two measured lesion values for reconstructions with clearly different picture resolution.

Methods
All measurements took place at the PET camera ECAT EXACT HR+ with the software V7.1 (Siemens, CTI) in the 2D-Mode. For the measurement of the HSRC the EEC head phantom with the hollow spheres insert was used. Additionaly 8 thin-walled glass spheres with inside diameter values between 5.0 mm and 8.6 mm were examined. The reconstruction of the phantom measurements took place with FBP and OSEM.
The transversal resolution was measured with three line sources in water and the average values from radial and tangential values were calculated.
From ROIs with the diameter equal to the FWHM the recovery coefficients (phantom measurements) and the contrast values (patient measurements) were determined.

Results and Discussion
The transver-sal resolution was measured for axial distances up to 11.5 cm. For distances larger than 7 cm the radial component is increased.
If the HSRC from two reconstructions with significantly different image resolution are used to calculate a quotient HSRC1/HSRC2 then spheres with diameters smaller approximatly 15 mm can be distinct.
This method can be used to correct the recovery of a lesion in a patient study by determination of the image contrast. Fore the application of the procedure to lesions in the periphery of the body the dependence of the resolution from the axial distance must be considered.
Further investigation should be done to show the limits of this method.
  • Poster
    CTI-Tagung Barcelona, Spanien, 28.8.-1.9.2000

Permalink: https://www.hzdr.de/publications/Publ-3486
Publ.-Id: 3486


'3+1' Mixed-ligand oxotechnetium(V) complexes with affinity for melanoma: Synthesis and Evaluation in vitro and in vivo

Friebe, M.; Mahmood, A.; Spies, H.; Berger, R.; Johannsen, B.; Mohammed, A.; Eisenhut, M.; Bolzati, C.; Davison, A.; Jones, A. G.
'3+1' Mixed-ligand [99mTc]oxotechnetium complexes with affinity for melanoma were synthesized in a one-pot reaction. Complexation of technetium-99m with a mixture of N-R(3-azapentane-1,5-dithiol) [R = Me, Pr, Bn, Et2N(CH2)2] and N-(2-dialkylamino)ethanethiol [alkyl] = X = Et, Bu, morpholinyl] using Sn2+ as the reducing agent resulted in the formation of '3+1' mixed-ligand technetium-99m complexes [TcO(SN(R)S)(SNX2)] in high radiochemical yield (60-98%). In vitro uptake studies in B16 murine melanoma cells indicated a moderate tumor-cell accumulation (40%) of compound 1 [R = Me, X = Et] and a higher accumulation (69%) of compound 2 [R = Me, X = Bu] after a 60-min incubation. In vivo evaluation of compounds 1-6 in the C57B16/B16 mouse melanoma model demonstrated tumor localization. Compound 2 displayed the highest accumulation with up to 5% ID/g at 60 min after injection. In vivo, 2 also showed a low blood-pool activity and high melanoma/spleen (4.3) and melanoma/lung (1.9) ratios at 1 h. These results suggest that small technetium-99m complexes could be useful as potential melanoma-imaging agents.
  • Journal of Medicinal Chemistry 43 (2000) 2745-2752

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Publ.-Id: 3485


Neutral '3+1' mixed-ligand oxorhenium(V) complexes with tridentate [S,N,S] chelates and aminoalkanethiols: synthesis, characterization and structure determination

Friebe, M.; Spies, H.; Seichter, W.; Leibnitz, P.; Johannsen, B.
'3+1' Oxorhenium(v) complexes [ReO(SN(R')S)(SR)] (R' = Me, Et, Pr or Bu; SR = aminoalkane thiolate) have been synthesized by ligand exchange at trans-trichloromonooxo-bis(triphenylphosphine)rhenium(v) with a mixture of HSN(R')SH and RSH in alkaline methanolic solution. The complexes were purified by column chromatography and characterized by elemental analysis, mass and IR spectroscopy and for selected compounds by 1H NMR spectroscopy. The structures of those complexes have been determined by X-ray diffraction analysis and revealed a change in the co-ordination geometry from square pyramidal to trigonal bipyramidal, depending on the chelating (SN(R')S) moiety. The alkyl group (R') was found to be arranged "syn" to the oxorhenium group.
  • J. Chem. Soc, Dalton Trans. (2000) 2471-2475

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Publ.-Id: 3484


Stress relaxation during annealing of boron nitride films

Fitz, C.; Kolitsch, A.; Fukarek, W.
The global stresses in turbostratic and cubic boron nitride films are studied during annealing up to 670 °C. It is observed that the stress relaxation starts when the deposition temperature is exceeded. The compressive intrinsic stress in tBN and cBN decreases exponentially with the same time constant of . Depth resolved analysis of the stress before and after annealing reveals that the features in the stress depth profile do not smear out during annealing. The stress relaxation in the interfacial turbostratic boron nitride exceeds that in the cubic boron nitride on top by a factor of 1.5±0.2 and is thus not significantly affected by the capping cubic boron nitride. The specific thermal stresses in turbostratic and cubic boron nitride films are not altered after thermal treatment up to 670 °C. It is concluded that the decrease in stress is mainly due to changes in strain, whereas the elastic properties of boron nitride films remain largely constant under annealing.
Keywords: boron nitride; heat treatment; stress
  • Thin Solid Films 389 (2001) 173-179

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Publ.-Id: 3483


Microbiology and Radioactivity Chapter 8. Diversity and Activity of Bacteria in Uranium Waste Piles

Selenska-Pobell, S.; Flemming, K.; Radeva, G.; Tzvetkova, I.; Tzvetkova, T.; Merroun, M.; Raff, J.
The pollution of the environment with toxic metals is one of the most severe problems of our industrial century. The uranium mining waste piles are a subject of particular attention, because in soils, sediments, and drain waters of these environments significant amounts of many hazardous metals such as uranium, caesium, strontium, selenium, molybdenum, arsenic, cadmium, chromium, mercury, lead, copper, nickel, zinc, etc. are present (Francis, 1990). In addition, significant amounts of thorium, radium, and polonium might also be present at the so called uranium "mill tailings" where the extraction of uranium from the ores was performed.
It was demonstrated that even in the most heavily polluted uranium wastes large numbers of bacteria are present (Cerda et al., 1993; Goebel & Stackebrandt, 1994; Shippers et al., 1994). Moreover, different groups of bacteria are interacting in various ways with metals and radionuclides. Some of the most important mechanisms by which bacteria can biotransform and influence the mobilisation and/or immobilisation of metals are listed below:
1) Direct oxidation and/or reduction of metals, which affect their solubility (DiSpirito & Tuovinen, 1982; Lovley, 1993; Nelson et al., 1999; Sharma et al. 2000; Wildung et al., 2000);
2) Direct or indirect oxidation of metal sulfides and solubilization of certain elements (Bosecker, 1997; Krebs & Brandl, 1997);
3) Indirect alteration of metal ionic states caused by bacterial induced pH and Eh changes in the medium (Bosecker, 1997; Bacelar-Nicolau & Johnson, 1999);
4) Bioaccumulation [biosorption by cell surface polymers (DiSpirito et al., 1983; Douglas & Beveridge, 1998; Macaskie et al., 1992; Panak et al., 1999; Selenska-Pobell et al., 1999; Valentive et al., 1996) and/or uptake of metals inside the cells (Klaus et al., 1999; Marques et al., 1991; Purchase et al., 1997)].
5) Bio-mineralization, which includes induction of metal precipitates by particular metabolic functions of some bacteria and consequent generation of minerals (Brown and Beveridge, 1998; Douglas and Beveridge, 1998; Francis, 1998);
6) Release of the biosorbed metals by chelation, alkylation, or decomposition (Bosecker, 1997; Francis, 1990; Francis et al., 1998).
It is clear that the above described bacterial activities are strongly influencing the fate and the migration of toxic metals in and outside of the sites where uranium mining was performed.
In addition to the living cells, significant amounts of different bacterial metabolites are present in the wastes which are also interacting with the heavy metals and influencing their behaviour.
For these reasons, the knowledge about the diversity and about the activity of the indigenous bacteria in the uranium waste piles is of basic importance for understanding the bio-geo-chemical processes occurring in these environments and especially for modelling the process of migration of the heavy metals and radionuclides in nature.
  • Book (Authorship)
    Chapter 8, Microbiology and Radioactivity in Interactions of Microorganisms with Radionuclides, M. Keith-Roach and F. Livens (eds.) Elsevier Science, Oxford, UK, pp.225-253

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Publ.-Id: 3482


Interactions of the S-Layer protein of the uranium waste pile isolate bacillus sphaericus JG-A 12 with metals

Raff, J.; Wahl, R.; Matys, S.; Flemming, K.; Mertig, M.; Selenska-Pobell, S.; Pompe, W.
Bacteria in uranium waste piles are of special interest for bioremediation, because they are adapted to high concentrations of radionuclides and heavy metals which occur in these environments. A large number of Bacillus strains was recovered from a uranium mining waste pile "Haberland" near the town of Johanngeorgenstadt in Saxony, Germany. One isolate, Bacillus sphaericus JG-A 12, possesses a surface layer protein with a molecular weight of 135 kDa [1]. Sequence analysis of a part of the gene of this protein, coding 184 amino acids from the N-terminal region of its matured S-layer product, demonstrated that the protein shares only a limited homol-ogy (less than 35%) to the known S-layers of the other Bacillus sphaericus strains WHO 2362, CCM 2177 and P-1 (see Fig. 1).
  • Poster
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

Permalink: https://www.hzdr.de/publications/Publ-3480
Publ.-Id: 3480


Bacteria from Uranium waste piles and their interactions with uranium(VI) and other metals

Selenska-Pobell, S.; Flemming, K.; Merroun, M.; Radeva, G.; Raff, J.; Tzvetkova, I.; Zzvetkova, T.; Hennig, C.; Reich, T.
Bacterial diversity was studied in drain waters and soil samples drawn from different sites and depths of three uranium mill-tailings - Schlema/Alberoda, Gittersee/ Coschütz (Germany), and Shiprock, New Mexico (USA) as well as in samples drawn from two uranium mining waste depository sites, "Haberlandhalde" near the town of Johanngeorgenstadt and Deponie B1, Germany. For this study both culture-dependent and culture-independent i.e. direct molecular approaches were applied.
The direct molecular analyses involved PCR based rep-APD, 16S rDNA and RISA retrievals [1, 2, 3].
Three parallel rDNA clone libraries (16S rDNA I, 16S rDNA II, and RISA) were constructed for each of the samples studied using three different sets of PCR primer pairs (see Fig. 1).Fig. 1. Clone libraries constructed for the soil and water samples from the uranium wastes analysed

The clones of each of the above mentioned three libraries constructed from the same sample usually indicated the presence of different, not overlapping bacterial groups. This demonstrates the necessity of using more than one PCR primer pair in the construction of the environmental rDNA libraries, because as mentioned by others [4] in such complex mixtures of DNA templates the regions flanking the PCR amplification products are strongly influencing the effectivity and the preferences of the PCR reaction. As a result of these so called biases of the preferential PCR on the end of each amplification an enrichment with particular fragments preferred by the process occurs.
For example, in some samples of the uranium wastes the RISA retrieval demonstrated the predominance of the aerobic ammonia oxidisers Nitrosomonas (b-Proteobacteria) and of the anaerobic chemolithotrophic ammonia oxidizing bacteria named Anammox (Planctomycetales) which were "overseen" by the 16S rDNA retrievals.
The direct molecular approach has demonstrated that, in general, the bacterial populations in the environmental samples studied possess different grade of variability. The highest variability was found in the soil samples drawn from depths between 2.5 m and 5 m below the surface and also in the water sediment samples. Despite the fact that the predominant bacterial species in the studied environments are in general site-specific, many samples share common bacterial groups. These groups belong mainly to the g subgroup of Pseudomonas; to the sulfate and metal reducing genera such as Desulfovibrio, and Geobacter (d-Proteobacteria); to the aerobic chemolithoautotrophs oxidizing iron and sulfur compounds (Acidithiobacillus); or to those oxidizing nitrite (Nitrospina) and ammonium (Nitrosomonas), d- and b-Proteobacteria, respectively. A large number of diverse 16S rDNA sequences was related to various not yet cultured representatives of Holophaga/Acidomicrobium and Cytophaga/ Flexibacter clusters. In addition, many 16S rDNA sequences were affiliated with novel so-called "candidate" bacterial divisions.
Both the RISA and the 16S rDNA retrievals revealed many cases of bacterial microdiversity, i.e. presence of closely related strains belonging to the same species predominating in the natural community.

Analyzsing different individual bacterial isolates as well as mixed enrichment bacterial cultures we have demonstrated the presence of strains belonging to the genera Acidithiobacillus, Agrobacterium, Bacillus, Clostridium, Desulfovibrio, Leptospirillum, Pseudomonas, Rhizobium, Stenotrophomonas, etc. in the samples of the uranium wastes. The exact phylogenetic affiliation of the individual strains studied was performed by the use of the 16S rDNA RFLP and sequence analyses. Many of the strains cultured represent novel bacterial species within the above mentioned genera. In addition, several pure cultures of isolates which are closely related to some previously uncultured bacterial species were cultured.
Interactions of several of the natural uranium waste isolates with uranium (VI), in particular, sor...
  • Lecture (Conference)
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

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Publ.-Id: 3479


Molecular analysis of bacteria cultured from uranium mining waste piles

Tzvetkova, I.; Tzvetkova, T.; Groudeva, V.; Selenska-Pobell, S.
The main problem of the direct molecular approaches for studying environmental samples is the so called preferential PCR amplification which can mask the presence of some DNA templates in the samples.
For this reason the application of the classical approach of the enrichment cultures, in parallel to the molecular retrievals, for studies on bacterial diversity in the environment may be helpful. Of course, here the limitation to analyze only those strains of the community which are able to grow individually exists. It is a compromise to analyze enriched biofilm cultures or mixed cultures instead of pure cultures, because most of the bacteria in the extreme environments are living in consortia which are described as symbiotic [1, 2]. The identification of the members of such mixed cultures using the 16S rDNA retrieval may provide very important information in addition to those, derived by the direct methods, about the bacteria present in the samples studied.
Our studies on phylogenetic diversity of bacteria cultured as pure and/or mixed cultures from the uranium wastes are presented in Table 1.
From these results one can see that bacterial strains known for their ability to biotransform metals were recovered from the samples. For example, different types of Acidithiobacillus ferrooxidans, which are oxidizing iron and sulfur compounds and Leptospirillum ferrooxidans , oxidizing iron, were cultured. These two groups of bacteria play a significant role in the mobilization of many metals and radionuclides in the wastes, because as a result of their physiological activity large amounts of H2SO4 are produced and the pH in their surrounding is extremely low.
Individual cultures representing sulfate reducing bacteria of the genus Desulfovibrio which are able to reduce also uranium and other metals were cultured from the uranium mining waste samples as well.
In addition, strains belonging to the species Pseudomonas stutzeri, Pseudomonas migulae, Erwinia herbicola (g-Proteobacteria) as well as isolates related to Agrobacterium and Sphingomonas (a-Proteobacteria) were cultured.
In addition to the above described individual bacterial isolates several enrichment mixed cultures were recovered. One of them, called initially "JG1", from which the sulfate reducing Desulfovibrio isolate JG1 was purified, consisted of 11 diverse representatives of Clostridium (see the series of clones IrT-JG1 affiliated to the Bacillus/Clostridium group in Table 1) and the two clones IrT-JG1-58 and IrT-JG1-71 closely related to the isolate Desulfovibrio JG1.
Formerly we have reported that the mixed culture of "JG1" is able to reduce and precipitate amounts of about 1.5 g of U(VI) per g of dry weight bacterial biomass from a liquid medium independently on its pH value in the range between 2.8 and 6.0 [3]. Our recent results demonstrated, however, that the U(VI) reducing capacity of the pure culture of Desulfovibrio sp. JG1 does not differ significantly from those published for the other uranium reducing bacteria, Desulfovibrio vulgaris, D. desulfuricans, and Geobacter metallireducens which is about five times lower and, in addition, it is pH dependent with an optimum of pH 6.8 [4, 5]. This indicates that the higher capability of the mixed culture "JG1" to precipitate uranium at a wider range of environmental conditions (pH for example) is a result of the combined function of the different bacterial members of which it consists. We suppose that in addition to the U(VI) reduction performed by the above mentioned natural strains of Desulfovibrio sp. (JG1, IrT-JG1-58 and JrT-JG1-71) some other processes occur, as bio-precipitation or/and bio-minearalisation stimulated by the metabolic functions of the described Clostridia present in the mixed culture.
Another mixed culture "JG14" consisted of different a-Proteobacteria (Agrobacterium and Rhizobium) and a microdiverse population of environmental strains of Stenotrophomonas maltopilia (d-Proteobacteria). ...
  • Poster
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

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Publ.-Id: 3478


Microbial diversity in soil and water samples from uranium mining waste piles

Radeva, G.; Flemming, K.; Selenska-Pobell, S.
Bacterial diversity in soil and drain water samples of uranium mining waste piles was studied by two direct (culture-independent) approaches, the16S rDNA and the ribosomal intergenic spacer amplification (RISA) retrievals. A large number of samples was studied which were drawn from the following heavy metal and radionuclide polluted sites: the uranium mill-tailings Schlema /Alberoda, Gittersee/Coschütz, in Germany, and Shiprock/New Mexico in the USA, as well as two uranium mining disposal sites, Haberlandhalde near the town of Johanngeorgenstadt and Deponie B1/Weisse Elster (Germany).
Both methods demonstrate significant differences in the microbial diversity between the samples studied. The highest diversity was found in the drain water and soil samples from the mill-tailing Gittersee/Coschütz, followed by those from Schlema/Alberoda and the Haberlandhalde. The predominant 16S rDNA fragments in those samples were affiliated to Pseudomonas, Geobacter, and to different uncultured sulfate reducing and Cytophaga-like bacteria. Interestingly, in the samples of the Gittersee/Coschütz site the presence of the recently discovered anaerobic chemolithotrophic ammonium oxidizing bacteria named Anammox [1] was demonstrated by the use of the RISA approach. Using the same approach, an abundance of Nitrosomonas sp., nitrifying bacteria belonging to b-subclass of Proteobacteria was found in the water samples from Shiprock. Both groups of bacteria were "overseen" when the 16S rDNA retrieval was applied for analyzing the same samples. These results clearly demonstrate the utility of using at least two primer pairs for PCR amplifications of environmental rDNA fragments in order to overcome the masking effect of the preferential amplification, which depends on the structure of the flanking regions of the templates.
In all kinds of uranium polluted wastes the presence of a large variety of not yet cultured bacteria belonging to Holophaga/Acidobacterium and Cytophaga/ Flexibacter clusters was shown. In addition, many 16S rDNA sequences were affiliated with various unidentified so- called "candidate" bacterial divisions such as OP1, and OP6 [2].

Acknowledgements
This work was supported by grants 7531.50-03-FZR/607 from the Sächsisches Staatministerium für Wissenschaft und Kunst, Dresden, Germany and GRP/9816 from the European Science Foundation. The authors thank David Balkwill, Florida State University, Tallahassee, USA for providing some of the water samples.

  • Poster
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

Permalink: https://www.hzdr.de/publications/Publ-3477
Publ.-Id: 3477


Microdiversity of Leptospirillum Ferrooxidans isolates recovered from uranium wastes and their interaction with U(VI)

Tzvetkova, T.; Groudeva, V.; Selenska-Pobell, S.
A large number of acidophilic chemolithoautotrophic iron oxidizing bacterial isolates recovered from two uranium mining waste piles was classified as Leptospirillum ferrooxidans. For this purpose a combination of classical and molecular microbiological methods was applied. The letter involved Amplified Ribosomal DNA Restriction Endonucleases analysis (ARDREA) and 16S rDNA sequence analysis. In the ARDREA two sets of primers were involved: one universal -16S7f and 16S1406r, and one species specific -16S176f and 16S679r (De-Wulf-Durand et al,.1997, Tzvetkova et al., 1999). In both cases using endonuclease RsaI, two groups were discriminated among the isolates studied. These groups correspond to the recently characterized RsaI RFLP types I and II of L. ferrooxidans, which include the type strain of the species L. ferrooxidans DSM 2705T (type I) and the strains L. ferrooxidans DSM 2391 and Lf30A (type II); (Fig.1 and Tzvetkova et. al., 1999);
An additional extensive comparative sequence analysis of the variable region 3 of a series of natural isolates and the deposited sequences of this region in the EMBL allowed to distinguish seven L. ferrooxidans groups. Each group possesses a specific signature in the helix 18 of the variable region 3 (Fig.2). These signatures discriminate particular types of the species and possibly reflect the genetic adaptations of different parts of the natural L. ferrooxidans populations to different concentrations of heavy metals and other components of their natural environment. The variability of the helix 18 influences target sites of several frequently cutting endonucleases and allows discrimination of some of the above mentioned groups.
The interaction of some L. ferrooxidans natural isolates with uranium was studied at different concentrations of the metal and at two pH values. Results demonstrating accumulation of U(VI) at unusually low pH values are presented and discussed in the poster
  • Lecture (Conference)
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

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Publ.-Id: 3476


EXAFS investigation of uranium(VI) complexes formed at Acidithiobacillus Ferrooxidans types

Merroun, M.; Hennig, C.; Reich, T.; Selenska-Pobell, S.
Bacteria express a wide variety of complex molecules on their surfaces, which, at physiological pH values, contain numerous charged chemical groups (such as phosphoryl, carboxyl, and amino groups) that usually give the cell surface a net of anionic (negative) charge density. Since the cell surface is in direct contact with the environment, the charged groups within the surface layers are able to interact with ions or charged molecules present in the external milieu. As a result, metal cations can become electrostatically attracted and bound to the cell surface [1].

Uranium (VI) complexes formation at surfaces of three Acidithiobacillus ferrooxidans types was studied using uranium LIII-edge extended x-ray absorption fine structure (EXAFS) spectroscopy. In all samples uranium is coordinated by two axial oxygen atoms (Oax) at distance of 1.77-1.78 Å. The average distance between uranium and the equatorial oxygen atoms (Oeq) is 2.35 Å. The coordination number for Oeq is 5-6. In comparison to the uranium crystal structure data, the U-Oeq distance indicates a coordination number of the equatorial oxygen of 5.

Within the experimental error, there are no differences in the U-O bond distances between samples from the 3 types of A. ferrooxidans investigated. The fit to the EXAFS data of samples measured as wet pastes gave the same results as for dried samples. No significant structural differences were observed for the uranium complexes formed by the three eco-types of A. ferrooxidans. However, the EXAFS spectra are indicating a formation of uranium complexes which are different from those formed by Bacilli [2] where the bond length of 2.28 Å indicates a coordination number of 4 for the equatorial oxygen atoms.
  • Poster
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

Permalink: https://www.hzdr.de/publications/Publ-3475
Publ.-Id: 3475


Complexation of uranium by three different Acidithiobacillus Ferrooxidans types

Merroun, M.; Tzvetkova, Z.; Selenska-Pobell, S.
In uranium mining piles a number of acidophilic chemolithoautotrophic bacteria has been identified, which are able to oxidize sulphide minerals, elemental sulfur, ferrous iron, and, in presence of uranium minerals, also U(IV). Especially one representative of this group, Acidithiobacillus ferrooxidans, is of particular interest. This organism has been used commercially in metal leaching from ores and decontamination of industrial wastes [1].
Sequence analysis of the 16S rRNA genes of several reference strains and uranium mining waste pile isolates of this bacterium revealed specific signatures which distinguish three types within the species. This allowed to develop a technique for analysis of the distribution of the A. ferrooxidans eco-types in the soil samples of a uranium mining waste pile.
The technique is based on amplification of 16S rDNA fragments in total soil DNA by the use of two A. ferrooxidans species specific primers 16S458F and 16S1473R [2]. The resulting amplicons were then digested with a frequently cutting enzyme RsaI which produced three different type-specific profiles [3; 4]. Using this direct approach we have demonstrated that one of the A. ferrooxidans types (type I) was predominant in the soil samples studied and was found in more polluted sites, whereas the type II was found in less contaminated samples. The type III was found mostly to coexist with the type II.
The objectives of the present work were to determine whether these eco-types differ in their capability to tolerate and accumulate uranium, and also to study the structural complexes formed at the surfaces of A. ferrooxidans eco-types using different spectroscopic techniques as Extended X-ray Absorption Fine Structure (EXAFS), Infra Red (IR) and time-resolved laser-induced fluorescence spectroscopy (TRLFS). In addition, the most efficient desorbing agent for the accumulated uranium was selected.
The uranium accumulation by the above mentioned three types of A. ferrooxidans was studied at different metal concentrations and different pH values (1.5 and 4). The results obtained (Fig.1) demonstrated that the strains from the different types possess different capability to accumulate uranium. The amount of uranium biosorbed by the three types increased with increasing concentration of uranium.
Fig.1: Biosorption of uranium by different types of A. ferrooxidans

Interestingly, the strains W1 (type I) and D2 (type III) are resistant to 8 and 9 mM of uranium, respectively, whereas the strain ATCC 33020 (type II) does not tolerate more than 2 mM of uranium (Table 1).


Strains

Uranium (mM)
Tolerated
MICs
A. ferrooxidans W1
8 9
A. ferrooxidans ATCC 33020
2 4
A. ferrooxidans D2
9 10
Table 1: Minimum Inhibitory Concentrations (MICs) of uranium for the growth of A. ferrooxidans type

On the basis of these results, one may speculate that the strains of the types I and III are more resistant to uranium, probably because they possess a mechanism which limits the uranium binding below the lethal amounts.

The desorption of the accumulated uranium from the bacterial cells was investigated using different desorbing agents as sodium carbonate, sodium citrate and EDTA at different concentrations. The results obtained demonstrated that the sodium carbonate is able to recuperate up to 97% of the uranium sorbed from the cells of A. ferrooxidans type III, and 88.33 and 88.50% from the cells of the types I and II, respectively.

Using EXAFS analysis we have found that no significant structural differences were observed between the uranium complexes formed by the 3 types of A. ferrooxidans. However, the EXAFS spectra are indicating formation of uranium complexes which are different from those formed by bacilli [5; 6].


Acknowledgements
This work was supported by grant 7531.50-03-FZR/607 from the Sächsisches Staatsministerium für Wissenschaft und Kunst, Dresden, Germany

  • Lecture (Conference)
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

Permalink: https://www.hzdr.de/publications/Publ-3474
Publ.-Id: 3474


Ion nitriding of Al: growth kinetics and characterisation of the nitride layer

Telbizova, T.; Parascandola, S.; Prokert, F.; Barradas, N. P.; Richter, E.; Möller, W.
To study the kinetics of Al ion nitriding, a series of experiments has been performed at fixed ion beam parameters using substrate temperatures varied from 250 °C to 400 °C at intervals of 50 °C. The nitride layers have been analysed by nuclear reaction analysis (NRA), elastic recoil detection analysis (ERDA), x-ray diffraction (XRD) and scanning electron microscopy (SEM). Depending on the experimental conditions, the nitriding kinetics shows different character: controlled by the delivery of N ions or by the diffusion of Al atoms. Furthermore, the growth of the nitride layer is limited due to the bad layer adhesion. XRD analysis reveals the formation of a hexagonal AlN-phase plus a small fraction of the cubic AlN-phase.
Keywords: ion nitriding, Al, AlN, growth kinetics, diffusion
  • Surface & Coatings Technology 142-144 (2001) p.1028-1033

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Publ.-Id: 3473


Beiträge zur Validierung fortgeschrittener Störfallanalysecodes mit 3D Neutronenkinetik - WTZ mit der Ukraine

Grundmann, U.; Kliem, S.; Rohde, U.; Seidel, A.; Khalimonchuk, V.; Kuchin, A.
Im Rahmen eines vom BMBF/BMWi geförderten WTZ-Vorhabens wurde der ukrainischen Aufsichtsbehörde der Programmkomplex ATHLET-DYN3D verfügbar gemacht, welcher eine Anbindung des im FZR entwickelten 3D Kernmodells DYN3D an den thermohydraulischen Systemcode ATHLET der GRS darstellt. Zur Validierung dieses gekoppelten Programmcodes wurde eine Meßdatensammlung angelegt, die entsprechend erarbeiteter Richtlinien Daten von geeigneten Betriebstransienten bereitstellt. Für zwei ausgewählte Transienten wurden Validierungsrechnungen durchgeführt. Dabei wurden die Ergebnisse mit den Meßwerten aus der Datensammlung verglichen.
Der Programmcode DYN3D wurde von den ukrainischen Experten mit einer Ergänzung zur Berechnung von Reaktivitätskoeffizienten im Funktionsumfang erweitert. Diese Programmentwicklung ermöglicht es, den Einfluß der einzelnen Reaktivitätskoeffizienten bei verschiedenen Betriebsprozessen bzw. Störungen zu untersuchen.

Keywords: Störfallanalyse, DYN3D, ATHLET, Codevalidierung, WWER-Reaktor, Messdatensammlung
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-301 Oktober 2000

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Publ.-Id: 3472


Störfallablaufanalysen für neue Reaktorkonzepte und WWER-Reaktoren mit neuem Brennstoffdesign - WTZ mit Russland

Grundmann, U.; Kliem, S.; Mittag, S.; Rohde, U.; Seidel, A.; Kozmenkov, Y.; Kumayev, V.
Im Rahmen eines vom BMBF/BMWi geförderten WTZ-Vorhabens wurden der Transfer des im Forschungszentrum Rossendorf (FZR) entwickelten Programmcodes DYN3D und seine Integration in die programmtechnische Basis des Instituts für Physik und Energietechnik (IPPE) Obninsk realisiert. Das neutronenkinetische Programmodul von DYN3D wurde von den russischen Experten genutzt, um den im IPPE verwendeten Thermohydraulikcode um die Funktion der 3D Neutronenkinetik zu erweitern. Zur Modernisierung der bisher bei Störfallanalysen verwendeten makroskopischen Wirkungsquerschnitte wurde mit dem Programmcode WIMS/D4 eine neue Datenbibliothek generiert, welche auch die bereits in WWER-Reaktoren umgesetzten Konzepte zu modifizierten Kernbeladungen (abbrennbare Absorber unterschiedlicher Borkonzentration) berücksichtigen kann. Diese Querschnittdatenbibliothek wurde an DYN3D angeschlossen und in ersten Vergleichsrechnungen auf seine Funktionstüchtigkeit sowie Genauigkeit überprüft.
Für das unter Beteiligung von IPPE erstellte integrale Reaktorkonzept ABV-67 wurden sowohl mit DYN3D als auch mit dem gekoppelten Programmkomplex erste ATWS-Analysen durchgeführt.
Der im IPPE entwickelte Fluiddynamikcode DINCOR wurde dem FZR zur Nutzung übergeben und durch gemeinsame Nachrechnungen von Modellaufgaben zum kurzzeitigen Schmelzeverhalten (CORVIS-Experimente) validiert.

Keywords: Störfallanalyse, DYN3D, RELAP, Programmkopplung, WWER-Reaktor, integraler Druckwasserreaktor, DINCOR
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-302 Oktober 2000

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Publ.-Id: 3471


The emission pattern of high-energy pions: A new probe for the Early Phase of heavy ion collisions

Wagner, A.; Müntz, C.; Oeschler, H.; Sturm, C.; Barth, R.; Cieslak, M.; Debowski, M.; Grosse, E.; Koczon, P.; Mang, M.; Miskowiec, D.; Schicker, R.; Schwab, E.; Senger, P.; Beckerle, P.; Brill, D.; Shin, Y.-H.; Ströbele, H.; Walus, W.; Kohlmeyer, B.; Pühlhofer, F.; Speer, J.; Völkel, K.
The emission pattern of charged pions has been measured in Au+Au collisions at 1 GeV/nucleon incident energy.
In peripheral collisions and at target rapidities, high-energy pions are emitted preferentially towards the target spectator matter. In contrast, low-energy pions are emitted predominantly in the opposite direction. The corresponding azimuthal anisotropy is explained by the interaction of pions with projectile and target spectator matter. This interaction with the spectator matter causes an effective shadowing which varies with time during the reaction. Our observations show that high-energy pions stem from the early stage of the collision whereas low-energy pions freeze out later.
Keywords: pions Au+Au collision azimuthal anisotropy shadow freeze-out
  • Physical Review Letters 85 (2000) 18-21.

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Publ.-Id: 3470


Some Issues by Using the Master Curve Concept

Viehrig, H.-W.; Böhmert, J.; Dzugan, J.
The Master Curve concept allows to quantify the variation of fracture toughness with the temperature throughout the ductile-to-brittle transition region. Limit curves of fracture tough ness for defined failure probabilities and a reference temperatures can be determined using this method. Thus, fracture mechanical values can be supplied for an integrity assessment of structural components. This paper presents the application of the master curve concept to the reference temperature determination over the thickness of RPV steel plate. It was shown that the master curve concept is applicable for the fracture mechanical characterisation of material with different microstructures using small test specimens. The influence of the material homogeneity and the test temperature on the resulting reference temperature was investigated.
Keywords: reactor pressure vessel steel, integrity assessment, brittle failure, fracture toughness, Master Curve, Charpy-V test, ductile-to-brittle transition, reference temperature
  • Nuclear Engineering and Design 212 (2002) 115-124

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Publ.-Id: 3469


Uranium(VI) complexation by bacillus species isolated from uranium mining waste pile - a comparative EXAFS study

Hennig, C.; Panak, P.; Reich, T.; Raff, J.; Selenska-Pobell, S.; Bernhard, G.; Nitsche, H.

Certain bacterial strains can selectively accumulate various metal ions from aqueous systems /1/. Recently, it was demonstrated that two Bacillus strains, B. cereus JG-A30 and B. sphaericus JG-A12, recovered from a uranium mining waste site in Germany are able to accumulate selectively a large variety of heavy metals from the drain waters of the waste site /2/. In particular, it was shown that these strains accumulate large amounts of uranium. The aim of this study is the analysis of the structure of uranium complexes formed at vegetative cells and spores of the above mentioned Bacillus strains using extended x-ray absorption fine structure (EXAFS) spectroscopy. Analytical procedures allow separating radial distribution functions from the EXAFS, which contain information on bond lengths and coordination numbers. However, frequently the EXAFS result is dominated mainly by the major coordination type in the sample. A comparison of the determined structural parameters with those of the uranium structure family allows to determine the type of complex formed in the
  • Lecture (Conference)
    BMRI-2 Euroconference on Bacterial-Metal/Radionuclide Interaction, Rossendorf bei Dresden, 30.8.-1.9. 2000

Permalink: https://www.hzdr.de/publications/Publ-3467
Publ.-Id: 3467


Wissensbasierte Massenverlaufsregelung mit einem Schwingrinnenförderer

Dörrer, A.
Für die kontinuierliche gravimetrische Dosierung feiner Pulver im Bereich kleinster Masseströme ( 50mg/s) mittels Dosierwaage und Schwingrinne wurde ein wissensbasierter Dosierregler entworfen, der die Anpassung an die Fließeigenschaften der Dosiergüter durch Insitu-Messung und qualitative Modellierung
erlaubt. Die Regelung erfolgt PC-gestützt mit dem echtzeitfähigem Simulationssystem
DynStar. Die leistungsfähige Fuzzy-Shell erlaubt die effiziente Generierung und Erprobung nichtlinearer Reglerstrukturen. Damit steht ein komfortables und flexibles Werkzeug für die anwendungsorientierte Forschung auf dem Gebiet der Förderung und Dosierung von Pulvern im Kleinstbereich zur Verfügung.
  • Other report
    Arbeitsbericht FWS 00-01 August 2000

Permalink: https://www.hzdr.de/publications/Publ-3465
Publ.-Id: 3465


Optimization of a tunable quasi-monochromatic X-ray source for cell irradiations.

Neubert, W.; Enghardt, W.; Lehnert, U.; Müller, E.; Naumann, B.; Panteleeva, A.; Pawelke, J.
A setup for radiobiological studies using channeling radiation produced at a beamline of the superconducting electron accelerator ELBE has been optimized in order to reduce the bremsstrahlung and neutron background. The electron beam transport was designed using the code package PARMELA. The interaction of the electrons with the elements of the beam delivery and bremsstrahlung production has been calculated by means of GEANT. These results were used as input for EGS4 to calculate dose distributions in a biological specimen.
Keywords: Monte-Carlo simulations, bremsstrahlung, electron beam line, GEANT, EGS4, PARMELA
  • Lecture (Conference)
    Int. Conf. on Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications, 23-26 Oct, 2000, Lisbon, Portugal
    Book of Abstracts (2000) 27-28
  • Book (Authorship)
    A. Kling, F. Barao, M. Nakagawa, L. Tavora, P. Vaz (Eds.), Springer Verlag, Berlin Heidelberg New York (2001) 123-128
  • Contribution to external collection
    Int. Conf. on Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications, 23-26 Oct, 2000, Lisbon, Portugal
    Book of Abstracts (2000) 27-28

Permalink: https://www.hzdr.de/publications/Publ-3464
Publ.-Id: 3464


Untersuchungen zur Förder- und Dosierbarkeit kleiner Mengen feiner Pulver am Schwingförderer - Konzept eines wissensbasieren adaptiven Dosierreglers

Lindau, B.; Dörrer, A.
Die hochgenaue zeitsynchrone Dosierung feiner Pulver im Bereich kleinster Massenströme (< 100 g/h) ist nur durch gravimetrisch geregelte Masse-Verlaufs-Regelung vorteilhaft realisierbar. Das auf Bruttowägung mit Dosierwaagen basierende Verfahren stellt hohe Anforderungen an die Stell- und Messglieder und an die Regelung.
  • Chemie-Ingenieur-Technik

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Publ.-Id: 3463


Photovoltaische Stromversorgung

Rindelhardt, U.
Im Buch werden der Stand und die Perspektiven der photovoltaischen Stromversorgung dargestellt. Ausgehend von der derzeitigen Energieversorgung wird die Notwendigkeit der Erschließung neuer Energiequellen abgeleitet. Im Kapitel 2 wird das Potential der Solarstrahlung dargestellt. Das Kapitel 3 befaßt sich mit der Technik der photovoltaischen Umwandlung. In den beiden abschließenden Kapiteln werden der Aufbau, die Auslegung und der Betrieb sowohl von photovoltaischen Inselanlagen als auch von netzgekoppelten Photovoltaikanlagen beschrieben. Die Möglichkeiten und Grenzen der photovoltaischen Stromversorgung werden aus energiewirtschaftlicher Sicht verdeutlicht.
Keywords: Photovoltaik, Energieversorgung, Energiewirtschaft
  • Book (Authorship)
    B. G. Teubner Stuttgart-Leipzig-Wiesbaden

Permalink: https://www.hzdr.de/publications/Publ-3462
Publ.-Id: 3462


Flash lamp annealing of implantation doped p- and n-6H-SiC

Panknin, D.; Gebel, T.; Skorupa, W.
The electrical properties of Al, B, N implanted 6H-SiC after flash lamp annealing are discussed in comparison with furnace annealing. The electrical activity of Al is for high concentrations distinctly enhanced using flash lamp annealing. For B implanted layers only a soft enhancement is possible using flash lamp annealing but the dopant outdiffusion is strong reduced. N activated by a two step process. A high temperature short time step follow a furnace step at lower temperatures leads to a soft enhanced electrical activation compared to furnace annealing.
Keywords: SiC, doping, ion implantation, short time annealing
  • Materials Science Forum 353-356(2001)587-590

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Publ.-Id: 3461


Crystallisation of Ge nanoclusters in SiO2 caused by electron irradiation in TEM

Klimenkov, M.; Matz, W.; Nepijko, S.; Lehmann, M.
The Ge nanoparticles fabricated by ion implantation technique in SiO2 thin film crystallise after irradiation with high energetic electron beam. The crystallisation process depends on the irradiation dose and intensity. Irradiation with a dose above 6x103 C/cm2 results in cluster growths and above 4x104 C/cm2 in crystallisation. An irradiation of intensity below 150 A/cm2 leads to the crystallisation of Ge nanoparticles in the form of single crystals. For irradiation intensities above this value the formation of twinned and multiply twinned particles (MTP) was observed.
Keywords: nanocluster, crystallisation, transmission electron microscopy
  • Nuclear Instruments and Methods in Physics Research B 179 (2001) 209-214

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Publ.-Id: 3460


Unterstützung der ukrainischen Aufsichtsbehörde bei der Einrichtung einer verbesserten betrieblichen Überwachung für das gesamte KKW Saporoshje

Beyer, M.; Carl, H.; Reitz, T.
Das Mitte der 90er Jahre im KKW Saporoshje als Pilotprojekt für den 5. Block eingerichtete System zur verbesserten betrieblichen Überwachung wurde auf alle 6 Blöcke erweitert und mittels moderner Kommunikationstechnik an das Informations- und Krisenzentrum der ukrainischen Aufsichtsbehörde in Kiew angeschlossen. Die zur Komplettierung des Rechnernetzes am Standort benötigten aktiven Komponenten wurden einvernehmlich spezifiziert, in Deutschland beschafft, im notwendigen Umfang erprobt, in die Ukraine überführt und dem Partner am Einsatzort unentgeltlich überlassen. Nach der entsprechenden Erweiterung der Software für die Informationsverarbeitung, -übertragung und -bewertung können von jedem der sechs WWER-1000 Blöcke 159 sicherheitsrelevante betriebliche und 25 radiologische Messwerte kontinuierlich erfasst, vor Ort in Form von Tabellen, Grafiken und Schemata online dargestellt und bewertet sowie nach Kiew übertragen werden. Damit steht im Informations- und Krisenzentrum in Kiew der gleiche Informationsumfang für Überwachungszwecke zur Verfügung.
Keywords: Ukraine, KKW Saporoshje, Fernüberwachung, Sicherheit
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-297 Juli 2000

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Publ.-Id: 3459


Applying ANSYS/Multiphysics with Extended Creep Capabilities to an Integral Severe Nuclear Accident Experiment

Altstadt, E.; Willschütz, H.-G.
Considering the hypothetical accident scenario of a core melt down for a Light Water Reactor the behaviour of the Reactor Pressure Vessel has to be investigated. The vessel behaviour is governed by multiaxial creep deformation of the three-dimensional vessel with highly non-uniform temperature and stress fields.
Therefore a Finite Element model is developed on the basis of ANSYS/Multiphysics®. Using FLOTRAN® the transient temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are performed applying a creep model which is able to take into account great temperature, stress and strain variations within the model domain.
The user programmable features (UPF) of the finite element code ANSYS® are used to generate a customized ANSYS-executable including a more general creep behaviour of materials and a damage module. The numerical approach for the creep behaviour is not restricted to a single creep law (e.g. strain hardening model) with parameters evaluated from a limited stress and temperature range. Instead of this strain rate - strain relations can be read from external creep data files for different temperature and stress levels.
The damage module accumulates a damage measure based on the creep strain increment and plastic strain increment of the load step and the current fracture strains for creep and plasticity (depending on temperature and stress level). If the damage measure of an element exceeds a critical value this element is deactivated.
Post test calculations of a scaled core melt down experiment FOREVER-C2 were performed. If the temperature field in the vessel wall is fixed along creeping process, the calculated creep curves disagree with the measurement. Considering the time dependent variation of the temperature field, the calculated results show a good agreement with the measurements.
Currently the FE-Model is improved and validated in the frame of further scaled core melt down experiments.
Keywords: Advanced Creep Modelling by User Programmable Features, Integral Severe Nuclear Accident Experiment, Coupling of Thermo-Fluid Dynamic and Structural Mechanical Model
  • Lecture (Conference)
    18. CAD-FEM Users´ Meeting, 20.-22. September 2000, Friedrichshafen am Bodensee, Germany, Proceedings Vol.2, 2.5.5.
  • Contribution to proceedings
    18. CAD-FEM Users´ Meeting, 20.-22. September 2000, Friedrichshafen am Bodensee, Germany, Proceedings Vol.2, 2.5.5.

Permalink: https://www.hzdr.de/publications/Publ-3458
Publ.-Id: 3458


XAS study of acid rock drainage samples from an abandoned Zn-Pb-Ag mine at Freiberg, Germany

Moll, H.; Zänker, H.; Richter, W.; Brendler, V.; Reich, T.; Hennig, C.; Roßberg, A.; Funke, H.; Kluge, A.
Ore crystals in clay play a key role in the sulfide oxidation and water mineralization process in abandoned ore mines. Highly mineralized, red-colored solutions are formed by the weathering of the ore particles which causes acid rock drainage (ARD). Major cationic components (>1 g/l) of the ARD solution under study were Zn, Fe, Mg, Al, and Mn. Important minor components were toxic and heavy metals, e.g., As, Cu, Pb, and Cd. This XAS investigation deals with the in-situ characterization of the near-order surrounding of As in ARD solutions containing colloidal particles as well as with the determination of the particle mineralogy. The atomic surrounding of Fe and As in ARD samples is compared to those found in model compounds. The arsenate seems to be bound to the colloids (iron hydroxy sulfate) in a way similar to that of arsenate binding onto ferrihydrite. The presented study is an example for the broad application of XAS techniques to environmental research.
Keywords: XANES, EXAFS, Fe, As, acid rock drainage, colloids
  • Poster
    Beitrag zur Konferenz Actinide-XAS-2000, 10.-12.09.2000 in Grenoble Proceedings Workshop: "Speciation, Techniques and Facilities for Radioactive Materials at Synchrotron Light Sources", Grenoble; France, 10.-12.09.2000, OECD/NEA Paris, p. 263-26...
  • Contribution to proceedings
    Beitrag zur Konferenz Actinide-XAS-2000, 10.-12.09.2000 in Grenoble Proceedings Workshop: "Speciation, Techniques and Facilities for Radioactive Materials at Synchrotron Light Sources", Grenoble; France, 10.-12.09.2000, OECD/NEA Paris, p. 263-26...

Permalink: https://www.hzdr.de/publications/Publ-3457
Publ.-Id: 3457


High dose implantation in 6H-SiC

Heera, V.; Skorupa, W.; Stoemenos, J.; Pécz, B.
The phase formation in 6H-SiC due to high dose implantation was studied as function of temperature by means of transmission electron microscopy. Two examples demonstrate the feasibility of ion beam synthesis of crystalline phases in 6H-SiC which are epitaxially aligned with the surrounding matrix. In the first example Al+ ions were implanted up to concentrations of 15 at% at temperatures between RT and 800oC. The precipitation of carbon phases due to high dose C+ implantation in 6H-SiC at temperatures between 300°C and 900°C was investigated in the second example.
Keywords: High Dose Implantation, Phase Formation, 6H-SiC, Al, Al4C3, C, Diamond, TEM
  • Contribution to proceedings
    Third European Conference on Silicon Carbide and Related Materials 2000, Silicon Carbide and Related Materials ECSCRM2000, Materials Science Forum Vols. 353-356 (2001) 579-582, Trans Tech Publications

Permalink: https://www.hzdr.de/publications/Publ-3456
Publ.-Id: 3456


Influence of growth parameters and melt convection on the solid-liquid interface during RF-floating zone crystal growth of intermetallic compounds

Hermann, R.; Priede, J.; Behr, G.; Gerbeth, G.; Schultz, L.
The influence of growth parameters and melt convection on the solid-liquid interface of intermetallic compounds grown by the RF-floating zone technique was investigated experimentally as well as numerically. Numerical simulations showed that the heat transfer is strongly influenced by the electromagnetically driven and Marangoni convections whereas both the buoyancy and feed rotation have a negligible effect. It was found experimentally that the coil design, the rod diameter and the length of the molten zone influence the solid-liquid interface shape significantly. The electromagnetically driven convection increases dramatically with increasing zone length due to the rapid increase of the non-uniformity of the magnetic field. The minimisation of the zone length and the application of an after heater reduce concave (towards the melt) interface regions which give rise to polycrystalline segments during RF-floating zone crystal growth of complicated intermetallic compounds. However, the adjustment of a complete convex solid-liquid interface shape in RF-floating zone crystal growth requires some additional melt stirring by magnetic forces.
Keywords: Floating zone technique, Growth parameters, Numerical simulation
  • Journal of Crystal Growth 223 (2001) 577-587

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Publ.-Id: 3455


Neptunium(V) Complexation by Various Humic Acids in Solution Studied by EXAFS and UV-Vis Spectroscopy

Pompe, S.; Schmeide, K.; Reich, T.; Hennig, C.; Funke, H.; Rossberg, A.; Geipel, G.; Brendler, V.; Heise, K. H.; Bernhard, G.
The complexation of neptunium(V) with humic acids at pH 7 was studied by EXAFS and UV-Vis spectroscopy using a natural humic acid from Aldrich as well as a synthetic humic acid model substance (type M42) with well defined functional properties. In addition, we studied the influence of phenolic OH groups on the complexation between humic acids and neptunium(V) in the neutral pH range using Aldrich humic acid in a modified form, i.e., with blocked phenolic OH groups.
The formation of neptunium(V) humate complexes was confirmed for all investigated humic acids by UV-Vis spectroscopy. Neptunium LIII-edge EXAFS spectra were recorded in fluorescence mode at the Rossendorf Beamline (ROBL) at the ESRF in Grenoble. For the first two coordination shells of neptunium(V) the EXAFS spectra were analyzed. The obtained structural information for the axial and equatorial oxygen atoms surrounding the neptunium atom will be presented and compared with results for neptunium(V) hydrates.
Keywords: neptunium, pentavalent, humic acid, complexation, EXAFS, UV-Vis spectroscopy
  • Poster
    2nd Euroconference and NEA Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, Grenoble, France, 10.-12.09.2000.

Permalink: https://www.hzdr.de/publications/Publ-3454
Publ.-Id: 3454


Complexation of Neptunium(IV) by Various Humic Substances Studied by X-Ray Absorption Spectroscopy

Schmeide, K.; Pompe, S.; Reich, T.; Hennig, C.; Funke, H.; Rossberg, A.; Geipel, G.; Brendler, V.; Heise, K. H.; Bernhard, G.
We studied the complexation of neptunium(IV) with natural and synthetic humic and fulvic acids at pH 1 by X-ray absorption spectroscopy. Neptunium LIII-edge X-ray absorption spectra were collected in transmission mode at the Rossendorf Beamline (ROBL) at the ESRF in Grenoble. Furthermore, we studied the interaction of neptunium(IV) with Bio-Rex70, a cation exchange resin having solely carboxylate groups, at pH 1. The structural parameters of the near-neighbor surrounding of neptunium(IV) obtained for the interaction of neptunium(IV) with humic substances and with Bio-Rex70 are compared to obtain information on the nature of functional groups of humic substances responsible for binding neptunium(IV) in the acidic pH range.
The results are also compared with structural parameters obtained for neptunium(IV) hydrates as well as for the interaction of thorium(IV) and hafnium(IV) with humic acid and Bio-Rex70.

Keywords: neptunium, tetravalent, humic substances, complexation, EXAFS
  • Poster
    2nd Euroconference and NEA Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, Grenoble, France, 10.-12.09.2000.

Permalink: https://www.hzdr.de/publications/Publ-3453
Publ.-Id: 3453


Soft hadron production in pp interactions up to ISR energies

Müller, H.
Soft hadron production is described as a two-step process, where the
interaction of the partonic constituents of the colliding hadrons
leads to the production of intermediate subsystems (fireballs), which
decay subsequently into hadrons. The weights of the various final
states are derived from the corresponding phase-space factors modified
by empirical transition elements. The results compare well with data
at energies between particle production thresholds and ISR
energies. Special emphasis is put on correlation data, which offer the
opportunity to shed some light on the question whether particle
production proceeds via fireballs or strings.
  • The European Physical Journal C 18 (2001) 563-576

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Construction and use of an intense positron source at new linac facilities in Germany (- conceptual report -)

Brauer, G.; (Editor)
In this conceptual report the idea to establish an European Positron Source for Applied Research ("EPOS") based on new LINAC facilities in Germany (ELBE/Rossendorf or TTF-DESY/Hamburg) is considered. The report contains not only the outline of obvious applications in atomic physics, materials science and surface physics, but also several new methodical developments which are only possible with an intense positron beam. This opportunity will also allow the use and further development of imaging techniques being of special interest for industrial applications.


Keywords: positron, intense positron beam, linac, atomic physics, materials science, surface physics, image-creating applications
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-295 Juli 2000

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Publ.-Id: 3451


Aufgabenstellung - Validierung - Anwendung von gekoppelten 3D-Kernmodellen und Systemcodes

Weiß, F.-P.; Rohde, U.; Grundmann, U.; Teschendorff, V.; Burtak, F.
100 Wissenschaftler und Ingenieure aus elf europäischen Ländern und den USA waren der Einladung des Institutes für Sicherheitsforschung des Forschungszentrums Rossendorf (FZR) zum Fachtag "Wechselwirkungen zwischen Thermofluiddynamik und Neutronenkinetik" gefolgt. Die Tagung fand vom 31. Januar bis 1. Februar 2000 am FZR statt und wurde gemeinsam von den Fachgruppen "Reaktorphysik" und Thermofluiddynamik" der Kerntechnischen Gesellschaft veranstaltet. In 19 Vorträgen wurden Anforderungen an Sicherheitsanalysen aus der Sicht der Wissenschaft, der Industrie und der Gutachter formuliert. Programmschwerpunkte waren die Entwicklung von Methoden zur Kopplung von 3D Neutronenkinetik und Thermohydraulik, die Validierung der Modelle an Hand von Experimenten und die Anwendung für Sicherheitsanalysen von Leichtwasserreaktoren. Am Ende konnte festgestellt werden, dass mit den gekoppelten neutronenkinetisch-thermohydraulischen Systemcodes eine fortgeschrittene Simulationstechnik zur Verfügung steht, die eine wesentliche Erhöhung der Aussagesicherheit von Störfallsimulationen ermöglicht.
  • atw 45. Jg. (2000) Heft 6 - Juni

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Publ.-Id: 3450


EXAFS investigation of uranium (VI) complexes formed at Acidithiobacillus ferrooxidans types

Merroun, M.; Reich, T.; Hennig, C.; Selenska-Pobell, S.
Uranium (VI) complexes formation at surfaces of Acidithiobacillus ferrooxidans types was studied using uranium LIII-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. In all samples the uranium is coordinated by two axial oxygen atoms (Oax) at distance of 1.77-1.78 Å. The distance between uranium and the equatorial oxygen atoms (Oeq) is 2.35 Å. To within the experimental error, there are no differences in the U-O bond distances between samples from the 3 types of A. ferrooxidans. The coordination number for Oeq is 5-6. The fit to the EXAFS data of samples measured as wet pastes gave the same results as for dried samples. No significant structural differences were observed for the uranium complexes formed by the eco-types of A. ferrooxidans. However, the EXAFS spectra are indicating formation of uranium complexes which are different from those formed by Bacilli /1/.

/1/ C. Hennig et al., EXAFS investigation of uranium(VI) complexes formed at Bacillus cereus and Bacillus sphaericus surfaces, Radiochim. Acta (submitted)

  • Poster
    European Workshop on X-ray Absorption for Biology

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Publ.-Id: 3449


Characterization of Chromium Complexes in Chrome Tannins, Leather, and Gelatin Using Extended X-ray Absorption Fine Structure (EXAFS) Spectroscopy

Reich, T.; Rossberg, A.; Hennig, C.; Reich, G.
Chrome tannage is the most intensively investigated tanning process. Nevertheless, the nature (size) of the chromium - collagen complexes has not been proofed experimentally yet.
We investigated the structure of the chromium complexes in powder and dilute solutions of chromium alum, a basic chrome(III) tannin (Chromosal B), an acetone dehydrated, Chromosal tanned Wet Blue leather, an industrial manufactured leather before and after artificial shrinkage, and gelatin by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy.
It is shown that in solid Chromosal B every Cr atom is surrounded by approximately two other Cr atoms. In 0.2 M Chromosal B solution binuclear, in solid chromium alum and its 0.2 M solution mononuclear chromium complexes are present. In leather and gelatin the bound chromium complexes are approximately binuclear. Partial area shrinkage caused by repeated thermal treatment of the chrome leather did not lead to a significant change of the Cr complex inside the leather. These results support the current theoretical concept of chrome tanning in a direct way and demonstrate the great potential of EXAFS investigations in the leather field.

  • Journal of the American Leather Chemists Association 96, 133-147 (2001)

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Publ.-Id: 3448


Comment on "Behaviour of Europium(III) and its Hydroxo and Carbonate Complexes in a Solvent Extraction System with HDBM in 2 M NaCl at 303 K" by M. Jiménez-Reyes, M. Solache-Rios and A. Rojas-Hernández.

Fanghänel, T.; Neck, V.
In a recent paper [1] the hydrolysis and carbonate complexation of Eu(III) was studied by potentiometric titration of 2 ´ 10-4 M Eu(III) solutions in the range pH = 7 - 13. Under the experimental conditions applied in this study, the Eu(III) concentration exceeds the solubility of Eu(OH)3(s) or EuOHCO3(s) by several orders of magnitude. The formation constants derived for numerous aqueous Eu(III) hydrolysis species and ternary hydroxo-carbonate complexes constants must be considered as erroneous. They are the result of misinterpreting the formation of solid Eu(III) particles as hydrolysis or carbonate complexation in solution.


  • Radiochimica Acta 88, 499-501 (2000)

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