Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33397 Publications

Development of Multi-Physics Code Systems based on the Reactor Dynamics Code DYN3D

Kliem, S.; Gommlich, A.; Grahn, A.; Rohde, U.; Schütze, J.; Frank, T.; Gomez, A.; Sanchez, V.
In the presentation the recent developments of the coupling of the reactor dynamics code DYN3D with the coarse-mesh CFD code FLICA-4 and the CFD code ANSYS CFX are presented. First results of verification calculations for small-size test problems confirm the correctness of the implementation of the coupling.
  • Invited lecture (Conferences)
    Fachtag der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 07.-08.10.2010, Dresden, Deutschland
  • Contribution to proceedings
    Fachtag der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 07.-08.10.2010, Dresden, Deutschland
    Tagungsband des Fachtages der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", CDROM: FZ Dresden-Rossendorf
  • Kerntechnik 76(2011)3, KT100569

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Permalink: https://www.hzdr.de/publications/Publ-14726
Publ.-Id: 14726


Medical Impact of Polynuclear Cluster Compounds

Stephan, H.; Müller, C. E.
Polynuclear metal compounds may have considerable potential as metallic drugs. The most prominent representatives are polyoxometalates which have been investigated since the last third of the 19th century. In addition to applications in catalysis, separation, analysis, and as electron-dense imaging agents, some of these substances have been shown to exhibit biological activity in vitro as well as in vivo ranging from anti-cancer, antibiotic, and antiviral to anti-diabetic effects.1
Polymetalates represent a diverse ensemble of nanostructures with an almost infinite variability of chemical, physical and biological properties. The size of typical covalent bridged cluster compounds is in the range from 1 to 3 nm. The attachment of special surface groups on the periphery of cluster compounds may result in self-assembled non-covalent organized structures larger than 5 nm which are characteristic for bio-molecules, such as enzymes. Cells of mammalian organisms are typically 10 to 30 µm. However, sub-cellular organelle dimensions are smaller and range in sub-µm sizes. This comparison of size dimension illustrates that polymetalates are small enough to allow the cell membrane to be penetrated without too much interference. Evidently, some types of polymetalates are able to be transported into cells, particularly into mitochondria. Our aim is focused on the development of novel cluster compounds with improved chemical and metabolic stability. Furthermore, increased recognition of target biomolecules - such as enzymes - shall be achieved.
On the way to explore the biological activity of polynuclear cluster compounds, we recently recognised polyoxometalates as a new class of potent enzyme inhibitors.2 Certain polymetalates are able to inhibit E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) that are surface-located nucleotide-hydrolyzing enzymes involved in the regulation of signaling cascades by activating P2 (nucleotide) receptors. The most potent compound - described to date – is K6H2[TiW11CoO40] I exhibiting IC50 values which are significantly lower than those of known standard inhibitors. Some compounds are also able to directly interact with P2 receptors. A further promising new class of cluster compounds to permit selective inhibition of E-NTPDases are hexanuclear rhenium complexes with bridging sulfur, selenium and/or tellurium atoms. In this perspective, a broad ensemble of water-soluble octahedral rhenium cluster compounds II becomes available by ligand exchange reactions.3
The paper will give a brief overview about the potential of inorganic cluster compounds in medicine as well as a survey of recent progress that was achieved on E-NTPDase inhibition and P2 receptor antagonism with polymetalates.

[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev.1998, 98, 327-357.
[2] C. E. Müller, J. Iqbal, Y. Baqi, H. Zimmermann, A. Röllich, H. Stephan, Bioorg. Med. Chem. Lett. 2006, 16, 5943-5947.
[3] K. A. Brylev, Y. V. Mironov, S. Kozlova, V. E. Fedorov, S.-J. Kim, H.-J. Pietzsch,
H. Stephan, A. Ito, S. Ishizaka, N. Kitamura, Inorg. Chem. 2009, 48, 2309-2315.
  • Lecture (Conference)
    IWTMC-II International Workshop on Transition Metal Clusters-II, 30.09.-02.10.2010, Rostock, D

Permalink: https://www.hzdr.de/publications/Publ-14725
Publ.-Id: 14725


A novel Dibenzoazacyclooctyne precursor in regioselective Copper-free click chemistry. An innovative 3-step synthesis.

Starke, F.; Walther, M.; Pietzsch, H.-J.
A novel carboxylic acid substituted dibenzoazacyclooctyne precursor has been synthesized using a fast and innovative three-step synthesis. It can be easily converted into the corresponding alkyne through UV-irradiation. Due to its fast and regioselective reaction with azides, the alkyne is a promising agent for copper-free "click chemistry". The second order reaction rate constant was determined by 1H-NMR.
  • Open Access Logo ARKIVOC (2010), 350-359

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Permalink: https://www.hzdr.de/publications/Publ-14724
Publ.-Id: 14724


Nanotribology of lubricated carbon-based nanocoatings

Kunze, T.; Posselt, M.; Gemming, S.; Seifert, G.
Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding lubricated contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency. An additional variation of the tribological characteristics arises due to the presence of the fuel as the lubricant.
The present study employs atomic-scale simulations in order to assist the manufacturing and optimization of functional nanocoatings. Our investigations focus on two basic functional film species - tetrahedral amorphous carbon (ta-C) and transition metal enriched carbon (TM:C) coatings. These films are modeled and studied with the help of bond-order potentials such as the reactive empirical bond-order (REBO) potential [1] for carbon-carbon interaction and the Shibuta potential [2] for TM-carbon interaction. Our simulations also incorporate an adaptive cutoff scheme, which is able to enhance the REBO potential characteristics [3]. Since the tribological properties of lubricated engine parts depend not only on the properties of the nanocoatings but also on the lubricant, the hydrocarbon dodecan is selected as a representative of the fuel in the automotive engines. Preliminary results on the ta-C film morphology and its tribological properties such as friction coefficients with and without lubrication are presented.

[1] D. W. Brenner et al., J. Phys.: Condens. Matter 14 (2002) 783
[2] Y. Shibuta et al., Chem. Phys. Lett. 472 (2009) 200
[3] L. Pastewka et al., Phys. Rev. B 78 (2008) 161402
Keywords: nanotribology, diamond-like carbon, atomistic simulations
  • Poster
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), Symposium Tribology, 04.-08.10.2010, Freiburg, Deutschland
  • Contribution to proceedings
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), 04.-08.10.2010, Freiburg, Deutschland
    Conference Proceedings MMM2010, Stuttgart: Fraunhofer Verlag, 978-3-8396-0166-2, 858

Permalink: https://www.hzdr.de/publications/Publ-14723
Publ.-Id: 14723


Status of atomic-level simulations of solid phase epitaxial recrystallization of amorphous Si

Posselt, M.
In semiconductor technology amorphous Si layers are formed by ion implantation, and during subsequent annealing the solid phase epitaxial recrystallization (SPER) of the amorphous material takes place. In order to simulate the SPER process and to understand its atomic-level mechanisms, classical molecular dynamics calculations are employed since they allow the consideration of several thousand atoms and a time scale up to some hundreds of nanoseconds. In the last decade different authors investigated SPER in Si by this type of simulations, but the critical review shows that their results are not consistent with the experimental data. In most cases the SPER rate was strongly overestimated. Moreover, the results obtained by different groups under virtually equal conditions do not agree. This may be due to the different approaches used to prepare the initial state consisting of an atomic system with a nearly planar amorphous-crystalline interface. The main cause for the disagreement with experimental data is the inaccuracy of the interatomic potentials used in the different studies. The improvements considered in the present work are based on a better description of the amorphous phase using a modified potential without changing the established potential for the single-crystalline material. It is found that amorphous Si with realistic structural and thermodynamic properties can be obtained by certain modifications of known interatomic potentials, but these modifications do not yield the correct SPER rate. However, it is shown that the value of the SPER rate is strongly correlated with the melting temperature of amorphous silicon obtained by the corresponding modified potential. Obviously, this dependence can be explained by the fact that both melting and SPER are essentially determined by the flexibility of atomic bonds. The atomic mechanism of SPER consists in sequential local arrangements of atomic bonds and positions, preferentially along {111} facets or terraces.
Keywords: epitaxial recrystallization, Si, atomistic computer simulations
  • Lecture (Conference)
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), Symposium Microstructure Modeling, 04.-08.10.2010, Freiburg, Deutschland
  • Contribution to proceedings
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), 04.-08.10.2010, Freiburg, Deutschland
    Conference Proceedings MMM2010, Stuttgart: Fraunhofer Verlag, 978-3-8396-0166-2, 509

Permalink: https://www.hzdr.de/publications/Publ-14722
Publ.-Id: 14722


Applications of 100TW class ultrashort-pulse lasers

Schramm, U.
first steps to laser driven radiation oncology
and the future of the Dresden laser lab
  • Lecture (Conference)
    Superstrong fields in plasmas, 03.-08.10.2010, Varenna, Italien

Permalink: https://www.hzdr.de/publications/Publ-14721
Publ.-Id: 14721


Nano-Biotechnologie für den Umweltschutz: Neue photokatalytisch aktive Verbundmaterialien zur Eliminierung von pharmazeutischen Reststoffen (NanoPharm)

Pollmann, K.; Raff, J.
Vorstellung des BMBF-geförderten "NanoPharm"-Projekts
  • Lecture (others)
    4. MITTELDEUTSCHES NETZWERKTREFFEN, 30.11.2010, Magdeburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14720
Publ.-Id: 14720


Bioinspired nanomaterials

Raff, J.
Protecting the environment and saving resources are two of the society’s challenges of the 21th century. Therefore interesting insights coming also from nature. As many bacteria and archaea live in extreme habitats, they developed early in evolution so called surface layers (S-layers), which function as intelligent interface between cells and their environment. One function of such S-layers is the binding of toxic metals and metalloids and thusly the protection of the cells from being damaged by these elements and their compounds. This makes, together with their self-assembling properties, S-layer very interesting building blocks for the construction of new bioinspired nanomaterials for different technical applications. Currently under development are materials for the selective metal-binding for the removal of toxic metals and metalloids or the recovery of precious metals, highly efficient (photo)catalysts for the elimination of organic pollutants or organic synthesis and new biosensors for chemicals or pharmaceuticals.
Keywords: S-layer, nanomaterials
  • Lecture (others)
    nanoSeminar des Instituts für Werkstoffwissenschaft, TU Dresden, 11.11.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14719
Publ.-Id: 14719


Domains and Dynamics in NiMnGa

Neudert, A.; Schäfer, R.; McCord, J.
Magnetic domains in the shape memory alloy NiMnGa are investigated using magneto-optical indicator film technique. Depending on whether the twin boundary is moved by applying mechanical stress or magnetic fields a different domain state is found after twin boundary motion.
  • Lecture (Conference)
    SPP Convention Tutzing, 29.09.2010, Tutzing, Germany

Permalink: https://www.hzdr.de/publications/Publ-14718
Publ.-Id: 14718


Local patterning of damping by ion-irradiation In ferromagnetic-antiferromagnetic thin films

McCord, J.; Mönch, I.; Strache, T.; Fassbender, J.ORC; Mattheis, R.
The control of the effective magnetic anisotropy, saturation magnetization as well as the dynamic magnetic properties in ferromagnetic thin films is of significant importance for most applications in spin electronics. The two materials’ parameters which control the dynamic response of soft magnetic thin films are the precessional frequency f_res and the effective damping parameter alpha. Whereas anisotropy and saturation magnetization together determine the precessional frequency of the films, the magnetic damping parameter cannot be varied easily. However it was shown that exchange coupled ferromagnetic/antiferromagnetic (F/AF) systems exhibit strong changes in f_res and alpha independent of the occurrence of exchange bias [1, 2]. On the other hand, ion irradiation of magnetic thin films [3] has been shown to provide an alternative method to alter soft magnetic properties of magnetic multilayer films due to ion induced changes in the interfacial structure. Here we use Ni-ion irradiation to control the dynamic magnetic properties in Ni81Fe19/IrMn/Ni81Fe19 structures in a controlled way. We show that for very thin AF layers alpha can be increased significantly [4]. Selecting an IrMn thickness below the onset of exchange bias, it is possible to solely alter alpha. This effect is reversible by low fluence Ni ion irradiation without changing the composition of the ferromagnetic alloy and thus can be used to adjust alpha over a wide range. As a consequence, the method can be used to laterally pattern samples only by the damping parameter. As shown in Fig. 1 the overall integral damping parameter then is determined by the relative fraction of materials with high and low damping parameter. alpha is thereby varied linearly without any significant change in f_res. The demonstrated paths of film alteration by ion irradiation provide an additional degree of freedom for the tailoring of dynamic magnetic properties of softmagnetic thin films. The method not only allows for general adjustment of magnetic properties, but also for a local setting of dynamic magnetic properties.
This work was supported by the German Science Foundation DFG under grant no. MC9-8/2.

[1] J. McCord et al., Phys. Rev. B 70, 094420 (2004)
[2] J. McCord et al., Phys. Rev. B 75, 134418 (2007).
[3] J. Fassbender and J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
[4] J. McCord, et al., Appl. Phys. Lett. 92 162506 (2008).
  • Lecture (Conference)
    IEEE 7th International Symposium on Metallic Multilayers (MML2010), 20.-24.09.2010, Berkeley, USA

Permalink: https://www.hzdr.de/publications/Publ-14717
Publ.-Id: 14717


Domain width effects on the magneto-dynamic response of CoFeB element arrays

Patschureck, C.; McCord, J.; Schäfer, R.; Mattheis, R.; Schultz, L.
Understanding the role of the magnetic domain structure on the magneto-dynamic properties of patterned magnetic thin film structures is crucial for the optimization of devices, e.g. recording heads and integrated inductors. Arrays of rectangular amorphous Co40Fe40B20 elements of micron size, a separation to width ratio of 1.5 and a thickness of 60 nm have been fabricated. Magneto-optical Kerr microscopy was used to study the domain structure. At zero field closure domain patterns are present whereas the domain width was systematically altered by varying the magnetic field history. The magneto dynamic response of different domain patterns with adjusted domain width was measured using pulsed inductive microwave magnetometry. We show that the resonance frequency is the lowest for broad closure domain structures and increases when the domain width is decreased.
  • Lecture (Conference)
    Joint European Magnetic Symposia JEMS 2010, 25.08.2010, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-14716
Publ.-Id: 14716


Spatially controlled manipulation of damping in ferromagnetic thin films

McCord, J.; Strache, T.; Mönch, I.; Fassbender, J.ORC; Mattheis, R.
The control of dynamic magnetic properties in ferromagnetic thin films is of significant importance for applications in spin electronics. We demonstrate the use of low fluence Ni-ion irradiation to locally and solely tailor the magnetic damping parameter e in ferromagnetic-antiferromagnetic Ni81Fe19/IrMn/Ni81Fe19 sandwich structures. The overall relaxation time then depends on the relative fraction of the phases with different e , which thereby can be controlled without changing the precessional frequency. The superposition of alpha is confirmed by modeling of the dynamic response. The demonstrated path of film engineering by local ion irradiation [J. Fassbender, J. McCord, JMMM 320 (2008) 579] provides an additional degree of freedom for the local tailoring of dynamic magnetic properties of soft-magnetic thin films.
  • Lecture (Conference)
    Joint European Magnetic Symposia JEMS 2010, 27.08.2010, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-14715
Publ.-Id: 14715


P0806 Verfahren und Anordnung zum Nachweis von Östrogen in wässrigen Lösungen

Cherkouk, C.; Rebohle, L.; Skorupa, W.
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zum schnellen Nachweis von Östrogen in wässrigen Lösungen vor Ort zu realisieren. Der Nachweis basiert auf einer Fluoreszenzanalyse, wobei eine integrierte Lichtquelle mit einer bioaktiven Schicht auf deren Oberfläche verwendet wird. Die bioaktive Schicht wird durch ein spezielles Hybridisierungs- und Silanisierungsverfahren erzeugt. Die Messung erfolgt durch die optische Detektion farbstoffmarkierter Hormonmoleküle, die nach einem bestimmten Messprotokoll die Rezeptoren belegen, die noch nicht durch Hormone aus der Messprobe gesättigt worden sind.
  • Patent
    Anmeldung: DE102008024526 A1 2009/12/03

Permalink: https://www.hzdr.de/publications/Publ-14714
Publ.-Id: 14714


Optical and microstructural properties of self-assembled InAs quantum structures in silicon

Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Wójtowicz, A.; Zhou, S. Q.; Kanjilal, A.; Shalimov, A.; Skorupa, W.; Zuk, J.
The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Samples were characterized by micro-Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized:quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optic (TO) and longitudinal optic (LO) InAs single-phonon modes, respectively. The narrow PL band at around 1.3 mm due to the excitation of InAs QDs with an average diameter 7.5 ± 0.5 nm was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The lattice constant of the NPs increases from 6.051 to 6.055 Ǻ with the annealing temperature increasing from 1100 to 1200 oC due to network relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs.
Keywords: InAs, nanopyramid, quantum dots, flash lamp annealing, ion implantation
  • Poster
    E-MRS 2010 Spring Meeting, 07.-11.06.2010, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-14713
Publ.-Id: 14713


Electro-Optical Properties of Solar Cell Emitters Fabricated by Plasma Immersion Ion Implantation and Flash Lamp Millisecond Annealing

Prucnal, S.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.
Both mono- and multicrystalline p-type silicon wafers were used for the phosphorous ion implantation. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. It is demonstrated that FLA at 800 oC for 20 ms even without preheating is sufficient to recrystallized implanted silicon. The highest recrystallization and the lowest resistivity were obtained after annealing at 1200 oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P - cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: c-Si, mc-Si, ion implantation, FLA, solar cells
  • Poster
    26th European Photovoltaic Solar Energy Conference and Exhibition (26th EU PVSEC), 05.-09.09.2010, Valencia, Spain

Permalink: https://www.hzdr.de/publications/Publ-14712
Publ.-Id: 14712


P0801 Anordnung zur dreidimensionalen Elektronenstrahltomographie

Hampel, U.
Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Röntgen-Computertomographie anzugeben, die eine kontinuierliche dreidimensionale Abbildung des Untersuchungsobjektes bzw. eines Teilvolumens des Untersuchungsobjektes bei hoher zeitlicher und räumlicher Auflösung gestattet, wobei mit hoher räumlicher Auflösung sowohl eine hohe Auflösung innerhalb der Schnittebene als auch in axialer Richtung definiert ist.
  • Patent
    Anmeldung: DE 102008005718A1 2009/07/30
  • Patent
    Anmeldung: WO 2009092372A1: Offenlegung-30.07.2009; Nationaliserung in US, EP

Permalink: https://www.hzdr.de/publications/Publ-14711
Publ.-Id: 14711


Solar cell emitters fabricated by flash lamp millisecond annealing

Prucnal, S.; Shumann, T.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.
Phosphorous ion implantation was used for the emitter formation in mono- and multicrystalline silicon solar cells. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800°C for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200°C for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: Solar cells, silicon, Flash Lamp Annealing
  • Open Access Logo Acta Physica Polonica A 120(2011)1, 30-34

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Permalink: https://www.hzdr.de/publications/Publ-14710
Publ.-Id: 14710


Optical and microstructural properties of In(As, N) quantum structure made by ion implantation and flash lamp processing

Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Wójtowicz, A.; Kanjilal, A.; Shalimov, A.; Skorupa, W.; Żuk, J.
The In(As, N) quantum structures were formed in silicon, SiO2 and Si3N4 films by sequential ion implantation and subsequent thermal annealing. Samples were characterized by -Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized: quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The narrow PL band at around 1.3 m from the InAs QDs with an average diameter 7.5 ± 0.5 nm was observed.
The InAs NPs were found only in samples annealed for 20 ms at temperature range from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by high resolution transmission electron microscopy (HRTEM) (see Fig. 1) and X-ray diffraction (XRD). The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The InAs nanopyramids grow in silicon due to liquid phase epitaxy. The InN crystals are formed on the top of silicon nitride layer due to outdiffusion of indium and in Si3N4 film. The PL measurements shows narrow band at around 1.35 m originated from hexagonal InN nanocrystals due to quantum confinement size effect. -Raman scattering study shows two peaks at 495 and 588 cm-1, which correspond to (TO) of E2h and (LO) of A1 phonon modes, respectively.
Keywords: InAs, InN, Quantum dots, photoluminescence, FLA
  • Lecture (Conference)
    VIII-th International Conference Ion Implantation and Other Applications of Ions and Electrons, 14.-17.06.2010, Kazimierz Dolny, Poland

Permalink: https://www.hzdr.de/publications/Publ-14709
Publ.-Id: 14709


P0808 Verfahren und Anordnung zur Reinigung des Reaktionsgemisches bei der Herstellung von Radiopharmaka

Füchtner, F.; Mäding, P.; Preusche, S.; Zessin, J.
Die Erfindung betrifft die Herstellung von Radiopharmaka, insbesondere in Verfahren, und eine Anordnung zur Reinigung des Reaktionsgemisches bei der Herstellung von Radiopharmaka, insbesondereF-markierte Radiopharmaka, wie z. B. [F]FDOPA und [F]OMFD sowie [F]FMeMcN. Erfindungsgemäß wird zur Reinigung des Raktionsgemisches eine Vorsäule als Vorreinigungssäule, gefüllt mit RP-Material (Reversed Phase Material), zur Abtrennung des bei der Reaktion verwendeten Lösungsmittels (Matrix) bzw. unerwünschter Nebenprodukte verwendet, während die eigentliche chromatographische Trennung des Reaktionsgemisches auf einer HPLC-Säule, bevorzugt einer RP-HPLC-Säule, durchgeführt wird.
  • Patent
    Anmeldung: DE 102009009344 A1 2010/09/02
  • Patent
    Anmeldung: WO201088901A1 2010/02/05

Permalink: https://www.hzdr.de/publications/Publ-14708
Publ.-Id: 14708


Magnetic Anisotropy of Thin Magnetic Films on Nanometer Scale Silicon Ripples

Ball, D.; Liedke, M. O.; Lenz, K.; Fritzsche, M.; Yilgin, R.; Keller, A.; Ranjan, M.; Facsko, S.; Fassbender, J.ORC
Ion beam erosion techniques allow for the creation of well-ordered substrate ripples with nanometer periodicity. Moreover, the periodicity can be tuned by changing the ion beam energy over a wide range [1]. The ripple pattern is directly transferred into films grown on these substrates. This offers the possibility of tailoring the magnetic properties by inducing additional magnetic anisotropy due to the structural modifications.
We study the influence of rippled vs. flat Si substrates for 10 nm thin Fe and Co films, as well as technologically relevant Heusler alloys (Fe3Si and Co2FexMn1-xSi). The magnetic anisotropy is measured by frequency and angle dependent vector network analyzer ferromagnetic resonance. The ripple morphology of the magnetic layers induces a strong uniaxial magnetic anisotropy.
Keywords: Vector network analyzer ferromagnetic resonance, Co2FexMn1-xSi, Fe3Si, rippled morphology
  • Poster
    Nanofair, 06.-07.07.2010, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-14707
Publ.-Id: 14707


P0802 Hochgeordnete Nanostrukturen und Sensor und deren Verwendung

Pollmann, K.; Raff, J.; Fahmy, K.
Die vorliegende Erfindung betrifft eine hochgeordnete Nanostruktur und Sensor, in der bzw. dem organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül haben, geordnet gebunden sind, und deren Verwendung. Anwendungsgebiet dafür finden sich in der Biotechnologie, Verfahrenstechnik, Umwelttechnik und Pharmazie, insbesondere bei der Herstellung von Biosensoren, in der biomedizinischen Analytik, bei der Beseitigung von Schadstoffen und Pathogenen, in der DNA-Analytik, für die Herstellung von Filtermaterialien, für Separationsverfahren, für Katalysatoren und in der medizinischen Therapie. Die Aufgabe der Erfindung ist es, eine Struktur zur Verfügung zu stellen, in der organische Molekülgruppen, insbesondere Molekülgruppen, die spezifische Bindungseigenschaften haben, geordnet gebunden sind, und dadurch die von den organischen Molekülgruppen gebundenen Substanzen in die Nähe funktioneller Bestandteile zu bringen. Dies wird gelöst durch eine Nanostruktur, die selbstorganisierende Proteine, an die Aptamere oder andere organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül aufweisen, gebunden sind, und an die selbstorganisierenden Proteine gebundene anorganische Nanopartikel enthält.
  • Patent
    Anmeldung: DE 102008014298 A1 2009/09/24
  • Patent
    Anmeldung: EP 2101175 A1 2009/09/16

Permalink: https://www.hzdr.de/publications/Publ-14706
Publ.-Id: 14706


Solar cell emitters fabricated by plasma immersion ion implantation and flash lamp millisecond annealing

Prucnal, S.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.
Both mono- and multicrystalline p-type silicon wafers were used for the implantation of phosphorous. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800oC for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: solar cells, FLA,silicon
  • Poster
    VIII-th International Conference Ion Implantation and Other Applications of Ions and Electrons, 14.-17.06.2010, Kazimierz Dolny, Poland

Permalink: https://www.hzdr.de/publications/Publ-14705
Publ.-Id: 14705


Formation of InAs quantum dots in silicon by sequential ion implantation and flash lamp annealing

Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Zhou, S. Q.; Kanjilal, A.; Zuk, J.; Skorupa, W.
InAs quantum dots (QDs) were successfully formed in single-crystalline Si by sequential ion implantation and subsequent milliseconds range flash lamp annealing (FLA). Samples were characterized by μ-Raman spectroscopy, Rutherford Backscattering Spectrometry (RBS) high-resolution transmission electronmicroscopy (HRTEM) and low temperature photoluminescence (PL). The Raman spectrum shows two peaks at 215 and 235 cm−1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The PL band at around 1.3 μm originates from the InAs QDs with an average diameter 7.5±0.5 nm and corresponds to the increased band gap energy due to the strong quantum confinement size effect. The FLA of 20 ms is sufficient for InAs QDs formation. It also prevents the out-diffusion of implanted elements.
Moreover, the silicon layer amorphized during ion implantation is recrystallized by solid-phase epitaxial regrowth during FLA.
Keywords: InAs, Quantum Dots, Si, photoluminescence, FLA

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Permalink: https://www.hzdr.de/publications/Publ-14704
Publ.-Id: 14704


Comparison of the room temperature 1.53 μm Er photoluminescence from flash lamp and furnace annealed Er-doped Ge-rich SiO2 layers

Kanjilal, A.; Prucnal, S.; Rebohle, L.; Voelskow, M.; Helm, M.; Skorupa, W.
The furnace and flash-lamp annealing (FLA) temperature dependent variation in the room temperature 1.53 μm Er photoluminescence (PL) from Er-doped Ge-rich SiO2 layers is investigated. The appearance of the 1.53 μm Er PL is discussed in the framework of the phonon-assisted fluorescent resonant energy transfer from Ge-related luminescence-centers (LCs) to the Er3+. Detailed analyses suggest that in case of FLA the decrease in the 1.53 μm Er PL intensity is governed by the temperature dependent recrystallization of Ge nanoclusters, while for furnace-annealing it is associated with the reduction in the LC-Er3+ coupling due to Ge out-diffusion and the formation of Er-rich clusters with increasing temperature.
Keywords: rare earth, electroluminescence, MOSLED, Flash Lamp Annealing

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Publ.-Id: 14703


Infrared magneto-spectroscopy using quantum cascade lasers

Drachenko, O.; Winnerl, S.; Schneider, H.; Helm, M.; Leotin, J.
We present a magneto-transmission experimental set up covering spectral region from 5 to 120 µm. Interchangable quintum cascade lasers are used as an excitation sources. Performance of the setup is illustrated via cyclotron resonance studies of InGaAs/GaAs QWs under magnetic fields up to 60T
Keywords: Cyclotron resonance, quantum cascade laser, high magnetic fields
  • Lecture (Conference)
    The 35th International Conference on Infrared, Millimeter and THz Waves (IRMMW-THz 2010), 05.-10.09.2010, Rome, Italy
  • Contribution to proceedings
    The 35th International Conference on Infrared, Millimeter and THz Waves (IRMMW-THz 2010), 05.-10.09.2010, Rome, Intaly: IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 978-1-4244-6657-3

Permalink: https://www.hzdr.de/publications/Publ-14702
Publ.-Id: 14702


Nucleation of copper-vacancy clusters in bcc-Fe: An atomistic study

Al-Motasem, A. T.; Posselt, M.; Bergner, F.
Copper-rich precipitates are assumed to be the main cause of hardening and embrittlement of Cu-bearing reactor pressure vessel steels since they act as obstacles to dislocation motion within the grains of the polycrystalline bcc-Fe. Multiscale modeling contributes to a better understanding of point-defect-enhanced formation of these clusters during reactor operation. Rate theory is an efficient tool to simulate the cluster evolution on realistic time and length scales. However, many parameters used in rate theory, such as the diffusion coefficients of mobile species and the free binding energies of clusters, are not very well known from experimental investigations. Atomic-level computer simulations can provide these data. In the present work the nucleation free energy is determined for pure copper and pure vacancy clusters as well as for mixed clusters up to a maximum cluster size of 200. The energetics of the coherent CunVm clusters in bcc-Fe is obtained using a combination of on-lattice Monte Carlo simulations and off-lattice molecular dynamics. The most recent Fe-Cu interatomic potential by Pasianot and Malerba [1] is employed in the calculations.
[1] R. C. Pasianot and L. Malerba, J. Nucl. Mater. 360, 118 (2007).
Keywords: Lattice Monte Carlo, Nucleation of Cu-vacancy Cluster, free binding energy.
  • Poster
    Nuclear Materials 2010, An international conference in association with Journal of Nuclear Materials, 04.-07.10.2010, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-14701
Publ.-Id: 14701


Traumatic Brain Injury Elicits Similar Alterations in α7 Nicotinic Receptor Density in Two Different Experimental Models

Hoffmeister, P.-G.; Donat, C. K.; Schuhmann, M. U.; Voigt, C.; Walter, B.; Nieber, K.; Meixensberger, J.; Bauer, R.; Brust, P.
Traumatic brain injury (TBI) is a major cause of death and disability worldwide, especially in children and young adults. Previous studies have shown alterations in the central cholinergic neurotransmission after TBI. We therefore determined α7 nicotinic acetylcholine receptor (nAChR) densities in newborn piglets and adult rats after experimental TBI. Thirteen newborn piglets (post-TBI survival time: 6 h) underwent fluid percussion (FP) injury
(n = 7) or sham operation (n = 6). Furthermore, adult rats randomized into three groups of post-TBI survival times (2, 24, 72 h) received controlled cortical impact injury (CCI, n = 8) or sham operation (n = 8). Brains were frozen, sagittally cut and incubated with the α7-specific radioligand [125I]a-bungarotoxin for autoradiography. In injured newborn piglets, decreased α7 receptor densities were observed in the hippocampus (-38%), the hippocampus CA1 (-40%), thalamus (-30%) and colliculus superior (-30%). In adult rats, CCI decreased the receptor densities (between -16 and -47%) in almost any brain region within 2 and 24 h. In conclusion, widespread and significantly lowered α7 nAChR densities were demonstrated in
both TBI models. Our results suggest that a nearly similar TBI-induced decrease in the α7 density in the brain of immature and adult animals is found, even with the differences in species, age and experimental procedures. The alterations make the α7 nAChR a suitable target for drug development and neuroimaging after TBI.
Keywords: Traumatic brain injury; α7 nAChR; Autoradiography; Cholinergic system; α-Bungarotoxin

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Publ.-Id: 14700


Texture development, microstructure and phase transformation characteristics of sputtered Ni-Ti Shape Memory Alloy films on TiN<111>

Martins, R. M. S.; Schell, N.; Reuther, H.; Pereira, L.; Mahesh, K. K.; Silva, R. J. C.; Fernandes, F. M. B.
Near equiatomic Ni–Ti films have been deposited by magnetron co-sputtering on TiN films with a topmost layer formed by b111N oriented grains (TiN/SiO2/Si(100) substrate) in a chamber installed at a synchrotron radiation beamline. In-situ X-ray diffraction during Ni–Ti film growth and their complementary ex-situ characterization by Auger electron spectroscopy, scanning electron microscopy and electrical resistivity measurements during temperature cycling have allowed us to establish a relationship between the structure and processing parameters. A preferential development of b110N oriented grains of the B2 phase since the beginning of the deposition has been observed (without and with the application of a substrate bias voltage of −45 and −90 V). The biaxial stress state is considerably influenced by the energy of the bombarding ions, which is dependent on the substrate bias voltage value applied during the growth of the Ni–Ti film. Furthermore, the present work reveals that the control of the energy of the bombarding ions is a promising tool to vary the transformation characteristics of Ni–Ti films, as shown by electrical resistivity measurements during temperature cycling. The in-situ study of the structural evolution of the growing Ni–Ti film as a consequence of changing the Ti:Ni ratio during deposition (on a TiNb111N layer) has also been performed. The preferential growth of b110N oriented grains of the Ni–Ti B2 phase has been as well observed despite the precipitation of Ti2Ni during the deposition of a Ti-rich Ni–Ti film fraction. Functionally graded Ni–Ti films should lead to an intrinsic “twoway” shape memory effect which is a plus for the miniaturization of Ni–Ti films based devices in the field of micro-electro-mechanical systems.

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Publ.-Id: 14699


Enantioselective σ1 receptor binding and biotransformation of the spirocyclic PET tracer 1’-Benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine]

Wiese, C.; Große Maestrup, E.; Schepmann, D.; Grimme, S.; Humpf, H.-U.; Brust, P.; Wünsch, B.
It was shown that racemic (±)-2 [1’-benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine], WMS-1813] represents a promising positron emission tomography (PET) tracer for the investigation of centrally located σ1 receptors. To study the pharmacological activity of the enantiomers of 2, a preparative HPLC separation of (R)-2 and (S)-2 was performed. The absolute configuration of the enantiomers was determined by CD-spectroscopy together with theoretical calculations of the CD-spectrum of a model compound. In receptor binding studies with the radioligand [3H]-(+)-pentazocine, (S)-2 was thrice more potent than its (R)-configured enantiomer (R)-2. The metabolic degradation of the more potent (S)-enantiomer was considerably slower than the metabolism of (R)-2. The structures of the main metabolites of both enantiomers were elucidated by determination of the exact mass using an Orbitrap-LC-MS system. These experiments showed a stereoselective biotransformation of the enantiomers of 2.
Keywords: σ1 receptor ligands; PET tracer; resolution; CD spectroscopy; enantioselective receptor binding; enantioselective metabolism

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Publ.-Id: 14698


Hyperon production in Ar + KCl collisions at 1.76A GeV

Agakishiev, G.; Balanda, A.; Bannier, B.; Bassini, R.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Huck, P.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kaempfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Kruecken, R.; Kuehn, W.; Kugler, A.; Kurepin, A.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Mishra, D.; Moriniere, E.; Mousa, J.; Muentz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez-Cavalcanti, T.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wendisch, C.; Wisniowski, M.; Wojcik, T.; Wuestenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.
We present transverse momentum spectra, rapidity distribution and multiplicity of Lambda-hyperons measured with the HADES spectrometer in the reaction Ar(1.76A GeV)+KCl. The yield of Xi- is calculated from our previously reported Xi-/(Lambda+Sigma0) ratio and compared to other strange particle multiplicities. Employing a strangeness balance equation the multiplicities of the yet unmeasured charged Sigma hyperons can be estimated. Finally a statistical hadronization model is used to fit the yields of pi-, K+, K0s, K-, phi, Lambda and Xi-. The resulting chemical freeze-out temperature of T=(76+-2) MeV is compared to the measured slope parameters obtained from fits to the transverse mass distributions of the particles.

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Publ.-Id: 14696


Energetics and kinetics of defects, impurities, nanostructures and interfaces

Posselt, M.
Computer simulations using classical interatomic potentials are an efficient and promising tool to investigate and understand atomic-level properties and processes in advanced materials. They allow the consideration of length and time scales which are often hardly accessible by experiments. However, the accuracy of the interatomic potentials employed in such type of simulations determines decisively the quality of the obtained results. Therefore, these potentials must be continuously improved and evaluated.
In the present contribution three applications of atomistic computer simulations are illustrated. The focus is on energetics and kinetics of defects, impurities, nanostructures and interfaces in materials for micro- and nanoelectronics and in structural materials for fission reactors. Implications of the simulation results for the explanation of experimental findings are discussed.

The first example deals with molecular dynamics simulations on basic migration mechanisms of mono- and di-(self-)interstitials in Si. Both the atomic mobility due to the presence of the defect and the defect mobility itself are determined. The mechanism of di-interstitial migration depends on temperature, in contrast to that of the mono-interstitial.

In the second example amorphous Si and Ge as well as their solid-phase epitaxial recrystallization (SPER) are considered. Results obtained by different interatomic potentials are compared. The molecular dynamics simulations yield amorphous material with realistic structural and thermodynamic properties, but the SPER rate is strongly overestimated. It is shown that a more realistic SPER rate can be obtained using a modified interatomic potential which yields a higher melting temperature of the amorphous phase. This is explained by the fact that both melting and SPER are essentially determined by the flexibility of atomic bonds.

The subject of the third example is the formation of coherent Cu-rich precipitates in bcc-Fe, i.e. nanostructures containing Cu and vacancies. For pure vacancy and pure Cu clusters as well as for mixed clusters up to a maximum size of 200 the free binding energy and nucleation free energy are determined, using a combination of on-lattice Metropolis Monte Carlo simulations and off-lattice molecular dynamics calculations. The data which are obtained for the binding energy of a single Cu atom and a single vacancy to a cluster are important input parameters of the rate theory. This type of simulation is an efficient multi-scale modeling tool to simulate the cluster evolution on realistic length and time scales.
Keywords: energetics and kinetics, defects, impurities, nanostructures, computer simulation, classical interatomic potential
  • Invited lecture (Conferences)
    11th IUMRS International Conference in Asia, Symposium T: Multi-scale Modeling and Simulation of Materials, 25.-28.09.2010, Qingdao, China

Permalink: https://www.hzdr.de/publications/Publ-14695
Publ.-Id: 14695


Nucleation of Cu-vacancy and Ni-vacancy clusters in bcc-Fe

Al-Motasem, A. T.; Posselt, M.; Bergner, F.
Experimental investigations revealed that both the impurity Cu and the alloying element Ni may contribute to hardening and embrittlement of reactor pressure vessel (RPV) steels during the irradiation by fast neutrons. The irradiation-induced supersaturation of vacancies and self-interstitials amplifies the diffusion of the foreign atoms in bcc-Fe and causes the formation of nanosized Cu- or Ni-rich clusters which act as obstacles to dislocation motion within the grains of the polycrystalline matrix. The concentration of Cu in RPV steels is typically higher than its solid solubility and, therefore, irradiation-enhanced formation of Cu-rich precipitates is observed. Measurements showed that these clusters may not only consist of pure Cu but also include vacancies [1]. On the other hand, the Ni concentration is typically below its solubility limit. That means, any formation of Ni-rich clusters as found in [2] for neutron-irradiated binary Fe-Ni alloys is essentially irradiation-induced. Obviously, these clusters must contain additional species in order to be stable. Small-angle neutron scattering analysis [2] indicated that vacancies could be the other constituent.
In the present work atomistic computer simulations using the ternary Fe-Cu-Ni interatomic potential by Bonny et al. [3] are employed to investigate the thermodynamics of Cu-vacancy and Ni-vacancy precipitates in bcc-Fe. The nucleation free energy of the clusters is determined by the energy and the entropy change due to precipitation using isolated (diluted) Cu and Ni atoms as well as vacancies as the reference. In agreement with indications from measurements the nanoclusters are assumed to have the bcc structure of the iron matrix. The binding energy of the most stable cluster configurations is calculated by simulated annealing within the framework of on-lattice Metropolis Monte Carlo simulations and by subsequent relaxation using off-lattice molecular dynamics calculations.
[1] Q. Xu, T. Yoshiie, K. Sato, Phys. Rev, B 73 (2006) 134115.
[2] F. Bergner, A. Ulbricht, M. Hernandez-Mayoral, P. K. Pranzas, J. Nucl. Mater. 374 (2008) 334.
[3] G. Bonny, R. C. Pasianot, N. Castin, L. Malerba, Phil. Mag. 89 (2009) 3531.
Keywords: atomic simulation, cu-v clusters, formation energy, binding energy
  • Lecture (Conference)
    the 10th International Conference on Computer Simulation of Radiation Effects in Solids, 19.-23.07.2010, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-14694
Publ.-Id: 14694


Thermodynamics of nanoclusters in bcc-Fe containing copper, nickel and vacancies

Al-Motasem, A. T.; Posselt, M.; Talati, M.; Bergner, F.
Reactor pressure vessel (RPV) steels consist of polycrystalline bcc-Fe with different alloying elements, e.g. Ni, and different impurities, e.g. Cu. The continuous irradiation by fast neutrons leads to a supersaturation of vacancies and self-interstitials which enhances the diffusion of the foreign atoms and causes the formation of nanosized clusters. The interaction of dislocations with these precipitates is considered to be the main cause of hardening and embrittlement of RPV steels. In order to model the evolution of the nanoclusters under irradiation at typical temperatures by rate theory the dependence of their nucleation free energy on cluster size and composition must be known. In the present work atomic-level computer simulations are employed to determine these data since they are hardly obtainable by experimental investigations. The ternary Fe-Cu-Ni interatomic potential by Bonny et al. [1] is used in order to consider the thermodynamics of nanoclusters which may consist of the two foreign species and vacancies. In particular the influence of Ni on the formation of clusters containing Cu and vacancies is investigated since previous theoretical [1] and experimental [2,3] studies indicated synergistic effects. The nucleation free energy of the clusters is determined by the energy and the entropy change due to precipitation using isolated (diluted) Cu and Ni atoms as well as vacancies as the reference. In agreement with experimental observations the nanoclusters are assumed to have the bcc structure of the iron matrix. The energy and entropy contributions are calculated using combinations of on-lattice Monte Carlo simulations and off-lattice molecular dynamics calculations.
[1] G. Bonny et al., Phil. Mag. 89 (2009) 3531.
[2] J. T. Buswell et al., Effects of Radiation on Materials: 14th Int. Symp. (Vol. II), ASTM STP 1046, Philadelphia, 1990, p.127.
[3] F. Bergner et al., J. Nucl. Mater. (2009) in press
Keywords: atomistic modeling, v-Cu-Ni cluster, thermodynamic stability, monomer binding energy.
  • Lecture (Conference)
    The fifth International Conference on Multiscale Materials Modeling (MMM-2010), 04.-08.10.2010, Frieburg, Germany, 04.-08.10.2010, Freiburg, Germany
  • Contribution to proceedings
    The fifth international conference on Multiscale Materials Modeling , Freiburg-Germany, 04.-08.10.2010, Freiburg, Germany
    MMM2010 Multiscale Materials Modeling, 978-3-8396-0166-2

Permalink: https://www.hzdr.de/publications/Publ-14693
Publ.-Id: 14693


3D-Visualisierung von Fluidströmungen in Salinargestein mittels Positronen-Emissions-Tomographie

Wolf, M.; Kulenkampff, J.; Enzmann, F.; Lippmann-Pipke, J.; Gründig, M.; Richter, M.
Der ehemalige Kali- und Steinsalzbergbau im Raum Staßfurt (Sachsen-Anhalt) führt seit dem 19. Jahrhundert zu stellenweise erheblichen Bergschäden im Stadtgebiet, die auf Subrosion und Konvergenz untertägiger Hohlräume zurück gehen. Gebäude und Infrastruktur sind von großflächigen Absenkungen, Vernässungen und lokalen Tagesbrüchen in Mitleidenschaft gezogen worden.

Da man ähnliche Bergbaufolgeschäden in vielen Regionen des Salzbergbaus antrifft, hat sich das aus mehreren Forschungseinrichtungen, Universitäten und Unternehmen bestehende Forschungsverbundvorhaben Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks unter Federführung der Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) zum Ziel gesetzt, Ursachen, Prozesse und Auswirkungen der Bergschäden exemplarisch und allumfassend zu untersuchen.

Um ein möglichst umfassendes Bild der im Untergrund ablaufenden Prozesse und deren Ursachen und Folgen zu erhalten, sind Untersuchung der kleinräumigen Strukturen und Prozesse im Labormaßstab erforderlich. Die großräumige Abschätzung der Grundwasserdynamik im Salinar und im Deckgebirge, also der Ursachen und Folgen der Subrosion, bedarf der Charakterisierung von Wegsamkeiten und der Fluiddynamik bis in den Milli- und Mikrometerbereich, da sich die grundlegenden Prozesse auf der molekularen Ebene in der Mikroskala abspielen und somit die Dynamik in der regionalen Größenordnung bestimmen.

Wie auf der Feldskala, so wird auch auf der Laborskala die Verteilung von hydrologischen Parametern, wie z.B. Permeabilitäten, Abstandsgeschwindigkeiten und Dispersionsraten von der heterogenen Struktur des Gesteins kontrolliert, weswegen diese Parameter nicht nur im regionalen sondern auch im Labormaßstab strukturbezogen, also räumlich differenziert, erhoben werden sollten.

Daher wurde in enger Zusammenarbeit mit dem Geologischen Institut der JGU Mainz eine Methode zur direkten räumlich aufgelösten und quantitativen Prozessbeobachtung entwickelt und angewendet. Hierfür wurde die Methode der Positronen-Emissions-Tomographie (PET) eingesetzt, ein ursprünglich medizinisches, bildgebendes Verfahren. Dieses Verfahren erlaubt es, zerstörungsfrei, mit höchstmöglicher Empfindlichkeit und geeignetem Auflösungsvermögen, die Bewegung einer mit einem radioaktiven Tracerisotop (hier F-18 und I-124) markierten Wassermenge in Raum und Zeit zu beobachten, wobei die Menge des eingesetzten Radiotracers im Bereich weniger Nanogramm gehalten werden kann. Das System wird somit durch den Tracer auf geringst mögliche Weise beeinflusst und es wird ein sehr realistisches Bild des Fließverhaltens mit einer räumlichen Auflösung von 1 mm und einer zeitlichen Auflösung von 60 s erzeugt.

Bislang wird in der Literatur nur von wenigen Ansätzen berichtet, die das Ziel verfolgen, die realistischen Verhältnisse strömender Fluide in heterogen strukturierten Gesteinen dreidimensional abzubilden. Solche Strömungsmuster werden in der Regel mittels stochastischer Modelle durch Computersimulationen erzeugt. Erst ein Abgleich mit gemessenen Strömungsmustern kann zur Validierung dieser Simulationen führen, was auch erst ein valides Upscaling in die Feldskala ermöglicht.

In Kooperation mit der Bundesanstalt für Materialforschung- und prüfung Berlin (BAM) und dem Geologischen Institut der Johannes-Gutenberg Universität Mainz (JGU) werden daher die PET-Messungen zur Fluiddynamik mit Lattice-Boltzmann-Simulationen der Fließprozesse verglichen, die auf hochauflösenden computertomographischen µXCT Messungen der internen Struktur der identischen Bohrkerne beruhen.

Der Vergleich von PET-Messdaten mit Lattice-Boltzmann - Simulationsdaten bedeutet eine Skalenübertragung um etwa drei Größenordnungen (µm - mm). Daher erfolgt der Abgleich zwischen gemessenen und simulierten Daten auf statistischem Wege. Gemessene und simulierte Strömungsmuster werden mittels Variographie mit einander abgeglichen, da diese Methode skalenübergreifend die Korrelationen zwischen den Fließmustern wider gibt. Ebenso werden räumlich differenzierte Durchbruchkurven und Histogramme für den Vergleich von Messung und Simulation heran gezogen.

Diesem Ansatz liegt das Bestreben zugrunde, zu einer Erweiterung des generellen Prozessverständnisses und der Vorhersagbarkeit über das Verhalten von Fluiden in porösen und klüftigen Gesteinen beizutragen und die beobachteten Phänomene und Prozesse von der Labor- auf die Feldskala zu übertragen.

Nicht in jedem Fall war dieser Abgleich zwischen Simulation und Experiment jedoch möglich: während in klüftig-porösen Materialien gewöhnlich mit beiden Methoden räumlich stark differenzierte präferentielle Fließwege im Kluftsystem gefunden wurden, konnte in eher mikrostrukturell ausgeprägten Materialien trotz messbarer Permeabilität gelegentlich kein verbundener Porenraum aus den CT-Bildern segmentiert und somit keine Lattice-Boltzmann-Simulation durchgeführt werden. In diesem Fall zeigte die PET-Untersuchung ein diffuses Ausbreitungsverhalten des Tracers.
  • Lecture (Conference)
    Staßfurt-Verbund Abschlusstagung 2010, 18.-20.11.2010, Staßfurt, Sachsen-Anhalt

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Publ.-Id: 14692


Fluid flow in geological material: GeoPET observation in comparison with Lattice-Boltzmann simulation

Wolf, M.; Kulenkampff, J.; Lippmann-Pipke, J.; Gründig, M.; Richter, M.; Enzmann, F.
This thesis is located at the Institute of Radiochemistry, FZD Research Site Leipzig for Interdisciplinary Isotope Research, Reactive Transport Division (FWRT). The main focus of this division is the investigation of transport processes in geosystems by means of radiotracer applications. The main topic of the thesis is the visualization of transport processes in geologic material by means of the in-house development of the GeoPET-method. This work is conducted as part of the scientific joint venture: „Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks“ („Dynamic of drowned or flooded salt mines and their overburden“), coordinated by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR).

Since the late 19. century drowned salt mines cause severe mining damages in the city of Stassfurt (Saxony-Anhalt). Sink hole depressions and subsidence of the surface below the groundwater table destroyed large parts of the down town. The general causation was lack of experience with salt mines and mining in gypsum karst in the 19. century. The causation in detail why and how exactly salt rock has washed out is more complicated to identify, as streaming mechanisms at the small scale level are partly still unclear; the general fluid dynamics at small scales is partly unknown.

To reveal these processes and mechanisms the behaviour of salt brines at the millimetre scale in drilling cores of the different geological units of the salt rock and its surrounding is examined by three-dimensional visualization of the distribution of radioactive labelled water measured with PET. Mechanisms at millimetre scale control mechanisms at the kilometre scale and are of utmost importance for the principal understanding of fluid dynamics. In the laboratory you can have „a look into the rock“. In the field this is not possible this way.

Combining PET data with high resolution CT-scans of the samples (conducted by the cooperation partners JGU Mainz and BAM Berlin) allows an alignment of processes of the fluid flow and its associated hydraulic pathway structures. This matching is important for understanding and for generalized conclusion about ongoing processes and is a necessary preparatory work for computer modelling.

Lattice-Boltzmann-simulations of velocity fields and streaming patterns based on CT-data are compared with PET-data derived from the same samples. This comparison of the flow patterns is done by means of geostatistic methods that allows scale independant spatial correlation of the patterns and therefore provide scale indpendant parameters like correlation lengths that are a necessity for upscaling.

Short term objective is the improvement and validation of parameters and fluid flow concepts derived from small scale simulations. Long term objective is the improvement of upscaling of parameters and concepts to the field scale and a better understanding and prediction of mining damages and groundwater behaviour.
  • Lecture (Conference)
    Bodenphysik-Seminar, 14.10.2010, Halle, Sachsen-Anhalt

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Permalink: https://www.hzdr.de/publications/Publ-14691
Publ.-Id: 14691


Does the coordination geometry of CuII bispidine complexes influence the radiopharmacological properties?

Fähnemann, S.; Stephan, H.; Walther, M.; Steinbach, J.; Haaf, C.; Comba, P.
3,7-Diazabicyclo[3.3.1]nonane derivatives (bispidines) represent a versatile platform for the development of new copper radiopharmaceuticals.[1] An extensive research effort has shown that bispidines with additional donor substituents form very stable complexes with copper(II) (L1, logK = 16.3). The CuII complexes of these so-called 1st generation hexadentate bispidine ligands (L1-Cu) enforce a distorted octahedral geometry which is well preorganized for CuII.

Recently, the 2nd generation of bispidine derivatives has been reported (L2 – L3).[2, 3] These ligands yield very high complex stabilities with CuII (logK from 19.5 to 26.4) similar to [CuII(cyclam)]2+ (logK = 27.2). In contrast to the 1st generation bispidines they provide exclusively aliphatic nitrogen atoms in the backbone, combined with one (L2) or two (L3) rigid diazacycloheptane rings for tetra- or hexadentate coordination, leading to distorted trigonal bipyramidal or distorted trigonal prismatic coordination geometries.

Ligands L1 – L3 have been labeled with 64Cu, and their radiopharmacological data, e.g. labeling efficiency and kinetics, lipophilicity and in vitro stability will be discussed.

Literature:
[1] S. Juran, M. Walther, H. Stephan, R. Bergmann, L. Steinbach, W. Kraus, F. Emmerling, P.Comba; Bioconjugate Chem. 2009, 20, 347-59.
[2] P. Comba, C. Haaf, H. Wadephol; Inorg. Chem. 2009, 48, 6604-6614.
[3] P. Comba, C. Haaf, A. Lienke, A. Muruganantham, H. Wadepohl: Chem.-Eur. J., 2009, 41, 10880-10887.
  • Poster
    3rd EuCheMS Chemistry Congress, 29.08.-02.09.2010, Nürnberg, D

Permalink: https://www.hzdr.de/publications/Publ-14690
Publ.-Id: 14690


Octahedral rhenium cluster/glycodendrimer associates: A new tailor-made drug delivery system?

Kubeil, M.
In recent years polynuclear metal complexes have become increasingly important due to their antitumoral as well as antiviral properties. [1] Their wide variety of biochemical, chemical and physical properties gives the opportunity to create tailor-made drugs. In this perspective, the enhancement of the hydrolytic stability and in particular the improvement of the in vivo selectivity of inorganic cluster compounds represents the major burden to circumvent.

Appropriate nanocontainers may be utilized to enable the cluster compounds to be transported and released within target tissues. Of great interest is the encapsulation of potential drug molecules by non-covalent binding at the interior of dendritic structures which provide well-defined cavities. In this context, dendritic nanocontainer with maltose-modified shell [2] appears appealing to act as a host for nanometer sized anionic rhenium cluster compounds.

The inclusion and release phenomena of an octahedral rhenium cluster with six terminal hydroxo ligands [Re6S8(OH)6]4- [3] into poly(propylene amine) dendrimers (POPAM, generation 4 and 5) with dense maltose shell have been studied in detail applying different physico-chemical methods, e.g. UV/vis, time-resolved laser-induced fluorescence spectroscopy (TRLFS) and laser induced liquid bead ion desorption (LILBID) mass spectrometry.

On average, 4 – 5 cluster anions can be captured in the interior of the investigated sugar-coated dendrimers, and a slow release of cluster complexes was observed under physiological conditions.

Altogether, the studied system shows the possibility for the development of dendritic nanocarriers with specific targeting and paves the way for therapeutic applications.



[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev.1998, 98, 327-357.
[2] B. Klajnert, D. Appelhans, H. Komber, N. Morgner, S. Schwarz, S. Richter, B. Brutschy, M. Ionov, A. K. Tonkikh, M. Bryszewska, B. Voit, Chem. Eur. J. 2008, 14, 7030.
[3] K. A. Brylev, Y. V. Mironov, S. S. Yarovoi, N. G. Naumov, V. E. Fedorov, S.-J. Kim, N. Kitamura, Y. Kuwahara, K. Yamada, S. Ishizaka, Y. Sasaki, Inorg. Chem. 2007, 46, 7414-7422.
  • Lecture (Conference)
    IWTMC-II International Workshop on Transition Metal Clusters-II, 30.09.-02.10.2010, Rostock, D

Permalink: https://www.hzdr.de/publications/Publ-14689
Publ.-Id: 14689


Improved environmental resistance of Ti-alloys at elevated temperatures by a combined Al- and F-treatment

Donchev, A.; Schütze, M.; Kolitsch, A.; Yankov, R.
Titanium is widely used as a structural material because of its low specific weight, good mechanical properties and excellent corrosion resistance at low temperatures due to the formation of a passive TiO2layer. The melting point (1677°C) is very high. Usually the maximum tolerable operating temperature is lower than 600°C. Because of increased oxidation and environmental embrittlement Ti-Alloys can not be used at higher temperatures in oxidizing environments. An enrichment of Al in the surface zone of Ti-alloys leads to an improvement of the oxidation resistance by the formation of intermetallic TixAly-phases but this is not sufficient. A fluorine treatment on TiAl-alloys results in the formation of a protective alumina scale by the so called fluorine effect. Therefore, the combination of Al-enrichment in the surface zone so that a TiAl-layer is formed and an additional F-treatment gives good results. The alumina scale is very protective against environmental attack and also prevents oxygen inward diffusion which causes embrittlement. In this paper the results of isothermal and thermocyclic oxidation tests at 600°C of several Ti-alloys (-Ti, Ti3Al, etc.) are presented without any treatment, with single Al-treatment, pure F-treatment and the combination of both. Aluminium was either enriched by a powder pack process or by magnetron sputtering. Fluorine was applied by several ways e.g. by a liquid phase process. Post experimental investigations like SEM revealed the formation of thin oxide layers on samples with the combined Al + F-treatment. Hardness measurements showed that no embrittlement was observed on the treated samples while untreated specimens showed increased hardness values in the oxygen enriched zone.
  • Lecture (Conference)
    Materials Science & Technology 2010 Conference and Exhibition - combined with the ACerS 112th Annual Meeting (MS&T 2010), 17.-21.10.2010, Houston, USA

Permalink: https://www.hzdr.de/publications/Publ-14688
Publ.-Id: 14688


Protection of TiAl-components against high temperature oxidation with fluorine

Donchev, A.; Schütze, M.; Kolitsch, A.; Yankov, R.
Titanium aluminides are very promising light weight materials for several high temperature applications e.g. in aero or automotive engines but due to their insufficient oxidation resistance at temperatures above roughly 800°C they can not be used for longer times. The oxidation behaviour of TiAl-alloys can be improved significantly by microalloying of small amounts of fluorine into the subsurface zone. The use of TiAl-components after fluorine treatment is possible up to temperatures above 1000°C in oxidizing atmospheres due to the formation of a thin protective alumina layer. One possibility to apply fluorine to the surface of complex TiAl-components is the PI³-technique (plasma immersion ion implantation). The use of an Ar/CH2F2-plasma for the F-PI³ into small coupons leads to a positive effect which is as good as the beamline implantation of elemental fluorine gas into samples of the same size. Other treatments are using liquid or gaseous fluorine containing compounds which react with the surface of the specimens. The oxidation kinetics of F-treated TiAl-alloys will be discussed in the paper. Several more complex TiAl-samples and turbine blades as examples for real TiAl-components have been treated. Their oxidation behaviour will be shown. Post exposure investigations like SEM reveal a thin protective alumina scale on the surface of the implanted samples in contrast to a thick mixed scale (TiN/TiO2/Al2O3) growing on untreated samples during high temperature exposure in air.
  • Lecture (Conference)
    Materials Science & Technology 2010 Conference and Exhibition - combined with the ACerS 112th Annual Meeting (MS&T 2010), 17.-21.10.2010, Houston, USA

Permalink: https://www.hzdr.de/publications/Publ-14687
Publ.-Id: 14687


Suppression of oxygen-induced embrittlement in Ti by plasma immersion ion implantation (PIII)-based processing

Yankov, R. A.; Kolitsch, A.; Munnik, F.; von Borany, J.
Titanium has a large strength-to-weight ratio and good corrosion resistance at moderate temperatures, which make it an important structural material in a number of advanced technical applications. A major problem with the use of Ti is its high affinity to oxygen giving rise to massive oxygen in-diffusion at temperatures of about 550° to 600°C. The presence of large amounts of oxygen renders the material brittle and deteriorates its mechanical properties. In this work, we describe an effective way of overcoming the oxygen-induced embrittlement problem by forming a surface barrier to the diffusion of oxygen. Surface processing has involved two steps, namely enrichment of the Ti near-surface region with Al, and introduction of fluorine. For the Al enrichment, a novel hybrid system has been developed to implant Al into Ti. The apparatus consists basically of a PIII chamber configured with two magnetrons having an Al target each, and facing the RF antenna. The magnetrons are synchronized with the bias applied to the sample holder in such a way that the accelerating high-voltage pulse is triggered with a certain delay, i.e. during the time when the Al plasma generated by the magnetrons is most dense, thereby minimizing deposition. Alternative aluminization techniques have involved either magnetron sputtering of Al onto Ti followed by a thermal drive-in step or pack processes. Fluorine has been subsequently introduced by PIII employing a mixture of CH2F2 and Ar as the precursor gas. A variety of analytical techniques such as elastic recoil detection analysis (ERDA), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and x-ray diffraction (XRD) have been used for characterization. Optimized PIII-based processing has been found to produce a continuous, adherent alumina scale on the Ti surface. Thus, the resulting material is inherently resistant to oxygen absorption and is not embritteled upon extended exposure to oxygen-containing environments at elevated temperatures up to about 600° C.
  • Poster
    12th International Conference on Plasma Surface Engineering - PSE 2010, 13.-17.09.2010, Garmisch-Partenkirchen, Germany

Permalink: https://www.hzdr.de/publications/Publ-14686
Publ.-Id: 14686


Improvement of the oxidation behaviour of complex shaped TiAl-alloys by plasma immersion ion implantation with fluorine

Kolitsch, A.; Yankov, R.; Donchev, A.
Titanium aluminides are of great interest for several structural high temperature applications because of their low specific weight (about 4 g/cm3) and their excellent high temperature strength. They could replace the much heavier high temperature steels or Ni-based superalloys (up to 9 g/cm3) which are usually in service. The implementation of this new group of intermetallic alloys in e.g. the aerospace or automotive industry is therefore due to economic and ecologic reasons. The use of TiAl-based alloys is still limited to a temperature of about 750 °C because of their poor oxidation resistance despite of their good mechanical properties which would allow the use at higher temperatures. The oxidation resistance can be improved significantly by small amounts of halogens such as fluorine, chlorine, bromine and iodine (so called halogen effect).
A defined dose of these halogens has to be provided at the metal/oxide interface of the component. The halogens promote the selective formation of gaseous Al-halides at temperatures above 700 °C which are oxidised to Al2O3 during their outward diffusion through the naturally grown oxide scale. So finally a protective alumina scale is formed which is stable for long times even under thermocyclic exposure and wet atmospheres. In this presentation the results of isothermal and thermocyclic high temperature oxidation tests of technical TiAl-alloys with and without fluorine ion implantation are shown.
  • Poster
    18th International Conference on Ion Implantation Technology, 06.-11.06.2010, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-14685
Publ.-Id: 14685


Formation of an alumina-containing scale for the surface protection of TiAl alloys and Ti against environmental degradation at elevated temperatures

Yankov, R. A.; Kolitsch, A.; Munnik, F.; von Borany, J.
Ti and TiAl alloys are lightweight materials that hold great promise for advanced aerospace, automotive and power generation applications. They are, however, limited in applicability by their poor oxidation resistance above 600°C. We have developed a process for enhancing the high-temperature oxidation resistance of these materials. For TiAl, the process involves a single step, i.e. plasma immersion implantation (PIII) of fluorine relying on the so-called "halogen effect". Optimum conditions have been established under which the alloys acquire a stable, adherent and highly protective alumina scale upon subsequent high-temperature oxidation in air. The extent of oxidation protection has been evaluated by testing F-implanted TiAl samples at temperatures up to 1050°C. Results from characterization by elastic recoil detection, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis have proven the possibility of forming a protective alumina scale on both laboratory coupons and components such as turbine blades and turbochargers. In the case of Ti, surface processing involves two steps, i.e. Al enrichment of the Ti near-surface, and introduction of F by PIII. The Ti samples so modified have shown marked environmental stability at temperatures up to 700°C.
  • Poster
    CIMTEC 2010 - 12th International Conference on Modern Materials and Technologies, 12th International Ceramic Congress, 06.-11.06.2010, Montecatini Terme, Italy

Permalink: https://www.hzdr.de/publications/Publ-14684
Publ.-Id: 14684


Enhanced resistance of Ti-alloys against environmental attack by a combined Al- and F-treatment

Donchev, A.; Schütze, M.; Kolitsch, A.; Yankov, R.
Titanium alloys cannot be used at elevated temperatures above approximately 500°C because of their limited environmental stability. Several ways have been investigated so far to improve the environmental stability of Ti-alloys e.g. coatings but these attempts in a majority of cases have not been really successful. A new way to improve the performance of these alloys is the combination of Al-enrichment in the surface zone plus additional fluorine treatment. The Al-enrichment leads to the formation of intermetallic phases. These phases improve the oxidation resistance of Ti-alloys but not to a sufficient extent. An additional fluorine treatment on top of the Al-enriched surface leads to the formation of a stable alumina scale due to the fluorine effect. In this paper results from oxidation and other tests performed on Ti-samples without any treatment, with single Al- or F-treatment and with a combination of both are presented and the results are discussed.
  • Lecture (Conference)
    TMS 2010 (The Minerals, Metals and Materials Society), 139th Annual Meeting & Exhibition, 14.-18.02.2010, Seattle, USA

Permalink: https://www.hzdr.de/publications/Publ-14683
Publ.-Id: 14683


Comparison of fluorination treatments to improve the high temperature oxidation resistance of TiAl alloys in SO2 containing environments

Masset, P. J.; Yankov, R.; Kolitsch, A.; Schütze, M.
Surfaces of titanium aluminides were treated with fluorine either physically by plasma immersion ion implantation (PIII) or chemically using a F-based polymer. Under optimum conditions of fluorination, both treatments were shown to improve the oxidation resistance of the alloys even in aggressive environments containing sulfur dioxide (0.1 vol. %). No sulfur was detected in the oxide scale although thermodynamic calculations predict the formation of sulfides. The inward diffusion of oxygen and nitrogen was found to be reduced in the presence of SiO2.

Permalink: https://www.hzdr.de/publications/Publ-14682
Publ.-Id: 14682


Surface Morphology of Heterogeneous Nanocrystalline Rutile/Amorphous Anatase TiO2 Films Grown by Reactive Pulsed Magnetron Sputtering

Gago, R.; Vinnichenko, M.; Redondo-Cubero, A.; Czigany, Z.; Vazquez, L.
Titaniumdioxide filmswere grown on unheated substrates bymid-frequency (100 kHz) reactive pulsed magnetron sputtering at different O2 partial pressures in an Ar/O2 atmosphere. X-ray diffraction and absorption measurements reveal a transition from amorphous anatase to nanocrystalline rutile with [O2], with a mixture of both phases at intermediate values. Atomic forcemicroscopy shows that the promotion of rutile is accompanied by surface roughening due to the apparition of hollow structures (holes) on the surface, in contrast with the extremely smooth morphology of amorphous anatase films. The number and size of holes increase with [O2] and growth time in such a way that they eventually coalesce and percolate to lead to a rough surface for those growth conditions for which a rutile rich filmis obtained. Transmission electron microscopy analysis shows the growth evolution of a heterogeneous phase mixture and provides unambiguous correlation between the hole (smooth) morphology and the underlying rutile (anatase) phase. Therefore, the surface morphology results fromthe slower local growth rate of nanocrystalline rutile compared to that of the surrounding amorphous anatase flat regions as well as from the fast (slow) lateral (vertical) growth rate of the rutile domains.
Keywords: Amorphous oxides, TiO2, magnetron, pulsed discharges, thin films

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Permalink: https://www.hzdr.de/publications/Publ-14681
Publ.-Id: 14681


Tumour bed irradiation of human tumour xenografts in a nude rat model using a common X-ray tube

Tokalov, S.; Enghardt, W.; Abolmaali, N.
Studies that investigate the radiation of human tumour xenografts require an appropriate radiation source and highly standardized conditions during radiation. This work reports on the design of a standardized irradiation device using a commercially available X-ray tube with a custom constructed lead collimator with two circular apertures and an animal bed plate, permitting synchronous irradiation of two animals. Dosimetry and the corresponding methodology for radiotherapy of human non-small cell lung cancer xenograft tumours transplanted to and growing subcutaneously on the right lower limb in a nude rat model were investigated. Procedures and results described herein prove the feasibility of use of the device, which is applicable for any investigation involving irradiation of non-tumorous and tumorous lesions in small animals.

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Permalink: https://www.hzdr.de/publications/Publ-14680
Publ.-Id: 14680


Improvement of radiation-mediated immunosuppression of human NSCLC tumour xenografts in a nude rat model

Tokalov, S.; Enghardt, W.; Abolmaali, N.
Human tumour xenografts in a nude rat model have consistently been used as an essential part of preclinical studies for anticancer drugs activity in human. Commonly, these animals receive whole body irradiation to assure immunosuppression. But whole body dose delivery might be inhomogeneous and the resulting incomplete bone marrow depletion may modify tumour behaviour. To improve irradiation-mediated immunosuppression of human non-small cell lung cancer (NSCLC) xenografts in a nude rat model irradiation (2 + 2 Gy) from opposite sides of animals has been performed using a conventional X-ray tube. The described modification of whole body irradiation improves growth properties of human NSCLC xenografts in a nude rat model. The design of the whole body irradiation mediated immunosuppression described here for NSCLC xenografts may be useful for research applications involving other types of human tumours.

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Permalink: https://www.hzdr.de/publications/Publ-14679
Publ.-Id: 14679


Advanced bio-composite materials for water treatment

Raff, J.; Pollmann, K.
Bacteria developed during evolution highly effective mechanisms and structures to survive at the most forbidding, uninviting places on Earth. One example is the binding of metalloids, heavy metals and actinides by cell surface proteins of uranium mining waste pile isolates. The so called surface layer (S-layer) proteins avoid the uptake and any sustainable damage of the cell by toxic and/or radioactive elements. The proteins possess additionally self-assembling properties and form symmetric lattices. These properties altogether qualifies the protein for nano-technological purposes and allow the production of advanced bio-composite materials such as metal filters, (photo)catalysts, functionalized membranes or biosensors for the treatment of water.
Keywords: S-layer, photocatalysts, water treatment
  • Poster
    POLEKO 2010, Internationale Fachausstellung für Umwelt, Energie, Ökologie, 23.-26.11.2010, Posen, Polen

Permalink: https://www.hzdr.de/publications/Publ-14678
Publ.-Id: 14678


Untersuchungen zur U(VI)-Komplexierung durch Milchsäure sowie zur U(VI)-Sorption an Opalinuston in Abwesenheit und Gegenwart von organischen Modellliganden in Abhängigkeit von der Temperatur

Joseph, C.; Steudtner, R.; Schmeide, K.
Die U(VI)-Komplexierung durch Milchsäure in Abhängigkeit von der Temperatur (7-65°C) wurde mittels UV/VIS-Spektroskopie und TRLFS untersucht. Dabei konnten zwei U(VI)-Lactat-Komplexe, UO2Lac+ und UO2Lac2, identifiziert werden. Die entsprechende Enthalpie und Entropie der U(VI)-Komplexierung wurde bestimmt.
Die U(VI)-Sorption an Opalinuston (OPA) in Abhängigkeit von Modellliganden und der Temperatur (25-60°C) wurde untersucht. Dabei beeinflussten die Modellliganden die U(VI)-Sorption an OPA in folgender Reihenfolge: Citronensäure > Weinsäure > Milchsäure ≈ Essigsäure > Ameisensäure. Die U(VI)-Sorption nahm mit steigender Ligandenkonzentration ab, nahm aber mit steigender Temperatur zu. Bei 60°C wurde ein Sprung im Kd-Wert des Urans verzeichnet. Milchsäure hatte dabei keinen signifikanten Einfluss auf die Enthalpie und Entropie der U(VI)-Sorption an OPA in Abhängigkeit von der Temperatur.
HTO-Diffusionsversuche mit OPA bei 25°C und 60°C wurden durchgeführt um die Diffusionsparameter (effektiver Diffusionskoeffizient, Porosität) der Tonproben zu bestimmen. Die experimentellen Werte bestätigten die Literaturdaten.
Keywords: uranium(VI), complexation, TRLFS, UV/VIS, lactate, citric acid, sorption, Opalinus Clay, temperature-dependent, diffusion, HTO
  • Lecture (others)
    9. Workshop des Verbundprojekts "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 05.-06.10.2010, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14677
Publ.-Id: 14677


Design, Synthesis and Preliminary in vitro and in vivo Pharmacological Evaluation of 2-{4-[4-(2,5-disubstituted thiazolyl)phenylethyl] piperazin-1-yl}-1,8-naphthyridine-3- carbonitriles as Atypical Antipsychotic Agents

Chandra Sekhar, K. V. G.; Rao, V. S.; Deuther-Conrad, W.; Reddy, A. S.; Brust, P.; Kumara, M. M. K.
A series of 2-{4-[4-(2,5-disubstituted thiazolyl)phenylethyl] piperazin-1-yl}-1,8-naphthyridine-3-carbonitriles were synthesized in an effort to prepare novel atypical antipsychotic agents. The compounds were synthesized by either microwave irradiation technique or by conventional synthesis and were characterized by spectral data (IR, 1H NMR, and MS) and the purity was ascertained by microanalysis. The D2 and 5-HT2A affinity of the synthesized compounds was screened in vitro by radioligand displacement assays on membrane homogenates isolated from rat striatum and rat cortex, respectively. Furthermore, all the synthesized compounds were screened for their in vivo pharmacological activity in Swiss albino mice. The D2 antagonism studies were performed using climbing mouse assay model and 5-HT2A antagonism studies were performed using quipazine induced head twitches in mice. It was observed that none of the new chemical entities exhibited catalepsy and 10f is the most active among the synthesized compounds with 5-HT2A/D2 ratio of 1.1286 while the standard drug risperidone exhibited 5-HT2A/ D2 ratio of 1.0989
Keywords: schizophrenia, atypical antipsychotics, D2 antagonists, 5-HT2A antagonists

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Permalink: https://www.hzdr.de/publications/Publ-14675
Publ.-Id: 14675


A prototype coordinate detector based on granulated thin-walled drift tubes

Bazylev, S. N.; Davkov, K. I.; Gregor, I.; Haas, D.; Mouraviev, S. V.; Myalkovskiy, V. V.; Naumann, L.; Peshekhonov, V. D.; Rembser, C.; Rufanov, I. A.; Russakovich, N. A.; Senger, P.; Shutov, A. V.; Slepnev, I. V.; Smirnov, S. Y.; Tikhomirov, V. O.; Zhukov, I. A.
A prototype detector based on thin-walled segmented tubes has been developed and its parameters have been studied. The detector contains 360 registration channels with a straw diameter of 4mm. The prototype granularity is 4 cm2 and the length of insensitive region due to straw internal elements is less than 5% of its full sensitive area. Deterioration of the spatial resolution near these elements is observed for 1.0% of the detector sensitive area. The time and spatial parameters of the detector do not differ from those of conventional tracking detectors based on drift tubes.
Keywords: Coordinate detector Granulated thin-walled drift tube Straw Spatial resolution

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Permalink: https://www.hzdr.de/publications/Publ-14674
Publ.-Id: 14674


Exploring uranium chemistry with computational chemistry

Tsushima, S.
there is no abstract for this talk
  • Lecture (Conference)
    User's meeting of Zentrum für Informationsdienste und Hochleistungsrechnen (ZIH), TU Dresden, 06.-07.12.2010, TU Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-14673
Publ.-Id: 14673


Ni-Ti Surface Modification by Plasma Immersion Ion Implantation

Martins, R. M. S.; Barradas, N.; Alves, E.; Henke, D.; Reuther, H.; Carmezim, M. J.; Fernandes, T. M. S. J. C. S.
The plasma immersion ion implantation (PIII) technique was used to modify and improve the surface of a Ni-Ti alloy (» 50.2 at.% Ni) for biomedical applications. The main goal has been the formation of a Ni-depleted surface, which should serve as a barrier to out-diffusion of Ni ions from the bulk material. Ion implantation of oxygen was carried out. The depth profiles of the elemental distribution in the alloy surface region, obtained by Auger electron spectroscopy (AES), confirm the formation of a Ti-rich oxide layer. The working plan also comprised ion implantation of nitrogen. In this case, the formation of titanium oxynitride (TiNxOy) was observed. The AES depth profiles clearly show a Ni-depleted fraction for experiments performed with 40 keV.
Keywords: plasma immersion ion implantation, PIII, ion implantation, Ni-Ti
  • Poster
    MM & FGM 2010 - 11th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials, 26.-29.09.2010, Guimarães, Portugal

Permalink: https://www.hzdr.de/publications/Publ-14672
Publ.-Id: 14672


Medical Imaging Experience from the Past 10 Years and State-of-the-Art

Enghardt, W.
no abstract available
  • Lecture (Conference)
    ENVISION General Meeting Stockholm, 05.09.2010, Stockholm, Schweden

Permalink: https://www.hzdr.de/publications/Publ-14671
Publ.-Id: 14671


Neue Entwicklungen in der medizinischen Strahlenphysik

Enghardt, W.
no abstract available
  • Invited lecture (Conferences)
    43. Sitzung des Arbeitskreises Strahlenbiologie/Strahlenwirkung Dresden, 21.-22.06.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14670
Publ.-Id: 14670


Laser-Radioonkologie: Auf dem Weg vom Konzept zur Klinik

Enghardt, W.
no abstract available
  • Invited lecture (Conferences)
    Symposium anlässlich der Emeritierung von Prof. Dr. Thomas Herrmann, 19.02.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14669
Publ.-Id: 14669


Prospects in Medical Imaging - Summary Workshop

Enghardt, W.
no abstract available
  • Invited lecture (Conferences)
    „Physics for Health in Europe“, 02.-04.02.2010, Geneva, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-14668
Publ.-Id: 14668


Wissensvermittlung im Studiengang „Medical Radiation Sciences“ an der Medizinischen Fakultät der TU Dresden Sitzung des Fachausschusses Strahlenschutz des Länderausschusses für Atomkernenergie

Enghardt, W.
no abstract available
  • Invited lecture (Conferences)
    Sitzung des Fachausschusses Strahlenschutz des Länderausschusses für Atomkernenergie, 18.02.2010, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14667
Publ.-Id: 14667


Runtime Experience and Impurity Investigations at the ELBE Cryogenic Plant

Schneider, C.; Michel, P.; Haberstroh, C.
The superconducting linear accelerator ELBE at the Forschungszentrum Dresden/Rossendorf has two superconducting accelerator modules and a superconducting photo injector (SRF-Gun). They are operated by a cryogenic Helium plant with a cooling power of 200 W at 1.8 K. Since the commissioning of the plant in 1999 minor and major impurity problems have influenced the operation stability of the plant. The presentation will give an overview of the ELBE cryogenic system and will focus on the different sources of plant contamination and their effects on the plant operation, which have been found during the nearly 10 years of plant lifetime. Especially the contamination with oil brake up components as well as air and water from different sources have limited the run periods of the plant and effected special service and maintenance procedures.
Keywords: superconducting linear accelerator, cryogenetic
  • Contribution to proceedings
    The first International Particle Accelerator Conference, IPAC’10, 23.-28.05.2010, Kyoto, Japan
    Proceedings of IPAC'10, 3828-3830
  • Poster
    The first International Particle Accelerator Conference, IPAC’10, 23.-28.05.2010, Kyoto, Japan

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Permalink: https://www.hzdr.de/publications/Publ-14666
Publ.-Id: 14666


Untersuchungen zur Anwendung der Elektronenstrahl-Röntgen-Tomographie für die Kleintierbildgebung

Loitsch, S.
Die ultraschnelle Röntgentomographie wird am FZD vorrangig für die Untersuchung von Zweiphasenströmungen eingesetzt. Potentielle Anwendungsgebiete sind aber auch auf dem medizinischen Sektor zu erwarten. Daher soll die Möglichkeit des Einsatzes der ultraschnellen Röntgentomographie für die Kleintierbildgebung untersucht werden. In dieser Diplomarbeit wurden statische und dynamische Labormodelle entwickelt, mit deren Hilfe die Abbildungseigenschaften für die Kleintierdiagnostik evaluiert werden können.
Keywords: ultrafast imaging, X-ray computed tomography, small animals
  • Diploma thesis
    Fachhochschule Lübeck, 2010
    63 Seiten

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Publ.-Id: 14665


Filtration material inspired by microorganisms

Kutschke, S.; Pollmann, K.; Raff, J.; Matys, S.
Detoxification strategy of bacteria, living in uranium mining waste piles, is one part of radio-ecological investigation at the Institute of Radiochemistry of the Forschungszentrum Dresden-Rossendorf. On that account several isolates were subsequently analyzed regarding their growth in presence of different heavy metals and their heavy metal binding properties, particularly using uranium. Some isolates show a high and selective binding for uranium, cadmium, lead, and a few other heavy metals. Interestingly, the heavy metals were immobilized on the cell surface, preventing any sustainable damage of the cell. Responsible for the binding of heavy metals outside the cell is a proteinaceous cell envelope, a so-called surface layer (S-layer).
Using these heavy metal binding properties of bacterial cells and S-layer different filter materials were developed. These include the production of biofilm based materials and the protein immobilization on conventional carriers. Thereby, a different binding behaviour between whole cells and their corresponding S-Layers could be observed. Moreover the S-layer based filter materials bind also some precious metals. So a metal selective filter material for the removal of heavy metals and precious metals from aqueous solutions is developing.
Keywords: Proteinous bacterial surface layer (S-layer) Metal binding capacities of S-layer Application potential
  • Invited lecture (Conferences)
    Synthetic Fibre Talks- Membranes and Filters, 29.-30.04.2010, Aachen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14663
Publ.-Id: 14663


Sorption of thallium(I) onto geological materials: Influence of pH and humic matter

Liu, J.; Lippold, H.; Wang, J.; Lippmann-Pipke, J.; Chen, Y.
The sorption behaviour of the severely toxic heavy metal thallium (Tl) as a monovalent cation onto three representative materials (goethite, pyrolusite and a natural sediment sampled from a field site) was examined as a function of pH in the absence and presence of two natural humic acids (HAs), using 204Tl(I) as a radiotracer. In order to obtain a basic understanding of trends in the pH dependence of Tl(I) sorption with and without HA, sorption of HAs and humate complexation of Tl(I) as a function of pH were investigated as well. In spite of the low complexation between Tl(I) and HAs, the presence of HAs results in obvious alterations of Tl(I) sorption onto pyrolusite and sediment. An influence on Tl(I) sorption onto goethite was not observed. Predictions of Kd (distribution coefficient) for Tl(I) on goethite in the presence of HAs, based on a linear additive model, agree well with the experimental data, while a notable disagreement occurs for the pyrolusite and sediment systems. Accordingly, it is suggested that HAs and goethite may act as a non-interacting sorbent mixture under the given conditions, but more complex interactions may take place between the HAs and the mineral phases of pyrolusite or sediment.
Keywords: goethite; pyrolusite; humic acid; modelling

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Publ.-Id: 14661


Cold quark stars from hot lattice QCD: a comparison

Schulze, R.; Kämpfer, B.
Based on a quasiparticle model for \beta stable and electrically neutral deconfined matter we address the possibility of pure quark stars. The model is adjusted to recent hot lattice QCD results for 2+1 flavors with almost physical quark masses. Using stability and binding arguments general statements can be made concerning the existence of such compact stellar objects.
  • Lecture (Conference)
    TORIC 2010, 26.-30.09.2010, Villasimius/Sardinia, Italy

Permalink: https://www.hzdr.de/publications/Publ-14660
Publ.-Id: 14660


Superconductivity in Group IV Semiconductors

Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Posselt, M.; Skorupa, W.; Helm, M.; Gobsch, G.
es hat kein Abstract vorgelegen
  • Lecture (Conference)
    Punktdefekttreffen, 07.-08.10.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14659
Publ.-Id: 14659


Spin manipulation in Co-doped ZnO

Schmidt, H.
The magnetoresistance of n-type conducting, paramagnetic Co-doped ZnO films prepared by pulsed laser deposition on sapphire substrates has been studied experimentally and theoretically. Positive magnetoresistance (MR) of 124% has been observed in the film with the lowest electron concentration, while only a negative MR of −1.9% was observed in the film with a large electron concentration at 5 K. The positive MR is attributed to the quantum correction on the conductivity due to the s-d exchange interaction induced spin splitting of the conduction band. The negative MR is attributed to the magnetic field suppressed weak localization. Voltage control of the electron concentration in Schottky diodes revealed a drastic change of the magnetoresistance and demonstrated the electrically controllable magnetotransport behavior in Co-doped ZnO. The magnetically controllable spin polarization in Co-doped ZnO has been demonstrated at 5 K in magnetic tunnel junctions with Co-doped ZnO as a bottom electrode and Co as a top electrode. There spin-polarized electrons were injected from Co-doped ZnO to a crystallized Al2O3 layer and tunnelled through an amorphous Al2O3 barrier. Our studies demonstrate the spin polarization and manipulation in Co-doped ZnO.
Keywords: ZnO, spin polarization, spin-polarized transport
  • Invited lecture (Conferences)
    12th International Ceramics Congress, 06.-11.06.2010, Montecatini Terme, Italy

Permalink: https://www.hzdr.de/publications/Publ-14658
Publ.-Id: 14658


Lung tumour motion during treatment: Should we match on bone or on tumour?

Hoinkis, C.; Richter, C.; Enghardt, W.; Zips, D.; Baumann, M.
During the session titled "The use of PET-CT for lung cancer" several topics will be addressed, such as the technical background of PET-CT and an overview of the possibilities offered by PET imaging in lung cancer. The aim of all PET imaging in treatment planning for tumours is an improved delineation of the Gross Tumour Volume (GTV). Knowing exactly the position and extent of the vital tumour should increase local control and lead to longer survival of patients. As long as the target is immobile as is the case in the brain fusion of the PET information into the planning CT seems to be effortless. But problems arise when PET imaging is to be used for moving targets such as in lung. Therefore, the issue to be discussed in this presentation is "Should we match on bone or on tumour?". Necessity of motion comprehension during PET-CT imaging: In PET-CT imaging two different motion-related effects have to be considered:
(1) the direct effect of motion on the CT and PET modalities separately, and
(2) the effect of improper attenuation correction caused by a mismatch in the temporal resolutions of the two data sets.Examples of direct effects are artefacts in the region between the lung and liver in 3D-CT data and motion-induced smearing of the activity concentration in 3D-PET data. These artefacts are unavoidable in 3D imaging but can be overcome with the introduction of 4D imaging (4D-CT and 4D-PET). The second effect (i.e. smearing) has to be considered in both 3D- and 4D-imaging. In 3D-imaging the 3D-CT artefacts described above can propagate into the PET data set due to attenuation correction. One example given by Beyer et al. shows 3D PET-CT data that appears to show soft tissue in the lung, but which in fact is part of the moving liver (Eur J Nucl Med Mol Imaging 2003). Additionally, the different temporal resolution of 3D-PET and 3D-CT can generate artefacts in attenuation corrected data sets although both 3D-CT and uncorrected 3D-PET are free of artefacts. One impressive example of this phenomenon was shown by Osman et al. (J Nucl Med 2003), where liver metastases appeared in the lung region. In 4D-imaging, artefacts due to improper attenuation correction can be avoided if the different datasets of the 4D-PET are corrected with corresponding datasets of the 4D-CT, as has been demonstrated by Pnisch et al. (Med Phys 2008).
Possibilities for motion compensation during treatment: Several technical approaches have been introduced into clinical practice to compensate for motion during radiotherapy.
Two questions have to be addressed: a) How can the motion be turned into a signal and b) how can this signal be used to compensate the motion? Answering question a), helpful techniques which can be mentioned include spirometry, pressure based systems or optical systems detecting the motion of points on the thorax or of the whole body surface. In all these techniques, the motion leads to a signal that represents more or less precisely the motion of the patient. However, it is not proven that any signal also exactly follows the motion of the tumour. Answering question b), two approaches can be mentioned: "Gating" and "Tracking". Gating uses the motion signal to trigger the linear accelerator according to a defined "gate", i.e. to turn the beam on and off in synchronization with the breathing motion. Tracking is a method in which the motion of the target is followed (tracked) either by motion of the leaves in the MLC or by motion of the table. Verification of motion in the chain from planning to treatment: 4D treatment planning including 4D-PET/4D-CT and breathing-synchronized radiotherapy for lung cancer patients need a carefully considered concept of verification.
In contrast to conventional verification procedures at the linear accelerator, where the position of the patient is verified only by bony anatomy (brain), target motion adapted methods require appropriate additional imaging in the treatment room. Either radioopaque markers or kV-CT images are necessary. For organs with mainly interfractional motion such as the prostate, correct positioning of the target before the start of the fraction is essential. The treatment of intrafractional moving targets imposes more complexity. Besides verification of the baseline, the amplitude of the motion is a second point to be considered. The most important in the verification of a breathing synchronized radiotherapy is the comparison with the 4D treatment planning dataset. The basic principle is the use of the identical motion signal both for 4D imaging and for the 4D treatment. Only then a possible shift between real tumour motion and visualized tumour motion can be neglected.
Conclusions: Should we match on bone or on tumour? The short answer should be ON TUMOUR. But the longer answer is, BUT NOT FOR EVERY PATIENT. The challenge is the finding of clinical values used as guidance as to which patients will benefit from the high workload of 4D treatment planning and delivery.
  • Invited lecture (Conferences)
    ESTR0 29, 12.-16.09.2010, Barcelona, Espana
  • Abstract in refereed journal
    Radiotherapy and Oncology 96(2010)Suppl. 1, 64-65

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Permalink: https://www.hzdr.de/publications/Publ-14657
Publ.-Id: 14657


Suppression of temperature fluctuations by rotating magnetic field in a large scale Rayleigh-Benard cell

Grants, I.; Gerbeth, G.
Temperature fluctuations are observed experimentally in a cylinder of liquid mercury heated from below and cooled from above under action of a rotating magnetic field (RMF). The Grashof number (Gr) exceeds that of earlier studies by a factor of 10 at least. The setup models a proposed modification of the Czochralski crystal growth process where crucible rotation is replaced by RMF. It is known that the RMF characterized by the magnetic Taylor number Ta=15Gr0.8 suppresses buoyant temperature fluctuations in a cylinder cooled from above [1]. To achieve a comparable effect by a mechanical rotation of the crucible, a considerably higher rotation rate is required and the difference grows with Gr. The effect has been demonstrated up to Gr~5x107 that corresponds to a medium size gallium arsenide liquid encapsulated Czochralski process. Does the “0.8” scaling keep as Gr is increased? This is the central question of the study. One of the possible explanations of the phenomenon is a hypothetical stabilizing action of the core meridional flow. It is known that the angular velocity scaling Omega~Ta2/3 experiences a change at Ta~2x107 (that is able to stabilize the Gr~5x107 configuration). Besides, it is known that the product of mean radial velocity Vr and mean angular velocity Omega equals the magnetic force (Ta~V, Omega). Thus, if the meridional flow indeed plays a major role, then there should be a change of the Tacr(Gr) scaling above Gr~5x107. The experiment will allow Gr in the range [5x107 : 5x108]. It is prepared and scheduled for April 2010
  • Lecture (Conference)
    Modelling for Material Processing, 16.-17.09.2010, Riga, Lettland
  • Contribution to proceedings
    Modelling for Material Processing, 16.-17.09.2010, Riga, Lettland
    Suppression of temperature fluctuations by rotating magnetic field in a large scale Rayleigh-Benard cell, pp. 293-298

Permalink: https://www.hzdr.de/publications/Publ-14656
Publ.-Id: 14656


Development and assessment of structural materials and heavy liquid metal technologies for transmutation systems (DEMETRA): highlights on major results

Fazio, C.; van den Bosch, J.; Martin Muñoz, F. J.; Henry, J.; Roelofs, F.; Turroni, P.; Mansani, L.; Weisenburger, A.; Gorse, D.; Abella, J.; Brissonneau, L.; Dai, Y.; Magielsen, L.; Neuhausen, J.; Vladimirov, P.; Class, A.; Jeanmart, H.; Ciampichetti, A.; Gerbeth, G.; Wetzel, T.; Karbojian, A.; Litfin, K.; Tarantino, M.; Zanini, L.
The DEMETRA domain of the EUROTRANS project provides a wealth of experimental and theoretical results within key technological areas related to the Heavy Liquid Metal (HLM) Technology. HLMs as Pb and Lead-Bismuth Eutectic (LBE) are the reference coolant and spallation materials choices for the ADS facilities studied within the EUROTRANS project.
For these coolants the key items that have been addressed within DEMETRA are:
Coolant quality control in terms of oxygen and impurities control;
Materials compatibility in terms of corrosion, mechanical and irradiation resistance;
Thermal-hydraulics studies related to heat transfer in turbulent conditions through dedicated experiments on a single pin, a fuel bundle and integrated component tests;
Safety related studies through experimental and simulation studies on HLM/water interaction;
Support to component design and testing, where in particular substantial support has been given to the development of the windowless-neutron spallation target and the assessment of the window spallation target behaviour through the post test analysis of MEGAPIE;
Measurement and operational techniques development;

The technical work programme of DEMETRA is herein summarised and some major experimental results are discussed.
  • Lecture (Conference)
    Technology and components of accelerator-driven systems, 15.-17.03.2010, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-14655
Publ.-Id: 14655


Einfluss der Pulslänge bei hohen Pulsdosen auf die Sättigungskorrektur von Ionisationskammern

Karsch, L.; Richter, C.; Pawelke, J.
no abstract available
Keywords: hohe Pulsdosen, Ionisationskammern
  • Lecture (Conference)
    41. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 29.09.-02.10.2010, Freiburg, Deutschland
  • Contribution to proceedings
    41. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 29.09.-02.10.2010, Freiburg, Deutschland

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Publ.-Id: 14654


Strömungsinstabilitäten bei der Kristallzüchtung im TMF

Gerbeth, G.
Es wird eine übersicht gegeben zu Strömungen und deren Stabilität in magnetischen Wanderfeldern. Die Sensitivität der TMF-Strömung gegenüber geringen Achsenverschiebungen zwischen TMF und Schmelztiegel ist sehr hoch und sollte in der Praxis großen Einfluss auf die tatsächlichen Strömungen in Kristallzüchtungsprozessen haben.
  • Lecture (Conference)
    Magnetfelder in der Kristallzüchtung, 09.-10.09.2010, Potsdam, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14653
Publ.-Id: 14653


Elektromagnetische Strömungskontrolle lokaler Temperaturgradienten in einem Modell des Czochralski-Prozesses

Cramer, A.; Röder, M.; Pal, J.; Gerbeth, G.
Die Gestalt der Kristallisationsfront und das damit verbundene monokristalline Wachstum im Czochralski-Kristallzuchtprozess hängt stark vom Verhältnis zwischen horizontalem und vertikalem Temperaturgradienten r*=deltaT_h/deltaT_v an der Schnittstelle zwischen Schmelze, Kristall und Atmosphäre ab. Der Wert von r* liegt dabei idealerweise in der Nähe von 1. Deshalb wurde ein Flüssigmetall-Modellexperiment aufgebaut, das die Untersuchung von r* unter dem Einfluss von Magnetfel-dern ermöglicht. Das zylindrische Flüssigmetallvolumen wird dabei homogen von unten geheizt, und um den wachsenden Kristall zu simulieren wird die Wärme oben konzentrisch mit einem Kühler entzogen, der die Oberfläche nur bis zu einem Drittel des Radius bedeckt. Ohne Strömungskontrolle findet sich ein von der Zielfunktion weit entfernter Wert von r*=3. Das Ziel r*=1 kann durch elektromagnetische Strömungsbeeinflussung erreicht werden.
  • Contribution to proceedings
    Workshop Elektroprozesstechnik, 23.-24.09.2010, Ilmenau - OT Heyda, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-14652
Publ.-Id: 14652


A physical model for electromagnetic control of local temperature gradients in a Czochralski system

Cramer, A.; Röder, M.; Pal, J.; Gerbeth, G.
The shape of the solidification front and the related mono-crystalline growth in the Czochralski crystal growth process is thought of being strongly influenced by the ratio of the horizontal and the vertical temperature gradient r* = deltaT_h / deltaT_v at the triple point liquid-solid-atmosphere, which ratio desirably should be in the order of unity. A liquid metal model experiment was therefore built that allows studying r* under the influence of magnetic fields. The cylindrical liquid metal column was homogeneously heated from below, whereas on top the heat was extracted in a centrical region covering only one third of the surface in order to simulate the growing crystal. Without flow control, r* ≈ 3 is far removed from unity. It was then possible to reach the target value r* = 1 for any temperature difference between the bottom and the top at a moderate field strength while applying a rotating magnetic field.
Keywords: crystal growth, Czochralski process, flow control, electromagnetic processing of materials, magnetic fields
  • Lecture (Conference)
    International Scientific Colloquium on Modelling for Material Processing, 16.-17.09.2010, Riga, Lettland
  • Contribution to proceedings
    International Scientific Colloquium Modelling for Material Processing, 16.-17.09.2010, Rīga, Latvija
    Proceedings of the 6th International Scientific Colloquium Modelling for Material Processing, 978-9984-45-223-4, 41-46
  • Magnetohydrodynamics 46(2010), 353-362

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Publ.-Id: 14651


Magnetic field controlled single crystal growth and surface modification of titanium alloys exposed for biocompatibility

Hermann, R.; Calin, M.; Uhlemann, M.; Wendrock, H.; Gerbeth, G.; Büchner, B.; Eckert, J.
The aim of the work is the growth and characterisation of Ti55Nb45 (wt %) single crystals with the floating-zone single crystal growth of intermetallic compounds using two-phase radio-frequency (RF) electromagnetic heating. Thereby, the process and, in particular, the flow field in the molten zone is influenced via additional magnetic fields. The growth of massive intermetallic single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. It is generally known that the crystallization process stability is enhanced if the crystallization interface is convex. As a result, a tailored magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards to outwards flows. Due to their attractive properties such as light, strong and totally biocompatible, titanium is one of few materials that naturally match the requirements for implantation in the human body. Therefore, the magnetic system was applied to crystal growth of Ti alloys. The grown crystals were oriented and cut to cubes with the desired crystallographic orientations (-1,0,0) and (1,0,1) normally on a plane. The electron backscatter diffraction (EBSD) technique was applied to clearly define crystal orientation and orientation changes in the crystallographic textures. The elastic modulus, the shear modulus and the bulk modulus were determined in dependence on the crystal orientation using ultrasonic measurements. Moreover, the oxide formation behavior on Ti surfaces in dependence on the grain orientation was investigated, performed anodically from fluoride containing electrolyte.
  • Lecture (Conference)
    The 16th International Conference on Crystal Growth (ICCG-16), 08.-13.08.2010, Beijing, China
  • Journal of Crystal Growth 318(2011)1, 1048-1052
    DOI: 10.1016/j.jcrysgro.2010.10.196

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Permalink: https://www.hzdr.de/publications/Publ-14650
Publ.-Id: 14650


Thermophysical properties of intermetallic Ti-Al alloys in the liquid state

Plevachuk, Y.; Sklyarchuk, V.; Hermann, R.; Gerbeth, G.
TiAl intermetallic alloys were developed as potential materials for high temperature applications because of their excellent chemical and physical properties such as low density, high modulus and corrosion resistance. These characteristics are attractive for applications in aerospace and automotive industries but also for chemical and biomedical application. However, their low ductility at room temperature limits their application. Also microscopic factors like volume fraction of the apparent phases, the distribution of orientation variants, fineness of the microscopic structure strongly affect the mechanical properties.
  • Lecture (Conference)
    Liquid and Amorphous Metals Conference (LAM 14), 11.-16.07.2010, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-14649
Publ.-Id: 14649


Thermophysical and structure-sensitive properties of low-temperature ternary liquid metal eutectics

Plevachuk, Y.; Sklyarchuka, V.; Gerbeth, G.; Eckert, S.
Investigation of thermophysical and structure-sensitive properties of liquid low-temperature ternary metal eutectic alloys are stimulated both by pure academic as well as by applied science. In particular, there exist few reliable experimental data on the electrophysical, transport and surface properties of multicomponent alloys and, therefore, they are often estimated with analytical approaches. In order to prove any theory, experimental results are needed.
The favorable combination of the technical characteristics of Ga-based melts brought about their extensive application as sliding contacts, the working medium of magnetohydrodynamic devices, heat-sensitive elements of liquid-metal thermometers and thermocouples, and the base for conducting magnetic fluids. The GaInSn eutectic alloy is a suitable alternative to mercury since it exhibits an equilibrium melting point of 284 K. Bi-Pb-Sn liquid eutectics are chosen as model substances for experimental
  • Poster
    XIV Liquid and Amorphous Metals Conference (LAM 14), 11.-16.07.2010, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-14648
Publ.-Id: 14648


Saturation correction of an ionization chamber for short and intense beam pulses

Karsch, L.; Richter, C.; Pawelke, J.
no abstract available
Keywords: saturation correction, ionization chamber, short and intense beam pulse
  • Poster
    OncoRay Retreat, 27.-28.01.2010, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14647
Publ.-Id: 14647


An integrated dosimetry and cell irradiation device for in vitro cell experiments with laser accelerated protons

Richter, C.; Akhmadaliev, S.; Dammene, Y.; Karsch, L.; Reinhardt, S.; Sobiella, M.; Schürer, M.; Weber, A.; Pawelke, J.
no abstract available
Keywords: dosimetry, cell irradiation, in vitro cell experiments, laser accelerated protons
  • Poster
    OncoRay Retreat, 27.-28.01.2010, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14646
Publ.-Id: 14646


Liquid metal modelling of continuous steel casting

Gerbeth, G.; Eckert, S.; Timmel, K.; Miao, X.
Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. We present the new experimental facility CONCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. The possibilities for flow investigations in tundish, submerged entry nozzle and mould will be discussed. In addition, experimental results will be presented on the impact of a steady magnetic field on the outlet flow from the nozzle, obtained at a smaller-scale set-up working with the room-temperature alloy GaInSn. Local velocities in both facilities are measured by Ultrasound Doppler Velocimetry and contactless inductive flow tomography. The latter is attractive also for real-scale steel casting.
  • Lecture (Conference)
    TMS Annual meeting "Jim Evans Honorary Symposium", 14.-18.02.2010, Seattle, USA
  • Contribution to proceedings
    TMS Annual meeting, 14.-18.02.2010, Seattle, USA
    "Jim Evans Honorary Symposium", 55-62

Permalink: https://www.hzdr.de/publications/Publ-14645
Publ.-Id: 14645


Radiobiological preparation of in vitro cell experimentes with laser accelerated protons

Beyreuther, E.; Dammene Debbih, Y.; Karsch, L.; Laschinsky, L.; Lessmann, E.; Naumburger, D.; Richter, C.; Schürer, M.; Pawelke, J.
no abstract available
Keywords: in vitro cell experimentes, laser accelerated protons
  • Poster
    OncoRay Retreat, 27.-28.01.2010, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14644
Publ.-Id: 14644


Influence of ultra-high pulse dose rate on biological effectiveness of laser accelerated electrons

Laschinsky, L.; Beyreuther, E.; Karsch, L.; Leßmann, E.; Naumburger, D.; Richter, C.; Schürer, M.; Pawelke, J.
no abstract available
Keywords: ultra-high pulse dose rate, biological effectiveness, laser accelerated electrons
  • Poster
    OncoRay Retreat, 27.-28.01.2010, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14643
Publ.-Id: 14643


Biological effectiveness of laser-accelerated electrons in comparison to conventional accelerated electrons

Naumburger, D.; Beyreuther, E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H. P.; Baumann, M.
no abstract available
Keywords: biological effectiveness, laser-accelerated electrons, electrons
  • Poster
    OncoRay Retreat, 27.-28.01.2010, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14642
Publ.-Id: 14642


Research of the laser-radiooncology (onCOOPtics) group

Pawelke, J.
no abstract available
Keywords: laser radiooncology
  • Invited lecture (Conferences)
    OncoRay Retreat, 27.-28.01.2010, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14641
Publ.-Id: 14641


Modelling, Simulation and Experiments to Boiling in Pressurized Water Reactors in the framework of the R&D program “Energie 2020+”

Krepper, E.
Der Vortrag gibt einen Überblick zu diesem Verbundprojekt. Die im Rahmen des Förderprogramms Energie 2020+ durch das Bundesministerium für Bildung und Forschung geförderten und gemeinsam von den Partnern Forschungszentrum Dresden-Rossendorf (FZD), Technische Universität Dresden (TUD), Hochschule Zittau/Görlitz (HSZG), Karlsruher Institut für Technologie (KIT), Ruhr-Universität Bochum (RUB), Technische Universität München (TUM) und ANSYS Germany durchgeführten Arbeiten sind der Weiterentwicklung und Validierung von CFD-Modellen für Siedevorgänge in Druckwasserreaktoren, vom Blasensieden bis hin zu Phänomenen des Filmsiedens, gewidmet. Das auf die Grundlagen orientierte Vorhaben schließt die Modellentwicklung, die Simulation und Experimente in verschiedenen Maßstäben ein. Kleinskalige Experimente an den Hochschulen dienen der Aufklärung mikroskopischer Phänomene. An der Großversuchsanlage TOPFLOW wird ein Bündelexperiment zur integralen Validierung der Modelle aufgebaut. Die Ausrüstung dieses Experiments mit schneller Röntgentomographie wird störungsfrei zeitlich und räumlich hoch aufgelöste Daten liefern, die für die Entwicklung und Validierung von CFD-Modellen geeignet sind. Die TU Dresden wird den Einfluss chemischer Zusätze auf die Ausprägung kritischer Siedezustände an der Versuchsanlage BORAN untersuchen. Durch den Einsatz neuester und zum Teil eigens zu entwickelnder Messtechnik wird ein signifikanter Erkenntniszuwachs gegenüber dem Stand von Wissenschaft und Technik erreicht werden.
Keywords: CFD, boiling, model development, small scale experiments, large scale tests
  • Lecture (Conference)
    Sitzung des CFD-Verbundes, 21.-22.07.2010, Jülich, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14640
Publ.-Id: 14640


CFD modelling of boiling in rod bundles

Krepper, E.; Rzehak, R.
The presentation shows the application of the CFD wall boiling model on the computation of a rod bundle. The data of the OECD/NEA Benchmark Based on NUPEC PWR Subchannel and Bundle Test (PSBT) were used. Besides the parameters of the wall boiling model the simulation of turbulence in the narrow channels is essential.
Keywords: CFD, two phase flow, wall boiling, rod bundle, OECD benchmark PSBT
  • Lecture (Conference)
    8th FZD & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 22.-24.06.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14639
Publ.-Id: 14639


Development and validation of the wall boiling model in ANSYS CFD

Frank, T.; Lifante, C.; Burns, A.; Krepper, E.; Rzehak, R.
The presentation shows the actual state of model implementation of a wall boiling model in the code ANSYS/CFX. Publisherd experimental data are used to validate the model
Keywords: CFD, two phase flow, wall boiling, model development, validation
  • Lecture (Conference)
    8th FZD & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 22.-24.06.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14638
Publ.-Id: 14638


Contactless inductive flow tomography: principles and applications

Wondrak, T.; Stefani, F.; Gerbeth, G.; Gundrum, T.
There is a growing interest in the determination of the velocity field of metal or semiconductor melts in many industrial applications, such as steel casting and silicon growth. Due to the opaqueness of those fluids optical methods are not applicable. Furthermore these fluids are often very hot or chemically aggressive, so a contactless measuring technique would be highly desirable. Interestingly, those metal and semiconductor melts are characterized by a relatively high electrical conductivity. Exposing the flow of such melts to an externally applied magnetic field, electrical currents are induced which give rise to a perturbation of the applied field. This flow induced field perturbation, which is detectable outside the fluid volume, contains information about the flow structure and can be exploited to reconstruct the velocity field. By applying consecutively the external magnetic field in different directions, different induced currents and magnetic fields can be produced from the same velocity. This enables a tomographic reconstruction of the flow field. Such a contactless inductive flow tomography (CIFT) was proposed, and later verified experimentally. The determination of the velocity from the measured induced magnetic field is an ill-posed linear inverse problem. One of the key problems is the inherent non-uniqueness of the reconstruction. For the velocity reconstruction we circumvent this non-uniqueness problem by using Tikhonov regularization and the method of the L-curve to identify automatically the best regularization parameter. At the point of strongest curvature (the knee) of the L-curve one expects the most reasonable compromise between the fit of the modeled magnetic fields to the measured ones on one hand, and the minimum kinetic energy on the other hand. One possible application of CIFT is the continuous casting process which is widely used in the steel producing industry. The flow structure in the mould, where the steel starts to solidify, is of particular interest since it is mainly responsible for the quality of the produced steel slabs. Since for thin slab casting the velocity can be assumed to be mainly two-dimensional it is sufficient to apply only one external field. We show that the CIFT method is able to reconstruct a numerically determined flow field with an empirical correlation coefficient of about 75 per cent. Then we apply the method to different flow configurations in a real model and show that typical flow features can be reliably detected.
Keywords: velocity measurement, liquid metals, continuous casting, inverse problems
  • Lecture (Conference)
    5th International Conference: Inverse Problems: Modeling and Simulation, 24.-29.05.2010, Antalya, Türkei

Permalink: https://www.hzdr.de/publications/Publ-14637
Publ.-Id: 14637


Use of electromagnetic induction tomography for monitoring liquid metal/gas flow regimes on a model of an industrial steel caster

Terzija, N.; Yin, W.; Peyton, A.; Gerbeth, G.; Stefani, F.; Timmel, K.; Wondrak, T.
Monitoring of the steel flow through the submerged entry nozzle (SEN) during continuous casting presents a challenge for the instrumentation system because of the high temperature environment and the limited access to the nozzle in between the tundish and the mould. Electromagnetic inductance tomography (EMT) presents an attractive tool to visualize the steel flow profile within the SEN.
In this paper, we investigate various flow regimes over a range of stopper positions and gas volume flow rates on a model of a submerged entry nozzle. A scaled (approx. 10:1) experimental rig consisting of a tundish, stopper rod, nozzle and mould was used. Argon gas was injected through the centre of the stopper rod and the behaviour of the two phase GaInSn / Argon flow was studied. The experiments were performed with GaInSn as an analogue for liquid steel, which has similar conductive properties as molten steel and allows the measurements at the room temperature. The electromagnetic system used in our experiments to monitor the behavior of the two phase GaInSn / Argon flow consisted of an array of 8 equally spaced inductive coils arranged around the object, a data acquisition system and a host computer. The present system operates with a sinusoidal excitation waveform with a frequency of 20 kHz and the system has a capture rate of 40 frames per second.
The results show the ability of the system to distinguish the different flow regimes and to detect the individual bubbles. Sample tomographic images given in the paper clearly illustrate the different flow regimes.
Keywords: two­phase flow study, electromagnetic inductance tomography, industrial steel caster model
  • Contribution to proceedings
    6th World Congress on Industrial Process Tomography, 06.-9.9.2010, Peking, China, 1033-1041
  • Measurement Science and Technology 22(2011)1, 015501
    DOI: 10.1088/0957-0233/22/1/015501

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-14636
Publ.-Id: 14636


Contactless inductive flow tomography: principles and application to a model of continuous casting

Wondrak, T.; Stefani, F.; Timmel, K.; Galindo, V.; Gundrum, T.; Gerbeth, G.
In many metal casting processes the flow structure in the mould is very important for the produced material. For instance the flow field in the mould in the continuous casting process plays an important role for slug entrainment and surface defects. The measurement of that velocity field is very difficult due to the opaqueness and the high temperature of the liquid steel. One possible measurement technique is the contactless inductive flow tomography (CIFT), which is able to reconstruct the three dimensional velocity field in electrically conducting melts from externally measured induced magnetic fields.
Since for thin slab casting the velocity can be assumed to be mainly two-dimensional it is sufficient to apply only one external magnetic field and to measure the induced fields at the narrow faces of the mould. We utilize CIFT for visualizing the flow of GaInSn in a model of continuous steel casting. In a first step we show that a numerically determined flow field can be reconstructed by CIFT with an empirical correlation coefficient of nearly 80 per cent. Then we apply the method to the real model and show that typical flow features can be reliably detected.
Keywords: velocity measurement, liquid metals, continuous casting
  • Lecture (Conference)
    6th World Congress on Industrial Process Tomography, 06.-9.9.2010, Peking, China
  • Contribution to proceedings
    6th World Congress on Industrial Process Tomography, 06.-9.9.2010, Peking, China
    6th World Congress on Industrial Process Tomography, 1051-1066

Permalink: https://www.hzdr.de/publications/Publ-14635
Publ.-Id: 14635


Contribution of Lattice Vibrations to the Thermodynamics of Vacancy Clusters in bcc-Fe

Talati, M.; Posselt, M.; Bonny, G.; Al-Motasem, A. T.; Bergner, F.
During the long operation time of nuclear reactors, vacancies and vacancy clusters (VC) may play an intermediary role in the formation of copper-rich precipitates (CRP), which are considered to be the main cause of hardening and embrittlement of Cu-bearing RPV steels since these defects act as obstacles to dislocation motion within the grains of polycrystalline bcc-Fe. The effect of irradiation on the microstructure of RPV steels and consequently on their mechanical properties is a multiscale phenomenon. The evolution of VCs over realistic time and length scales can be effectively studied by rate theory. However, many parameters used, such as the free binding energies of precipitates, are not very well known from experimental investigations. Atomic-level computer simulations can provide these data. The few previous attempts to include the effect of lattice vibrations into thermodynamics of Cu-precipitates in bcc-Fe did not lead to consistent results [1, 2].The present investigations are focused on the phonon contributions to the thermodynamics of VCs. In all calculations the Mendelev potential for bcc Fe is used [3]. Molecular dynamics simulations at different temperatures are performed in order to determine the velocity autocorrelation function which can be transformed into the vibrational density of states (VDOS). VDOS is also obtained using dynamical matrix method under harmonic approximation. This quantity is then used to calculate the contributions of lattice vibrations to the total free energy of bcc-Fe as well as to the free energy of formation and free binding energy of VCs. The vibrational contribution to the total free energy of bcc-Fe is compared with available CALPHAD data and with the values obtained using other interatomic potentials. At a temperature of 600 K the vibrational contribution to the free binding energy leads to a reduction of the absolute value of the corresponding zero-Kelvin free binding energy of the VC by about 10%.

[1] K. Yuge, A. Seko, I. Tanaka, S. R. Nishitani, Phys. Rev. B 72 (2005) 174201.
[2] K. Yuge, A. Seko, K. Kobayashi, T. Tatsuoka, S. R. Nishitani, H. Adachi, Mater. Trans. 45 (2004) 1473.
[3] M. I. Mendelev, S. Han, D. J. Srolovitz, G. Ackland, D. Y. Sun, M. Asta, Philo. Mag. 83 (2003) 3977.
Keywords: Vibrational Density of States, Total free energy, Free binding energy, bcc-Fe , Thermodynamics, Molecular Dynamics Simulation
  • Poster
    The fifth International Conference on Multiscale Materials Modeling (MMM-2010), 04.-08.10.2010, Freiburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-14634
Publ.-Id: 14634


Boiling models for CFD

Rzehak, R.; Krepper, E.
CFD for Boiling Flows requires models to represent bubble dynamics during ebullition cycle. At present, mostly empirical correlations are used to this end, which have only a limited range of applicabiblity. Hence, there is a strong desire to replace these correlations by physical models. A survey of available approaches to this issue is given and need for further research identified.
Keywords: CFD, boiling
  • Lecture (Conference)
    8th FZD & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 22.-24.06.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14633
Publ.-Id: 14633


Measurement technique developments for LBE flows

Buchenau, D.; Eckert, S.; Gerbeth, G.; Stieglitz, R.; Dierckx, M.
We report on the development of measurements techniques for flows in lead-bismuth eutectic alloys (LBE). This paper covers the test results of newly developed contact-less flow rate sensors as well as the development and test of the LIDAR technique for operational free surface level detection. The flow rate sensors are based on the flow-induced disturbance of an externally applied AC magnetic field which manifests itself by a modified amplitude or a modified phase of the AC field. Another concept of a forcefree contactless flow meter uses a single cylindrical permanent magnet. The electromagnetic torque on the magnet caused by the liquid metal flow sets the magnet into rotation. The operation of those sensors has been demonstrated at liquid metal test loops for which comparative flow rate measurements are available, as well as at the LBE loops THESYS at KIT and WEBEXPIR at SCK-CEN. For the level detection a commercial LIDAR system was successfully tested at the WEBEXPIR facility in Mol and the THEADES loop in Karlsruhe.
Keywords: Liquid metal, LBE, Phase-shift sensor, EMFM, Rotating magnet, LIDAR
  • Lecture (Conference)
    Int. DEMETRA Workshop, 02.-04.03.2010, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14632
Publ.-Id: 14632


Interfacial heat and mass tansfer models

Krepper, E.; Scheuerer, G.
The lesson 4 of the "Short Course on Multiphase Flow Modelling" deals with the simulation of mass and energy exchange between the phases based on the two fluid model approach. After the basic principles the lesson describes the simulation of subcooled boiling and the simulation of cavitation processes.
Keywords: CFD, Two fluid model, heat transfer, mass transfer, boiling, cavitation
  • Invited lecture (Conferences)
    7th FZD & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 26.-28.05.2009, Dresden, Deutschland
  • Invited lecture (Conferences)
    8th FZD & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 22.-24.06.2010, Dresden, Deutschland
  • Invited lecture (Conferences)
    9th FZD & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 08.-10.06.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-14629
Publ.-Id: 14629


CFD models for the description of particle transport, deposition and (re)mobilization of deposited particles at walls

Barth, T.; Krepper, E.
Radioactive aerosol deposition and the assessment of its resuspension during a design basis accident (DBA) in the primary circuit have been revealed in the past as a key issue in the development and certification of advanced pebble bed High Temperature Reactors (HTRs). The report describes the particle parametres to be expected. Actual CFD methods to model particle deposition and particle resuspension are reported.
Keywords: CFD, Euler/Lagrange, Particles, Deposition, Resuspension
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2010
    FZD\FWS\2010\06
    22 Seiten

Permalink: https://www.hzdr.de/publications/Publ-14625
Publ.-Id: 14625


Extension of the MUSIG approach by considering gas/liquid-mass transfer

Krepper, E.; Lucas, D.; Schmidtke, M.
The report describes the derivation of the corresponding equation and validations on the TOPFLOW condensation experiments (test series K16). The evolution of the cross-sectional averaged void fraction along the pipe were compared with experimental results. In the test K16_118 the condensation of steam was prevailing. The influence of the heat transfer model bubble – liquid (Ranz-Marshall, Hughmark, Tomiyama) was investigated and the influence of the initial bubble size distribution was shown. In the tests K16_140 reevaporation caused by decreasing hydrostatic pressure was found in the experiments and simulated.
Keywords: CFD, two phase flow, bubble population balance, mass transfer
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2010
    FZD\FWS\2010\05
    22 Seiten

Permalink: https://www.hzdr.de/publications/Publ-14624
Publ.-Id: 14624


Improvement of the turbulence modelling in Euler/Eulerian CFD simulation of gas/liquidflow

Krepper, E.; Schmidtke, M.; Lucas, D.
In the Euler/Eulerian approach simulating bubbly flow, the influence of the bubbles on the turbulence of the liquid has to be modelled. Vice versa, the structures of the turbulent liquid flow influence the gas void fraction distribution, which is expressed as a turbulent dispersion force. Reliable models for turbulence are an urgent precondition for the improvement of models describing bubble coalescence and bubble breakup in any population balance model. In the present work the different approaches simulating the influence of bubbles on the turbulence are revised and compared to measurements using ANSYS-CFX. Models for the turbulent dispersion force are validated.
Keywords: CFD, two phase flow, turbulence
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2010
    FZD\FWS\2010\04
    18 Seiten

Permalink: https://www.hzdr.de/publications/Publ-14623
Publ.-Id: 14623


Die supraleitende HF-Fotoelektronenquelle am ELBE-Beschleuniger im FZD

Teichert, J.
kein Abstract vorhanden.
Keywords: SRF Gun, Cs2Te, electron injector
  • Lecture (others)
    MAMI Seminar, 28.01.2010, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-14622
Publ.-Id: 14622


Study of gas-liquid two-phase flow in pipes with ultrafast electron beam X-ray CT

Fischer, F.; Hampel, U.
Electron beam X-ray CT is capable of fast measurement of multi-phase flows with frame rates of 1000 images per second and higher. The principle is based on the creation of a moving X-ray spot by electromagnetic deflection of a high-intensity electron beam across a circular target within an evacuated scanner enclosure. Together with a fixed fast X-ray detector this setup allows scanning of objects at frame rates well beyond that of classical CT machines. Our group has developed a scanner that is capable of scanning at up to 7 kHz frame rate and approximately 1 mm spatial resolution. The technique allows visualizing and measuring multiphase flows in vessels of moderate size. We have applied this fast electron X-ray tomography to the study of gas-liquid flow in a vertical pipe of 50 mm inner diameter. Different two-phase flow regimes from bubbly flow to churn-turbulent flow were produced and scanned. The data were processed using self-made image reconstruction software which implements the filtered backprojection technique and further post-processing algorithms for determination of gas-phase parameters, such as temporal and radial gas fraction profiles.
Keywords: Electron beam tomography, X-ray tomography, flow measurement, two-phase flow
  • Lecture (Conference)
    6th World Congress of Industrial Process Tomography, 06.-09.09.2010, Peking, China

Permalink: https://www.hzdr.de/publications/Publ-14619
Publ.-Id: 14619


Alfven wave experiments with liquid rubidium

Gundrum, T.; Hüller, J.; Stefani, F.; Gerbeth, G.; Galindo, V.; Herrmannsdörfer, T.; Arnold, F.; Putzke, C.
Since their discovery by Hannes Alfvén in 1942, Alfvén waves have played an ever increasing role in explaining many phenomena in astrophysical and fusion related plasmas. The experimental investigation of Alfvén waves had started shortly after Alfvéns prediction, with first experiments using mercury and liquid sodium. Since those times, many Alfvén wave experiments have been carried out, both in liquid metals and, even more extensively, in plasmas.
Interestingly, the recent developments in reaching pulsed magnetic fields above 50 Tesla open up quite new prospects for Alfvén wave experiments with liquid metals. At those field strengths it happens that the Alfvén speed in higher alkalis metals reaches the sound speed (the threshold is 51 T for Caesium and 55 T for Rubidium). This threshold is of upmost importance for the character of Alfvén waves and its relation to slow and fast magnetoacoustic waves, and its crossing has been made responsible for the corona heating.In order to check the feasibility of experiments with higher alkali metals, we have carried out at Dresden High Magnetic Field Laboratory a preliminary experiment. This first test experiment has yielded a proof of concept, and first promising results have been achieved.
Keywords: Alfven, MHD, Rubidium, magnetoacoustic wave, liquid metal, high magnetic field
  • Lecture (Conference)
    Science in High Magnetic Fields, 05.-11.09.2010, Ameland, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-14618
Publ.-Id: 14618


Use of Superconducting LINACS for Positron Generation: The EPOS System at Research Center Dresden-Rossendorf

Krause-Rehberg, R.; Jungmann, M.; Krille, A.; Werlich, B.; Pohl, A.; Anwand, W.; Brauer, G.; Butterling, M.; Büttig, H.; Kosev, K. M.; Teichert, J.; Wagner, A.; Cowan, T. E.
Intense positron sources require the pair production process for the positron generation. In case a pulsed positron source shall be constructed, a superconducting Linac-based accelerator allows generating the required final time structure for the electron beam. This simplifies the positron beam construction. The first such setup, the EPOS system at the Research Center Dresden-Rossendorf, will be described.
  • Lecture (Conference)
    12th International Workshop on Slow Positron Beam Techniques, 01.-06.08.2010, North Queensland, Australia
  • Contribution to proceedings
    12th International Workshop on Slow Positron Beam Techniques, 01.-06.08.2010, North Queensland, North Queensland
    Use of Superconducting LINACS for Positron Generation: The EPOS System at Research

Permalink: https://www.hzdr.de/publications/Publ-14617
Publ.-Id: 14617


SRF Gun Experiments

Teichert, J.; Arnold, A.; Büttig, H.; Lehnert, U.; Michel, P.; Murcek, P.; Schneider, C.; Schurig, R.; Staats, G.; Xiang, R.; Kneisel, P.; Kamps, T.; Rudolph, J.; Schenk, M.; Klemz, G.; Will, I.
kein Abstract vorhanden
  • Lecture (others)
    EuCARD-SRF Annual Review 2010, 07.-09.04.2010, Daresbury, UK

Permalink: https://www.hzdr.de/publications/Publ-14616
Publ.-Id: 14616


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