102,144 research outputs found
The Ternary System Yb-Cu-Mg: Isothermal Section at 400 °C in the Range from 0 to 67 at.% Cu
No full textPhase equilibria in systems Ce-M-Sb (M=Si, Ge, Sn) and superstructure Ce12Ge9-xSb23-x (x=3.8+/-0.1)
No full textDFT simulation of the physical properties of the newly discovered Ti₃Co₅B₂ -type novel borides Mn₃₋ₓ {Rh,Ir}₅B₂ using HPC in addition to X-ray single crystal and TEM data evaluation
No full textBoron has unique chemical properties and with it´s ability of reactions with metals boron yields to a large class of metal borides with high melting points and super hardness [1,2]. Some metal borides are superconductors and there are many borides with extraordinary magnetic properties [3].
While investigating the phase relations in the Mn-{Rh,Ir }-B system we have discovered for both systems a ternary compound, Mn(3−x){Rh,Ir}5B2. The crystal structure of both compounds were determined from X-ray single crystal data to be isotypic with the Ti3Co5B2-type (space group P4/mbm, No. 127). Remarkably, both cases exhibit a significant defect at the Mn 2a sites, which is at the origin of the unit cell.
The absence of a superstructure related to these defects is confirmed by transmission electron microscopy studies, in fact Mn atoms and their corresponding vacancies randomly share the 2a sites in a small unit cell.
The aim of this presentation is to show that we can model this randomly occurring vacancies of Mn atoms in the above mentioned crystallographic positions with large supercell simulations. We initially perform a
full relaxation of the lattice parameters and ionic positions for the unit cell with no vacancies followed by supercell calculations with cells as large as 2 × 2 × 3, which results in a 240 atoms structure. The effect of the Mn vacancies is then simulated by running calculations with some Mn atoms removed from the 2a site (out of 24).
To run simulations on such big supercells we needed the aid of high-performance computing (HPC) and, therefore, did our calculations on the Vienna Scientific Cluster (VSC). We have run several tests with the
Vienna ab-initio simulation package VASP, which we have used for our density functional theory (DFT) approach to find out the optimal adjustments for the parallelism settings. The results of this investigation will be presented here.
References
[1] Steiner, S., Rogl, G., Flansdorfer, H., Noel, H., Gonçalves, A.P., Giester, G., and Rogl, P.F., J. Alloy.
Comp. 811, 151578 (2019).
[2] Steiner, S., Rogl, G., Michor, H., Giester, G., Rogl, P.F., and Gonçalves, A.P., Dalton Trans. 47, 12933
(2018).
[3] Ali, T., Steiner, S., Ritter, C., and Michor, H., J. Alloy. Comp. 716, 251 (2017)
Understanding thermal and electronic transport in high-performance thermoelectric skutterudites
No full textFilled Sb-based skutterudites are considered one of the most appealing thermoelectric materials in the mid temperature range. Even though Sb is not one of the most abundant elements in nature, the large thermoelectric figure of merit of these materials makes them attractive for applications such as thermoelectric generators. In order to get deeper insight into the fundamental physical mechanisms of thermal and electronic transport properties, we studied the temperature dependent electrical resistivity, Seebeck coefficient, thermal conductivity and specific heat. Three groups of skutterudites with excellent thermoelectric performance were investigated: (a) DDyFe4-xCoxSb12 (0 ≤ x ≤ 4; 0.08≤ y ≤ 0.7), to study the influence of Fe/Co substitution and the resulting filling level y as well as the influence of grain size, (b) DD0.7Fe3CoSb12 samples prepared from the same powder to study the effect of different synthesis nanostructuring techniques (hot-pressed, hot pressed and processed via high pressure torsion and cold-pressed and processed via high pressure torsion) and (c), a DD-filled skutterudite with and without Sb/Sn substitution before and after annealing. An overview of experimental investigations of the low-temperature transport is given and appropriate phenomenological models are adopted to elucidate the temperature-dependent features and the origin of high thermoelectric performance in these systems.Fil: Rogl, G.. Universidad de Viena; AustriaFil: Garmroudi, F.. Tu Wien; AustriaFil: Riss, A.. Vienna University of Technology; AustriaFil: Yan, X.. Vienna University of Technology; AustriaFil: Sereni, Julian Gustavo Renzo. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Bauer, E.. Vienna University of Technology; AustriaFil: Rogl, P.. Universidad de Viena; Austri
Constitution of the binary M-Sb systems (M = Ti, Zr, Hf) and physical properties of MSb2
No full textThis study is closely related to the chemical interactions in thermoelectric joints of a hot metal electrode with p- and n-type skutterudite. As a result of this work, a first and complete phase diagram has been constructed for the TiâSb system as well as partial phase diagrams (>65 at.% Sb) for the systems ZrâSb and HfâSb. Investigations are based on X-ray powder and single crystal analyses (determination of the crystal structure of Ti5Sb8with Zr2.6Ti2.4Sb8-type, space group I4122; RF= 0.032), electron probe microanalyses (EPMA) and differential thermal analyses (DTA). Physical properties were evaluated for the binary compounds MSb2(M = Ti, Zr, Hf) comprising electrical resistivity (from 4.2 K to 825 K), specific heat, thermal conductivity and thermal expansion coefficient (from 4.2 K to 300 K), Seebeck coefficient (from 300 K to 825 K) and elastic moduli at 300 K. These data will serve to evaluate the potential of MSb2compounds (M = Ti, Zr, Hf) for thermoelectric devices, where these phases predominantly appear in the diffusion zones of the hot metal electrode with p- and n-type skutterudite
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Effect of chemical composition on ground state properties of Ce and Yb intermetallic compounds
No full textPhase relations and crystal structure of τ6-Ti2(Ti0.16Ni0.43Al0.41)3
No full textTi2(Ti0.16Ni0.43Al0.41) 3 is a novel compound (labeled as τ6) in the Ti-rich region of the Ti-Ni-Al system in a limited temperature range 870 < T < 980 °C. The structure of τ6-Ti2(Ti,Ni,Al)3 was solved from a combined analysis of X-ray single crystal and neutron powder diffracton data (space group C2/m, a = 1.85383(7) nm, b = 0.49970(2) nm, c = 0.81511(3) nm, and β = 99.597(3)°). τ6-Ti 2(Ti,Ni,Al)3 as a variant of the V2(Co 0.57Si0.43)3-type is a combination of slabs of the MgZn2-Laves type and slabs of the Zr4Al 3-type forming a tetrahedrally close-packed Frank-Kasper structure with pentagon-triangle main layers. Titanium atoms occupy the vanadium sites, but Ti/Ni/Al atoms randomly share the (Co/Si) sites of V2(Co 0.57Si0.43)3. Although τ6 shows a random replacement on 6 of the 11 atom sites, it has no significant homogeneity range (∼1 at. %). The composition of τ6 changes slightly with temperature. DSC/DTA runs (1 K/min) were not sufficient to define proper reaction temperatures due to slow reaction kinetics. Therefore, phase equilibria related to τ6 were derived from X-ray powder diffraction in combination with EPMA on alloys, which were annealed at carefully set temperatures and quenched. τ6 forms from a peritectoid reaction η-(Ti,Al)2Ni + τ3 + α2 ↔ τ6 at 980 °C and decomposes in a eutectoid reaction τ6 ↔ η + τ4 + α2 at 870 °C. Both reactions involve the η-(Ti,Al)2Ni phase, for which the atom distribution was derived from X-ray single crystal intensity data, revealing Ti/Al randomly sharing the 48f- and 16c-positions in space group Fd3̄m (Ti2Ni-type, a = 1.12543(3) nm). There was no residual electron density at the octahedral centers of the crystal structure ruling out impurity stabilization. Phase equilibria involving the τ6 phase have been established for various temperatures (T = 865, 900, 925, 950, 975 °C, and subsolidus). The reaction isotherms concerning the τ6 phase have been established and are summarized in a Schultz-Scheil diagram
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