P. Jóvári, A. Piarristeguy, Raphaël Escalier, I. Kaban, Jozef Bednarčík, A. Pradel,
Amorphous GexTe100−x alloys were obtained over a broad composition range (12 ≤ x ≤ 44.6) by thermal co-evaporation. Their structure was investigated by x-ray diffraction and extended x-ray absorption fine structure measurements. Experimental datasets were fitted simultaneously by the reverse Monte Carlo simulation technique. It is concluded that Te is mostly twofold coordinated and the majority of Ge atoms have four neighbours. The number of Ge–Ge and Te–Te bonds evolves monotonically with composition. ...
Tópico(s): Chalcogenide Semiconductor Thin Films
2013 - IOP Publishing | Journal of Physics Condensed Matter
Amir Hossein Taghvaei, Mihai Stoica, Mohsen Samadi Khoshkhoo, I. Kaban, Jozef Bednarčík, P. Jóvári, K. Janghorban, J. Eckert,
In this letter we report about a new melt-spun Co40Fe22Ta8B30 metallic glass with a wide supercooled liquid region of 74 K. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) investigations confirmed that crystallization occurs with significantly longer incubation time during annealing above the glass transition, as compared to the well-known Co43Fe20Ta5.5B31.5 glassy alloy. The new alloy as a good soft magnetic material showed a very low coercivity of 0.8 A/m and ...
Tópico(s): Phase-change materials and chalcogenides
2012 - Elsevier BV | Materials Letters
Amir Hossein Taghvaei, Mihai Stoica, I. Kaban, Jozef Bednarčík, J. Eckert,
The structural evolution of Co40Fe22Ta8B30 glassy particles has been studied by in-situ high-energy synchrotron X-ray diffraction (XRD) upon isochronal annealing. The changes in position, intensity, and full width at half maximum (FWHM) of the first and second diffuse maxima of the XRD patterns suggest the occurrence of irreversible structural relaxation upon the first heating up to a temperature close to the glass transition temperature Tg. The variations in reduced pair correlation functions upon ...
Tópico(s): Glass properties and applications
2014 - American Institute of Physics | Journal of Applied Physics
László Rátkai, Clément Conseil, V. Nazabal, Bruno Bureau, I. Kaban, Jozef Bednarčík, B. Beuneu, P. Jóvári,
The structure of Ge20SexTe80−x (x = 5, 10, 15, 20) glasses has been investigated by X-ray and neutron diffraction as well as Ge and Se K-edge extended X-ray absorption fine structure (EXAFS) measurements. Experimental datasets have been fitted simultaneously by the reverse Monte Carlo simulation technique. It has been found that all components obey the 8-N rule. Se binds preferentially to Ge. At x = 20, experimental data can be fitted without Se–Te bonding, but Se–Se bonds appear, and the Te–Te coordination ...
Tópico(s): Material Dynamics and Properties
2011 - Elsevier BV | Journal of Alloys and Compounds
P. Jóvári, Pierre Lucas, Zhiyong Yang, Bruno Bureau, I. Kaban, B. Beuneu, Jozef Bednarčík,
The structure of Te‐rich (75–80 at.% Te) and Te‐poor (40 at.% Te) Ge–As–Te glasses has been investigated by diffraction and extended X‐ray absorption fine structure ( EXAFS ) measurements. Large‐scale structural models have been created by fitting simultaneously diffraction and EXAFS datasets by the reverse Monte Carlo simulation technique. It is found that As–As bonds improve the fit quality in the case of Te‐rich glasses while no Ge–Ge bonding is necessary in these compositions. In the Te‐poor glasses, ...
Tópico(s): Crystal Structures and Properties
2014 - Wiley | Journal of the American Ceramic Society
Kaikai Song, Shuang Wu, I. Kaban, Mihai Stoica, Jozef Bednarčík, Baoan Sun, Chongde Cao, Gang Wang, Li Wang, J. Eckert,
The martensitic transformation within B2 phase plays a critical role for the ductility of CuZr-based bulk metallic glass (BMG) composites, yet the underlying mechanism for the martensitic transformation process needs further investigations. Here, we found that the onset temperature of the thermally-activated martensitic transformation for CuZr-based BMG composites was reduced to 162.7 ± 2.5 K, which is far lower than those of polycrystalline samples, due to the stabilization of the austenitic phase ...
Tópico(s): Glass properties and applications
2020 - Elsevier BV | Journal of Alloys and Compounds
Xilei Bian, G. Wang, Jun Yi, Yandong Jia, Jozef Bednarčík, Qijie Zhai, I. Kaban, Baran Sarac, Marlene Mühlbacher, Florian Spieckermann, Jozef Kečkéš, J. Eckert,
The temperature-dependent atomic structural evolution of a Zr64.13Cu15.75Ni10.12Al10 metallic glass is studied by in-situ high-energy X-ray diffraction in the temperature range of 79–553 K. The interatomic distance in the first nearest neighbor shell increases with decreasing temperature, while the interatomic distance in other atomic shells decreases. This decrease in the interatomic distances causes volume shrinkage and an increase in the strength of the metallic glass. The volume shrinkage can ...
Tópico(s): Material Dynamics and Properties
2017 - Elsevier BV | Journal of Alloys and Compounds
D. Holland‐Moritz, Fan Yang, Tobias Kordel, Stefan Klein, Florian Kargl, J. Gegner, Thomas C. Hansen, Jozef Bednarčík, I. Kaban, O. Shuleshova, N. Mattern, Andreas Meyer,
We report on investigations of the static structure factors of glass-forming Zr-Cu alloy melts by combination of the containerless processing technique of electrostatic levitation with diffraction of neutron and synchrotron radiation. The partial Bhatia-Thornton structure factors SNN and SNC were determined from the two total structure factors. While it is widely assumed in literature that the good glass-forming ability of Zr-Cu is related to an icosahedral short-range order prevailing in the melt, ...
Tópico(s): Material Dynamics and Properties
2012 - Institute of Physics | EPL (Europhysics Letters)
Mihai Stoica, S. Scudino, Jozef Bednarčík, I. Kaban, J. Eckert,
By adding 0.5 at. % Cu to the strong but brittle [(Fe0.5Co0.5)0.75Si0.05B0.20]96Nb4 bulk metallic glass, fully amorphous rods with diameters up to 2 mm were obtained. The monolithic samples with 1 mm diameter revealed a fracture strain of 3.80% and a maximum stress of 4143 MPa upon compression, together with a slight work-hardening behavior. SEM micrographs of fractured samples did neither reveal any shear bands on the lateral surface nor the typical vein patterns which characterize ductile fracture. ...
Tópico(s): Metallic Glasses and Amorphous Alloys
2014 - American Institute of Physics | Journal of Applied Physics
Shuai Wei, Fan Yang, Jozef Bednarčík, I. Kaban, O. Shuleshova, Andreas Meyer, Ralf Busch,
Polymorphic phase transitions are common in crystalline solids. Recent studies suggest that phase transitions may also exist between two liquid forms with different entropy and structure. Such a liquid–liquid transition has been investigated in various substances including water, Al2O3-Y2O3 and network glass formers. However, the nature of liquid–liquid transition is debated due to experimental difficulties in avoiding crystallization and/or measuring at high temperatures/pressures. Here we report ...
Tópico(s): Glass properties and applications
2013 - Nature Portfolio | Nature Communications
Ildikó Pethes, V. Nazabal, Radwan Chahal, Bruno Bureau, I. Kaban, B. Beuneu, Jozef Bednarčík, P. Jóvári,
The structure of Ge22Ga3Sb10S65 and Ge15Ga10Sb10S65 glasses was investigated by neutron diffraction (ND), X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) measurements at the Ge, Ga and Sb K-edges. Experimental data sets were fitted simultaneously in the framework of the reverse Monte Carlo (RMC) simulation technique. Short range order parameters were determined from the obtained large-scale configurations. It was found that the coordination numbers of Ge, Sb and S are around ...
Tópico(s): Crystal Structures and Properties
2018 - Elsevier BV | Journal of Non-Crystalline Solids
Jun Han, N. Mattern, I. Kaban, D. Holland‐Moritz, Jozef Bednarčík, R. Nowak, N. Sobczak, Dahee Kim, J. Eckert,
The phase equilibria and the solidification behavior of ternary Co–Gd–Ti (Co ≤35 at.%) alloys have been investigated. The phase transformation and equilibria in the liquid phase were studied in situ for two alloys, Co30Gd35Ti35 and Co30Gd50Ti20, by combining electrostatic levitation of the samples with high-energy synchrotron x-ray diffraction (XRD) at elevated temperature. The XRD patterns with two diffuse maxima for molten Co30Gd35Ti35 give direct evidence for liquid–liquid phase separation in this ...
Tópico(s): Solidification and crystal growth phenomena
2013 - IOP Publishing | Journal of Physics Condensed Matter
I. Kaban, P. Jóvári, Anja Waske, M. Stoica, Jozef Bednarčík, B. Beuneu, N. Mattern, J. Eckert,
The short-range atomic order of ternary Fe–Nb–B metallic glasses has been studied by X-ray diffraction, neutron diffraction, X-ray absorption spectroscopy, and reverse Monte-Carlo simulation. The similarities and differences in the local structure of the Fe–Nb–B glasses and their crystalline counterparts are revealed. The composition dependences for the Curie temperature of the Fe–Nb–B glasses, which increases by substitution of boron for iron at constant niobium content and decreases by substitution ...
Tópico(s): Glass properties and applications
2012 - Elsevier BV | Journal of Alloys and Compounds
N. Mattern, Jun Han, Olga Fabrichnaya, M. Zinkevich, W. Löser, J. Werner, R. Nowak, I. Kaban, O. Shuleshova, D. Holland‐Moritz, Jozef Bednarčík, N. Sobczak, J. Eckert,
The phase equilibria of the binary Gd–Ti system were studied by combining electrostatic levitation of the melt with high energy synchrotron in situ X-ray diffraction at elevated temperatures. The coexistence of the phases including the liquid was directly proven in the temperature range between T=1000 and 1920 K. The Gd–Ti system is of monotectic type characterized by a miscibility gap in the liquid state above the monotectic temperature T=1841±5 K. Together with experimental data from thermo-analysis ...
Tópico(s): Metallurgical and Alloy Processes
2013 - Elsevier BV | Calphad
N. Mattern, Jun Han, M. Zinkevich, O. Shuleshova, I. Kaban, D. Holland‐Moritz, J. Gegner, Fan Yang, Jozef Bednarčík, W. Löser, J. Eckert,
The phase equilibria of the binary Gd–Zr system have been investigated by combining electrostatic levitation of the melt with in situ high energy synchrotron X-ray diffraction. The liquidus line was experimentally assessed between 1500 and 1800 K from the diffraction data. At T=1495±10 K the eutectic reaction L↔bcc-Gd+bcc-Zr is evident. The eutectic composition x=18±2 at% Zr is determined from the in situ diffraction data and confirmed by the analysis of the microstructure of cast alloys. The so ...
Tópico(s): Metallic Glasses and Amorphous Alloys
2012 - Elsevier BV | Calphad
P. Jóvári, Pierre Lucas, Zhiyong Yang, Bruno Bureau, I. Kaban, B. Beuneu, Claudia Pantalei, Jozef Bednarčík,
Short range order in glassy 0.9(Ge0.1As0.15Te0.75)–0.1Cu (GATC1) and 0.9(Ge0.05As0.55Te0.4)–0.1Cu (GATC2) was studied by neutron- and X-ray diffraction as well as EXAFS (extended X-ray absorption fine structure) measurements at the K-edges of all components. The reverse Monte Carlo simulation technique was used to create models consistent with all experimental datasets. It was found that Cu binds predominantly to Te in GATC1 while Cu–As and Cu–Cu bonding is also significant in GATC2. Ge and As atoms ...
Tópico(s): Chalcogenide Semiconductor Thin Films
2015 - Elsevier BV | Journal of Non-Crystalline Solids
I. Kaban, K. Khalouk, F. Gasser, J.G. Gasser, Jozef Bednarčík, O. Shuleshova, I.V. Okulov, Thomas Gemming, N. Mattern, J. Eckert,
The temperature dependences of electrical resistivity, absolute thermoelectric power as well as structural changes in Ni36.5Pd36.5P27 metallic glass have been measured and analyzed. A very good agreement between the phase transition temperatures determined using different techniques has been established. In situ measurement of electrical resistivity is suggested as a method to control the phase formation and microstructure upon heat treatment of metallic glasses.
Tópico(s): Glass properties and applications
2014 - Elsevier BV | Journal of Alloys and Compounds
I. Kaban, W. Hoyer, P. Jóvári, T. Petkova, Ani Stoilova, A. Schöps, Jozef Bednarčík, B. Beuneu,
As34Se51Ag15 and As34Te51Ag15 glasses have been studied with high energy X-ray diffraction, neutron diffraction and extended X-ray absorption spectroscopy. The experimental data were modeled simultaneously with the reverse Monte Carlo simulation method. The combination of these independent measurements together with the application of some plausible physical constraints allowed the separation of the partial pair correlation functions and the estimation of the coordination numbers. An analysis of ...
Tópico(s): X-ray Spectroscopy and Fluorescence Analysis
2009 - Springer Nature (Netherlands) | NATO science for peace and security series. B, Physics and biophysics
Amir Hossein Taghvaei, Mihai Stoica, Jozef Bednarčík, I. Kaban, H. Shakur Shahabi, Mohsen Samadi Khoshkhoo, K. Janghorban, J. Eckert,
The influence of ball milling on the atomic structure and magnetic properties of the Co40Fe22Ta8B30 metallic glass with a high thermal stability and excellent soft magnetic properties has been investigated. After 14 h of milling, the obtained powders were found to consist mainly of an amorphous phase and a small fraction of the (Co,Fe)21Ta2B6 nanocrystals. The changes in the reduced pair correlation functions suggest noticeable changes in the atomic structure of the amorphous upon ball milling. Furthermore, ...
Tópico(s): Phase-change materials and chalcogenides
2014 - Elsevier BV | Materials Characterization
J. Orava, Konrad Kosiba, Xiaoliang Han, Ivan Soldatov, Olof Gutowski, Oleh Ivashko, Ann‐Christin Dippel, M. v. Zimmermann, André Rothkirch, Jozef Bednarčík, U. Kühn, H. Siegel, Steffen Ziller, A. J. van der Horst, Karsten Peukert, Ralf Voigtländer, D. Lindackers, I. Kaban,
Details of fast-resistive-heating setups, controlled heating ranging from ∼101 K s−1 to ∼103 K s−1, to study in situ phase transformations (on heating and on cooling) in metallic glasses by high-energy synchrotron x-ray diffraction are discussed. Both setups were designed and custom built at the Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden) and have been implemented at the P02.1 Powder Diffraction and Total Scattering Beamline and the P21.1 Swedish Materials Science ...
Tópico(s): Material Dynamics and Properties
2020 - American Institute of Physics | Review of Scientific Instruments
Kaikai Song, Shuang Wu, I. Kaban, Mihai Stoica, Jozef Bednarčík, J.G. Wang, Delong Yan, G. Wang, J. Eckert,
During the thermally-activated martensitic transformation (MT) of CuZr-based bulk metallic glass (BMG) composites containing B2 CuZr crystals, the MT temperatures were reduced to 162.7 ± 2.5 K due to the constraint effect from glassy matrix, which is far lower than those of crystalline counterparts. In situ high-energy X-ray diffraction measurements demonstrate that the thermally-activated MT is governed by an extremely incomplete MT from B2 to B19' and B33 phases without the decomposition of B2 phase ...
Tópico(s): Consumer Perception and Purchasing Behavior
2019 - RELX Group (Netherlands) | SSRN Electronic Journal
P. Jóvári, A. Piarristeguy, Jean‐Baptiste Vaney, I. Kaban, Andrea Zitolo, B. Beuneu, Jozef Bednarčík, Gaëlle Delaizir, Judith Monnier, A.P. Gonçalves, Christophe Candolfi,
Short range order of As40-xCuxTe60 (x = 0, 10, 20, 25, 30) glasses was studied by neutron- and X-ray diffraction, combined with extended X-ray absorption fine structure (EXAFS) measurements at the K-edges of all components. Large-scale structural models were generated by fitting the experimental datasets simultaneously in the framework of the reverse Monte Carlo simulation technique. These simulations revealed that As and Te atoms bind to about 3 and 2 As/Te neighbors, respectively, both of which possess ...
Tópico(s): X-ray Spectroscopy and Fluorescence Analysis
2017 - Elsevier BV | Journal of Non-Crystalline Solids
Shuai Wei, Fan Yang, Jozef Bednarčík, I. Kaban, Andreas Meyer, Ralf Busch,
Polyamorphic phase transformations are important for understanding and applications of the properties of liquids and glasses. This article reviews the recent studies of polyamorphic transitions and their implications to the properties of metallic liquids and glasses. We discuss the implications of the viscosity hysteresis in a kinetically strong Zr-based viscous liquid and propose an alternative explanation of the anomalous crystallization behavior in the framework of the polyamorphism. We also ...
Tópico(s): Material Dynamics and Properties
2013 - American Institute of Physics | AIP conference proceedings