Number of found documents: 906
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HYDROGEN STORAGE IN Mg-In-C ALLOYS: EFFECT OF COMPOSITION AND AGEING
Čermák, Jiří; Král, Lubomír
2015 - English
Hydrogen storage in two Mg-In-C alloys with different In concentration, c In , was studied in the temperature range from 250°C to 350°C after five-years-ageing at room temperature. The both alloys show acceptable cycling stability, however, the storage capacity of the alloys decreased from about 5 wt. % H2 to about 2,5 and 3.1 wt. % H 2 by higher c In and lower c In , respectively after 5 years. The sorption kinetics degraded much more by high c In than by c In . PCT isotherms, TPS and DSC patterns were measured for both materials. It was found that the hydrides responsible for hydrogen storage in alloy with higher c In are slightly more stable. Keywords: hydrogen; hydrogen storage; magnesium alloys Available at various institutes of the ASCR
HYDROGEN STORAGE IN Mg-In-C ALLOYS: EFFECT OF COMPOSITION AND AGEING

Hydrogen storage in two Mg-In-C alloys with different In concentration, c In , was studied in the temperature range from 250°C to 350°C after five-years-ageing at room temperature. The both alloys ...

Čermák, Jiří; Král, Lubomír
Ústav fyziky materiálů, 2015

THE EFFECT OF MO AND/OR C ADDITION ON MICROSTRUCTURE AND PROPERTIES OF TIAL ALLOYS
Chlupová, Alice; Kruml, Tomáš; Roupcová, Pavla; Heczko, Milan; Obrtlík, Karel; Beran, Přemysl
2015 - English
Cast TiAl alloys with high Nb content are subject of extensive research with the aim to develop material with low density, good corrosion resistance and high strength at elevated temperatures. Disadvantage of their broad applications is restricted workability, machinability and low fracture toughness especially at room temperature. Improvement of properties of TiAl based materials can be achieved by tailoring the microstructure by modification of chemical composition. For this purpose 5 types of TiAl alloys with 7 % of Nb were prepared having variable content of Mo and/or C. Addition of Mo and/or C resulted in three types of microstructure and different phase composition. All modified alloys contain colonies consisting of thin lamellae of a and g phases sometimes complemented by g and/or b phase at the grain boundaries. Variable microstructure and phase composition resulted in differences in mechanical behaviour. The most promising tensile properties at both room and elevated temperature were observed for alloy doped with 2 % of Mo having the mixed microstructure containing b phase and for alloy doped with 0.5 % of C with nearly lamellar microstructure without b phase. 2Mo alloy exhibited reasonably good ductility while 0.5C alloy reached the highest tensile strength. Also low cycle fatigue behaviour of these two materials was the best of all five materials under investigation. Fatigue deformation characteristics were better in the case of 2Mo alloy while 0.5C alloy exhibited higher cyclic stresses. Fracture mechanisms were determined using fractographic analysis. The major fracture mode of all alloys was trans-lamellar. Keywords: TiAl; microstructure; mechanical properties; effect of alloying; fractography Available at various institutes of the ASCR
THE EFFECT OF MO AND/OR C ADDITION ON MICROSTRUCTURE AND PROPERTIES OF TIAL ALLOYS

Cast TiAl alloys with high Nb content are subject of extensive research with the aim to develop material with low density, good corrosion resistance and high strength at elevated temperatures. ...

Chlupová, Alice; Kruml, Tomáš; Roupcová, Pavla; Heczko, Milan; Obrtlík, Karel; Beran, Přemysl
Ústav fyziky materiálů, 2015

Deposition of Hard Yet Moderately Ductile MoBC Coatings by p-DC Magnetron Sputtering
Souček, P.; Buršíková, V.; Zábranský, L.; Buršík, Jiří; Vašina, P.
2015 - English
Novel nanolaminated MoBC coatings were prepared using a combination of non-reactive direct current and pulsed direct current magnetron sputtering. Depending on the deposition conditions the coatings were either of amorphous or of nanocomposite nature. Nanocomposite coatings showed good hardness and Young’s modulus and showed no tendency to form cracks even for high-load nanoindentation testing. Keywords: magnetron sputtering; ion flux; nanolaminates Available at various institutes of the ASCR
Deposition of Hard Yet Moderately Ductile MoBC Coatings by p-DC Magnetron Sputtering

Novel nanolaminated MoBC coatings were prepared using a combination of non-reactive direct current and pulsed direct current magnetron sputtering. Depending on the deposition conditions the coatings ...

Souček, P.; Buršíková, V.; Zábranský, L.; Buršík, Jiří; Vašina, P.
Ústav fyziky materiálů, 2015

Chemical Wet Synthesis and Characterization of Copper-Silver Nanoparticles
Zobač, O.; Sopoušek, J.; Vykoukal, V.; Buršík, Jiří; Roupcová, Pavla
2015 - English
AgCu nanoparticles (NPs) of near-eutectic composition were prepared by various route of wet synthesis. Nanoparticles suspended in nonpolar solvents were synthesized by solvothermal synthesis from metalloorganic precursors. AgCu colloids in aqueous solution were obtained by the hydride reduction of Ag and Cu nitrates under action of different stabilization agents. Chemical characterizations of as-synthesized AgCu NPs were done using inductively-coupled plasma-optical emission spectrometry (ICP-OES). The optical properties of nanoparticles were monitored using UV-Vis spectrophotometer. The size of colloid nanoparticles were measured by both dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) method in some extra cases. Keywords: nanoalloy; Ag-Cu; phase transformation Available at various institutes of the ASCR
Chemical Wet Synthesis and Characterization of Copper-Silver Nanoparticles

AgCu nanoparticles (NPs) of near-eutectic composition were prepared by various route of wet synthesis. Nanoparticles suspended in nonpolar solvents were synthesized by solvothermal synthesis from ...

Zobač, O.; Sopoušek, J.; Vykoukal, V.; Buršík, Jiří; Roupcová, Pavla
Ústav fyziky materiálů, 2015

THE EFFECTS OF HIGH TEMPERATURE HELIUM GAS ON THE FRACTURE BEHAVIOUR OF ODS MA957
Rozumová, L.; Hojná, A.; Kalivodová, J.; Bublíková, P.; Hadraba, Hynek; Di Gabriele, F.
2015 - English
Oxide-dispersion-strengthened steel (ODS) MA957 has been studied as a candidate material for Tritium Breeding Blanket for fusion reactors with helium coolant, where temperatures 250-650 degrees C are expected. Helium is one of type as primary coolant in High Temperature Reactor and Gas Cooled Fast Reactor with working temperature 500-1000 degrees C. \n\nThis work presents results of the study of behaviour of ODS (MA957) under influence of high temperature helium environment. Microstructure of the material and the interaction with He was investigated. The average exposure temperature was held at 720 degrees C. Subsequently, the surface changes were determined. Impact testing and material surfaces were studied in detail by means of SEM and TEM microscopy. It is essential to understand the He effect on microstructure and mechanical properties of structural materials since the He embrittlement in TBB may be significant. Keywords: ODS; MA957; Helium Available at various institutes of the ASCR
THE EFFECTS OF HIGH TEMPERATURE HELIUM GAS ON THE FRACTURE BEHAVIOUR OF ODS MA957

Oxide-dispersion-strengthened steel (ODS) MA957 has been studied as a candidate material for Tritium Breeding Blanket for fusion reactors with helium coolant, where temperatures 250-650 degrees C are ...

Rozumová, L.; Hojná, A.; Kalivodová, J.; Bublíková, P.; Hadraba, Hynek; Di Gabriele, F.
Ústav fyziky materiálů, 2015

Analysis of the surface layer of the brake disk
Švábenská, Eva; Roupcová, Pavla; Podstranská, Ivana; Petr, M.; Filip, J.; Schneeweiss, Oldřich
2015 - English
Our research is focused on the changes in thin surface layer of the brake disk due to the impact of severe plastic deformation and heating by friction process. The aim of this study is to compare structure, chemical and phase compositions of the surface layer in depth up to several hundreds of nanometers in the no affected central part of brake disk and the part which was in contact with brake pads by braking. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-Ray Powder Diffraction and Mössbauer Spectroscopy. The thin surface layer was studied using Conversion Electron Mössbauer Spectroscopy and X-ray Photoelectron Spectroscopy. We explain the observed changes with the knowledge on effects of plastic deformation and/or diffusion of alloying elements in the material of the brake disk. Keywords: grey cast iron; brake disk; microstructure analysis; surface layer Available at various institutes of the ASCR
Analysis of the surface layer of the brake disk

Our research is focused on the changes in thin surface layer of the brake disk due to the impact of severe plastic deformation and heating by friction process. The aim of this study is to compare ...

Švábenská, Eva; Roupcová, Pavla; Podstranská, Ivana; Petr, M.; Filip, J.; Schneeweiss, Oldřich
Ústav fyziky materiálů, 2015

ATOMISTIC SIMULATIONS OF TWIN BOUNDARIES FACETING IN HCP MATERIALS
Ostapovets, Andriy
2015 - English
Deformation twinning is frequently observed in materials with hexagonal crystal lattice. It plays important role in plastic deformation of such materials. Twin regions have often lamellar shape and twin boundaries are usually oriented along invariant planes. However, non-invariant plane twin interfaces are also observed. Occurrence of such interfaces can be connected with interactions between twinning disconnections. Mechanisms of such interactions are discussed on the basis of atomistic simulations. Keywords: Twin boundaries; hcp; EAM potential Available at various institutes of the ASCR
ATOMISTIC SIMULATIONS OF TWIN BOUNDARIES FACETING IN HCP MATERIALS

Deformation twinning is frequently observed in materials with hexagonal crystal lattice. It plays important role in plastic deformation of such materials. Twin regions have often lamellar shape and ...

Ostapovets, Andriy
Ústav fyziky materiálů, 2015

THE INFLUENCE OF CONSOLIDATION PROCEDURE PARAMETERS ON COMPACTION OF AL POWDER
Lowe, T. C.; Kunčická, L.; Kocich, R.; Davis, C. F.; Hlaváč, L.; Dvořák, Jiří
2015 - English
The influence of different consolidation procedures on compaction of Al powders was evaluated. Powder preparation procedures consisted of selection of particle size distribution, cold isostatic pressing (CIP), and vacuum sintering. Processing parameters investigated included the number of compression steps, compression pressure, and sintering temperature and time. Densities of the samples after compression and also after sintering were measured and compared. The overall oxygen content was analysed using by Energy Dispersive Spectroscopy. Phase composition was determined using X-ray. Microhardness measurements were performed to evaluate the degree of compaction. Double-step CIP at 200+300 MPa and subsequent sintering at 500°C for 60 min produced the best combination of properties from all the consolidation technologies of Al particles. Of the particle size ranges studies, those with diameters between 20 and 45 μm produced the best results. Aluminum oxide was present in the structure after all the processing treatments. Keywords: Aluminum powder; cold isostatic pressing; sintering; oxygen content; X-ray Available at various institutes of the ASCR
THE INFLUENCE OF CONSOLIDATION PROCEDURE PARAMETERS ON COMPACTION OF AL POWDER

The influence of different consolidation procedures on compaction of Al powders was evaluated. Powder preparation procedures consisted of selection of particle size distribution, cold isostatic ...

Lowe, T. C.; Kunčická, L.; Kocich, R.; Davis, C. F.; Hlaváč, L.; Dvořák, Jiří
Ústav fyziky materiálů, 2015

Ab initio calculations of temperature dependent resistivity for transition metals
Wagenknecht, D.; Turek, Ilja; Carva, K.
2015 - English
The effect of phonons on electrical resistivity has been simulated by considering random displacements of atomic nuclei from their equilibrium positions together with a frozen-potential approach. The developed theory has been applied successfully to late transition metals (Fe, Ni, Rh, Pd, Pt). Keywords: electrical resistivity; temperature dependence; transition metals Available at various institutes of the ASCR
Ab initio calculations of temperature dependent resistivity for transition metals

The effect of phonons on electrical resistivity has been simulated by considering random displacements of atomic nuclei from their equilibrium positions together with a frozen-potential approach. The ...

Wagenknecht, D.; Turek, Ilja; Carva, K.
Ústav fyziky materiálů, 2015

MODIFIKOVANÁ ZKOUŠKA EXCENTRICKÝM TAHEM: VYHODNOCENÍ EXPERIMENTÁLNÍCH TESTŮ VÁLCOVÝCH TĚLES Z CEMENTOVÉHO KOMPOZITU
Holušová, T.; Lozano, M.; Komárková, T.; Kocáb, D.; Seitl, Stanislav
2015 - Czech
Modifikovaná zkouška excentrickým tahem (MCT) by mohla v budoucnu představovat stabilní zkoušku pro vyhodnocování lomově-mechanických parametrů nebo také únavového chování kompozitních materiálů jako je beton. Těleso pro MCT zkoušku s kruhovým průměrem může být snadno odebráno z jádrového vývrtu se zvolenou tloušťkou a velikostí průměru. Tato práce je zaměřena na vyhodnocení lomového chování MCT těles při statickém zatěžování a porovnání dvou různých uchycení do čelistí testovacího zařízení. Výsledky jsou prezentovány formou L-COD zatěžovacích digramů, tj. závislosti zatížení (L) měřeného v ose ocelových tyčí na velikosti otevření trhliny (COD). The modified compact tension test (MCT) might be in the future a stable test configuration for the evaluation of fracture-mechanics parameter or also a fatigue behavior of the composites materials such the concrete is. Core drilling can be employed to obtain specimens which are cylindrical in shape with the chosen thickness. This contribution focuses on the evaluation of MCT specimen fracture behavior during static tests and the comparison of two different fixing system of the test machine. The results are represented as L-COD diagrams (i.e. load vs. crack opening displacement measured on the loading axis. Keywords: Modified compact tension test; fracture parameters; composites; ARAMIS; L-COD Available at various institutes of the ASCR
MODIFIKOVANÁ ZKOUŠKA EXCENTRICKÝM TAHEM: VYHODNOCENÍ EXPERIMENTÁLNÍCH TESTŮ VÁLCOVÝCH TĚLES Z CEMENTOVÉHO KOMPOZITU

Modifikovaná zkouška excentrickým tahem (MCT) by mohla v budoucnu představovat stabilní zkoušku pro vyhodnocování lomově-mechanických parametrů nebo také únavového chování kompozitních materiálů jako ...

Holušová, T.; Lozano, M.; Komárková, T.; Kocáb, D.; Seitl, Stanislav
Ústav fyziky materiálů, 2015

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