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Vlastnosti nanokrysltalického Zr-Fe-H
Roupcová, Pavla ; Schneeweiss, Oldřich
In this paper, we describe some results obtained by synthesis of Fe-Zr alloys and the study of the phase transformations in these materials induced by hydrogen. Mossbauer spectroscopy was used as the most sensitive method for determination of Fe-Zr based phases in a nanocrystalline form.
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Vliv tepelného zpracování na mechanické vlastnosti slitiny FeNiB
Zábranský, Karel ; Jirásková, Yvonna
An influence of thermal treatment in the temperature range 150 - 350 °C on the structural and mechanical properties of an amorphous FeNiB alloy is investigated. The high tensile strength of 2200 MPa in the as-prepared amorphous state slightly decreases with increasing annealing temperature up to approximately 200 °C in opposite to microhardness where an increase is observed. Above 200 °C a pronounced deterioration of both characteristics is observed which reflects the embrittlement of amorphous structure without any indication of crystallization.
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Porovnání fyzikálních a chemických vlastností slitin Fe80Nb3Cu1B16 a Fe33,5Ni40Nb3Cu1Si13,5B9
Zábranský, Karel
Two FINEMET-type alloys FeNbCuB (F) and FeNiNbCuSiB (FNS) in the as-quenched amorphous, relaxed amorphous and nanocrystalline states have been investigated using Mössbauer spectroscopy, X-ray diffraction, magnetic and electrochemical methods. Present work summarizes the results obtained in the as-quenched and relaxed amorphous states. A partial substitution of Si for B and mainly of Ni for Fe (FNS-alloy) had a pronounced influence on the majority of the physical and chemical properties. A significant decrease in Curie temperature, an increase in crystallization temperature, a decrease in saturation magnetic polarization supported also by a decrease of hyperfine induction were observed.
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Physical and chemical properties of FINEMET-type alloys
Zábranský, Karel
FINEMET-type alloys Fe80Nb3Cu1B16 (FM1), Fe80Nb3Cu1Si6B10 (FM2), and Fe33,5Ni40Nb3Cu1Si13, 5B9 (FM3) are investigated in the amorphous states. The aim of these studies is to follow an influence of variations in metalloid (Si, B) and metal (Fe, Ni) elements on the structural, magnetic, chemical, and mechanical properties.
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Složení a struktura plazmově stříkaných prášků chromové ocele
Schneeweiss, O. ; Voleník, Karel ; Kolman, Blahoslav Jan
Chromium steel powder (13% Cr) was sprayed by a water stabilized plasma gun. The changes of composition and structure occurring during two plasma spraying stages were studied. To characterize the main features of the first (in-flight) stage product, the molten powder particles flying in the plasma stream were trapped and quenched in liquid nitrogen. At the second stage, the particles were allowed to hit a solid substrate and to form a coating. The composition of the feedstock powder and the samples resulting from both plasma spraying stages were determined by chemical methods and X-ray microanalysis. Significant Cr-depletion was due mainly to selective oxidation of chromium at the in-flight stage. At the second stage, the composition changes were less important. Some details of the structure, in particular the distribution of Cr-atoms in the nearest neighbourhood of a Fe-atom, were assessed employing the results of Mössbauer spectroscopy.
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Influence of annealing conditions on Mossbauer spectroscopy parameters of Fe-Zn intermetallic phases
Zmrzlý, Martin ; Schneeweiss, Oldřich ; Houbaert, Y. ; Fiala, J.
The phase composition of galvannealed zinc coatings strongly depends on used annealing conditions. According to equilibrium binary phase diagram of iron and zinc, it is possible to find four intermetallic phases. They arise due to diffusion of zinc and have some certain limits of stability. After dipping into molten zinc the steel sheet proceeds to annealing furnace. Since this is the diffusion controlled and thermodynamically determined process, the composition of coating differs with temperature and time of annealing. Also within the phases themselves there are small but important differences of space arrangement of unit cells, what is clearly observable at Mossbauer spectra parameters ů isomer shifts, quadrupole splittings and relative areas of peaks.
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Preparation of MgO-Ni3Fe nanocrystalline composite from spark eroded powder
Schneeweiss, Oldřich ; Jirásková, Yvonna ; Řepa, P.
Nanocomposites MgO-TM (TM = Ni3Fe, FeCo) were prepared by controlled heat treatment of compacted spark synthesised nanopowders. Main attention was paid to study of influence of interaction with surrounding atmosphere and adsorbed gases on phase composition and magnetic properties. Mössbauer spectroscopy, x-ray diffraction and TEM were used for phase analysis. Changes in structure and phase composition during annealing were detected using thermomagnetic curves and DTA/TG measure-ments and completed with gas analysis using mass spectroscopy.
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