The magnetic characteristics of iron oxide nanopowder (Fe
3
O
4
base phase) produced by electroerosion dispersion and consolidated at high pressures (2 GPa) and high temperatures (900, 1000, 1100, ...1200, and 1300°C) for 0.07 h in contact with hexagonal boron nitride were studied. The nanopowder was produced by dispersing iron granules or shavings in plasma induced at contact points between the granules when electric pulses of high current and voltage were passed through them. The metal granules being dispersed are in a constantly circulating liquid (water) atmosphere, creating a pseudo-boiling layer from the granules. The liquid (water in this case) cools the granules to prevent them from being welded and oxidizes the metal vapors that emerge in plasma, forming nanosized iron oxide grains carried by the liquid flow into sedimentation tanks (powders with different grain sizes sediment in different tanks). Room-temperature studies of the magnetic characteristics of samples consolidated from iron oxide powders showed that the materials sintered at 1200 and 1300°C were soft magnetics with virtually zero hysteresis. Their specific magnetic moments at 5000 Oe were 128.4 and 126.4 emu/g and the coercive force was negligibly small: 5.1 and 4.5 Oe. The materials sintered at 1100°C were characterized by a specific magnetic moment of 90.4 emu/g and a relatively low coercive force of 9.1 Oe. The specific magnetic moments of the samples sintered at 900 and 1000°C were significantly lower and the coercive force higher: 40.2 and 42.1 emu/g and 37.9 and 32.4 Oe, respectively. X-ray diffraction with Rietveld refinement revealed that the materials consolidated at 900 and 1000°C contained 75–80 wt.% FeO and 25–20 wt.% Fe, while the materials sintered at 1100°C contained, along with 32 wt.% FeO and 2 wt.% Fe, a significant amount of Fe
3
N (66 wt.%). The materials consolidated at 1200–1300°C contained 100% Fe
3
N phase. Hence, under high pressures and increasing sintering temperatures, iron oxides are reduced and then iron is nitrided with nitrogen released from boron nitride, which improves the soft magnetic characteristics of the sintered materials.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The hydride powder technique was employed to produce intermetallic TiAl alloys using a mixture of Al and TiH
2
powders. The features peculiar to the consolidation and phase formation in different ...temperature/kinetic sintering conditions were studied. To impart the required density to TiAl, two methods of refining the initial mixture were employed: (i) high-energy grinding of the components to provide superfine TiH
2
and Al particles and (ii) use of Al
3
Ti compounds, easily refined because of extraordinary brittleness, as precursors. In the former method, the phase formation processes are accelerated by the refined powders and positive hydrogen effect. At all sintering temperatures (900–1200°C), intermetallic TiAl with an addition of Ti
3
Al is formed after holding for 2–3 h. The material is hardly compacted because of a significant difference in diffusion rates in the Ti–Al system, resulting in the expansion of samples according to the Kirkendall–Frenkel mechanism in the sintering process. In the latter method, the fine TiAl
3
powder, as the starting component, improves the consolidation since the synthesis of Al
3
Ti proceeds as an individual process operation. In this case, in optimal sintering modes, the samples have a relatively low porosity of ~10% and a small grain size of 10–20 μm. Mechanical tests demonstrated that the strength and ductility were sensitive to variation in the porosity and grain size. In the best structural states, the powder material produced with the latter method shows the maximum bending strength (σ
b
~ 550 MPa) and the highest compressive strength (σ
c
= 1700–1600 MPa) and ductility (δ ~ 20%).
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•Electronic structure of tetragonal Tl3PbBr5 is calculated by the FP-LAPW method.•The valence band is dominated by contributions of Br 4p states.•Contributions of Pb 6p* states ...dominate at the bottom of the conduction band.•The high-temperature tetragonal phase of Tl3PbBr5 is an indirect-gap material.•XPS core-level and valence-band spectra of tetragonal Tl3PbBr5 are measured.
We report on calculations of total and partial densities of states of atoms constituting the high-temperature (HT) tetragonal Tl3PbBr5 phase (space group P41) using the full potential linearized augmented plane wave (FP-LAPW) method. Our theoretical data reveal that the tetragonal HT-Tl3PbBr5 phase is an indirect-gap material with band gap of 2.26eV. In addition, the FP-LAPW calculations render that dominant contributors in the valence-band region of HT-Tl3PbBr5 are the Br 4p-like states, which contribute mainly into the top and the central portion of the valence band with also significant contributions throughout the whole valence-band region. The main contributors to the bottom of the valence band of the HT-Tl3PbBr5 phase are the Tl 6s-like states, whilst the unoccupied Pb 6p-like states dominate at the bottom of the conduction band. The X-ray photoelectron core-level and valence-band spectra for the HT-Tl3PbBr5 phase have been measured and compared with those of previously studied the low-temperature orthorhombic Tl3PbBr5 phase.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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•The treatment in microbreaker is used to combine the properties of nanosized Al2O3 and SiO2.•It was first established that the result of SVT there is a redistribution of valence Sisd ...and Alsd electrons in Opπ states.•Changes in electronic structure and structural, morphological features explains increasing the charge capacity of lithium sources of current at cycling.•The relationship between the distribution of electrons and the electrochemical characteristics of the lithium current sources is established.
This paper highlights the relationship between changes in the electrochemical properties vs grinding duration of mixed nanosilica and nanoalumina powders. The dependence of the electrochemical characteristics on structural and morphological changes in the nanocomposite powder has been elucidated. A study of the electrochemical characteristics was performed in galvanostatic and potentiodynamic modes. Scanning electron spectroscopy (SEM), X-ray diffraction analysis (XRD) and ultra-soft X-ray emission spectroscopy (USXES) were used to determine the grinding duration effect on the structural and morphological characteristics. It have been found that as a result of increasing duration processing, the composite is compacted due to O-Opπ-interaction between surface atoms of nanoparticles. From the results of electrochemical studies, it has been found that the changes in specific structural features lead to changes in the discharge capacities of lithium power sources. Namely, an increase in grinding time to 5 min leads to increase in charge capacity of first cycle and capacity after 50 cycles. However, with increasing grinding duration to 10, 15 and 20 min is accompanied by a decrease in the charge state of oxygen, specific surface area and increasing of coherent region scattering that lead to a decrease in the discharge capacity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The process of producing alloys with elements that are uniformly distributed throughout an ingot is described. The structural features of NiCrAlY alloys produced by electron-beam melting, excluding ...primary vacuum induction melting of the starting mixture, were studied. The MZP6 and MZP7 alloys, differing in aluminum content, were examined. The cast material produced from the MZP7 alloy contained the γ phase: a standard solid solution of chromium and aluminum in nickel. The β-NiAl phase was found to be the main phase in the MZP6 alloy. Chain and globular precipitates characteristic of the γ′ phase and a small number of α-Cr-based compounds of variable composition were identified as well. The γ′ phase was detected in the NiCrAlY alloys containing more than 5 wt.% Al. Standard microstructures of the cast ingots produced from the MZP7 and MZP6 alloys indicated that the structural elements refined when the aluminum content increased from 4–6 wt.% (MZP7) to 11–14 wt.% (MZP6), the amounts of nickel, chromium, and yttrium being equal. The MZP7 alloy was characterized by a smooth transition from a fine-grained structure in the areas adjacent to the cooled mold surfaces to a coarse-grained one, formed in the central ingot regions. This phenomenon was less pronounced for the MZP6 alloy ingots. The lattice parameters of the NiCrAlY alloys were determined with the Rietveld refinement of the X-ray diffraction patterns. Maps showing the distribution of elements in the NiCrAlY alloy were provided.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Thermally-activated phase transitions in Pt/Mn/Fe thin films were investigated by a combination of x-ray diffraction, transmission electron microscopy, secondary neutral mass spectrometry depth ...profiling, atomic force microscopy, and magnetic properties measurements. Post-annealing was carried out in vacuum to different temperatures up to 620 °C. Initially, at temperatures between 280 °C-450 °C first L10-MnPt is formed at the Mn/Pt interface followed by the most likely formation of metastable bcc Fe3Pt, which gets transformed by further annealing to fcc Fe3Pt and eventually to chemically ordered L12-Fe3Pt. The final product after annealing at 620 °C consists of two interesting phases, which are relevant for spintronic applications, antiferromagnetic L10-MnPt with addition of Fe and ferromagnetic L12-Fe3Pt, consistent with the initial element composition.
The corrosive effect of the slag-forming mixture (SFM) of a crystallizer on monoclinic zirconium dioxide partially stabilized by calcium oxide or yttrium oxide was studied. It was experimentally ...established that zirconium dioxide stabilized with yttrium oxide had better corrosion resistance due to the low decomposition rate of the stable phase ZrO
2
–Y
2
O
3
when exposed to SFM of the same composition.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We study the heat resistance and electric conductivity of the specimens of Crofer 22 APU steel, which is traditionally used for the production of interconnects of solid-oxide fuel cells, a bulk ...composite based on the Ti
2
AlC MAX phase, and a vacuum-arc coating of the Ti–Al–C system on a thin (0.5 mm) VT1-0 titanium sheet in the intact state and after long-term holding (1000 h) in air at 600°. We study the evolution of the phase compositions of the composite and the coating in the course of long-term holding in oxidizing media and the changes in the oxidation resistance and electric conductivity observed in the course of this evolution. It is shown that thin (0.5 mm) titanium interconnects with the indicated coating may serve as an efficient alternative to the interconnects made of the Crofer-type steel, which enables us to avoid the negative influence of chromium on the serviceability of solid-oxide fuel cells and significantly (by ~ 50%) decrease the weight of batteries of these cells.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The phase formation and consolidation processes in TiH
2
–Ni powder mixtures resulting in TiNi intermetallic were studied. The use of titanium hydride as a precursor in optimal sintering conditions ...(900–1000°C) allowed a material with optimum porosity to be produced and a liquid phase to be avoided during sintering. The phase formation processes were found to occur rapidly in the sintering of TiH
2
–Ni mixtures. At sintering temperatures of 900–1000°C, 70–82% TiNi formed. Intermetallic Ti
2
Ni compound was an additional phase that emerged in the material in all sintering conditions. The stability of this phase was attributed to its affinity for oxygen and thus formation of stable complex oxides. The superfine mixture and highly active titanium resulting from the decomposition of titanium hydride accelerated the oxidation process. Moreover, the interaction with oxygen began sooner than with nickel. The samples produced from the finest mixture were less homogeneous than the samples produced from a coarser mixture. The high-speed interaction between titanium and nickel and rapid oxygen absorption were due to the hydride powder with significantly finer particles. In these sintering conditions, the material had 12–15% porosity and was thus optimum for medical applications. Studies of the mechanical behavior of TiNi alloys revealed an abnormally low elastic modulus of 40 GPa. Experiments on cyclic loading–unloading showed that the initial elastic strain was 1.1% and reversible transformation strain 0.7%. When the strain reached 4%, the elastic modulus decreased to E ~ 32.7 GPa, the total elastic strain increased to ε
el
~ 2.6%, and damping capability Q
–1
became equal to 0.036. The mechanical characteristics of the materials were close to those of human bones. The experimental results demonstrate that the sintered TiN materials exhibit the structure and mechanical properties that make them promising for the design of human bone implants.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The ZrNi
1.2
Mn
0.5
Cr
0.2
V
0.1
alloy was qualified using isotherms of hydrogen desorption in a gas atmosphere, equilibrium curves of hydrogen desorption in a 30% KOH solution, and X-ray diffraction ...data. The equilibrium pressure of the ZrNi
1.2
Mn
0.5
Cr
0.2
V
0.1
alloy in a gas atmosphere at 20°C that was equal to ~1 atm (101,325 Pa) indicated that the alloy could be used in Ni–MH batteries, and the equilibrium hydrogen desorption curve obtained by the electrochemical method indicated that insignificant self-discharge could occur. The alloy samples crystallized at different cooling rates showed different quantitative phase composition. Electrodes produced from the sample with a greater amount of the Zr
7
Ni
10
phase activated faster and those with a greater amount of the C15 and C14 phases had higher maximum discharge capacity. After the electrodes were exposed to air for 14 days, the Zr
7
Ni
10
phase decreased by 7 vol.% and the total content of the C15 and C14 phases increased by 7 vol.% in the sample with a greater amount of the Zr
7
Ni
10
phase (~ 24 vol.%). No changes in quantitative phase composition were found in the sample with a smaller amount of the Zr
7
Ni
10
phase (~12 vol.%). Electrodes prepared from the sample with a lower content of the Zr
7
Ni
10
phase showed better cyclic stability both before and after a pause in the cycles. The loss of the maximum achieved discharge capacity of these electrodes for 100 cycles with a pause in the cycles for 14 days (after the 80
th
cycle) and for 200 cycles with a pause in the cycles for 45 days (after the 150
th
cycle) was only 2 and 16%, and that of the electrodes with a higher content of the Zr
7
Ni
10
phase was 30 and 52%. Thus, the electrodes produced from the alloy sample that showed stable quantitative phase composition according to X-ray diffraction had better hydrogenation–dehydrogenation cyclic stability when exposed to air in powder form for 14 days. Taking into account some similarities in hydrogenation-dehydrogenation and exposure to air of the zirconium alloys (oxidation of alloy components, significant increase in nickel surface concentration, etc.), the better cyclic stability of the electrodes was logically assumed to be due to more stable quantitative phase composition of the surface. The relationship between the electrochemical properties of the ZrNi
1.2
Mn
0.5
Cr
0.2
V
0.1
alloy and the cooling rate in crystallization (quantitative phase composition) allows the development of materials with predicted functional properties.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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