Solid State Phenomena Vols. 203-204

Abstract: In the present paper magnetic and elastic properties of the Ni+SrFe12O19 nanocomposites were examined in detail. Samples were in two forms: i) mechanically pressed cylindrical pellets and ii) filled polymer (amine-epoxy resin) coating on aluminum substrate. The so called apparent Young’s modulus was determined by measurements of the free flexural vibrations frequency by means of vibrating reed technique. Magnetic research was carried out using VSM magnetometer. It was shown that replacement of SrFe12O19 with nano Ni powder results in an increase in material resistivity to elastic deformation. The influence of size reduction of SrFe12O19 powder particles on magnetic parameters of the studied nanocomposites were discussed in detail.

Abstract: This study presents the results of an analysis of the domain structure of supersaturated X2CoCrMoAl20-15-3 maraging steel. The analyses was carried out using the magnetic force microscopy method in a two pass mode. Obtained magnetic results were subjected to numerical analysis. The dimensions of spontaneously magnetized regions and their orientation were determined by analyzing the autocorrelation function of changes in the resonant frequency of the MFM probe. The use of fractal analysis was proposed to describe the domain structure.

Abstract: The aim of this study was to analyze the influence of the method of preparing the substrates in the form of simple oxides for the structure of the final Bi₅Ti₃FeO₁₅ ceramics. Milling of the substrates was carried out by two methods: the classical one by hand mixing in a porcelain mortar, and by high-energy. Structure studies were performed by the X-ray diffraction (XRD) method. XRD patterns were analyzed with the Rietveld method using the DBWS 9807a program. It was found out that the slightest deviation of the network parameters from the catalog data occurs for the sample obtained from simple oxides by free sintering (BTFs). Furthermore, it was also determined that the optimal high-energy time of the substrates is 5 hours. When compared to the ICDD catalog data, the resulting ceramics is a single phase one and has the lowest network parameters deviation among all samples which were subject to high-energy.

Abstract: Results of morphology and electrical properties evaluation of Y2O3 powders were presented in this article. The tests were made on the two different types of powders. First of them was a powder of the "microsize" type with the particle sizes not crossing10 µm, however the size of particles of the second powder was located in range 30 - 50 nm. Totally different was a morphology of both powders as well. In the first case the form of dense polyhedrons about the smooth surface was observed. However the powder of the type nano was characterized by spongy conglomeration of nano particles type of morphology. The range of investigations included the evaluation of the phase composition of powders (X-ray and electrons diffraction), characteristics of their morphology (SEM, STEM) and evaluation of electric properties by impedance spectroscopy. The obtained results showed that nano powders of oxide Y2O3 is different in the morphology of individual particles, but he is also better ionic conductor in the temperature of 20°C comparing to powder the micro type.

Abstract: The article presents the first attempt to CVD-aluminise alloys based on an intermetallic phase Ti48Al2Cr2Nb. Moreover, it includes initial results of producing VPA-deposited aluminide coating in industrial environment. Microstructure and phase analyses of the obtained coatings have been conducted. The chemical and phase composition analyses have revealed that the CVD-deposited coating was roughly 8 m thick, and composed of aluminium-rich TiAl phase, whereas the application of VPA method results in a coating which is approximately 18 m thick and consists of three layers made up of TiAl3, TiAl2 i TiAl phases. Both deposition processes were conducted with industrial equipment.

Abstract: Metamict minerals contain radioactive elements that degrade their crystal structure. During the annealing process under ambient pressure in argon atmosphere the sample of metamict rinkite recrystallizes to the primary crystalline form at 700°C. Further heating leads to the formation of a new crystalline phase.

Abstract: The NiTi alloy (50.6 at.% Ni) passivated for 30 min at 130°C by autoclaving has been studied towards corrosion resistance in aqueous solutions of 3% NaCl, 0.1 M H₂SO₄, 1 M H₂SO₄ and HBSS. Structure and thickness of the passive layer (TiO2, rutile) were examined by X-ray reflectivity method and high resolution electron microscopy. Corrosion behavior of this oxide layer was investigated by open circuit potential method and polarization curves. It was found that the corrosion resistance of the passivated NiTi alloy is strongly dependent on the type of corrosive environment. The higher corrosion resistance of the tested samples was revealed in sulfate solutions as compared to chloride ones. The highest resistance to electrochemical corrosion of the NiTi alloy was observed in 0.1 M H2SO4 solution. Susceptibility to pitting corrosion of the tested samples was observed which increased with the concentration rise of chlorine anions in solution. Electrochemical tests for 316L stainless steel carried out under the same experimental conditions revealed a weaker corrosion resistance in all solutions as compared to the highly corrosion resistant NiTi alloy.

Abstract: Ni-rich alloy (50.8at.%Ni) was plastically deformed by compression combined with reversion oscillating torsion. The compression rate was 0.05 mm/s and the torsion frequency and angle were 1,5Hz and ±3°. After the deformation process the specimens were annealed at 350°C/1h (623K/1h) and 400°C/1h (673K/1h). Their structure and transformation characteristic were studied with the use of TEM, X-ray phase analysis and DSC measurements. TEM observation of specimens after annealing at 350°C/1h (623K/1h) indicate presence of highly deformed B2 phase. In the specimen annealed at 400°C/1h (673K/1h) additionally Ni4Ti3 precipitates and the R-phase in the B2 matrix was found. DSC measurements show that the transformation sequence changes for the deformed and then annealed samples from single step B2  B19’ transformation to the B2  R  B19’ on cooling. Also increase of R-phase transformation temperature TR with the decrease of annealing temperature was observed.

Abstract: In this work, the Mössbauer spectroscopy employed in a study of point defect formation in intermetallic phases of the B2 structure from the Fe-Al system as a function of Al concentration. We present the values of the 57Fe isomer shift and quadruple splitting for the components describing the point defect in the local environment of a Mössbauer nuclide. The concentration of the Fe vacancies and Fe atoms substituting Al (Fe-AS) are determined. The results shown that an increase in Al content causes an increase in vacancy and Fe-AS concentration.

Abstract: During molecular beam epitaxy regular oscillations of the intensity of the specularly reflected beam often occur. The phenomenon of such oscillations is still theoretically explained only partially. For example it is not clear why usually the oscillation phase depends strongly on the glancing angle of the incident beam. However, quite recently interesting results were shown in the literature on the features of RHEED oscillations observed during the growth of Ge layers. The phase of oscillations practically stays constant for a wide range of angles. So in this paper, we show results of RHEED dynamical calculations for Ge. They are presented together with results of calculations for GaAs to make analysis executed more complete. It is concluded that experimental findings for Ge for off-symmetry azimuths can be explained using dynamical diffraction theory employing the proportional model (for which the scattering potential of the layer is determined as the potential of the completed layer multiplied by the coverage).