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The TiN–20% TiB2 and TiN–20% Si3N4 nanocomposites sintered in a microwave field with a frequency of 2.45 GHz were applied to a steel substrate by electrospark deposition in the temperature range 1400–1500°C in a nitrogen atmosphere. In deposition modes with an energy of isolated pulses ranging from 0.2 to 0.75 J, changed surface layers consisting of a coating 50–90 μm thick and a heat-affected zone of increased hardness 40–60 μm thick on the substrate were produced. A part of the samples was subjected to additional surface laser processing to increase the density and homogeneity of the deposited layers. Substantial influence of electrospark mass transfer on the phase composition of the transferred material was established. According to XRD data, the TiN–TiB2 composite, with all its components being present in the coating, was more stable. In the case of the TiN–Si3N4 composite, silicon nitride completely dissociated to form Ti5Si3 and Ti2N compounds. For both compositions, iron, penetrating into the coating from the substrate, was found in the deposited layer. The TiN–TiB2 and TiN–Si3N4 coatings had a hardness of 14–15 GPa and 11–12 GPa, respectively. Comparative tribotechnical tests of the coatings with a spherical VK6 hardmetal counterface in quasistatic and dynamic modes revealed that the electrospark deposition of the TiN–TiB2 composite combined with subsequent laser processing was highly efficient. In tribotechnical tests, the linear wear of this coating was 0.5 μm, corresponding to a twelvefold increase in the wear resistance as compared to that of the TiN–Si3N4 coating for dynamic friction tests. The deposition of the TiN–Si3N4 composite enabled a double increase in the wear resistance of the substrate in dynamic testing mode. In this case, additional laser processing of the coating turned out to be inefficient. [ABSTRACT FROM AUTHOR]

The application of materials with a perovskite structure has currently become one of the most promising approaches for the development of photovoltaic systems. A method for high-speed synthesis (under 15 minutes) of CaTiO3 perovskite — TiO2 rutile with the possibility of concurrent doping of the product has been developed. The density of electronic states, phase composition features, and resistivity of niobium-doped perovskite (CaTiO3 ) were investigated. The calculations of the density of electronic states for niobium-doped CaTiO3 have shown that at low concentrations of niobium, the samples exhibit conductivity characteristic of semiconductors. Since niobium has one more valence electron compared to titanium, as the niobium content increases, the Fermi level shifts to the band of free states. This shift of the Fermi level should lead to a change in the nature of the conductivity of doped crystals, eventually transitioning to metallic conductivity at high concentrations of niobium. Composite analysis (CaTiO3 + ТіО2 ) by X-ray diffraction has shown that the use of niobium as a doping element significantly accelerates the CaTiO3 synthesis reaction, and increases the perovskite concentration in the sample. The concentration of CaTiO3 in the sample the with niobium is 83% vol. at a temperature of 900 ºC and a synthesis time of 5 min, whereas when using a mixture without Nb, the content of perovskite will be only 58% vol. at a synthesis time of 12 min. X-ray phase analysis methods confirm the formation of a solid solution (doping) Ca (Ti,Nb)O3, resulting in the preparation of samples (CaTiO3 + ТіО2 ) with resistivity inherent to semiconductors. [ABSTRACT FROM AUTHOR]