Physical and Chemical Processes of Structure Formation of (BeO+TiO2)-Ceramics with the Addition of TiO2 Nanoparticles

This paper describes in detail the solid-phase sintering mechanism of BeO + + ceramics in the 1520–1550 °C temperature range. It is shown that the structural elements are formed due to the processes of pore disappearance and grain growth in the process of ceramic shrinkage during sintering. It is found that under the influence of TiO2 nanoparticles it is possible to increase the sintering temperature of such ceramics by 30 °C, which promotes the transformation of the crystal structure of TiO2 into a more conductive Ti3O5 with an orthorhombic structure. The mechanism of the slowing down of the grain boundary movement by the second phase impurity as the segregation of nano impurities on the grain boundary is described. The calculation of binding energy of spontaneous chemical reactions during sintering of ceramics is performed, chemical elements and compounds related to conductive phase in ceramics of BeO + + composition at sintering temperature 1550 °С are determined. It is shown that the specific conductivity of the synthesized nanocomposite material increases in comparison with the ceramics consisting of micropowders in the frequency range of 100 Hz–100 MHz, at a sintering temperature of 1550 °С

Processing of industrial waste by plasma-chemical method

In this paper, the results of the processing of magnesium fluoride by plasma-chemical method to obtain periclase and a solution of hydrogen fluoride (hydrofluoric acid) were presented. For the industrial implementation of plasma technologies, it is necessary to study the main parameters of plasma processes for obtaining reducing gases and processing metal oxides with them, to solve the issues of their hardware design, to increase the service life of plasma torches for their use in continuous metallurgical processes. The purpose of this work was to determine the conditions for the plasma-chemical process of processing magnesium fluoride. Thermal analysis of magnesium fluoride on a TGA/DSC2 thermogravimetric analyzer was performed. Thermogravimetric analysis showed that in the temperature range under consideration the process is endothermic, and at a temperature of ~1280°C a phase transition of the 1st kind is observed due to the melting of magnesium fluoride. The fractional composition of MgF2 and MgO powders was studied using the Analysette-22 Nanotech laser diffraction analyzer. The results of the evaluation of the fractional composition of powders have a significant difference. At the same time, the convergence of the data obtained using laser diffraction and electron microscopy methods was found

Formation of TiN coatings by air plasma spraying

Titanium nitride (TiN) coatings were obtained on the surface of 12Kh18N10T steel by air plasma spraying (APS) of TiN powders using an arc plasmatron made by the authors. The plasmatron has a node of circular input and gas-dynamic focusing of the powder and the output apertures of the nozzle-anode are made in the form of rectangular narrowing-expanding channels (No.34334 RK: IPC H05H 1/42). A study of operation modes of a plasmatron for spraying of powder coatings was carried out. The structural-phase state, microhardness and wear resistance of TiN coatings were systematically investigated. The optimum APS operating mode for deposition of TiN powder was determined: current 250 A, voltage 68 V, argon gas flow 34 L/min, spraying distance 150 mm. To reduce the oxidation of TiN powder in the APS process, a method of creating a nitrogen environment at the outlet of the anode nozzle, nitrogen flow rate 2.3 bar was used. The results of structural analysis showed that TiN is the main phase of the coating. The mechanism of formation of TiN structures was characterized by analyzing SEM results of TiN coating surface morphology and TiN droplets sprayed on the surface of the sample. The results showed that the TiN(1) coating has better wear resistance than the TiN(2) and TiN(3) coatings. The cross-sectional and longitudinal microhardness of the TiN coating was investigated. The highest cross-sectional hardness of TiN coating is 1250 HV0.1, which is in accordance with mode 1