Formation of ultra- and nanodispersed “core-shell” structures Ti$_{0.8}$Mo$_{0.2}$C$_{0.5}$N$_{0.5}$–Ni–Mo in the process of plasma-chemical synthesis of a mechanical mixture of titanium carbonitride with metallic nickel and molybdenum

Ultradisperse and nanocrystalline powder compositions were obtained in the process of plasmachemical synthesis of a mechanical mixture of titanium carbonitride TiC$_{0.5}$N$_{0.5}$ with metallic nickel and molybdenum in a low-temperature nitrogen plasma (4000 – 6000$^\circ$C), taking into account recondensation in a turbulent flow of nitrogen gas. It was established by X-ray diffraction that their phase composition is characterized by the presence of cubic compounds in the form of titanium-molybdenum carbonitride Ti$_{0.8}$Mo$_{0.2}$C$_{0.5}$N$_{0.5}$, metallic Ni and Mo. High-resolution transmission electron microscopy was used to visualize a “core-shell” structure in the nanocrystalline fraction, which includes such phases as Ti$_{1-n}$Mo$_n$C$_x$N$_y$, Ni, NiO, TiO$_2$, MoC$_{0.5}$N$_{0.5}$. The experimental data on measurements of the specific surface area by the BET method and the pycnomentric density made it possible to determine the calculated values of the average particle sizes which were 365 and 56 nm for the fractions from the cyclone and the filter, respectively. The average particle size of the nanocrystalline component of the fraction from the cyclone, according to the results of direct measurements, was 22 nm. Based on the obtained experimental results, a model for the formation of Ti$_{0.8}$Mo$_{0.2}$C$_{0.5}$N$_{0.5}$–Ni–Mo “core-shell” structures has been developed, which is implemented under the conditions of a turbulent flow of nitrogen gas formed in a quenching chamber of a plasma chemical plant.