STUDY OF THE EFFECT OF TiO<sub>2</sub> NANOADDITIVES ON THE PHYSICAL AND MECHANICAL PROPERTIES, STRUCTURE AND PHASE COMPOSITION OF (BeO + TiO<sub>2</sub>)-CERAMICS
This study presents the results of the influence of the number of TiO2 nanosized particles (0.1-2.0 wt.%) and the firing temperature on the physical and mechanical properties, structure and phase composition of beryllium oxide ceramics of the composition (BeO + TiO2) made from powders of micron size. It is shown that the presence of TiO2 nanoparticles promotes an increase in the density of sintered ceramics. This effect is achieved due to the interpenetration of the BeO - TiO2 phases and an increase in the defectiveness of the structure. The decrease in the activation energy of place exchange processes in the grain boundary zone can be explained by the relationship between diffusion and defects in the lattice structure. Diffusion along the grain boundary occurs faster than in an undisturbed lattice. The presence of nanoparticles also promotes self-healing of micropores, which can be explained by the blocking of a certain fraction of the interfaces between BeO particles by nanoparticles and the creation of a diffusion barrier. Injection of vacancies into the crystal, increases the free energy of the system, makes its growth thermodynamically unfavorable, in a certain range of sizes. As shown in this study, an increase in the sintering temperature of ceramics promotes the transformation of the crystalline structure of TiO2 into a more conductive Ti3O5 with an orthorhombic structure. The onset of an electrically conductive phase is usually accompanied by the absorption of electromagnetic radiation. The synthesized ceramics are relevant for the needs of the radio-electronic industry: microwave electric vacuum devices - EEC, amplifiers, traveling and backward wave tubes, klystrons, klystrodes, gyro devices; solid state microwave devices; microwave modules; integrated microwave products with the use of microwave electronic devices, solid-state discrete devices and microwave modules.