The electromagnetic characteristics, particularly the real εr′ and imaginary εr″ parts of the dielectric constant, of new AlN-based composites with additions of powdered diamond, soot, and diamond with 3–5 wt.

The study is devoted to the electrodynamic properties of composite materials based on AlN–5 wt

The new composite materials with a high level of dielectric constant were created on the AlN-based. These materials were obtained by the hot pressing method at temperatures of 1800-1820 °C and a pressure of 15 MPa from powders mixtures AlN-Y₂O₃-5%C(soot), AlN-Y₂O₃-3%C(diamond powder - DP), AlN-Y₂O₃-5%C(DP)-5%Mo. The structural and phase composition of the composites was investigated by X-ray phase analysis using the Rietveld method and using a Zeiss Evoma15 SEM. The measurements of the complex dielectric constant in the frequency range of 12.4-18 GHz were carried out by the waveguide method using the Keysight P9375A vector microwave circuit analyzer. The main AlN phase and the presence of new phases: С(graphite), Al₃(O,N)₄, and Al in the materials structures were revealed by the X-ray phase method. The graphitization process of DP is characteristic for these compositions and at free sintering [1]. In addition, the formation of Mo₂C is observed in the system AlN-Y₂O₃-C(DP)-Mo. Also, thanks to X-ray studies and SEM with analysis of the quantitative elemental composition in the main phases by the EDS method, was established the presence of a low concentration of O in the AlN lattice and was revealed the location of conductive phases (C, Mo₂C) in the structure of materials. The results of measurements of electrodynamic characteristics showed that the developed new composite materials with graphite phase inclusions have constant dielectric characteristics in the entire frequency range and are at the level of ɛr = 12.38-33.03 and tgδ=0.06-0.51. Composites with soot had the highest values of dielectric constant (33) and losses (0.51). Preservation of high dielectric characteristics of composites, and at the same time increasing the level of dielectric permeability, is achieved due to the features of structure formation, in particular, arrangement of conductive phases grains (C, Mo₂C) in the structure of composites and minimization of contacts between them.

The electrodynamic properties of new composite materials, produced by free sintering based on AlN with the addition of 1–5 wt

We present the results of the study of the microstructure of a ceramic composite based on aluminum nitride with different concentrations of yttrium oxide, synthesized by pressureless sintering. The thermal conductivity of the obtained materials was investigated, and the optimal amount of yttrium oxide in the composition for sintering large-sized parts used in electrotechnical devices was determined.

Electrophysical characteristics (electrical resistance and activation energy) of the aluminum nitride–titanium nitride ceramic composite are determined in the temperature range of 27–215°C.

The mechanical and physical properties, such as microhardness, strength, wear resistance, and electrical conductivity, of the materials for the tram pantograph contact insert, which is worked with the contact wire material of the catenary, have been investigated. As the pantograph insert materials, the composites on the basis of the MAX phases of the Ti3AlC2 and Ti2AlC systems were studied. They were made in two ways by one-step technology (hot pressing) and two-step technology (vacuum synthesis and hot pressing). The obtained properties were compared with the aluminum alloy from which pantograph inserts are currently made in Ukraine. It is shown that the wear resistance of composites from MAX phases obtained by one- and two-step technologies is practically the same and significantly dominates over that of aluminum alloy. However, they are paired differently with M1 copper wire. It was found the least wear of the copper counterbody in contact with the porous composite obtained by the one-step technology.