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Results of experimental studies of aluminum nitride based composites with addition of silicon carbide and molybdenum having high microwave absorption are presented. The interconnection between high level of absorption and volume electrical resistance was observed: maximum absorption of 6.5±1,0 dB/mm corresponds to the electrical resistance of (4—5)·105 Ohm·m. Level of absorption of 3.5±0,5 dB/mm is revealed for the dielectric material with electrical conductivity of 1012 Ohm·m. The patterns detected during the study allow to predict the minimum and maximum levels of absorption of microwave energy in the two-phase composites based on aluminum nitride with molybdenum or silicon carbide, based on the measured volume of electrical resistance.

The paper presents the results of experimental studies of thermal conductivity and microwave absorption in aluminum nitride based composites with different percentages of silicium carbide and molybdenum. It is shown that the optimal composition of the studied materials is the composite with 46% of silicium carbide and 4% of molybdenum. This composition reveals high UHF-energy absorption level of 42 dB/cm in the frequency range of 9.5—10.5 GHz and high thermal conductivity of 65 W/(m*K).

Analysis of properties and characteristics of the alumina, beryllium oxide and aluminum nitride based ceramic materials used in UHF electronic devices has been made. It was shown that the complex of parameters including structural and functional characteristics of the high-thermal conductive aluminum nitride ceramics prevail over all types of alumina ceramics and is not lower than the same characteristics of the beryllium oxide ceramics especially at the temperatures higher than 450 °C. The examples of the prevailing use of the aluminum nitride ceramics inside vacuum UHF-region devices: TWT’s and klystrons.

The article presents the results of experimental measurements. It is shown that the behavior of the dielectric constant and dielectric loss tangent in the investigated frequency range is due to the lack of relaxation processes in ceramics associated with the orientation polarization and to weak influence of ion and electron polarization.

Compositions of AlN–Y2O3–Mo and AlN–Y2O3–TiN composite materials with high thermal conductivity have been selected for bulk absorbers of microwave energy in delay systems. The thermal conductivity, electrical resistivity, and electromagnetic absorption of pressureless sintered AlN-based composites with different volume concentrations of conducting Mo and TiN particles are determined. [ABSTRACT FROM AUTHOR]

The structure and electro-physical properties of islet gold films on the surface of aluminum nitride are reported. [ABSTRACT FROM AUTHOR]