Serbenyuk T. Regularities of the structure formation of AlN-SiC-based ceramic material with specific functional properties for electrical and constructive applications.

The thesis deals with solution of actual scientific and technical tasks consisting in establishing of regularities of the AlN-SiC-based materials structure formation having designated functional properties for electrical and constructive applications. It has been shown for the first time that one can purposefully regulate the level of microwave absorption and other characteristics of the AlN -based material varying content and dispersion (50 - 1 µm) of the SiC powder: functional properties are improving when amount of SiC is increased up to 50 wt.% and powder dispersion decreased down to 5 µm. It has been revealed by Auger spectroscopy that during sintering of the AlN(2H)-SiC(6H)-Y2O3-based composites the mutual solubility of components took place, but formation of aluminum yttrium garnet Y3Al5O12 layers between SiC and AlN restricts the solubility process and enables to preserve the material dielectric properties in parallel with densification to practically porousless state (98-99%). X-ray diffractometer analysis has shown that when 16-50 wt.% of SiC to AlN-4 wt.%Y2O3 were added the с lattice parameter of the AlN increases from 0.49821 to 0.49837 nm, and а decreases from 0.31110 to 0.31070 nm. As construction electrical materials are recommended materials prepared by pressureless sintering at 1900 0С having the absorption coefficient L=32-36 dB/cm, (at 3.0-10.5 GHz), dialectic permittivity lambda=15-22 and dielectric loss tangent tg lambda=0.52-0.6 (at 3-3.3 GHz), specific resistance R 108 Ohm m, thermal conductivity lambda=40-75 W/(m К), bending strength Rbm=168.0-209.0 МPа, Vickers hardness НV 15,4-16,0 GPа, fracture toughness K1С=3.4-3,9 МPа m0.5, with a porosity of 1-2%.