We report on the design of highly absorptive thermostable composite materials for microwave applications. Ceramics comprising the thermostable phosphate host and silicon carbide particles or whiskers were studied in a wide frequency range from several Hertz up to microwaves. It was demonstrated that a thin layer of ceramics placed on the back-reflector absorbs perfectly at the 30 GHz frequency. In the case of a free-standing ceramic composite layer being 1 mm thick, it provides more than 50% of absorption.

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Hybrid composite materials based on an aluminium phosphate matrix with silicon carbide whiskers and multi-walled carbon nanotubes were studied in a wide frequency range (20 Hz to 36 GHz). It was demonstrated, that the addition of the silicon carbide whiskers enhances the dielectric permittivity and conductivity. This was explained by the difference in tunnelling parameters. Hybrid ceramics with nanotubes and whiskers also exhibits substantially improved electromagnetic shielding properties. The hybrid ceramics with 10 wt. % silicon carbide whiskers and a 1 mm thick 1.5 wt. % carbon nanotube layer, show higher than 50% absorption of electromagnetic radiation.

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