Preparation of nano-sized Si/C/N microwave absorber

Nano-sized Si/C/N powders were prepared by chemical vapor deposition (CVD) at 1200°C~1600°C with different NH₃ flow rates. The effects of preparation technology, N content and phase composition on the microwave permittivity of the powders were investigated. The results show that a higher flow rate of NH₃ results in a higher N content, the degree of crystallization increases with the synthesizing temperature increasing, and the powders mainly consist of β-SiC. The N atoms are dissolved in SiC lattice, and the dissolved amount of N atoms decreases with the increase of synthesizing temperature. The amount of SiC in powders and the dissolved N amount have influence on the ε^', ε^", and tgδ (ε^"/ε^'). We believe that the Si/C/N nano-sized powders have the ability of absorbing microwave mainly due to the conductivity losses and the dielectric relaxation induced by the dissolved N atoms.