Abstract:The C_sf/Si₃N₄ composites were prepared by hot-press sintering method using α-Si₃N₄ power, short carbon fibers and La₂O₃-Y₂O₃ sintering additives. The mechanical and microwave dielectric properties of C_sf/Si₃N₄ composites were studied and discussed. The results show that the addition of the short carbon fibers can not destroy the relative density of the sintered samples, but it deteriorates the flexural strength of the sintered samples, so the flexural strength of the silicon nitride matrix is the highest among the samples. The real part (ε′) and the imaginary part (ε″) of the permittivity of C_sf/Si₃N₄ composites greatly increase with increasing volume fraction of the short carbon fibers, achieve the maximum 73.1 and 101.5, respectively. A strong frequency dependence of the imaginary part (ε″) of the permittivity is observed.

Key words: C_sf/Si₃N₄; composites; short carbon fibers; mechanical property; dielectric properties