Fabrication and Characterization of In Situ Porous Si_3N_4-Si_2N_2O-BN Ceramic

摘要

Porous Si_3N_4-Si_2N_2O-BN ceramic was fabricated at 1750℃ using Si_3N_4, BN, and (NH_4)_2HPO_4 as starting materials. During the sintering process, oxygen from the decomposed products of (NF_4)_2HPO_4 would bond Si and N in the liquid phase to form Si_2N_2O. The microstructure and properties of the porous ceramics were investigated. With the (NH_4)_2HPO_4 content varied from 10 to 50 vol.%, porosity of the porous Si_3N_4-Si_2N_2O-BN ceramic increased from 43.5% to 51%. The microstructure, mechanical, and dielectric properties was well controlled by adjusting (NH_4)_2HPO_4 contents. The present technique offers a more simple way of synthesizing porous Si_3N_4-Si_2N_2O-BN ceramics.