PRECERAMIC-POLYMER-BONDED SiC PREFORMS FOR HIGH VOLUME FRACTION SiCp/Al COMPOSITES

摘要

Preceramic polymer polycarbosilane (PCS) and silicon carbide (SiC) powders were used as the starting materials for the fabrication of porous SiC ceramic preforms. Since the aim of these preforms was to make SiC/Al MMC with high solid loading, maximum packing density of pressed compact was designed using Dinger-Funk distribution with an exponent of 0.37. Additional in-situ SiC from an organic-inorganic transformation during heat treatment process acted as the bonding material between SiC particles. The effect of the SiC powdenPCS ratio on the porosity and flexural strength of the porous SiC ceramics were investigated. Open porosity of the preforms varied from 30 to 45%. Fracture strength of the porous SiC ceramics was in the range of 20-70 MPa. No strength degradation was observed from thermal shock test at △T lower than 300°C. An infiltrated SiCp/Al composite exhibited flexural strength of 655±104 MPa.