Pressureless sintered SiC matrix toughened by in situ synthesized TiB_2: Process conditions and fracture toughness

摘要

This paper reports the fabrication of SiC toughened by in situ synthesized TiB_2 based on pressure-less sintering technique using TiO_2, B_4C, C and SiC as starting materials. The process conditions were investigated in detail, including the pre-sintering temperatures, carbon contents, differently sized TiO_2 powders, TiB_2 volume contents, final sintering temperature and time. These conditions were found to have great influence on the TiB_2 toughened SiC in terms of relative density, TiB_2 particle size and fracture toughness. Homogeneous dispersion of in situ synthesized TiB_2 secondary phase was confirmed to enhance the K_(IC) of the SiC matrix. The K_(IC) of SiC toughened by in situ synthesized TiB_2 (15 vol%) reaches 6.3 MPa m~(1/2), which is among the highest values reported so far on TiB_2 reinforced SiC composites based on the pressure-less sintering technique using TiO_2 as Ti source.