Effect of inert filler addition on microstructure and strength of porous SiC ceramics

摘要

Porous ceramics are of technological interest because of their unique characteristics such as low density, low ther_mal conductivity, high thermal shock resistance, high permeability, and high specific strength [1-5]. Specifically, porous silicon carbide (SiC) ceramics are used as molten metal filters, diesel particulate filters, and preforms for metal matrix composites on account of their excellent permeability, thermal shock resistance, specific strength, and corrosion resistance at high temperatures [6-9]. Dif_ferent processing routes for porous SiC ceramics have been developed for specific applications to satisfy the associated requirements of porosity, pore size, and degree of inter-connectivity. These manufacturing techniques include replica techniques [10, 11], sacrificial template techniques [12, 13], and reaction techniques [8, 14]. Recently, a new processing method for fabricating porous SiC ceramics was developed based on the following strategy [15, 16]: (1) pyrolysis of carbon-filled polysiloxane at 1000 °C, which leads to the conversion of polysiloxane to silicon oxycarbide (SiOC); (2) carbothermal reduction of SiOC and C mixture at 1450 °C, which converts the mixture to SiC ceramic; and (3) liquid-phase sintering of SiC using А1203_Y203 as a sintering additive at 1750-1950 °C. This letter reports the effect of inert filler addition on the microstructural development and flexural strength of por_ous SiC ceramics processed by the above method using polymer microbeads as a pore former and submicron SiC powder as an inert filler.