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

The effect of inert filler addition on the microstructural development and flexural strength of porous SiC ceramics processed by a method using polymer microbeads as a pore former and submicron SiC powder as an inert filler was reported. A powder composition with 20 wt% filler PSCF was prepared and the milled powder was dried and pressed uniaxially into rectangular bars at 28 MPa. The results show that the filler grain could be grown at the expense of the submicron SiC grains synthesized from the polysiloxane-derived SiOC through an Ostwald ripening mechanism. The finer microstructure obtained in the PSCF specimen is attributed to the impingement of growing grains, which are added as fillers. The decrease in porosity with increasing sintering temperature from 1750 to 1900°C of the filler is attributed to the further densification of porous SiC ceramics during sintering.