Porous sodium borate-bonded SiC ceramics

Porous silicon carbide ceramics were fabricated from SiC, sodium borate, and starch at temperatures as low as 650–800 °C by a simple pressing and heat-treatment process. The effects of heat treatment temperature and starch content on the porosity and strength of the ceramics were investigated. During heat treatment, the sodium borate transformed to a viscous phase, which acted as the bonding material between SiC particles, and the starch decomposed into gases, leaving pores. The porosity of the porous SiC ceramics could be controlled within a range of 47–64% with the present set of processing conditions. The porous SiC ceramics showed a maximum 64% porosity when 43.2 wt% SiC particles and 10.8 wt% sodium borate were used with 46 wt% starch. Flexural strength was at a maximum (37 MPa at 52% porosity) when the sintering temperature was 750 °C and the starch content was 40 wt%.