Evaluation of superplastic-foamed zirconia-based ceramics using foaming agent and a superplasticity facilitator derived from rice husk

The applicability of rice husks to solid phase foaming ceramics was assessed. Through an atmospheric heat treatment on silicon carbide based mixture produced by the reduction heat treatment of rice husks, the residual carbon was mostly eliminated, giving a foaming agent composed of approximately SiC and SiO2. Solid-phase foamed porous ceramics was fabricated using this rice husk-derived foaming agent and the properties were compared with that fabricated from commercially available SiC. The sample fabricated from the rice husk-derived foaming agent showed favorable performances in terms of both strength and heat insulating properties. In comparison with the sample fabricated by adding commercially available silica in addition to commercial SiC, the strength became comparable, however, its heat insulating property was still inferior to that using rice husk-derived foaming agent. The increase in mechanical strength can be ascribed to the suppression of the grain growth due to the added silica. The formed silica phase existing at the grain boundaries would affect the thermal conductivity.