POROUS SILICON OXYCARBIDE COMPOSITES WITH ALIGNED MACRO POROSITY FROM WATER-BASED SLURRY BY FREEZECASTING PROCESS

摘要

Directionally aligned porous SiOC composites were prepared using polycarbosiloxane (SILRES~R H62 C) as a preceramic polymer. To decrease shrinkage during pyrolysis, rice husk ash (RHA, amorphous silica) was added as a filler. The influence of different freezing rates and filler to polymer ratios on freeze-casting performance of 30 wt.-% aqueous polymer-silica suspensions are studied. The use of water as a liquid vehicle and dextrin as a binder was examined successfully. After pyrolysis of the green bodies at 1100 °C under nitrogen atmosphere, the monoliths show macro porous tailored lamellar structures with porosities around 65%. The results show that an increase in the polymer to RHA ratio results in smaller pore sizes and thinner pore walls. Also, by decreasing the freezing rate, pore coarsening is observed.