Effect of organic additives on mechanical properties of SiC ceramics prepared by a modified gelcasting method

A novel and simple gel system of isobutylene and maleic anhydride (PIBM) was used to prepare SiC ceramics. The rheological behaviour of the SiC slurries was investigated as function of organic additives. The SiC slurries with 0.2wt.% PIBM and 0.2wt.% tetramethylammonium hydroxide (TMAH) showed low viscosity, which was favourable for casting SiC green bodies. In order to obtain homogeneous green bodies, polyvinyl alcohol (PVA) was used to assist the dispersion of carbon black in the slurries, and polyethylene glycol (PEG) was added to inhibit the surface exfoliation of green bodies. The content of PVA was controlled carefully to avoid the warpage of green bodies during the drying process. Finally, homogeneous defect-free SiC green bodies were successfully fabricated via aqueous gelcasting. The SiC ceramics sintered at 2100?C (prepared from slurries with solid content of 60wt.%) showed an average flexural strength of 305.7MPa with porosity of 19.92%.