Gel casting process for Al2O3–SiC nanocomposites and its creep characteristics

A process for obtaining highly stable alumina–silicon carbide (SiC) co-dispersion in acidic aqueous medium has been described and composite fabrication by gel casting using co-dispersed alumina–SiC slurry has been demonstrated. The gel casting was accomplished by in situ polymerization of urea formaldehyde monomer. Nano-particulate silicon carbide has been provided an alumina like surface coating using hydrolyzed aluminium species, which produced stable alumina–SiC co-dispersion containing 55 vol.% solids loading suitable for gel casting. The alumina–SiC composite attained 97% theoretical sintered density at 1700 °C under gas pressures of 80 bar. Compressive creep test at different stress and temperature levels was performed for the gel cast alumina–SiC composite. The gel cast composite showed the activation energy (Q) of 869 kJ mol−1 and the stress exponent (n) as 1.72. The possible creep mechanism was discussed. The present work reports a novel process for preparing alumina–SiC co-dispersion in acidic medium, which otherwise undergoes hetero-coagulation or preferential settling. The surface modification technique, co-dispersion stability and flow characteristics, sintering and microstructural features have been studied and reported.