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 degreesC 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 micro structural features have been studied and reported. (C) 2004 Elsevier B.V. All rights reserved.