Microwave processing of Ni-Al2O3 composites

Nickel-alumina cermets were sintered in this work by microwave and conventional techniques in a forming gas (5% H2, 95% N2) atmosphere. The composites were fabricated by sol-gel, powder mixture, and nickel oxalate powder precursor mixture route. The sol-gel and the powder precursor routes required calcining to decompose and remove the volatile materials to give nickel and alumina phases only. The sintered densities were measured and each powder processing technique was compared. The sol-gel samples using boehmite as a starting material were cracked and had densities near 50% of theoretical. Densities obtained from powder mixture route were 81% of theoretical. Densities obtained from the nickel oxalate route were at 93% of theoretical. 9 refs., 2 figs., 4 tabs