Synthesis and properties of Ni-α-Al2O3 composites via sol-gel

Ni-α-Al2O3 metal-ceramic composites with metal loadings ranging from 33 to 67 vol.% were synthesized via a sol-gel (both polymeric and colloidal) technique. The polymeric route involves introducing nickel formate during the hydrolysis and condensation of aluminum isopropoxide while the colloidal route involves precipitating Ni(OH)2 onto boehmite particles. Transformation to Ni-α-Al2O3 composites is accomplished by calcination in a reducing environment followed by hot pressing at about 1400°C in an oxygen partial pressure of 10−12 atm. The composites exhibit a highly interconnected microstructure, composed of continuous Ni and alumina networks, and enhanced fracture properties compared with pure alumina.