Effect of nickel content on the sintering behavior, mechanical and dielectric properties of Al2O3/Ni composites from coated powders

Al2O3/Ni composites were fabricated by hot pressing coated powders, in which nanosized Ni particles were coated with layers of alumina precursor by the heterogeneous precipitation method. The calcined powders could be sintered to above 96% of the theoretical density at as low temperature as 1350°C. The average alumina grain size in the composites decreased with increasing Ni content. Compared with that of monolithic alumina, the fracture toughness and the fracture strength of alumina could be increased by 28 and 43% by adding 2 and 5.5 vol.% Ni, respectively. The enhancement in mechanical properties can be explained from the unique microstructure of sintered bodies. The dielectric constant of Al2O3/Ni composites was found to increase with Ni content, which should be primarily attributed to the size effect of alumina grains.