Evaluation of Nano-Sized Nickel Dispersed Alumina Materials
Yoshitaka Nishimura, Kenichiro Aikawa, Seong-Min Choi, Shinobu Hashimoto and Hideo Awaji
Abstract:In order to develop new ceramics for a power electric device, alumina/nickel (Ni) nanocomposites were fabricated using the soaking method and the pulse electric current sintering technique. The volume fractions of Ni were 0.5, 1, and 5 % in γ-alumina powder. 10 mass% α-alumina powder was added as a sintering seed. SEM and TEM observations revealed that the nanocomposites exhibited an intra-granular fracture mode, and agglomerated Ni particles existed mostly along alumina grain boundaries especially for 5 vol% Ni. The experimental results showed that the strength and fracture toughness values of the nanocomposites were higher than those of monolithic alumina, and the thermal conductivity decreased slightly with increase in Ni content. Moderate improvements in the strength and fracture toughness seemed to result from the fact that the nano-sized Ni particles dispersed within alumina grains creating dislocations around the Ni particles, which reduced sintering residual stresses in alumina grains and expanded the frontal process zone size. It was concluded that nanocomposites with a lower Ni content had better mechanical, electrical, and thermo-mechanical properties. Key Words:Ceramics, Nanocomposites, Alumina, Nickel, Thermal expansion, Thermal conductivity, Break down voltage