Pressureless sintering of Al2O3/Ni nanocomposites

In the present study, an Al2O3/Ni nanocomposite containing 5 vol% Ni is prepared by pressureless sintering at 1400 degrees C for 2 h. Most nickel inclusions, around 70% in the sintered nanocomposite, locate at the intergranular sites, the triple junctions and Al2O3/Al2O3 grain boundaries. The average size of the nickel inclusions at the triple junctions, grain boundaries and intragranular locations is 145, 131 and 73 nm, respectively. The average size of all nickel inclusions is 118 nm. The presence of nickel inclusions can prohibit the grain growth of matrix grains. The size of Al2O3 grains in the sintered nanocomposite is only 490 nm. The strength of the nanocomposite is thus high for the refined microstructure. The matrix Al2O3 grains and Ni inclusions at triple junctions underwent considerable coarsening during a post-annealing treatment at 1300 degrees C for 2 h. The strength of the annealed composites is thus reduced significantly after annealing. (C) 1999 Elsevier Science Limited. All rights reserved.