Preparation and properties of Al_2O_3/Ni composite from NiAl_2O_4 spinel by in situ reaction sintering method

摘要

Al_2O_3/Ni nano composites were prepared from NiAl_2O_4 spinel by in situ reaction sintering method. The starting materials of Al_2O_3-NiO powder were synthesized by thermal decomposition of precipitates prepared from aluminum sulfate and nickel sulfate. The specific surface area of the Al_2O_3-NiO powder was >36 m~2/g. The Al_2O_3/Ni composites were obtained by firing the starting material buried in a carbon bed at 1500 deg C for 1 h. The resulting Al_2O_3/Ni composites have relative densities >96 percent (0-40 mol percent Ni). Nickel grains dispersed homogeneously in the microstructure, accounting for 10 percent of within the grains and 90 percent at grain boundaries. The average particle size of the former nickel grains was 150 nm while that of the latter grains was 300 nm. The maximum three-point bending strength was 408 MPa at 10 mol percent Ni sample and the maximum fracture toughness was 9.9 MPa m~(1/2) at 40 mol percent Ni sample. The Vickers hardness decreased slightly with increasing Ni content and this change is in good agreement with individual mixture rale.