Fabrication of Ni-coated Al2O3 powders by the heterogeneous precipitation method

Ni-coated Al2O3 powders were prepared by the heterogeneous precipitation me thod using Al2O3. Ni(NO3)(2). 6H(2)O and NH4HCO3 as the starting materials. The amorphous NiCO3. 2Ni(OH)(2). 2H(2)O was uniformly coated on the surfac e of Al2O3 particles with the thickness of 20 nm. The amorphous coating lay er was crystallized to NiO with the size of about 15 nm at 500 degreesC for 2 hours in air, meantime. the dispersant was eliminated. NiO was completel y reduced to Ni at 700 degreesC for 4 hours in hydrogen atmosphere. Ni with the size of about 20 nm in the coating layer was spherical and weakly aggl omerated. The continuous coating layer became discontinuous during heating treatment. (C) 2001 Elsevier Science Ltd. All rights reserved.