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

Ni-coated Al2O3 powders were prepared by the heterogeneous precipitation method using Al2O3, Ni(NO3)2·6H2O and NH4HCO3 as the starting materials. The amorphous NiCO3·2Ni(OH)2·2H2O was uniformly coated on the surface of Al2O3 particles with the thickness of 20 nm. The amorphous coating layer was crystallized to NiO with the size of about 15 nm at 500°C for 2 hours in air, meantime, the dispersant was eliminated. NiO was completely reduced to Ni at 700°C for 4 hours in hydrogen atmosphere. Ni with the size of about 20 nm in the coating layer was spherical and weakly agglomerated. The continuous coating layer became discontinuous during heating treatment.