PREPARATION OF α-Al_2O_3/METAL NANO-COMPOSITE POWDER BY THE HETEROGENEOUS PRECIPITATION

Al_2O_3/W and Al_2O_3/Ni nano-composite powders, with mean particle sizes less than 50 nm, were prepared by the heterogeneous precipitation process using Al(NO_3)_3·9H_2O and (NH_4)_2CO_3 solutions as raw materials and tungsten and nickel nanometer powders as additive in different volume fractions (5%,10%). The α-Al_2O_3/W(Ni) nano-composite was obtained by calcining Al(OH)_3/W(Ni) dried gel at 1000(1150)℃ for an hour in vacuum. Adding tungsten or nickel nanometer powder can both reduce the phase transformation temperature to alpha alumina, which is lower by adding tungsten than that by adding nickel. The more secondary nanometer phase is, the lower the phase transformation temperature to alpha alumina will be. The composite powder is simply mechanically mixed together, because no new phases were observed, which is different from alumina and tungsten or nickel.