PREPARATION OF α-Al₂O₃/METAL NANO-COMPOSITE POWDER BY THE HETEROGENEOUS PRECIPITATION

Al₂O₃/W and Al₂O₃/Ni nano-composite powders, with mean particle sizes less than 50 nm, were prepared by the heterogeneous precipitation process using Al(NO₃)₃·9H₂O and (NH₄)₂CO₃ solutions as raw materials and tungsten and nickel nanometer powders as additive in different volume fractions (5%,10%). The α-Al₂O₃/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.