Effect of Ni in α-Al_2O_3/Ni nanocomposite powders on the phase transformation temperature to alpha alumina pressing TiC/Ti/Al powder mixtures

Al_2O_3/5%Ni and Al_2O_3/10%Ni nanocomposite powders with mean particles size less than 50nm were respectively prepared by the heterogeneous precipitation process using Al(NO_3)_3·9H_2O and (NH_4)_2CO_3 solutions and nickel nano-powders as raw materials. The phase analysis and the powder morphology were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) respectively. After Al(OH)_3/Ni dried gel calcined at 1000, 1100 and 1150℃ for an hour in vacuum, the Al_2O_3 powders combinated with 10%Ni transfer to α-Al_2O_3at 1150℃, while the Al_2O_3 powders without Ni and with 5vol%Ni remain γ-Al_2O_3 type in the same condition, that is the phase transformation temperature to alpha alumina drops by adding nanometer nickel powders. The nanocomposite powders are simply mechanically mixed together from the XRD patterns, because no new phases, which are different from Al_2O_3 and Ni, were observed.