Preparation of NiAl/Al_2O_3 Composites

摘要

Fine powders of intermetallic NiAl can be prepared by a heat-treatment and subsequent decarbonization of organic salt precursor, [Ni(N_2H_4)_2](C_6H_5COO)_2 + Al(C_6H_5COO)_(1.7)(OH)_(1.3), precipitated in an equivolume H_2O/methanol solution. Composite powders have been prepared from precursors containing α-Al_2O_3 as a matrix. Thermal decomposition or the precursors in an argon atmosphere results in the mixture of Ni_3C (or Ni dissolving C), amorphous-Al_2O_3, and free carbon at 500℃. The decomposition products are converted into single phase NiAl at 1350℃. Composite powders of NiAl and α-Al_2O_3 are efficiently prepared on account of the difference in reactivity between α-Al_2O_3 powder (15.3 m~2g~(-1)) mixed for matrix and organic salt-derived am-Al_2O_3 with filler particle size and homogeneous mixing with Ni_3C and C. The composite powders with the size of 0.3μm and carbon content less than 0.1% can be densified to 98.4% of the theoretical density. The grain size of α-Al_2O_3 and NiAl are 1.0 and 1.5μm, respectively. The alternative use of γ-Al_2O_3 and α-Al_2O_3 to the aluminum-precipitate has also been examined.