Preparation of nickel-coated powders as precursors to reinforce MMCs

The preparation of nickel-coated ceramic particles as precursors for MMC fa brication was studied. Al2O3 and SiC powders of three different particle si zes were successfully coated with Ni using an electroless metal plating tec hnique. Uniform and continuous nickel films were deposited on both, alumina and silicon carbide powders, with a final composition ranging from 1.6 to 1.9wt% phosphorus, 18-21wt% of metallic nickel and the balance is ceramic. XRD showed that the Ni-P deposit was predominantly amorphous. However, afte r heat treatment, the metallic deposits crystallize into Ni and Ni3P phases , as confirmed by DSC analyses. Preliminary results showed that the use of Ni-coated powders enhances the wettability between the matrix and ceramic p hase when processing particulate MMCs by infiltration techniques. The coati ng promoted easy metal flow through the preform, compared to the non-infilt ration behavior of the uncoated counterpart samples. (C) 2000 Kluwer Academ ic Publishers.