Nanostructured hard material composites by molecular engineering. I. Synthesis from soluble tungstate salts

A key issue, in the development of very fine grades, is to produce materials with high uniformity. The aqueous chemistry of tungsten offers several possibilities for the synthesis of homogenous molecular precursors containing W and Co mixed on the atomic scale. Powders containing (NH sub 4 ) sub 8 [H sub 2 Co sub 2 W sub 11 O sub 40 ] have been prepared starting from sodium tungstate or ammonium metatungstate. Nanophase powders of W-Co and WC-Co powders were obtained after reduction at 750 deg C under H sub 2 and carburisation at 1000 deg C under H sub 2 /CH sub 4 . Hard materials with submicron microstructures were obtained after sintering at 1410 deg C.