Controlled synthesis of high-quality W-Y2O3 composite powder precursor by ascertaining the synthesis mechanism behind the wet chemical method

As an emerging preparation technology, wet chemical method has been employed widely to produce lots of alloy materials such as W and Mo based alloys, owing to its unique technical advantages. Ascertaining the synthesis mechanism behind wet chemical method is indispensable for controlled synthesis of high-quality W-Y2O3 composite powder precursor. The co-deposition mechanism of yttrium and tungsten component behind the wet chemical method of preparing yttrium-doped tungsten composite nanopowder was investigated systematically in this work. A series of co-deposited composite powders fabricated under different acidity conditions were used as research targets for investigating the effect of surface composition and structure on co-deposition efficiency. It was found that white tungstic acid has more W-OH bonds and much higher co-deposition efficiency with Y3+ ions than yellow tungstic acid. It is illustrated that the coordination reaction between W-OH bonds on tungstic acid particles and Y3+ ions brings the co-deposition of yttrium and tungsten component into being. Through displacing H+ ions in W-OH bonds, Y3+ ions can be adsorbed on the surface of or incorporated into tungstic acid particles in form of ligand. Consequently, to control and regulate Y2O3 content in powder precursor accurately, H+ ion concentration in wet chemical reaction should be in range of 0.55-2.82 mol L- (-1) to obtain white tungstic acid. Besides, H+ ion concentration also has prominent effect on the grain size and morphology of reduced powder precursor. The optimal value should be around 1.58 mol L-1, which can lead to minimum W grain size (about 17 nm) without bimodal structure. The chemical mechanism proposed in this work could produce great sense to preparation of high-quality precursor for sintering high-performance Y2O3 dispersion strengthened W based alloys. Our work may also shed light on the approach to exploit analogous synthesis mechanism in other alloy systems. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.