| Abstract: | 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 highquality W-Y_2 O_3 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 Y~(3+)ions than yellow tungstic acid.It is illustrated that the coordination reaction between W-OH bonds on tungstic acid particles and Y~(3+)ions brings the co-deposition of yttrium and tungsten component into being.Through displacing H~+ions in W-OH bonds,Y~(3+)ions can be adsorbed on the surface of or incorporated into tungstic acid particles in form of ligand.Consequently,to control and regulate Y_2 O_3 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 Y_2 O_3 dispersion strengthened W based alloys.Our work may also shed light on the approach to exploit analogous synthesis mechanism in other alloy systems. |
