J. Mater. Sci. Technol. ›› 2020, Vol. 36: 118-127.DOI: 10.1016/j.jmst.2019.05.067

• Research Article • Previous Articles     Next Articles

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

Zhi Dong, Nan Liu, Weiqiang Hu, Zongqing Ma*(), Chong Li, Chenxi Liu, Qianying Guo, Yongchang Liu   

  1. State Key Lab. of Hydraulic Engineering Simulation and Safety, School of Materials Science and Engineering, Tianjin University, Tianjin, 300072, China
  • Received:2019-01-18 Revised:2019-04-10 Accepted:2019-05-06 Published:2020-01-01 Online:2020-02-11
  • Contact: Ma Zongqing

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 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.

Key words: W-Y2O3, Wet chemical method, W-OH bond, Ligand, Co-deposition mechanism