Phase and Microstructure Transition of High Cu Content Cu-W Composite Powder Fabricated by Spray Drying

Cu-W composite powder with various W contents (0, 10, 20, and 30 wt%) has been fabricated by spray drying, calcination, and two-stage hydrogen reduction in this work. The microstructures and phase evolution of Cu-W composite powder were studied by FESEM, HRTEM, and XRD. Results show that precursor powder is composed of Cu-2(OH)(3)NO3 and H2WO4 center dot H2O. Spherical CuWO4 with a particle size of about 50 nm and micron-scale flat flake CuO were obtained when the calcination temperature was 500 degrees C. Through chemical vapor transport (CVT) during the reduction process, volatile WO2(OH)(2) continuously migrates to the copper surface and is reduced to W, resulting in a W-coated Cu structure. This coating structure can inhibit the aggregation and growth of copper particles. The particle sizes of Cu-10 wt%W, Cu-20 wt%W, and Cu-30 wt%W composite powders are 9.309 mu m, 8.440 mu m, and 6.290 mu m, reduced by 40.51%, 46.06%, and 59.80%, respectively, compared to the particle size of pure copper powder, 15.648 mu m. With increasing W content, the W-coated Cu particles gradually become denser and trend to grow from sphere to flake.