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

Abstract

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 Cu2(OH)3NO3 and H2WO4·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 °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 μm, 8.440 μm, and 6.290 μm, reduced by 40.51%, 46.06%, and 59.80%, respectively, compared to the particle size of pure copper powder, 15.648 μm. With increasing W content, the W-coated Cu particles gradually become denser and trend to grow from sphere to flake.