Ultrafast synthesis of nanocrystalline molybdenum powder by thermal plasma and its sintering behavior

Abstract Nanocrystals sintering is a critical way to achieve full-densified compact with fine grain size, which is highly desired to improve its mechanical properties by grain boundaries strengthening. In this work, a one-step plasma synthesis strategy was developed to synthesize Mo nanopowder using ammonium molybdate as precursor, and the reaction could be completed by an ultrafast way in several seconds. As obtained products exhibit single-crystalline structure and quasi-spherical shape with size of about 30 nm. The sintering behavior of Mo nanoparticles was further investigated by isothermal and nonisothermal processes, and the results reveal that Mo compact experiences different grain growth and microstructure evolution at different sintering stages. Fully densified Mo compact (99.13%) with well suppressed grain growth of about 7 μm was obtained at a rather low temperature of 1500 °C, and kinetics analysis illustrates that the surface diffusion with low activation energy is responsible for the high sintering activity of nanosized powder at low temperature.