Shape-Controlled Synthesis of Ultrafine Molybdenum Crystals via Salt-Assisted Reduction of MoO2 with H2

In the current investigation, the salt-assisted hydrogen reduction of MoO2, was proposed to prepare ultrafine Mo single crystals with controllable shape and size. By adjusting the type and amount of added chlorine salts (NaCl, KCl, CaCl2, and MgCl2) and temperature, ultrafine Mo single crystals with different shapes and sizes were prepared successfully. When no salt is added, the produced Mo approximately keeps the shapes and size of the raw MoO2 in the temperature range of 805-1000 degrees C. However, by adding 0.1 mass % of chlorine salts, ultrafine, uniformed and spherical Mo crystals were obtained. As the amount of added salt increased, the shape of the Mo crystal would change from a sphere to a polyhedron. By increasing the amount of added salts to 0.5 mass %, ultrafine Mo single crystals with polyhedral shape were synthesized. The effects of the added salts on the nucleation, growth, and shape control of the Mo crystal were investigated in detail.