Regulation mechanism of morphology and particle size of ultrafine molybdenum powder prepared via hydrogen reduction of gaseous molybdenum trioxides

In this study, molybdenum powder with desired morphology and particle size was produced through hydrogen reduction of gaseous molybdenum trioxide by changing the hydrogen partial pressure, reaction temperature, hydrogen preheating temperature, and cooling gas flow rate. At the reaction temperature of 1000 degrees C, the reaction product was a mixture of MoO2 and Mo. The reduction rate reached 100% at 1100 degrees C, and a further increase in temperature from 1100 degrees C to 1200 degrees C caused the average particle size of molybdenum powder to increase from 26.2 nm to 63.1 nm. Both the hydrogen temperature and the cooling intensity during the reaction had a great influence on the nucleation and growth of the grains, respectively. The molybdenum powder obtained without hydrogen preheating exhibited higher nucleation rates and finer grains than those exposed to hydrogen preheating. The molybdenum powder particles evolved from irregular polyhedra to spheres as the cooling intensity decreased through the injection of cooling gas. Therefore, the results of this work provide theoretical guidance for tuning the morphology and particle size of molybdenum powder.