Synthesis of Fine Mo2C Powder from Prereduced Mo in Undiluted CH4 Flow

Abstract

The carburization behavior of prereduced Mo was investigated in undiluted CH4 flow at 900–1000 K. Prior to the experiments, equilibrium thermodynamic analysis was carried out in the Mo-C-H system. The products were characterized by mass measurement, x-ray diffraction and scanning electron microscopy techniques. A single Mo2C phase was obtained within ~45 min, ~5 min, and ~2.5 min at 900 K, 950 K, and 1000 K, respectively, at CH4 contents higher than the predicted ones. The reasons for this behavior were discussed in terms of CH4 stability, open tube flow, and self-created atmosphere in the powder bed. The fractional conversion-time curves indicated that the carburization kinetics followed a linear rate law. The Mo2C crystallite size (26–37 nm) and platelet thickness (50–100 nm) were found to be smaller than those of the parent Mo phase. These findings were attributable to the defects formed as a result of stresses associated with the reduction and the carburization.