| Summary: | In this study, oxygen reduction behavior of TiH<sub>2</sub> powders during dehydrogenation process was investigated based on thermodynamics. During the hydrogenation−dehydrogenation (HDH) method to fabricate Ti powder, TiH<sub>2</sub> was formed from a Ti sponge through hydrogenation annealing, and was easily pulverized even by ball milling due to its brittle nature. The ball milling process caused an increase in the oxygen concentration from 0.133 to 0.282 wt %, and transmission electron microscopy and X-ray photoelectron Spectroscopy results demonstrated that the formation of oxide layers such as TiO and TiO<sub>2</sub> formed on the surface of the TiH<sub>2</sub> powder resulted in the higher oxygen content. Dehydrogenation, which is the process originally conducted to eliminate hydrogen from TiH<sub>2</sub>, was used to remove and/or reduce oxygen, resulting in the reduction of the oxygen concentration from 0.282 to 0.216 wt %. Thermodynamic calculations confirmed the possibility of oxygen reduction by atomic hydrogen but molecular hydrogen has no function for the oxygen reduction. Glow discharge mass spectrometry (GD-MS) analysis, which checks H<sub>2</sub>O flow as an evidence of the oxygen reduction by hydrogen, supported the fact that the atomic hydrogen formed during the dehydrogenation process is able to play a critical role in decreasing the oxygen content.
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