Mechanism and kinetics of mechanically induced transformation of titanium and titanium hydride: Effect of reaction medium on microstructure, morphology and hydrogen-uptake properties

The stimulating effect of graphite addition on hydrogen sorption/desorption properties of titanium activated under ball milling and titanium hydride activated or prepared under ball milling is studied using X-ray diffraction, scanning and transmission electron microscopy, and temperature-programmed reaction/desorption techniques. The formation of microporous carbon matrix containing randomly distributed titanium or titanium hydride fragments of several nm in size is found to be the major effect of graphite addition. This kind of morphology allows the hydrogen transport to titanium or from titanium hydride surfaces without hindrances and improves titanium-hydrogen interaction through modifying the titanium surface and subsurface layers by interstitial C atoms.