Chemical state of Ti in sodium alanate doped with TiCl3 using X-ray photoelectron spectroscopy

In this work, a study of the evolution of the chemical state of Ti in sodium alanate doped with 5 mol.% of TiCl3 using X-ray photoelectron spectroscopy (XPS) is presented. Samples ball milled at 2, 30 and 60 min were investigated. XPS analysis indicates that the titanium is partially reduced to the metallic state after 2 min of ball milling and completely reduced after 30 min of ball milling. Further milling does not change the valence state of the titanium. Moreover, the atomic concentration of titanium at the surface is decreasing with increasing milling time. Depth profile and atomic concentration analysis show that the samples are contaminated at the surface only by oxygen and carbon. Furthermore, the concentration of titanium as well as of the metallic aluminum is increasing with the sputtering time. Finally, the reduction of TiCl3 during the milling process explains that the theoretical capacity of 5.6 wt.% is never reached experimentally with doped sodium alanate. (c) 2005 Published by Elsevier B.V.