The decomposition behavior of as-received and oxidized TiH2 foaming-agent powder

The decomposition behavior of as-received and oxidized TiH2 powder has been studied using differential scanning calorimetry and X-ray diffraction. It was found that the decomposition of TiH2 in argon occurs in two stages, firstly the reduction in the stoichiometry of the hydride to delta-TiH1.5, and secondly, with progressive heating, decomposition of the hydride to form the beta- and alpha-phases. When heating in air, at low temperatures, oxidation of the hydride to form an oxyhydride occurs and with progressive heating, the oxidation products Ti3O and TiO2 are formed in increasing quantities. Heat treatment, to reduce the stoichiometry of the hydride and form an oxide layer, does delay the evolution of gas when re-heated in argon. A balance between the delay in gas evolution and detrimental gas loss is best achieved for pre-heat treating to between 530 and 630 degreesC. (C) 2003 Elsevier Science B.V. All rights reserved.