Annealing effects on Laves phase-related body-centered-cubic solid solution metal hydride alloys

Abstract

Effects of thermal annealing (between 800 and 1100 °C) on the structural, gaseous phase and electrochemical hydrogen storage properties of a Laves phase-related body-centered-cubic (BCC) alloy, Ti15.6Zr2.1V40.0Cr11.2Mn6.9Co1.4Ni22.5Al0.3, were studied. Only BCC, TiNi, and C14 phases appeared in the as-cast sample. Annealing at 800 and 900 °C increased the main hydrogen storage BCC phase abundance and reduced C14 and TiNi catalytic phases. Annealing at 1000 °C promoted the formation of Ti2Ni phase. A σ-VNi phase appeared after annealing at 1100 °C. In addition, the annealed samples also contained Zr and TiO2 debris. Electrochemical results suggested optimized annealing conditions of 900 °C for 12-h to optimize the storage capacity, high-rate performance, and activation due to a favorable balance in abundance between storage phase (BCC) and catalytic phases (C14 and TiNi).