Improvement in hydrogen storage characteristics of titanium-chromium-vanadium BCC solid solution by melt-quenching

The purpose of this study is to increase the rechargeable hydrogen storage capacity of Titanium-Chromium-Vanadium (Ti-Cr-V) body-centered cubic (BCC) solid solution alloy by making a uniform alloy with high crystallinity and homogeneity on the nano-scale. The samples were prepared by a melt-quenching method, and the effects of this method on the BCC alloy were investigated using X-ray diffraction, optical and electron microscopies, and a pressure-composition-temperature (P-C-T) analyzer. It was found that the quenched alloy had highly crystalline, sub-micron scale crystals and a high dislocation density compared with the arc-melted alloy. As a result, the plateau in the P-C-T characteristics became a steep slope with large hysterisis. The quenched alloy was heat-treated to improve this plateau. This caused an increase in the grain size and a decrease in the dislocation density of the alloy; however, its high crystallinity was retained. The heat-treated alloys had a high maximum and rechargeable hydrogen storage capacity and a flat plateau in their P-C-T characteristics. As a result, the rechargeable hydrogen storage capacity reached 2.56 mass% in the pressure region of 0.1-4.5 MPa at 293 K.