Low and high-pressure hydriding of V–0.5at.%C

Abstract The low-pressure hydriding characteristics of V–0.5at.%C alloy were determined in this study. There are several prior reports on the pressure-composition-temperature (p-c-T) isotherms and stability of the low-pressure vanadium hydride phases (V 2 H or β 1 ), and of vanadium alloyed with transition elements, but there are no reports on the hydrides of V–C alloys. The thermodynamic properties of the vanadium did not change significantly with the addition of carbon. In addition to low-pressure studies on V–0.5at.%C, we also performed high-pressure studies on V 2 H ↔ VH ↔ VH 2 (β 1  ↔ β 2  ↔ γ) hydrides, including thermal cycling (778 cycles) between the β and γ phases. Thermal cycling between VH ↔ VH 2 increased the pressure hysteresis. The effects of thermal cycling (4000 cycles) on the absorption and desorption isotherms of V–0.5at.%C and on the H/M ratios for the β 1 -, β 2 - and γ-phase hydrides are also presented. There was minimal decrepitation (pulverization) of the alloy; decrepitation of the V–0.5at.%C alloy was dramatically less than that of pure vanadium.