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

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 (V2H or β1), 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 V2H ↔ VH ↔ VH2 (β1 ↔ β2 ↔ γ) hydrides, including thermal cycling (778 cycles) between the β and γ phases. Thermal cycling between VH ↔ VH2 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 β1-, β2- 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.