Thermal desorption spectra of hydrogen isotopes in the monohydride phase of V–H–D and Ti–V–H–D systems

Abstract

Thermal desorption of hydrogen isotopes in VH x D y ( x+ y≈0.6), Ti 0.1V 0.9H x D y ( x+ y≈0.6) and Ti 0.33V 0.67H x D y ( x+ y≈0.9) alloys has been studied by means of simultaneous measurements of thermogravimetric and differential thermal analyses and mass spectrometry. H desorbs more easily than D in all the samples studied and thus H is enriched in the gas phase during desorption. The H enrichment factor in the gas phase is in the following order, V≥Ti 0.1V 0.9>Ti 0.33V 0.67. The H enrichment factor also depends on the [H]/[D] ratio, which suggests that H and D in the solid phase influence the desorption kinetics of the other isotope probably through an indirect interaction mediated by metal atoms. The equilibrium pressure is in the order of Ti 0.1V 0.9>V>>Ti 0.33V 0.67. Deuterides have higher equilibrium pressures than protides, and this isotope effect is Ti 0.33V 0.67>Ti 0.1V 0.9≈V. There are no correlations in the isotope effects between the thermal desorption and the equilibrium pressure. Hydrogen diffusion in solids might play an important role in the thermal desorption.