Surface segregation and oxidation of Ti in a V–Ti alloy

Influence of heat treatment on hydrogen ingress into V–4Cr–4Ti alloy

“…In the cases of vanadium alloys, however, not only impurities but also the redistribution of constituent elements of the alloy could have a strong influence on the surface reactions of hydrogen isotopes. The present authors have examined the effects of heat treatment on surface composition and hydrogen absorption of V-4Ti alloy [8,11]. It was found that Ti segregated to the surface of V-4Ti alloy during vacuum heating at temperatures from 823 to 1273 K [11] and the hydrogen absorption rate radically decreased owing to this surface segregation of Ti [8].…”

Influence of oxygen and carbon on performance of superpermeable membranes

“…The specimen was heated at a given temperature for 600 s, and the decomposition of so-called natural oxide film was examined by XPS. The change in oxidation state of V was analyzed by deconvolution of V 2p photoelectron spectra, and the atomic ratio of oxygen to V ([O]/[V]) was evaluated from the intensity ratio between O 1s and V 2p photoelectron peaks [9]. It is apparent that [O]/[V] started to decrease at around 700 K. The conversion of V oxides into the metallic state was also initiated at 700 K and almost completed at 900 K. It should be emphasized that [O]/[V] did not reach zero even in the temperature range above 900 K. Schiechl and Winkler [6] examined the oxidation of V(1 0 0) surface by XPS under 6.6 × 10 −6 Pa of O 2 at various temperatures and reported that V 2 O 3 was formed below 873 K, whereas (5 × 1)-O superstructure was observed at higher temperatures.…”

Surface Segregation of Ti in a V-4Cr-4Ti Alloy and Its Influence on the Surface Reaction Rates of Hydrogen Isotopes

“…The spectra of V 2p and Ti 2p photoelectrons were deconvoluted in the same manner as in the previous study 11) to examine the change in the oxidation states of V and Ti with the heating temperature, the results of which are shown in Figs. 3 and 4, respectively.…”

“…11,12) This enrichment of Ti at the surface resulted in a large reduction in the hydrogen absorption rate in the temperature range from 523 to 1023 K. This reduction was ascribed to oxide formation due to preferential oxidation of segregating Ti by water vapor contained in the hydrogen gas as an impurity. 11,12) A similar effect of heat treatment on hydrogen absorption was also observed for a V-4Cr-4Ti alloy.…”