Approach to deoxidation of metals of the groups VB and VIB through 'oxide removal' diagrams.

The wettability of solid surfaces by liquid metals is inhibited by the presence of oxide surface layers; as a consequences, these types of technological processes are generally carried out under high vacuum or reducing atmospheres. In particular, when metals able to form volatile oxides and suboxides are considered, deoxidation of surfaces can be achieved by thermovacuum treatment, especially if the evaporation of oxides and suboxides is enhanced by providing quantitative removal of vapours from the gas phase overhanging the metal. The evaporation rates of any oxygen-containing species can be evaluated by using the Hertz-Langmuir-Knudsen equation, allowing the appropriate conditions for surface cleaning to be selected.