The surface characterization of the early stages of the oxidation of titanium

In order to study the early stages of oxidation of pure titanium surface na noscale characterisation has been carried out using different surface sensi tive techniques. Metal surfaces have been prepared so as to study the effec ts of different surface finishes such as buffing (BP), chemical (CP), elect rical (EP) and mechano-chemical (MCP) treatments. Characterisation of the o xide layers has been carried out using scanning electron microscopy (SEM),A uger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) . These measurements have shown that the BP and MCP surfaces have thick mod ified layers whereas only very thin oxide layers are formed on the CP and E P surfaces. The influence of hydrogen on the titanium oxidation during the surface treatments has been estimated by obtaining the depth profiles of hy drogen, as measured using elastic recoil detection analysis (ERDA). High co ncentrations of hydrogen have been found in the surface regions especially for MCP and BP treatments. An oc-titanium single crystal has been used to i nvestigate the initial stages of the oxidation processes using grazing inci dence reflection high energy electron diffraction and Auger electron spectr oscopy (RHEED-AES). This method has demonstrated the time dependence of the titanium oxidation during the early stages with the RHEED intensities from the alpha-titanium single crystal surface, TiO being observed in the oxide layer. We discuss the characteristics of the oxidised surface on a sub-mic ro scale in relation to parameters such as the thickness of the oxide layer , crystalline state, chemical state, compact ness of the oxide layer and hy drides of titanium.