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Martensitic transformation and tensile properties of 4 to 5 mol%Sn-doped Ti-16 mol%Nb alloys consisting of biocompatible elements were investigated to provide superelasticity for biomedical applications as a function of heat treatment and Sn content. Martensitic transformation (bcc to orthorhombic structure) is accelerated at such quenching conditions that the bcc parent phase is slightly decomposed. Martensitic transformation temperature decreases rapidly with increasing Sn content. In-situ optical microscopic observation on cooling and heating indicates that the martensite is thermoelastic, corresponding to small temperature hysteresis between the martensitic and the reverse transformations, which is determined by differential scanning calorimetry. By controlling the heat treatment condition and Sn content, large superelastic strain is obtained at room temperature.

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This paper presents valuable evidence in support of the removal of a contaminant hydrocarbon layer adsorbed on photocatalytic TiO2 film by the latter's photo-oxidization. UV light was radiated on an anodic TiO2 film in an atmosphere-controlled chamber, and the film was then transferred to an ultrahigh-vacuum chamber for X-ray photoelectron spectroscopic (XPS) analysis; during the transfer, care was taken to ensure that the film was not exposed to air. This "in situ" setting eliminates the influence of carbon and water adsorptions during the transfer, thus enabling the accurate analysis of the UV-induced surface reaction. The spectral and quantitative results clearly revealed that the adsorbed hydrocarbon was removed from the photocatalytic TiO2 film when the film was irradiated in an oxygen atmosphere. Such removal occurs only in the case of TiO2 films that exhibit superhydrophilicity. This indicates that the removal of hydrocarbon is dependent on the UV-induced hydrophilicity on the film. In situ XPS measurement also presented evidence for UV-induced hydroxide group adsorption, where the adsorption was observed on both the surfaces showing superhydrophilicity and devoid of it.