Tongxiang Liang

Influence of oxidation time on microstructure and composition of micro-arc oxidation coatings formed on zirconium

Abstract Zirconia ceramic coatings on zirconium were prepared by micro-arc oxidation (MAO) method in mixed electrolyte of calcium glycerophosphate and calcium acetate. Effect of oxidation time on microstructure, element composition and phase composition of the coatings were analysised by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, respectively. The elemental composition of the coatings included Zr, O, Ca, and P. As oxidation time increased, Ca and P content of coatings correspondingly increased, and content of Zr reduced. The fabricated coatings with thickness from 20 to 30 μm were composed of c-ZrO2 and t-ZrO2, only trace amounts of m-ZrO2 phase were detected. Owing to the porous structure and components of coatings, ZrO2 coatings prepared by this method may provide available possibilities applied to biomedical materials.

CO adsorption on TiO2 nanomaterials: nanoparticles, nanotubes and nano-surfaces

Abstract The adsorption and oxidation behaviour of CO on different structural TiO2 has been analysed based on the density function theory first principle calculation. For zero-dimensional structure of nanoparticles, a high-specific surface area and onefold oxygen atoms on the surface result in a high rate of adsorption and oxidation for gas molecules. However, for one-dimensional nanotubes, CO molecules are physisorbed because of the absence of coordinatively unsaturated Ti4+ or basic O2− sites on it. But with advantages of lower levels of recombination of charge carriers, chemical adsorption may happen after illumination by the presence of adsorbate states in the band gap of the TiO2 nanotube upon light adsorption. Two-dimensional surfaces with onefold oxygen atoms or hole-assisted surface planes have stronger adsorption and oxidation ability.