Papers by Author: Jing Ma

Abstract: The binding energy of anatase TiO2, in which the Ti was substituted by other transition metals in the 4th, 5th and 6th periods of the periodic system of the elements, has been calculated by using first principles method. The doping limits of V, Cr, Zr, Nb, Mo and W are 61.5%, 39.7%, 88.2%, 100.0%, 65.0%, and 63.2%, respectively predicted by the calculated binding energy, while the doping limits of other transition metals are much lower. So, these transition metals can easily be doped into the anatase structure theoretically while it is difficult for the others. And the band structure and density of states (DOS) of V, Cr, Zr, Nb, Mo and W doped anatase TiO2 have also been calculated and analyzed.

Abstract: TiO2 thin film was prepared on soda lime glass by hydrolysis of Ti(OC4H9)4 in alcoholic solutions by sol-gel method combined with spin-coating and calcination different temperatures. Prepared samples were characterized by XRD, FESEM, and measurement of contact angles and transmittance. XRD identification reveals that the films are composed of anatase TiO2 when the annealing temperature was set at 450~550 oC. SiO2 layer was coated on the surface of the glass firstly to barrier the diffusing of sodium ions from the substrate. Light-induced superhydrophilicity of the TiO2 thin film has been investigated. To increase the illumination light intensity will decrease the water contact angle. The superhydrophilicity of the TiO2 thin film will disappear more slowly in the dark than that in the field of ultrasound.

Abstract: Titanate nanotubes have been directly prepared by hydrothermally treating P25 powders in NaOH aqueous solution. Effect of calcination temperature on crystal phase, morphologies and specific surface area of the as-synthesized nanotubes has been investigated in detail. The Na2Ti3O7 tubular structure could be kept well even after calcination at 600 °C and began to transform to Na2Ti6O13 nanorods at around 645 °C. The specific surface area of the as-synthesized nanotubes was 200.6 m2/g and reached to the maximum of 347.9 m2/g after calcination at 300 °C and then decreased sharply with the further increase of the calcination temperature.

Abstract: It is shown from the oxidation results that, for Fe-Cr, Ni-Cr, Co-Cr binary alloys with and without internal Cr2O3 precipitations after exposure, continuous external Cr2O3 scales formed on their surfaces, especially at the initial stage. It is therefore suggested that the transitions of oxidation for these alloys take place from externally to internally. There are two types of transitions for alloys: (1) the transition from temporary external oxidation to internal oxidation; and (2) the transition from permanent external oxidation to internal oxidation. The thermodynamic conditions for these transitions have been analyzed, and the criterion for prediction of the minimum solute concentration of a binary solid solution alloy required for the second transition has been derived. It is also suggested that the external oxide scale is an important factor to determine the formation of pure solvent metal nodules on the surfaces.