Wang Huihu

First-principles study on the synergistic effects of codoped anatase TiO2 photocatalysts codoped with N/V or C/Cr

An effective compensated codoping approach is described to modify the photoelectrochemical properties of anatase TiO2 by doping with nonmetals (N or C) and transition metals (V or Cr) impurities. Here, compensated codoped TiO2 systems are constructed with different dopant species and sources, and then their dopant formation energies and electronic structures are performed to study the stability and visible-light photoactivity by first-principles plane-wave ultrasoft pseudopotential calculations, respectively. The calculated results demonstrate that the codoping with transition metals facilitates the enhancement of the concentration of p-type dopants (N and C) in a host lattice. Especially, compensated codoping not only reduces the energy gap, to enhance the optical absorption, and eliminate the local trapping, to improve carrier mobility and conversion efficiency, but it also keeps the oxidation-reduction potential of the conduction band edge. These results are conducive to the understanding of the synergistic mechanism of the photocatalytic activity of TiO2 that is enhanced by codoping.

Thermal Shock Failure Mechanism of Nanostructured Zirconia Coating by Atmospheric Plasma Spraying

Abstract Nanostructured zirconia coatings has been prepared based on reasonable spraying technical parameters and the corresponding thermal shock property of the as-sprayed coating was examined at 1100 °C. The structure and the surface/interface morphology of the coatings have been analyzed using X-ray diffraction (XRD), metallographic microscope, scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and transmission electron microscopy (TEM). Based on the detailed analysis of the structure and phase composition, a rational mechanism has been proposed for thermal shock failure of the coating. Compared with other nanoparticles, those particles close to pores and pre-existing microcracks would preferentially grow up during the thermal shock process due to a better growth space. The growth of these nanoparticles is conducive to the formation of new microcracks which would lead to the growth of the other nanoparticles. With the growth of most or all of the nanoparticles, the nanostructured zirconia coating correspondingly changes into the quasi-microstructured coating. The thermal shock failure mode of the as-sprayed coating is similar to that of traditional zirconia thermal barrier coatings (TBCs).

Effects of Preparation Parameters and Alloy Elements on the Hydrogen Generation Performance of Aluminum Alloy-0°C Pure Water Reaction

Abstract Aluminum (Al) alloys with gallium (Ga) and indium (In) were prepared via mechanical alloying technology. The hydrolysis reaction between the Al alloys and pure water was studied to analyze the hydrogen yield evolution. The results obtained by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy show that Ga and In elements mainly exist in the alloy in the forms of dissolution and precipitated phases, respectively. The dissolution of Ga and In can improve the hydrogen yield of Al alloy by enhancing the activity of hydrolysis reaction. Moreover, the quantity and distribution of precipitated phase determined by ball milling time directly influence the hydrogen yields, and the Al alloy with appropriate number and uniform-distributed precipitated phase can react with 0 °C pure water to produce 1132.8 mL/g hydrogen.