Engineering topics
Wang, Zumin
Publications and source records attributed to Wang, Zumin.
Controlled synthesis of silkworm cocoon-like α-Fe2O3 and its adsorptive properties for organic dyes and Cr(VI)
Highlights: • A hierarchical structured α-Fe{sub 2}O{sub 3} is synthesized by using a simple hydrothermal method. • The as-synthesized α-Fe{sub 2}O{sub 3} shows high adsorption capacities for CR, MO and Cr(VI) ions. The removal efficiency can reach up to 99.2%, 83.9% and 100% under the given conditions. • This kind of material realizes synergistic adsorption of organic and inorganic pollutants. And the adsorption efficiency can reach 94.7% for CR and 97.9% for Cr(VI) ions in a mixed solution. - Abstract: Industrial wastewater containing both organic and inorganic pollutants is being generated all the time. Efficient materials are highly needed to purify the polluted water. Thus, a hierarchical structured α-Fe{sub 2}O{sub 3} with excellent adsorptive property has been synthesized by using a facile hydrothermal method. It can be prepared in macroscopic quantity. The as-synthesized α-Fe{sub 2}O{sub 3} with silkworm cocoon-like morphology shows high efficiency in adsorbing Congo red (CR), Methyl orange (MO) and Cr(VI). The removal efficiency of CR, MO and Cr(VI) can reach 99.2%, 83.9% and 100% under appropriate conditions. Besides, this α-Fe{sub 2}O{sub 3} shows high adsorptive ability for mixed CR and Cr(VI) in aqueous solution and the final removal rates can reach 94.7% and 97.9%, respectively. The adsorption kinetics fits well with the pseudo-second-order kinetic model. The results indicate that the product may find potential application in purification of wastewater containing both organic and inorganic pollutants.
Construction of multi-shelled Bi2WO6 hollow microspheres with enhanced visible light photo-catalytic performance
Highlights: • Bi{sub 2}WO{sub 6} with multi-shelled hollow microstructure was successfully fabricated and the use of ethylene glycol is a key factor. • Bi{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6} composite with multi-shelled hollow structure were also fabricated when concentration of solution was reduced. • Enhanced visible light photocatalytic performance was observed, which are believed due to the unique hollow microstructure. - Abstract: As a promising structure in enhancing the photo-catalytic performance of the materials, hollow-shell structure still faces the great challenge of constructing an effective architecture for catalytic application. Herein, multi-shelled hollow microspheres of the visible-light photo-catalyst Bi{sub 2}WO{sub 6} with shells up to the triple (BWO-MSH), have been synthesized by using a facile and effective carbonaceous template route. Intriguingly, the photo-catalytic reaction rate constant of BWO-MSH sample is nearly 16 times higher than the Bi{sub 2}WO{sub 6} prepared through solid-state reaction (BWO-SSR). The single-, double-shelled Bi{sub 2}WO{sub 6} microspheres (Broken) could only be synthesized with lower quality (synthesized with many broken species), and their photo-catalytic performance was nearly the same poor as the BWO-SSR sample. Furthermore, multi-shelled hollow microsphere of Bi{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6} (BO/BWO-MSH) composite was also synthesized. The present work not only extends the scope of high-performance complex mixed metal oxides with multi-shelled microstructures, but also brings a good reference to engineer other impressive photo-catalyst.
Interdiffusion and stress development in single-crystalline Pd/Ag bilayers
Interdiffusion and stress evolution in single-crystalline Pd/single-crystalline Ag thin films were investigated by Auger electron spectroscopy sputter-depth profiling and in-situ X-ray diffraction, respectively. The concentration-dependent chemical diffusion coefficient, as well as the impurity diffusion coefficient of Ag in Pd could be determined in the low temperature range of 356 °C–455 °C. As a consequence of the similarity of the strong concentration-dependences of the intrinsic diffusion coefficients, the chemical diffusion coefficient varies only over three orders of magnitude over the whole composition range, despite the large difference of six orders of magnitude of the self-diffusion coefficients of Ag in Ag and Pd in Pd. It is shown that the Darken-Manning treatment should be adopted for interpretation of the experimental data; the Nernst-Planck treatment yielded physically unreasonable results. Apart from the development of compressive thermal stress, the development of stress in both sublayers separately could be ascribed to compositional stress (tensile in the Ag sublayer and compressive in the Pd sublayer) and dominant relaxation processes, especially in the Ag sublayer. The effect of these internal stresses on the values determined for the diffusion coefficients is shown to be negligible.
Concentration-dependent self-diffusion coefficients in amorphous Si{sub 1−x}Ge{sub x} solid solutions: An interdiffusion study
Self-diffusion coefficients of Si and Ge in amorphous Si{sub 1−x}Ge{sub x} (a-Si{sub 1−x}Ge{sub x}) solid solutions were determined quantitatively in the temperature range of 440 °C – 460 °C by the investigation of interdiffusion in amorphous Si/Si{sub 0.52}Ge{sub 0.48} multilayers using Auger electron spectroscopy sputter-depth profiling. The determined concentration dependent self-diffusion coefficients of Si and Ge in a-Si{sub 1−x}Ge{sub x} with 0 ≤ x ≤ 0.48 at. % Ge are about ten orders of magnitude larger than in the corresponding crystalline phases, due to the inherent, excess free volume in the amorphous phase. The self-diffusion coefficient of Si (or Ge) in a-Si{sub 1−x}Ge{sub x} increases in association with a decreasing activation enthalpy with increasing Ge concentration. This concentration dependence has been related to an overall decrease of the average bond strength with increasing Ge concentration.