• RUI LIU

      Articles written in Bulletin of Materials Science

    • Optimization of process conditions for the production of TiO2–𝑥N𝑦 film by sol–gel process using response surface methodology

      Rui Liu Ching-Shieh Hsieh Wein-Duo Yang Hui-Yi Tsai

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      TiO2–𝑥N𝑦 film has been synthesized successfully through the sol–gel method. It is found that the anatase phase is formed at 400 °C and converted to rutile phase at 600 °C. The response surface methodology (RSM) and Box–Behnken design were employed to optimize the process conditions of sol–gel process. Based on the results in preliminary experiments, we selected molar ratio of surfactant to Ti, molar ratio of acetylacetone to Ti, molar ratio of water to Ti and calcination temperature as the key process factors affecting the roughness of TiO2–𝑥N𝑦 film. The adjusted determination coefficient ($R^{2}_{\text{Adj}}$) of the regression model was 0.9651, which indicated that the regression model is significant. By analysing the contour plots of response surface as well as solving the regression model, the optimized conditions were obtained as: 0.19 for molar ratio of surfactant to Ti, 2.01 for molar ratio of acetylacetone to Ti, 1.38 for molar ratio of water to Ti and 500 °C for calcination temperature. The predicted roughness of TiO2–𝑥N𝑦 film for the optimized condition was calculated to be 41 nm. Confirmation experiments using the optimized conditions were performed, and a value about 43 nm was obtained. The experimental results are in good agreement with the predicted results.

    • Effects of calcination temperatures on the morphology, architecture and dielectric properties of BCZT ceramics

      RUI LIU YINGJIE QIAO XIAOHONG ZHANG CHEN-XI LU

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      (Ba$_{0.85}$Ca$_{0.15}$)(Zr$_{0.1}$Ti$_{0.9}$)O$_3$ (BCZT) ceramics were prepared by a simple sol–gel method. The effects of calcining temperature on the formation of BCZT ceramics were investigated in detail. The morphological changes and phase transformation of BCZT ceramics were analysed by X-ray diffraction and scanning electron microscopy. It is found that the calcined temperature determines the formation of a crystal phase, crystallinity and grain size. For dielectric properties, dielectric constant was increased first, and then decreased with increasing calcination temperature, in which the maximumdielectric constant of 2732 was achieved at 650$^{\circ}$C under a low-frequency alternating electric field. This may be attributed to the high crystallinity, density and fewer surface defects of BCZT ceramics. The optimum calcination temperature helps to understand the dielectric properties, which indicates that BCZT ceramics are promising lead-free candidates for widely used lead-based piezoelectric materials.

    • Photodegradation of methylene blue over a new down-shifting luminescence catalyst

      RUI LIU TAO LIU YINGJIE QIAO YONGCHAO BIE YINGJIN SONG

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      TiO$_2$ nanotube arrays prepared by anodization technology are modified with a samarium ion (Sm$^{3+}$) by a hydrothermal method for use in photodegradation of methylene blue (MB). The samarium ion as a down-shifting luminescence material can improve UV radiation harvesting to increase visible light utilization. The efficiency of the photocatalytic activity for the modified-TiO$_2$ nanotube arrays in degradation of MB was investigated under UV–Vis light irradiation. The results show that Sm–TiO$_2$ nanotubes can increase the photocatalytic efficiency of MB. When TiO$_2$ nanotubes are modified by 0.02 M Sm$^{3+}$, MB can be almost completely degraded when compared with bare TiO$_2$ nanotubes. This indicates that TiO$_2$ nanotubes structure, surface area and good UV radiation harvesting play important roles in the degradation of MB.

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