Yuming Tian

Synthesis of Cu2O/ZnO hetero-nanorod arrays with enhanced visible light-driven photocatalytic activity

Vertically aligned Cu2O/ZnO hetero-nanorod arrays were synthesized on indium-doped tin oxide (ITO) glass substrates using a simple hydrothermal method followed by an electrodeposition process. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) results show that Cu2O nanoparticles conformably formed on the pre-grown ZnO single-crystalline nanorods. Compared to pure Cu2O and pure ZnO nanorod array films, the Cu2O/ZnO hetero-nanorod array films exhibit an excellent improvement in photocatalytic applications under visible light irradiation. The increase of the electrodeposition time (amount) of Cu2O helps to enhance the photocatalytic activities of the system until the Cu2O nanoparticles nearly cover the entire periphery of the ZnO nanorods. The enhanced photocatalytic activity is attributed to better light scattering for the Cu2O/ZnO hetero-nanorod array structure and fast charge separation and transport within the heterojunctions of the Cu2O/ZnO.

Chemical bath deposition of Cu2O quantum dots onto ZnO nanorod arrays for application in photovoltaic devices

Cu2O quantum dots (QDs) decorated ZnO nanorod arrays (ZNAs) were fabricated using a facile hydrothermal method followed by a chemical bath deposition (CBD) process. The surface morphology, crystal structure and photovoltaic behaviors of the heterostructure films were investigated. The results indicate that the Cu2O QDs decorated ZNAs can be used as a good light absorber improving the visible spectral absorption. In addition, the photo-induced electrons can easily transfer to ZnO, leading to an increase in the photovoltaic performance. When the number of CBD cycles was 10, an optimal photovoltaic performance could be obtained under simulated sunlight illumination (AM 1.5G, 100 mW cm−2) with a photocurrent of 3.21 mA cm−2, an open circuit photovoltage of 0.65 V and a conversion efficiency of 1.17%. Moreover, for improving the photovoltaic stability, a protective layer was prepared on the Cu2O QDs by a simple process of heat treatment in ambient air at 100 °C for 2 h. The results demonstrate that the passive CuO layer could be an effective protective layer to increase the photovoltaic stability.

Solution combustion synthesis and enhanced gas sensing properties of porous In2O3/ZnO heterostructures

Self-assembled porous In2O3/ZnO heterostructures were prepared by a low temperature solution combustion synthesis method, and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The results indicate that the as-synthesized porous In2O3/ZnO heterostructures were constructed from a large number of In2O3 and ZnO nanoparticles and showed high gas sensing performance toward Cl2. Compared with pure ZnO and other heterostructure sensors, the porous In2O3/ZnO heterostructures with an appropriate molar ratio of In2O3 : ZnO exhibited highly enhanced gas sensing performances toward Cl2. An extremely high sensitivity of 6610 could be reached when exposed to 50 ppm Cl2 at 370 °C; also, In2O3/ZnO heterostructures showed high selectivity toward Cl2. Furthermore, the gas sensing mechanism was discussed.

Preparation and characterization of low-cost high-performance mullite-quartz ceramic proppants for coal bed methane wells

Abstract In this study, the mullite-quartz-based proppants were successfully prepared by using the coal gangue as the raw materials. Then, the effects of the additive and the sintering temperature on the composition, microstructure, and properties of the proppants were investigated. Results showed that the proppants sintered at 1250°C with the 10 wt% bauxite additive presented the best performance, which was very close to that of the quartz-proppant, and met the operational requirements of the 52 MPa coal bed methane wells. The viscous flow mechanism of the liquid phase formed during the sintering process also promoted the arrangement of the grains, thus benefiting the densification and the strength of the proppants.

Preparation and characterization of low-density ceramic proppant containing coal gangue additive

Abstract Low-density ceramic proppants were prepared from calcined flint clay and solid waste coal gangue by pelleting, drying, screening and sintering, namely solid state sintering method. The density and breakage ratio of the proppants were systematically investigated as a function of sintering temperature. The morphology and phase composition of the proppants were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the ceramic proppants are composed of acicular mullite and granular cristobalite. Bulk density and apparent density of the proppants rise and thereafter down with increasing the sintering temperature. The proppants sintered at 1400 °C have the best performance with 1.28 g/cm3 of bulk density, 2.84 g/cm3 of apparent density and 7.89% of breakage ratio under 52 MPa closed pressure. The prepared ceramic proppants meet China industrial standard requirements SY/T5108-2014.

Feasible Recycling of Industrial Waste Coal Gangue for Preparation of Mullite Based Ceramic Proppant

Industrial waste coal gangue was successfully utilized to prepare the mullite-based ceramic proppants. The experiments involved the pelletizing technology of proppant through intensive mixer and following the sintering process under different temperatures. The crystalline phase, microstructure, density and breakage ratio of the proppants were investigated. The results showed that with the increasing of sintering temperature, the crystalline phases were transformed to rod-like mullite, which formed the cross-linked structure, improving the densification of proppants. Consequently, the breakage ratio under the closure pressure of 35 MPa exhibited declining trend and reached the minimum value of 6.8% at 1450 °C. Owing to the easy preparation, feasible design, low cost and moderate breakage ratio, the mullite-based ceramic proppant prepared by coal gangue and bauxite is promising candidate for fracturing proppants in future applications.