Kai Du

Fabrication of ordered ZnO/TiO2 heterostructures via a templating technique.

Two kinds of ordered ZnO/TiO2 heterostructures were fabricated via a facile approach. The architecture of the TiO2 substrate could be controlled by alternating the filling forms of the template, and the morphology of the secondary ZnO nanostructure could be further tuned by adjusting the parameters of the hydrothermal reaction. Then two different morphologies of ZnO/TiO2 heteroarchitectures with ZnO nanorods and nanoplates growing on TiO2 shells and bowls were successfully achieved, respectively.

Structural properties and electrochemical behavior of cone-like TiO2: emphasizing the contributions of structure and spatial arrangement to lithium storage

A novel structure of anatase TiO2, nanocone-like TiO2 (TiO2-NC), is successfully prepared by a simple liquid-phase deposition method and is used as an anode material. The morphology and spatial arrangement of the TiO2-NC greatly affects the lithium storage, and TiO2-NC achieves a sustained high lithium storage performance (254.7 mA h g−1, corresponding to Li0.76TiO2) by assembling the TiO2-NC into ordered spherical shells. The structural analysis shows that exposed {001} facets of nanosized TiO2-NC help to increase the surface area as well as shorten the diffusion path of lithium transport. Moreover, an ordered arrangement of the TiO2-NC with a channel structure can further increase the surface area and improve the diffusion of the electrolyte, hence enhancing the lithium storage. Electrochemical tests indicate that the bulk intercalation of lithium was accompanied by the phenomenon of interfacial lithium storage in the TiO2-NC. In addition, the polarization of the TiO2-NC hollow spheres is effectively inhibited due to the ordered structure providing comfortable channels for the ionic and electronic diffusion, which imparts improved rate performance.

Thermo-catalytic decomposition of formaldehyde: a novel approach to produce mesoporous ZnO for enhanced photocatalytic activities

A novel method, thermo-catalytic decomposition of formaldehyde, is used to synthesize mesoporous ZnO crystals with enhanced photocatalytic activities. The mechanism of the mesoporous formation is investigated by synthesizing a series of samples at various systems and characterizing them with FT-IR, EDS, XRD, SEM, and TEM. The results show that formaldehyde can be adsorbed on the crystal planes of ZnO during the crystal growth and can then be catalytically decomposed into CO, CO2 and H2 during a sintering process. Because of the formation and the escape of these gases, which act as templates, the crystalline particles of ZnO are forced to rearrange consistently, and pores are formed in the internal crystal. Also, porous TiO2 crystals have been obtained via the same approach. Photocatalytic tests indicate that a porous ZnO crystal has higher activity than that of a nonporous one.

Preparation of Carbon Fiber/MoS2 Core-Shell Structure by Surface Modification and Precipitation Process in Aqueous Solution

A core-shell structure material, carbon fiber/MoS2 was prepared by a surface modification precipitation process in aqueous solution. A nucleation model for this structure was proposed. Coating was obtained from 10-4M ammonium molybdate. The energy band gap of MoS2 calculated from the absorption spectra was about 1.97eV. CFs/MoS2 core-shell structure has strong absorption in the wavelength range from 400 to 1000nm, which is well fitted to visible light of the solar spectrum. The result of thermal analysis indicates that the composite is stable below 403 °C.

The Pressure Performance of a Slide-Style Multianvil Large Volume Press

A slide-style 6-8 multianvil high pressure apparatus which has a better synchronicity and smaller step difference uncertainty has been developed in recent years. The second-stage pressure-generating system was established successfully. The cell pressures for 18/8, 14/8, 12/6, 10/4, 8/3 assemblies have been calibrated by using fixed point method at room temperature. The 8/3 assembly has an excellent pressure efficiency and could be obtained 22.5GPa with only 250 ton loading force. The size of gaskets and performance of transmitting medium have a great influence on cell pressure. Semi-sintered MgO (porosity 40%) medium is more excellent than pyrophyllite in performance of transmitting pressure.

Photoluminescence Properties of β-SiC Nanoparticles by Electric-Pulses Discharge in Liquid-Phase Compound

β-SiC nanoparticles have been synthesized by electric pulses discharge (EPD) in Hexamethyl disilane. Dependence of photoluminescence (PL) from the samples with air-annealing are presented. Emission bands around 400 nm and 470 nm are observed at room temperature. The corresponding PL properties and possible mechanisms are discussed. The 400 nm peak may be result from the atom excess defect center at the surfaces of β-SiC nanocrystallites, while the 470 nm peak is believed to be related to the defects created in the interface boundary between β-SiC nanocrystallites and amorphous SiO2.

Synthesis of MoO3 Nanostructures by a Solution Method

Synthesis and characterization of microsheets, microrods, microflowers and microspheres of orthorhombic phase molybdenum oxide (MoO3) were reported. The reaction between ammonium molybdate and hydrochloric acid was used to prepare MoO3 microstructures and followed by annealing in air at 400oC for 2h. The combined techniques of X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and Raman spectroscopy were used to investigate the effect of pH and additives on the as-prepared samples. Results indicated that they were of microsize. With alcohol as an additive, the sample was plate-like MoO3 at pH=2.5, and it was a mixture of MoO3 and MoO3•0.55H2O of irradiative corolla at pH=1. The sample obtained by hydrothermal was MoO3 flowers. Meanwhile, when silane coupling agent was introduced as the additive, the sample was MoO3 spheres.

Preparation and Optical Properties of Carbon Fiber/ZnO Core-Shell Structure by a Simple Method

A core-shell structure material, carbon fiber/ZnO was prepared by a surface modification precipitation process in aqueous solution. The structure, absorptive properties and photoluminescence properties of the composites were investigated. Results showed that the energy bandgap of samples calculated from the absorptive spectra was about 3.30eV. The green emission peak of the samples was ascribed to the oxygen vacancies.

Synthesis of MoO3 Nanorods by a Solution Method

MoO3 nanorods were synthesized by a solution method with stirring and ultrasound. The formation temperature of MoO3 nanorods were studied by XRD. The particle-size and morphology were characterized by TEM. The diameter of nanorods was ca. 60nm.