Yao Gang Li

Observation of Cu2ZnSnS4 thin film prepared by RF magnetron sputtering for heterojunction applications

In this paper, copper-zinc-tin-sulfide (Cu2ZnSnS4) thin film was successfully fabricated by radio-frequency (RF) magnetron sputtering on glass substrate. The structural, optical and electrical properties of the film were studied by X-ray photoelectron spectroscopy (XPS), laser micro-Raman spectrometer, field emission scanning electron microscope (FESEM), UV-VIS spectrophotometer and Hall effect measurement, respectively. The results show that Cu2ZnSnS4 film is of good quality. A good nonlinear rectifying behavior is obtained for the GZO/Cu2ZnSnS4 heterojunction. Under reverse bias, high photocurrent is obtained.

Anatase TiO2 Colloids Derived from the Peptization of TiO2 Precipitates with CF3COOH and their Photocatalytic Activities

The highly dispersed TiO2 sols composed of anatase crystallites (ca.5 nm) were prepared by peptization of amorphous precipitates with trifluoroactic acid (TFA) during the synthesis. The size and crystallinity of the particles were tuned by the subsequent hydrothermal treatment. The prepared TiO2 nanocrystals were characterized by X-ray diffraction and transmission electron microscopy (TEM). The TEM results indicated that the growth of the crystallites could be inhibited by the increasing addition of TFA and the average sizes of TiO2 nanocrystals were all ultrafine. The degradation of phenol over the nanocrystals after calcination at 500 °C was investigated. The photocatalytic results showed that the sample with a high addition of TFA obtained a better photocatalytic property than that of the commercial TiO2

Fast Synthesis of Rutile/Apatite Core/Shell Structured Photocatalyst in Simulated Body Fluid

The core/shell structured rutile/apatite was prepared by soaking rutile TiO2 (R-TiO2) microspheres into a simulated body fluid (SBF) only for 1 day. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and N2 adsorption measurements. XRD showed that the apatite content increased with prolonging the soaking time or increasing the SBF concentration. TEM and EDX demonstrated that apatite had been coated on the surface of R-TiO2 microspheres successfully. HRTEM indicated that the lattice spacings of 0.27 nm and 0.32 nm were assigned to (211) plane of apatite and (101) plane of R-TiO2, respectively.

Synthesis and characterization of the PANI/ITO conducting nanocomposites

The PANI/ITO conducting nanocomposites have been synthesized by in-situ polymerization. The obtained nanocomposites were characterized by X-ray diffraction pattern, scanning electron microscopy and Fourier transform infrared. Electrical conductivity measurements on the samples pressed into pellets showed that the maximum conductivity attained 2.0 ± 0.05 S/cm for PANI/ITO nanocomposites, at ITO doping concentration of 10 wt%. The results of the present work may provide a simple, rapid and efficient approach for preparing PANI/ITO nanocomposites.

Hot-Pressed TiB2 Ceramics with B4C and C Additives

Effects of B4C and C additives on the densification behavior, phase composition, and microstructure of TiB2 ceramics were studied. The relative density of pure TiB2 ceramics by hot pressing at 2000°C for 1 h was only 77.4%. With the introduction of B4C and C additives, the relative density increase to 97.4% and 98.1%, respectively. The great improvement on densification was due to the removal of surface oxides of TiB2 powders by reaction with B4C and C additives. Microstructure observation showed the addition of B4C led to some TiB2 grains abnormal growth (>10 µm), whereas the addition of C produced a uniform and fine-grained microstructure.

A Single-Phase Full-Color Ca4Si2O7F2:Ce3+, Tb3+, Sm3+ Micron Belt Mat for White-Light Emitting Diode Application

A new kind of Ca4Si2O7F2:Ce3+, Tb3+, Sm3+ oxyfluoride phosphor micron belt mat was obatained by simply electrospinning process and subsequent heat treatment. XRD result shows that a pure Ca4Si2O7F2 phase can be obtained at low temperature of around 900 °C. The micron belt precursor has a smooth surface and uniform morphology, and the width and thickness of the belt is about 2 μm and 200 nm. The morphology of micron belt is well retained after heat treatment, forming a plat phosphor mat consisting of uniform micron belt network. Ca4Si2O7F2:Ce3+, Ca4Si2O7F2:Tb3+, and Ca4Si2O7F2:Sm3+ exhibit the characteristic emissions of Ce3+ (4f7→4f65d1, blue), Tb3+ (4f8→4f75d, green), and Sm3+ (4f6→4f65d, red) under the excitation of near-UV light, respectively. By adjusting the doping concentration of Ce3+, Tb3+, Sm3+ ions a white emission in a single phase was obtained under the excitation of 360 nm. We have demonstrated that Ca4Si2O7F2:Ce3+, Tb3+, Sm3+ phosphor mat can be a promising candidate for a color-tunable phosphor mat applied in a near-UV White light emitting diodes.

Synthesis of Bi0.5Sb1.5Te3/Graphene Composite Powders

In this paper, Bi0.5Sb1.5Te3/graphene composite powders were prepared by hydrothermal synthesis method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to characterize the morphology and structure of the composite powders. As a nanocomposite phase, graphene provided plenty of charge carriers and active sites for nucleation of Bi0.5Sb1.5Te3 grains. Bi0.5Sb1.5Te3 particles aggregated and attached to the surfaces of graphene randomly. In addition, it was found that the sizes of Bi0.5Sb1.5Te3 particles varied with different content of graphene. The formation mechanism of Bi0.5Sb1.5Te3/graphene composite powders was discussed.

Preparation of High Performance Pt Counter Electrodes on Conductive Plastic Substrate for Flexible Dye-Sensitized Solar Cells

Pt counter electrodes (CE) were been prepared using ion sputtering method on indium-doped tinoxide coated polyethylene terephthalate (ITO-PET) for flexible dye-sensitized solar cells (DSSCs). The effect of sputtering time on the properties was characterized by Feld emission scanning electron microscope (FESEM), electrochemical impedance (EIS) and UV-vis absorption spectra. The flexible CE show increased catalytic activity but reduced transmittance when the sputtering time is increased from 0 to 80 s. The light-to-electricity conversion efficiency of the DSSCs assembled with the high catalytic activity flexible CE attained a conversion efficiency of 4.0% by using Ti foil as the photoanode substrate under the simulated AM 1.5 sunlight. The results reveal that ion sputtering is an effective method for depositing platinum nanoparticles on plastic substrates with low cost under room-temperature.

Preparation and Properties of Zn1-XCoxO Magnetic Microspheres

Zn1-xCoxO magnetic microspheres have been synthesized by a simple solvothermal process. Different Co2+ dopant concentrations have been used as modifier and proved to be efficient at controlling the morphology and magnetic property of Zn1-xCoxO microspheres. The as-synthesized samples are characterized by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, photoluminescence spectrophotometer and vibrating sample magnetometry. Magnetic hysteresis loops reveal the samples exhibit ferromagnetic loops at room temperature. The meta-saturation magnetization value and coercivity of Zn0.8Co0.2O reach 0.09 emu·g-1 and 15.0 Oe.

Synthesis of Ultrafine MgAl2O4 Powders by Nitrate-Citrate Sol-Gel Combustion Process

Ultrafine MgAl2O4 powders were synthesized by a nitrate-citrate sol-gel combustion process using Al(NO3)3·9H2O, Mg(NO3)2·6H2O and C6H8O7·H2O as initial materials. The result of X-ray diffraction (XRD) analysis indicated that single-phase MgAl2O4 powder could be obtained at 850 oC, which is much lower than that needed in solid-state reactions. Transmission electron microscopy image showed that the as-prepared powder was in the nano scale and little agglomerate exited. It is concluded that this process need shorter time, lower temperature, and simple equipments.