Facile synthesis of SnO<Subscript>2</Subscript> hollow microspheres and their optical property

SnO2 hollow microspheres were fabricated via a hydrothermal synthesis method assisting by the complex surfactant system of polyacrylamide and polyethylene glycol.Observation by field emission scanning electron microscopy (FESEM) showed the SnO2 hollow spheres were composed of nanoparticles.The growth mechanism for the formation of hollow spheres was proposed.UV spectroscopy and photoluminescence (PL) were used to investigate the optical properties of the products.The PL result showed that four peaks,containing the emission from recombination of free excitons,were observed in the photoluminescence spectrum.     

石墨烯/SnO_2/聚苯胺纳米复合材料的制备与表征

石墨烯具有独特的纳米结构和一系列极具吸引力的特性,成为新型纳米复合材料的理想载体,如纳米复合材料分散的基体.提出了一种以石墨,苯胺,四氯化锡为原料制备石墨烯/二氧化锡/聚苯胺的新方法.通过X-射线衍射,红外光谱,透射电子显微镜,扫描电子显微镜以及紫外-可见光谱对合成的材料进行表征.结果表明：二氧化锡纳米粒子原位吸附在石墨烯的表面,有效地避免了石墨烯片的堆叠,聚苯胺加入后可大大提高二氧化锡的电化学性质.     

Synthesis and electrochemical properties of Mg-doped LiNi<Subscript>0.6</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.2</Subscript>O<Subscript>2</Subscript> cathode materials for Li-ion battery

The layered LiNi0.6Co0.2-xMn0.2MgxO2 (x=0.00,0.03,0.05,0.07) cathode materials were prepared by a co-precipitation method.The properties of the Mg-doped LiNi0.6Co0.2Mn0.2O2 were investigated by X-ray diffraction (XRD),scanning electron microscopy (SEM),and electrochemical measurements.XRD studies showed that the Mg-doped LiNi0.6Co0.2Mn0.2O2 had the same layered structure as the undoped LiNi0.6Co0.2Mn0.2O2.The SEM images exhibited that the particle size of Mg-doped LiNi0.6Co0.2Mn0.2O2 was finer than that of ...     

Synthesis and electrochemical properties of SnO2-polyaniline composite

The SnO2-polyaniline（SnO2-PAn） composite was prepared by microemulsion polymerization method using aniline, ammonium peroxodisulfate and SnO2 as starting materials. The SnO2-PAn composite was characterized by X-ray diffractometer, scanning electron microscope and electrochemical techniques. The results show that PAn in the composites is amorphous. PAn formed in the reaction is deposited preferentially on the SnO2 particles, giving a SnO2-PAn composite, in which SnO2 is coated with PAn. SnO2-PAn composite shows a reversible capacity of 657.6 mA.h/g and the capacity loss per cycle is only 0.092% after 80 cycles, suggesting that SnO2-PAn composite is a promising anode material for lithium ion batteries.     

Synthesis and electrochemical properties of SnO2-polyaniline composite

The SnO2-polyaniline(SnO2-PAn) composite was prepared by microemulsion polymerization method using aniline, ammonium peroxodisulfate and SnO2 as starting materials. The SnO2-PAn composite was characterized by X-ray diffractometer, scanning electron microscope and electrochemical techniques. The results show that PAn in the composites is amorphous. PAn formed in the reaction is deposited preferentially on the SnO2 particles, giving a SnO2-PAn composite, in which SnO2 is coated with PAn. SnO2-PAn composite shows a reversible capacity of 657.6 mA.h/g and the capacity loss per cycle is only 0.092% after 80 cycles, suggesting that SnO2-PAn composite is a promising anode material for lithium ion batteries.     

Microstructures and Properties of SiC／Al2O3 ／Al- Si Composites Prepared by Reactive Penetration

The composition, microstructures and properties of SiC/Al2O3/Al-Si composites formed by reactive penetration of the molten aluminum into the preforms of SiO2 and SiC were investigated. The composition of the composites was measured by X-ray diffraction ( XRD ). The microstructures of the composites were also measured by scanning electron microscopy (SEM) and optical microscopy. In addition, the factors affecting the properties of the composites were discussed. The experiments show that the mechanical properties of the composites depend on their relative densities and the sizes of the fillers“ SiC gains“. The denser the SiC/Al2O3/Al-Si composites, the higher their bending strength. As the filler “SiC gains“ become fine, the bending strength of the composites increases.     

Fluxing Agents on Ceramification of Composites of MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>/Boron Phenolic Resin

Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al₂O₃-SiO₂/boron phenol formaldehyde resin (MAS/BPF) composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS / BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS / BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS / BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.     

钛基二氧化锡纳米涂层的制备与改进

采用热分解法,制备了Ti/SnO2和添加活性元素的Ti/SnO2纳米涂层,并研究了涂层的结构与物化性能。结果表明:普通热分解方法可制备纳米二氧化锡涂层,其晶体结构为金红石结构;热氧化为500℃时,往Ti/SnO2涂层中添加Ru、Co能显著提高Ti/SnO2涂层的电催化性能,而添加La则无作用;制备的Ti/SnRuCo涂层,具有结合强度高、电催化性能好和孔隙率小的特点。     

Hierarchical Co<Subscript>3</Subscript>O<Subscript>4</Subscript> microstructures decorated with Ag and Cu oxides: Study of photocatalytic and electrochemical properties

Three-dimensional hierarchical Co₃O₄ microstructures decorated with Ag and Cu oxides were prepared via displacement reaction and subsequent annealing treatment. Photocatalytic properties measurements revealed that the photocatalystic activities of CuO/Co₃O₄ composites (Co₃O₄ microstructures decorated with CuO) were enhanced while those of Ag₂O/Co₃O₄ composites (Co₃O₄ microstructures decorated with Ag₂O) were reduced, when compared with those of pure hierarchical Co₃O₄ microstructures toward the degradation of methyl orange. In addition, CuO/Co₃O₄ composites exhibited an excellent recyclability ability of photodegradation. The electrochemical properties test indicated that both of the composite oxide electrodes exhibited excellent pseudocapacitive performance with relatively high specific capacitance and good long-term cycling stability. With the increase of the loaded Ag₂O and CuO dosages deposited on the Co₃O₄ microstructures surface, the specific capacitance values of the composites were increased. Ag₂O/Co₃O₄ composite electrodes showed higher specific capacitance values and better cycling stability than CuO/Co₃O₄ composite ones.     

Electrochemical Sensing of Heavy Metal Ions based on Monodisperse Single-crystal Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Microspheres

Single-crystal Fe₃O₄ with monodisperse microspheres structure has been used for individual electrochemical detection of heavy metal ions. Morphology and structure of the as-prepared Fe₃O₄ microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Meanwhile the electrochemical properties of the Fe₃O₄ microspheres modified glass carbon electrodes (GCE) were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the enhanced electrochemical response in stripping voltammetry for individual detection of Pb(II), Hg(II), Cu(II), and Cd(II) was evaluated using square wave anodic stripping voltammetry (SWASV). With high specific surface area and excellent catalytic activity toward heavy metal ions, the as-prepared monodisperse and single-crystal Fe₃O₄ microspheres show a preferable sensing sensitivity (22.2 μA/μM) and limit of detection (0.0699 μM) toward Pb(II). Furthermore, the electrochemical sensor of Fe₃O₄ microspheres exhibits excellent stability and it also offers potential practical applicability for the determination of heavy metal ions in real water samples. This study provides a potential simple and low cost iron oxide for the construction of sensitive electrochemical sensors applied to monitor and control the pollution of toxic metal ions.     

Sonochemical synthesis of core/Shell structured CdS/TiO<Subscript>2</Subscript> nanocrystals composites

A simple sonochemical route for the surface coating of titanium dioxide on cadmium sulfide nanocrystal was reported. After 2 h ultrasonic irradiation treatment, the mixture of CdS nanocrystals and tetrabutyl titanate in an aqueous medium yielded CdS/TiO₂ nanocrystals composites with core/shell structure. The thickness of TiO₂ layer with smooth interface could be easily controlled via changing the concentration of the precursors and the time of irradiation. The core/shell nanocrysrals were characterized by X-ray diffraction, transmission electron microscope and UV-vis spectrometry techniques. The prepared semiconductor composites with particular band structure present appealing properties especially in photochemical activity.     

Electrochemical properties of Nano-LiFePO<Subscript>4</Subscript> prepared by hydrothermal reaction

LiFePO4 nanorods were facilely synthesized under hydrothermal condition. The crystalline structure and particle morphology of LiFePO4 powders were characterized by X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The electrochemical properties of LiFePO4/Li cells were investigated by galvanostatic test and cyclic voltammetry (CV). The XRD result demonstrated LiFePO4 powder had an orthorhombic structure with a space group of Pnma. The synthesized LiFePO4 nanorods exhibited a...     

锂离子电池负极材料SnO2-Gn-C三元复合物的制备及其电化学性能

通过两步水热法合成了可用作锂离子电池负极材料的二氧化锡-石墨烯-炭（SnO2-Gn-C）三元复合物.采用X射线粉末衍射（XRD）、透射电镜（TEM）和电化学测试研究了SnO2-Gn-C复合物的晶型结构、形貌和电化学性能,并考察了反应温度和Sn/Gn物质的量比对复合物电化学性能的影响.实验结果显示,SnO2-Gn-C复合物在200mA· g-1电流密度下初始放电比容量达到1 225mA·h·g-1,50次充放电循环后比容量仍有约229mA.h·g-1.SnO2-Gn-C良好的电化学性能主要归结于大比表面积的石墨烯对SnO2纳米粒子的良好分散作用、石墨烯和炭的高导电性以及炭包覆后的复合物充放电时体积效应的显著减小.     

Synthesis and characterization of VO<Subscript>2</Subscript>/mesoporous carbon composites for hybrid capacitors

VO₂/ordered mesoporous carbon (CMK-3) composites were prepared by solid-state reaction process. The microstructures were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The experimental results showed that the vanadium oxide in the composites was vanadium dioxide (VO₂) with monoclinic structure, which was artificially loaded on the outer surface of CMK-3. VO₂/ordered mesoporous carbon composites present a significantly improved capacitive performance (131 F/g) increased by 40.86% compared to that of CMK-3 carbon (93 F/g). Therefore, as-prepared VO₂/mesoporous carbon composites suggest promising applications in hybrid capacitors.     

Synthesis and electrochemical properties of Cr-doped Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> cathode materials for lithium-ion batteries

Cr-doped Li₃V₂(PO₄)₃ cathode materials Li₃V_2−x Cr _x (PO₄)₃ were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li₃V₂(PO₄)₃ were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li₃V₂(PO₄)₃ has the same monoclinic structure as the undoped Li₃V₂(PO₄)₃, and the particle size of Cr-doped Li₃V₂(PO₄)₃ is smaller than that of the undoped Li₃V₂(PO₄)₃ and the smallest particle size is only about 1 μm. The Cr-doped Li₃V₂(PO₄)₃ samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Cr was that x=0.04 in the Li₃V_2−x Cr _x (PO₄)₃ samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li₃V₂(PO₄)₃ cathode materials are attributed to the addition of Cr³⁺ ion by stabilizing the monoclinic structure. Funded by the Guangxi Natural Science Foundation(No. 0832259) and the National Basic Research Program of China (No. 2007CB613607)     

Tensile properties of 3-Dimension-4-directional braided C<Subscript>f</Subscript>/SiC composite based on double-scale model

The longitude tensile properties of 3-Dimension-4-directional(3D-4d) braided C/SiC composites(CMCs) were investigated with the help of a double scale model. This model involves micro-scale and unit-cell scale. In micro-scale, the tensile properties of fiber tows which involves matrix cracking, interfacial debonding, and fiber failure are studied. The unit-cell scale model can reflect the braided structure and simulate the tensile properties of 3D-4d CMCs by introducing the tensile properties of fiber tows into it. Quasi-static tensile tests of 3D-4d braided CMCs were performed on a PWS-100 test system. The predicted tensile stress-strain curve by the double scale model is in good agreement with that of the experimental results.     

Effect of MnO<Subscript>2</Subscript> on properties of SiC-mullite composite ceramics for solar sensible thermal storage

For improving the properties of SiC-mullite composite ceramics used for solar sensible thermal storage, MnO₂ was introduced as sintering additive when preparing. The composite ceramics were synthesized by using SiC, andalusite, α-Al₂O₃ as the starting materials with non-contact graphite-buried sintering method. Phase composition and microstructure of the composites were investigated by XRD and SEM, and the effect of MnO₂ on the properties of SiC composites was studied. Results indicated that samples SM1 with 0.2 wt% MnO₂ addition achieved the optimum properties: bending strength of 70.96 MPa, heat capacity of 1.02 J·(g·K)^-1, thermal conductivity of 9.05 W·(m·K)^-1. Proper addition of MnO₂ was found to weaken the volume effect of the composites and improve the thermal shock resistance with an increased rate of 27.84% for bending strength after 30 cycles of thermal shock (air cooling from 1 100 °C to RT).     

Effect of salt spray corrosion on tribological properties of HVOF sprayed NiCr-Cr<Subscript>3</Subscript>C<Subscript>2</Subscript> coating with intermediate layer

The objective of the present work was to determine the influence of the neutral salt spray corrosion on the wear resistance of HVOF sprayed NiCr-Cr₃C₂ coating with intermediate layer. Ni-Zn-Al₂O₃ coatings as interlayers were prepared by low pressure cold spray (LPCS) between NiCr-Cr₃C₂ cermet coatings to form a sandwich structure to enhance the corrosion resistance properties. The tribological properties were examined using the UMT-3 fricition and wear tester by line-contact reciprocating sliding under dry and salt spray one week corrosion. The morphology, element distribution, and phase compositions of the coating and worn sufaces were analyzed by using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction respectively. The corrosion behavior of the coating was studied by the open-circuit potential, the electrochemical impedance spectroscopy, potentiodynamic polarization, and salt spray corrosion methods. It is found that the sandwich structured coating has better corrosion resistance than the single layer coating. The results show that under dry wear conditions, the wear mechanism is abrasive and adhesive wear, whereas under salt spray corrosion conditions it becomes corrosion wear. The friction coefficient of the sandwich structured coating after salt spray corrosion is slightly lower than the dry friction coefficient, but the weight of the wear loss is lower than that under dry condition.     

Fabrication of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-NaCl composite heat storage materials by one-step synthesis method

Thermal energy storage is an attractive option for effectiveness since it gives flexibility and reduces energy consumption and costs. New composite materials for storage and transformation of heat of NaCl-Al₂O₃ composite materials were synthesized by one-step synthesis method. The chemical composition, morphology, structure, and thermal properties were investigated by XRD, EDS, SEM, and DSC. The results show that NaCl can be absorbed by Al₂O₃ particle from 800 to 900 °C for Al₂O₃ particle surface is rich active structure. The results also indicate that the leakage of NaCl when the phase change can be prevented by Al₂O₃ particles and the enthalpy of phase change of NaCl-Al₂O₃ material is 362 J/g. The composites have an excellent heat storage capacity. Therefore, this study contributes to one new thought and method to prepare high temperature heat storage material and this material can be applied in future thermal engineering.     

Synthesis and Characterization of Polyaniline/MgTiO_3 Composite with Excellent Thermal and Electrochemical Performance

This article explores the effects of doping ferroelectric materials MgTiO_3 with different proportions on the properties of polyaniline (PANI).PANI / MgTiO_3 composites were prepared by in-situ composite method.Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to characterize the structure of the composites.Scanning electron microscope (SEM) was used to characterize the morphology of the composites.The thermal stability of the composites was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG).Electrochemical methods (cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS),and constant current charge-discharge test) were used to compare and analyze the electrochemical performance of the composites.TG-DTG analysis and electrochemical experiments all show that the thermal stability and electrochemical properties of the PANI / MgTiO_3 composite with a mass ratio of 82/18 (w/w) are the best.The results indicate that there is a synergistic effect between PANI and MgTiO_3,which improves the performances of the PANI when the appropriate amount of MgTiO_3 is added.