Abstract:PbSe dendritic structures have been successfully synthesized by a facile hydrothermal route in glycerol solution without surfactant. Temperature, time, and Pb₂₊source play a major role in controlling the morphology and shape evolution of the product. The obtained products were characterized by X-ray power diffraction (XRD), Scanning electron microcopy (SEM) and transmission electron microscopy (TEM). This simple synthesis technique for the growth of various nano- and microstructures opens a new route to prepare hierarchical structures of a variety of semiconducting materials in a large quantity. The possible formation mechanism for products with various architectures are presented, which is mainly based on the variation of the ratio (R) of the growth rates along the <100> direction and <111> direction.

Abstract:Reducing graphene oxide suspension with amino agent can prepare N-containing graphene aerogels useful in many applications. This work studied the reaction process during the synthesis of N-doped graphene aerogels (NDGA) with p-phenylene diamine (PPD) as reducing and functionalizing agent based on the experimental and calculated results. The amino group in the PPD firstly reacts with the hydroxyl in the carboxyl for the strong electron-donating effect of carbonyl. Then the reaction happens between the amino group and the epoxy group. This reaction not only induces the forming of the pyrrolic N, but also changes the interlayer distance. The reaction process ideally explains the reasons for the structure and composition change during synthesis. This work provides a more thorough understanding of the reaction process during the synthesis of NDGA, which is significant for the optimization of the aerogels. And these findings are also useful for understanding the reaction process and reaction mechanisms during the synthesis of reduced graphene oxide aerogels with other amino agent as reductant.

Abstract:The TaC coatings were prepared by precursor slurry application and subsequent sintering processes on graphite substrate. The prepared coating were investigated with their phase composition and morphology, by means of XRD and SEM. The coating consisted of single-phase TaC and had a dense granular structure containing grain with the mean size of 12μm. The coating had an isotropic granular structure, which make the crack tip would be pinned at a grain boundary junction and would not fully penetrate the coating. The hardness and the plastic modulus of the coating are 15.35GPa and 195.1GPa, respectively.

Abstract:Using the Baoxi clay which was strenthened by Al2O3 as the main materials. And then import the ZrO2(Y2O3) powder that made by the sol-gel method. Studied the microstructure and mechanical properties by the addition of the ZrO2(Y2O3) . The result shows that, with the increasing of ZrO2(Y2O3) content the body strength improves at first but declines afterward . While the content of ZrO2(Y2O3)was 2% in the Baoxi clay with 22%α-Al2O3, the sample shown the max bending strength and most compact volume density. The strengthen mechanism was stress-induced transformation toughening.

Abstract:Diyao Longquan celadon body was enhanced by introducing silica sol. Influence of silica sol addition on microstructure and mechanical properties was investigated. The results show that, the silica sol uniformly distributes on the surface of the raw material particles,generates high activity ultrafine silica during fire process, which reacts with alumina and formats Mullite to achieve body enhancement. With the increase of the amount of silica sol, bending strength and sintering shrinkage increased firstly and then decreased. When the silica sol addition is 2%, Diyao Longquan celadon body sample achieves maximum bending strength and shrinkage .

Abstract:TiO₂ nanotubes were prepared through hydrothermal method with TiO₂ power in high concentration NaOH solution. XRD, SEM, TEM and UV-Vis were adopted to analyze as-prepared TiO₂ nanotubes. The influence of the factors, such as NaOH concentration, reaction time and temperature, on the structure and properties of TiO₂ nanotubes were investigated. The results show that the uniform TiO₂ nanotubes are obtained under optimum preparation conditions: 10mol/L of NaOH, 20h of reaction time and 160℃ of reaction temperature. TiO₂ nanotubes exhibit higher photocatalytic activity, and the degradation rate of methyl orange (MO) in aqueous solution reached 75.48% after UV irradiation for 30 min.

Abstract:Intermediate Ag-60SnO₂In₂O₃powders were synthesized by in-situ oxidation and traditional oxidation process with Ag-65SnIn-8 melting atomization powder as raw material, Ag-92SnO₂In₂O₃materials were prepared by mixing-isostatic press and sintering-Hot extrusion technology, and then Ag-92SnO₂In₂O₃/Cu/Fe contacts were fabricated by the solid phase bonding process.Compared with that synthesized by traditional oxidation process, Ag-92SnO₂In₂O₃/Cu/Fe contacts fabricated with in-situ oxidated Ag-60SnO₂In₂O₃ as reinforcing phase had lower electrical resistivity ( 2.1 μΩ.cm) and proper hardness(85~110HV). By installing the contacts in motor loaded-thermal protection circuit ( power factor 0.7, 380V, 65A), the results of eletrical life testing showed that Ag-92SnO₂In₂O₃ electrical contacts fabricated by In-Situ oxidation process had higher operations(＞5000 times) which was met the requirements and could substitute for AgCdO/Cu/Fe electrical contacts.

Abstract:Analytical solution is proposed for induction brazing of electrical contacts by solving coupled equations of electromagnetic field and thermal field. And a finite element model is presented in the paper to simulate induction brazing of electrical contact. The numerical results agree well with the analytical results. Therefore the feasibility of simulation analysis of induction brazing using finite element method is fully validated. Numerical results show that, the temperature near the boundary of electrical contacts is the highest in the brazing region. The closer to the center of brazing region, the lower the temperature. In addition, when induction coil wound with ferrite, the state of melting the solder near the center of electrical contact becomes more similar to the state near the boundary of electrical contact, accordingly nonuniform distribution of the temperature at brazing interface is improved to a certain extent. Further more, whether the induction coil optimized or not, the brazing time all decreases with the increase of brazing current. And under the same brazing current, it costs less time to obtain the required temperature rise when using the coil wound with ferrite. This indicates that the use of ferrite to optimize induction coil will improve nonuniform temperature distribution of induction brazing, which will also saving brazing time, thus improving brazing efficiency and brazing quality.This has certain instructive significance to the brazing of electrical contact material

Abstract:YAG nanoparticles were prepared by sol - gel method using yttrium nitrate (Y(NO₃)₃6H₂O) and aluminum nitrate (Al(NO₃)₃9H₂O) as the main raw materials and hexamethylenediamine as the catalyst. Ag / YAG electrical contact composites were fabricated by powder metallurgy. And the microstructure and properties of them were characterized by XRD, SEM, TEM, FTIR and so on. The results showed that pure YAG nanoparticles were successfully synthesized by sol-gel method with the bath temperature of 50℃. The size of YAG nanoparticles increased with the increasing of the amount of hexamethylenediamine.And low resistivity and high hardness (>80Hv) of Ag / YAG electrical contact composite were obtained when sintering temperature reached 860℃.

Abstract:Alumina/silica microspheres were prepared by sol-gel process in oil-in-water emulsion with aluminum sec-butoxide as aluminum source and tetraethoxysilane as silicon source, crystallization was achieved by heat treatment at 1000 oC. The effect of addition of tetraethoxysilane and heat treatment on the crystalline structure and microstructure of the microspheres were studied via scanning electron microscopy, X-ray diffraction and thermogravimertic/diifrental thermal analysis analysis. The results showed that increasing addition of tetraethoxysilane inhibited the gelation of the disperse phase in emulsion, which induced the conglutination of the disperse phase. After heat-treated at 100 oC, the mulite phase in the alumina/silica microspheres was generated and the resulting grain size was12 nm.

Abstract:The LSCO_p and LSCO_wpowders were synthesized by sol-gel method. And then Ag-LSCO_pand Ag-LSCO_w electrical contact composites were fabricated by high-energy ball milling and sintering process with LSCO powders as the second reinforcement phase. The effects of pH and pre-treated sol temperature on the microstructure of LSCO powder were optimized. The effects of molding pressure and sintering temperature on the electrical and mechanical properties of Ag-LSCO contacts were investigated. The microstructure and phase of LSCO powders and Conductivity and hardness characteristics of the Ag-LSCO electrical contact material were tested by scanning electron microscopy (SEM), X-ray diffractometer(XRD), D60K digital metal conductivity meter and HVS-1000 digital microhardness tester. The results showed that LSCO_p was obtained at pH= 9.5 and sintering temperature of 700℃ for 8 h when using single citric acid as gelling agent, but LSCO_w was obtained with citric acid and EDTA used as complex gelling agents. Ag/LSCO_w electrical contact materials were prepared with the molding pressure of 1100 MPa, sintering temperature of 900℃ and sintering time of 6h. And when using LSCO_w powder as the second reinforcement phase, Ag-LSCO_w electrical contacts showed lower resistivity than that of Ag-LSCO_p.

Abstract:By using tin tetrachloride pentahydrate and lanthanum nitrate as raw materials, Lanthanum stannate powder was prepared by chemical coprecipitation method with sintering temperature of 920℃. And then Ag-La₂Sn₂O₇ electrical contact composites were prepared by high-energy ball milling and sintering process. The effects of sintering temperature, sintering time and surface modifier on the morphology and phase of La2Sn2O7 powder were investigated, and the physical properties of Ag- La₂Sn₂O₇ were analyzed. The results showed that La₂Sn₂O₇ powder with mesoporous structure was obtained with sintering temperature of 920℃, 2h. With the pressure of 1200MPa and sintering temperature of 900℃, 6h, The properties of Ag- La₂Sn₂O₇ showed good electrical resistivity and hardness. After the hot extrusion process, Ag- La₂Sn₂O₇ electrical contact material had undergone large plastic deformation, in this process, the formation of fiber-like structured distribution of the particles observed contributed to obtain lower resistivity.

Abstract:A bromination apparatus was designed and manufactured to accurately control the flow rate of ZrBr₄ vapor. Zirconium carbide (ZrC) coatings were deposited on graphite substrate at 1200°C by low pressure chemical vapor deposition from the Zr-Br₂-C₃H₆-H₂-Ar system. The effects of gas composition (input C/Zr ratio) on the morphology and growth mechanism of ZrC coatings were investigated. The coating deposition process was controlled by the surface reaction kinetics at the input C/Zr ratio of 1.5, leading to a loose structure. When the input C/Zr ratios were 0.5 and 1, coating growth was dominated by diffusion kinetics, resulting in (200) preferential orientation with a dense columnar structure. Meanwhile, ZrC coating without free carbon was produced at the input C/Zr ratio of 0.5.

Abstract:Using La(NO₃)₂, MnC₄H₆O₂, citric acid and ethylene glycol (EG), LaMnO₃and LaMn_1-XV_XO₃powers were prepared by Sol-gel with dopant NH₄VO₃. The cayalst were characterized by XRD and used methy orange (MO) as object on photocatalytic oxidation experiment. And effect of heat temperature, cayalyst mass and dopant amount were discussed on degradation rate of MO respectively. The kinetic equations of the process of MO photodegradation were explored. The results show that crystal structure and photocatalytic oxidation degradation rate of MO by LaMnO₃ had been not affect by calcination temperature higher than 700 _oC; the photocatalytic oxidation degradation rate of MO by LaMn_1-XV_XO₃decreased with the increase of the doping amount due to effect of V ion on LaMn_1-XV_XO₃crystal structure; the catalysts were followed first-order kinetic.

Abstract:Using commercial low melting temperature glass (LMTG) powders, Ce doped Y₃Al₅O₁₂ (Ce: YAG) and acrylic resin as raw materials, LMTG with Ce: YAG phosphor films for high-power white LEDs have been successfully prepared through silk-screen printing and low-temperature melt-quenching method. The LMTG with Ce: YAG phosphor thick films were studied by Differential Scanning Calorimeter, X-ray Diffraction, Photoluminescence Spectrum, and so on．The results showed that the crystal structure of Ce: YAG phosphor was formed after sintering, the glass phase was still the major phase in low melting temperature phosphor glass (LMTPG) thick films; The glass transition temperature of LMTPG films are around 305 ℃, and their glass melting temperature are around 450 ℃, both of them were significantly lower than ordinary glass. The emission peaks are a broad emission band that the center is located at 553 nm under the wavelength of 441 nm blue light excitation. the chromaticity coordinate was calculated to be (0.3794, 0.4296),the LE is 115.5 lm/W and the IE is 76.2 %. The research results indicated that the LMTPG films can be a novel promising material without any organic principle for high- power white LEDs．

Abstract:NaNbO3, one of typical antiferroelectric niobates with a complicated sequence of phase transition, has attracted much attention recently due to its potential application in the energy storage and piezoelectric devices. However, for the traditional ceramic process, it is difficult to prepare uniform and dense NaNbO3 ceramics, affecting its performance optimization. In this work, the sol-gel method in combination with spark plasma sintering (SPS) has been applied to build NaNbO3 fine-grained ceramics. The results revealed that perovskite type NaNbO3 nano-powders with mean size of 40 nm can be synthesized by using an aqueous sol-gel route. Subsequently, using the resulted NaNbO3 nano-powders as precursors, the dense ceramics with mean grain size of 1-2 μm were obtained by SPS method. The electrical measurement evidenced that the defect dipoles play the roles of assisting antiferroelectric to ferroelectric (AFE-FE) phase transition. Moreover, the dielectric constant exhibits good frequency stability and the loss tangent was as low as 0.018 (1 kHz). Our work not only provided the dense NaNbO3 ceramics with potential application in new generational lead-free ferroelectric devices, but also developed a new route to construct fine-grained ceramics, which can be applied to prepare other niobates system.

Abstract:zinc chlorideand aluminum chloride (AlCl₃.6H₂O, Aladdin, 97%) were chosen as zinc and aluminum precursors, a mixture of distilled water (H₂O) and ethanol was used as the solvents. Propyleneoxide was used to immediate the gelation process, and poly(ethylene-oxide) was used as a phase-separation inducer. All the chemical reagents were used as received. Porous ZnAl₂O₄ spinel monolith has been successfully prepared via the sol–gel route accompanied by phase separation. The as-prepared samples were characterized by means of XRD, DTA, SEM and FTIR, the inpact of heat-treatment on the structure and phase transmition were discussed. The results show that phase separation can be induced by PEO, thus obtain a prous monoliths with a interesting pore structure with co-continuous solid skeletons and well-controlled pores. The as-prepared samples shows a phase of(ZnAl-LDHs, The ZnAl₂O₄ crystalline phase is obtained after the decomposition of –OH and carbonate anions during the heat treatment at 600 _oC in air. The materials can be widely applied in many catalytic fileds in the future.

Abstract:Nano porous material SiO₂ were prepared by acid-alkali two steps approach with low cost industrial silica sol as silicon source and deionized water as solvent. The surfactant was used as the surface modifier to get rid of the broken of samples in the drying process. The densities, specific surface area and the average pore size of the obtained SiO₂ monoliths are in the range of 150~400 mg/cm₃ and the range of 0.04~0.07W/(m.K), respectively. This method greatly reduced the cost in the preparation of SiO₂ nano porous material, which will largely promote the industrial production and application of porous SiO₂ materials.

Abstract:The organic modified SiO2 sols were prepared by sol-gel method using γ-Methacryloxypropyl trimethoxy silane KH570 as modifier, tetraethylorthosilicate (TEOS) as precursor, and ammonia water as catalyst. Durable antireflective (AR) coatings were then deposited on the glass substrates by dip-coating method. The modified silica AR coatings were characterized by UV-Vis-NIR spectrometry, FTIR, SEM and water contact angle measurement, respectively. The results shown that the modified coating can achieve a high peak transmittance of 99.50% when the molar ratio of KH570 to TEOS was 1:5. After exposed in the humid environment with a relative humidity of 90% for 60 days, the transmittance of SiO2 coating modified by KH570 shown almost no change, which indicate that the environmental stability of the silica coating was greatly improved

Abstract:The monodisperse collodial SiO2 sol was prepared by sol-gel process using tetraethylorthosilicate (TEOS) as precursor and ammonia as catalyst. Hexadecyltrimethoxysilane (HTMS), as a modifier, was added into the sol to passivate the surface of the silica particle . Silica antireflective (AR) coatings were then prepared from different SiO2 sols by dip-coating method. UV-Vis-NIR spectrometer, Fourier transform infrared spectroscopy, transmission electron microscope, Scanning Electron Microscopeand water contact angle measurement were employed to analyze the optical property, microstructure, surface morphology and environmental stability of the coatings. The results show that the HTMS modified silica AR coating can achieve a high transmittance of ~99.8% and possess excellent environment stability.After been placed in an ambient with relative humidity higher than 90% for 2 months, the peak transmittance of the silica AR coatings modified with HTMS decreased only by 0.3%.

Abstract:WO3-TiO2-SiO2 sol has been prepared for dip coating room-temperature optical hydrogen-sensing thin films. FT-IR, SEM, TEM, AFM, XPS and UV-VIS-NIR spectroscopy have been used to analyze the compound films and its gasochromic properties. Though TiO2 did not doping into the film, it can form WO3 particles during the doping stage in sol. These particles have well spread on the films and improved the roughness of the films. The results of UV-VIS-NIR spectroscopy indicated that TiO2-doped films show better sensitivity than WO3-SiO2 films. The improvement of sensitivity may be assigned to the existence of WO3 particles and high roughness of the films.

Abstract:La₂O₃ doped alumina aerogels with different La₂O₃ contents are prepared by using aluminum tri-sec-butoxide as precursor via sol-gel route combined with acetone-aniline in situ water formation (ISWF) method, followed by supercritical fluid drying. The effect of La₂O₃ on microstructure and thermal stability of alumina aerogels is investigated by SEM, TEM, XRD and N₂ adsorption. The results show that the morphology of alumina aerogels changes from sphere like accumulated to notably sheet like stacked with the doping of La₂O₃. An appropriate amount of La₂O₃ doping can enhance the specific surface area of alumina aerogels, and the 9 mol% La₂O₃ doping aerogels has the largest specific surface area. In addition, the alumina crystal growth and phase transition of the aerogels upon heat treatment are effectively inhibited by La₂O₃ doping, which significantly improves the thermal stability of the aerogels. After heat treatment at 1200℃ for 2h, the phase of 9 mol% La₂O₃ doped alumina aerogel remains in the θ-Al₂O₃ while that of undoped one is a-Al₂O₃, and the specific surface area of 9 mol% La₂O₃ doped alumina aerogel is 86.5 m₂/g which is higher than the undoped one (46 m₂/g).

Abstract:The resorcinol–formaldehyde (RF) aerogels composited polyacrylonitrile (PAN) pre-oxidized fibers were prepared by a sol-gel method combined with the CO₂ supercritical drying technique using resorcinol (C₆H₄(OH)₂) and formaldehyde (HCHO) as the precursors andSsodium carbonate as catalyzer respectively, enhanced frame support by PAN pre-oxidized fibers in the solvent. The sample composition is characterized by using Fourier transform infrared spectrometer. Field emission scanning electron microscopy (FESEM), surface area and pore size analyzer were used to investigate the microtopography and the microstructure of the RF aerogels composited PAN pre-oxidized fibers with the nanoporous structure. Compared with the pure RF aerogel, the excellent thermal conductivity of the RF aerogels composited PAN pre-oxidized fibers is 0.032W/mK at 25°C and Young"s modulus of 1.499MPa has increased 0.6 time.

Abstract:TaC-SiC, one member of ultrahigh-temperature ceramics (UHTCs), is potentially useful as structural materials in aerospace engineering and hypersonic flight vehicles. In this paper, the synthesis and characterization of nano-tantalopolycarbosilanes (TS) and their transformation into ceramic materials are reported. The TS-5, TS-10, TS-25, and TS-55 hybrid precursors were prepared by using nanometer tantalum powders (nano-Ta) and polycarbonsilane (PCS), according to the quality of tantalum powders and PCS at 5wt%, 10wt%, 25wt%, 55wt%, respectively, via ultrasonic and ball mill mixing method. The composition, structure, uniformity and pyrolysis process of the obtained precursors were investigated by infrared (IR), thermogravimetric (TGA), element analysis, SEM characterization, and so on. The results show that nano-Ta were dispersed uniformly in PCS. The ceramic yield of the precursors increased gradually with increase of nano-Ta proportion. The inorganic conversion was almost completed at 1073 K and TaC crystal appeared, nano-Ta was completely converted into TaC at 1673 K. As the temperature increases, the crystallization of TaC is more and more sharp, which indicates the growth of TaC grain. The non-oxygen structure, high ceramic yield, and uniform composition enable the as-received hybrid precursor as promising materials to prepare high performance ultrahigh-temperature ceramics.

Abstract:Carbon nanofibers (CNFs) are synthesized by pyrolysis of polyarylonitrile (PAN) nanofibers that are prepared by dissolving of PAN in N,N-dimethylformamide (DMF) solution followed by electrospinning and drying. The obtained CNFs are further treated via a CO₂ activation process. The morphology and porous structures of the obtained nanofibers are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N₂ sorption measurements. Effects of polymer solution concentration and static voltage during the electrospinning process on the morphology and diameter of nanofibers are studied. Their unique microstructural features enable the CNFs to present outstanding high specific capacitance in aqueous, non-aqueous and novel ionic liquid electrolytes. Moreover, the CO₂ activated carbon nanofibers (ACNFs) exhibit a high specific area (2866 m₂ g_-1) and pore volume which is almost three times higher than that of the raw carbon nanofibers. Overall, combinations of the high surface areas and outstanding electrical conductivity make the activated carbon nanofibers could have a further application in supercapacitor electrode materials.

Abstract:In this work, preparation of TaC-SiC fibers derived from Ta-doped polycarbosilicon precursor are reported. Ta-doped precursor was prepared by using nanometer tantalum powders (nano-Ta) and polycarbonsilane (PCS), according to the quality of tantalum powders and PCS at 10wt%, via ultrasonic and ball mill mixing method. TaC-SiC fibers were prepared after melt-spinning, electron beam irradiation and heat-treatment. The composition, structure and pyrolysis process of the obtained green fibers were investigated by IR, TG, XRD, SEM and so on. The results show the evolution of volatile gases is inhibited via introduction of nano-Ta in the precursor and the yield of precursor was increased to 69.32 wt%. TaC ceramics could be prepared via reaction of tantalum powders with free carbon in the fibers. The ceramic fibers were compact and smooth. Thus, TaC-SiC fibers could be prepared using the doped method.

Abstract:In this work, Zr-modified polyborosilazanes (PZC-PBSZ) with a high zirconium content over 10wt% were synthesized via radical reaction between Cp₂Zr(CH₂CH=CH₂)₂ and liquid polyborosilazane under the existence of dicumyl peroxide. The structure and reaction mechanism of PZC-PBSZ were studied using Fourier transforminfrared spectra, nuclear magnetic resonance and X-ray photoelectron spectroscopy. The results shown that besides the self-polymerization, Cp₂Zr(CH₂CH=CH₂)₂ can also reacted with Si-H in LPBSZ via hydrosilylation reaction and substitution reaction to form Zr-C and Zr-Si, respectively. The thermogravimetric-mass spectrometry and ₂₉Si MAS NMR results shown that the escape of goups such as Cp, (CH₃)₃Si and (CH₃)₂SiH was ooccured at temperature range from 400 _oC to 800 _oC. As the temperature went up to 800~1200_oC, the polymer PZC-PBSZ converted into inorganic mineral, and the evolution of SiHN₂C and SiN₃C structure to SiN₄ structure was occurred at that temperature. After pyrolyzing at above 1000 _oC, PZC-PBSZ can convert into ZrC/SiBNC ceramic nanocomposites, with ZrC nanoparticles finely dispersed in SiBNC matrix. The obtained ZrC/SiBNC ceramic nanocomposites can remain fine and nanocrystalline microstructure after annealing at 1800 _oC.

Abstract:Porous vanadium oxide nanotubes (VNTs) are generated by electrospinning technique and following sintering treatment. In this paper, we choose commercial vanadium oxides and benzyl alcohol and Isopropanol as the raw materials to form low-cost inorganic vanadium sol solution followed the appropriate addition of poly(vinylpyrrolidone) (PVP) as electrospinning vanadium precursor[1]. Thus, we can prepare the one-dimensional (1D) VNTs, which mainly containing V₂O₅-sol and PVP, followed by varying the holding time of sintering. Crystal structure and the morphology of electrospun VNTs are analyzed by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) also displays carbon remained after PVP sintered. The electrospun VNTs are about 400 - 700 nm in diameter, and 2-10 μm long with various degrees of porous interconnected fibrous morphology which could be seen by SEM and TEM images. And the degrees of the fracture of the porous vanadium pentoxide nanotubes are various with different holding time at high temperature.

Abstract:The cobalt-ferrite nanoparticles (CoFe₂O₄ NPs) were prepared using the modified co-precipitation method and the CoFe₂O₄-SiO₂ magnetic composites were synthesized via st?ber step. The CoFe₂O₄-SiO₂ was also amino-functionalized to adsorb heavy metal ions. The crystalline phase, morphologies, particle size, chemical compositions and chemical structure of the absorbent have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The composites exhibited excellent magnetic properties with high saturated magnetization and can be separated by a magnet within 30 seconds, and the saturation magnetization (Ms) of CoFe₂O₄ NPs can be adjusted by sintering temperature,increased with increasing the temperature. The effect of pH and reaction time on the adsorption of CoFe₂O₄-SiO₂-NH₂ for Cu (II) was examined. And the amino-functionalized CoFe₂O₄-SiO₂ (CoFe₂O₄-SiO₂-NH₂) showed high adsorption capacity and the removal efficiency for Cu (II), Cd (II), Zn (II) and Mn (II), which makes great potential application on the heavy metal wastewater treatment.

Abstract:The SiO₂ aerogel samples were obtained via one-step sol-gel route and ethanol supercritical dried method. A silicon oxide precursor, tetramethyl orthosilicate (TMOS) was dissolved in methanol and hydrolyzed. By using ammonia as a catalyst and methanol as solvent, SiO₂ aerogels with the density of 95, 110, 135, 165 mg/cm₃ were prepared. Combining with 635 nm wavelength laser and 90° direction scattering of samples, the microstructure-property relationship was studied by analyzing the results of small angle x-ray scattering. In this paper, with the increase of initial solvent, density (r ) and mass fractal dimension (Dm) decreased, while the primary particles (a) and secondary particles (d) increased. The reason may be that the phase separation is changed from the nucleation-dominated to the growth-dominated for initial concentration of TMOS decreased. In addition, the primary or secondary particles were assumed as the scatterer. The results are analyzed, respectively. It is revealed that interaction between the aerogels and the light is irrelevant Rayleigh scattering, and the main scattering took place on the secondary particles. The scattering is determined by the secondary structure, including the fractal dimension (D), the size of primary particles (a), and the size of secondary particles (d).

Abstract:Using bismuth nitrate and cerous ammonium nitrate as raw materials, aqueous ammonia as precipitator, pure and cerium-doped bismuth oxide photocatalysts were prepared through coprecipitation process. The phase composition and microstructure were investigated by XRD, SEM and TEM. The results showed that the pure and cerium-doped bismuth oxide photocatalysts were α-Bi2O3 and the sizes were all around 50 nm. Under the irradiation of visible light, the photocatalytic properties of samples were investigated by using degradation of Orange Ⅱ as the simulative reaction．The results showed that the photocatalytic degradation efficiency increased with the increasing of Ce4+ introduction. The photocatalyst with Ce4+/Bi3+ ratio of 20:80 performed 98% degradation efficiency. In addation, weak acid environment showed a better degradation efficiency.

Abstract:SiBNC preceramic polymer was synthesized by reacting hexamethyldisilazane simultaneously with dichoromethylsilane and trichoroborane in one pot. The prepared precursors were investigated with respect to their chemical and phase composition, by means of FT-IR and XPS. The random arrangement of planar B-N units and Si-N bonds formed the desired polymer precursors with –Si-N-B- framework. The precursor was converted into multinary ceramics when heated above 800°C with the yields of 50.1wt%. Under N2, the obtained SiBNC ceramic remained amorphous up to 1700 °C and formed crystallization of Si3N4 at 1800°C. But under Ar atmosphere, the sample showed obvious crystallization of β-SiC and BNC2 at 1800°C.

Abstract:In order to improve the chemical stability of quantum dots in application for quantum dot sensitized solar cells, we prepared CdXZn1-XTe/CdS core/shell quantum dots with type-II structure by an aqueous phase process using 3-mercaptopropionic acid as a stabilizing agent. We investigated the composition of Zn and Cd in CdXZn1-XTe quantum dots by using X-ray photoelectron spectrometer. The X-ray diffraction patterns confirmed the cubic zinc blende structure of CdXZn1-XTe quantum dots. In addition, we investigated the optical absorption, fluorescence emission and emission decay of samples, indicating that the energy level of ternary quantum dots can be controlled by both size and composition. Therefore, quantum dots with type-II structure can be prepared easily, which is benefitial to the improvement of fluorescence lifetime. We find that there are two decay processes in the emission decay kinetics of CdXZn1-XTe and core/shell CdXZn1-XTe-CdS quantum dots. The average lifetime of the photoexcited carriers is 24.07 and 39.80 ns, respectively.

Abstract:A series of Mn-Zn ferrite nanoparticles with a nominal composition Mn_1-xZn_xFe₂O₄ (0≤x≤1 with steps of 0.2) were synthesized by a template-assisted sol-gel method. The phase identification and magnetic properties of Mn_1-xZn_xFe₂O₄ were measured by XRD and VSM. The effects of Zn content on the structure and magnetic properties of Mn_1-xZn_xFe₂O₄ were studied. It was found that all the Mn_1-xZn_xFe₂O₄ samples with different Zn content exhibited cubic spinel structure in single phase. With the increase of Zn content, the values of the crystal plane spacing d, average crystal size D, saturation magnetization M_s, Curie temperature T_c all exhibited a decreasing trend, while, the coercivity H_c exhibited a first increasing then decreasing trend. For the Mn_0.6Zn_0.4Fe₂O₄samples, the coercivity Hc exhibited the maximum values. The decreasing of M_s was attributed to the Yafet-Kittel canting, the decreasing of T_c was due to the decreasing of anti-ferromagneticScoupling among sublattices, the variation trend of the coercivity H_c can be explained on the basis of the changes of magneto-crystalline anisotropy K₁ of the samples caused by the change of Mn_1-xZn_xFe₂O₄ formula with different Zn content x.

Abstract:A series of Mn-Zn ferrite particles was prepared by a template-assisted sol-gel method and calcined at 773, 973 and 1173 K in air, nitrogen and nitrogen after precalcination at 573 K for 1h in air respectively. The effects of calcined conditions on composition, morphology and properties of Mn-Zn ferrites were investigated by XRD, TEM, VSM and impedance analyzer. It was found that Mn-Zn ferrites with pure spinel structure, uniform size and morphology were obtained only in nitrogen after precalcination at 573 K for 1h in air, which provided a new way to prepare Mn-Zn ferrite nanoparticles with spinel structure. The reaction mechanisms of the Mn-Zn ferrites in different calcined atmospheres were analyzed. The calcined temperature had a major influence on the morphology and properties of the Mn-Zn ferrite particles with spinel structure obtained; and with the increasing of the calcination temperature, the particles in size became larger, M_s increased monotonically, H_c first increased and then decreased, T_c decreased monotonically. The permittivity first increased and then decreased, and the dielectric loss showed a sharp rise after slightly reducing trend with the increasing of frequency.

Abstract:hollow Bi₂WO₆ nanoflowers have been successfully synthesized by using PVP modified hydrothermal method, and their morphology and structure are characterized by XRD, SEM, TEM, PL and UV-vis analysis. A series of controlling experiments indicate PVP play an important role in the formation of the hollow hierarchical structure. Without adding PVP, the morphology of Bi₂WO₆ is the solid nanoplate. When a small amount of PVP is added, the surface of Bi₂WO₆ splits, and the hollow flowerlike morphology forms. The crystalline size of Bi₂WO₆ also slightly increases with PVP contents increasing. The as-prepared PVP-Bi₂WO₆ shows the improved photocatalytic activity under visible light irradiation. After investigated by PL spectra, the emission intensity of PVP assisted Bi₂WO₆ is weaker than that of pure PVP, which means the high-mobility of PVP-Bi₂WO₆ is obtained. PVP assisted Bi₂WO₆ nanoflower can be potentially used for practical waste water treatments.

Abstract:Ni-P composite coatings with various contents of Al₂O₃ particles were prepared by using electroless plating technique and the tribological properties of the coatings were evaluated by a ball-on-disc wear instrument. The morphology, microstructure and chemical composition of the coatings and the counterpart balls were characterized by scanning electron microscopy (SEM), optical microscopy (OM), energy disperse spectrum (EDS), and X-ray diffraction (XRD) technique, and the wear mechanisms were discussed. The results show that the maximum content of Al₂O₃ in the composite coating is about 34.7 wt.%, the phosphorus content of the coatings decreases greatly, and the Ni-P matrix of the composite coatings remain amorphous. The friction coefficient of the coatings is about 0.49–0.58 and higher than that of Ni-P coating. With the increase of Al₂O₃ content in the coatings, the friction coefficient decreases at first and increases later, the micro-hardness of the coatings linearly increases from 502 to 764, and the wear rate of the coatings monotonously decreases from 1.2×10_-14 m₃.N_-1m_-1 to 3.2×10_-15 m₃.N_-1m_-1, and the major wear mechanism of the coatings changes from adhesive wear to abrasive wear.

Abstract:WSx/a-C composite films with various carbon contents were prepared on monocrystalline silicon substrate by ablating a set of graphite/WS₂ combined targets with pulsed excimer laser. The composition, morphology, microstructure and chemical state of the films were characterized by energy disperse spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The hardness, adhesion to substrate and tribological properties in air (RH=50~55%) of the films were evaluated by nano-indentation, scratch tester and ball-on-disk tribometer. The results show that the S/W ratio maintains a constant value about 2.0 and a WS₂ phase with (002) preferred orientation is formed in the films. With increasing carbon content, the hardness peaks at 36.1%C, the adhesion increases and a maximum value is reached at 52.4%C, the friction coefficient decreases first and then increases and a minimum value 0.144 is reached at 41.2%C. The wear rate varies in the range of (0.91~1.61) ×10_-15 m₃N_-1m_-1 and the film with 36.1%C shows the best wear resistance.

Abstract:Ag-SnO2-La2O3 composite powders were prepared by mechanical alloy method with Ag, Sn and La2O3 powder. The composite powders were oxidized, pressed and sintered by combining with oxidation and powder metallurgy processs. The morphology of the composite powders before and after oxidation and their electrical contact materials before and after sintering were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), Vickers hardness tester, metallographic microscope and metal conductivity meter. The results showed that with the increase of Sn content, the resistivity increased but the density decreased after sintering. And the hardness of electrical contact materials was decreased significantly after sintering. When the doping content of La2O3 ranged from 0wt.% up to 3wt.%, the higher the La2O3 doping content, the lower the density of the Ag-SnO2-La2O3 electrical contact material. And with the increase of La2O3 doping content, the resistivity decreased first and then increased for the sintered Ag-SnO2-La2O3 contacts. When the La2O3 doping content was 0.75wt.%, the resistivity of the sintered Ag-SnO2-La2O3 contacts was lowest.

Abstract:A thorough understanding in thermal evolution of alumina hydroxide precursor is fundamental to prepare high-purity alumina powders though a sol-gel process. This work contributes this by investigating the structural evolution of boehmite precursor after annealing at a wide temperature range, 300~1400 °C in air for 1 h. TG-DSC analysis revealed the transformation process of dry boehmite gel. With heat-treatment up to 1400 °C, structural evolution of dry boehmite gel was carried out by combination of XRD, FT-IR, NMR and TEM analysis. The results show that the γ-Al₂O₃ is formed from boehmite at 500 °C, which transform into δ-Al₂O₃ up to 1000 °C. After sintering at 1100 °C, the appearance of a three-phase region including δ-, θ- and initial α-Al₂O₃ is observed. The complete transformation into α-Al₂O₃ lasts until at 1200 °C. The α-Al₂O₃ powders prepared with so-gel method at 1200 °C for 1h had an average particle size of ≈50 nm with good dispersivity and narrow particle size distribution.

Abstract:_{:Magnesium oxide aerogels were made by sol-gel process using magnesium methoxide as precursor,methanol and deionized water as solvents followed by ethanol supercritical fluid drying. The influences of the different factors on the gel time and the specific surface area of magnesium oxide aerogels were studied, and the structure and morphology were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and X-ray diffraction (XRD), and the Small Angle X-ray Scatter (SAXS) was utilized to determine the fractural structure of the magnesium oxide aerogels. The results show that MgO aerogels are typical mesoporous materials with the average pore size of 19.6 nmand possessrich network,high porosity(98%), high specific surface area(904.9 m2/g) and low density(0.055 g/cm3). The resultsof SAXS analysis show that the fractal dimension of the MgO aerogels is 2.32 in high q area which proves the existence of rough surface and pore fractal structure.}

Abstract:Bismuth tungstate (Bi₂WO₆), one of the simplest Aurivillius phase oxides, has been used as a new photocatalyst that works under visible light irradiation. However, it is not easy to reuse the photocatalyst due to difficulty in its recovery from the reaction media. Indeed, reusability and recyclability of photocatalyst are major factors considered in industrial applications. In the paper, magnetically recoverable photocatalyst Fe₃O₄/SiO₂/Bi₂WO₆ was synthesized by a three-step approach. After a hydrothermal process of preparing ferroferric oxide (Fe₃O₄), these Fe₃O₄ nanoparticles were coated with SiO₂ by sol-gel method. Finally, Fe₃O₄/SiO₂ nanoparticles were immobilized onto the surface of Bi₂WO₆ by a second hydrothermal process. The morphology, structure and properties of the composite were characterized by XRD, SEM, PL spectra and UV-vis absorption spectrum. The results show that the Bi₂WO₆ nanosheets structures with average diameters of 500nm are further decorated by Fe₃O₄ nanoparticles with an average diameter of 500nm. The photocatalytic activity of Fe₃O₄/SiO₂/Bi₂WO₆ to degrade rhodamine B was close to that of pure Bi₂WO₆. The photocatalyst with appropriate superparamagnetism can be easily re-collected by applying an external magnetic field. It shows potential applications in pollutant degradation.

Abstract:A simple and template-free synthesis method was developed to fabricate porous graphitic carbon nitride (g-C3N4) through a hydrothermal process in the presence of ammonium hydroxide. The effect of ammonium hydroxide on the structure of porous g-C3N4 was characterized in details by XRD, FT-IR, SEM and TEM. The photocatalytic activity of porous g-C3N4 was evaluated by the degradation of methylene blue (MB) under visible light irradiation. The results show that as-prepared porous g-C3N4 exhibits a porous nanostructure composed of 2D nanosheets and interconnected pores. The photocatalytic activity of porous g-C3N4 is enhanced, owing to the synergistic effect of more reaction sites and good separation efficiency of photo-generated carriers.

Abstract:A facile method to synthesis PS/Ag composite microspheres with high and uniform metal coverage was proposed in this article, therefore avoiding the modification of PS beads. First, polyvinylpyrrolidone (PVP)-capped Ag NPs with a narrow size distribution were obtained by the modified polyol process, and then the PVP-capped Ag NPs were successfully loaded on the PS beads by using a combined swelling-heteroaggregation (CSH) procedure. The size distribution of Ag NPs and the morphology of PS/Ag composite microspheres were investigated. The results show that well-dispersed and uniformly coated PS/Ag microspheres are obtained and the coverage of the Ag NPs can be controlled by changing the amount of Ag NPs.

Abstract:The Aurivillius-type sodium bismuth titanate (Na_0.5Bi_4.5Ti₄O₁₅ or NBT) powders were prepared by two-step hydrothermal routes with starting chemicals containing Bi(NO₃)₃?5H₂O, Ti(C₄H₉O)₄ and CH₃COONa?3H₂O. Crystalline phase and morphology of hydrothermally derived powders are investigated by XRD and SEM, and microstructure and electrical properties of derived ceramics are measured. The results indicate that the elemental ratio in the composition of hydrothermally derived nanopowders is very close to stoichiometic ratio of NBT, which possessed an average diameter of about 1.0μm and a thickness of less than 100 nm. The synthesis temperatures of NBT nanopowders are as low as 260～270℃, which is the lowest temperature among those published literatures. Compared with NBT ceramics by solid state sintering process, the ceramics resulting from hydrothermally derived powders, with dense ceramic body and fine grain size (<2μm), have very similar Curie temperature (≈674℃) and improved dielectric properties at high temperature.

Abstract:Cu doped ZnO(CZO)Nanorod films (NRF) are fabricated on CZO thin films (TF) coated FTO substrates by the hydrothermal method, and the microstructure and resistive switching characteristics are further investigated.The doping of Cu₂₊ helps to improve the quality of crystallization and the oriented growth of nanorods along c axis, in the meantime, effectively compensates the intrinsic defects of nanorods. The prepared CZO NRF/CZO TF devices exhibit bipolar resistive switching behaviors. The compliance current has a great effect on I-V curves and retention performance, and the OFF/ON ratio decreases under a low value of I_CC. The mean OFF/ON ratios are 7460 and 45 respectively when I_CC=10mA and 1mA. Compared with the CZO TF devices, CZO NRF/CZO TF devices show narrow distribution of V_SET and good stability of HRS and LRS, with the V_SET of +0.3～1.55V, HRS of 7.05×10₅～2.1×10₆Ω and LRS of ≈134Ω. CZO nanorods provide large quantities of oxygen vacancy for the formation of conductive filaments with orderly arrangement and uniform size.

Abstract:The strong interaction between n-eicosane and silica nanoscale skeleton exhibits novel phase change temperature management and energy utilization. In this study, a sol-gel synthesized method to fabricate phase change nano-composites by impregnating silica nano-porous materials with n-eicosane is reported. Field emission scanning electron microscope (FE-SEM) results show that the sol-gel synthesized silica has an open network structure as a host for shape stabilization of molten n-eicosane. A combined thermodynamic/heat transfer analysis was carried out to determine the total mass, thickness, and temperature excursion as a function of the area fraction of n-eicosane at given maximum energy and thermal flux. The derived hyperbolic relations showed that increasing the n-eicosane area fraction resulted in a better thermal management in smoothing temperature fluctuation, lower total mass, and lower volume in the nano-composites.

Abstract:Perovskite oxides ErFeO₃ was a new-style photocatalytic material. Using Er(NO₃)₃.5H₂O, Fe(NO₃)₃×9H₂O, citric acid and urea as the main materials, the ErFeO₃ gel was prepared by sol-gel process. Then, the gel was dried in the 80℃ air oven for 48 hours. The xerogel was calcined in the muffle furnace at the temperature of 700-1000℃for preparation ErFeO₃samples. The samples were characterized by thermogravimetric and differential scanning calorimetry (TG-DSC), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance spectra (DRS). Using methyl orange as waste water, the photocatalytic activity of ErFeO₃ was studied under visible-light. The results showed that the particle size of perovskite structure ErFeO₃ was about 80-100 nm and the gap width was about 2.0 eV. Under visible-light, ErFeO₃ showed the high visible-light photocatalytic activity for the decomposition of methyl orange. The ErFeO₃ photocatalysts which were prepared by sol-gel process had wide application prospect in sewage treatment under visible-light.

Abstract:This study evaluates the oxidative resistance and the thermal stability in inert atmosphere of silicon nitride fibers. When the silicon nitride fibers were oxidized at 1000 °C for 1 h, they possessed the highest tensile strength (1.53 GPa) because of the surface defect healing effect of the glassy phase, whereas those oxidized at higher temperatures showed lower strength than the non-oxidized fibers. After treatment at 1200 °C in air, they retained 63% of strength, which indicates that the fiber might possess high serving life at the temperature lower than 1200 °C. Besides, the strength retention of the fibers after 1 h at 1450 °C in nitrogen remained 57%, showing good thermal stability. However, surface oxidation adversely affected the thermal stability of the fibers at high temperatures in nitrogen because of the predominant oxygen-containing phase. Above 1500 °C, crystallization of Si₃N₄ along with decomposition of SiN_xO_y occurred, resulting in a considerable decrease in weight and a catastrophic decrease in strength for the oxidized fibers.

Abstract:A transparent conductive film of silver nanowires was fabricated on glass substance via spin-coating method by commercial silver nanowires, and the transmission spectra andresistance of transparent conductive films were tested by UV-vis spectrophotometer and other technologies.. The effect of the concentration of silver nanowires, the speed of spin-coating and the heat treatment on photoelectrical properties was investigated. The results show that transparent conductive films with the transmittance of 98% are obtained when the concentration is 2 mg/mL and the speed of spin-coating is 7500 rpm; and drop to 91 % after heat treatment at 120 ℃. Transparent conductive films with high photoelectrical properties are fabricated via spin-coating process,which may be used in touch screens and Organic Light-Emitting Diode(OLED).

Abstract:The large-scale application of silica aerogels is restricted due to many reasons, one of which is the poor mechanical. How to exert superiority of aerogels in application has always been the focus of research. In this work, the silica aerogel microspheres were added into polyimide to prepare composite film successfully. The results showed that the thermal conductivity of composite film was declined compared with that of pure polyimide film and kept decreasing with increasing additions, the lowest value was 0.321 W m_-1 K_-1. The mechanical strength is weakened compared with that of pure polyimide film. Therefore, the trade-off between thermal insulation performance and mechanical property is important in application of such film materials. The study enriches the application form of aerogels.

Abstract:Design and fabrication of highly active photocatalysts under visible light irradiation are one of hotspots in the field of photocatalysis. In this paper, mesoporous AgInO₂ nanostructures have been synthesized through a combined sol-gel and ion exchange process. Thermogravimetric analysis-differential scanning calorimeter (TGA-DSC), X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), N₂ adsorption-desorption and ultraviolet-visible (UV-vis) analysis technologies are used to investigate the effects of preparation condition on the microstructure of the AgInO₂. The photocatalytic performances have been evaluated by degradation of the formaldehyde under visible light irradiation. The results demonstrate that the mesoporous AgInO₂ is a delafossite structure with the uniform size about 200-500 nm and nitrogen adsorption- desorption type IV isotherms, the absorption edge of AgInO₂ lies between 500nm and 600 nm in the visible light scope. As-synthesized AgInO₂ exhibited remarkably high photocatalytic activity of 93.97% in decomposing formaldehyde for 180 min. These results provide a basic experimental process for preparation novel photocatalyst of AgInO₂, which will possess a broad prospect in terms of the applications in improving indoor air quality.

Abstract:LiInO₂ nanoparticles (NPs) have been successfully synthesized by a sol-gel method. The structure of the as-synthesized LiInO₂ NPs were characterized using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) analysis technologies. The photocatalytic performances of samples were evaluated using the methyl blue (MB) as a model dye pollutant. Additionally, the photocatalytic degradation mechanism for MB of the LiInO₂ NPs were also proposed. The results demonstrated that the as-prepared LiInO₂ presented a LiFeO₂ structure with the uniform size about 50~100 nm. The calcination temperature can severely impact the structure and photocatalytic performance of the LiInO₂ NPs. The degradation rate of MB was 92% under simulated sunlight using 300W xenon lamp for 90 min. The trapping experiments of the reactive species showed that the holes played an important role in the process of the MB degradation. The results obtained from this work suggested that the LiInO₂ NPs would have potential applications in wastewater treatment.

Abstract:In this paper, Cesium Tungsten Bronze (Cs_xWO₃) powders was synthesized by hydrothermal method. Effects of cesium content of reactant and concentration of citric acid on crystalline phases, micromorphology and size of Cs_xWO₃ powders were studied. The Cs_xWO₃ was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and DLS. The results show that we can get higher crystallinity, smaller diameters and well dispersed Cs_xWO₃ powders at 200℃ for 3 day through moderately increasing the cesium content of reactant and the concentration of citric acid.

Abstract:Three dimensional and four directional carbon fiber reinforced SiC matrix (C_f/SiC) composites were fabricated by precursor infiltration and pyrolysis process with ameliorated interface and low porosity employing a new precursor, liquid polyvinylcarbosilane (LPVCS). LPVCS is a novel precursor with active Si-H and –CH=CH₂ groups with relatively high oxygen content (~7.3 wt.%). The mechanical properties improvement led by ameliorated interface and low porosity was reasearched. Samples with ameliorated interface and low porosity employing LPVCS showed better mechanical properties than those employing ploycarbpsilane (PCS). The flexural strength and fracture toughness of the C_f/SiC composites fabricated with PCS were 301 MPa and 11.2 MPa.m_1/2, respectively, whereas the equivalent values of the samples fabricated with ameliorated interface and low porosity were 442 MPa and 26.1 MPa.m_1/2, respectively. Employing LPVCS for the first infiltration and pyrolysis cycle formed suitable interface, employing PCS as precursor for the left cycles formed relatively low oxygen content matrix, then employing LPVCS for the last several cycles formed low porosity, this the main reason of mechanical properties improvement.

Abstract:Polymethylsilsesquioxane (PMSQ) aerogels were synthesized by using methyltrimethoxysilane (MTMS) as precursor and dimethyl sulfoxide (DMSO) as solvent via sol-gel method and supercritical drying. The laws of gelation times of PMSQ aerogels were discussed by changing the amount of ammonium hydroxide (AH) and DMSO. PMSQ aerogels possess typical nano-porous structures. The gelation time is shortened by the increase of amount of AH, but is extended by the increase of amount of DMSO. As the DMSO content increases, the viscosity changeSis retarded, whereas the increase of AH results in the acceleration of the viscosity change. The short or circle Si–O–Si linkages are generated because of the influence of theSunhydrolyzed –CH₃ groups, which causes the aggregates of particles and phase separation. The uniform gels can be obtained by controlling the relationships between gelation time and the time of phase separation.

Abstract:In order to research the reusability of the high speed flight vehicle in the future, according to the practical application environment of the silica aerogel composites, the silica aerogel composites were treated single-side heat treatment at 400 ℃ for 1800 s, evaluating the stability of silica aerogel composites at 400 ℃ via the method of monitoring the quality loss ratio, size shrinkage ratio,, insulation properties, microstructure change .The results indicate that silica aerogel composites were exhibited excellent stability after single-side heat treatment 10 times, including the variations of mass loss, XYZ direction size shrinkage, thermal conductivity. The variation of elevated temperature and ambient temperature thermal conductivity and microstructure are very small. Comprehensively considering all properties of silica aerogel composites, it can reach up to 10 times.

Abstract:SnO₂ microspherical (SnO_2(s)) were successfully prepared by hydrothermal method at 180℃ for 25 hours,using SnCl₄.5H₂O and NaOH as raw materials. And Ag- SnO_2(s) electrical contacts material were obtained by high-balling and sintering processes; Effects of surfactants, hydrothermal time and pH on the morphology of SnO₂ microspheres were studied；The morphology, structure and other physical properties of Ag-SnO_2(s) electrical contacts material were characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Vickers Hardness Tester and Conductivity Meter. The results show that monodispersed SnO2 microspheres with a diameter of 1 ~ 4 μm were obtained using CTAB as the template at pH=13 with hydrothermal time for 25h. The electrical resistivity and density of Ag-SnO_2(s) electrical contacts material are respectively 3.18 μΩ.cm and 71.5 g.cm_-3, which is better than that of traditional Ag-SnO_2(p) electrical contacts material with nano SnO₂ particulates as the second reinforecement.

Abstract:LiV₃O₈/polypyrrole (PPy) composite materials were prepared by an oxidative polymerization of pyrrole monomer on the surface of LiV₃O₈ using ethanol as medium, FeCl₃ as oxidant, benzene sulfonic acid sodium salt as dopant. The crystal structures and microstructures of LiV₃O₈/PPy were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The electrochemical properties of the composites were investigated with galvanostatic charge–discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that 10nm pyrrole was uniformly polymerized around the LiV₃O₈, and the PPy-coating did not alter the crystal structure of the LiV₃O₈. LiV₃O₈/PPy composite material containing 6% PPy (LVP6) exhibits perfect electrochemical properties, its first discharge capacity reaches a high specific discharge capacity of 274 mAh/g and maintains a stable capacity of 239.4 mAh/g within 100 cycles at the charge–discharge rate of 0.1 C and in the voltage range of 1.8～4.0 V, the capacity retention is 87.4%. But the pure LiV₃O₈ shows that the first discharge capacity is 227.4 mAh/g and the discharge capacity is 160.1 mAh/g after 100 cycles, the capacity retention is only about 70.4%. LiV₃O₈/PPy composite materials show better cycling performance than the pure LiV₃O₈.

Abstract:Using sol-gel method, the iron-containing nanocomposites with the ferric citrate as iron raw were synthesized. The clear sols were gelated at room temperature and then treated at 60 _oC in vacuum to get dry gels which were characterized by thermogravimetricSanalysis (TG). Finally, mesoporous Fe₂O₃/SiO₂ nanoparticles were obtained by the calciner at 400 _oC for 3h. The structural properties of synthesized particles were investigated by X-ray diffraction (XRD), N₂ adsorption-desorptionStechnique, transmission electron microscopy (TEM), Fourier-transform IR spectroscopy (FT-IR), and Temperature programmed reduction (H₂-TPR), which revealed that the iron active centers were successfully incorporated into the silica framework with spherical particles size about 50 nm and a average pore diameter of 30-45 ?. The catalytic activity of nanocatalysts had been tested in the synthesis diphenylmethane by Friedel-Crafts alkylation reaction. It found that the catalysts exhibited an excellent activity with 100% conversion of benzyl chloride and relatively higher selectivity to diphenylmethane, and could be reusedSmultiple times.

Abstract:In this thesis, the synthetic hectorite was introduced to improve the material of Lonquan celadon. The effects of different amounts of hectorite on important characteristics of Longquan celadon were compared. And such important characteristics include rheological properties of clay, microstructure and mechanical properties after sintering. Besides, the 3D printing standard model test of the modified clay was carried out by using mould-free forming technology, so as to test its pendulous performance. The results showed that the addition of hectorite can obviously improve the clay plasticity and effectively reduce deformation and cracking caused by poor plasticity. The flexural strength of the casing went up first and then down, while the water absorption rate went down first and then up. When the addition amount of hectorite was 1.5-2%, the flexural strength of the sample was the best. At this point, the perfect pendulous standard model could be successfully printed.

Abstract:Through proposing creatively the process scheme of designing reverse spinning trajectories and polishing internal surface by pressure aimed at seanless cylinder Ti-liners of necking spinning, it is manufactured successfully that the head plates of Ti-liner can meet design demands besides internal and exterior moulding surface, and the wall thickness of Ti-liner is 0.6 mm whose internal surface has not deeper ruck, especially smooth in the location of R angle. And it is elaborated detailedly that the processing parameters of spinning such as the designed and actual process of spinning mode、spinning passes、spinning temperature and so on. The results of this article can resolve the trouble of welding seam for gas cylinders and liners chronically, and the reliability of production has been improved dramatically during service period.