Jing Xiao Liu

Preparation and Characterization of Silica Aerogels/Glass Wool Composites

Using industrial water glass as silica source, silica aerogel/glass wool composite heat insulation materials were prepared through the gel moulding, surface modification and ambient pressure drying method. The microstructure and porous characteristics of the silica aerogel/glass wool composites were studied by scanning electron microscopy (SEM) and BET nitrogen adsorption-desorption method. The thermal conductivity of silica aerogel/glass wool composites was measured by the thermal conductivity measurement instrument. The results indicate that the as-prepared silica aerogel/glass wool composites exhibit strong hydrophobicity and excellent thermal insulation performance. The thermal conductivity of the obtained silica aerogel/glass wool composites is 1.1×10-2～2.0 W∙m-1∙K-1, and with the increasing of aerogels content, the thermal conductivity of the composites could be decreased further.

Hydrothermal Synthesis of Cesium Tungsten Bronze and its Heat Insulation Properties

Using sodium tungstate and cesium carbonate as raw materials, cesium tungsten bronze (CsxWO3) powders were synthesized by low temperature hydrothermal reaction with citric acid as the reducing agent. The CsxWO3 films were prepared on glass using polyvinyl alcohol solution as dispersing agent. The microstructure and morphology of CsxWO3 powders were characterized by XRD and SEM, and the optical spectra and heat insulation properties of CsxWO3 powder and films were investigated. The results indicate that the synthesized cesium tungsten bronze powders have hexagonal Cs0.32WO3 crystal structure. The as-prepared CsxWO3 powder and films show strong near-infrared absorption and near-infrared shielding properties. Furthermore, the near-infrared shielding performance of glass coated with CsxWO3 film has been further improved after UV irradiation. Especially, the glasses coated with CsxWO3 films which was synthesized from the non-ethanol precursor solution exhibit most outstanding near-infrared shielding performance and best heat insulation effect. In comparison with the blank glass without CsxWO3 film, the heat insulation temperature difference can achieve 24.8°C.

Pore Structure Characterization of TiO2-SiO2 Composite Aerogel Prepared via Ambient Pressure Drying by Sol Pre-Modification Process

In this paper, TiO2-SiO2 composite aerogels were prepared via ambient pressure drying by sol-gel and sol pre-modification method. The pre-modification solution consists of hexamethyldisiloxane (HMDSO) as buffering agent, trimethylchlorosilane (TMCS) as modifier and hexane as organic solvent. The pore structure of TiO2-SiO2 composite aerogels was characterized by N2 adsorption-desorption method. The effects of HMDSO/TMCS volume ratio on the pore structure and properties of TiO2-SiO2 composite aerogel were studied. The results indicate that the pre-modification of TiO2-SiO2 composite sol by adding HMDSO/TMCS/Hexane solution could shorten the preparation period. Increasing the amount of HMDSO is favorable for obtaining TiO2-SiO2 composite aerogel with higher specific surface area and pore volume. The best volume ratio of HMDSO/TMCS/composite sol for preparing mesoporous TiO2-SiO2 composite aerogels were 12:6:120 and 12:12:120, with which the specific surface area and pore volume of the obtained TiO2-SiO2 composite aerogel are 425.2～645.4 m2/g and 0.80～2.85 m3/g, respectively.

Effects of Annealing in Different Atmosphere on the Near-Infrared Shielding Properties of CsxWO3 Particles

Using sodium tungstate and cesium carbonate as raw materials, cesium tungsten bronze (CsxWO3) powders were synthesized by low temperature hydrothermal reaction with citric acid as the reducing agent. Effects of annealing in different atmosphere on the near-infrared shielding properties of CsxWO3 were investigated. The microstructure of CsxWO3 powders was characterized by X-ray diffraction. The CsxWO3 films were prepared on glass using polyvinyl alcohol solution as film-forming agent, and the optical transmission properties of CsxWO3 films were investigated. The results indicate that the near-infrared shielding ability of samples after annealed at 200°C in the air atmosphere did not deteriorate apparently, but the 400°C-annealed samples in the air atmosphere showed apparent decrease of near-infrared shielding properties. Annealing in the carbon powder atmosphere had no apparent effects on the properties of CsxWO3 particles. As for the N2 annealing, the 500°C-annealed samples showed best improved near-infrared shielding as well as high transparency in the visible light region.

Preparation and Characterization of SiO2-WO3 Composite Aerogel by Ambient Pressure Drying Process

Using sodium tungsten and industrial water glass as raw materials, SiO2-WO3 composite aerogels were prepared by ambient pressure drying process. The hexamethyldisilazane(HMDSZ)/hexamethyldisiloxane(HMDSO)/hexane mixing solution was used to modify the sol-gel-derived SiO2-WO3 wet gel. The microstructure, morphology and pore characteristics of the obtained SiO2-WO3 composite aerogels were investigated by XRD, SEM, FTIR and BET N2 adsorption-desorption analysis. The adsorption/photocatalytic degradation for Rhodamine B of SiO2-WO3 composite aerogel was investigated. The results indicate that mesoporous SiO2-WO3 composite aerogel with specific surface area 660.8 m2/g and pore volume 1.94 cm3/g could be prepared by using HMDSZ/HMDSO/hexane mixing solution to modify the wet gel. The obtained SiO2-WO3 composite aerogels have good adsorption/photocatalytic degradation for Rhodamine B than that of pure WO3 aerogel.

Effect of Composite Pore-Forming Agent on Performance of Light-Weight Thermal Insulation Materials

Production of porous and light-weight thermal insulation materials with reduced thermal conductivity and raised porosity were accomplished using sludge (SL) and sugar filter mud (SFM) as pore-forming agent respectively and composite pore-forming agent (CPFA) at different sintered temperature and holding time. The results of thermal insulation materials with flexural strength 7.65 MPa and thermal conductivity 0.056 W•m-1•K-1, obtained at 1000 °C for 0.5 h show that its the porosity factor raised to 40.60% and the bulk density of the materials decreased down to 1.265 g/cm3 using CPFA, closed porosity and dense structure in sample was observed by SEM

Synthesis and Visible Light Photocatalytic Activity of Spinel MAl2O4 (M=Mg, Zn, Cu)

Aluminium spinel MAl2O4 (M = Mg, Zn, Cu) photocatalysts were prepared by a sol-gel method. The prepared samples were characterized by X-ray diffraction and transmission electron microscope. The results indicated that the samples possess a single spinel-type structure. Ultraviolet-visible diffuse reflectance spectra showed an extension of light absorption into the visible region. The spinel MAl2O4 photocatalysts exhibited high photocatalytic activity for the degradation of industrial dyes under high pressure mercury lamp and visible light irradiation, especially CuAl2O4. With the decrease of band gap of MAl2O4 (M = Mg, Zn, Cu), the photocatalytic activity increases. The possible reasons are discussed from the crystal field theory and energy band theory. These characteristics make the aluminium spinel MAl2O4 (M = Mg, Zn, Cu) photocatalysts to be promising candidates for the photocatalytic degradation of dyes.

The Effect of Lithium Source on the Electrochemical Performance of LiFePO4/C Cathode Materials Synthesized by Sol-Gel Method

LiFePO4/C cathode materials were synthesized by Sol-gel method under the same process conditions using different water-soluble lithium source (LiOH, Li2CO3, LiNO3). The phase of synthesized powders were characterized by XRD; and the electrochemical performance of the material was investigated by measurements of cyclic voltammetry, AC impedance measurements, charge and discharge. The results show that the synthesized LiFePO4/C using LiOH as the lithium source has high electrochemical reversibility and low internal impedance. The specific discharge capacity is 147.5mAh/g under the discharge at 0.2C rate. It also has high stability of cycle capacity, and almost no attenuation after 30 cycles. So it has the excellent electrochemical performance.

Rapid Biomimetic Deposition of Drug-Loaded Apatite Coatings

In order to reduce the postoperative inflammation by the slow release of drugs at the beginning of implanting, drug-loaded apatite coatings and chitosan-apatite composite coatings on the NiTi alloy surface were prepared in the Simulated Body Fluid concentrated by five (5×SBF) under constant bubbling of carbon dioxide gas by biomimetic synthesis method. The composition and surface morphology of the coatings were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Additionally, a bacterial inhibition test was conducted for evaluating the drug slow release effects from the drug-loaded coatings. The results indicated that the porous apatite coatings with the flake structure could be deposited using the 5 times Simulated Body Fluid, and the drug-loaded chitosan-apatite composite coatings with better drug slow release effect were obtained. The incorporation of chitosan into the coatings could effectively control the drug release rate and was favorable for achieving better drug slow release effects.

Improved Corrosion Resistance of NiTi Alloy by Coated with TiO2-SiO2-HAP Composite Films

In order to further improve the corrosion resistance and bioactivity of NiTi alloy, TiO2-SiO2-HAP (hydroxyapatite) composite films with different composition were prepared on NiTi alloy substrate by a sol-gel method. The phase composition, surface morphology, interface adhesive strength and corrosion resistance were studied. The results indicated that the composite film heat-treated at 500°C showed amorphous state, and with increasing of heat-treatment temperature, crystals of CaSiO3, anatase TiO2 and hydroxyapatite (HAP) appeared. The composite film with higher (TiO2-SiO2) content was more uniform and smooth, and had higher interface adhesive strength with the substrate. With the decreasing of (TiO2-SiO2) content, the composite films tended to become irregular, and tiny crack clusters with ringy distribution appeared when the (Ti+Si)/Ca molar ratio was decreased to 25/75, which led to decrease of interface adhesive strength to some extent. The anodic polarization curves indicated that NiTi alloy coated with TiO2-SiO2-HAP composite films had an apparent improvement of corrosion resistance, with an obvious decrease of passivation current.