Papers by Keyword: SiO₂

Abstract: Monodispersed Ag nanoparticles with sizes down to 10 nm were synthesised in an aqueous medium. These nanoparticles were then successfully dispersesd up to 45 wt% in aqueous medium with the aid of a copolymer, Pluronic F127. SiO2 nanoparticles were added to the ink formula in order to improve the physical properties of the ink after inkjet printing. The effect of the different SiO2 concentrations in the ink on the adhesion, resistivity and microstructure of the film at several sintered temperatures was investigated. The percentage of the SiO2 added in the ink was responsible for the development of microstructure for the sintered silver films and improving adhesion of the films to the substrate. The addition of SiO2 had also significant effect on improving the conductivity of the films. The conductivity is, though, better when only a small amount of SiO2 was added.

Abstract: The effect of sodium carbonate concentration on alumina leaching of low A/S ratio clinkers and SiO2 concentration in leached liquor was studied in this paper. The clinker with the Al2O3/SiO2 mass ratio of 1.0 (the molar ratios of CaO/SiO2 and Na2O/Al2O3 are 2.0 and 1.05) was sintered at 1230°C using AR reagents. The alumina leaching rate and SiO2 concentration in leached liquor increase with the increase of sodium carbonate concentration, and the alumina leaching rate reaches its maximum of 96.36% when the sodium carbonate concentration is 15g/L. The results of XRD indicate that sodium carbonate can inhibit the formation of hydrogarnet, and there is almost no formation of hydrogarnet when the sodium carbonate concentration is 15g/L.

Abstract: Polyaniline/SiO2 composites were prepared by the SiO2 particles whose surface character was modified by succinic acid. The composites were characterized by Fourier transform infrared (FT–IR) spectroscopy, X–ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM). The results demonstrated that the thermal stability of PANI had improved.

Abstract: This paper studied the impact of silicon oxide layer on photovoltaic characteristic of iron-doped amorphous carbon film/silicon heterojunction (a-C:Fe/Si). The results show that a native SiO2 layer on the silicon surface can provide a significant improvement of the a-C:Fe/Si devices’ photovoltaic performances, especially for the short circuit current and fill factor. This improvement partly may be attributed to the electron recombination process is suppressed and the interface is modified by the SiO2 film based on the open circuit voltage decay measurement.

Abstract: 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.

Abstract: Poly(viny1 alcohol) (PVA)/regenerated silk fibroin (RSF)/silicon dioxide (SiO₂) fiber mats were prepared by electrospinning of composite solutions. Fiber morphology was observed under a scanning electron microscope and effects addition of SiO₂ was evaluated. Results showed that the obtained fibers exhibited a smooth outer surface, and the continuity was improved because of the different solution conductivity, solution viscosity and compatibility of PVA and RSF by the addition of 1.0 wt. % SiO₂. It was found that both Si-O-C linkage and hydrogen bonding interactions were existed among SiO₂, PVA, and RSF by FTIR spectroscopy. The addition of SiO₂ also resulted in the decrease of crystallinity and increase of thermal properties of electrospun fibers, which were suggested as a result of enhanced compatibility and physical properties of PVA and RSF composite.

Abstract: Sulfonated poly (ethersulfone) s (S-PDHTPEs) were prepared from 4,4-(2,2-diphenylethenylidene) bisphenol (DHTPE), 4,4-sulfonyldiphenol, 4-fluorophenylsulfone using potassium carbonate, and followed sulfonation reaction with conc. sulfuric acid. DHTPE is a conjugated structure, which enables to form planar conformation between aromatic rings, and selectively sufonated on phenyl rings of polymer side chain. Composite membranes were prepared with copolymers and SiO₂ nanoparticles (20 nm, 4~10%wt). The composite membranes were cast from DMSO. A series of composite membranes structures and characteristic were evaluated by the ¹H-NMR spectroscopy, and thermal stabilities. The membranes were performed by ion exchange capacity (IEC), water uptake and proton conductivity as a function of degree of sulfonation.

Abstract: A novel catalyst, H₃PW₆Mo₆O₄₀/SiO₂ was prepared by a sol-gel technique and its catalytic application in synthesis of acetals and ketals were tested. The preparation conditions of catalyst were optimised by using the orthogonal experimental design. The optimum conditions are: the mass ratio of H3PW6Mo6O40 to SiO₂ is 0.4, calcination temperature is 150 °C and calcination time is 3 h. The steric properties of the reactants play an important role in the acetalization. The catalytic activity of the catalyst decreases when the size of the reactant increased. Although a decrease in catalytic activity was observed with its subsequent reuse, the catalyst could be reused at least four times without any other treatments. The results reveal that the H₃PW₆Mo₆O₄₀/SiO₂ catalysis generally results in good yields of acetals and ketals under mild reaction conditions.

Abstract: A kind of porous SiO2 bulk materials with pore size distributed in nano and micron scales has been fabricated by freeze-casting of SiO2 nano-size powders in TBA (tert-butyl alcohol)/H2O suspensions. The content of TBA in the well mixed TBA/H2O binary co-solvent plays an important role in size and morphology control of the pores in the obtained SiO2 monolithic materials, since the ratio of TBA/H2O determines the competition of crystallization of TBA and ice, therefore, the microstructure of the monolithic SiO2. It was found that the content of TBA in the range from 30 to 40% was suitable for formation of more nano-pores in the SiO2 monolith. The insulation materials freeze-casted from the suspension of SiO2 in 13wt% and TBA in 40wt% has the density of 0.17g/cm3, and the specific surface area of 282m2/g. The pore size has a trimodal size distribution with three mean diameters of 15nm, 100nm and 4μm, respectively.

Abstract: Nano-structrued SiO2 coating was prepared on metal substrate by sol-gel processing and the dip-coating technique using tetraethyl orthosilicate (TEOS) as precursor. And the superhydrophobicic SiO2 coating was obtained after modified with fluoroalkylsilane (FAS, CF3(CF2)7CH2CH2Si(OCH3)3). The morphology of obtained SiO2 coating was characterized by scanning electronic microscope (SEM). And the superhydrophobicity of SiO2 coating modified with FAS was characterized by contact angle meter. It was observed that the SiO2 coating showed superhydrophobicity with water contact angle 154.7° after modified with fluoroalkylsilane, and the superhydrophobicity was corrosion-resistance to acid or alkali to some extant.