Papers by Keyword: Silica

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Authors: Hai Xu, Jia Chen Liu, Ying Na Zhao, Zhen Guang Hou
Abstract: Highly porous silica ceramics were produced by gel casting with egg white protein (EWP) as a foaming agent and evaluated by measuring the porosity, mechanical strength and microstructure. After drying, the green bodies were debindered and sintered at 1300°C for 4 h. The influences of the EWP content on the open porosity as well as the strength were investigated. The porosity of the obtained porous silica ceramics was within 70.2%-86.1%, the bending strength decreased from 6.81 MPa to 5.48 MPa. It was found that the strength dependence of the porosity was well described by a modified exponential relation of the form σ=σ0exp(-BP), where P is the porosity and B is a constant (B = 1.37 was obtained by fitting the experimental data). This finding is in agreement with other literature data and seems to indicate a common feature of all porous ceramics.
Authors: Jian Li, Xue Mei Wen, Wei Zhang, Yu Ping Chen, Ying Xiao, Chen Xue Xiong, Wei Zhu, Tao Jiang
Abstract: A facile biomimetic method was developed to enhance the interfacial interaction in polymer-inorganic composites. By mimicking mussel adhesive proteins, a monolayer of polydopamine (PD) was constructed on surface of silica particles through a controllable coating pathway. The modified silica (PD-silica) was incorporated into an epoxy resin. It is found that the strong interfacial interactions brought by the polydopamine benefits the effective interfacial stress transfer, leading to greatly improved flexural properties of epoxy based composites.
Authors: X.Q. Chen, Y.Y. Liu, K.H. Qi, X. Zhou, J.H. Xin
Abstract: Monodisperse silica particles containing available active C=C bonds were directly prepared by a simple two-step sol-gel method. In the first step the hydrolysis of vinyltrimethoxysilane (VTMS) was performed under acidic conditions in an aqueous solution. In the second step the condensation of the siloxane precursors progressed under basic conditions, resulting in production of silica nanoparticles containing available active C=C bonds. The products were characterized using SEM and FTIR.
Authors: Jian Hui Luo, Yuan Yang Li, Ping Mei Wang, Bi Bo Xia, Li Peng He, Bo Wen Yang, Bo Jiang
Abstract: Nano-silica was prepared using tetraethylorthosilicate (TEOS) as precursor by sol-gel technology based on stÖber method. These silica nanoparticals were further modified with silane coupling agents, i.e., Hexadecyltrimethoxysilane (HDTMS), dimethoxydiphenylsilane (DMMPS), to introduce organic functional groups on the surface of SiO2 nanoparticles. The Fourier transform-infrared (FTIR) spectra indicated that these silane coupling agents were anchored on the surface of silica particles. And the obtained organic–inorganic hybrid SiO2 particles showed an improvement in hydrophobicity, which can effectively inhibit these silica particles from aggregating.
Authors: Y. Fujiwara, Tetsuhiko Isobe, Mamoru Senna, M. Tanaka
Authors: Xue Qing Liu, Heng Zhou, Ji Yan Liu, Hao Wang, Shao Jun Cai
Abstract: The influence of silica on the mechanical properties, thermal stability and the flammability of epoxy (EP) blended with aluminum methylethylphosphinate (Al (MEP) has been studied by the limiting oxygen index (LOI), UL-94 test, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Results show that adding silica enhances the mechanical properties of EP/Al (MEP). Synergistic effects between Al (MEP) and silica are obtained leading to the increase of LOI and to the reduction of combustion time. The TGA data demonstrate that silica can enhance the thermal stability of the EP/Al (MEP) and increase the char residue formation at high temperature. When the rice husk silica is substituted for silica, the composite presents lower LOI, lower thermal stability and char formation as well as inferior mechanical strength. The SEM results indicate that rice husk silica based composite shows poorer fillermatrix adhesion, which will be responsible for its inferior mechanical properties, lower thermal stability and flammability.
Authors: Dong Shin Yun, Hyun Jung Kim, Hyun Chang Shin, Venkatathri Narayanan, Jung Whan Yoo, Seong Ho Lee, Dong Jin Lee, Nam Hoon Kim
Abstract: The physicochemical characteristics (SEM, N2 adsorption, FT-IR, MASNMR) of samples from kinetics (10 min, 20 min, 30 min, 1 h and 3h) of hydrolysis of tetraethyl orthosilicate (TEOS) gives new insight into the synthesis of nanosphere. The particle sizes are increased with time, however, the surface areas decreased. FT-IR investigation reveals the presence of high intensed silanol groups of 960 cm-1 at 10 min, which reduced on progress of the reaction time. This suggests the partial hydrolysis and condensation of alkoxy groups in TEOS. 29Si MASNMR analysis shows the presence three different silica species(Q4, Q3 and Q2) in 10 and 20 min samples. The intensity of Q2 species decreases with time and other species concentration were increased.
Authors: Xiang Wen Kong, Han Wang, Zhao Jing Li, Jing Zhang
Abstract: Cyclohexyl ferulate was prepared by direct sterification of ferulic acid and cyclohexanol as raw materials with sodium bisulfate supported by silica as a catalyst. The influences of some factors on the synthesis process were studied. The optimal reaction conditions based upon 0. 2 mol of ferulic acid were chosen that the molar ratio of cyclohexanol and ferulic acid was 10 : 1, the mass ratio of catalyst to reactants was 5%, refluing reaction time was 3.5 hours, et a1. The yield of the product reached 80%. The structure of the product was characterized by IR, 1H NMR and MS spectrum. The catalyst could be recycled and used for many times, which is friendly to the environment.
Authors: An Ran Guo, Jia Chen Liu, Yi Bing Sun, Wen Jun Lian, Lu Yang
Abstract: A new technique of flyash utilization was presented and high-purity silica was prepared by alkali leaching. The flyash was added into sodium hydroxide solution, and then the suspension was heated to 115 °C for 30 min. After filtrated, the filtrate was collected and carbon dioxide was imported into the solution. Finally, the silica would precipitate from the solution. The silica was characterized by scanning electron microscopy, X-ray diffraction and X-ray fluorescence spectrometer. The high-purity silica prepared from flyash was qualified for the rubber reinforcing agent used in shoemaking.
Authors: Xiao Yu Ma, Li Li Wang, Su Ping Cui, Ya Li Wang
Abstract: In the present work, a green and sustainable route for preparation of hydrochars and silica from a bio-resource (rice husk) under low temperature and atmospheric pressure was described. This route was achieved with the catalysis of sulfuric acid and NH4F. The sphere-like carbon materials with regular size of about 500nm were obtained at 95°C for 6 h when the acid concentration was 42% and 52%. The obtained yield of silica reached up to 94.6% and the particle size was 50-60nm. The morphology of the hydrochars was controllable by changing the concentration of sulfuric acid. Microstructure of the precipitated silica powder was carried out using transmission electron microscopy (TEM). The preparation conditions were determined and the recyclability of the process was confirmed experimentally. All the reactants and byproducts were recyclable in this process, without the waste emissions.
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