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Silica Sol (silica + sol)
Selected AbstractsNanoimprint Lithography on Silica Sol,Gels: A Simple Route to Sequential Patterning,ADVANCED MATERIALS, Issue 5 2009Christophe Peroz Inorganic condensing sol-gel films are promising resist materials for nanoimprint lithography. We demonstrate that sequential patterning of these materials can be performed by controlling their condensation state. As a consequence, multilevel inorganic patterns can be obtained by superimposing structures, as show here, where successive stamping of a line pattern leads to two-level square features. [source] THIS ARTICLE HAS BEEN RETRACTED Effect of Silica Sol on the Properties of Alumina-Based Duplex Ceramic CoresINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2008Yexia Qin A series of alumina-based ceramic cores sintered at 1300°C, 1400°C, and 1500°C for 5 h were prepared, and the phases and microstructures were characterized by X-ray diffraction and scanning electron microscopy. The effect of colloidal silica sols on the properties of ceramic core was discussed. The properties of these materials were determined. The results indicated that the microstructure of the core is characterized by the presence of substantially unreacted Al2O3 particles having a polycrystalline composition consisting essentially of in situ synthesized 3Al2O3·2SiO2 on the surface of the Al2O3 particles. The colloidal silica sol contents do not have an appreciable effect on the densification and shrinkage of the alumina ceramic core. The ceramic cores of 5 wt% colloidal silica sol contents sintered at 1500°C for 5 h showed the smallest creep deformation in the present research. [source] Heck Vinylation of Aryl Iodides by a Silica Sol,Gel Entrapped Pd(II) Catalyst and Its Combination with a Photocyclization Process.CHEMINFORM, Issue 32 2004Khalil Hamza Abstract For Abstract see ChemInform Abstract in Full Text. [source] Three Phase Microemulsion/Sol,Gel System for Aqueous C,C Coupling of Hydrophobic SubstratesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2008Dmitry Tsvelikhovsky Abstract Heck, Stille, Suzuki and three-component coupling reactions with hydrophobic substrates have been carried out in water. The substrates are initially transformed by a general procedure into a microemulsion, which consists of nearly 90,% water with the aid of sodium dodecyl sulfate and either PrOH or BuOH. The surfactant carries the molecules of the substrates to Pd(OAc)2 entrapped within a hydrophobicitized silica sol,gel matrix where the coupling between the substrates is assumed to take place. The products are then returned by the surfactant into the microemulsion from which it can be released. The immobilized palladium catalyst is leach proof and recyclable. It can be used in various coupling processes at least six times without loss of activity. Experiments with D2O have revealed that the water does not take part in the coupling process, but it has an effect on the pore size of the sol,gel matrix, which hosts the palladium catalyst. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Biomorphic Silicon Nitride Ceramics with Fibrous Morphology Prepared by Sol Infiltration and Reduction,NitridationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Min Luo Biomorphic silicon nitride (Si3N4) ceramics with fibrous morphology were fabricated by combining sol,gel infiltration with carbothermal reduction nitridation from wood precursor. Y2O3 -incorporated silica sol was used as the infiltrated solution to promote the formation of fibrous Si3N4 grain at 1600°C under high nitrogen pressure (0.6 MPa). The influence of sintering conditions (additive and temperature) on the phase composition and microstructure of sintering bodies was analyzed, and the reaction mechanism is discussed. [source] Surface Treatment of Templates for Fabrication of Reticulated Porous CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007Xi-peng Pu Before impregnation of the organic templates with an aqueous ceramic slurry, the templates were treated using silica sol. The surface morphology, elasticity of the templates, and the solid loading were studied. After the treatment, the coherence between the template and the slurry was significantly optimized, and the surfaces of the templates were uniformly covered by slurry. The elasticity of the templates was also increased. Consequently, the loading content increased considerably. [source] Seeded Crystallization of LeuciteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Yi Zhang The leucite crystallization kinetics from a hydrothermally derived precursor seeded with nano-crystalline leucite was investigated by X-ray diffraction and non-isothermal differential thermal analysis. The nano-crystalline leucite was prepared by high-energy milling of high-purity leucite powder and the leucite precursor was prepared by the hydrothermal method of silica sol, aluminum nitrate, and potassium nitrate. After the seeds were introduced, the crystallization temperature of the precursor was lowered by 100°C and the transition phase kalsilite did not appear during the crystallization process. When the seeded precursor was heat treated at 700°C, a small amount of cubic leucite was stabilized to room temperature. The seeded precursor showed an exothermic peak between 800° and 920°C under different heating rates. The activation energy for the growth of leucite from the seeded precursor was 256(SD9) kJ/mol. [source] Cell-free synthesis of functional proteins using transcription/translation machinery entrapped in silica sol,gel matrixBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Kyeong-Ohn Kim Abstract Herewith we report the encapsulation of functional protein synthesis machinery in a silica sol,gel matrix. When the sol,gel reaction using alkoxysilane monomers was carried out in the presence of Escherichia coli cell extract, macromolecular protein synthesis machinery in the cell extract was successfully immobilized within a silica gel matrix, catalyzing the translation of co-immobilized DNA when supplied with small-molecular-weight substrates for protein synthesis. The efficiency of protein synthesis was affected by the pore size of the gel structure, which was controlled through the use of appropriate additives during the sol,gel reactions. To the best of our knowledge, this is the first report describing the reproduction of the entire set of complicated biological process within an inorganic gel matrix, and we expect that the developed technology will find many applications in numerous fields such as high-throughput gene expression and the development of multifunctional biosensors. Biotechnol. Bioeng. 2009;102: 303,307. © 2008 Wiley Periodicals, Inc. [source] THIS ARTICLE HAS BEEN RETRACTED Effect of Silica Sol on the Properties of Alumina-Based Duplex Ceramic CoresINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2008Yexia Qin A series of alumina-based ceramic cores sintered at 1300°C, 1400°C, and 1500°C for 5 h were prepared, and the phases and microstructures were characterized by X-ray diffraction and scanning electron microscopy. The effect of colloidal silica sols on the properties of ceramic core was discussed. The properties of these materials were determined. The results indicated that the microstructure of the core is characterized by the presence of substantially unreacted Al2O3 particles having a polycrystalline composition consisting essentially of in situ synthesized 3Al2O3·2SiO2 on the surface of the Al2O3 particles. The colloidal silica sol contents do not have an appreciable effect on the densification and shrinkage of the alumina ceramic core. The ceramic cores of 5 wt% colloidal silica sol contents sintered at 1500°C for 5 h showed the smallest creep deformation in the present research. [source] Structure and Mechanical Properties of Polyurethane/Silica Hybrid CoatingsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Yongchun Chen Abstract Summary: Polyurethane/silica hybrid coatings were prepared via in situ (IS) or blending (BL) method using different acidic silica sols. The effects of preparation methods, silica types, and content on the structure and mechanical properties of the hybrid coatings were investigated. It was found that there existed two types of silica phases in the hybrid coatings: silica-rich agglomerate and primary silica-rich phase, whose size and compactness depended upon the silica types and the preparation methods. Introducing silica could result in obvious changes in surface free energy, atomic composition, and mechanical properties of the hybrid coatings. Typical SEM image of the fractured surface of hybrids obtained by the in situ method. [source] | |||||||||||||