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This completely updated and expanded second edition stands as a comprehensive knowledgebase on both the fundamentals and applications of this important materials processing method. The diverse, international team of contributing authors of this reference clarify in extensive detail properties and applications of sol-gel science and technology as it pertains to the production of substances, active and non-active, including optical, electronic, chemical, sensor, bio- and structural materials. Essential to a wide range of manufacturing industries, the compilation divides into the three complementary sections: Sol-Gel Processing, devoted to general aspects of processing and recently developed materials such as organic-inorganic hybrids, photonic crystals, ferroelectric coatings, and photocatalysts; Characterization of Sol-Gel Materials and Products, presenting contributions that highlight the notion that useful materials are only produced when characterization is tied to processing, such as determination of structure by NMR, in-situ characterization of the sol-gel reaction process, determination of microstructure of oxide gels, characterization of porous structure of gels by the surface measurements, and characterization of organic-inorganic hybrid; and Applications of Sol-Gel Technology, covering applications such as the sol-gel method used in processing of bulk silica glasses, bulk porous gels prepared by sol-gel method, application of sol-gel method to fabrication of glass and ceramic fibers, reflective and antireflective coating films, application of sol-gel method to formation of photocatalytic coating films, and application of sol-gel method to bioactive coating films. The comprehensive scope and integrated treatment of topics make this reference volume ideal for R&D scientists and engineers across a wide range of disciplines and professional interests.
Silica based sol-gel thin films have been extensively studied because of their advantages that include optical transparency, high biodegradability and low intrinsic fluorescence. However, one concern with silica based sol-gel derived materials is their long term stability in aqueous solutions. Another concern is their limited porosity. These two concerns limit the application of these materials in catalysis and separations. The main objective of this study is to prepare porous, thin films using titanium alkoxides as precursors and evaluate their long term stability in aqueous solutions. Colloidal crystal templating will be used to introduce macrosized pores into the titania network. The materials will be characterized using SEM and AFM. To prove that the templated films provide access to the underlying surface of the electrode, a conducting metal like copper was electrodeposited inside the nano-wells. The stability of titania and silica films will be evaluated over a two month period using cyclic voltammetry with three redox probes.
Modifying their surface with a coating of another ceramic material can dramatically alter the properties of ceramic particles. In the present work we have demonstrated that the Al2O3 particles can he successfully coated by TiO2 using a novel sol-gel technique. The nature of these coatings was predicted on the basis of scanning electron microscopy imaging in conjunction with the micro-Raman scattering measurements. The surface morphology of these particles shows that either individual or group of sub-micron alumina particles ate coated with the nanocrystalline titania particles. The thickness of the titania coating could he varied by changing the precursor sol concentration. Amorphous titania was converted to anatase phase at 400 deg. C and upon further heating it started transforming to rutile phase, and both these phases coexisted in the coated particles that were heat treated up to 800 deg. C. The mechanical strength of the titania coating was measured qualitatively by ultrasonicating the coated powders for longer duration to observe that titania coatings are strongly adhered with the alumina particles.
Novel sol-gel titania-poly(dimethylsiloxane) (TiO2-PDMS) and titania-silica-N-(triethoxysilylpropyl)-O-polyethylene oxide urethane (TiO2-SiO2-TESP-PEO) coatings were developed for capillary microextraction (CME) to perform on-line preconcentration and HPLC analysis of trace impurities in aqueous samples. Due to chemical inertness of titania, effective covalent binding of a suitable organic ligand to its surface is difficult via conventional surface modification methods. In this research, sol-gel chemistry was employed to chemically bind hydroxy-terminated poly(dimethylsiloxane) (PDMS) and N-(triethoxysilylpropyl)-O-polyethylene oxide urethane (TESP-PEO) to sol-gel titania and sol-gel titania-silica network, respectively. A method is presented describing in situ preparation of the titania-based sol-gel PDMS and TESP-PEO coatings and their immobilization on the inner surface of a fused-silica microextraction capillary. To perform on-line CME-HPLC, the sol-gel TiO2-PDMS or TiO2-SiO 2-TESP-PEO capillary was installed in the HPLC injection port as an external sampling loop, and a conventional HPLC separation column was used for the liquid chromatographic separation. The sol-gel TiO2-PDMS-coated microextraction capillary was used for on-line CME-HPLC analysis of non-polar and moderately polar analytes, and the sol-gel coatings showed excellent pH (1-13), and solvent (acetonitrile and methanol) stabilities under elevated temperatures (150°C) over analogous non-sol-gel silica-based coatings. Extraction of highly polar analytes, especially from aqueous phases is not an easy task. However, the sol-gel TiO2- SiO2-TESP-PEO-coated capillaries showed excellent capability of extracting underivatized highly polar analytes from aqueous samples. This opens the possibility to employ sol-gel titania-based polar coatings for solvent-free extraction and trace analysis of target analytes in environmental and biomedical matrices. To our knowledge, this is the first research on the use of sol-gel titania (or titania-silica)-based organic-inorganic materials as a sorbent in capillary microextraction. The newly developed sol-gel titania (or titania-silica)-based organic-inorganic hybrid extraction media provides an effective solution to coupling CME with HPLC (CME-HPLC), and this can be expected to become a powerful analytical tool in environmental investigations, proteomic research, early disease diagnosis and biomarker research. Being a combination of a highly efficient solvent free sample preconcentration technique (CME) and a powerful separation method (HPLC), CME-HPLC poses to become a key analytical tool in solving complex chemical, environmental, and biomedical problems involving complex matrices.
Sol-gel technique is one of the simplest techniques to prepare thin films and can provide almost single- or multi-component oxide coating on glass or metals surface. Coatings prepared by this technique have shown excellent chemical stability, oxidation control, and enhanced corrosion resistance for metal substrate. This book focuses on the advantages of nanostructured titanium dioxide coatings to many engineering applications and also explains the mechanisms of formation of the nanostructured titanium dioxide coatings including significant mechanical and physical properties. It also explains the structural properties of the nano-structured titania coatings. This book also illustrates the factors affecting particle size and morphology of titania coated samples.
Sol-Gel Science and Technology covers optical, electronic and magnetic, chemical, mechanical, biomedical and biotechnological materials. Concerning the microstructures, the sol-gel method applies to porous materials, dense materials like glasses and ceramics, organic-inorganic hybrids and nanocomposites. The four volumes of this reference treat four areas that are timely, important and seeing great research activity: -Sol-gel prepared ferroelectrics and related materials. -Sol-gel processing of titanium oxides: photocatalyst and other applications. -Sol-gel prepared organic-inorganic hybrids and nanocomposites. -Sol-gel processing of porous materials: application to catalysts, enzymes, chemical analysis, sensors, and membranes. The goal of these four volumes is to disseminate the recent research results published in recent issues of Journal of Sol-Gel Science and Technology, which is a unique journal devoted to Sol-Gel.