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<p>Tubular halloysite clay mineral and nanocrystalline TiO<sub>2 </sub>were incorporated in the preparation of nanocomposite films on glass substrates via sol-gel method at 450ºC. The synthesis involves a simple chemical method employing nonionic surfactant molecule as pore directing agent along with the acetic acid-based sol-gel route without addition of water molecules. Drying and thermal treatment of composite films ensure elimination of organic material and lead to the formation of TiO<sub>2</sub> nanoparticles homogeneously distributed on the surface of the halloysite. Nanocomposite films without cracks of active anatase crystal phase and small crystallite size on halloysite nanotubes are characterized by microscopy techniques and porosimetry methods in order to examine their structural properties. The composite halloysite-TiO<sub>2 </sub>films with variable quantities of halloysite were examined as photocatalysts to the discoloration of Basic Blue 41 azo dye in water. These nanocomposite films proved to be very promising photocatalysts and highly effective to dye’s discoloration in spite of small amount of halloysite/TiO<sub>2</sub> catalyst immobilized onto glass substrates. It also has been shown that the efficiency of the halloysite/TiO<sub>2</sub> films could be further improved when silver particles were deposited on their surface after successful adsorption from an aqueous solution of a silver salt and UV reduction of the adsorbed ions.</p>
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AbstractTo improve the processing of silicon nitride, boehmite and yttrium oxide were coated on silicon nitride particles by an aqueous sol-gel method. It is shown that boehmite and Y2O3 can be coated on Si3N4 particles from aqueous solutions. However, the Y2O3 coating is not as complete as boehmite coating. The coating of a yttria coating followed by a boehmite coating was attempted and the TEM showed a coating twice as thick as the Y2O3 or AlOOH coating. Hydrothermal treatment of yttrium nitrate hydrous hydroxide results in the formation and growth of Y(OH)3 fibers which can be calcined and transformed into Y2O3 fibers at 500°C.
Nanocrystalline TiO2 and Halloysite clay mineral composite films prepared by sol-gel method: Synergistic effect and the case of silver modification to the photocatalytic degradation of Basic Blue- 41 azo dye in water.