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This report presents a novel synthesis method of alumina nanofibers at moderate conditions in aqueous systems through a surfactant-directed crystal growth process. In the presence of polyethylene oxide (PEO) surfactants, boehmite nanofibers of about 3 nm thick and 30-60 nm long formed from aluminium hydrate colloids. During the subsequent heating, the surfactant was evaporated and boehmite nanofibers were converted into γ-alumina nanofibers. The function of the PEO surfactant and the formation mechanism of the nanofibers are discussed. Alumina nanofibers are an ideal structural reinforcement for various nanocomposite materials. They are potential adsorbents with high adsorption capacity. Furthermore, their unique structure exhibits strong resistance to heating at high temperatures. The BET surface area of a typical sample after heating at 1200°C is as high as 68 m2/g. This makes the material very promising as excellent substrates for catalysts of high thermal stability.
A novel synthesis route of metal oxide nanoparticles dispersed in a silicate framework is reported here. This composite nanostructure is highly thermally stable and porous, rendering large surface area and rich surface chemistry promising for catalytic applications. Aqueous solutions of metal salts were used as the precursors of the nanoparticles, and added in an aqueous dispersion of synthetic clay, laponite, in which the clay exists in exfoliated silicate sheets. Acid leaching of the clay sheets occurs in the reaction due to the strong acidity of the metal salt solution. Meanwhile, the metal hydrate ions polymerise because of the high pH of the clay dispersion and condense on the leached silicates. This mechanism is distinctly different from conventional pillaring process. The nanocomposites of various oxides and binary oxides were synthesised. By introducing polyethylene oxide surfactants, we obtained mesoporous nanocomposites with very large surface areas (400-900 m2/g) and porosity. These nanocomposites are superior catalysts or catalyst supports over of microporous pillared clays [1-3] due to their structure and surface properties.
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