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Preparation and photocatalytic application ot TiO2 film coated alumina foam

Ceramic foams are lightweight materials with open or closed cellular structure. Due to their specific properties such as low density, high chemical and temperature resistance, pore interconnectivity and permeability, ceramic foams have found a wide range of applications, e.g. catalyst supports, molten metal and hot gas filters, thermal insulators, biomedical implants and lightweight structural components. In the present work, TiO2 film was deposited on alumina foam substrate by sol-gel technique. Firstly, alumina foam was prepared by the replica method in witch polyurethane sponge with a pore density of 17 ppi (pores per linear inch) was used as a template. Polyurethane template was repeatedly immersed in an aqueous alumina suspension containing 60 wt. % solid and following additives: commercial carbonic acid based polyelectrolyte Dolapix CE 64 as a dispersant, polyvinyl alcohol as a binder and Foamaster MO 2111 as a defoaming agent. After each immersion, centrifugation was conducted and the sample was dried to remove the excess suspension and to provide uniformly coated structure. Finally, a ceramic replica of the polyurethane template was obtained by pyrolysis and sintering. The slow heating rate of 1 oC/min to 600 oC and 5 oC/min to 1600 oC was applied to burn out the organic materials without collapsing of the structure. The sintering process was completed by holding the sample at 1600 oC for 1 h. For the preparation of TiO2 sol, the following components were used: titanium (IV) isopropoxide as the titanium precursor, propanol as a solvent, nitric acid as a catalyst and acetylacetone for complexation. The coating process was performed by dipping 17 ppi alumina foam into TiO2 sol followed by drying in an air oven at 80 oC. The coated sample was calcined at 500 oC for 1h. Crystal structure of TiO2 and alumina were identified by X-ray diffraction and the morphological features of the TiO2 coated alumina foam were characterized with a scanning electron microscope. The photocatalytic activity of the TiO2 film was evaluated by the photocatalytic degradation of synthetic Congo Red dye with UV light radiation at 25 °C. Photocatalytic activities of the films were monitored by means of UV/VIS spectrophotometry and total organic carbon measurement and results show the dye was efficiently degraded. Finally, the as-derived titania-alumina composite foam may be considered as valuable photocatalytic substrate.

Alumina foam, sol-gel TiO2, Photocatalysis

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