| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 105 === This research aims to prepare hydrophobic TiO2 particles by adsorption of surfactant molecules so that macroporous TiO2 foams with a high porosity and a reasonable mechanical strength can be prepared by Pickering emulsion followed then by sintering at elevated temperatures. Microstructure and oil-absorption performance of the TiO2 foams have been examined. The surface of TiO2 particles bears negative surface charge in water over a broad pH range. This leads to a preferential adsorption of cationic surfactant molecules on the particle surface with a contact angle greater than 50o. Among the surfactant examined, benzethonium chloride (BZT, C27H42ClNO2) is the most effective; to which, the originally hydrophilic TiO2 surface with a contact angle of 16o becomes hydrophobic with a contact angle of 86o. The hydrophobized TiO2 particles have been prepared into aqueous TiO2 colloids with a fixed solids concentration of 5 vol%, along with addition of agar (Agar, C12H18O9) upon subjected to mechanical frothing and freeze gelcasting. The thus-prepared foams are then dried and sintered at 1000oC to obtain the finished product. The sintering makes the TiO2 particles of anatase phase to become a mixture of anatase and rutile phase. Porosity of the sintered foams ranges from 75 to 83%, while flexural strength varies from 38 to 210 kPa. The highest oil-absorption rate of the sintered TiO2 foams is found to be 0.96 when the foam was prepared with the BZT concentration of 0.25 cmc (Note: cmc is the critical micelle concentration). The sintered foams have been modified by the second BZT adsorption through vacuum infiltration and drying, and the oil-absorption rate increases from 0.7 to 1.81.
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