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Crystalline TiO 2 films have been deposited on several substrates (glass, F-doped SnO 2covered glass, and silicon wafers) by a drain-coating method from a colloidal anatase aqueous solution. The process is performed at low-temperature, 333 K, in open atmosphere. The colloidal TiO 2 consists on anatase nanoparticles of about 9 × 5 nm size, stabilized by tetrabutylammonium cations (TBA + ). This colloid has also been obtained under mild conditions (i.e., low temperature and ambient pressure) by hydrolysis of tetraisopropyl orthotitanate (TIP) in the presence of (TBA)OH and subsequent treatment by microwave radiation to enhance crystallization. Different film thicknesses have been obtained by consecutive deposition processes. Titania films thus obtained were transparent and showed good adherence. FT-IR analysis of the films reveal that TBA cations were not trapped in the film during the deposition process. No further thermal posttreatment was required to eliminate organics from the films or to induce titania crystallization. The photocatalytic activity of as-deposited titania has been assessed by the photodegradation of salicylic acid in aqueous solution under aerated conditions.

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This study aims to analyze the effects of supercritical carbonation (CO2 at 20 MPa and 318 K) on the physicochemical properties of ordinary Portland cement pastes. The evolution of the main crystalline phases of the cement pastes during carbonation was determined by means of X-ray diffraction and thermogravimetric analysis. The pore structure was analyzed by low-temperature N2 adsorption−desorption and mercury intrusion porosimetry techniques. Finally, the microstructure of the samples was observed by using scanning electron microscopy coupled with energy-dispersive X-ray detection for chemical analysis. For a natural carbonation process, diffusion of CO2 into the pores of the cement paste is considered as the rate-controlling step. Instead, the accelerated reaction kinetics of calcium carbonate precipitation in the supercritical process was chemically controlled by the detachment of calcium ions from solid portlandite or CSH gel. The total pore volume of the studied cement pastes decreased with carbonation, which was associated with the deposition of the formed CaCO3. Samples carbonated under the supercritical conditions developed a higher volume of gel pores than those obtained by natural carbonation.