Thermal evolution of mesoporous titania prepared by CO2 supercritical extraction

Tursiloadi, Silvester; Yamanaka, Yu; Hirashima, Hiroshi

doi:10.1007/s10971-006-7849-1

Cited by 12 publications

(4 citation statements)

References 10 publications

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“…A good linear relationship between ln V and ln[ln( P 0 / P )] can be discerned for the two isotherms derived from the as-deposited film and that heated at 450 °C. The corresponding values of D s were determined to be 2.70 and 2.58, respectively, both of which fallen well into the range of 2 < D s < 3 ( − ). The values of D s obtained here are much lager than those obtained by Yao et al for the porous polycrystalline titania derived by sol−gel ().…”

Section: Resultsmentioning

confidence: 71%

“…Surface irregularity, which can be described by the surface fractal dimension, D s , has been recognized to play a crucial role in certain phenomena such as adsorption/desorption, diffusion, and catalysis (). D s is dependent on surface roughness and surface area ( − ) and can be obtained using the N 2 adsorption isotherm with the following equation, according to the Frenkel−Halsey−Hill (FHH) theory (), where V is the adsorbed volume of N 2 at standard temperature and pressure (STP), P / P 0 is the relative pressure, and C is a constant. Equation 1 holds only when the adsorption mechanism occurring in the mesopores is capillary condensation ().…”

Section: Resultsmentioning

confidence: 99%

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Photodegradation of Rhodamine B in Water Assisted by Titania Nanorod Thin Films Subjected to Various Thermal Treatments

2007

Environ. Sci. Technol.

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Well-crystallized titania nanorod thin films with high specific surface areas were synthesized through in situ oxidation of metallic titanium substrates with hydrogen peroxide solutions at a low temperature of 80 degrees C. The effects of thermal treatments on the ability of the thin films to assist photodegradation of rhodamine B in water were studied in detail. It is found that, due to a unique nanofeature, the titania nanorod film retained its small grain size and high specific surface area during the subsequent thermal treatment for up to 450 degrees C, which further improved the crystallinity of titania. In addition, upon heating to 450 degrees C, the nanorods still possessed a high surface fractal dimension, which is an indication of high surface roughness and surface area. As a result, the photocatalytic activity of the titania nanorod film is found to increase with an increasing heating temperature for up to 450 degrees C. The subsequent thermal treatment at temperatures beyond 450 degrees C decreased the photocatalytic activity, because of the significantly reduced specific surface area. The current investigation provided a simple and easily scaled-up approach to produce photocatalysts for efficient removal of dye effluents in wastewater.

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Section: Resultsmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Photodegradation of Rhodamine B in Water Assisted by Titania Nanorod Thin Films Subjected to Various Thermal Treatments

2007

Environ. Sci. Technol.

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“…CO 2 was chosen because of its nonflammability, non-toxicity, low cost, near-ambient critical temperature and low pressure (304.1 K and 73.8 bar). The efficient method has been widely applied for the removal of cationic, anionic and neutral templates from silicabased mesoporous materials [31][32][33][34][35], however few from mesoporous TiO 2 [36,37]. High quality pore structure and removal effectiveness (over 80%) have been attained through supercritical fluid extraction with the promotion of physical properties of the products compared to calcined materials.…”

Section: Introductionmentioning

confidence: 99%

Surfactant removal from mesoporous TiO2 nanocrystals by supercritical CO2 fluid extraction

Nguyen‐Phan¹,

Pham²,

Kim³

et al. 2010

Journal of Industrial and Engineering Chemistry

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“…Aerogels are a class of materials sometimes described as a new state of matter because their properties differ from those of equivalent bulk materials due to their nanostructured backbone and porosity and their high porosity (up to and above 99%, typically around 95%). Aerogels were first reported by Kistler in 1932 and are still being studied extensively nowadays. , Aside from silica aerogels, the pioneering and most commonly explored chemistry for those materials, other chemical systems have since then been studied as aerogel candidates, including metals − and metal oxides, polymers − and biopolymers, and carbon-based materials − and their hybrids. The motivation behind exploring these different chemistries for aerogels is about elaborating interesting and innovating microstructures, chemistries, properties, and applications.…”

Section: Introductionmentioning

confidence: 99%

Silica–Resorcinol–Melamine–Formaldehyde Composite Aerogels as High-Performance Thermal Insulators

et al. 2022

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Here, we report the gelation and supercritical drying of ethanol-based silica–resorcinol–melamine–formaldehyde (RMF) composite aerogels with relative concentrations of initial reagents ranging from neat silica to neat RMF alcogels. The as-prepared materials are subsequently supercritically dried with carbon dioxide. Their properties include a thermal conductivity in the 15–20 mW·m –1 ·K –1 range even with a silica content as low as 20% wt . The possible reasons behind this interesting insulation performance and the mechanisms leading to the underlying gel structure are discussed in depth. A focus is made on the different gelation modes happening between the RMF and silica phases, from a coating of silica surfaces with RMF species to discontinuous RMF particles within a silica backbone and a continuous RMF backbone with isolated silica particles. The implications in terms of mechanical properties and thermal conductivity are elaborated upon. The initial ratio of silica–RMF species in this ethanol-based synthesis affects the micro- and macrostructure of the composites, resulting in materials with drastically different pore structures and thus an interesting array of possibilities for a new class of silica-organic composite aerogels, based on a sol–gel process.

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Thermal evolution of mesoporous titania prepared by CO2 supercritical extraction

Cited by 12 publications

References 10 publications

Photodegradation of Rhodamine B in Water Assisted by Titania Nanorod Thin Films Subjected to Various Thermal Treatments

Photodegradation of Rhodamine B in Water Assisted by Titania Nanorod Thin Films Subjected to Various Thermal Treatments

Surfactant removal from mesoporous TiO2 nanocrystals by supercritical CO2 fluid extraction

Silica–Resorcinol–Melamine–Formaldehyde Composite Aerogels as High-Performance Thermal Insulators

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