Structural considerations about SiO2 glasses prepared by sol-gel

Durán, Alicia; Serna, C. J.; Fornés, Vicente; Navarro, José María Fernández

doi:10.1016/0022-3093(86)90112-2

Cited by 261 publications

(126 citation statements)

References 9 publications

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“…It has been reported that the signal at the wave number around 800 cm nates from Ti-O-Ti. [28][29][30] By combining the results of FTIR and XRD, one can see that silica exists as a segregated amorphous phase in the anatase titania. The presence of water is evidenced by the appearance of the bending mode at 1640 cm À1 and the stretching mode at 3400 cm…”

Section: Resultsmentioning

confidence: 99%

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Zhang

et al. 2010

Chemistry A European J

319

203

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Core–shell structured Fe3O4/SiO2/TiO2 nanocomposites with enhanced photocatalytic activity that are capable of fast magnetic separation have been successfully synthesized by combining two steps of a sol–gel process with calcination. The as‐obtained core–shell structure is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, and an outer layer of TiO2 nanocrystals with a tunable average size. The convenient control over the size and crystallinity of the TiO2 nanocatalysts makes it possible to achieve higher photocatalytic efficiency than that of commercial photocatalyst Degussa P25. The photocatalytic activity increases as the thickness of the TiO2 nanocrystal shell decreases. The presence of SiO2 interlayer helps to enhance the photocatalytic efficiency of the TiO2 nanocrystal shell as well as the chemical and thermal stability of Fe3O4 core. In addition, the TiO2 nanocrystals strongly adhere to the magnetic supports through covalent bonds. We demonstrate that this photocatalyst can be easily recycled by applying an external magnetic field while maintaining their photocatalytic activity during at least eighteen cycles of use.

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Section: Resultsmentioning

confidence: 99%

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Zhang

et al. 2010

Chemistry A European J

319

203

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“…The symmetric stretching vibrations of Si-O-Si appear at around 790 cm -1 . Furthermore, the Si-O inplane stretching vibrations of the silanol Si-OH groups appear at around 934 cm -1 [8][9][10]. 5 nm) .…”

Section: Resultsmentioning

confidence: 98%

Growth of Carbon Nanotube Forests on Carbon Fibers with a SiO₂ Interlayer

et al. 2012

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“…Therefore, FO process for desalination may not be attractive. The less common membrane distillation (MD) process [46,47] has also been employed for desalination application. [85,87].…”

Section: Membrane Process Performance and Discussionmentioning

confidence: 99%

High performance ES40-derived silica membranes for desalination

Wang¹

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Access to potable water has become one of the top 10 global problems facing our contemporary society. Desalination of vast amounts of seawater is a promising measure to ameliorate this stress.Numerous thermal and membrane processes have been employed to desalt seawater, of which reverse osmosis (RO) using polymeric membranes is the most mature technology and has been regarded as the benchmark in current desalination technologies. However, due to the high pressure requirement for RO operation, other membrane processes, such as membrane distillation and pervaporation have been developed as the alternatives to further reduce the energy cost.Furthermore, due to the lack of chemical/thermal stability and high tendency to scaling and fouling of polymeric membranes, novel inorganic membranes, in particular silica derived membranes, are emerging as potential candidates for desalination. The majority of published works on silica membranes utilizes tetraethyl orthosilicate (TEOS) as the silica precursor and interlayers are generally required to reduce the roughness of the porous substrates, followed by 4 to 6 thin-film coatings and calcinations with heating rates of 1-2 º C min -1 to form defect free silica membranes, which consume 10-14 days with extra cost. Therefore, the major target of this research is to produce interlayer-free silica membranes fabricated by rapid thermal processing (RTP) for desalination application.Ethyl silicate 40 (ES40) is used as precursor to prepare silica membranes in this work owing to their superior thermal stability as compared to the TEOS analogous product. Firstly, the sol-gel processing of ES40 was investigated in this thesis. At different temperatures and H 2 O/Si ratios, ES40 underwent various degrees of phase separation behaviour and sol-gel reactions. It was found that the hydrolysis and condensation reactions decreased with decreasing reaction temperature.Dense silica structures were obtained using low H 2 O/Si ratios, whereas higher porosity was produced from a phase-separated sol-gel system with high H 2 O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, leading to stronger silica matrices which were more resistant to densification.The second part of this work is focused on improvement of the hydrostability of ES40-derived silica membrane materials by adjusting the reactant ratios of sol-gel synthesis process, as the low resistance of silica membranes to water vapor attack, which induce enlargement of the pore size followed by failure in salt rejection, can be detrimental to desalination performance. Investigations were carried out on the effects of reactant ratios on the microstructure of the silica matrices and their hydrothermal stability under harsh conditions (550 °C, 75 mol% vapour). The most hydrothermally stable matrix was obtained by decreasing the ethanol ratio whilst increasing water II and acid ratios. The improved hydrothermal stability was attributed to the further transition of silanol to siloxa...

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Structural considerations about SiO2 glasses prepared by sol-gel

Cited by 261 publications

References 9 publications

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Growth of Carbon Nanotube Forests on Carbon Fibers with a SiO₂ Interlayer

High performance ES40-derived silica membranes for desalination

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Structural considerations about SiO2 glasses prepared by sol-gel

Cited by 261 publications

References 9 publications

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Growth of Carbon Nanotube Forests on Carbon Fibers with a SiO2 Interlayer

High performance ES40-derived silica membranes for desalination

Contact Info

Product

Resources

About

Growth of Carbon Nanotube Forests on Carbon Fibers with a SiO₂ Interlayer