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The initial silica nanoparticles are in an amorphous crystalline phase and the solvent is composed of trimethylsilyl chloride (TMCS) and ethyl alcohol. To synthesize hydrophobic nanostructured silica using this method, the colloid precursor containing the solvent and silica particles is sprayed by an aerosol generator.
In contrast, the oxide polystyrene composites are more durable than the gel-based coatings, however the process fof applying the coating is much more involved and costly. Carbon nano-tubes are also expensive and difficult to produce with current technology. Thus, the silica-based gels remain the most economically viable option at present.
The Stöber process is a chemical process used to prepare silica (SiO 2) particles [1] of controllable and uniform size [2] for applications in materials science.It was pioneering [3] when it was reported by Werner Stöber and his team in 1968, [1] and remains today the most widely used wet chemistry synthetic approach to silica nanoparticles. [3]
Using silica nano-particles is also of interest to develop transparent hydrophobic materials for car windshields and self-cleaning windows. [58] By coating an already transparent surface with nano-silica with about 1 wt%, droplet contact angles can be raised up to 168° with a 12° sliding angle.
Mesoporous silica is a form of silica that is characterised by its mesoporous structure, that is, having pores that range from 2 nm to 50 nm in diameter. According to IUPAC's terminology, mesoporosity sits between microporous (<2 nm) and macroporous (>50 nm). Mesoporous silica is a relatively recent development in nanotechnology.
Silica (SiO2) is present in conventional concrete as part of the normal mix. However, one of the advancements made by the study of concrete at the nanoscale is that particle packing in concrete can be improved by using nano-silica which leads to a densifying of the micro and nanostructure resulting in improved mechanical properties.
These products are often called precipitated silica or silica sols. Hydrogen ions from the surface of colloidal silica tend to dissociate in aqueous solution, yielding a high negative charge. Substitution of some of the Si atoms by Al is known increase the negative colloidal charge, especially when it is evaluated at pH below the neutral point.
Schematic representation of the different stages and routes of the sol–gel technology. In this chemical procedure, a "sol" (a colloidal solution) is formed that then gradually evolves towards the formation of a gel-like diphasic system containing both a liquid phase and solid phase whose morphologies range from discrete particles to continuous polymer networks.
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