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Colloidal silica gel with light opalescence. Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum.
Silica is an occupational hazard for people who do sandblasting or work with powdered crystalline silica products. Amorphous silica, such as fumed silica, may cause irreversible lung damage in some cases but is not associated with the development of silicosis.
Colloidal silicas are most often prepared in a multi-step process where an alkali-silicate solution is partially neutralized, leading to the formation of silica nuclei. The subunits of colloidal silica particles are typically in the range of 1 to 5 nm. Whether or not these subunits are joined depends on the conditions of polymerization.
The lowest-density silica nanofoam weighs 1,000 g/m 3, [58] which is the evacuated version of the record-aerogel of 1,900 g/m 3. [59] The density of air is 1,200 g/m 3 (at 20 °C and 1 atm). [60] The silica solidifies into three-dimensional, intertwined clusters that make up only 3% of the volume. Conduction through the solid is therefore very low.
Precipitated silica is an amorphous form of silica (silicon dioxide, SiO 2); it is a white, powdery material. Precipitated silica is produced by precipitation from a solution containing silicate salts. The three main classes of amorphous silica are pyrogenic silica, precipitated silica and silica gel.
In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is characteristic of a crystal. The terms " glass " and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo ...
An amorphism, in chemistry, crystallography and, by extension, to other areas of the natural sciences is a substance or feature that lacks an ordered form. In the specific case of crystallography, an amorphic material is one that lacks long range (significant) crystalline order at the molecular level.
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.