Silica range

Crystalline silicon dioxide range : Crystalline silicon dioxide is one of the most commonly encountered substances in both daily life and in electronics manufacturing. Crystalline silicon dioxide (in several forms: quartz, cristobalite, tridymite) is an important constituent of a great many minerals and gemstones, both in pure form and mixed with related oxides. Beach sand is mostly silica. Crystalline silicas show discrete reflections in X-ray diffraction from the internal planes formed by the orderly pattern of atoms. The working of silica into glass (usually by the addition of natron -- sodium oxide -- to lower the melting point) has been known since antiquity, with polished glass lenses in eyeglasses and optical instruments dating back more than 5 centuries.

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Non-Crystalline range : Non-crystalline, or amorphous silica, is usually prepared by vapor-phase hydrolysis, precipitation or other processes that ensure the absence of crystalline free silica. Three forms of synthetic amorphous silica are classified according to their method of preparation: silica gel (silica G), precipitated silica (silica P) and fumed silica (silica F). There are several naturally-occurring and synthetic amorphous silicas, namely diatomaceous earth, precipitated silica, silica gel, fumed silica and silica fume (thermally generated). In amorphous silica, X-rays are scattered randomly and no discrete reflections are seen. All types of amorphous silica can be converted to crystalline forms when heated to a sufficiently high temperature.

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Fumed silica range : Fumed silica is derived from vapor-phase hydrolysis of a silicon-bearing halide, such as silicon tetrachloride. It is the byproduct of a high-temperature process when elemental silicon is produced by reacting coke and silica sand (crystalline) in an electric arc furnace. It offers primary particles with diameters from 5 to 40 n.m., as well as a low density of silanois (#2.5/n/m.2), and very few impurities.

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Precipitated silica range : in precipitated silica, the reaction mixture is held in the alkaline pH region, and offers limited aggregates of primary particles with a diameter of >5 n.m., and specific surface area (<350 m2.g). The production of precipitated silica starts with the reaction of an alkaline silicate solution with a mineral acid. Sulfuric acid and sodium silicate solutions are added simultaneously with agitation to water. The resulting white precipitate is filtered, washed and dried in the manufacturing process. Precipitated silica's basic characteristics, which can be altered during the precipitation process, are particle size distribution, porosity, specific surface area and purity.

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Silica gel range : for silica gel, the reaction mixture is held in the acidic pH region, and here precipitated silica means a three-dimensional network of particles with low diameter (3 n.m.), with a high specific surface area (>350 m2/g). Packets of silica gel are found in all sorts of products because silica gel adsorbs and holds water vapor. In fact, you will find little silica gel packets in anything that would be affected by excess moisture or condensation. Silica gel is nearly harmless and that is why you find it in food products. Silica gel can adsorb about 40% of its weight in moisture and can take the relative humidity in a closed container down to about 40%. Once saturated you can drive the moisture off and reuse silica gel by heating it above 300 degrees F.

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Colloidal silica range : colloidal silica has found widespread use for diverse materials in many industries. It is an aqueous, colloidal dispersion of chemically inert silica particles. The particles cut effectively, without deformation, because they combine individual crystals with a large exposed surface area and a high pH activation. Colloidal silica has been used successfully on a variety of materials including aluminium and aluminium alloys, titanium and titanium alloys, copper and copper alloys, lead and lead alloys, zirconium alloys, semiconductors, printed circuit boards, steels and coal

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The use of silica :
Tire & Rubber Goods (Manufactured Rubber Goods & Tire)
Polymer Performance (Organic Rubber For Footwear, Plastics and TPE, Polymer for Membranes
Silicone Elastomers), Nutritions & Industrial (Specialties, Nutritions, Industrial Specialties), Performance Silicas (Dentifrice)
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On Rhodia-silica.com, find content about :
Use of Silica, silica products, silica range, silica for industry, amourphous silica, green tire, HDS, performance silica, precipitated silica, silica characteristics (Ph, technology, density), silica expertise, silica functions, silica gel, silicone dioxide, silica utilization.