What is the structure of pyrogenic silica?

Silicon dioxide with branched chains on micro scale

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Not to be confused with silica fume

"Aerosil" redirects here. Not to be confused with aerosol

Fumed silica with surface area of 130 m2/g

Fumed silica (CAS number -52-5), also known as pyrogenic silica because it is produced in a flame, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk density and high surface area. Its three-dimensional structure results in viscosity-increasing, thixotropic behavior when used as a thickener or reinforcing filler.[1]

Properties

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Fumed silica has a very strong thickening effect. Primary particle size is 550 nm.[2] The particles are non-porous and have a surface area of 50600 m2/g. The density is 160190 kg/m3.

Production

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Fumed silica is made from flame pyrolysis of silicon tetrachloride or from quartz sand vaporized in a  °C electric arc.[3] Major global producers are Evonik (who sells it under the name Aerosil), Cabot Corporation (Cab-O-Sil), Wacker Chemie (HDK), Dow Corning, Heraeus (Zandosil), Tokuyama Corporation (Reolosil), OCI (Konasil), Orisil (Orisil) and Xunyuchem(XYSIL).[4]

Applications

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Fumed silica serves as a universal thickening agent and an anticaking agent (free-flow agent) in powders. Like silica gel, it serves as a desiccant. It is used in cosmetics for its light-diffusing properties. It is used as a light abrasive, in products like toothpaste. Other uses include filler in silicone elastomer and viscosity adjustment in paints, coatings, printing inks, adhesives and unsaturated polyester resins.[5] Fumed silica readily forms a network structure within bitumen and enhances its elasticity.[6]

Health issues

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Fumed silica is not listed as a carcinogen by OSHA, IARC, or NTP. Due to its fineness and thinness, fumed silica can easily become airborne, making it an inhalation hazard capable of causing irritation.

See also

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References

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Fumed silica (CAS number -52-5), also known as pyrogenic silica or colloidal silicone dioxide, is produced through flame hydrolysis synthesis in which silicon tetrachloride reacts with hydrogen & oxygen, and the SiO2 seed grows in size or aggregates.

SURFACE of FUMED SILICA

Fumed silica is produced at small particle sizes (around 7-40 nanometers), which makes it very reactive and gives it more surface area for chemical reactions. Its porous-structure powder.

Property of HIFULL Hydrophilic Fumed Silica

• Partical Size: Primary 7-20nm

• Aggregates (average)150-300nm

• Agglomerates average ): 1-50um

• Specific surface area (BET): 90-400 m2/g

• Tamped density: 40-120 g/l

• pH in 4% dispersion: 3.7-4.5

• Purity: SiO2 Content> 99.8%

• Sieve residue (45um): < 0.025%

• Loss on drying: < 0.5-1.5% @ 105/2h

• Loss on ignition: < 1% @/2h

• Hebei Silicon Research Electronic Materials Co., L supply professional and honest service.

  Crystal structure: amorphous

• Refractive index: 1.46

• Specific gravity: 2.2g/cm3

Property of HIFULL Hydrophobic Fumed Silica

• Surface Chemistry: surface silanol group( Si-OH) was reacted, show hydrophobicity; Low Moisture absorption

• Particle Size:treated based on hydrophilic fumed silica, increase of particle size accordingly

• Specific surface area (BET): 90-400 m2/g

• Tamped density: 40-120 g/l

• pH in 4% dispersion: 3.0-10

• Carbon Content: 0.5%-6%

• Sieve residue (45um): < 0.025%

• Loss on drying: < 0.1-1.5% @ 105/2h

• Loss on ignition: < 1% @/2h

• Crystal structure: amorphous

• Refractive index: 1.45-1.46

• Specific gravity: 2.2g/cm3

• HMDS
• DDS
• PDMS

Fumed Silica functions

Fumed silica has better performance in thickening, thixotropy, sag resistance, reinforcement and caking resistance. While precipitated silica is mainly used as a reinforcing agent for rubbers or friction agent in toothpaste.

Fumed SilicaVSPrecipitated Silica150-300 Nano meter AGGREGATES SIZE    1-100 Micron meter99.8%SILICA CONTENT90%90-400/gSPECIFIC SURFACE AREA50-600 /gLowMOISTURE CONTENT HighFumed silica is synthesized from the hydrolysis of high purity silane in a flame of oxygen and hydrogen at a very high temperature.  MANUFACTURING PROCESSPrecipitated silica is produced by the Controlled neutralization of dilute sodium silicate (water glass) by either concentrated sulfuric, hydrochloric or carbonic acids. High specific surface area, small particle sizeFEATURELow specific surface area, large particle sizeHas better performance in thickening, thixotropy, sag resistance, reinforcement, caking resistance; mainly used for industries that need high transparency, high purity & small surface area.FUNCTIONSPrecipitated silica is mainly used as natural rubber and synthetic rubber reinforcing agent, friction agent in toothpaste. Competitive price with international brandPRICELower than fumed silica

HIFULL manufactures more than 10 grades of hydrophilic and hydrophobic fumed silica for your special choice. For product TDS, MSDS or sample-testing, price quotation, please check Datasheet or leave message to us.

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My name is Van, Im the business manager of HIFULL, I have been in Fumed Silica Industry for more than 10 years. Feel free to contact me. Im happy to provide you the best service and products.

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