Precipitated amorphous silica

Kea.tlte, Keatite has been prepared (65) by the crystallisation of amorphous precipitated silica ia a hydrothermal bomb from dilute alkah hydroxide or carbonate solutions at 380—585°C and 35—120 MPa (345—1180 atm). The stmcture (66) is tetragonal. There are 12 Si02 units ia the unit cell ttg = 745 pm and Cg = 8604 pm the space group is P42. Keatite has a negative volumetric expansion coefficient from 20—550°C. It is unchanged by beating at 1100°C, but is transformed completely to cristobahte ia three hours at 1620°C. 

Wessahm. [Degussa] Amorphous precipitated silica fex pesticides mdustry. 

CAS 112926-00-8 EINECS/ELINCS 231-545-4 Synonyms Amorphous silica gel Polyethylenimine-silica Precipitated silica Silica, amorphous precipitated Silica, amorphous, precipitated and gel Silica gel dessiccant Classification Mineral... 

Silica, amorphous precipitated Silica, amorphous, precipitated and gel. 

The choice of antiblocking additive depends on the polymer, the desired film quality, and whether there is a pigment. Several inorganic substances are used, including synthetic amorphous precipitated silica, diatomaceous earths, nepheline syenite, calcined clay, coated calcium carbonate, magnesium carbonate, magnesium sulphate, mica, talc and various zeolites. Calcium carbonate particles are approximately spherical, but silica ones are irregular mica forms sheets and talc is plate-like. 

Hydrophobic Silica. Amorphous, precipitated silica (particle size 1-2 pm) is commonly added to silicon oils, fats, waxes and aqueous mixtures for preparation of cost effective foam control products [IS, J9]. 

Kaye Disk Centrifuge. A device for particle-size analysis (1-50 pm) by means of a beam of light passed through a liquid suspension of the particles while the suspension is rotated in a transparent disk-shaped centrifuge. The prototype was designed by B. H. Kaye (Brit. Pat, 895,222,2/5/62) now made by Coulter Electronics Ltd., St. Albans, England. Keatite. A form of silica resulting from the crystallization of amorphous precipitated silica at 380-585°C and water pressures of 350-1250 bars sp. gr. 2.50. Named from its discoverer, P. P. Keat (Science, 120, 328,1954). 

Exposure to fiime and the precipitated silica (amorphous silica) causes fatal bronchial response as these are respirable. Repeated exposure dries the skin and causes mechanical irritation to eyes. Sol-gel silica, as an alternative to this, ceases the floating problem and avoids unnecessary contamination. 

Filler Carbon black Natural amorphous silica, precipitated silica, nonblack nanofiller Solvent Organic solvent Aqua-based solvent... 

Perchloryl fluoride Precipitated silica, see Silica, amorphous 3 13 6 25 3 13 6 26 ... 

Precipitated amorphous hydrated silica and fumed anhydrous silica, inorganic reinforcing agent. 

The marked difference in the relaxation times for the kaolinite and silica may be attributed to the nature of the surface. Intuitively, the hydrogen bonding which influences the increased structure at the kaolinite surface would be expected to give shorter values for the relaxation time. However this is not observed in the simulations. Instead, shorter values are seen for the silica surface which is a result of water molecules becoming trapped in the cage-like amorphous silica surface. This reflects experimental results where precipitated silica surfaces are microporous and water inclusion in the surface is common. 

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