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Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO 2, commonly found in nature as quartz. [5] [6] In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a
Fumed silica (CAS number 7631-86-9, also 112945-52-5), 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 ...
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.
Early research used an expensive additive called fumed silica, an amorphous form of silica made by combustion of silicon tetrachloride in a hydrogen-oxygen flame. Silica fume on the other hand, is a very fine pozzolanic, amorphous material, a by-product of the production of elemental silicon or ferrosilicon alloys in electric arc furnaces.
The original mass of flammable material and the mass of the oxygen consumed (typically from the surrounding air) equals the mass of the flame products (ash, water, carbon dioxide, and other gases). Lavoisier used the experimental fact that some metals gained mass when they burned to support his ideas (because those chemical reactions capture ...
This material which must have started out like unfired pottery was slip cast from fused silica. Then it was dried four days at 333 K before being tested. It was 9 inches in diameter and 1 inch thick, density 1.78 ⋅ cm −3. The first run went to 1317K and then on the second run the same insulator proved to be more conductive. 1959. [110 ...
They are excellent electrical insulators [2] and, unlike their carbon analogues, are non-flammable. Their temperature stability and good heat-transfer characteristics make them widely used in laboratories for heating baths ("oil baths") placed on top of hotplate stirrers, as well as in freeze-dryers as refrigerants.
Silica aerogels are the most common type of aerogel, and the primary type in use or study. [41] [57] It is silica-based and can be derived from silica gel or by a modified Stober process. Nicknames include frozen smoke, [58] solid smoke, solid air, solid cloud, and blue smoke, owing to its translucent nature and the way light scatters in the ...