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Chemical properties of silicon dioxide

Chemical properties of silicon dioxide

Chemical properties of silicon dioxide

Source:
2014/06/24 02:06
Relatively stable chemical properties. Not reacting with water. Is an acidic oxide, not with the general acid reaction. Gaseous hydrogen fluoride and silicon dioxide reaction to form four silicon fluoride. With the formation of hot concentrated alkali solution or molten alkali silicate and water. Reaction of silicate with various metal oxides at high temperature. Used for producing quartz glass, optical instruments, chemical containers, ordinary glass, refractory materials, optical fiber, ceramic, etc.. Properties of silica is inert, it was not associated with except Fluorine, hydrogen fluoride halogen, hydrogen halide and sulfuric acid, nitric acid, perchloric acid role (with the exception of hot concentrated phosphoric acid).
 
 
Common concentrated phosphate or pyrophosphate at high temperatures can be etching the silicon dioxide to generate heteropoly acid [3], high-temperature borate fusion or boron anhydride also etching the silicon dioxide, in view of the nature of borate can used for firing ceramic flux, in addition to the hydrogen fluoride can also can make the dissolved silica acid, generating soluble in the water fluoride silicate: 6HF+SiO2=H2SiF6+2H2O
 
 
Silica generally does not react with water, that is, the contact with water does not produce acid, but man-made provisions of the acid anhydride.
 
 
In the temperature range of interest in most microelectronic processes, the crystallization rate of silicon dioxide is low enough to be ignored.
 
 
Silica structure
 
Although the fused silica is not in a long range, it has a short ordered structure, which can be considered as the 4 oxygen atom on the vertex of the tetrahedral. The center of a polyhedron is a silicon atom.
 
 
In this way, each of the 4 oxygen atoms covalently bonded to the silicon atom approximation, satisfy the valence shell of silicon. If each oxygen atom is part of the two polyhedra, is the valence of oxygen has also been met. As a result known as the rules of quartz crystal structure.
 
 
In fused silica, some of the oxygen atoms become oxygen bridges, with two silicon atoms bonded together. Some oxygen atoms have no oxygen bridges, and only one silicon atom bonded.
 
 
It can be concluded that the thermal growth of silicon dioxide is mainly composed of polyhedral networks with arbitrary directions. Compared with the oxygen free bridge, the greater part of the oxygen bridge, the greater the adhesion of the oxide layer, and the smaller the tendency of damage. The ratio of aerobic bridge and oxygen free bridge is much greater than that of wet oxygen.
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