Orthosilicate

Orthosilicate anions Silicon in end position Silicon in middle Branching silicons Cross-linked silicons Methyl siloxanes (CH3)2Si—O— (end position)... 

Normal and dibasic lead stearate have a stabilising effect but their main uses are as lubricants (see section 12.5.4). Lead silicate is sometimes used in leathercloth formulations but is today of little importance. Other lead compounds now of negligible importance are coprecipitated lead orthosilicates and lead salicylate. 

Orthosilicates are derivatives of orthosilicic acid Si(OH)4. The most common is tetraethyl orthosilicate Si(OC2H04, often called TEOS, an acronym that also fits the alternative way of naming such a compound, tetraethoxysilane. Thus orthosilicates are actually a sub-set of the larger class of XRSi(OR )3 silanes, where the XR group is also an alkoxy group. The XR and OR groups do not have to be the... 

Various inorganic esters have been claimed as coupling agents for reinforced plastics, including aminobenzyl phosphonates, dicetylisopropylborate, alkoxy compounds of aluminum, zirconium and titanium, zircoaluminates, and numerous substituted titanates [1]. These metal alkoxides could function in a similar manner to the orthosilicates by reacting with hydroxylated substrates. Like the simple orthosilicates such as tetraethyl orthosilicate (TEOS), it is less evident how an-... 

Tetraethyl orthosilicate (104.2 g) and deuterium oxide (40 g) are stirred in a stoppered distillation flask at room temperature until a viscous, miscible solution is obtained (approximately 24 hr). (A small amount of acid catalyst, such as deuteriochloric acid, speeds up the reaction considerably. ) A distillation head and a receiver cooled in a dry ice-acetone bath are attached and the solution is distilled at 2 mm pressure until no further product is obtained. A 90% yield of ethanol-OD is obtained having an isotopic purity equal to that of the deuterium oxide used. ... 

Propionic ether 2-Ethylhexenal I-Ethoxypropane Ethyl orthosilicate... 

Silicate binders are used in conjunction with zinc powder to give paints of excellent corrosion resistance. The organo-silicates, e.g. ethyl orthosilicate, are most commonly used. The full potential of this type of binder has probably not yet been exploited. 

MooP76 Moore, P. B., Asaki, T. The crystal structure of bredigite and the genealogy of some alkaline earth orthosilicates. American Mineralogist 61 (1976) 74-87. 

A. Determination of silica in a soluble silicate Discussion. Most of the silicates which come within the classification of soluble silicates are the orthosilicates formed from SiO units in combination with just one or two cations. More highly condensed silicate structures give rise to the insoluble silicates. 

Orthosilicates are not suitable for corrosion inhibitor purposes, and metasilicates are not generally used because they tend to increase the caustic alkalinity too much, leading to the potential for caustic-induced problems. However, glassy polysilicates are widely used. They have inhibition properties similar to those of polyphosphates and also have an indefinite crystalline structure. 

Polysilicates are effective in potable HW systems and provide threshold effect protection against hardness destabilization and red water. They also function by laying down a protective calcium silicate film. Polysilicates used for this type of application typically require a dose rate of 8 to 15 ppm Si02 above that of the natural orthosilicate found in the MU water. Where polysilicates are employed for dualtemperature and LPHW systems, however, the silicate reserve required is higher and ranges from 50 to 150 ppm. 

Metasilicic acid, H2Si03, and orthosilicic acid, H4Si04, are weak acids. However, when a solution of sodium orthosilicate is acidified, instead of H4Si04, a gelatinous precipitate of silica is produced ... 

The silicates which will occur are orthosilicates, R++2Si04, metasilicates, R++Si03, etc. This is verified by observation no basic silicates of such cations are known, although many normal silicates such as forsterite Mg2Si04, etc., exist. 

MOCVD of Silica. Considerable work is being done with the MOCVD of silica, which is rapidly expanding in semiconductor processing. The most common MOCVD reaction is the decomposition of tetraethyl orthosilicate (TEOS), shown in simplified form as follows ]... 

A widely used glass is phosphosilicate (PSG), which is used extensively in semiconductor devices as a passivation and planarization coating for silicon wafers. It is deposited by CVD by the reaction of tetraethyl orthosilicate (TEOS) (C2H50)4Si, and trimethylphosphate PO(OCH3)3, in a molecular ratio corresponding to a concentration of 5 to 7% P. Deposition temperature is usually 700°C and pressure is 1 atm. 

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