Silicon dioxide fused

Silicon Dioxide Fuse 1 g of sample, accurately weighed, with 10 g of sodium bisulfate, NaHS04H20, contained in a 250-mL high-silica glass Erlenmeyer flask. While swirling the flask, heat it gently over a Meker burner until decomposition and fusion are complete and the melt is clear, except for the silica content, and then cool. 

The model of two-level systems was suggested for amorphous silicon dioxide (fused quartz) where the increase of the distance R between Si atoms compared to that of the crystal was found [191]. Due to the extention of bonds, the O atom in the chain Si-O-Si has several equilibrium positions. 

Amorphous silica, ie, silicon dioxide [7631-86-9] Si02, does not have a crystalline stmcture as defined by x-ray diffraction measurements. Amorphous silica, which can be naturally occurring or synthetic, can be either surface-hydrated or anhydrous. Synthetic amorphous silica can be broadly divided into two categories of stable materials (1) vitreous silica or glass (qv), which is made by fusing quart2 at temperatures greater than approximately 1700°C (see Silica, vitreous silica), and microamorphous silica, which is discussed herein. 

The key to the extraordinary power of these fibers is their fabulous purity. A triumph of modern chemistry, they are made of fused silica, essentially pure silicon dioxide, Si02. Thanks to this superpure glass, fiberoptic cables can snake their way across the ocean floor with virtually no discernible effect on their surroundings. 

Silicon glass is made by fusing pure quartz crystals or glass sand (impure crystals), and it is typically about 99.8% silicon dioxide. It is high-melting and difficult to fabricate. 

In 1992, R.M. Laine (University of Michigan, Ann Arbor) announced the development of a process that transforms sand and other forms of silica into reactive silicates that can be used to synthesize unusual silicon-based chemicals, polymers, glasses, and ceramics. The Lame procedure produces pentacoordinate silicates directly from low-cost raw materials—silicon dioxide,ethylene glycol, and an alkali base. The mixture is approximately a 60 1 ratio of silica gel, fused silica (or sand) to metal hydroxide and ethylene... 

The mineral quartz is crystallized silicon dioxide. Sea sand consists mostly of rounded grains of broken quartz. If finely ground quartz or sand is fused for a long time with sodium carbonate, the weaker, but non-volatile, acid anhydride displaces the carbon dioxide, and sodium silicate is obtained. This is a glass-like substance, which, however, can slowly be dissolved by water heated under pressure. The solution so obtained is evaporated to a sirup-like consistency and is sold on the market under... 

OPTOCIL OFTOCIL (QUARTZ) QG 100 QUARTZ GLASS QUARTZ SAND RANCOSIL RD 8 RD 120 S-COL SGA SILICA, AMORPHOUS-FUSED (ACGIH) SILICA, FUSED SILICA, FUSED (OSHA) SILICA, VITREOUS (9CI) SILICON DIOXIDE... 

Discussion of Experiment 140. — When silicon dioxide is fused with alkaline carbonates, an alkaline silicate is formed. The alkaline silicates are soluble in water, and when hydrochloric acid is added to such a solution, the gelatinous precipitate formed is a silicic acid having the formula H2Si03 (probably). This acid is decomposed by heat into silicon dioxide and water, thus —... 

Q Silicon dioxide (sand), sodium oxide, and potassium oxide formed in the inflator fuse into glass. 

An electrocyclization of the 1,3,5-triene 12 was employed in the stereoselective synthesis of ( )-pallescensin (ll)95. Thermolysis of furan 12 in xylene (200°C) presumably forms the intermediate 13 via 1.6-ECRC, how ever 13 is not observed, rather it undergoes a suprafacial [1,5] hydrogen shift to afford the cts-fused tricyclic 14. The synthesis of ( )-pallescensin (11) required the trans-fused tricycle 15 rather than the cis, and it was found that this desired stereoisomer could be obtained w hen the 1,6-ECRC was carried out in the presence of silica gel. It was reasoned that the mildly acidic silicon dioxide could reasonably effect the acid-catalyzed epimerization of 14 to 15. Reduction and protodesilylation of 15 completed the synthesis of 11. 

Sodium silicates are made by fusing (melting) sand (silicon dioxide) and soda ash (sodium carbonate) or sodium hydroxide in a gas-fired open hearth furnace, somewhat similar to the furnaces used in the manufacture of steel. The products of this reaction are lumps of sodium silicate that are broken apart and dissolved in a stream of hot steam. The proportions of sand and soda ash used, the temperature of the reaction, and the amount of water that remains in the final product all determine the physical properties of the final product. 

SYNONYMS amorphous quartz, amorphous silica, cryptocrystalline quartz, fused quartz, fused silica, fuselex, microcrystalline quartz, quartz, glass, quartz sand, silicon dioxide, silicone dioxide, suprasil, vitreous silica. 

Silicon dioxide (vitreous) [Fused silica] OjSi 60676-86-0 0.1 mg/m ... 

These consist of fused silica (silicon dioxide), alkali glass or borate glass. Their ID varies between 30 and 500 pm. Column lengths are usually between 1 and 100 m. 

Silicon dioxide is a form of pure glass with a melting temperature of 1,730 °C which is similar to fused sDica. It exhibits excellent dielectric properties and has a good adhesimi to siticmi such that silicon dioxide is ideal to be used as a dielectric or barrier layer. Silicon dioxide is also veiy useful in the MEMS and semiconductor industry due to its excellent material properties. A grown oxide layer is conformal oti the silicon... 

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