Silicon

Silicon

Silicon is an element (nonmetal) in the main subgroup of the fourth group, the third period. It has the fourteenth atomic number. It has its own symbol – Si (Silicium). It can be extracted from an old car if you decide to retire your car.

History

In the early eighteenth century, French chemist Joseph Louis Gay-Lussac and his colleague Louis Jacques Tenard obtained silicon in pure form. Later, Swedish scientist Jöns Jakob Berzelius also derived elemental silicon and named it “silicium” (silex means flint in Latin). In Russia, the official name of silicon was introduced by G.I. Gess in the 1830s, which translated from Ancient Greek (κρημνός) means “mountain, cliff”.

Obtaining

Free silicon is formed when white sand (SiO2) is heated over 400 °C with magnesium (Mg): [SiO]2 + 2Mg=2MgO + Si, where the silicon is a brown powder.

In the metallurgical industry, silicon is produced in the following way:

Silicon dioxide melt is reduced with coke at a temperature of about one thousand eight hundred degrees Celsius in ore-thermal shaft furnaces. The process results in a 99.9% purity of silicon (the main impurities are metal and carbon). Further refinements can be made to separate the impurities from the silicon.

The method used in the lab to purify silicon is as follows: first Mg2Si is produced, then gaseous SiH4 is produced from magnesium silicide by using acetic or hydrochloric acid. The resulting monosilane is purified, for example by sorption or distillation or other methods. The SiH4 is then decomposed into hydrogen and silicon at a temperature of about a thousand degrees Celsius.

In industry, silicon is purified through the process of chlorination. Through this, two constituent compounds, SiCl3, as well as SiCl4H, are produced. Such chlorides can purify impurities in a variety of ways. And the very last step is the reduction of pure hydrogen–the temperature must be about nine hundred or one thousand one hundred degrees Celsius.

Silicon purifiers are being developed that are more efficient, cleaner, and inexpensive. By 2010, silicon purification was done using fluorine (chlorine was changed to fluorine), technologies were developed that involved mono-oxide silicon distillation and technologies were invented that take as their basis the extraction of impurities that tend to concentrate on the boundaries between the grains (crystallites).

In the crude state the silicon impurities have a mass which is reduced by 10-8 – 10-6 %.

Silicon (technical) is produced in some Russian cities such as Kamensk-Uralsky and Shelekhov. At Usolie-Sibirsk plant Nitol Solar group produces refined silicon using (chloride) technology.

Application

Technical silicon is used:

1. In metallurgical production as:
– one of the components of bronze alloys, silumin;
– a deoxidizer in melting steel and cast iron;
– an alloying element, a modifier;
2. As a raw material for producing polysilicon (a material consisting of small crystallites of silicon).
3. In the manufacture of silanes as well as organosilicon materials.
4. In the field in the production of hydrogen.
5. In the manufacture of solar cells.
6. In plastics industry as an anti-block (additive).

Silicon is also used in production of passive elements of electric circuits as well as for production of monolithic microcircuits. In addition to pure silicon, the main components of solar cell production are silicon waste and crystalline silicon.

Monocrystalline silicon is used in production of electronics and gas laser mirrors.

Silicides (compounds of silicon with metals), are often used in the nuclear and electronics industries. They have many useful properties such as resistance to oxidation, neutrons, etc. For thermoelectrics, silicides of a number of elements are one of the most important materials.

Silicon compounds are the basis in the production of cement and glass. Their production, as well as the manufacture of ceramics and other things made of bricks, porcelain, etc., is done by the silicate industry.

Glue made from silica is very popular in the world, it is used as a “drying agent” in construction and in pyrotechnics to glue paper.

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