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Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. As the eighth most common element in the universe by mass, silicon very rarely occurs as the pure free element in nature, but is more widely distributed in dusts, planetoids and planets as various forms of silicon dioxide (silica) or silicates. On Earth, silicon is the second most abundant element (after oxygen) in the crust, making up 25.7% of the crust by mass.

 

Silicon has many industrial uses. Elemental silicon is the principal component of most semiconductor devices, most importantly integrated circuits or microchips. Silicon is widely used in semiconductors because it remains a semiconductor at higher temperatures than the semiconductor germanium and because its native oxide is easily grown in a furnace and forms a better semiconductor/dielectric interface than any other material.

 

In the form of silica and silicates, silicon forms useful glasses, cements, and ceramics. It is also a constituent of silicones, a class-name for various synthetic plastic substances made of silicon, oxygen, carbon and hydrogen, often confused with silicon itself.

 

Silicon is commercially prepared by the reaction of high-purity silica with wood, charcoal, and coal, in an electric arc furnace using carbon electrodes. At temperatures over 1,900 °C (3,450 °F), the carbon reduces the silica to silicon according to the chemical equation

SiO2 + C → Si + CO2.

SiO2 + 2C → Si + 2CO.

 

Liquid silicon collects in the bottom of the furnace, and is then drained and cooled. The silicon produced via this process is called metallurgical grade silicon and is at least 98% pure. Using this method, silicon carbide, SiC, can form. However, provided the amount of SiO2 is kept high, silicon carbide may be eliminated, as explained by this equation:

2 SiC + SiO2 → 3 Si + 2 CO.

 

In September 2008, metallurgical grade silicon cost about $1.45 per pound ($3.20/kg), up from $0.77 per pound ($1.70/kg) in 2005.

 

It has been reported in recent years that, by molten salt electrolysis, pure silicon can be directly extracted from solid silica and this new electrolysis method, known as the FFC Cambridge Process, has the potential to produce directly the solar grade silicon without any CO2 emission at much lower energy consumption.

 

Usage

It is mainly used to produce organic-si in chemical industry and also regarding the non-ferroalloy’s additive and deoxidizer.