Through the above process and device to remove impurities in silicon

At present,the international general put the silicon goods into metal silicon and

semiconductor silicon. Silicon metal is made of quartz and coke in the electric

heating furnace smelted into products, principal component silicon content is

about 98% ( in recent years, also have content 99.99% Si of silicon metal ),

the remaining impurities is iron, aluminium, calcium. Semiconductor silicon

used in producing semiconductor device of high purity silicon metal. Is sell as

polycrystalline, single crystal morphology, the formal is cheap, the latter is expensive.

Due to its different use, it is divided into a variety of specifications.

According to statistics, in 1985 the world total consumption of silicon metal

is about 500000 tons, the silicon which is used for aluminum alloy metal is accounted

for about 60%, for the silicone is less than 30%, for semiconductor is accounted

for about 3%, others used for steel smelting and precision ceramic.

Metallic silicon can be used for preparing

super pure silica, through crushing the raw material, impurity compounds,

crystallization purification of three sequential steps of principle, adopts the

combination of various procedures operations: the metal silicon broken into

fine particles to increase the surface area; pass into the oxygen, chlorine,

hydrochloric acid in the silicon particles, conduct combination reaction in the

silicon impurity, in order to make the impurities in silicon generated into oxide

or chloride by high temperature; use high temperature to make low sublimation

temperature chloride evaporation removal, again using the individual element

segregation coefficient and oxide eutectic solidification characteristics, with

the intermediate technology or directional solidification technique further

removal the impurities in silicon. Through the above process and device to

remove impurities in silicon, make the silicon metal purified into ultra pure

silicon products.

In industry, metal silicon is usually prepared

by reduction of silica in an electric furnace carbon. The produced silicon

purity is 97~98%, called silicon metal. Then melt it and crystallization, use acid

to remove impurities, get the purity of 99.7~99.8% silicon metal. Silicon metal

component is silicon, thus having similar properties with silicon. Silicon has amorphous

silicon powder and amorphous silicon two allotropes. Amorphous silicon powder is dark gray powder,

is in fact a microcrystal. Crystalline silicon has the crystal structure of

diamond and semiconductor properties, the melting point is 1410,

boiling point is 2355,

the density is 2.32 to 2.34 g

/ cm 3, Mohs hardness is 7, brittle. Amorphous silicon powder with active

chemical properties, can burn in oxygen. It can react with halogen, nitrogen,

carbon and other non-metallic at high temperature, also can react with

magnesium and calcium, iron and other metals, form of silicide. Amorphous silicon

powder is virtually insoluble in all including hydrofluoric acid, inorganic

acid and organic acid, but soluble in nitric acid and hydrofluoric acid mixed

acid. Concentrated sodium hydroxide solution can dissolve the amorphous silicon

powder, release hydrogen. Crystalline silicon is less active, even at high

temperatures will not react with oxygen, it will not dissolve in any kind of

inorganic acid and organic acid, but soluble in nitric acid and hydrofluoric

acid mixed acid and concentrated sodium hydroxide solution.

Silicon metal smelting is a high

energy-consuming production, Chinese silicon metal production has

long-standing, along with the national energy policy tightening and energy

saving, and emission reduction and new energy development advocating, metal

silicon smelting has become the primary products and technology, many of Chinese

new energy industry construct metal silicon, polycrystalline silicon,

monocrystalline silicon, solar cell and other a series of cycle of industrial

chain, in the next few years will inevitably affect the development of the

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