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The purity of silicon obtained in this way is 97~98%, which is called metal silicon. It is then melted and recrystallized, and impurities are removed with acid to obtain metallic silicon with a purity of 99.7~99.8%. The composition of metal silicon is mainly silicon, so it has similar properties to silicon. Silicon has two allotropes:amorphous silicon and crystalline silicon. Amorphous silicon is a gray-black powder that is actually a microcrystal. Crystalline silicon has the crystal structure and semiconductor properties of diamond, the melting point is 1410°C, the boiling point is 2355°C, the Moh's hardness hardness is 7, and it is brittle. Amorphous silicon is chemically active and can burn violently in oxygen. It reacts with non-metals such as halogen, nitrogen and carbon at high temperature, and can also interact with metals such as magnesium, calcium and iron to form silicides. Amorphous silicon is almost insoluble in all inorganic and organic acids including hydrofluoric acid, but is soluble in mixed acids of nitric acid and hydrofluoric acid. Concentrated sodium hydroxide solution can dissolve amorphous silicon and release hydrogen. Crystalline silicon is relatively inactive, it does not combine with oxygen even at high temperature, it is insoluble in any inorganic acid and organic acid, but it is soluble in mixed acids of nitric acid and hydrofluoric acid and concentrated sodium hydroxide solution. A large amount of silicon is used for smelting into ferrosilicon alloy as an alloying element in the iron and steel industry, and as a reducing agent in the smelting of many kinds of metals. Silicon is also a good component in aluminum alloys, and most cast aluminum alloys contain siliconProduct Dispaly
