Silicon Metal grade
The grades of silicon metal are usually based on the content of iron, aluminum, calcium three main impurities contained in the silicon metal composition. According to the content of iron, aluminum, and calcium in silicon metal. The silicon metal grade can be divided into 553, 441, 411, 421, 3303, 3305, 2202, 2502, 1501, 1101, and other different grades.
Industrially, silicon metal is usually prepared by reducing silicon dioxide from carbon in an electric furnace. Chemical reaction equation: SiO2 + 2C → Si + 2CO so the purity of silicon is 97~98%, called silicon metal. Then it is melted and recrystallized, and the impurities are removed with acid to obtain the purity of 99.7~99.8% silicon metal.
Silicon metal is mainly silicon in composition and therefore has similar properties to silicon. Silicon has two allotropes: amorphous silicon and crystalline silicon. Amorphous silicon is a grayish-black powder that is actually a microcrystal. Crystalline silicon with diamond crystal structure and semiconductor properties, melting point 1410℃, boiling point 2355℃, Mohs hardness 7, brittle.
Amorphous silicification has active chemical properties and can burn violently in oxygen. It reacts with halogen, nitrogen, carbon and other nonmetals at high temperatures, and can also interact with magnesium, calcium, iron, and other metals to produce silicides.
Amorphous silicon is almost insoluble in all inorganic and organic acids, including hydrofluoric acid, but soluble in mixed acids of nitric and hydrofluoric acid. A concentrated solution of sodium hydroxide dissolves amorphous silicon and releases hydrogen. Crystalline silicon is less reactive and does not combine with oxygen even at high temperatures. It is also insoluble in any inorganic or organic acid, but soluble in a mixture of nitric and hydrofluoric acids and concentrated sodium hydroxide solutions.
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