The classification of silicon metal is usually classified by the content of the three main impurities of iron, aluminum and calcium contained in the silicon metal composition. According to the content of iron, aluminum and calcium in metal silicon, metal silicon can be divided into 553, 441, 411, 421, 3303, 3305, 2202, 2502, 1501, 1101 and other different grades.
In industry, metallic silicon is usually produced by carbon reduction of silicon dioxide in electric furnaces. Chemical reaction equation: SiO2 + 2C → Si + 2CO The purity of silicon produced in this way is 97~98%, which is called metallic silicon. Then it is melted and recrystallized, and impurities are removed with acid to obtain metallic silicon with a purity of 99.7~99.8%.
Silicon metal is mainly composed of silicon, so it has similar properties to silicon. Silicon has two allotropes: amorphous silicon and crystalline silicon. Amorphous silicon is a gray-black powder and is actually a microcrystal. Crystalline silicon has the crystal structure and semiconductor properties of diamond, melting point 1410℃, boiling point 2355℃, Mohs hardness 7, brittle. Amorphous silicification is active and can burn violently in oxygen. It reacts with non-metals such as halogens, nitrogen and carbon at high temperatures, and can also interact with metals such as magnesium, calcium and iron to generate silicides. Amorphous silicon is almost insoluble in all inorganic and organic acids, including hydrofluoric acid, but 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, even at high temperatures do not combine with oxygen, it is not soluble in any inorganic and organic acids, but soluble in nitric acid and hydrofluoric acid mixed acid and concentrated sodium hydroxide solution.
Post time: Nov-27-2024
