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Method of purifying silicon metal by coating with aluminum film

A technology for purifying metals and metallic silicon, applied in non-metallic elements, chemical instruments and methods, silicon compounds, etc., can solve problems such as inability to remove metal impurities, and achieve the effect of cost reduction and simple process

Inactive Publication Date: 2012-01-04
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] It is generally believed that the segregation coefficient of most metal impurities in silicon is very small and can be removed by directional solidification. However, when the concentration of metal impurities is very high (greater than 1 ppmw, ppmw refers to one millionth by mass, that is, When there is 1 microgram of metal impurities per gram of silicon), the metal impurities cannot be removed by directional solidification

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] 1) Ultrasonic degreasing and cleaning of metal silicon with a particle size of 0.01 mm in acetone;

[0022] 2) Add the product of step 1) to the aluminum hydroxide colloid, stir well, and evaporate to dryness at 60°C, wherein the mass ratio of aluminum hydroxide to silicon is 2:1, and in the aluminum hydroxide colloid, aluminum hydroxide and water The mass ratio is 15:1;

[0023] 3) the product of step 2) is put into an annealing furnace, in a water gas atmosphere (volume ratio H 2 :CO=1:1) and heat to 800°C, hold for 2h; cool down to 650°C, hold for 1h; cool to room temperature with the furnace;

[0024] 4) The product of step 3) is taken out, soaked in a mixed solution of 5% hydrochloric acid and 1% hydrofluoric acid for 1 hour, and then cleaned with deionized water. High-grade metal silicon materials with a purity of 4N can be obtained. (The impurity content has been tested by ICPMS, see the table below for details, ppmw refers to one millionth by mass, that is, t...

Embodiment 2

[0027] 1) Ultrasonic degreasing and cleaning of metal silicon with a particle size of 0.1 mm in acetone;

[0028] 2) Add the product of step 1) into the aluminum hydroxide colloid, stir well, and evaporate to dryness at 100°C, wherein the mass ratio of aluminum hydroxide to silicon is 2:1, and in the aluminum hydroxide colloid, aluminum hydroxide and water The mass ratio is 10:1;

[0029] 3) the product of step 2) is put into an annealing furnace, in a water gas atmosphere (volume ratio H 2 :CO=1:1) heated to 900°C and kept for 4h; cooled to 700°C and kept for 2h; cooled to room temperature with the furnace;

[0030] 4) The product of step 3) is taken out, soaked in a mixed solution of 10% hydrochloric acid and 3% hydrofluoric acid for 3 hours, and then cleaned with deionized water. High-grade metal silicon materials with a purity of 4.5N can be obtained. (The content of impurities has been tested by ICPMS, see the table below for details)

[0031] impurity atoms ...

Embodiment 3

[0033] 1) Ultrasonic degreasing and cleaning of metal silicon with a particle size of 10 mm in acetone;

[0034] 2) Add the product of step 1) into the aluminum hydroxide colloid, stir well, and evaporate to dryness at 100°C, wherein the mass ratio of aluminum hydroxide to silicon is 2:1, and in the aluminum hydroxide colloid, aluminum hydroxide and water The mass ratio is 3:1;

[0035] 3) the product of step 2) is put into an annealing furnace, in a water gas atmosphere (volume ratio H 2 :CO=1:1) Heating to 1000°C, holding for 5 hours; cooling to 750°C, holding for 3 hours; cooling to room temperature with the furnace;

[0036] 4) The product of step 3) is taken out, soaked in a mixed solution of 20% hydrochloric acid and 10% hydrofluoric acid for 5 hours, and then cleaned with deionized water. High-grade metal silicon materials with a purity of 4N can be obtained. (The content of impurities has been tested by ICPMS, see the table below for details)

[0037] impu...

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PUM

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Abstract

The invention discloses a method of purifying silicon metal by coating with an aluminum film, which comprises the following steps of deoiling and washing the silicon metal; adding the silicon metal in aluminum hydroxide colloid for uniform mixing and drying; heating in the water gas atmosphere and heat insulating for twice and then cooling to the room temperature; and finally soaking the silicon metal in mixed solution of hydrochloric acid and hydrofluoric acid and cleaning with deionized water to obtain advanced silicon metal with the purity of 4-5N. The method utilizes the aluminum gettering for preliminary gettering treatment for the impurities in the silicon metal, the process is simple, the cost is greatly reduced, and the relatively pure silicon material can be obtained as the silicon material of a solar battery or further purified raw material can be obtained.

Description

technical field [0001] The invention relates to a method for purifying metallic silicon, in particular to a method for purifying metallic silicon by covering it with an aluminum film. Background technique [0002] Solar energy is widely distributed and is an inexhaustible clean energy. Solar cells can convert solar energy into electrical energy, but the current price of solar cells is relatively high, especially the cost of crystalline silicon cells, which is the main body of the photovoltaic market, is still very high, which seriously affects the promotion and use of solar energy. [0003] The photovoltaic market is currently dominated by crystalline silicon solar cells. In recent years, the cost of silicon material accounts for more than 25% of the total cost, which has become a bottleneck restricting the further development of solar cells. Among the high-purity polysilicon purification technologies, the improved Siemens method and the silane method account for more than...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B33/037
Inventor 余学功顾鑫杨德仁
Owner ZHEJIANG UNIV