Preparation method of composite quartz sand

Abstract

The invention provides a preparation method of composite quartz sand, and belongs to the technical field of preparation processes of synthetic quartz sand. According to the method, natural quartz sand is subjected to crushing and acid treatment, bubbles and silicate impurities such as feldspar and mica in the natural quartz sand are effectively removed, further, the purified quartz sand is subjected to special surface modification, after coupling groups are generated on the surface of the quartz sand, the quartz sand and newly prepared silica sol are subjected to crystallization compounding according to a specific proportion, and the silica sol is obtained. The purity and the performance of the composite quartz sand are close to those of natural quartz sand, and the composite quartz sand can be used for preparing a high-performance quartz crucible.

Description

Technical Field

[0001] The invention relates to a method for preparing composite quartz sand, and belongs to the technical field of preparation technology of synthetic quartz sand. Background Art

[0002] With the rapid development of photovoltaic technology, the demand for single crystal silicon rods, as an important photovoltaic material, is also increasing year by year. Quartz crucibles, as key components for pulling single crystal silicon, have an important impact on the quality of single crystal silicon rods. In order to meet the purity requirements of single crystal silicon wafers, quartz crucibles generally need to be replaced with new quartz crucibles for the next crystal pulling after one to several crystal pulling operations. Therefore, they are highly consumables in the single crystal silicon industry chain.

[0003] The quartz crucible includes a vacuum transparent inner layer of sand and an opaque outer layer of sand. The outer layer of sand is also called a bubble composite layer, which is mainly used for heat preservation. The thickness of the inner layer of sand is 3-5 mm, which plays a decisive role in the life of the quartz crucible and the quality of single crystal silicon. In order to increase the number of reuses of the quartz crucible and ensure the performance of the single crystal silicon rod, high requirements are put forward for the purity, impurities, hydroxyl groups, gas-liquid inclusions, particle size, and consistency of the quartz sand used to prepare the inner layer of the crucible. Naturally formed high-purity quartz sand is an ideal raw material for preparing the inner layer of the crucible. However, my country's quartz mineral resources are relatively scarce. The feldspar, mica and bubbles contained in the particles cause the purity of the quartz sand to be low, and it cannot be used to produce high-quality quartz crucibles. In recent years, scientific researchers have been committed to synthesizing high-purity silicon dioxide through chemical methods, hoping to replace natural quartz sand. However, artificially synthesized silicon dioxide is often in an amorphous state, resulting in its hardness, softening point and other properties being lower than those of natural quartz sand, which in turn affects the quality of the quartz crucible. Improving the purity of natural quartz sand and improving the performance of synthetic quartz sand have become issues that need to be urgently addressed in this field. Summary of the invention

[0004] In order to improve the problems of poor compactness and low softening point of synthetic silicon dioxide, the present invention provides a method for synthesizing high-softening-point silicon oxide.

[0005] The technical solution of the present invention is a method for preparing composite quartz sand, which comprises the following steps: The natural quartz sand is crushed into 500 nm to 10 μm, added into an acid aqueous solution and stirred for 1 to 30 h, filtered, washed with water, and then the step a or the step b is performed to obtain modified quartz sand; The modified quartz sand and silica sol are mixed in a mass ratio of 1:0.1-0.2, stirred at 60-100°C for 10-30 min, and filtered. The stirring at 60-100°C for 10-30 min is repeated for 1-5 times, and then washed, vacuum dried, roasted, and crushed to obtain composite quartz sand of 40-120 meshes. The acid aqueous solution is selected from hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, and an organic acid aqueous solution having 1 to 5 carbon atoms; The step a: adding the washed quartz sand into solution A, stirring at 0.5-10 Mpa and 100-300 °C for 0.5-48 h; The solution A comprises at least one of sodium chloride, sodium hydroxide, and ammonia water and at least one of water and an organic alcohol having 1 to 3 carbon atoms; The step b: adding the washed quartz sand into a solution containing 1-5% of a silane coupling agent, and stirring at 50-100° C. for 0.5-24 h; The silane coupling agent is selected from vinyl triethoxy silane, vinyl trimethoxy silane, and vinyl tri (β-methoxyethoxy) silane.

[0006] In some specific preparation methods, the concentration of the aqueous acid solution is 2-6 mol / L; the concentration of the silica sol is 15-20%.

[0007] In some specific preparation methods, modified quartz sand and silica sol are mixed in a mass ratio of 1:0.1-0.15.

[0008] In some specific preparation methods, the calcination temperature is 500~1100°C and the calcination time is 5~15 h.

[0009] In some specific preparation methods, the vacuum drying conditions are: drying at 60~100°C and 0~-0.9 Mpa for 12~48h.

[0010] In some specific preparation methods, the silica sol is prepared by using C1-C4 alkyl orthosilicate or sodium silicate.

[0011] In some specific preparation methods, the silica sol is prepared by using methyl orthosilicate, ethyl orthosilicate or sodium silicate.

[0012] In some specific preparation methods, the acid aqueous solution is selected from hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, formic acid, acetic acid, propionic acid, methanesulfonic acid, and ethylsulfonic acid aqueous solutions.

[0013] In some specific preparation methods, the acid aqueous solution is selected from hydrofluoric acid, nitric acid, sulfuric acid, and hydrochloric acid aqueous solution.

[0014] The composite quartz sand prepared by the preparation method is used in preparing crucibles.

[0015] Beneficial effects of the present invention: The present invention provides a method for preparing composite quartz sand. The method effectively removes bubbles and silicate impurities such as feldspar and mica in natural quartz sand by crushing and acid-treating natural quartz sand. Furthermore, the purified quartz sand is subjected to special surface modification to generate coupling groups on its surface, which are then crystallized and composited with newly prepared silica sol in a specific ratio to obtain composite quartz sand with purity and performance close to those of natural quartz sand. The purity of the composite quartz can reach above 5N level and can be used to prepare high-performance quartz crucibles. DETAILED DESCRIPTION Example 1

[0016] Add 50 g of 2 mol / L hydrochloric acid to 20 kg of deionized water, then drop 5000 g of 99.999% pure tetramethoxysilane, react at room temperature for 6 h, and distill to remove the organic alcohol and 30% of the water produced by hydrolysis to obtain silica sol. Example 2

[0017] A 6% hydrochloric acid solution was added dropwise to a 20% water glass, the pH value of the system was maintained to be less than 2, and the silica sol was obtained by stirring at room temperature for 1 hour. Example 3

[0018] 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 2 mol / L hydrofluoric acid aqueous solution and stirred for 5 h, filtered, washed with water, added to 1 L of 2 mol / L sodium hydroxide solution, stirred at 5 Mpa, 150 °C for 10 h, filtered, washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.1, and then stirred at 80°C for 20 min. The stirring step at 80°C for 20 min was repeated twice, and then filtered, washed, dried at -0.5 Mpa, 75°C for 15 h, calcined at 800°C for 8 h, and crushed to 40-120 mesh to obtain composite quartz sand. Example 4

[0019] 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 2 mol / L hydrofluoric acid aqueous solution and stirred for 5 h, filtered, washed with water, added to 1 L of 25% ammonia aqueous solution, stirred at 5 Mpa, 200 °C for 10 h, filtered, washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.1, and then stirred at 80°C for 20 min. The stirring step at 80°C for 20 min was repeated twice, and then filtered, washed, dried at -0.5 Mpa, 75°C for 15 h, calcined at 800°C for 8 h, and crushed to 40-120 mesh to obtain composite quartz sand. Example 5

[0020] 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 2 mol / L hydrofluoric acid aqueous solution and stirred for 5 h, filtered and washed with water, then added to 1 L of 2 mol / L sodium hydroxide solution, stirred at 5 Mpa and 250 °C for 10 h, filtered and washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.1, and then stirred at 80°C for 20 min. The stirring step at 80°C for 20 min was repeated twice, and then filtered, washed, dried at -0.5 Mpa, 75°C for 15 h, calcined at 800°C for 8 h, and crushed to 40-120 mesh to obtain composite quartz sand. Example 6

[0021] 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 2 mol / L hydrofluoric acid aqueous solution and stirred for 5 h, filtered, washed with water, added to 1 L of water, and then 2% of the mass of quartz sand was added dropwise with vinyltriethoxysilane, stirred at 60 °C for 8 h, filtered, washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.1, and then stirred at 80°C for 20 min. The stirring step at 80°C for 200 min was repeated twice, and then filtered, washed, dried at -0.5 Mpa, 75°C for 15 h, calcined at 800°C for 8 h, and crushed to 40-120 mesh to obtain composite quartz sand. Example 7

[0022] 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 2 mol / L hydrochloric acid aqueous solution and stirred for 15 h, filtered, washed with water, added to 1 L of water, and then 3% of the mass of quartz sand was added dropwise with vinyltriethoxysilane, stirred at 80 °C for 8 h, filtered, washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.12, and then stirred at 100°C for 20 min. The stirring step at 100°C for 20 min was repeated three times, and then filtered, washed, dried at -0.5 Mpa, 80°C for 15 h, calcined at 1000°C for 5 h, and crushed to 40-120 mesh to obtain composite quartz sand. Example 8

[0023] 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 3 mol / L hydrofluoric acid aqueous solution and stirred for 15 h, filtered, washed with water, added to 1 L of water, and then 5% of the mass of quartz sand was added dropwise with vinyltriethoxysilane, stirred at 100 ° C for 1 h, filtered, and washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.15, and then stirred at 70°C for 25 min. The stirring step at 70°C for 25 min was repeated three times, and then filtered, washed, dried at -0.5 Mpa, 80°C for 15 h, calcined at 1000°C for 5 h, and crushed to 40-120 mesh to obtain composite quartz sand. Example 9

[0024] 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 5 mol / L hydrofluoric acid aqueous solution and stirred for 5 h, filtered, washed with water, added to 1 L of water, and then 3% of the mass of quartz sand was added dropwise with vinyltrimethoxysilane, stirred at 50°C for 15 h, filtered, washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.10, stirred at 60°C for 10 min, stirred at 80°C for 20 min, stirred at 100°C for 30 min, filtered, washed, dried at -0.5Mpa, 80°C for 15 h, calcined at 1000°C for 5 h, and crushed to 40-120 mesh to obtain composite quartz sand.

[0025] Comparative Example 1 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added to 1 L of 3 mol / L hydrofluoric acid aqueous solution and stirred for 15 h, filtered, washed with water, added to 1 L of water, and then 5% of the mass of quartz sand was added dropwise with vinyltriethoxysilane, stirred at 100 ° C for 1 h, filtered, and washed with water to obtain modified quartz sand; The obtained modified quartz sand was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.15, stirred at 70°C for 25 min, filtered, washed, dried at -0.5 Mpa, 80°C for 15 h, calcined at 1000°C for 5 h, and crushed to 40-120 mesh to obtain composite quartz sand.

[0026] Comparative Example 2 1 kg of natural quartz sand was crushed to 500 nm~10 μm, added into 1 L of 5 mol / L hydrofluoric acid aqueous solution and stirred for 5 h, filtered and washed with water to obtain modified quartz sand; The modified quartz sand obtained was mixed with the silica sol prepared in Example 1 at a dry basis mass ratio of 1:0.10, stirred at 60°C for 20 min, filtered, washed, dried at -0.5 MPa, 80°C for 15 h, calcined at 1000°C for 5 h, and crushed to 40-120 mesh to obtain composite quartz sand.

[0027] Comparative Example 3 Add 10 g of 2 mol / L hydrochloric acid to 4 kg of water, then add 1000 g of 99.999% pure tetramethoxysilane dropwise, react at room temperature for 6 h, distill to remove the alcohol and 30% of the water produced by hydrolysis, and age at 60 ° C for 24 h. The obtained gel is washed with water, dried at -0.5 Mpa, 80 ° C for 15 h, calcined at 1100 ° C for 5 h, and crushed to 40-120 mesh to obtain synthetic silica.

[0028] Test Case Quartz crucibles were prepared using the quartz sand obtained in Examples 3-9 and Comparative Examples 1-3, and the strength, amount of bubbles on the inner surface, and service life of the quartz crucibles were compared. The specific data are shown in Table 1.

[0029] Preparation process of quartz crucible: The quartz sand prepared in the embodiment and the comparative example is loaded into a rotary molding mold with a diameter of 2 cm, manually molded under the action of centrifugal force and a molding rod, the rotating device is moved to the electrode, the vacuum system is started, and the high temperature generated by the electric arc causes the quartz sand on the inner surface of the crucible to begin to melt and then expand to the outer surface, melting into molten quartz in the shape of a crucible, and then taken out after cooling. The outer surface is ground and molded to complete the preparation of the quartz crucible.

[0030] Table 1 Performance parameters of crucibles prepared using quartz sand from examples and comparative examples sample Number of bubbles at a depth of 1-2 mm on the inner surface Compressive strength / Mpa Continuous crystal pulling time / h Example 3 0 152 403 Example 4 0 155 408 Example 5 0 153 406 Example 6 0 154 408 Example 7 0 152 405 Example 8 0 155 410 Example 9 0 158 420 Comparative Example 1 0 160 450 Comparative Example 2 5 135 300 Comparative Example 3 10 125 250 It can be seen from the data in Table 1 that the quartz crucible prepared by using the composite quartz sand of the present invention is close to natural quartz sand.

Claims

1. A method for preparing composite quartz sand, characterized in that: Use the following steps: The natural quartz sand is crushed into 500 nm to 10 μm, added into an acid aqueous solution and stirred for 1 to 30 h, filtered, washed with water, and then the step a or the step b is performed to obtain modified quartz sand; The modified quartz sand and silica sol are mixed in a mass ratio of 1:0.1-0.2, stirred at 60-100°C for 10-30 min, and filtered. The stirring at 60-100°C for 10-30 min is repeated for 1-5 times, and then washed, vacuum dried, roasted, and crushed to obtain composite quartz sand of 40-120 meshes. The acid aqueous solution is selected from hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, and an organic acid aqueous solution having 1 to 5 carbon atoms; The step a: adding the washed quartz sand into solution A, stirring at 0.5-10 Mpa and 100-300 °C for 0.5-48 hours; The solution A comprises at least one of sodium chloride, sodium hydroxide, and ammonia water and at least one of water and an organic alcohol having 1 to 3 carbon atoms; The step b: adding the washed quartz sand into a solution containing 1-5% of a silane coupling agent, and stirring at 50-100° C. for 0.5-24 h; The silane coupling agent is selected from vinyl triethoxy silane, vinyl trimethoxy silane, and vinyl tri (β-methoxyethoxy) silane.

2. The method for preparing composite quartz sand according to claim 1, characterized in that: Repeat the stirring step at 60-100 °C for 10-30 min 2-5 times and then wash; The concentration of the acid aqueous solution is 2~6 mol / L; The concentration of silica sol is 15~20%.

3. The method for preparing composite quartz sand according to claim 1, characterized in that: Modified quartz sand and silica sol are mixed in a mass ratio of 1:0.1~0.

15.

4. The method for preparing composite quartz sand according to any one of claims 1 to 3, characterized in that: The calcination temperature is 500~1100 ℃, and the calcination time is 5~15 h.

5. The method for preparing composite quartz sand according to any one of claims 1 to 3, characterized in that: The vacuum drying conditions are: drying at 60~100 ℃, 0~-0.9 Mpa for 12~48 h.

6. The method for preparing composite quartz sand according to any one of claims 1 to 3, characterized in that: The silica sol is prepared by using C1-C4 alkyl orthosilicate or sodium silicate.

7. The method for preparing composite quartz sand according to claim 6, characterized in that: The silica sol is prepared by using methyl orthosilicate, ethyl orthosilicate or sodium silicate.

8. The method for preparing composite quartz sand according to any one of claims 1 to 3, characterized in that: The acid aqueous solution is selected from hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, formic acid, acetic acid, propionic acid, methanesulfonic acid, and ethylsulfonic acid aqueous solutions.

9. The method for preparing composite quartz sand according to claim 8, characterized in that: The acid aqueous solution is selected from hydrofluoric acid, nitric acid, sulfuric acid, and hydrochloric acid aqueous solutions.

10. Use of the composite quartz sand prepared according to the preparation method according to any one of claims 1 to 3 in preparing a crucible.