A method for preparing high-purity silicon dioxide particles

Abstract

The present invention relates to a method for preparing high-purity silica particles, belonging to the technical field of silica particle synthesis. The method uses high-purity organosilane as a raw material, and produces high-purity silica gel particles after hydrolysis, water crushing, and other treatment processes. The high-purity silica particles are then obtained by removing organic matter and dehydroxylation. This method has the characteristics of a simple process, a short reaction time, and no safety or environmental hazards, thus solving the problems of existing chemical synthesis of silica, which is complicated, has a long reaction time, and presents safety and environmental hazards. Furthermore, the method eliminates the need for acid or alkali during the silica particle preparation process, reducing damage to equipment. The gel particles produced by this method can achieve a purity of over 99.99995%, and have excellent application prospects.

Description

Technical Field

[0001] The invention relates to a method for preparing high-purity silicon dioxide particles, belonging to the technical field of silicon dioxide particle synthesis. Background Art

[0002] Quartz glass, due to its excellent high-temperature resistance, corrosion resistance, high insulation properties, high light transmittance, and strong mechanical properties, is widely used as a key base material in fields such as photovoltaic power sources, semiconductors, optical fibers, solar energy, aerospace technology, and military technology. The primary raw material for producing quartz glass is high-purity natural quartz sand, which contains silicon dioxide. Natural quartz sand is produced from natural quartz ore through processes such as crushing, water quenching, magnetic separation, electrostatic separation, flotation, pickling, calcination, and high-temperature chlorination. However, natural quartz contains a high concentration of metallic impurities, which cannot be completely removed even through various purification treatments, directly affecting the quality of the produced quartz glass. With the rapid development of semiconductors, the purity requirements for quartz glass, a base material, are becoming increasingly stringent. Consequently, chemically synthesizing high-purity silica particles and fusing them into quartz products is gaining increasing attention due to their low metallic impurity content and lack of bubbles. However, the current method of chemically synthesizing silica particles has the disadvantages of complicated process, long reaction time, and the need to use concentrated acid solution as a reactant, which poses safety and environmental risks. Therefore, it is necessary to improve it. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing high-purity silica particles with a simple process, short reaction time, and no safety and environmental risks, so as to solve the problems of the existing chemical synthesis of silica, which has a complicated process, long reaction time, and safety and environmental risks.

[0004] The technical solution of the present invention is:

[0005] A method for preparing high-purity silicon dioxide particles, characterized in that it comprises the following steps:

[0006] 1) Place the organic silicon raw material with purity > 99.99% and metal ion < 100ppb in an oil bath reactor, heat it to 40-60°C and maintain it, then stir it at 20-80 rpm.

[0007] 2) While stirring, inject the alcohol into the reactor at a flow rate of 100-250 ml / min to mix the two evenly, and stir for 0.5-2 hours to obtain Solution I;

[0008] 3) Pour up water into the reactor at a flow rate of 100-250 ml / min, continue stirring at a stirring speed of 20-80 rpm to fully mix it with solution I, stir for 0.5-2 hours to obtain solution II, stop stirring, and let it stand for 1-6 hours to obtain silica gel blocks;

[0009] 4) Heat the reactor to 110-180°C, introduce high-purity air into the reactor at a flow rate of 0.5-3L / min, and continue drying the gel blocks for 15-24 hours. When the moisture content of the gel blocks is less than 4%, the drying is complete. At this point, the gel blocks are evenly distributed with cracks formed by drying and dehydration.

[0010] 5) Inject up water into the reactor at a flow rate of 100-250 ml / min. The injection amount of up water is required to immerse the gel block by 0.5 cm, and the immersion time is 5-10 minutes, so that the up water enters the interior of the gel block along the cracks and structural gaps. The up water entering the gel block causes the gel block to break and decompose under the capillary action, forming gel particles of 200-1000 μm; at this time, the reactor is heated to 110-180 ° C again, and high-purity air is introduced into the reactor at a flow rate of 0.5-3 L / min. The gel particles are dried for 15-24 hours. After drying for 15-24 hours, the introduction of high-purity air (or nitrogen) is stopped to obtain dry gel particles of 200-1000 μm;

[0011] 6) Take out the dried gel and place it in an atmosphere electric furnace and heat it to 900-1200℃ for 8-20h to burn off all the organic matter and hydroxyl groups in the gel to obtain high-purity silica particles (quartz sand); the high-purity silica particles are sieved to 150-800μm and placed in a vacuum electric melting furnace. After electric melting at 1700℃, high-quality bubble-free quartz glass is obtained.

[0012] The volume ratio of organosilane to alcohol in the solution I in step 2) is 1:0.5-2, wherein the total content of metal ions in the organosilicon raw material is less than 100 ppb.

[0013] The volume ratio of the organosilane to the up-water in the solution II in step 3) is 1:1-5.

[0014] In step 5), the volume ratio of up water to solution II is 0.5-2:1.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention uses organic silane, alcohol and UP water as raw materials, and prepares high-purity silicon dioxide through the processes of mixing, water crushing, drying and calcining. The preparation process is simple, low-cost, low-waste liquid discharge, high efficiency and stable product quality. The prepared silicon dioxide not only has uniform particle size and total metal impurities below 0.5 ppm, but also is subsequently calcined at high temperature and does not contain gas-liquid inclusions, so that the fused quartz glass is free of bubbles, thereby significantly improving the quality of the quartz glass. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a bright field microscope image of the silica gel prepared by the present invention. Figure 1 It can be seen that the surface of the particles is clean without any fine powder and the particle size is evenly distributed.

[0018] Figure 2 The dark field microscope image of the silica gel prepared in the present invention shows that there are no defects such as inclusions and pores inside the particles.

[0019] Figure 3 This is the laser particle size picture of silica gel prepared by the present invention; Figure 3 It can be seen that the gel particles are uniform in size.

[0020] Figure 4 This is a transparent quartz glass picture made by calcining the gel prepared by the present invention and then electro-melting it; Figure 4 It can be seen that the quartz glass is transparent and there are no bubbles inside. DETAILED DESCRIPTION Example 1

[0021] 1 L of tetraethyl orthosilicate with a purity greater than 99.99% and a metal ion content less than 100 ppb was placed in a stainless steel oil bath reactor lined with polytetrafluoroethylene. The reactor was heated to 60°C and stirred at a stirring speed of 45 rpm. While stirring, 1 L of anhydrous ethanol was introduced into the reactor at a flow rate of 100 ml / min to uniformly mix it with the tetraethyl orthosilicate. Solution I was obtained after stirring for 2 h.

[0022] 5L of up water was injected into the reactor at a flow rate of 250ml / min and stirred at 80 rpm to ensure thorough mixing with Solution I. After stirring for 1 hour, stirring was stopped to obtain Solution II. Solution II was allowed to stand for 1 hour to obtain a silica gel block. At this point, the reactor was heated to 110°C and high-purity air was introduced into the reactor at a flow rate of 3L / min. The vent valve on the reactor was opened to allow high-purity air to flow. The gel block was dried continuously in the reactor for 24 hours. When the moisture content of the gel block was sampled and tested to be less than 4%, it indicated that drying was complete. At this point, the gel block was evenly distributed with a network of cracks formed by drying and dehydration.

[0023] After drying, the high-purity air flow was stopped and 3L of up-water (up-water) was introduced into the reactor at a flow rate of 250ml / min. The amount of up-water injected was required to submerge the gel blocks by 0.5cm. The immersion time was 10 minutes, allowing the up-water to enter the gel blocks along the cracks and structural gaps. The up-water inside the gel blocks caused the gel blocks to break and decompose under capillary action, forming gel particles. At this point, the reactor was heated to 110°C again and high-purity air was introduced into the reactor at a flow rate of 3L / min. After drying for another 24 hours, the high-purity air flow was stopped and the gel particles were cooled to obtain gel particles with a particle size of 200-700μm.

[0024] The dried gel particles are taken out and placed in an oxygen atmosphere electric furnace at 900°C and calcined for 20 hours to burn away all the organic matter and hydroxyl groups in the gel particles to obtain high-purity silica particles (quartz sand).

[0025] The high-purity silicon dioxide particles obtained in this example were analyzed for particle size, microscopy, and impurity content by ICP-MS. The results showed that the silicon dioxide had a particle size of 300-700 μm and no defects such as inclusions and pores inside. The ICP-MS test analysis results are as follows:

[0026]

[0027] Place the silicon dioxide particles in a vacuum electric melting furnace and then melt them to obtain bubble-free quartz glass. Specifically:

[0028] First, silica particles (quartz sand) are placed in a graphite crucible in the furnace. After loading, the vacuum degree in the vacuum melting furnace is evacuated to ≤20Pa. The temperature in the vacuum melting furnace is slowly increased from room temperature to 1200°C at a heating rate of 110°C / h. High-purity helium is then introduced into the vacuum melting furnace until the pressure reaches one atmosphere. The temperature in the vacuum melting furnace is maintained at 1200°C for 15 hours to fully remove the hydroxyl groups in the high-purity quartz sand. After 15 hours, the temperature in the vacuum melting furnace is increased from 1200°C to 1700°C at a rate of 60°C / h to melt the silica particles in the crucible to form a slurry. Heating is then stopped and the vacuum melting furnace is allowed to cool naturally to room temperature, allowing the silica slurry in the crucible to solidify into quartz glass. After demolding, a transparent, bubble-free quartz glass product is obtained. Example 2

[0029] 1 L of tetraethyl orthosilicate with a purity of >99.99% and a metal ion content of <100 ppb was placed in a stainless steel oil bath reactor with a polytetrafluoroethylene liner. The reactor was heated to 50°C and stirred at a stirring speed of 20 rpm. While stirring, 0.5 L of methanol was introduced into the reactor at a flow rate of 250 ml / min to uniformly mix it with the tetraethyl orthosilicate. Solution I was obtained after stirring for 0.5 h.

[0030] 1L of up water was injected into the reactor at a flow rate of 100ml / min and stirred at 20 rpm to ensure thorough mixing with Solution I. Stirring was stopped after 0.5h to obtain Solution II. Solution II was allowed to stand for 6h to obtain a silica gel block. The reactor was then heated to 180°C and high-purity nitrogen was introduced at a flow rate of 0.5L / min. The vent valve on the reactor was opened to allow the high-purity gas to flow. The gel block was dried continuously in the reactor for 15h. When the moisture content of the gel block was sampled and tested to be below 4%, drying was complete. At this point, the gel block was uniformly covered with a network of cracks formed by dehydration from drying.

[0031] After 15 hours of drying, the high-purity nitrogen was stopped and 6L of up water was passed into the reactor at a flow rate of 100ml / min. The injection amount of up water was required to immerse the gel block by 0.5cm, and the immersion time was 10min, so that the up water could enter the interior of the gel block along the cracks and structural gaps. The up water entering the interior of the gel block caused the gel block to break and decompose under the capillary action to form gel particles. At this time, the reactor was heated to 180°C again, and high-purity air was passed into the reactor at a flow rate of 2L / min to continue drying for 15 hours. The high-purity air was stopped and cooled to obtain gel particles with a particle size of 200-600μm. The high-purity air was passed into the reactor at a flow rate of 0.5L / min to continue drying for 15 hours. The high-purity nitrogen was stopped and cooled to obtain dry silica gel particles with a particle size of 200-600μm.

[0032] The dried silica gel particles are taken out and placed in an oxygen atmosphere electric furnace at 1200°C and calcined for 8 hours to burn off all organic matter and hydroxyl groups in the gel particles to obtain high-purity silica particles (quartz sand).

[0033] The silica particles obtained in this example were analyzed for particle size, microscopy, and impurity content by ICP-MS. The results showed that the silica particles had a particle size of 200-600 μm and no defects such as inclusions or pores. The ICP-MS test analysis results are as follows:

[0034]

[0035] Place the silicon dioxide particles in a vacuum electric melting furnace and then melt them to obtain bubble-free quartz glass. Specifically:

[0036] The silicon dioxide particles are placed in a graphite crucible in the furnace. After loading, the vacuum degree in the vacuum melting furnace is evacuated to ≤20Pa. The temperature in the vacuum melting furnace is slowly increased from room temperature to 1200℃ at a heating rate of 110℃ / h. High-purity helium is then introduced into the vacuum melting furnace until the pressure in the vacuum melting furnace reaches one atmosphere. At the same time, the temperature in the vacuum melting furnace is maintained at 1200℃ for 15 hours to fully remove the hydroxyl groups contained in the high-purity quartz sand. After 15 hours of constant temperature, the temperature in the vacuum melting furnace is increased from 1200℃ to 1700℃ at a rate of 60℃ / h to melt the silicon dioxide particles in the crucible to form a slurry. Heating is then stopped and the vacuum melting furnace is allowed to cool naturally to room temperature, allowing the silicon dioxide slurry in the crucible to solidify into quartz glass. After demolding, a bubble-free quartz glass product is obtained. Example 3

[0037] 1 L of butyl orthosilicate with a purity greater than 99.99% and a metal ion content less than 100 ppb was placed in a stainless steel oil bath reactor lined with polytetrafluoroethylene. The reactor was heated to 40°C and stirred at 80 rpm. While stirring, 2 L of anhydrous ethanol was introduced into the reactor at a flow rate of 100 ml / min to uniformly mix it with the butyl orthosilicate. Solution I was obtained after stirring for 1 h.

[0038] 2L of up water was injected into the reactor at a flow rate of 100ml / min and stirred at 80 rpm to thoroughly mix with Solution I. Stirring was stopped after 1 hour to obtain Solution II. Solution II was allowed to stand for 4 hours to obtain silica gel blocks. At this point, the reactor was heated to 140°C and high-purity nitrogen was introduced into the reactor at a flow rate of 2L / min. The vent valve on the reactor was opened to allow gas flow. The gel blocks were dried in the reactor for 24 hours.

[0039] After 24 hours, the high-purity nitrogen flow was stopped and 5L of up-water was introduced into the reactor at a flow rate of 250ml / min. The amount of up-water injected was required to immerse the gel blocks by 0.5cm, and the immersion time was 10 minutes. This allowed the up-water to enter the gel blocks along the cracks and structural gaps. The up-water inside the gel blocks caused the gel blocks to break up and decompose under capillary action, forming gel particles. At this time, high-purity air was introduced into the reactor at a flow rate of 2L / min to continue drying for 24 hours. The high-purity nitrogen flow was stopped and the gel particles were cooled to obtain dry gel particles with a particle size of 400-800μm.

[0040] The dried gel particles are taken out and placed in an oxygen atmosphere electric furnace at 1000°C and calcined for 16 hours to burn away all the organic matter and hydroxyl groups in the gel particles to obtain high-purity silica particles (quartz sand).

[0041] The silica particles obtained in this example were analyzed for particle size, microscopy, and ICP-MS impurity content. The results showed that the silica particles had a particle size of 400-800 μm, the gel was transparent, and there were no defects such as inclusions and pores inside. The ICP-MS test analysis results are as follows:

[0042]

[0043] The dried gel particles are placed in a vacuum electric melting furnace and then melted by vacuum electric melting to produce bubble-free quartz glass. The method for preparing bubble-free transparent quartz glass using dried gel particles is as follows:

[0044] First, place the crucible in the furnace. The crucible is made of graphite. After loading, the vacuum degree in the vacuum melting furnace is evacuated to ≤20Pa. The temperature in the vacuum melting furnace is slowly increased from room temperature to 1200℃ at a heating rate of 110℃ / h. High-purity helium is then filled into the vacuum melting furnace until the pressure in the vacuum melting furnace reaches one atmosphere. At the same time, the temperature in the vacuum melting furnace is maintained at 1200℃ for 15 hours to fully remove the hydroxyl groups contained in the high-purity quartz sand. After 15 hours of constant temperature, the temperature in the vacuum melting furnace is increased from 1200℃ to 1700℃ at a rate of 60℃ / h to melt the silica particles in the crucible to form slurry. Then, heating is stopped and the vacuum melting furnace is allowed to naturally cool to room temperature, allowing the silica slurry in the crucible to solidify into quartz glass. After demolding, a bubble-free transparent quartz glass product is obtained.

[0045] Comparative Example 1:

[0046] The preparation method of ultrapure spherical quartz sand comprises the following steps:

[0047] 1. Gradually add high-purity hydrochloric acid to ultrapure water to create an acidic solution with a pH of 1.5. Add 1.5g of the surfactant Tweens-80 to 500g of 99.5% pure ethyl silicate and stir thoroughly. Adjust the water bath temperature to 40°C.

[0048] 2. Pour the ethyl silicate prepared in step 1 into a glass and stir at 650 rpm. Pour 30 g of acid solution into the stirred ethyl silicate and continue stirring for 50 minutes to generate quartz sand precipitation.

[0049] 3. Rinse with ethanol twice and then with pure water four times to obtain transparent spherical quartz sand. Place the quartz sand in an oven, adjust the temperature to 70 degrees, and dry it for 20 hours. Then adjust the temperature to 150 degrees and dry it for 30 hours.

[0050] 4. The dried quartz sand is placed in a vacuum atmosphere electric furnace and continuously introduced with dry air. It is kept at 400 degrees for 10 hours, then evacuated to a vacuum degree of 5Pa, heated to 1050 degrees and kept warm for 20 hours. After natural cooling, high-purity spherical quartz sand is obtained.

[0051] The particle size of quartz sand is 250-400 microns, meeting the particle size requirements of high-end, high-purity quartz sand. The common impurity content analyzed by ICP-OES is shown in the table below.

[0052]

[0053] As shown in Comparative Example 1, the high-purity silica particles produced by the present invention require simple raw materials and do not require concentrated acid solutions as reactants, reducing safety risks. The particles are free of internal inclusions and have a higher purity, reaching over 99.99995%. Furthermore, the silica particles produced by the present invention can be subsequently electro-melted to produce bubble-free quartz products, offering high economic benefits.

Claims

1. A method for preparing high-purity silicon dioxide particles, characterized in that: It includes the following steps: 1) Place the organosilane raw material with a purity of more than 99.99% and a metal ion content of less than 100 ppb in an oil bath reactor, heat it to 40-60°C, and stir it at 20-80 rpm; 2) While stirring, inject the alcohol into the reactor at a flow rate of 100-250 ml / min to mix the two evenly, and stir for 0.5-2 hours to obtain Solution I; 3) Pour up water into the reactor at a flow rate of 100-250 ml / min, continue stirring at a stirring speed of 20-80 rpm to fully mix it with solution I, stir for 0.5-2 hours to obtain solution II, stop stirring, and let it stand for 1-6 hours to obtain silica gel blocks; 4) Raise the temperature of the reactor to 110-180°C, introduce high-purity air into the reactor at a flow rate of 0.5-3L / min, and continue drying the gel blocks for 15-24 hours. When the moisture content of the gel blocks is less than 4%, the drying is complete. At this point, the gel blocks are evenly distributed with network-like cracks formed by drying and dehydration. 5) Inject up water into the reactor at a flow rate of 100-250 ml / min. The injection amount of up water is required to immerse the gel block by 0.5 cm, and the immersion time is 5-10 minutes, so that the up water enters the interior of the gel block along the cracks and structural gaps. The up water entering the gel block causes the gel block to break and decompose under the capillary action, forming gel particles of 200-1000 μm; at this time, the reactor is heated to 110-180 ° C again, and high-purity air is introduced into the reactor at a flow rate of 0.5-3 L / min. The gel particles are dried for 15-24 hours. After drying for 15-24 hours, the introduction of high-purity air is stopped to obtain dry gel particles of 200-1000 μm; 6) Take out the dried gel and place it in an atmosphere electric furnace and heat it to 900-1200℃ for 8-20h to burn off all the organic matter and hydroxyl groups in the gel to obtain high-purity silica particles.

2. The method for preparing high-purity silicon dioxide particles according to claim 1, wherein: In step 2), the volume ratio of the organosilane raw material to the alcohol in solution I is 1:0.5-2, wherein the total content of metal ions in the organosilane raw material is less than 10 ppb.

3. The method for preparing high-purity silicon dioxide particles according to claim 1, wherein: The volume ratio of the organic silane raw material to the up water in the solution II in step 3) is 1:1-5.

4. The method for preparing high-purity silicon dioxide particles according to claim 1, wherein: In step 5), the volume ratio of up water to solution II is 0.5-2:1.

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