Method for preparing low-defect amorphous silicon dioxide

Abstract

The invention provides a method for preparing low-defect amorphous silicon dioxide, which comprises the following steps: S1, dropwise adding silicon tetrachloride into ethanol at 20-35 DEG C, and carrying out pre-hydrolysis reaction to obtain a reaction solution 1; s2, the reaction liquid 1 is dropwise added into a mixed solvent of ethyl alcohol and water, hydrolysis polycondensation reaction is further carried out, sol is obtained, and the volume ratio of ethyl alcohol to water in the mixed solvent of ethyl alcohol and water is 4: 1-16; s3, the sol obtained in the step S2 is subjected to aging or vacuum concentration treatment, and wet gel is obtained; and S4, drying, calcining and crushing the wet gel to obtain the low-defect amorphous silicon dioxide. The problems of violent reaction, non-uniform microstructure and defect residue in the traditional direct hydrolysis process of silicon tetrachloride are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of preparation of silicon dioxide, and particularly relates to a method for preparing low-defect amorphous silicon dioxide. BACKGROUND

[0002] High-purity quartz sand plays an indispensable role in the fields of cutting-edge technologies such as semiconductors, photovoltaics, optical communications, and military industries due to its excellent physical and chemical properties. The growth process of silicon single crystals has extremely stringent requirements for the quality of quartz crucibles, which are composed of an inner layer, a middle layer, and an outer layer. The inner layer has the most stringent requirements for the purity of quartz sand, which must be above 99.999%. In addition, it must have low hydroxyl content and anti-crystallization properties. Crucibles made of high-quality high-purity quartz sand have almost no bubbles on their inner surfaces before being put into use, and the breaking of bubbles on the inner surface during use is also extremely rare, which provides a solid guarantee for long-time crystal pulling operations (such as multiple recharging) and effectively avoids the introduction of impurities.

[0003] High-purity quartz sand can be divided into high-purity natural quartz sand and high-purity synthetic quartz sand. High-purity natural quartz sand is mainly obtained by further impurity removal and purification of natural quartz ore, but high-quality quartz ore is very scarce. Therefore, it is necessary to develop high-purity synthetic quartz sand that does not rely on quartz ore resources.

[0004] In the field of synthetic quartz sand, the current preparation processes of silicon dioxide can be divided into gas phase method, chemical precipitation method, sol-gel method, and biological method, etc., which show significant differences in purity, cost, environmental friendliness, etc.

[0005] Among them, the gas phase method (such as gas phase hydrolysis and oxidation method) synthesizes nanoscale high-purity silicon dioxide through high-temperature reaction, and the product has good dispersibility and excellent performance, but it relies on expensive equipment and has problems of high energy consumption and tail gas pollution, so it is suitable for high-value-added fields such as electronics and optics.

[0006] The chemical precipitation method uses cheap water glass as raw material and obtains nanoscale silicon dioxide by adding acid / alkali neutralization. Although the process is simple, the product is prone to agglomeration and contains impurities, and the wastewater treatment cost is high. Therefore, it is necessary to optimize the process to improve the purity. The silicon dioxide powder is mainly used for rubber fillers and toothpaste additives.

[0007] The sol-gel method prepares high-purity porous materials by hydrolysis-condensation reaction of silane compounds, and the pore size can be adjusted and suitable for low-temperature film formation. However, the preparation period is long and the cost is high, so it is mainly used for catalyst carriers or functional material development.

[0008] The biological method uses biomass such as rice husk to extract silicon dioxide, and the raw material is renewable and low-carbon and environmentally friendly. However, the purity is low and the process stability is insufficient, so it is mainly used for soil conditioners or environmentally friendly materials, and breakthroughs in purification technology are needed to broaden its application.

[0009] In addition, the traditional silicon tetrachloride hydrolysis can also prepare silicon dioxide, but this method has problems of violent reaction, difficult control of heat release, serious agglomeration of reaction products, and poor reaction filtration, resulting in low yield. Although there are methods for adjusting the pH of the reaction system by adding acid / base to improve the filtration of the reaction products, or adding different surfactants to improve the dispersion of the system to control the particle size of the products, etc., such methods introduce metal impurities or high molecular compounds, which are difficult to remove subsequently and cannot meet the purity requirements of semiconductor quartz products. For example, the patent application with publication number CN102515104A discloses a method for preparing hydrogen chloride and silicon dioxide by hydrolysis of silicon tetrachloride in an organic solvent. Water is added to a mixed solution prepared from silicon tetrachloride, an organic solvent, and a surfactant to generate hydrogen chloride gas and silicon dioxide by hydrolysis reaction. The generated hydrogen chloride gas is recovered after drying, and the silicon dioxide is sold as a product after alcohol washing and drying. SUMMARY

[0010] To solve the above technical problems in the prior art, the present application provides a method for preparing low-defect amorphous silicon dioxide, which solves the problems of violent reaction, uneven microstructure, and defect residues in the traditional direct hydrolysis process of silicon tetrachloride.

[0011] The present application provides a method for preparing low-defect amorphous silicon dioxide, comprising the following steps:

[0012] S1: Silicon tetrachloride is added dropwise to ethanol at 20-35℃ to generate a pre-hydrolysis reaction, obtaining reaction liquid 1;

[0013] S2: Reaction liquid 1 is added dropwise into a mixed solvent of ethanol and water to further generate a hydrolysis polycondensation reaction, obtaining a sol, wherein the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 4:1-16;

[0014] S3: The sol obtained in step S2 is aged or treated by reduced pressure concentration to obtain a wet gel;

[0015] S4: The wet gel is dried, calcined, and crushed to obtain the low-defect amorphous silicon dioxide.

[0016] In step S1, the volatilization of silicon tetrachloride is obvious at about 40℃, so the reaction temperature should not be too high.

[0017] Preferably, in step S1, the volume ratio of silicon tetrachloride to ethanol is 6:10-50.

[0018] Further preferably, in step S1, the volume ratio of silicon tetrachloride to ethanol is 6:10-20.

[0019] Preferably, in step S1, the purity of the silicon tetrachloride is not less than 99.9999%, and the purity of the ethanol is not less than 99.99%, so that the impurities in the raw materials are significantly reduced, the influence of the impurities on the hydrolysis reaction of the silicon tetrachloride is reduced, and the purity of the generated silicon dioxide is higher and the defects are fewer.

[0020] Preferably, in step S1, the dropping speed of the silicon tetrachloride into the ethanol is 20-40 mL / h, and is further preferably 20 mL / h. The slow dropping speed slows down the reaction rate and inhibits the local intense exothermic behavior, so that a uniform and stable transparent sol system is formed.

[0021] Preferably, in step S2, the volume ratio of the ethanol to the water in the mixed solvent of the ethanol and the water is 4:1-4. The small amount of water in the mixed solvent controls the gradual hydrolysis of the silicon tetrachloride, slows down the reaction rate of the generated silicon dioxide, and inhibits the local intense exothermic behavior, so that a uniform and stable transparent sol system is formed.

[0022] Preferably, in step S2, the volume ratio of the reaction liquid 1 to the mixed solvent of the ethanol and the water is 0.65-1.6:1.

[0023] Preferably, in step S1, the pre-hydrolysis reaction time is 3-10 h; and in step S2, the hydrolysis and polycondensation reaction time is 3-10 h.

[0024] Preferably, in step S3, the aging or vacuum concentration treatment time is 2-20 h.

[0025] Preferably, in step S4, the drying is air drying, and the temperature of the air drying is 80-110 ℃.

[0026] Preferably, in step S4, the calcination is staged calcination. First, the air calcination is performed at 400-500 ℃ for 2-8 h to remove the organic solvent ethanol and carbon residues, the carbon residues are ethyl and free carbon; then, the vacuum calcination is performed at 700-900 ℃ for 2-5 h to eliminate the silicon hydroxyl (Si-OH) on the surface or in the interior of the SiO2 to avoid introducing structural defects; finally, the vacuum calcination is further performed at 900-1200 ℃ for 2-20 h to complete the densification sintering to eliminate the pores in the silicon dioxide and improve the density.

[0027] Further preferably, in step S4, the calcination is staged calcination. First, the air calcination is performed at 400-500 ℃ for 2-8 h, then the vacuum calcination is performed at 700-900 ℃ for 2-5 h, and finally the vacuum calcination is further performed at 900-1200 ℃ for 2-20 h to complete the densification sintering.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) Process controllability is improved: by using ethanol as an intermediate medium for stage hydrolysis (from silicon tetrachloride to ethyl silicate to silicon dioxide), the reaction rate is significantly reduced, avoiding the heterogeneous nucleation of sol and pore defects caused by the sudden rise of micro-zone temperature, and the polarity gradient of mixed solvents promotes the directional polycondensation of silicate, forming a three-dimensional network structure with uniform pore size distribution. This control strategy enables the sol to complete gelation in a short time and obtain a transparent wet gel with uniform structure.

[0030] (2) Excellent product performance: The true density of the obtained silicon dioxide particles is ≥2.20 g / cm 3 , the surface is free of microcracks, and the internal bubble volume fraction is <0.05%, meeting the anti-bubble expansion requirements of semiconductor quartz devices in high-temperature and vacuum environments.

[0031] (3) Economic and environmental advantages: Directly using polysilicon by-product silicon tetrachloride as raw material, realizing high-value utilization of waste; without introducing metal catalysts or complex additives, avoiding secondary pollution; not only the process efficiency is improved compared with the traditional sol-gel method, but also the production cost is significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a real picture of low-defect amorphous silicon dioxide prepared in Example 1, wherein the left picture is a block sample before crushing and grinding, and the right picture is a particle sample after crushing and grinding.

[0033] Figure 2 is an optical microscope photograph of Examples 1-3.

[0034] Figure 3 is a scanning electron microscope comparison picture of silicon dioxide before and after sintering in Example 2, wherein, Figure 3 a is the scanning electron microscope picture of silicon dioxide before sintering, Figure 3 b is the scanning electron microscope picture of silicon dioxide after sintering.

[0035] Figure 4 is an X-ray diffraction test spectrum of Examples 1-3.

[0036] Figure 5 is a real picture of silicon dioxide prepared in Comparative Example 1, wherein the left picture is a block sample before crushing and grinding, and the right picture is a particle sample after crushing and grinding.

[0037] Figure 6 is an optical microscope photograph of Comparative Examples 1-3.

[0038] Figure 7 is a scanning electron microscope comparison picture of silicon dioxide before and after sintering in Comparative Example 1, wherein, Figure 7a is a scanning electron microscope picture of the silicon dioxide before sintering, Figure 7 b is a scanning electron microscope picture of the silicon dioxide after sintering. DETAILED DESCRIPTION

[0039] Example 1

[0040] Step 1: 500 mL of ethanol (purity 99.99%, same below) was placed in a constant temperature stirring reaction kettle, and the temperature was controlled at 20°C. 300 mL of high-purity silicon tetrachloride (purity of silicon tetrachloride 99.9999%, same below) was slowly added at a dropping speed of 20 mL / h, and the volume ratio of silicon tetrachloride to ethanol was 6:10. The silicon tetrachloride continued to hydrolyze in ethanol for 3 hours to form a reaction liquid S1, and the system temperature fluctuated within ±2°C.

[0041] Step 2: A mixed solvent of ethanol and ultrapure water 500 mL (volume ratio of ethanol to ultrapure water 4:1) was prepared, and the reaction liquid S1 was added dropwise into the mixed solvent, and stirred at room temperature for 3 hours to form a uniform colorless transparent sol.

[0042] Step 3: The sol was treated by reduced pressure concentration (pressure 0.08 MPa) for 20 hours to obtain a transparent wet gel with uniform structure.

[0043] Step 4: The wet gel was air-dried at 80°C for 10 hours to obtain a high-purity silicon dioxide bulk.

[0044] Step 5: First, under air condition, the temperature was raised to 400°C at a heating rate of 4°C / min, and the temperature was kept for 2 hours to remove organic matter and carbon residues; then under a vacuum environment of -0.1 MPa, the temperature was raised to 700°C at a heating rate of 2°C / min, and the temperature was kept for 2 hours to perform high-temperature dehydroxy treatment; finally, on the basis of the dehydroxy temperature, the temperature was raised to 900°C at a heating rate of 1.5°C / min, and the temperature was kept for 10 hours to complete the densification sintering.

[0045] Step 6: The sintered silicon dioxide bulk was crushed and ground to obtain dense silicon dioxide particles with a particle size of 50-300 μm, as shown in Figure 1 .

[0046] Example 2

[0047] Step 1: 60 mL of silicon tetrachloride was added dropwise to 200 mL of ethanol stirred at a constant speed at a temperature of 30°C, the volume ratio of silicon tetrachloride to ethanol was 6:20, and the hydrolysis reaction time was 5 hours to form a reaction liquid S1.

[0048] Step 2: A mixed solvent was prepared by mixing 200 mL of ethanol and 200 mL of ultrapure water in a volume ratio of 1:1, and the reaction solution S1 was added dropwise into the mixed solvent. After mixing, the reaction was carried out at room temperature for 5 hours to form a uniform colorless transparent sol.

[0049] Step 3: The sol was concentrated under reduced pressure at 25°C for 2 hours to obtain a transparent wet gel with uniform structure.

[0050] Step 4: The wet gel was gradient air-dried at 100°C for 10 hours to obtain a high-purity silica bulk.

[0051] Step 5: First, heat to 500°C at a heating rate of 5°C / min under air conditions, and keep the temperature for 5 hours to remove organic matter and carbon residues; then heat to 800°C at a heating rate of 3°C / min under vacuum environment, and keep the temperature for 5 hours for high-temperature dehydroxy treatment; finally, heat to 1000°C at a heating rate of 2°C / min based on the dehydroxy temperature, and keep the temperature for 2 hours to complete the densification sintering.

[0052] Step 6: The sintered silica bulk was crushed and ground to obtain dense silica particles with a particle size of 40-500 μm.

[0053] Example 3

[0054] Step 1: Under the condition of temperature control at 35°C, 60 mL of silicon tetrachloride was added dropwise into 300 mL of ethanol stirred at a constant speed at a rate of 30 mL / h, and the volume ratio of silicon tetrachloride to ethanol was 6:30. The hydrolysis reaction time was 10 hours to form a reaction solution S1.

[0055] Step 2: A mixed solvent was prepared by mixing 100 mL of ethanol and 200 mL of ultrapure water in a volume ratio of 1:2, and the reaction solution S1 was added dropwise into the mixed solvent. After mixing, the reaction was carried out at room temperature for 10 hours to form a uniform colorless transparent sol.

[0056] Step 3: The sol was aged at 30°C for 20 hours to obtain a transparent wet gel with uniform structure.

[0057] Step 4: The wet gel was gradient air-dried at 110°C for 8 hours to obtain a high-purity silica bulk.

[0058] Step 5: First, heat to 500°C at a heating rate of 3°C / min under air conditions, and keep the temperature for 8 hours to remove organic matter and carbon residues; then heat to 900°C at a heating rate of 2.5°C / min under vacuum environment, and keep the temperature for 2 hours for high-temperature dehydroxy treatment; finally, heat to 1200°C at a heating rate of 1°C / min based on the dehydroxy temperature, and keep the temperature for 20 hours to complete the densification sintering.

[0059] Step 6: The sintered silica block was crushed and ground to obtain dense silica particles with a particle size of 50-200 μm.

[0060] Example 4

[0061] The difference between this example and Example 2 is that in Step 1, the volume ratio of silicon tetrachloride to ethanol is 6:40, the volume of silicon tetrachloride and ethanol is 60 mL and 400 mL respectively, and the dropping speed of silicon tetrachloride is 40 mL / h.

[0062] Example 5

[0063] The difference between this example and Example 3 is that in Step 1, the volume ratio of silicon tetrachloride to ethanol is 6:50, the volume of silicon tetrachloride and ethanol is 60 mL and 500 mL respectively, and the dropping speed of silicon tetrachloride is 40 mL / h; in Step 2, the mixed solvent is prepared by mixing ethanol and ultrapure water at a volume ratio of 1:4, and the volume of ethanol and ultrapure water is 100 mL and 400 mL respectively.

[0064] Comparative Example 1

[0065] Step 1: 60 mL of silicon tetrachloride was added dropwise into 200 mL of ethanol stirred at a constant speed at a temperature of 30°C at a speed of 30 mL / h, the volume ratio of silicon tetrachloride to ethanol was 6:20, and the hydrolysis reaction time was 3 hours to form a reaction solution S1.

[0066] Step 2: The mixed solvent was prepared by mixing ethanol and ultrapure water at a volume ratio of 1:1 (the volume of ethanol and ultrapure water was 200 mL), and the mixed solvent was added dropwise into the reaction solution S1, contrary to Example 2. At this time, the reaction rate increased significantly, the local reaction exothermed violently, and the wet gel was formed after the addition of the mixed solvent was completed. The gel was milky white due to the structure collapse caused by the rapid reaction.

[0067] Step 3: The wet gel was dried at 110°C by gradient air blowing for 10 hours to obtain a high-purity silica block.

[0068] Step 4: First, the temperature was increased to 500°C at a rate of 5°C / min under air, and the organic matter and carbon residue were removed by keeping the temperature for 5 hours; then, the temperature was increased to 700°C at a rate of 3°C / min under vacuum, and the hydroxyl group was removed by keeping the temperature for 6 hours; finally, the temperature was increased to 1000°C at a rate of 2°C / min based on the dehydroxylation temperature, and the sintering was completed by keeping the temperature for 10 hours.

[0069] Step 6: The sintered silica block was crushed and ground, and finally silica particles with a particle size of 50-450 μm were obtained. The silica particles appeared as a relatively loose sample of milky white particles. Figure 5 .

[0070] Comparative Example 2

[0071] Step 1: At a temperature of 30°C, 60 mL of silicon tetrachloride was added dropwise to 300 mL of ethanol at a speed of 20 mL / h, the volume ratio of silicon tetrachloride to ethanol was 6:30, and the hydrolysis reaction time was 5 hours to form a reaction solution S1.

[0072] Step 2: 600 mL of ultrapure water with a volume ratio of 1:10 to silicon tetrachloride was directly added to the reaction solution S1 without additional ethanol. Due to the lack of catalysis of ethanol, the hydrolysis process was slow, and because the reaction solution S1 contained silicon tetrachloride raw materials, the reaction rate with water was faster than that of ethyl silicate with water. The different reaction rates resulted in the formation of a sol containing flocculation in the reaction solution.

[0073] Step 3: The sol was aged at 25°C for 5 hours to obtain a milky white wet gel.

[0074] Step 4: The wet gel was dried by gradient air flow at 100°C for 8 hours to obtain a high-purity silica block.

[0075] Step 5: First, heat to 700°C at a heating rate of 3°C / min under air conditions, and hold for 3 hours to remove organic matter and carbon residues; then heat to 900°C at a heating rate of 2.5°C / min in a vacuum environment, and hold for 5 hours for high-temperature dehydroxy treatment; finally, heat to 1200°C at a heating rate of 1°C / min based on the dehydroxy temperature, and hold for 20 hours to complete sintering, obtaining silica particles with a particle size of 50-450 μm, which appeared as a relatively loose sample of milky white particles.

[0076] Step 6: The sintered silica block was crushed and ground, and finally silica particles with a particle size of 50-450 μm were obtained. The silica particles appeared as a relatively loose sample of milky white particles.

[0077] Comparative Example 3

[0078] Step 1: At 25°C, 60 mL of silicon tetrachloride was added dropwise to a mixture of 30 mL of ethanol and 90 mL of ultrapure water at a speed of 30 mL / h, the volume ratio of silicon tetrachloride to ethanol and water was 6:30:90, and a translucent sol was obtained after 3 hours of hydrolysis reaction.

[0079] Step 2: The sol was concentrated under reduced pressure at 25℃ for 2 hours to obtain a wet gel with milky white color.

[0080] Step 3: The wet gel was dried by gradient air flow at 100℃ for 8 hours to obtain a high-purity silica bulk.

[0081] Step 4: Firstly, the temperature was raised to 700℃ at a rate of 3℃ / min under air condition for 3 hours to remove organic matter and carbon residues; then, the temperature was raised to 900℃ at a rate of 2.5℃ / min under vacuum condition for 5 hours for high-temperature dehydroxy treatment; finally, the temperature was raised to 1200℃ at a rate of 1℃ / min based on the dehydroxy temperature for 20 hours for sintering, to obtain silica particles with a particle size of 50-450μm, which appeared as a loose white powder sample.

[0082] Step 5: The silica bulk obtained by sintering was crushed and ground, to obtain silica particles with a particle size of 50-450μm, which appeared as a loose milky white particle sample.

[0083] Comparative Example 4

[0084] At 25℃, 60mL of silicon tetrachloride was added dropwise into a mixture solution of 90mL of ethanol and 30mL of ultrapure water at a rate of 30mL / h, and the volume ratio of silicon tetrachloride to ethanol and water was 6:90:30. Due to the high content of ethanol and the low boiling point of ethanol and silicon tetrachloride, the exothermic reaction of silicon tetrachloride and water resulted in a large amount of silicon tetrachloride volatilization with ethanol. After 3 hours of hydrolysis reaction, only a small amount of white precipitate was obtained, and the remaining liquid could not be gelled for a long time, which proved that a large amount of raw material was lost, and the reaction could not continue.

[0085] Comparative Example 5

[0086] Step 1: At 40℃, 60mL of silicon tetrachloride was added dropwise into 200mL of ethanol at a rate of 20mL / h, and the hydrolysis reaction time was 5 hours to form a reaction liquid S1.

[0087] Step 2: The reaction liquid S1 was added dropwise into a mixed solvent prepared by mixing 200mL of ethanol and 200mL of ultrapure water at a volume ratio of 1:1. Due to the high reaction temperature and the exothermic reaction, a large amount of silicon tetrachloride volatilized, and the remaining liquid could not be gelled for a long time, which proved that a large amount of raw material was lost, and the reaction could not continue.

[0088] Detection Example

[0089] 1. Verification of Dense Structure

[0090] From the light microscope test results (see Figure 2 ), it can be seen that the silica particles prepared in Examples 1-3 have no bubbles (internal bubble volume ratio < 0.05%) and pores on the surface and inside, indicating good densification.

[0091] The silica samples obtained in Example 2 before and after sintering were respectively taken by scanning electron microscope (SEM), and the results are shown in Figure 3 It can be seen that the microstructure of the precursor presents a porous structure, and the surface of the sintered silica is smooth and flat, and the pores are basically eliminated, indicating that the sintering process effectively eliminates the porous structure of the precursor.

[0092] It is worth noting that the silica prepared by traditional synthesis usually presents a sponge-like porous structure, and the densification of Example 2 is significantly better than such conventional materials, further proving the effectiveness of the sintering process. The light microscope test of the silica particles prepared in Comparative Examples 1-3 shows (see Figure 6 ) that the surface of the particles is rough, and there are obvious bubbles inside; the SEM picture of the sintered silica in Comparative Example 1 also shows that there are obvious pores on the surface of the particles (see Figure 7 ). These results show that the ethanol-mediated mild hydrolysis strategy and the segmented calcination technique are very effective for successfully preparing silica particles with high densification and low defects.

[0093] 2. Structure transformation mechanism of sintering process

[0094] As shown in Figure 3 , the silica precursor before sintering is in a loose and porous state, and the surface of the particles is densified after sintering, indicating that particle fusion and pore closure occur in the sintering process. Unlike the negative result of the collapse of the pore structure caused by improper treatment, Example 2 realizes the ordered elimination of pores rather than structural destruction by precisely controlling the sintering parameters, which reflects the superiority of the process.

[0095] 3. Confirmation of amorphous structure and breakthrough of high true density

[0096] The silica prepared in Examples 1-3 was subjected to X-ray diffraction (XRD) test, and the results are shown in Figure 4 , confirming that the silica obtained in Examples 1-3 is amorphous silica, and the diffraction pattern is consistent with the "hill" curve mode of amorphous silica.

[0097] At the same time, the true density of the silica before and after sintering in Examples 1-5 was tested and analyzed, and the results are shown in Table 1.

[0098] Table 1

[0099]

[0100] The results show that the true density is as high as 2.279 g / cm 3 , far exceeding the low-density characteristics (usually less than 2.1 g / cm 3 ) of traditional porous silica. This high density directly reflects the extremely low proportion of internal pores, which is consistent with the densification observation results of light microscopy / SEM.

[0101] The present application provides a controllable process path for large-scale preparation of high-performance silica materials, and realizes a controllable transformation from a porous precursor to a high-density particle through a sintering process, overcoming the defects of structural collapse or residual pores in traditional methods. The high true density indicates that the material has better mechanical strength and chemical stability, the retention of amorphous structure makes it more competitive in applications requiring amorphous characteristics such as optics and catalysis, and the absence of bubbles and pores makes it more suitable for manufacturing quartz glass auxiliary materials for the semiconductor industry. Bubble generation or expansion phenomenon is inhibited when used in high-temperature and reduced-pressure environments, effectively meeting the needs of the semiconductor, optoelectronic, photovoltaic and other industries.

[0102] In summary, Examples 1-5 have made significant breakthroughs in densification, structure control and performance indicators through process innovation, providing an efficient and reliable technical solution for the preparation of low-defect, amorphous silica materials.

Claims

1. A method of making low-defect, amorphous silicon dioxide, characterized by, The method comprises the following steps: S1: pre-hydrolysis reaction is carried out by adding silicon tetrachloride into ethanol at 20-35℃ to obtain reaction liquid 1; S2: further hydrolytic polycondensation reaction is carried out by adding reaction liquid 1 into a mixed solvent of ethanol and water to obtain sol, wherein the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 4:1-16; S3: the sol obtained in step S2 is aged or treated by vacuum concentration to obtain wet gel; S4: the wet gel is dried, calcined and crushed to obtain the low-defect amorphous silicon dioxide.

2. The method of claim 1, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S1, the volume ratio of silicon tetrachloride to ethanol is 6:10-50.

3. The method of claim 2, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S1, the volume ratio of silicon tetrachloride to ethanol is 6:10-20.

4. The method of claim 1, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S1, the dropping speed of silicon tetrachloride into ethanol is 20-40 mL / h.

5. The method of claim 1, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S2, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 4:1-4.

6. The method of claim 1, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S2, the volume ratio of reaction liquid 1 to the mixed solvent of ethanol and water is 0.65-1.6:

1.

7. The method of claim 1, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S1, the pre-hydrolysis reaction time is 3-10 h; in step S2, the hydrolytic polycondensation reaction time is 3-10 h; and in step S3, the aging or vacuum concentration treatment time is 2-20 h.

8. The method of claim 1, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S4, the drying is air blowing drying, and the air blowing drying temperature is 80-110℃.

9. The method of claim 1, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S4, the calcination is staged calcination, first, the organic matter and carbon residue are removed by calcination under air condition; then, the hydroxyl defects are eliminated by increasing the temperature for hydroxyl removal treatment under vacuum environment; finally, the densification sintering is completed by further increasing the temperature under vacuum environment.

10. The method of claim 9, wherein the low-defect, amorphous silicon dioxide is prepared by, In step S4, the calcination is staged calcination, first, the organic matter and carbon residue are removed by calcination under air condition; then, the hydroxyl defects are eliminated by increasing the temperature for hydroxyl removal treatment under vacuum environment; finally, the densification sintering is completed by further increasing the temperature under vacuum environment.

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