Preparation method of high-purity opaque quartz glass
By using a high-purity silica sol preparation and acrylamide gel system reinforcement, the problems of uneven pore distribution and impurity introduction in high-purity opaque quartz glass were solved, achieving stable light-shielding performance and impurity control, making it suitable for high-end applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU DEXIN NEW MATERIAL TECH CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-05-01
AI Technical Summary
Existing methods for preparing high-purity opaque quartz glass suffer from problems such as the difficulty in uniformly mixing the pore-forming agent, leading to unstable light-blocking performance and the easy introduction of metallic impurities.
A high-purity silica sol preparation method was adopted, which prepared multi-particle-size silica sol through silica hydrolysis and sol-gel methods. The wet gel was enhanced by combining an acrylamide gel system to control the pore distribution, and the pore size and density were controlled by melting under negative pressure.
It achieves uniform pore distribution, stable light-blocking performance, and low impurity content, making it suitable for high-end applications.
Smart Images
Figure CN121948814A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic non-metallic material preparation technology, specifically a method for preparing high-purity opaque quartz glass. Background Technology
[0002] High-purity opaque quartz glass is an opaque quartz glass material in which a large number of micron-sized bubbles are uniformly distributed in a high-purity silica matrix. While maintaining the high purity, high temperature resistance, low coefficient of thermal expansion, and chemical stability of quartz glass, it achieves a light-blocking effect through the scattering of light by the bubbles and can block heat radiation. It is suitable for projection light source reflector substrates and key components of heat treatment equipment in the semiconductor and photovoltaic industries.
[0003] Existing preparation methods mainly include:
[0004] (1) Adding pore-forming agent method: The pore-forming agent is mixed with quartz sand and then directly melted and molded. However, the pore-forming agent and quartz sand have large differences in density, particle size and surface properties, making it difficult to mix evenly and easy to agglomerate, resulting in decreased strength and unstable light-blocking performance.
[0005] (2) Wet grinding and forming method without adding pore-forming agent: Quartz sand is crushed, ball-milled and granulated into blanks and then melted / sintered. This method is prone to introducing metal impurities generated by the wear of grinding media during the crushing and ball-milling stage, which are difficult to remove in the later stage, affecting the purity of the final product and limiting its use in high-end applications. Summary of the Invention
[0006] (a) Technical problems to be solved
[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing high-purity opaque quartz glass, which has the advantages of avoiding the introduction of contaminants while achieving uniform and controllable pores.
[0008] (II) Technical Solution
[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-purity opaque quartz glass, comprising the following steps:
[0010] s1. Preparation of high-purity silica sol: Multiple groups of high-purity silica sols with particle sizes of 20-500 nm can be prepared using methods such as silica hydrolysis and sol-gel methods.
[0011] s2. Blending of high-purity silica sols of various particle sizes: The high-purity silica sols of different particle sizes from step 1 are blended and mixed in proportion, and then concentrated under reduced pressure until the silica content reaches 40-60%.
[0012] s3. The gel-enhancing system is added using an acrylamide system. The monomer, initiator, and crosslinking agent are mixed into an aqueous solution, and then the high-purity silica sol prepared in step 2 is added in proportion.
[0013] s4. Sol-gelation: Heat the mixed solution from step 3 to 30-40℃ to gel the solution. After gelation, continue to keep it at this temperature to increase the gel strength.
[0014] s5. Drying of the wet gel: The above wet gel is dried at a low temperature of 60-80℃ until the moisture content is <5%.
[0015] s6. Gel melting: After drying, the gel preform is frequently dehydrated and deorganized by pressure, and then melted under negative pressure to obtain high-purity opaque quartz glass.
[0016] Preferably, the high-purity silica sol in s1 can be prepared by one of the following methods: silica hydrolysis, sol-gel method, and ion exchange method. The impurity content in the high-purity silica sol should be less than 1 ppm. The different particle sizes are 30-40 nm, 70-80 nm, 150-200 nm, and 350-400 nm, wherein the 350-400 nm size is a suspension of silica microspheres.
[0017] Preferably, the mass ratio of silica sol in s2 (based on the mass of silica in the solution) is 30-40nm: 70-80nm: 150-200nm: 350-400nm = 2.5-3.5: 3-4: 2-3: 1
[0018] Preferably, the gel reinforcement system in s3 is an acrylamide gel system, used to enhance the strength of the wet gel and reduce the risk of cracking during the gel drying process. The monomer is acrylamide, the crosslinking agent is N,N-methylenebisacrylamide, and the initiator is an azo initiator. The total mass of each component in the gel reinforcement system does not exceed 1% of the total weight of the silica solution in s3.
[0019] Preferably, the heating method in step s4 can be drying heating or drying water bath heating, and the heat preservation time is 12-72 hours.
[0020] Preferably, the drying temperature in step s5 is 60-80℃, the humidity is 80-95%, and the moisture content determination method adopts the drying method: the sample is placed in a 120℃ oven and kept at a constant weight, and the moisture content is calculated based on the mass difference.
[0021] Preferably, the melting process in step s6 includes the following steps:
[0022] Under normal pressure, the temperature is increased to 220-300℃ at a rate of 1℃ / minute, and held at that temperature for a sufficient period of time to remove free water from the green body.
[0023] Under normal pressure, continue to heat to 550-650℃ at a rate of 1℃ / min and hold, while introducing dry air or oxygen to fully oxidize and remove organic matter from the green body. Continue to heat to 1100-1200℃ at a rate of 1℃ / min and hold for 3-5 hours to improve the strength of the green body. Then, reduce the temperature to room temperature at a rate not exceeding 5℃ / min. At this point, a loose silica green body with a density of 1.7-2.0 g / cm3 is obtained.
[0024] The above-mentioned billet is transferred to a graphite container for further melting. After the air in the furnace is purged, nitrogen is introduced for protection. Under normal pressure, the temperature is rapidly increased to 1400-1650℃ at a rate of 8-10℃ / minute and held for 2-8 hours. During this process, due to the low thermal conductivity of silicon dioxide, the surface energy of the porous quartz billet is high, and the billet is densified first, thus retaining a large number of pores inside. As the temperature increases or the holding time increases, the internal pores undergo a process of shrinkage-sealing-pore merging and growth-pore migration and discharge. By controlling the temperature and holding time, the size and density of pores in the billet can be effectively controlled.
[0025] (III) Beneficial Effects
[0026] Compared with the prior art, the present invention provides a method for preparing high-purity opaque quartz glass, which has the following beneficial effects:
[0027] (1) Using high-purity silica sol with impurity content ≤1ppm as raw material and adopting the integral green body melting route, the introduction of external impurities can be significantly reduced, and the total impurity content of the product can be controlled within 5ppm.
[0028] (2) Sol-gel molding is used to obtain a uniform microstructured preform with more uniform pore distribution and better structural consistency.
[0029] (3) By adjusting the melting temperature and holding time, a uniform pore structure with controllable size and density can be obtained, so that the product has stable light-shielding and heat-insulating properties. Attached Figure Description
[0030] Figure 1 : A physical image of Embodiment 1 of the present invention;
[0031] Figure 2 : Spectral transmittance diagram of Embodiment 1 of the present invention;
[0032] Figure 3 : Spectral transmittance diagram of Example 2 of the present invention;
[0033] Figure 4 : Spectral transmittance diagram of Example 3 of the present invention;
[0034] Figure 5 Table showing the content of 16 impurities in Example 1 of this invention;
[0035] Figure 6 Table showing the content of 16 impurities in Example 2 of this invention;
[0036] Figure 7 Table showing the content of 16 impurities in Example 3 of this invention. Detailed Implementation
[0037] To better understand the purpose, structure, and function of this invention, the following detailed description of a method for preparing high-purity opaque quartz glass, in conjunction with the accompanying drawings, is provided.
[0038] Please see Figure 1-7 This invention relates to a method for preparing high-purity opaque quartz glass, comprising the following steps:
[0039] s1. Preparation of high-purity silica sol: Multiple groups of high-purity silica sols with particle sizes of 20-500 nm can be prepared using methods such as silica hydrolysis and sol-gel methods.
[0040] s2. Blending of high-purity silica sols of various particle sizes: The high-purity silica sols of different particle sizes from step 1 are blended and mixed in proportion, and then concentrated under reduced pressure until the silica content reaches 40-60%.
[0041] s3. The gel-enhancing system is added using an acrylamide system. The monomer, initiator, and crosslinking agent are mixed into an aqueous solution, and then the high-purity silica sol prepared in step 2 is added in proportion.
[0042] s4. Sol-gelation: Heat the mixed solution from step 3 to 30-40℃ to gel the solution. After gelation, continue to keep it at this temperature to increase the gel strength.
[0043] s5. Drying of the wet gel: The above wet gel is dried at a low temperature of 60-80℃ until the moisture content is <5%.
[0044] s6. Gel melting: After drying, the gel preform is frequently dehydrated and deorganized by pressure, and then melted under negative pressure to obtain high-purity opaque quartz glass.
[0045] The high-purity silica sol in S1 can be prepared by one of the following methods: silica hydrolysis, sol-gel method, or ion exchange method. The impurity content in the high-purity silica sol should be less than 1 ppm. The different particle sizes are 30-40 nm, 70-80 nm, 150-200 nm, and 350-400 nm, where 350-400 nm is a suspension of silica microspheres.
[0046] The mass ratio of silica sol in S2 (based on the mass of silica in the solution) is 30-40nm: 70-80nm: 150-200nm: 350-400nm = 2.5-3.5: 3-4: 2-3: 1
[0047] The gel reinforcement system in S3 is an acrylamide gel system, used to enhance the strength of the wet gel and reduce the risk of cracking during the gel drying process. The monomer is acrylamide, the crosslinking agent is N,N-methylenebisacrylamide, and the initiator is an azo initiator. The total mass of each component in the gel reinforcement system does not exceed 1% of the total weight of the silica solution in S3.
[0048] In S4, the heating method can be drying or water bath heating, with a holding time of 12-72 hours. In S5, the drying temperature is 60-80℃, the humidity is 80-95%, and the moisture content is determined by the drying method: the sample is placed in a 120℃ oven and kept at constant weight; the moisture content is calculated based on the mass difference.
[0049] The melting process in s6 includes the following steps:
[0050] Under normal pressure, the temperature is increased to 220-300℃ at a rate of 1℃ / minute, and held at that temperature for a sufficient period of time to remove free water from the green body.
[0051] Under normal pressure, continue to heat to 550-650℃ at a rate of 1℃ / min and hold, while introducing dry air or oxygen to fully oxidize and remove organic matter from the green body. Continue to heat to 1100-1200℃ at a rate of 1℃ / min and hold for 3-5 hours to improve the strength of the green body. Then, reduce the temperature to room temperature at a rate not exceeding 5℃ / min. At this point, a loose silica green body with a density of 1.7-2.0 g / cm3 is obtained.
[0052] The above-mentioned billet is transferred to a graphite container for further melting. After the air in the furnace is purged, nitrogen is introduced for protection. Under normal pressure, the temperature is rapidly increased to 1400-1650℃ at a rate of 8-10℃ / minute and held for 2-8 hours. During this process, due to the low thermal conductivity of silicon dioxide, the surface energy of the porous quartz billet is high, and the billet is densified first, thus retaining a large number of pores inside. As the temperature increases or the holding time increases, the internal pores undergo a process of shrinkage-sealing-pore merging and growth-pore migration and discharge. By controlling the temperature and holding time, the size and density of pores in the billet can be effectively controlled.
[0054] Example 1:
[0055] High-purity silica sols with particle sizes of 30-40 nm, 70-80 nm, 150-200 nm, and 350-400 nm were prepared using a single-element silica hydrolysis method with high-purity silica powder as raw material and ammonia water as catalyst. The 350-400 nm solution was a suspension of spherical silica. A nano-silica mixture was prepared by mixing silica sols at a mass ratio (based on the mass of silica in the solution) of 30-40 nm: 70-80 nm: 150-200 nm: 350-400 nm = 3.2: 3.6: 2.2: 1. This mixture was then concentrated under reduced pressure at room temperature until the silica content reached 50%. The pH of the solution was adjusted to 5.5-7 with lactic acid to obtain silica sol mixture A. ICP analysis was performed to determine the content of 16 impurities in the mixture. Figure 5 As shown:
[0056] A premix solution B was prepared using acrylamide as the monomer, NN-methylenebisacrylamide as the crosslinking agent, and azodicyanovalerate as the initiator, in a ratio of monomer:crosslinking agent:initiator:water = 10:0.5:0.1:100. After thoroughly mixing silica sol mixture A and premix solution B at a ratio of 25:1, the mixture was heated in a 40℃ water bath to induce gelation. After gelation, the mixture was kept at this temperature for 48 hours to improve gel strength.
[0057] The above-mentioned wet gel was dried at 80℃ and 90% humidity for at least 240 hours; then the temperature was increased to 100℃ and the humidity to 70-90% for at least 120 hours; finally, the temperature was increased to 120℃ and the humidity to 50-70% for at least 48 hours to obtain a dried silica gel preform. The moisture content was determined to be 3.8% using an oven-drying method.
[0058] The billet melting process is carried out in two stages:
[0059] The dried green body is placed in an atmospheric pressure electric furnace and heated to 280°C at a rate of 1°C / min, and held at that temperature for at least 15 hours to remove free water from the green body. The temperature is then increased to 600°C at a rate of 1°C / min and held at that temperature for at least 10 hours, while dry air or oxygen is introduced to allow the organic matter in the green body to be fully oxidized and volatilized. The temperature is then increased to 1200°C at a rate of 1°C / min and held at that temperature for 5 hours to improve the strength of the green body. Finally, the temperature is reduced to room temperature at a rate of 3°C / min. At this point, a loose silica green body is obtained, and its density is measured to be 1.75 g / cm3 using the water displacement method.
[0060] The above-mentioned preform was transferred to an atmosphere furnace for secondary melting. A graphite container was used to hold the silica preform, and after the air in the furnace was purged, nitrogen was introduced for protection. Under normal pressure, the temperature was rapidly increased to 1500℃ at a rate of 10℃ / min and held for 4 hours, then cooled to room temperature at a rate of 3℃ / min to obtain high-purity opaque quartz glass. Its density was determined to be 1.83 g / cm³ using the water displacement method.
[0061] Example 2
[0062] High-purity silica sols with particle sizes of 30-40 nm, 70-80 nm, 150-200 nm, and 350-400 nm were prepared using a single-element silica hydrolysis method with high-purity silica powder as raw material and ammonia water as catalyst. The 350-400 nm solution was a suspension of spherical silica. A nano-silica mixture was prepared by mixing silica sols at a mass ratio (based on the mass of silica in the solution) of 30-40 nm: 70-80 nm: 150-200 nm: 350-400 nm = 3.2: 3.6: 2.2: 1. This mixture was concentrated under reduced pressure at room temperature until the silica content reached 55%, and the pH was adjusted to 5.5-7 with lactic acid to obtain silica sol mixture A. ICP analysis was performed to determine the content of 16 impurities in the mixture. Figure 6 As shown:
[0063] A premix solution B was prepared using acrylamide as the monomer, N,N-methylenebisacrylamide as the crosslinking agent, and azodicyanovalerate as the initiator, in a ratio of monomer:crosslinking agent:initiator:water = 10:0.5:0.1:100. After thoroughly mixing silica sol mixture A and premix solution B at a ratio of 25:1, the mixture was heated in a 40°C water bath to induce gelation. After gelation, the mixture was kept at this temperature for 96 hours to improve gel strength.
[0064] The above-mentioned wet gel was dried at 80℃ and 90% humidity for at least 240 hours; then the temperature was increased to 100℃ and the humidity to 70-90% for at least 120 hours; finally, the temperature was increased to 120℃ and the humidity to 50-70% for at least 48 hours to obtain a dried silica gel preform. The moisture content was determined to be 3.4% using an oven-drying method.
[0065] The billet melting process is carried out in two stages:
[0066] The dried green body was placed in an atmospheric pressure electric furnace and heated to 280°C at a rate of 1°C / min, and held at that temperature for at least 15 hours to remove free water from the green body. The temperature was then increased to 600°C at a rate of 1°C / min and held at that temperature for at least 10 hours, while dry air or oxygen was introduced to allow the organic matter in the green body to be fully oxidized and volatilized. The temperature was then increased to 1100°C at a rate of 1°C / min and held at that temperature for 5 hours to improve the strength of the green body. Finally, the temperature was reduced to room temperature at a rate of 3°C / min. At this point, a loose silica green body was obtained, and its density was measured to be 1.71 g / cm3 using the water displacement method.
[0067] The above-mentioned preform was transferred to an atmosphere furnace for secondary melting. A graphite container was used to support the silica preform, and after the air in the furnace was purged, nitrogen was introduced for protection. Under normal pressure, the temperature was rapidly increased to 1600℃ at a rate of 10℃ / min and held for 4 hours, then cooled to room temperature at a rate of 3℃ / min to obtain high-purity opaque quartz glass. Its density was determined to be 1.86 g / cm³ using the water displacement method.
[0068] Example 3
[0069] High-purity silica sols with particle sizes of 30-40 nm, 70-80 nm, 150-200 nm, and 350-400 nm were prepared by hydrolysis of tetraethyl orthosilicate (TES) with ammonia as a catalyst. The 350-400 nm solution was a suspension of spherical silica. A nano-silica mixture was prepared by mixing silica sols at a mass ratio (based on the mass of silica in the solution) of 30-40 nm: 70-80 nm: 150-200 nm: 350-400 nm = 3.2: 3.6: 2.2: 1. This mixture was concentrated under reduced pressure at room temperature until the silica content reached 55%, and the pH was adjusted to 5.5-7 with lactic acid to obtain silica sol mixture A. ICP analysis was performed to determine the content of 16 impurities in this mixture. Figure 7 As shown:
[0070] A premix solution B was prepared using acrylamide as the monomer, N,N-methylenebisacrylamide as the crosslinking agent, and azodicyanovalerate as the initiator, in a ratio of monomer:crosslinking agent:initiator:water = 10:0.5:0.1:100. After thoroughly mixing silica sol mixture A and premix solution B at a ratio of 25:1, the mixture was heated in a 40°C water bath to induce gelation. After gelation, the mixture was kept at this temperature for 96 hours to improve gel strength.
[0071] The above-mentioned wet gel was dried at 80℃ and 90% humidity for at least 240 hours; then the temperature was increased to 100℃ and the humidity to 70-90% for at least 120 hours; finally, the temperature was increased to 120℃ and the humidity to 50-70% for at least 48 hours to obtain a dried silica gel preform. The moisture content was determined to be 3.7% using an oven-drying method.
[0072] The billet melting process is carried out in two stages:
[0073] The dried green body is placed in an atmospheric pressure electric furnace and heated to 280°C at a rate of 1°C / min, and held at that temperature for at least 15 hours to remove free water from the green body. The temperature is then increased to 600°C at a rate of 1°C / min and held at that temperature for at least 10 hours, while dry air or oxygen is introduced to allow the organic matter in the green body to be fully oxidized and volatilized. The temperature is then increased to 1100°C at a rate of 1°C / min and held at that temperature for 5 hours to improve the strength of the green body. Finally, the temperature is reduced to room temperature at a rate of 3°C / min. At this point, a loose silica green body is obtained, and its density is measured to be 1.76 g / cm3 using the water displacement method.
[0074] The aforementioned preform was transferred to an atmosphere furnace for secondary melting. A graphite container was used to support the silica preform, and after the air in the furnace was purged, nitrogen was introduced for protection. Under normal pressure, the temperature was rapidly increased to 1600℃ at a rate of 10℃ / min and held for 4 hours, then cooled to room temperature at a rate of 3℃ / min to obtain high-purity opaque quartz glass. Its density was determined to be 1.85 g / cm³ using the water displacement method.
[0075] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.
Claims
1. A method for preparing high-purity opaque quartz glass, characterized in that... The steps involved are as follows: s1. Preparation of high-purity silica sol: Multiple groups of high-purity silica sol with particle sizes of 20-500nm can be prepared by methods such as silica hydrolysis and sol-gel method. s2. Blending of high-purity silica sols of various particle sizes: The high-purity silica sols of different particle sizes in step 1 are blended and mixed in proportion, and concentrated under reduced pressure until the silica content is 40-60%. s3. The gel reinforcement system is added by using an acrylamide system, mixing monomers, initiators, and crosslinking agents into an aqueous solution, and then adding the high-purity silica sol prepared in step 2 in proportion. s4. Sol-gelation: Heat the mixed solution from step 3 to 30-40℃ to gel the solution. After gelation, continue to keep it warm to improve the gel strength. s5. Drying of wet gel: The above wet gel is dried at a low temperature of 60-80℃ until the moisture content is <5%; s6. Gel melting: After drying, the gel preform is frequently dehydrated and deorganized by pressure, and then melted under negative pressure to obtain high-purity opaque quartz glass.
2. The method for preparing high-purity opaque quartz glass according to claim 1, characterized in that: The high-purity silica sol in s1 can be prepared by one of the following methods: silica hydrolysis, sol-gel method, or ion exchange method. The impurity content in the high-purity silica sol should be less than 1 ppm. The different particle sizes are 30-40 nm, 70-80 nm, 150-200 nm, and 350-400 nm, where 350-400 nm is a suspension of silica microspheres.
3. The method for preparing high-purity opaque quartz glass according to claim 1, characterized in that: The mass ratio of silica sol in s2 (based on the mass of silica in the solution) is 30-40nm: 70-80nm: 150-200nm: 350-400nm = 2.5-3.5: 3-4: 2-3:
1.
4. The method for preparing high-purity opaque quartz glass according to claim 1, characterized in that: The gel reinforcement system in s3 is an acrylamide gel system; the monomer is acrylamide, the crosslinking agent is NN methylenebisacrylamide, the initiator is an azo initiator, and the total mass of each component in the gel reinforcement system does not exceed 1% of the total weight of the silica solution in 2.
5. The method for preparing high-purity opaque quartz glass according to claim 1, characterized in that: The heating method in s4 can be drying heating or drying water bath heating, and the heat preservation time is 12-72h.
6. The method for preparing high-purity opaque quartz glass according to claim 1, characterized in that: The drying temperature in s5 is 60-80℃ and the humidity is 80-95%. The moisture content determination method adopts the drying method: the sample is placed in a 120℃ oven and kept at constant weight, and the moisture content is calculated based on the mass difference.
7. The preparation method according to claim 1, characterized in that: The melting process in s6 includes the following steps: Under normal pressure, the temperature is increased to 220-300℃ at a rate of 1℃ / minute, and held at that temperature for a sufficient period of time to remove free water from the green body. Under normal pressure, continue to heat to 550-650℃ at a rate of 1℃ / min and hold, while introducing dry air or oxygen to fully oxidize and remove organic matter in the green body. Continue to heat to 1100-1200℃ at a rate of 1℃ / min and hold for 3-5 hours to improve the strength of the green body. Then, reduce to room temperature at a rate not exceeding 5℃ / min. At this point, a loose silica green body with a density of 1.7-2.0 g / cm3 is obtained. The above-mentioned billet is transferred to a graphite container for further melting. After the air in the furnace is purged, nitrogen is introduced for protection. Under normal pressure, the temperature is rapidly increased to 1400-1650℃ at a rate of 8-10℃ / minute and held for 2-8 hours. During this process, due to the low thermal conductivity of silicon dioxide, the surface energy of the loose quartz billet is high, and the billet is densified first, thus retaining a large number of pores inside. As the temperature rises or the holding time increases, the internal pores undergo a process of shrinkage-sealing-pore merging and growth-pore migration and discharge. By controlling the temperature and holding time, the size and density of pores in the billet can be effectively controlled.