Aluminum-doped quartz sand and method for producing the same

Abstract

The application provides aluminum-doped quartz sand and a preparation method thereof. The preparation method comprises the following steps: respectively performing impurity removal treatment on an aluminum sol and a silicon source to obtain the aluminum sol and the silicon source after impurity removal treatment; mixing the aluminum sol after impurity removal treatment with water, then adding the silicon source after impurity removal treatment and an acidic catalyst to perform a hydrolysis reaction, and obtaining an aluminum-doped silicon sol; performing first temperature rising treatment on the aluminum-doped silicon sol, then adjusting the pH value to 7.5-12 to obtain a gel; wherein the temperature of the first temperature rising treatment is higher than that of the hydrolysis reaction; and after sequentially performing drying treatment, calcination treatment and second temperature rising treatment on the gel, aluminum-doped quartz sand is obtained; wherein the temperature of the second temperature rising treatment is higher than that of the calcination treatment, the calcination treatment is performed in an oxygen-containing atmosphere, and the second temperature rising treatment is performed under vacuum conditions. The aluminum-doped quartz sand prepared by the method has high purity and excellent high-temperature resistance.

Description

Technical Field

[0001] This invention belongs to the field of quartz sand modification technology, specifically relating to an aluminum-doped quartz sand and its preparation method. Background Technology

[0002] Quartz crucibles, used to hold molten silicon, are widely applied in semiconductor, photovoltaic, and other fields. With the development of the Internet of Things and information technology, higher requirements have been placed on the purity and high temperature resistance of quartz crucibles. High-purity quartz sand (SiO2 ≥ 99.998%) is a key raw material for the production of quartz crucibles, and its quality determines the quality of the crucible. However, under high-temperature melting conditions, elements in high-purity quartz sand easily separate and re-exist in solid form; this process is called crystallization. When crystallization occurs on the inner wall of the quartz crucible, it leads to a decrease in the crucible's mechanical strength, thus affecting its stability under high-temperature conditions.

[0003] Currently, the high-temperature resistance of quartz crucibles is often improved by adding an appropriate amount of aluminum to high-purity quartz sand to slow down crystallization. For example, patent documents CN109467306A, CN110820041A, CN110713343A, and CN112299864A involve adding aluminum to high-purity quartz sand through post-processing. However, the aluminum added in this method simply adheres to the surface of the quartz sand, resulting in uneven distribution and further deteriorating the high-temperature resistance of the crucible. Another method involves adding aluminum-containing compounds during the synthesis of the quartz sand precursor, as shown in patent document CN114044520A. However, this method also introduces other anions into the quartz sand, affecting its purity.

[0004] Therefore, how to obtain high-purity, high-temperature-resistant quartz sand is a long-term research topic in this field. Summary of the Invention

[0005] This invention provides a method for preparing aluminum-doped quartz sand. By controlling the feeding sequence, calcination treatment, two heating treatments, and atmospheric conditions, the method ultimately obtains aluminum-doped quartz sand with high purity and excellent high-temperature resistance.

[0006] This invention provides an aluminum-doped quartz sand, which has advantages such as high purity and excellent high-temperature resistance.

[0007] In a first aspect, the present invention provides a method for preparing aluminum-doped quartz sand, comprising the following steps:

[0008] The aluminum sol and silicon source were respectively subjected to impurity removal treatment to obtain the impurity-removed aluminum sol and silicon source.

[0009] The aluminum sol after impurity removal treatment is mixed with water, and then a silicon source and an acidic catalyst after impurity removal treatment are added to carry out a hydrolysis reaction to obtain aluminum-doped silicon sol.

[0010] The aluminum-doped silica sol is subjected to a first heating treatment, and then the pH value is adjusted to 7.5-12 to obtain a gel; wherein the temperature of the first heating treatment is higher than the temperature of the hydrolysis reaction;

[0011] The gel was subjected to drying, calcination, and a second heating treatment in sequence to obtain aluminum-doped quartz sand; wherein the temperature of the second heating treatment was higher than the temperature of the calcination treatment, the calcination treatment was carried out in an oxygen-containing atmosphere, and the second heating treatment was carried out under vacuum conditions.

[0012] In the preparation method described above, the impurity removal treatment is selected from one of ion exchange, extraction, and ultrafiltration; and / or,

[0013] The temperature of the first heating treatment is 10–30°C higher than the temperature of the hydrolysis reaction; and / or,

[0014] The temperature of the second heating treatment is 300-600°C higher than the temperature of the roasting treatment.

[0015] In the preparation method described above, the mass ratio of the acidic catalyst to water is (0.1–0.5):1; and / or,

[0016] The molar ratio of the silicon source to water is 1:(4-15).

[0017] In the preparation method described above, the hydrolysis reaction is carried out at a temperature of 40–90°C; and / or,

[0018] The drying process is carried out at a temperature of 100–300°C for 1–12 hours.

[0019] In the preparation method described above, the calcination treatment is carried out at a temperature of 600–1000°C for a time of 5–40 h; and / or,

[0020] The second heating process takes 3 to 20 hours.

[0021] In the preparation method described above, the pH value is adjusted to 7.5-12 by adding an alkaline substance, and the addition rate of the alkaline substance is 2-15 mL / min.

[0022] In the preparation method described above, the silicon source includes at least one selected from tetraethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, pentyl orthosilicate, isopropyl orthosilicate, isobutyl orthosilicate, isoamyl orthosilicate, dimethyl orthosilicate, diethyl orthosilicate, and diisopropyl orthosilicate; and / or,

[0023] The alumina solid content in the alumina sol is 8% to 25%.

[0024] In the preparation method described above, the acidic catalyst is an aqueous solution containing an acidic substance.

[0025] Among them, acidic substances include at least one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, propionic acid, acetic acid, benzoic acid, and oxalic acid;

[0026] The concentration of acidic substances in the aqueous solution is 0.1–2 mol / L.

[0027] In a second aspect, the present invention provides an aluminum-doped quartz sand, which is prepared by the aluminum-doped quartz sand preparation method described above.

[0028] The aluminum-doped quartz sand described above, wherein the mass content of aluminum element in the aluminum-doped quartz sand is 3 to 30 ppm.

[0029] The implementation of this invention has at least the following beneficial effects:

[0030] This invention provides a method for preparing aluminum-doped quartz sand. The method involves mixing aluminum sol with water and then adding a silicon source. By adjusting the timing of the two heating processes and the atmospheric conditions of the calcination and second heating processes, the purity of the aluminum-doped quartz sand is maximized, while ensuring a more uniform distribution of aluminum in the quartz sand. Ultimately, the resulting aluminum-doped quartz sand has advantages such as high purity and excellent high-temperature resistance. Attached Figure Description

[0031] Figure 1 This is a flowchart of a method for preparing aluminum-doped quartz sand according to one embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] like Figure 1As shown, in a first aspect, the present invention provides a method for preparing aluminum-doped quartz sand, comprising the following steps:

[0034] The aluminum sol and silicon source were respectively subjected to impurity removal treatment to obtain the impurity-removed aluminum sol and silicon source.

[0035] The aluminum sol after impurity removal treatment is mixed with water, and then a silicon source and an acidic catalyst after impurity removal treatment are added to carry out a hydrolysis reaction to obtain aluminum-doped silicon sol.

[0036] The aluminum-doped silica sol was subjected to a first heating treatment, and then the pH value was adjusted to 7.5-12 to obtain a gel; wherein the temperature of the first heating treatment was higher than the temperature of the hydrolysis reaction.

[0037] Aluminum-doped quartz sand was obtained by sequentially drying, calcining, and a second heating treatment on the gel. The temperature of the second heating treatment was higher than that of the calcining treatment. The calcining treatment was carried out in an oxygen-containing atmosphere, and the second heating treatment was carried out under vacuum conditions.

[0038] This invention does not limit the specific sources of the aluminum sol and silicon source; conventional aluminum sol and silicon sources in the art can be used. The impurity removal process is to remove metallic impurities from the aluminum sol and silicon source, purifying them to further improve the purity of the final product.

[0039] After the impurity-removed aluminum sol is uniformly mixed with water, a silicon source and an acidic catalyst are added to initiate a hydrolysis reaction. It is understood that the acidic catalyst can initiate the hydrolysis of the silicon source and promote the uniform incorporation of the aluminum sol into the silica sol, forming silicon-oxygen-aluminum bonds. By limiting the above-mentioned order of addition, it is beneficial to better control the nucleation rate of the silica sol, allowing for more uniform incorporation of aluminum into the silica sol, resulting in aluminum-doped silica sol.

[0040] Organic substances may be generated during the hydrolysis reaction; therefore, the gel contains a small amount of organic matter.

[0041] This invention is not limited to the above-described mixing process; conventional stirring and mixing methods in the art can be used. For example, in one embodiment, under rapid stirring, the impurity-removed aluminum sol is first mixed evenly with water to fully disperse the aluminum sol in deionized water. Then, impurity-removed tetraethyl orthosilicate is added, and mixing continues. Next, an acidic catalyst is added, and stirring is continued under hydrolysis reaction conditions to completely hydrolyze the tetraethyl orthosilicate, forming an aluminum-doped silica sol.

[0042] Before adjusting the pH value, the aluminum-doped silica sol was subjected to a first heating treatment. The first heating treatment is essentially a heating process based on the hydrolysis reaction, which raises the temperature of the aluminum-doped silica sol. This helps to improve the strength and stability of the gel.

[0043] Under the initial heating temperature conditions, by adjusting the pH value of the aluminosilicate sol, the conditions of the aluminosilicate sol are ensured to remain constant throughout the reaction process. This effectively controls the reaction rate and extent, ensuring that the formed gel has the expected properties and structure. Specifically, the pH value is adjusted to 7.5–12, for example, a range of 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11, 11.5, 12, or any combination thereof. If the pH value is higher than 12 or lower than 7.5, it may lead to runaway reaction, affecting the gel's properties. Furthermore, this invention, through real-time monitoring of the pH value, allows for accurate understanding of the reaction status and adjustments as needed, thereby further improving the strength and stability of the gel product.

[0044] The gel was subjected to drying, calcination, and a second heating treatment in sequence. The drying treatment was to remove excess moisture from the gel; the calcination treatment was to remove organic matter from the gel, thereby improving the purity of the product. At the same time, the calcination treatment could strengthen the silicon-oxygen-aluminum bonds and ensure the integrity of the structure; the second heating treatment was essentially an increase in temperature based on the calcination treatment, which helped to improve the efficiency of the dehydroxylation reaction, further promoting the removal of hydroxyl groups and improving the purity of the product.

[0045] The oxygen-containing atmosphere can be air, pure oxygen, or any other gas doped with oxygen in an inert atmosphere. In an oxygen-containing atmosphere, organic matter is more easily oxidized and decomposed, which effectively removes organic matter from the gel, thereby improving its purity. Furthermore, oxygen helps stabilize the gel's crystal structure, further strengthening the silicon-oxygen-aluminum bonds, thus maintaining the integrity of the gel structure.

[0046] The second heating process is carried out under vacuum conditions. This is because the lower pressure under vacuum allows the water vapor formed after hydroxyl group removal to escape more quickly, thus facilitating the hydroxyl group removal process. Simultaneously, the vacuum environment helps prevent the recombination of hydroxyl groups removed at high temperatures on the product surface, thereby more effectively eliminating hydroxyl groups from the product. Furthermore, the higher temperature of the second heating process compared to the calcination process further enhances the efficiency of the dehydroxylation reaction, promoting hydroxyl group removal.

[0047] According to the research of this invention, the aluminum-doped quartz sand prepared by the above-mentioned method exhibits high purity and excellent high-temperature resistance. This is because, on the one hand, by mixing aluminum sol with water and then adding a silicon source and an acidic catalyst, it is beneficial to better control the nucleation rate of the silica sol, allowing aluminum to be more uniformly incorporated into the silica sol; on the other hand, by adjusting the temperature and timing of the two heating processes, as well as the atmosphere conditions of the calcination and second heating processes, the purity and mechanical strength of the aluminum-doped quartz sand are maximized, ultimately resulting in aluminum-doped quartz sand with advantages such as high purity and excellent high-temperature resistance.

[0048] In some embodiments, the impurity removal process is selected from one of ion exchange, extraction, and ultrafiltration. Ion exchange refers to the separate impurity removal treatment of the alumina sol and silicon source using ion exchange resin. Specifically, the alumina sol and silicon source are separately passed through an ion exchanger containing ion exchange resin. As they flow through the resin, impurity ions in the alumina sol and silicon source are adsorbed, thereby achieving purification. Extraction refers to the separate extraction of the alumina sol and silicon source using an organic solvent, thereby separating impurities. Ultrafiltration refers to the separation of impurities using an ultrafiltration membrane.

[0049] Aluminum sol and silicon source can be treated with the same purification process, or they can be treated with different purification processes.

[0050] When using ion exchange to remove impurities from aluminum sol and silicon sources, the ion exchange resin used can be one or more of the following: strong acid ion exchange resin, chelating ion exchange resin, and selective ion exchange resin.

[0051] This invention does not limit the temperatures of the first heating treatment and the second heating treatment. For example, the temperature of the first heating treatment is 10 to 30°C higher than the temperature of the hydrolysis reaction, such as 10°C, 15°C, 20°C, 25°C, 30°C, or any combination thereof; and / or, the temperature of the second heating treatment is 300 to 600°C higher than the temperature of the calcination treatment, such as 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, or any combination thereof.

[0052] This invention does not limit the amount of aluminum sol, silicon source, acid catalyst, and water added. For example, the mass ratio of acid catalyst to water is (0.1 to 0.5):1, such as 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or any combination thereof; and / or, the molar ratio of silicon source to water is 1:(4 to 15), such as 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, or any combination thereof.

[0053] In this invention, after adjusting the pH value to 7.5-12, aging is also included. The main purpose of the aging process is to promote the further development and maturation of the gel structure, enhance the connection between silicon and aluminum species in the gel, and form more stable silicon-oxygen-aluminum bonds, which helps to achieve a more stable and uniform aluminum doping effect.

[0054] This invention does not limit the temperature of the hydrolysis reaction or the drying process, as long as the temperature of the hydrolysis reaction is sufficient to allow the silicon source to hydrolyze, and the drying process is sufficient to remove excess moisture. In some embodiments, the temperature of the hydrolysis reaction is 40–90°C, for example, 40°C, 45°C, 50°C, 60°C, 70°C, 80°C, 90°C, or any combination thereof; and / or, the temperature of the drying process is 100–300°C, for example, 100°C, 150°C, 200°C, 250°C, 300°C, or any combination thereof, and the time is 1–12 hours, for example, 1 hour, 2 hours, 5 hours, 8 hours, 10 hours, 12 hours, or any combination thereof.

[0055] The present invention does not limit the specific parameters of the calcination treatment and the second heating treatment. For example, in some embodiments, the temperature of the calcination treatment is 600 to 1000°C, such as 600°C, 650°C, 700°C, 800°C, 900°C, 1000°C or any combination thereof, and the time is 5 to 40 hours, such as 5 hours, 10 hours, 20 hours, 30 hours, 40 hours or any combination thereof; and / or, the time of the second heating treatment is 3 to 20 hours, such as 3 hours, 5 hours, 10 hours, 15 hours, 20 hours or any combination thereof.

[0056] The present invention does not limit the specific operational steps for adjusting the pH value to 7.5-12. For example, in some embodiments, the pH value is adjusted to 7.5-12 by adding an alkaline substance. The alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, ammonia, methylamine, ethylamine, propylamine, tert-butylamine, p-toluidine, aniline, dimethylamine, ethylenediamine, ethanolamine, propylenediamine, vinylamine, sodium carbonate, calcium hydroxide, potassium carbonate, sodium bicarbonate, ammonium hydroxide, sodium dihydrogen phosphate, and potassium dihydrogen phosphate. The rate of addition of the alkaline substance is 2-15 mL / min.

[0057] By controlling the addition rate of the alkaline substance, a uniform distribution among the components can be maintained, which helps to form a gel with good homogeneity and stability. The addition rate of the alkaline substance is 2–15 mL / min, for example, 2 mL / min, 5 mL / min, 8 mL / min, 10 mL / min, 12 mL / min, 14 mL / min, 15 mL / min, or any combination thereof. If the addition rate of the alkaline substance is too fast, it may cause a gradient in the aluminosilicate sol, thereby affecting the strength and stability of the gel.

[0058] The present invention does not impose excessive restrictions on the selection of various raw materials. For example, the silicon source includes at least one of tetraethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, pentyl orthosilicate, isopropyl orthosilicate, isobutyl orthosilicate, isoamyl orthosilicate, dimethyl orthosilicate, diethyl orthosilicate, and diisopropyl orthosilicate; and / or, the solid content of alumina in the aluminum sol is 8% to 25%, for example, 8%, 10%, 15%, 20%, 25%, or any combination thereof.

[0059] In some embodiments, the acidic catalyst is an aqueous solution containing an acidic substance, wherein the acidic substance includes at least one selected from nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, propionic acid, acetic acid, benzoic acid, and oxalic acid; the concentration of the acidic substance in the aqueous solution is 0.1 to 2 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, or any combination thereof.

[0060] In a second aspect, the present invention provides an aluminum-doped quartz sand, which is prepared by the aluminum-doped quartz sand preparation method of the first aspect described above.

[0061] Due to the unique nature of the aforementioned preparation method, the aluminum-doped quartz sand obtained by this method has high purity and excellent high-temperature resistance, and can be used stably in harsh high-temperature application environments.

[0062] In some embodiments, the mass content of aluminum in the aluminum-doped quartz sand is 3 to 30 ppm, for example, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, or any combination thereof. When the mass content of aluminum is within the above range, both the purity of the aluminum-doped quartz sand and its high-temperature resistance can be improved.

[0063] The present invention will be further described below through specific embodiments and comparative examples.

[0064] Example 1

[0065] (1) Aluminum sol with a solid content of 20% and tetraethyl orthosilicate were respectively passed through an aminoalkyl phosphate chelating cation exchange resin to remove the metal impurities contained therein, so as to obtain aluminum sol and tetraethyl orthosilicate after impurity removal treatment.

[0066] (2) Under rapid stirring, 0.0327 g of the impurity-removed aluminum sol (aluminum doping amount of about 10 ppm) was mixed with 1200 g of deionized water (conductivity ≤ 0.01 mS / m) to make the aluminum sol fully dispersed in the deionized water. Then, 1200 g of impurity-removed tetraethyl orthosilicate was added and the mixture was continued to be mixed for 30 min. Then, 240 mL of 1 mol / L electronic grade hydrochloric acid was added as an acid catalyst. The mixture was heated to 60 °C and stirred continuously to make the tetraethyl orthosilicate completely hydrolyze to form aluminum-doped silica sol.

[0067] (3) Raise the temperature to 80℃, add 28% electronic grade ammonia water at a rate of about 5mL / min to the aluminum-doped silica sol, and monitor the pH value in real time. Adjust the pH value to about 10 and maintain the aging process for 1 hour to form a gel.

[0068] (4) The gel was washed with deionized water and filtered until neutral. Then it was dried at 120°C for 8 hours. The dried material was then calcined in an air atmosphere of 80 mL / min: the temperature was increased from 50°C to 800°C at 2°C / min for 6 hours. Then the vacuum was drawn to an absolute pressure of 5 Pa, and the temperature was increased from 800°C to 1400°C at 2°C / min for 24 hours. Finally, the temperature was cooled to room temperature to obtain aluminum-doped quartz sand.

[0069] Example 2

[0070] The preparation process is basically the same as in Example 1, except that the amount of aluminum sol added is different. In this example, the amount of aluminum sol added is 0.0164g, and other conditions remain unchanged.

[0071] Example 3

[0072] The preparation process is basically the same as in Example 1, except that the solid content and amount of aluminum sol added are different. In this example, the solid content of aluminum sol is 10% and the amount added is 0.0654g, while other conditions remain unchanged.

[0073] Example 4

[0074] The preparation process is basically the same as in Example 1, except that the type and amount of silicon source used are different. In this example, the silicon source used is tetramethyl orthosilicate, and the amount added is 876.6g. Other conditions remain unchanged.

[0075] Example 5

[0076] The preparation process is basically the same as in Example 1, except that the silicon source used is tetrabutyl orthosilicate, while other conditions remain unchanged.

[0077] Example 6

[0078] The preparation process is basically the same as in Example 1, except that the silicon source used is amyl orthosilicate, while other conditions remain unchanged.

[0079] Example 7

[0080] The preparation process is basically the same as in Example 1, except that the silicon source used is isopropyl orthosilicate, while other conditions remain unchanged.

[0081] Example 8

[0082] The preparation process is basically the same as in Example 1, except that the silicon source used is isobutyl orthosilicate, while other conditions remain unchanged.

[0083] Example 9

[0084] The preparation process is basically the same as in Example 1, except that the silicon source used is isoamyl orthosilicate, while other conditions remain unchanged.

[0085] Example 10

[0086] The preparation process is basically the same as in Example 1, except that the silicon source used is dimethyl orthosilicate, while other conditions remain unchanged.

[0087] Example 11

[0088] The preparation process is basically the same as in Example 1, except that the silicon source used is diethyl orthosilicate, while other conditions remain unchanged.

[0089] Example 12

[0090] The preparation process is basically the same as in Example 1, except that the silicon source used is diisopropyl orthosilicate, while other conditions remain unchanged.

[0091] Example 13

[0092] The preparation process is basically the same as that in Example 1, except that the aluminum sol used has a solid content of 8% and an addition amount of 0.0818 grams.

[0093] Example 14

[0094] The preparation process is basically the same as that in Example 1, except that the aluminum sol used has a solid content of 25% and an addition amount of 0.0262 grams.

[0095] Example 15

[0096] The preparation process is basically the same as in Example 1, except that the rate at which electronic-grade ammonia is added to the aluminum-doped silica sol is 1 mL / min.

[0097] Example 16

[0098] The preparation process is basically the same as in Example 1, except that the rate at which electronic-grade ammonia water is added to the aluminum-doped silica sol is 2 mL / min.

[0099] Example 17

[0100] The preparation process is basically the same as in Example 1, except that the rate at which electronic-grade ammonia water is added to the aluminum-doped silica sol is 15 mL / min.

[0101] Example 18

[0102] The preparation process is basically the same as in Example 1, except that the rate at which electronic-grade ammonia water is added to the aluminum-doped silica sol is 20 mL / min.

[0103] Example 19

[0104] The preparation process is basically the same as in Example 1, except that the amount of aluminum sol added is different. In this example, the amount of aluminum sol added is 0.12g, and other conditions remain unchanged.

[0105] Comparative Example 1

[0106] (1) Under rapid stirring, 0.128 mL of 1 mol / L aluminum nitrate aqueous solution (where the molar amount of aluminum is the same as that of aluminum sol in Example 1) was added to 1200 g of deionized water (conductivity ≤ 0.01 mS / m) and mixed evenly for 30 min to fully disperse the aluminum sol in the deionized water. Then, 1200 g of tetraethyl orthosilicate after impurity removal was added and the mixture was continued for 30 min. Then, 240 mL of 1 M electronic grade hydrochloric acid was added as an acidic catalyst, heated to 60 °C and stirred continuously to completely hydrolyze the tetraethyl orthosilicate to form aluminum-doped silica sol.

[0107] (2) Raise the temperature to 80℃, add 28% electronic grade ammonia water at a rate of about 5mL / min to the aluminum-doped silica sol, and monitor the pH value in real time. Adjust the pH value to about 10 and maintain the aging process for 1 hour to form a gel.

[0108] (3) The gel was washed with deionized water and filtered until neutral. Then it was dried at 120°C for 8 hours. The dried material was then calcined in an air atmosphere of 80 mL / min: the temperature was increased from 50°C to 800°C at 2°C / min for 6 hours. Then the vacuum was drawn to an absolute pressure of 5 Pa, and the temperature was increased from 800°C to 1400°C at 2°C / min for 24 hours. Finally, the temperature was cooled to room temperature to obtain aluminum-doped quartz sand.

[0109] Comparative Example 2

[0110] The preparation process is basically the same as that in Example 1, except that the order of adding raw materials in step (2) is different. Specifically, under rapid stirring, 1200g of purified tetraethyl orthosilicate and 1200g of deionized water (conductivity ≤0.01mS / m) are mixed evenly for 30min. Then, 0.0327g of 20% solid content aluminum sol after purification is added and mixed for another 30min. Then, 240mL of 1M electronic grade hydrochloric acid is added as an acid catalyst. The mixture is heated to 60℃ and stirred continuously to completely hydrolyze the tetraethyl orthosilicate to form the aluminum-doped silica sol of this comparative example. The aluminum-doped silica sol in step (3) is replaced with the aluminum-doped silica sol of this comparative example, and other conditions remain unchanged to obtain aluminum-doped quartz sand.

[0111] Comparative Example 3

[0112] The difference from Example 1 is that the aluminum sol with a solid content of 20% is not subjected to impurity removal treatment in step (1), while other conditions remain unchanged.

[0113] Comparative Example 4

[0114] (1) Tetraethyl orthosilicate is passed through an aminoalkyl phosphate chelating cation exchange resin to remove the metallic impurities contained therein;

[0115] (2) Under rapid stirring, 1200g of purified tetraethyl orthosilicate and 1200g of deionized water (conductivity ≤0.01mS / m) were mixed evenly for 1h, and then 240mL of 1M electronic grade hydrochloric acid was added as an acid catalyst. The mixture was heated to 60℃ and stirred continuously to completely hydrolyze the tetraethyl orthosilicate to form a silica sol.

[0116] (3) Raise the temperature to 80℃, add 28% electronic grade ammonia water to the silica sol at a rate of about 5mL / min, and monitor the pH value in real time. Adjust the pH value to about 10 and maintain the aging process for 1 hour to form a gel.

[0117] (4) The gel was washed with deionized water and filtered until neutral, and then dried at 120°C for 8 hours. The dried material was then calcined in air at a rate of 80 mL / min: the temperature was increased from 50°C to 800°C at a rate of 2°C / min for 6 hours. Then, the temperature was evacuated to an absolute pressure of 5 Pa and increased from 800°C to 1400°C at a rate of 2°C / min for 24 hours. Finally, the temperature was cooled to room temperature to obtain the quartz sand sample.

[0118] Comparative Example 5

[0119] The preparation process is basically the same as that in Example 1, except that step (4) is: under an air atmosphere of 80 mL / min, the dried material is subjected to the following calcination process: directly from 50℃ to 1400℃ at 2℃ / min, the sample is treated for 24h, and finally cooled to room temperature to obtain aluminum-doped quartz sand.

[0120] Comparative Example 6

[0121] The preparation process is basically the same as that in Example 1, except that step (4) is as follows: under a nitrogen atmosphere of 80 mL / min, the dried material is subjected to the following calcination process: the temperature is increased from 50°C to 800°C at 2°C / min, and the sample is treated for 6 hours; then the vacuum is drawn to an absolute pressure of 5 Pa, the temperature is increased from 800°C to 1400°C at 2°C / min, and the sample is treated for 24 hours; finally, the temperature is cooled to room temperature to obtain aluminum-doped quartz sand.

[0122] Comparative Example 7

[0123] The preparation process is basically the same as that in Example 1, except that step (4) is as follows: under an air atmosphere of 80 mL / min, the dried material is subjected to the following calcination process: the temperature is increased from 50°C to 800°C at 2°C / min, the sample is treated for 6 hours, the atmosphere conditions are not changed, the temperature is increased from 800°C to 1400°C at 2°C / min, the sample is treated for 24 hours, and finally cooled to room temperature to obtain aluminum-doped quartz sand.

[0124] Test case

[0125] 1. Elemental Analysis

[0126] The samples prepared in the above examples and comparative examples were analyzed using ICP-MS. ICP-MS is a high-precision, high-sensitivity analytical method used to determine the content and distribution of trace elements in samples. ICP-MS analysis was used to understand the elemental content in the samples.

[0127] 2. Method for determining hydroxyl groups

[0128] Fourier transform infrared spectroscopy was used to measure the wavelength range of the Fourier transform infrared transmission spectra in the 3000 cm⁻¹ range of the above-described examples and comparative examples. The samples were ground with KBr and pressed into sheets. -1 ~3900m -1 The peak area was integrated, and the sand in the inner crucible of Unimin was measured immediately within 10 minutes after each measurement. The relative hydroxyl content was obtained by dividing the sample peak area by the Unimin sample peak area. Each sample was measured twice, and the average value was taken and retained to one decimal place to reduce measurement error.

[0129] 3. Stability Test

[0130] After melting the sample, it was poured into a mold to prepare two glass slides, each 100 mm long, 25 mm wide, and 3 mm thick. After polishing the glass slides, one slide was placed in a pressure measuring instrument to measure its pressure value, which was recorded as p0. The other slide was placed in a muffle furnace and kept at 1400℃ for 100 hours. The heating was then turned off, and the sample was removed after the furnace temperature dropped below 40℃. The pressure value was then measured using a pressure machine and recorded as p1. Δp was calculated using the formula Δp = p0 - p1. The larger Δp is, the worse the stability.

[0131] The test results are shown in Table 1.

[0132] Table 1

[0133]

[0134] As shown in Table 1, the Δp of the embodiments of the present invention is much smaller than that of the comparative examples, indicating that the samples of the embodiments have good stability under high temperature conditions, while the samples of the comparative examples have poor stability under high temperature conditions. This indicates that the aluminum-doped quartz sand prepared by the preparation method of the present invention has excellent high temperature resistance. Furthermore, the hydroxyl content of the samples of the embodiments does not exceed 1 ppm, which is lower than that of the samples of the comparative examples, indicating that the aluminum-doped quartz sand prepared by the preparation method of the present invention has higher purity.

[0135] The preferred embodiments and experimental verifications of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing aluminum-doped quartz sand, characterized in that, Includes the following steps: The aluminum sol and silicon source were respectively subjected to impurity removal treatment to obtain the impurity-removed aluminum sol and silicon source. The aluminum sol after impurity removal treatment is mixed with water, and then a silicon source and an acidic catalyst after impurity removal treatment are added to carry out a hydrolysis reaction to obtain aluminum-doped silicon sol. The aluminum-doped silica sol is subjected to a first heating treatment, and then the pH value is adjusted to 7.5~12 to obtain a gel; wherein the temperature of the first heating treatment is 10~30℃ higher than the temperature of the hydrolysis reaction, and the temperature of the hydrolysis reaction is 40~90℃. Aluminum-doped quartz sand is obtained by sequentially drying, calcining, and a second heating treatment on the gel. The temperature of the second heating treatment is 300-600°C higher than that of the calcining treatment. The temperature of the calcining treatment is 600-1000°C, and the duration of the second heating treatment is 3-20 hours. The calcining treatment is carried out in an oxygen-containing atmosphere, and the second heating treatment is carried out under vacuum conditions. The silicon source includes at least one of ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, pentyl orthosilicate, isopropyl orthosilicate, isobutyl orthosilicate, isoamyl orthosilicate, dimethyl orthosilicate, diethyl orthosilicate, and diisopropyl orthosilicate.

2. The preparation method according to claim 1, characterized in that, The impurity removal process is selected from one of the following methods: ion exchange, extraction, and ultrafiltration.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the acidic catalyst to water is (0.1~0.5):1; and / or, The molar ratio of the silicon source to water is 1:(4~15).

4. The preparation method according to claim 1, characterized in that, The drying process is carried out at a temperature of 100~300℃ for 1~12 hours.

5. The preparation method according to claim 1, characterized in that, The roasting process takes 5 to 40 hours.

6. The preparation method according to claim 1, characterized in that, The pH value is adjusted to 7.5-12 by adding an alkaline substance at a rate of 2-15 mL / min.

7. The preparation method according to claim 1, characterized in that, The alumina solid content in the alumina sol is 8%~25%.

8. The preparation method according to claim 1, characterized in that, The acidic catalyst is an aqueous solution containing an acidic substance. Among them, acidic substances include at least one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, propionic acid, benzoic acid, and oxalic acid; The concentration of acidic substances in the aqueous solution is 0.1~2 mol / L.

9. An aluminum-doped quartz sand, characterized in that, It is prepared by the method of any one of claims 1-8.

10. The aluminum-doped quartz sand according to claim 9, characterized in that, In the aluminum-doped quartz sand, the mass content of aluminum is 3~30 ppm.

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