Submicron-sized silicon carbide and its production method

Abstract

This invention relates to the field of micronized powder processing technology, and more particularly to a submicron-sized silicon carbide and its production method. The method involves a first acid wash of silicon carbide slurry prepared from hydrofluoric acid and hydrochloric acid, or hydrofluoric acid, hydrochloric acid, and concentrated sulfuric acid; a second acid wash using concentrated sulfuric acid; and a final alkaline wash using tetramethylammonium hydroxide as a dispersant. This process achieves a purity of 99.85% for the purified submicron-sized silicon carbide, meeting the production requirement of ≥99.5%, with a loss of less than 5%. This effectively improves production efficiency and reduces production costs.

Description

Technical Field

[0001] This invention relates to the field of micronized powder processing technology, and in particular to a submicron-sized silicon carbide and its production method. Background Technology

[0002] Silicon carbide micro powder is a micro powder material composed of silicon carbide particles. It has excellent properties such as high hardness, high temperature resistance, oxidation resistance, and corrosion resistance. It is an important functional material and is widely used in high-temperature materials, ceramic materials, abrasives, and coatings.

[0003] In the prior art, Chinese invention patent application number 200910256512.3 discloses a special silicon carbide micro powder for pressureless sintered silicon carbide products and its production method, including a step of mixing and stirring silicon carbide with water at a weight ratio of 1:1.5-3, a grinding step, a purification step, a water washing and dehydration step, and a drying step to obtain a particle size D50 value of 0.3um-0.6um and a BET 8m. 2 / g-30m 2 / g, silicon carbide purity ≥98.5wt%, sintering temperature 2160-2200℃, sintering density 3.10±0.05g / m³ 3 Silicon carbide micro powder. The purification process includes acid and alkali washing of the separated silicon carbide micro powder. The acid and alkali washing can be performed using conventional methods, with excess acid such as sulfuric acid or hydrochloric acid used for acid washing, and sodium hydroxide or similar substances used for alkali washing. These acid and alkali washing processes can be repeated multiple times depending on production conditions. The document shows that after multiple acid and alkali washings, the purity of silicon carbide can reach 99%, which does not meet the current production requirement of a purity greater than 99.5%. Furthermore, the multiple acid and alkali washings of silicon carbide using the above method result in significant silicon carbide loss, reaching 10%, leading to low efficiency and high enterprise costs. Summary of the Invention

[0004] Based on this, the present invention provides a submicron-sized silicon carbide and its production method, which solves the technical problems in the prior art where the silicon carbide purification process cannot meet the requirement of silicon carbide purity greater than 99.5%, and where silicon carbide loss is large, production efficiency is low, and enterprise costs are high.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A method for producing submicron-sized silicon carbide includes a purification process, the purification process comprising the following steps:

[0007] S1. Dehydrate the ground silicon carbide slurry to obtain silicon carbide mud A;

[0008] S2. The silicon carbide sludge A is subjected to acid washing, soaking and deacidification with a first acid solution to obtain silicon carbide sludge B. The first acid solution is a mixed solution of hydrofluoric acid and hydrochloric acid or a mixed solution of hydrofluoric acid, hydrochloric acid and sulfuric acid.

[0009] S3. The silicon carbide sludge B is subjected to a second acid wash, soaking, and deacidification in a second acid solution to obtain silicon carbide sludge C, wherein the second acid solution is concentrated sulfuric acid;

[0010] S4. Rinse the silicon carbide sludge C with water, let it stand, and dehydrate to obtain silicon carbide sludge D;

[0011] S5. The silicon carbide sludge D is rinsed twice with a dispersant and water, allowed to stand, and dehydrated to obtain silicon carbide sludge E, wherein the dispersant is tetramethylammonium hydroxide;

[0012] S6. The silicon carbide sludge E is rinsed with water at least once, allowed to stand, dehydrated, and dried to obtain submicron-sized silicon carbide.

[0013] Preferably, in step S2, the mass ratio of the silicon carbide sludge A to the first acid solution is 1:(4-5).

[0014] Preferably, in the first acid solution, the mass ratio of hydrofluoric acid to hydrochloric acid solution is 1:(3-5).

[0015] Preferably, the mass ratio of hydrofluoric acid, hydrochloric acid and sulfuric acid solution in the first acid solution is 1:(1-2):(1-2).

[0016] Preferably, in step S4, the mass ratio of the silicon carbide slurry C to water is 1:(3-5).

[0017] Preferably, the amount of dispersant added is 0.2%-0.8% of the mass of the silicon carbide slurry.

[0018] Preferably, the process further includes a grinding process, which comprises the following steps:

[0019] R1. Silicon carbide powder and water are mixed, a pH adjuster is added to adjust the pH value to 9-12, then a dispersant is added and stirred to obtain a silicon carbide slurry; wherein, the pH adjuster is at least one of NaOH, KOH, and sodium alkoxide, and the dispersant is TMAH;

[0020] R2. Add silicon carbide grinding media and perform self-grinding cycle until the silicon carbide powder particle size reaches the process particle size.

[0021] Preferably, in step R1, the mass ratio of the pH adjuster to the dispersant is 1:1.

[0022] Preferably, in step R2, the particle size of the silicon carbide polishing media is 4mm-8mm.

[0023] A submicron-sized silicon carbide is prepared by the method described above for producing submicron-sized silicon carbide.

[0024] The technical solution adopted in this application can achieve the following beneficial effects:

[0025] This invention provides a method for producing submicron-sized silicon carbide. The method involves first-washing the silicon carbide slurry with a first acid solution prepared from hydrofluoric acid and hydrochloric acid, or hydrofluoric acid, hydrochloric acid, and concentrated sulfuric acid. A second acid wash is then performed using concentrated sulfuric acid as the second acid solution. Finally, an alkaline wash is performed using tetramethylammonium hydroxide as a dispersant. This process achieves a purity of 99.85% for the purified submicron-sized silicon carbide, meeting the production requirement of ≥99.5%. Furthermore, the loss of submicron-sized silicon carbide is less than 5%, effectively improving production efficiency and reducing production costs. Attached Figure Description

[0026] Figure 1 Flowchart of the submicron-scale silicon carbide purification method. Detailed Implementation

[0027] To facilitate understanding of this application, a more comprehensive description will be provided below with reference to relevant experimental examples. Preferred embodiments of this application are shown in the experimental examples. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and comprehensive understanding of the disclosure of this application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] A method for producing submicron-sized silicon carbide includes a purification process, the purification process comprising the following steps:

[0030] S1. Dehydrate the ground silicon carbide slurry to obtain silicon carbide mud A;

[0031] S2. The silicon carbide sludge A is subjected to acid washing, soaking and deacidification with a first acid solution to obtain silicon carbide sludge B. The first acid solution is a mixed solution of hydrofluoric acid and hydrochloric acid or a mixed solution of hydrofluoric acid, hydrochloric acid and sulfuric acid.

[0032] S3. The silicon carbide sludge B is subjected to a second acid wash, soaking, and deacidification in a second acid solution to obtain silicon carbide sludge C, wherein the second acid solution is concentrated sulfuric acid;

[0033] S4. Rinse the silicon carbide sludge C with water, let it stand, and dehydrate to obtain silicon carbide sludge D;

[0034] S5. The silicon carbide sludge D is rinsed twice with a dispersant and water, allowed to stand, and dehydrated to obtain silicon carbide sludge E, wherein the dispersant is tetramethylammonium hydroxide;

[0035] S6. The silicon carbide sludge E is rinsed with water at least once, allowed to stand, dehydrated, and dried to obtain submicron-sized silicon carbide.

[0036] Specifically, the ground silicon carbide slurry is dehydrated. The dehydration method can employ centrifugation or filter press to separate the solid and liquid components. This invention preferably uses centrifugation to remove excess water, obtaining silicon carbide slurry A. Simultaneously, the dehydrated water can be recycled, saving enterprise costs. The moisture content of silicon carbide slurry A is approximately 35%, and the particle size of the silicon carbide slurry is 0.5µm-0.7µm.

[0037] The silicon carbide sludge A is subjected to acid washing, stirring, soaking, and deacidification with a first acid solution to obtain silicon carbide sludge B. The mass ratio of silicon carbide sludge B to the first acid solution is 1:(4-5). The first acid solution is a mixed solution of hydrofluoric acid and hydrochloric acid with a mass ratio of 1:(3-5), or a mixed solution of hydrofluoric acid, hydrochloric acid, and concentrated sulfuric acid with a mass ratio of 1:(1-2):(1-2). The stirring speed is 60r / min-80r / min. To accelerate the reaction, the temperature can be increased to 70℃-90℃. The stirring and soaking time ratio is 1:(2-3), and the total reaction time is 1-2 days. Centrifuge is preferred for deacidification, and the separated acid solution can be recycled.

[0038] The silicon carbide slurry B is subjected to a second acid wash, wherein the second acid is 98% concentrated sulfuric acid. The silicon carbide slurry B is added to the concentrated sulfuric acid and soaked and stirred for 6-12 hours, with a stirring-to-soaking time ratio of 2:4. The heating temperature is 30℃-50℃. Then, the slurry is deacidified using a centrifuge to obtain silicon carbide slurry C.

[0039] Silicon carbide sludge C and water are mixed at a ratio of 1:(3-5) and stirred at a speed of 30r / min-80r / min and a heating temperature of 20℃-40℃ for 3h-6h. After stirring, the mixture is allowed to stand for 10h-18h. The upper aqueous solution is then drained and water-solid separation is performed using a centrifuge or filter press to obtain silicon carbide sludge D.

[0040] The silicon carbide slurry D is rinsed twice with a dispersant and water. The dispersant is tetramethylammonium hydroxide, and the amount of the dispersant added is 0.2%-0.8% of the mass of the silicon carbide slurry. The mixture is stirred at a speed of 30-80 r / min and a heating temperature of 20-40℃ for 3-6 hours, then allowed to stand for 10-18 hours. Finally, solid-liquid separation is performed using a centrifuge to obtain silicon carbide slurry E.

[0041] The silicon carbide slurry E is rinsed with water at least once, stirred at a speed of 30 r / min-80 r / min, heated at a temperature of 20℃-40℃, stirred for 3h-6h, and then allowed to stand for 10h-18h. It is preferred to use a centrifuge for solid-liquid separation and then dry at a temperature of 70℃-130℃ until the moisture content of silicon carbide reaches below 0.2%, thus obtaining submicron-sized silicon carbide.

[0042] It should be noted that: the purpose of adding excess hydrofluoric acid and hydrochloric acid to the silicon carbide sludge is to remove metal oxides, elemental compounds, and silicon oxides from the silicon carbide; the purpose of adding concentrated sulfuric acid is to remove free carbon from the silicon carbide. The recovered acid solution can be recycled and reused until the concentration does not meet the requirements; the number of acid washing, rinsing, and alkali washing cycles can be freely determined according to the actual situation and is not limited to the above embodiments; solid-liquid separation can be achieved by various methods such as sieving, centrifugation, and filter press. Different filtration methods may result in different losses of silicon carbide. This invention preferably uses a centrifuge for solid-liquid separation; the concentrations of the above hydrofluoric acid, hydrochloric acid, and concentrated sulfuric acid are 49%, 33%, and 98%, respectively, and all can be purchased on the market.

[0043] The following specific experimental examples further illustrate the submicron-level silicon carbide purification process steps and their beneficial effects of the present invention.

[0044] Comparative Example 1

[0045] 800 kg of silicon carbide raw material (D50 = 6.7 μm - 14 μm) was ground to obtain silicon carbide slurry with a particle size of 0.5 μm - 0.7 μm. The slurry was then dehydrated using a filter press to obtain silicon carbide mud with a moisture content of about 35%.

[0046] Sulfuric acid was added to the separated silicon carbide sludge, and the mixture was stirred and soaked to separate the solid and liquid. The stirring speed was 70 r / min, the stirring time was 10 h, and the soaking time was 12 h. The solid-liquid ratio was 1:5.

[0047] The silicon carbide sludge separated from sulfuric acid is added to sodium hydroxide and stirred and soaked to separate the solid and liquid components. The solid-liquid ratio is 1:5.

[0048] The silicon carbide sludge separated from sodium hydroxide was washed with deionized water, the pH was adjusted to 5-6, and then dried at 140℃ for 28 hours.

[0049] The measured amount of silicon carbide micro powder was 719 kg, the purity of silicon carbide was 99.1%, and the particle size of silicon carbide was 0.5 μm-0.7 μm. The calculated silicon carbide loss was 10.13%.

[0050] Comparative Example 2

[0051] Keeping other conditions unchanged in Comparative Example 1, repeat the purification steps of silicon carbide acid washing, alkali washing, and water washing three times.

[0052] The measured amount of silicon carbide micro powder was 705 kg, the purity of silicon carbide was 99.1%, and the particle size of silicon carbide was 0.5 μm-0.7 μm. The calculated silicon carbide loss was 11.88%.

[0053] As can be seen from Comparative Examples 1 and 2, the silicon carbide obtained in Comparative Example 1 has a low purity, which does not reach the purity of more than 99.5% required by the enterprise. Therefore, Comparative Example 2 was used to purify the silicon carbide in Comparative Example 1 by repeating the acid washing, alkali washing and water washing three times. The results showed no essential change. Not only did it not improve the purity of silicon carbide, but it also increased the loss of silicon carbide. That is, simply increasing the number of acid washing, alkali washing and water washing of silicon carbide cannot improve the purity of silicon carbide, and may also cause more loss of silicon carbide. Therefore, the silicon carbide purification method needs to be further adjusted.

[0054] Experiment 1 investigates the effect of pickling media on silicon carbide purification.

[0055] 800 kg of silicon carbide raw material was ground to obtain silicon carbide slurry with a particle size of 0.5 μm-0.7 μm. The slurry was then put into a centrifuge for dehydration to obtain silicon carbide mud.

[0056] Silicon carbide sludge was mixed with the first acid solution at a mass ratio of 1:5, heated to 80℃, stirred at 70 r / min for 12 hours, and soaked for 24 hours. Then, a first solid-liquid separation was performed using a centrifuge, and the separated acid solution was recycled back to the acid tank. The first acid solution consisted of hydrochloric acid, hydrofluoric acid, concentrated sulfuric acid, a mixed solution of hydrofluoric acid and hydrochloric acid at a mass ratio of 1:4, a mixed solution of hydrofluoric acid and concentrated sulfuric acid at a mass ratio of 1:4, and a mixed solution of hydrofluoric acid, hydrochloric acid, and concentrated sulfuric acid at a mass ratio of 1:2:2, as shown in Table 1.

[0057] The mud separated after the first acid washing is added to the second acid solution, stirred for 3 hours, soaked for 6 hours, and heated to 40°C. The second acid solution is 98% concentrated sulfuric acid. A second solid-liquid separation is then performed, and the separated acid solution is recycled back to the concentrated sulfuric acid tank.

[0058] The silicon carbide mud separated in the second pickling process was mixed with deionized water at a mass ratio of 1:4. The mixture was stirred at a speed of 60 r / min and heated at 30℃ for 5 hours. After standing for 14 hours, the upper aqueous solution was drained, and then the solid and liquid were separated by centrifugation.

[0059] Before the second rinsing, the silicon carbide mud separated in the first rinsing is added to 0.5% sodium hydroxide by mass of the silicon carbide slurry, followed by deionized water. The stirring speed is 60 r / min, the heating temperature is 30℃, and the stirring is carried out for 5 hours. After standing for 14 hours, the upper aqueous solution is drained, and the second solid-liquid separation is carried out.

[0060] The silicon carbide mud separated in the second rinsing was further mixed with deionized water, stirred at 60 r / min, heated at 30 ℃, stirred for 5 h, and then allowed to stand for 14 h to separate the solid and liquid.

[0061] The silicon carbide sludge separated in the third rinsing is dried at 100°C until the moisture content of the silicon carbide reaches below 0.2%, thus obtaining submicron-sized silicon carbide.

[0062] Experiment Example 2 investigates the effect of alkaline washing media on silicon carbide purification.

[0063] Keeping all other conditions of Experiment 1 unchanged, the sodium hydroxide in the second rinsing step was replaced with the dispersant tetramethylammonium hydroxide, as shown in Table 1.

[0064] Table 1 Material Usage Table

[0065]

[0066] Table 2. Silicon Carbide Purity and Loss Table

[0067]

[0068]

[0069] As shown in the table above, adding a purification step in Comparative Example 2 did not improve the purity of silicon carbide and increased its loss. Therefore, in Experiment 1, two acid washes were used, and the effects of different first acid solutions on silicon carbide purification were explored. The experimental data in Table 2 show that the two acid washes had little effect on silicon carbide purification, but the loss was significantly reduced compared to Comparative Examples 1 and 2. Experiment 2 kept other conditions unchanged in Experiment 1 and explored the effect of alkaline washing medium on silicon carbide purification by replacing sodium hydroxide with tetramethylammonium hydroxide. The experimental results showed that when the first acid solution was a mixture of hydrofluoric acid and hydrochloric acid, or a mixture of hydrofluoric acid, hydrochloric acid, and concentrated sulfuric acid, and the second rinsing alkaline solution was tetramethylammonium hydroxide, the purity of silicon carbide was significantly improved to 99.86%, and the loss of silicon carbide was less than 5%, showing a significant synergistic effect. This is the optimal experimental example of the present invention. After multiple purification experiments, samples 1-6 were taken and tested as shown in the table below.

[0070] Table 3. Sampling and testing of silicon carbide content after purification in the optimal experimental example 2.

[0071] SiC TiO2 Al2O3 Fe2O3 MgO CaO Na2O SiO2 K2O Sample 1 99.83 0.02 0.08 0 0.01 0 0 0 0 Sample 2 99.85 0 0.09 0 0 0 0 0 0 Sample 3 99.80 0.04 0.09 0 0.01 0.01 0 0 0 Sample 4 99.87 0.04 0.03 0.01 0 0 0 0 0 Sample 5 99.85 0.03 0.02 0 0 0 0 0 0 Sample 6 99.86 0.05 0.03 0.01 0.01 0 0 0 0

[0072] As shown in Table 3, after multiple experiments, the purity of silicon carbide can be maintained at 99.80%-99.87% using the purification method of the present invention, proving that the method of the present invention can ensure the stability and repeatability of the silicon carbide purification process.

[0073] Furthermore, to improve grinding efficiency and shorten grinding time, this invention also provides a grinding method for submicron-sized silicon carbide micropowder, which is further illustrated below through specific experimental examples.

[0074] A method for grinding submicron-sized silicon carbide powder includes the following steps:

[0075] In some specific embodiments, the mixed water is prepared by the following method: Silicon carbide raw material and deionized water at a mass ratio of 1:(3-5) are added to a mixing tank and stirred for 0.3-1 hour. A pH adjuster is added at room temperature (25°C). The silicon carbide raw material is #800-#2000 silicon carbide, preferably with a D50 particle size of 6.7-14 μm. The pH adjuster is added first and stirred for 0.5-1 hour, then the ionic dispersant tetramethylammonium hydroxide (TMAH) is added, and stirring continues for another 0.5-1 hour to obtain a silicon carbide slurry with a solid content of 30%.

[0076] In one embodiment, the pH adjuster is a NaOH solution.

[0077] In one embodiment, the pH adjuster is a KOH solution.

[0078] In one embodiment, the pH adjuster is a sodium alkoxide solution.

[0079] In one embodiment, the pH adjuster is a mixture of NaOH and KOH, wherein the mass ratio of NaOH to KOH is 1:1.

[0080] In one embodiment, the mass ratio of the pH adjuster to the dispersant is 1:1. For example: when the pH adjuster is a NaOH solution and the dispersant is TMHA, the ratio of the amounts added is 1:1; when the pH adjuster is a KOH solution and the dispersant is TMHA, the ratio of the amounts added is 1:1; when the pH adjuster is a mixed solution of NaOH and KOH and the dispersant is TMHA, the ratio of the amounts of NaOH and KOH added to the mixed solution is 1:1, and the amount of TMHA added is 2 parts, thus maintaining the mass ratio of the pH adjuster to the dispersant at 1:1.

[0081] It should be noted that the original silicon carbide raw material has a pH of around 5.6 after dissolving in deionized water, indicating acidity. Under acidic conditions, the ground silicon carbide powder is prone to agglomeration. Therefore, NaOH, KOH, or a mixture of KOH and NaOH is added to adjust the pH of the slurry. After the alkaline solution is completely dissolved in the slurry, tetramethylammonium hydroxide, an ionic dispersant, is added to improve the dispersibility of the silicon carbide slurry itself, which is beneficial for the grinding of silicon carbide micro powder. The pH adjuster can also be sodium alkoxide.

[0082] In some specific embodiments, submicron-sized silicon carbide micropowder is prepared by self-grinding silicon carbide. The silicon carbide slurry is poured into a sand mill at a speed of 500 r / min-1200 r / min. After the first grinding for 12 hours, silicon carbide grinding media with a particle size of 1 mm-8 mm is added. The amount of grinding media added is 1%-10% of the silicon carbide raw material. Grinding continues, and the particle size at the bottom of the sand mill is checked every 12 hours. When the maximum particle size at the bottom of the sand mill is less than 1 mm-3 mm, 1%-10% silicon carbide grinding media is added to the sand mill again. The silicon carbide media with a diameter of 1 mm-10 mm is added, and grinding continues for 72 hours-144 hours until the median particle size of the silicon carbide powder reaches 0.5 μm-0.7 μm.

[0083] The mill can be any one of a vertical multi-disc mill, a horizontal mill, or a ball mill.

[0084] It should be noted that: firstly, the traditional grinding process uses sintered silicon carbide ceramic balls with a diameter between 1mm and 5mm, but silicon carbide ceramic balls are expensive, about 10 times the price of silicon carbide media sand; secondly, the grinding time will vary depending on the grinding machine used in actual work; thirdly, the water temperature is maintained at 30℃-40℃ during the grinding process; and fourthly, the median particle size of silicon carbide is measured using a BT-9300ST Dandong Better Laser Particle Size Analyzer.

[0085] Comparative Example 3

[0086] A method for grinding submicron-sized silicon carbide powder includes the following steps:

[0087] 800 kg of silicon carbide raw material and deionized water were added to a feed tank at a mass ratio of 1:4 and stirred for 0.5 h. The pH value was measured to be 5.6. The feed water was then poured into a sand mill and ground at a speed of 800 r / min. After grinding for 12 h, silicon carbide grinding media with a particle size of 3 mm was added. The particle size at the bottom of the sand mill was checked every 12 h. When the particle size at the bottom of the sand mill was less than 1 mm-3 mm, grinding media was added again. This process continued until the median particle size of the silicon carbide powder reached 0.5 μm-0.7 μm. The total grinding time was 150 ± 2 h.

[0088] As can be seen from the above comparative examples, without the addition of a pH adjuster, the pH value of the silicon carbide slurry is 5.6, resulting in a longer grinding time and severely impacting the company's production efficiency.

[0089] Experiment Example 3 investigated the effect of different pH values ​​on grinding efficiency when using NaOH to adjust the pH.

[0090] A method for grinding submicron-sized silicon carbide powder includes the following steps: 800 kg of silicon carbide raw material and deionized water are added to a feed tank at a mass ratio of 1:4 and stirred for 0.5 h. NaOH, a pH adjuster, is added to adjust the pH of the silicon carbide slurry to 7, and the mixture is stirred for 1 h to obtain a silicon carbide slurry. The silicon carbide slurry is then poured into a sand mill and ground at a speed of 800 r / min for 12 h. Silicon carbide grinding media with a particle size of 3 mm is then added. The particle size at the bottom of the sand mill is checked every 12 h. When the particle size at the bottom of the sand mill is less than 1 mm-3 mm, grinding media is added again. This process continues until the median particle size of the silicon carbide powder reaches 0.5 μm-0.7 μm. The total grinding time is 148 ± 2 h, and the total amount of silicon carbide media added is 50 ± 5 kg.

[0091] Using the above experimental examples, when the pH value of the silicon carbide slurry was adjusted to 8, 9, 10, 11 and 12, the corresponding self-grinding cycle times of the silicon carbide powder were statistically obtained to be 147±2h, 145±2h, 138±2h, 136±2h and 135±2h, respectively.

[0092] Experiment 4 investigated the effect of different pH values ​​on grinding efficiency when using KOH to adjust the pH.

[0093] Keeping other conditions unchanged in Experiment 3 above, when the pH adjuster is KOH, the pH values ​​of the silicon carbide slurry were adjusted to 7, 8, 9, 10, 11 and 12 respectively. The corresponding self-grinding cycle times of the silicon carbide powder were obtained as 148±2h, 148±2h, 145±2h, 139±2h, 136±2h and 135±2h respectively.

[0094] Experimental Example 5 investigates the effect of different pH values ​​on grinding efficiency when using TMAH to adjust the pH value.

[0095] Keeping other conditions unchanged in Experiment 3 above, without adding pH adjuster, only adding dispersant TMAH, and adjusting the pH value of silicon carbide slurry to 7, 8, 9, 10, 11, and 12 respectively, the corresponding self-grinding cycle times of the silicon carbide powder were statistically obtained as 147±2h, 144±2h, 143±2h, 127±2h, 128±2h, and 129±2h respectively.

[0096] Experimental Example 6 investigates the effect of different pH values ​​on grinding efficiency when using a mixture of NaOH and KOH to adjust the pH.

[0097] Keeping other conditions unchanged in Experiment Example 3 above, the pH adjuster was a mixture of NaOH and KOH, with a mass ratio of NaOH to KOH of 1:1. When the pH value of the silicon carbide slurry was adjusted to 7, 8, 9, 10, 11, and 12, the corresponding self-grinding cycle times of the silicon carbide powder were statistically obtained as 148±2h, 147±2h, 144±2h, 135±2h, 133±2h, and 133±2h, respectively.

[0098] Experimental Example 7 investigated the effect of different pH values ​​on grinding efficiency when NaOH was used to adjust the pH value and then the dispersant TMAH was added.

[0099] Keeping other conditions unchanged in Experiment 3 above, dispersant TMAH was added, and the ratio of NaOH to TMAH added was 1:1. When the pH values ​​of the silicon carbide slurry were 7, 8, 9, 10, 11, and 12, the corresponding self-grinding cycle times of the silicon carbide powder were statistically obtained as 146±2h, 145±2h, 142±2h, 125±2h, 125±2h, and 127±2h.

[0100] Experimental Example 8 investigated the effect of different pH values ​​on grinding efficiency when KOH was used to adjust the pH value and then the dispersant TMAH was added.

[0101] Keeping other conditions unchanged in Experiment Example 4 above, dispersant TMAH was added, and the ratio of KOH to TMAH added was 1:1. When the pH values ​​of the silicon carbide slurry were 7, 8, 9, 10, 11, and 12, the corresponding self-grinding cycle times of the silicon carbide powder were statistically obtained as 146±2h, 145±2h, 142±2h, 125±2h, 126±2h, and 127±2h, respectively.

[0102] Experimental Example 9 investigated the effect of different pH values ​​on grinding efficiency when NaOH and KOH were used to adjust the pH value before adding the dispersant TMAH.

[0103] Keeping other conditions unchanged in Experiment Example 6 above, dispersant TMAH was added. The ratio of NaOH, KOH and TMAH added was 1:1:2. When the pH values ​​of the silicon carbide slurry were 7, 8, 9, 10, 11 and 12, the corresponding self-grinding cycle times of the silicon carbide powder were statistically obtained as 145±2h, 142±2h, 138±2h, 120±2h, 121±2h and 123±2h, respectively.

[0104] Table 4 Grinding time at different pH values

[0105]

[0106] As shown in Table 4, firstly, under the condition of keeping the pH value constant, longitudinal analysis shows that in Experiments 3-6, when the pH adjuster is NaOH, KOH, TMAH, and a mixed solution of NaOH and KOH, the grinding efficiency of the NaOH, KOH, and mixed solution of NaOH and KOH varies but is not significantly different; in Experiments 7-8, the grinding efficiency of adding dispersant TMAH is slightly higher than that of Experiments 3-6; in Experiment 9, when the pH adjuster is a mixed solution of NaOH, KOH and TMAH, the grinding efficiency is significantly better than that of Experiments 3-8, except when the pH value is 7.

[0107] Second, with the pH adjuster remaining constant, a cross-sectional analysis was conducted. In Experiments 3-9, the grinding efficiency gradually increased as the pH value increased from 7 to 12. Among them, the highest grinding efficiency in Experiments 3-6 was at pH 12, with an increase of about 10.1%. In Experiments 7-9, the shortest grinding time was at pH 10, with the highest grinding efficiency. As the pH value continued to increase, the grinding efficiency decreased slightly. Experiments 7-9 were all results of adding the dispersant TMAH, and the grinding efficiency was significantly higher than that without the addition of the dispersant TMAH.

[0108] Third, in summary, when using NaOH, KOH, TMAH, or a mixture of NaOH and KOH as pH adjusters, the grinding time significantly decreased and the grinding efficiency increased by 6.8%-8.8% when the pH value was 10. When using NaOH and KOH as pH adjusters and adding the dispersant TMAH, the grinding efficiency was significantly higher than in Experiments 3-6 when the pH value was 10-12. When using a mixture of NaOH and KOH as pH adjusters and adding the dispersant TMAH, the silicon carbide grinding efficiency significantly increased at pH 9, reaching the same grinding time as in Experiments 3-6 at pH 12. Compared to Comparative Example 3, the grinding efficiency increased by 8%. Especially at pH 10, the silicon carbide grinding time decreased to approximately 120 hours, representing an 18.9% increase in grinding efficiency compared to other experimental examples and a 20% increase compared to Comparative Example 3. The experiments demonstrate that adding alkaline solutions can significantly increase grinding time, which is beneficial for reducing enterprise costs.

[0109] It should be noted that, according to the data, although TMHA is an alkaline solution, it mainly plays a dispersing role in this invention. Especially in an alkaline environment, TMHA fully exerts its dispersing effect, which enables the silicon carbide slurry to be fully ground, thereby improving the grinding efficiency. Therefore, the improvement in the grinding efficiency of silicon carbide slurry is the result of the synergistic effect of the pH adjuster and the dispersant.

[0110] Experiment 10 investigates the effect of silicon carbide abrasive media of different particle sizes on grinding time.

[0111] Using the optimal experimental example from Experimental Example 9 above, with a pH adjuster of a mixture of NaOH and KOH and a dispersant of a TMAH solution, and with the pH value at 10, while keeping other conditions unchanged from Experimental Example 7 above, the effect of silicon carbide grinding media with different particle sizes on grinding time was studied.

[0112] In one embodiment, when the grinding media particle size is 1 mm and the total grinding media loading is 50±5 kg and 70±5 kg respectively, the corresponding self-grinding cycle time of the process silicon carbide powder is statistically obtained as 144±7 h and 130±7 h.

[0113] In one embodiment, when the grinding media particle size is 2 mm and the total grinding media loading is 50±5 kg and 70±5 kg respectively, the corresponding self-grinding cycle time of the process silicon carbide powder is statistically obtained as 135±6 and 125±6 h.

[0114] In one embodiment, when the grinding media particle size is 3mm and the total grinding media loading is 50±5kg and 60±5kg respectively, the corresponding self-grinding cycle time of the process silicon carbide powder is statistically obtained as 120±5h and 114±5h.

[0115] In one embodiment, when the grinding media particle size is 4 mm and the total grinding media loading is 50±5 kg and 60±5 kg respectively, the corresponding self-grinding cycle time of the process silicon carbide powder is statistically obtained as 112±5 h and 102±5 h.

[0116] In one embodiment, when the grinding media particle size is 5 mm and the total grinding media loading is 40±5 kg and 50±5 kg respectively, the corresponding self-grinding cycle time for obtaining process silicon carbide powder is 103±5 h and 100±5 h respectively.

[0117] In one embodiment, when the grinding media particle size is 6 mm and the total grinding media loading is 40±5 kg and 50±5 kg respectively, the corresponding self-grinding cycle time of the process silicon carbide powder is statistically obtained as 96±5 and 92±4 h.

[0118] In one embodiment, when the grinding media particle size is 7 mm and the total grinding media loading is 50±5 kg and 60±5 kg respectively, the corresponding self-grinding cycle time of the process silicon carbide powder is statistically obtained as 110±5 and 112±5 h.

[0119] In one embodiment, when the grinding media particle size is 8 mm and the total grinding media loading is 50±5 kg and 60±5 kg respectively, the corresponding self-grinding cycle time of the process silicon carbide powder is statistically obtained as 118±5 and 116±5 h.

[0120] Table 5. Effect of media with different particle sizes on grinding efficiency in Experiment 10

[0121]

[0122]

[0123] Table 5 shows that, with the same grinding media particle size, the more grinding media added, the less grinding time is required. Data from Experiment 10 shows that when the grinding media particle size is 1-6 mm, the larger the particle size, the less grinding time and the higher the efficiency. When the grinding media particle size is greater than 6 mm, the larger the particle size, the longer the grinding time and the lower the grinding efficiency. The highest grinding efficiency is achieved when the grinding media particle size is 6 mm and the total grinding media loading is 50±5 kg, with a grinding time of 92±4 minutes, which is 38.7% higher than that of Comparative Example 3.

[0124] Experiments have shown that: First, the total amount of grinding media should not be increased as much as possible; it should be added appropriately. If the total amount of grinding media is excessive, the grinding machine will run slowly, which will actually increase the grinding time. Second, in the self-grinding cycle of silicon carbide, a larger particle size of the grinding media does not necessarily result in a better grinding effect. The preferred grinding media particle size in this invention is 4-7 mm. Third, the number of self-grinding cycles varies depending on the grinding conditions. For example, with a grinding media particle size of 1 mm, the cycle base is 6 hours, the statistical grinding time is 144 hours, and the number of cycles is 24. With a grinding media particle size of 8 mm, the cycle base is 12 hours, the statistical grinding time is 116 hours, and the number of cycles is 9.6. The preferred cycle base in this invention is 12 hours.

[0125] In summary, by using the grinding and purification method for silicon carbide of this invention, the production efficiency of silicon carbide is significantly improved; and sampling tests show that the silicon carbide content can reach up to 99.87%, with few impurities, which meets the requirements of enterprises with high silicon carbide purity.

[0126] The above-described embodiments merely illustrate the device deployment method of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those skilled in the art, several adjustments and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for producing submicron-sized silicon carbide, characterized in that, The purification process includes the following steps: S1. Dehydrate the ground silicon carbide slurry to obtain silicon carbide mud A; S2. The silicon carbide sludge A is subjected to acid washing, soaking and deacidification with a first acid solution to obtain silicon carbide sludge B. The first acid solution is a mixed solution of hydrofluoric acid and hydrochloric acid or a mixed solution of hydrofluoric acid, hydrochloric acid and sulfuric acid. S3. The silicon carbide sludge B is subjected to a second acid wash, soaking, and deacidification in a second acid solution to obtain silicon carbide sludge C, wherein the second acid solution is concentrated sulfuric acid; S4. Rinse the silicon carbide sludge C with water, let it stand, and dehydrate to obtain silicon carbide sludge D; S5. The silicon carbide sludge D is rinsed twice with a dispersant and water, allowed to stand, and dehydrated to obtain silicon carbide sludge E, wherein the dispersant is tetramethylammonium hydroxide; S6. The silicon carbide sludge E is rinsed with water at least once, allowed to stand, dehydrated, and dried to obtain submicron-sized silicon carbide.

2. The method for producing submicron-sized silicon carbide according to claim 1, characterized in that, In step S2, the mass ratio of the silicon carbide sludge A to the first acid solution is 1:(4-5).

3. The method for producing submicron-sized silicon carbide according to claim 2, characterized in that, In the first acid solution, the mass ratio of hydrofluoric acid to hydrochloric acid solution is 1:(3-5).

4. The method for producing submicron-sized silicon carbide according to claim 2, characterized in that, In the first acid solution, the mass ratio of hydrofluoric acid, hydrochloric acid and sulfuric acid solution is 1:(1-2):(1-2).

5. The method for producing submicron-sized silicon carbide according to claim 1, characterized in that, In step S4, the mass ratio of silicon carbide sludge C to water is 1:(3-5).

6. The method for producing submicron-sized silicon carbide according to claim 1, characterized in that, The amount of dispersant added is 0.2%-0.8% of the mass of the silicon carbide slurry.

7. The method for producing submicron-sized silicon carbide according to claim 1, characterized in that, It also includes a grinding process, which comprises the following steps: R1. Silicon carbide powder and water are mixed, a pH adjuster is added to adjust the pH value to 9-12, then a dispersant is added and stirred to obtain a silicon carbide slurry; wherein, the pH adjuster is at least one of NaOH, KOH, and sodium alkoxide, and the dispersant is TMAH; R2. Add silicon carbide grinding media and perform self-grinding cycle until the silicon carbide powder particle size reaches the process particle size.

8. The method for producing submicron-sized silicon carbide according to claim 7, characterized in that, In step R1, the mass ratio of the pH adjuster to the dispersant is 1:

1.

9. The method for producing submicron-sized silicon carbide according to claim 7, characterized in that, In step R2, the silicon carbide grinding media has a particle size of 4 mm-8 mm.

Images