Submicron recrystallized silicon carbide powder surface chemical modification method

Abstract

The invention discloses a submicron recrystallized silicon carbide powder surface chemical modification method, which comprises the following steps: shaping and purifying silicon carbide powder to prepare silicon carbide powder for a process, then preparing a mixed modification liquid, mixing the silicon carbide powder for the process with deionized water and a pH regulator, regulating the pH value to be 5-7 to obtain silicon carbide slurry, and finally preparing the silicon carbide slurry for the process. Then, the prepared silicon carbide slurry is combined with a mixed modification solution, a chemical modification process is implemented, finally, modified recrystallized silicon carbide powder is obtained through drying and crushing steps, and the recrystallized silicon carbide powder subjected to modification treatment can be stably and uniformly dispersed in a liquid medium; the prepared slurry is low in viscosity (between 17 mPa.s and 20 mPa.s) and has good fluidity, the solid content of the slurry can reach 84%-89%, and the application performance of the silicon carbide powder is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of silicon carbide, and particularly to a method for surface chemical modification of sub-micron recrystallized silicon carbide powder. Background Art

[0002] Recrystallized silicon carbide ceramics not only inherit the characteristics of traditional silicon carbide ceramics, such as high strength and wear resistance, but also exhibit unique thermal shock resistance, high purity, high temperature oxidation resistance, and excellent mechanical strength. Therefore, they are widely used in many special working condition fields. For example: kiln furniture inside kilns, cantilever paddles in semiconductor diffusion furnaces, equipment and pipelines for corrosion resistance in the chemical industry, and high-temperature engine components and shields in the fields of aerospace and national defense. In addition, it also plays an important role in thermoelectric materials and sensor components of electronic devices.

[0003] Since the recrystallized silicon carbide ceramics use micron-sized ultrafine powders with extremely high sphericity, they have a large specific surface area and are prone to agglomeration in solutions. It is difficult for particles of different particle sizes to be uniformly dispersed, which in turn affects the solid content and rheological properties of the silicon carbide slurry. Therefore, surface modification of silicon carbide powder by physical or chemical means to improve its dispersibility and fluidity is an important way to achieve the preparation of high-solid-content and low-viscosity slurries, which is crucial for improving the overall performance of ultrafine silicon carbide powder slurries.

[0004] In the prior art for the modification of silicon carbide powder, the main methods used are pickling purification method, inorganic modification method, and organic modification method. And the physical modification method is also to modify by adding silicon carbide powder into water and carrying out pulverization and grinding. However, the above modification methods have little effect on improving the dispersibility and fluidity of silicon carbide powder. Summary of the Invention

[0005] Based on this, the present invention provides a method for surface chemical modification of sub-micron recrystallized silicon carbide powder, which solves the technical problem that the prior art has little effect on improving the dispersibility and fluidity of silicon carbide powder in the modification method.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A method for surface chemical modification of sub-micron recrystallized silicon carbide powder, comprising the following steps:

[0008] S1. Obtain high-sphericity silicon carbide powder after shaping;

[0009] S2. After alkali washing and acid washing the high-sphericity silicon carbide powder, obtain purified silicon carbide powder;

[0010] S3. Add deionized water and a pH regulator to the purified silicon carbide powder to obtain a silicon carbide slurry with a pH of 5 to 7;

[0011] S4. Mix a silane coupling agent, a dispersant, and deionized water, and obtain a mixed modification liquid after heating and stirring;

[0012] S5. Mix the silicon carbide slurry with the mixed modification liquid, and after stirring, precipitation, and extraction of the supernatant, the remaining material obtained is the modified silicon carbide slurry;

[0013] S6. Dry and crush the modified silicon carbide slurry to obtain modified recrystallized silicon carbide powder.

[0014] Preferably, in step S1, the particle size D50 of the high-spherical silicon carbide powder after shaping is 2.0 μm to 2.1 μm, and the particle size range is 0.3 μm to 9 μm.

[0015] Preferably, in step S4, the mass ratio of the silane coupling agent, the dispersant, and the deionized water is (1 to 5):(0.5 to 2):1.

[0016] Preferably, in step S4, the dispersant is any one of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate.

[0017] Preferably, in step S4, the mass ratio of the silane coupling agent, the dispersant, and the deionized water is (0.5 to 1):(0.5 to 1):2.

[0018] Preferably, in step S5, the mass ratio of the silicon carbide slurry to the mixed modification liquid is (300 to 320):(0.3 to 1).

[0019] Preferably, in step S3, the pH regulator is any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0020] Preferably, in step S1, the high-spherical silicon carbide powder after shaping is prepared by the following method:

[0021] S11. Take the raw material silicon carbide powder, mix ammonium polyacrylate and deionized water and stir to obtain a dispersion liquid, and introduce the dispersion liquid and the raw material silicon carbide into a sand mill for grinding to obtain a refined silicon carbide slurry;

[0022] S12. Dry and crush the refined silicon carbide slurry to obtain silicon carbide particles;

[0023] S13. Put the silicon carbide particles and silicon carbide ceramic balls into an ultrasonic grinding machine, and obtain the high-spherical silicon carbide powder after stirring and ultrasonic vibration grinding.

[0024] Preferably, in step S11, the mass ratio of the ammonium polyacrylate to the deionized water is (0.05 to 2):100.

[0025] Preferably, in step S13, the ultrasonic frequency of the ultrasonic grinder is 70 kHz to 80 kHz, and the ultrasonic time is 8 h to 10 h.

[0026] The technical solution adopted in this application can achieve the following beneficial effects:

[0027] This application discloses a method for surface chemical modification of submicron recrystallized silicon carbide powder. The method first shapes and purifies the silicon carbide powder to prepare silicon carbide powder for the process. Subsequently, a mixed modification liquid is prepared, and this process silicon carbide powder is mixed with deionized water and a pH regulator to adjust the silicon carbide slurry to a pH value of 5 to 7. Then, the prepared silicon carbide slurry is combined with the mixed modification liquid to implement the chemical modification process. Finally, through the steps of drying and crushing, the modified recrystallized silicon carbide powder is obtained. The recrystallized silicon carbide powder after the modification treatment can be stably and uniformly dispersed in the liquid medium. The prepared slurry not only has a low viscosity (between 17 and 20 mPa·s), but also has good fluidity, and its solid content can reach 84% to 89%, effectively improving the application performance of the silicon carbide powder. Description of the Drawings

[0028] Figure 1 It is a morphology diagram of the modified recrystallized silicon carbide powder. Detailed Embodiments

[0029] To facilitate the understanding of this application, the following will describe this application more comprehensively with reference to relevant experimental examples. The preferred embodiments of this application are given in the experimental examples. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of this application more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] A method for surface chemical modification of submicron recrystallized silicon carbide powder includes the following steps:

[0032] S1. Obtain high-spherical silicon carbide powder after shaping; among them, add 0.05 to 0.2 parts of ammonium polyacrylate to 100 parts of deionized water and stir for 30 min to obtain a dispersion liquid, then take 100 parts of raw material silicon carbide (D 50 with a particle size of 5.5 to 8.5 μm and a purity of ≥98%) and the dispersion liquid are introduced into a sand mill and ground for 12 hours to obtain a refined silicon carbide slurry. The refined silicon carbide slurry is dried and crushed to obtain silicon carbide particles (D 50 with a particle size of 2.5 to 3.5 μm); put the silicon carbide particles and silicon carbide ceramic balls with a diameter of 5 to 9 mm into an ultrasonic mill according to a mass ratio of 1:(2 to 4), with a stirring speed of 6 to 10 rad / min, an ultrasonic frequency of 60 to 80 kHz, and ultrasonic vibration milling for 8 to 10 h to obtain high-spherical silicon carbide powder. The particle size of the high-spherical silicon carbide powder D 50 is 2 to 2.1 μm, and the particle size range is 0.3 to 9 μm.

[0033] S2. After alkali washing and acid washing the high-spherical silicon carbide powder, obtain purified silicon carbide powder; among them, add the high-spherical silicon carbide powder to 15 to 20 parts of sodium hydroxide and 100 to 300 parts of deionized water to mix and prepare a high-spherical silicon carbide powder slurry. Heat the high-spherical silicon carbide powder slurry to a high temperature of 70 to 100 °C, stir at a high temperature for 12 to 24 h, with a stirring speed of 50 to 100 rad / min, then precipitate for 10 to 14 h, and use a high-pressure water pump to extract the supernatant, repeating 2 to 3 times to obtain the high-spherical silicon carbide powder after alkali washing; add 10 to 20 parts of hydrochloric acid and 4 to 10 parts of nitric acid to the high-spherical silicon carbide powder after alkali washing, then add 100 to 300 parts of deionized water, heat to a high temperature of 70 to 100 °C, stir for 24 h, with a stirring speed of 50 to 100 rad / min, precipitate for 10 to 14 h, and use a high-pressure water pump to extract the supernatant, repeating 6 to 8 times to obtain purified silicon carbide powder.

[0034] S3. Add deionized water and a pH regulator to the purified silicon carbide powder to obtain a silicon carbide slurry with a pH of 5 to 7; among them, add 200 parts of deionized water and a pH regulator to the purified silicon carbide powder, stir evenly to prepare a silicon carbide slurry with a pH of 5 to 7, where the pH regulator is preferably tetramethylammonium hydroxide.

[0035] S4. Mix the silane coupling agent, dispersant, and deionized water, heat and stir to obtain a mixed modification liquid; among them, mix 0.1 to 0.5 parts of the silane coupling agent, 0.05 to 0.2 parts of SDS dispersant, and 0.1 part of deionized water, heat and maintain the temperature at 40°C to 50°C, and stir at a speed of 15 min to 20 min to obtain a mixed modification liquid, where the dispersant is sodium dodecyl sulfate (SDS).

[0036] S5. Mix the silicon carbide slurry with the mixed modification liquid, stir and precipitate, and then extract the supernatant to obtain the modified silicon carbide slurry; among them, mix the silicon carbide slurry with the mixed modification liquid, continue to stir for 4 to 6 hours, precipitate for 24 hours, use a high-pressure water pump to extract the supernatant, and continue to stir for 1 hour to obtain the modified silicon carbide slurry.

[0037] S6. Dry and crush the modified silicon carbide slurry to obtain modified recrystallized silicon carbide powder; among them, put the silicon carbide slurry into an oven, maintain the temperature at 70°C to 90°C, dry for 48h to 50h, put the dried block material into a crusher for crushing to obtain modified recrystallized silicon carbide powder.

[0038] I. Explore the influence of different masses of ammonium polyacrylate on the shaping of silicon carbide

[0039] Experimental Example 1

[0040] Take 1000 g of raw material silicon carbide powder (D 50 with a particle size between 5.5 μm and 8.5 μm and a purity ≥ 98%) and 1000 g of deionized water and introduce them into a sand mill for grinding for 12 hours to obtain a refined silicon carbide slurry. The refined silicon carbide slurry is dried and crushed to obtain silicon carbide particles with a particle size range of 1.54 μm to 6.79 μm; the silicon carbide particles and silicon carbide ceramic balls with a diameter of 5 mm are put into an ultrasonic grinding machine according to a mass ratio of 1:3, with a stirring speed of 8 rad / min, an ultrasonic frequency of 60 kHz, and ultrasonic vibration grinding for 8 h. The parameters of the high-spherical silicon carbide powder are measured as shown in Table 1.

[0041] Experimental Example 2

[0042] Take 0.5 g of ammonium polyacrylate and add it to 1000 g of deionized water and stir for 30 min to obtain a dispersion liquid. Then, the raw material silicon carbide powder (D 50(with a purity of ≥98% in the range of 5.5 μm to 8.5 μm) and the dispersion liquid were introduced into a sand mill and ground for 12 hours to obtain a refined silicon carbide slurry. The refined silicon carbide slurry was dried and crushed to obtain silicon carbide particles with a particle size range of 1.54 μm to 6.79 μm; the silicon carbide particles and silicon carbide ceramic balls with a diameter of 5 mm were placed in an ultrasonic grinding machine according to a mass ratio of 1:3, with a stirring speed of 8 rad / min, an ultrasonic frequency of 60 kHz, and ultrasonic vibration grinding for 8 h. The parameters of the high-spherical silicon carbide powder were measured as shown in Table 2.

[0043] Experimental Example 3

[0044] Keeping other conditions in Experimental Example 2 unchanged, 0.5 g of ammonium polyacrylate was replaced with 1 g of ammonium polyacrylate.

[0045] Experimental Example 4

[0046] Keeping other conditions in Experimental Example 2 unchanged, 0.5 g of ammonium polyacrylate was replaced with 1.5 g of ammonium polyacrylate.

[0047] Experimental Example 5

[0048] Keeping other conditions in Experimental Example 2 unchanged, 0.5 g of ammonium polyacrylate was replaced with 2 g of ammonium polyacrylate.

[0049] Table 1 Table of changes in the mass of ammonium polyacrylate

[0050]

[0051]

[0052] Table 2 Table of the influence of different masses of ammonium polyacrylate on the shaping parameters of silicon carbide

[0053] Name Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[Particle size D 50 (μm)]]> 2.216 2.100 2.100 2.095 2.068 Particle size range (μm) 1.54-6.795 1-7.505 0.873-7.84 0.804-7.947 0.785-7.877 <![CDATA[Bulk density (g / cm 3 )]]> 0.76 0.75 0.76 0.79 0.78 <![CDATA[Tap density (g / cm 3 )]]> 1.04 1.10 1.10 1.13 1.13

[0054] As can be seen from Tables 1 - 2, in the case of no addition of ammonium polyacrylate, the prepared high-spherical silicon carbide powder has a particle size D 50 of 2.216 μm, a particle size range of 1.54 μm to 6.795 μm, and a tapped density of 1.04 g / cm 3 ; when the ammonium polyacrylate increases to 0.20%, the particle size D 50 is 2.068 μm, a particle size range of 0.785 μm to 7.877 μm, and a tapped density of 1.13 g / cm 3 , and the tapped densities of Experimental Example 4 and Experimental Example 5 are the same. To save resources, this application preferably uses 1.5 g of ammonium polyacrylate.

[0055] II. Exploration of the influence of using silicon carbide ceramic balls with different particle sizes on the shaping of silicon carbide

[0056] Experimental Example 6

[0057] Keeping the other conditions in Experimental Example 4 unchanged, replace the silicon carbide ceramic balls with a diameter of 5 mm with silicon carbide ceramic balls with a diameter of 7 mm.

[0058] Experimental Example 7

[0059] Keeping the other conditions in Experimental Example 4 unchanged, replace the silicon carbide ceramic balls with a diameter of 5 mm with silicon carbide ceramic balls with a diameter of 9 mm.

[0060] Table 3 Variation diameter table of silicon carbide ceramic balls

[0061] Name Example 6 Example 7 Ammonium polyacrylate 0.15 0.15 Diameter of silicon carbide ceramic balls / mm 7 9 Ultrasonic frequency / kHz 60 60 Ultrasonic time / h 8 8

[0062] Table 4 Influence table of silicon carbide ceramic balls with different particle sizes on silicon carbide shaping parameters

[0063] Name Example 6 Example 7 <![CDATA[Particle size D 50 (μm)]]> 2.090 2.094 Particle size range (μm) 0.75-7.87 0.591-7.989 Loose packing density (g / cm3) 0.79 0.76 Tap density (g / cm3) 1.14 1.13

[0064] As can be seen from Tables 3 - 4, under the same conditions, the grinding effect is better when using silicon carbide ceramic balls with a diameter of 7 mm. The high-spherical silicon carbide powder after grinding has a particle size D 50 of 2.090 μm, the particle size range is from 0.75 μm to 7.87 μm, and the tapped density is 1.14 g / cm 3 . Therefore, this application preferably uses silicon carbide ceramic balls with a diameter of 7 mm.

[0065] III. Explore the influence of different ultrasonic frequencies and ultrasonic times on silicon carbide shaping

[0066] Experimental Example 8

[0067] Keeping the other conditions in Experimental Example 6 unchanged, replace the ultrasonic frequency of 60 kHz with an ultrasonic frequency of 70 kHz.

[0068] Experimental Example 9

[0069] Keeping the other conditions in Experimental Example 6 unchanged, replace the ultrasonic frequency of 60 kHz with an ultrasonic frequency of 80 kHz.

[0070] Experimental Example 10

[0071] Keeping the other conditions in Experimental Example 9 unchanged, replace the ultrasonic vibration grinding for 8 h with ultrasonic vibration grinding for 9 h.

[0072] Experimental Example 11

[0073] Keeping the other conditions in Experimental Example 9 unchanged, replace the ultrasonic vibration grinding for 8 h with ultrasonic vibration grinding for 10 h.

[0074] Table 5 Variation table of ultrasonic frequency and ultrasonic time

[0075]

[0076]

[0077] Table 6 Influence Table of Different Ultrasonic Frequencies and Ultrasonic Times on the Shaping Parameters of Silicon Carbide

[0078] Name Example 8 Example 9 Example 10 Example 11 <![CDATA[Particle size D 50 (μm)]]> 2.056 2.058 2.049 2.051 Particle size range (μm) 0.489-8.73 0.406-8.812 0.321-8.97 0.347-8.79 <![CDATA[Bulk density (g / cm 3 )]]> 0.79 0.81 0.84 0.82 <![CDATA[Tap density (g / cm 3 )]]> 1.15 1.21 1.25 1.25

[0079] As can be seen from Tables 5 - 6, under the same conditions, when the ultrasonic frequency is 80 kHz, the tap densities at ultrasonic times of 9 h and 10 h are the same, both being 1.25 g / cm 3 , but the particle size of silicon carbide in Experiment 10, the particle size D 50 is 2.049 μm, and the particle size range is from 0.321 μm to 8.97 μm. Its process particle size is better than that of Experiment Example 11. Therefore, in this application, the preferred ultrasonic frequency is 80 kHz and the ultrasonic time is 9 h.

[0080] IV. Experiment Example 12 on Exploring the Influence of Different Masses of Silane Coupling Agent on the Parameters of Recrystallized Silicon Carbide

[0081] Use the high - spherical silicon carbide powder ground in Example 10, and perform alkali washing and acid washing on the high - spherical silicon carbide powder.

[0082] The acid - washing steps are as follows:

[0083] Mix the high - spherical silicon carbide powder ground in Example 10 with 150 g of sodium hydroxide with a concentration of 45% and 1500 g of deionized water to prepare a high - spherical silicon carbide powder slurry. Heat the high - spherical silicon carbide powder slurry to 80°C, stir at a high temperature for 24 h, with a stirring speed of 60 rad / min, then precipitate for 12 h, and use a high - pressure water pump to extract the supernatant. After repeating the above process 2 times, the acid - washed high - spherical silicon carbide powder is obtained.

[0084] The alkali - washing steps are as follows:

[0085] Add the acid - washed high - spherical silicon carbide powder to a mixture of 150 g of hydrochloric acid with a concentration of 38% and 50 g of nitric acid with a concentration of 37%, then add 1500 g of deionized water, heat to 80°C and stir at a high temperature for 24 hours, with a stirring speed of 60 rad / min, precipitate for 12 hours, and use a high - pressure water pump to extract the supernatant. After repeating the above process 7 times, the purified silicon carbide powder is obtained.

[0086] After completing the acid - washing and alkali - washing of the high - spherical silicon carbide powder, the steps for preparing the silicon carbide slurry and the mixed modification liquid are as follows:

[0087] Add 2000 g of deionized water and a pH regulator to the obtained purified silicon carbide powder, mix and stir evenly to prepare a silicon carbide slurry with a pH value of 6, where the pH regulator is tetramethylammonium hydroxide.

[0088] Mix 0.5 g of silane coupling agent, 0.5 g of SDS dispersant, and 1 g of deionized water, heat and maintain the temperature at 45 °C, and stir for 20 min to obtain a mixed modification solution.

[0089] Mix the silicon carbide slurry with the mixed modification solution, stir for 5 hours, precipitate for 24 hours, pump out the supernatant with a high-pressure water pump, and then stir the remaining material for 1 hour to obtain the modified silicon carbide slurry.

[0090] Put the silicon carbide slurry into an oven, maintain the temperature at 80 °C, dry for 50 hours, put the dried block material into a crusher for crushing to obtain modified recrystallized silicon carbide, and test the modified recrystallized silicon carbide to obtain the parameters as shown in the following table.

[0091] Experimental Example 13

[0092] Keep other conditions in Experimental Example 12 unchanged, and replace 0.5 g of silane coupling agent with 0.6 g of silane coupling agent.

[0093] Experimental Example 14

[0094] Keep other conditions in Experimental Example 12 unchanged, and replace 0.5 g of silane coupling agent with 1 g of silane coupling agent.

[0095] Experimental Example 15

[0096] Keep other conditions in Experimental Example 12 unchanged, and replace 0.5 g of silane coupling agent with 3 g of silane coupling agent.

[0097] Experimental Example 16

[0098] Keep other conditions in Experimental Example 12 unchanged, and replace 0.5 g of silane coupling agent with 5 g of silane coupling agent.

[0099] Table 7 Influence of Silane Coupling Agents with Different Masses on the Shaping Parameters of Silicon Carbide

[0100] Name Example 12 Example 13 Example 14 Example 15 Example 16 Silane coupling agent 0.5 0.6 1 3 5 SDS 0.5 0.5 0.5 0.5 0.5 pH value 6 6 6 6 6

[0101] Table 8 Influence of Different Silane Coupling Agents on the Parameters of Recrystallized Silicon Carbide

[0102] Name Example 12 Example 13 Example 14 Example 15 Example 16 <![CDATA[Specific surface area m 2 / g]]> 4.8 5 6.5 5.7 5.8 Conductivity us / cm 63 47 31 25 25 SiC content 99.37％ 99.33％ 99.40％ 99.70％ 99.70％ Fe (mg / kg) ≤169 ≤133 ≤128 ≤104 ≤107 <![CDATA[Fe2O3]]> ≤0.04％ ≤0.04％ ≤0.02％ ≤0.01％ ≤0.01％

[0103] V. Explore the Influence of Dispersants with Different Masses on the Parameters of Recrystallized Silicon Carbide

[0104] Experimental Example 17

[0105] Keep other conditions in Experimental Example 15 unchanged, and replace 0.5 g of SDS dispersant with 0 parts of SDS dispersant.

[0106] Experimental Example 18

[0107] Keeping other conditions in Experimental Example 15 unchanged, replace 0.5 g of SDS dispersant with 1.5 g of SDS dispersant.

[0108] Experimental Example 19

[0109] Keeping other conditions in Experimental Example 15 unchanged, replace 0.5 g of SDS dispersant with 2 g of SDS dispersant.

[0110] Experimental Example 20

[0111] Keeping other conditions in Experimental Example 15 unchanged, replace 0.5 g of SDS dispersant with 3 g of SDS dispersant.

[0112] VI. Experiment on the influence of pH regulators with different masses on the fluidity of recrystallized silicon carbide - Experimental Example 21

[0113] Keeping other conditions in Experimental Example 18 unchanged, add a pH regulator to adjust the pH value of the silicon carbide slurry to 8.

[0114] Experimental Example 22

[0115] Keeping other conditions in Experimental Example 18 unchanged, add a pH regulator to adjust the pH value of the silicon carbide slurry to 10.

[0116] Table 9 Influence of different ultrasonic frequencies and ultrasonic times on silicon carbide parameters

[0117] Name Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 Silane coupling agent 3 3 3 3 3 3 SDS 0 1.5 2 3 1.5 1.5 pH value 6 6 6 6 8 10

[0118] Table 10 Influence of different ultrasonic frequencies and ultrasonic times on silicon carbide parameters

[0119] Name Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 <![CDATA[Specific surface area m 2 / g]]> 3.9 5.5 5.8 5.9 5.5 5.5 Conductivity us / cm 35 33 27 27 15 15 SiC content 99.30％ 99.39％ 99.58％ 99.58％ 99.70％ 99.64％ Fe (mg / kg) ≤130 ≤105 ≤105 ≤105 ≤89 ≤101 <![CDATA[Fe2O3]]> ≤0.04％ ≤0.01％ ≤0.01％ ≤0.01％ ≤0.01％ ≤0.01％

[0120] According to the experimental data in Tables 7 - 10, when the addition amount of silane coupling agent is 0.30% and the addition amount of SDS is 0.15%, the impurity content of the prepared modified recrystallized silicon carbide is relatively low: the Fe content is lower than 89 mg / kg, the Fe2O3 content is lower than 0.01%, and at the same time, the conductivity of the modified recrystallized silicon carbide is also relatively low, only 15 μS / cm. It shows that the modified recrystallized silicon carbide has high purity and excellent electrical insulation performance.

[0121] VII. Detection of the fluidity of modified recrystallized silicon carbide

[0122] Experimental Example 23

[0123] The modified recrystallized silicon carbide prepared in Experimental Examples 12 to 22 was respectively detected by the following steps:

[0124] Mix the modified recrystallized silicon carbide with deionized water at a ratio of 1:2 and stir evenly at a stirring speed of 20 rad / min to obtain a modified recrystallized silicon carbide slurry. Use a viscometer to detect it, and the performance parameters of the modified recrystallized silicon carbide are measured as follows:

[0125] Table 11-1 Detection Parameters of Modified Recrystallized Silicon Carbide

[0126] Name Example 12 Example 13 Example 14 Example 15 Example 16 PH value 6 6 6 6 6 Viscosity (mpa·s) 52 56 23 20 21 Solid content (%) 77 78 84 85 83

[0127] Table 11-2 Detection Parameters of Modified Recrystallized Silicon Carbide

[0128] Name Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 PH value 6 6 6 6 6 6 Viscosity (mpa·s) 60 18 19 21 17 17 Solid content (%) 71 88 87 84 89 87

[0129] According to the data in Table 11, by mixing the modified recrystallized silicon carbide prepared in Experimental Examples 12 to 22 with deionized water, the parameters in the above table were tested and recorded. It can be seen from the measured viscosity and solid content of the modified recrystallized silicon carbide slurry that in Experimental Examples 18 to 22, the obtained modified recrystallized silicon carbide slurry exhibited a low viscosity below 20 mPa·s, and at the same time, the solid content was maintained between 84% and 90%. These results indicate that a high solid content can be achieved under low viscosity conditions, reflecting that the modified recrystallized silicon carbide has good dispersibility and excellent fluidity.

[0130] The above embodiments only express the layout mode of the equipment of this application. The description is relatively specific and detailed, but it cannot be understood as a limitation to the scope of the patented application. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several adjustments and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of the patent of this application should be subject to the appended claims.

Claims

1. A method for surface chemical modification of sub-micron recrystallized silicon carbide powder, characterized in that, It includes the following steps: S1. Obtain high-spherical silicon carbide powder after shaping; S2. After alkali washing and acid washing the high-spherical silicon carbide powder, obtain purified silicon carbide powder; S3. Add deionized water and a pH regulator to the purified silicon carbide powder to obtain a silicon carbide slurry with a pH of 5 to 7; S4. Mix a silane coupling agent, a dispersant, and deionized water, and obtain a mixed modification liquid after heating and stirring; S5. Mix the silicon carbide slurry with the mixed modification liquid, and after stirring, precipitation, and extracting the supernatant, the remaining material obtained is the modified silicon carbide slurry; S6. Dry and crush the modified silicon carbide slurry to obtain modified recrystallized silicon carbide powder.

2. The surface chemical modification method of submicron recrystallized silicon carbide powder according to claim 1, wherein, In step S1, the particle size D of the shaped high-spherical silicon carbide powder 50 is between 2.0 µm and 2.1 µm, and the particle size range is from 0.3 µm to 9 µm.

3. The surface chemical modification method of submicron recrystallized silicon carbide powder according to claim 1, characterized in that, In step S4, the mass ratio of the silane coupling agent, the dispersant, and the deionized water is (1 to 5):(0.5 to 2):

1.

4. The surface chemical modification method of sub-micron recrystallized silicon carbide powder according to claim 1, characterized in that In step S4, the dispersant is any one of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate.

5. The surface chemical modification method of submicron recrystallized silicon carbide powder according to claim 1, characterized in that, In step S4, the mass ratio of the silane coupling agent, the dispersant, and the deionized water is (0.5 to 1):(0.5 to 1):

2.

6. The surface chemical modification method of the submicron recrystallized silicon carbide powder according to claim 1, characterized in that, In step S5, the mass ratio of the silicon carbide slurry to the mixed modification liquid is (300 to 320):(0.3 to 1).

7. The surface chemical modification method of the submicron recrystallized silicon carbide powder according to claim 1, characterized in that, In step S3, the pH regulator is any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

8. The surface chemical modification method of submicron recrystallized silicon carbide powder according to claim 1, characterized in that, In step S1, the high-spherical silicon carbide powder after shaping is prepared by the following method: S11. Take raw material silicon carbide powder, mix ammonium polyacrylate and deionized water and stir to obtain a dispersion liquid, and introduce the dispersion liquid and the raw material silicon carbide into a sand mill for grinding to obtain a refined silicon carbide slurry; S12. Dry and crush the refined silicon carbide slurry to obtain silicon carbide particles; S13. Put the silicon carbide particles and silicon carbide ceramic balls into an ultrasonic mill, and obtain the high-spherical silicon carbide powder after stirring and ultrasonic vibration grinding.

9. The surface chemical modification method of submicron recrystallized silicon carbide powder according to claim 8, wherein In step S11, the mass ratio of the ammonium polyacrylate to the deionized water is (0.05 to 2):

100.

10. The surface chemical modification method of submicron recrystallized silicon carbide powder according to claim 8, characterized in that, In step S13, the ultrasonic frequency of the ultrasonic mill is 70 kHz to 80 kHz, and the ultrasonic time is 8 h to 10 h.

Images