A method for preparing a multi-particle size silicon powder slurry

Abstract

The application discloses a slurry preparation method of multi-particle-size silicon powder slurry, relates to the technical field of silicon nitride ceramic sheets, and can customize particle size distribution, effectively improves the dilemma that low oxygen content and small particle size cannot be obtained at the same time in the existing silicon powder slurry preparation technology, and reduces the cost. In addition, the modified polyvinyl alcohol is introduced into acetaldehyde to generate an acetalization reaction, the crosslinking degree and water resistance of the silicon powder slurry are improved, the boric acid forms a boric acid ester bond with the hydroxyl group of the polyvinyl alcohol, the mechanical strength is improved, the boric acid ester bond inhibits the thermal motion of the molecular chain, and the thermal stability is improved. The modified boron nitride is added, a condensation reaction occurs between the silanol and the boron nitride, the interfacial bonding force is improved, and the ceramic wear rate is reduced; the amino group grafted on the surface forms a hydrogen bond with the hydroxyl group of the polyvinyl alcohol, the wear resistance and dispersibility are improved, the pores of the embedded Yb-MOF are enhanced, the mechanical interlocking is enhanced, and the peeling strength and thermal conductivity performance are greatly improved. The multi-particle-size silicon powder slurry is particularly suitable for the preparation of silicon nitride ceramic sheets.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon nitride ceramic sheet, and particularly to a method for preparing a silicon powder slurry with multiple particle sizes. BACKGROUND

[0002] Electronic ceramic materials, such as alumina, aluminum nitride, silicon nitride and silicon carbide, etc., usually include two main steps of green body forming and sintering in the manufacturing process. At present, the common green body forming methods include dry pressing, slip casting, tape casting and rolling film forming, etc., among which tape casting is widely adopted due to its simple operation and good process controllability. In the tape casting of silicon nitride green body, silicon sheet tape casting has certain advantages compared with silicon nitride powder tape casting, because silicon powder is not only low in price, but also easy to obtain in high purity, and its oxygen content is much lower than that of silicon nitride powder, which helps to improve the thermal conductivity of the final silicon nitride ceramic sheet.

[0003] The tape casting process mainly includes slurry preparation and subsequent optimization of process parameters. Among them, the preparation of slurry is the key link of the whole tape casting process. The tape casting slurry is usually composed of inorganic powder and organic carrier, among which the organic carrier mainly includes solvent, dispersant, binder, plasticizer and other functional additives, which respectively undertake the functions of flow medium, enhanced bonding force, improved flowability and performance adjustment.

[0004] One of the core factors affecting the thermal conductivity of silicon nitride ceramic sheet is the oxygen content of silicon powder. Studies have shown that as the particle size of silicon powder decreases, its oxygen content will gradually increase. In order to obtain silicon nitride ceramic sheet with high strength and toughness, it is usually necessary to use silicon powder with smaller particle size, because such silicon powder has larger specific surface area and can react more fully with nitrogen to form silicon nitride crystals with more compact structure, thereby improving the strength and hardness of the ceramic sheet. However, silicon powder with larger particle size has lower oxygen content, and the silicon nitride crystal boundary formed after reaction is less, which is beneficial to heat conduction, thereby improving the thermal conductivity of the ceramic sheet. However, its strength is relatively low. Therefore, it is difficult for a single particle size of silicon powder to achieve high strength while achieving high thermal conductivity. Therefore, the development of a silicon powder slurry with low oxygen content and small particle size to achieve a balance between high strength and high thermal conductivity has become a technical problem that needs to be solved in the field of silicon nitride ceramic sheet preparation.

[0005] The present application provides a method for preparing a silicon powder slurry with multiple particle sizes, which uses silicon powder with multiple particle sizes to prepare the silicon powder slurry, and can customize the particle size distribution. The present application effectively solves the dilemma of low oxygen content and small particle size in the existing silicon powder slurry preparation technology while reducing costs. SUMMARY

[0006] The present application aims to provide a method for preparing a silicon powder slurry with multiple particle sizes to solve the problems in the prior art.

[0007] To achieve the above object, the present application provides the following technical solutions.

[0008] A slurry preparation method of multi-particle-size silicon powder, comprising the following steps:

[0009] S1: Dry large-particle-size silicon powder, additive, and solvent are sequentially added into a ball mill, and nitrogen is passed through; after the oxygen content is lower than 1000 ppm, the large-particle-size silicon powder is ball milled for 1-2 h to obtain a ball-milled large-particle-size silicon powder slurry;

[0010] S2: Dry small-particle-size silicon powder is added into the ball-milled large-particle-size silicon powder slurry, and nitrogen is passed through; after the oxygen content is lower than 1000 ppm, the silicon powder slurry is ball milled for 1-2 h to obtain a silicon powder slurry;

[0011] S3: The silicon powder slurry is ultrasonically dispersed for 10-30 min at a power of 2-3 KW and a frequency of 10-20 KHz to obtain a pretreated silicon powder slurry;

[0012] S4: A binder and deionized water are mixed, heated to 70-80 DEG C, and stirred for 6-8 h to obtain a colloid;

[0013] S5: The colloid and a plasticizing agent are added into the pretreated silicon powder slurry, and ball milled for 8-10 h to obtain a multi-particle-size silicon powder slurry;

[0014] More preferably, the raw material composition of the multi-particle-size silicon powder slurry comprises, by weight fraction, 95-100 parts of silicon powder, 11-14 parts of additive, 100-120 parts of solvent, 30-60 parts of colloid, and 3-5 parts of plasticizing agent;

[0015] The raw material composition of the colloid in step S4 comprises 2-5 parts of binder and 40-50 parts of deionized water;

[0016] More preferably, the large-particle-size silicon powder and the small-particle-size silicon powder in the silicon powder slurry are compounded in a mass ratio of (55-65):(35-45); the particle size of the large-particle-size silicon powder ranges from 0.9 μm to 3.0 μm; and the particle size of the small-particle-size silicon powder ranges from 0.2 μm to 0.5 μm;

[0017] More preferably, the additive in step S1 is compounded from yttrium oxide, magnesium oxide, and castor oil in a mass ratio of (8-9):(1-2):(2-3);

[0018] More preferably, the plasticizing agent is one or a combination of dibutyl phthalate, dibutyl phthalate, polyethylene glycol, polyacrylate, and dibutyl sebacate;

[0019] More preferably, the binder is one or a combination of acrylic resin, polyvinyl alcohol, polyvinyl butyral, polypropylene carbonate and polyvinyl acetate.

[0020] More preferably, the binder is modified polyvinyl alcohol, and the preparation process of the modified polyvinyl alcohol is as follows: polyvinyl alcohol and deionized water are added to a reaction kettle, heated to 75-80 DEG C and stirred for 60-80 min, the pH is adjusted to 4-5, acetaldehyde, sulfuric acid and boric acid are added, and the reaction is carried out for 50-60 min; the temperature is lowered to 50-60 DEG C, tributyl phosphate, modified boron nitride and Yb-MOF are added, and stirred for 35-45 min; the temperature is lowered to 25-30 DEG C, and the pH is adjusted to 6.8-7.2 to obtain the modified polyvinyl alcohol.

[0021] The raw material composition of the modified polyvinyl alcohol is 15-20 parts of polyvinyl alcohol, 90-100 parts of deionized water, 2-4 parts of acetaldehyde, 0.05-0.1 parts of sulfuric acid, 0.1-0.2 parts of boric acid, 0.03-0.07 parts of tributyl phosphate, 1-3 parts of modified boron nitride and 0.5-1.5 parts of Yb-MOF by weight.

[0022] More preferably, the preparation process of the modified boron nitride is as follows: 3-aminopropyltrimethoxysilane, ethanol and deionized water are added to a reaction kettle in a mass ratio of 1:7:3, citric acid is used to adjust the pH to 4.5-5.0, the temperature is raised to 55-60 DEG C and reacted for 2-3 h, boron nitride, 50% ethanol aqueous solution and ammonium polyacrylate are added, ammonia is used to adjust the pH to 8-9, and then filtered, washed, vacuum dried to obtain the modified boron nitride.

[0023] More preferably, the preparation process of the Yb-MOF is as follows: 2,5-dihydroxyterephthalic acid and ytterbium acetate tetrahydrate are added to a polytetrafluoroethylene reaction kettle, deionized water and 1-hexyl-3-methylimidazolium bromide are added, ultrasonic stirring is carried out for 30-40 min, the temperature is raised to 150-165 DEG C and reacted for 20-24 h, cooled, centrifuged, washed with dimethylformamide, filtered, washed with ethanol and vacuum dried to obtain the Yb-MOF.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] The present application uses silicon powder with multiple particle sizes to prepare silicon powder slurry, which can customize the particle size distribution, effectively improve the dilemma that low oxygen content and small particle size cannot be achieved at the same time in the existing silicon powder slurry preparation technology, and reduce the cost.

[0026] In the process of preparing the multi-particle-size silicon powder slurry, first, the large-particle-size silicon powder, the additive and the solvent are sequentially added into a ball mill in a certain proportion, and nitrogen is introduced into the ball mill tank for deoxidation treatment, and then the ball milling program is started. The colloid can be pre-dissolved before stirring to improve the efficiency of subsequent operation and save time. After the large-particle-size silicon powder is completed, the small-particle-size silicon powder is added in proportion, and nitrogen is also introduced for deoxidation treatment before ball milling to reduce the oxidation reaction. After the small-particle-size silicon powder is completed, an ultrasonic disperser is placed in the ball mill, and ultrasonic dispersion treatment is carried out, and then the pre-dissolved colloid and the plasticizer are added, and the ball milling is continued.

[0027] The mixed slurry preparation method of large and small particle size silicon powder can not only shorten the overall ball milling time, but also effectively reduce the oxygen content of the slurry and reduce the slurry preparation cost, because the large particle size silicon powder has lower oxygen content and lower cost. In addition, by reasonably matching silicon powders of different particle sizes, the particle size distribution of the slurry can be flexibly adjusted to obtain the required wide or narrow particle size distribution range. In the whole ball milling process, nitrogen is introduced for deoxidation treatment before adding new materials each time, which helps to inhibit the oxidation of silicon powder during ball milling, thereby improving the quality of the slurry.

[0028] The modified polyvinyl alcohol introduces acetaldehyde modifier to occur acetalization reaction, under sulfuric acid catalysis, polyvinyl alcohol hydroxyl group and acetaldehyde occur nucleophilic addition reaction, form acetal bond, improve the crosslinking degree, thermal stability and water resistance of binder. In addition, boric acid forms boric acid ester bond with polyvinyl alcohol hydroxyl group, forms network structure, improves mechanical strength, and boric acid ester bond inhibits molecular chain thermal motion, improves thermal stability. Add modified boron nitride, under acidic conditions, silane coupling agent KH-550 occurs hydrolysis, generates silanol group, provides reaction site for boron nitride grafting; silanol and hydroxyl group on the surface of boron nitride occur condensation reaction, form Si-O-BN bond, interface bonding force improves, and peeling strength rises; the grafted amino group on the surface can form hydrogen bond with polyvinyl alcohol, improve wear resistance and dispersibility, and the embedded Yb-MOF pore enhances mechanical interlocking, so that the peeling strength is greatly improved, and the ceramic wear rate is reduced; boron nitride directional heat conduction and Yb-MOF cooperatively improve thermal conductivity performance; the amino group of boron nitride can form hydrogen bond with uncoordinated phenolic hydroxyl group in Yb-MOF, improve interface bonding force and peeling strength, so that the bending strength and thermal conductivity of silicon nitride ceramic can reach a high level in engineering application.

[0029] The multi-particle-size silicon powder slurry of the application is particularly suitable for the preparation of silicon nitride ceramic sheets, has good dispersibility, excellent dynamic mechanical properties and good compactness, solves the pain point that strength and thermal conductivity cannot be matched, and has comprehensive performance suitable for the preparation of high-performance silicon nitride ceramic. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A narrow silicon powder slurry particle size distribution graph is obtained for the embodiment 1 of the application.

[0031] Figure 2 The particle size distribution of the silicon powder slurry obtained for the present comparative example 1 is wide;

[0032] Figure 3 The particle size distribution of the silicon powder slurry obtained for the present comparative example 2 is wide;

[0033] Figure 4 The particle size distribution of the silicon powder slurry obtained for the present comparative example 3 is wide;

[0034] Figure 5 The particle size distribution of the silicon powder slurry obtained for the present comparative example 4 is wide;

[0035] Figure 6 The particle size distribution of the silicon powder slurry obtained for the present comparative example 5 is wide. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0037] Embodiment 1: A method for preparing a multi-particle-size silicon powder slurry, comprising the following steps:

[0038] S1: Dry large-particle-size silicon powder, additive, and ethanol are sequentially added into a ball mill, and nitrogen is passed through. After the oxygen content is 800 ppm, the ball milling is carried out at a speed of 55 r / min for 2 h to obtain a large-particle-size silicon powder slurry after ball milling;

[0039] S2: Dry small-particle-size silicon powder is added into the large-particle-size silicon powder slurry, and nitrogen is passed through. After the oxygen content is 800 ppm, the ball milling is carried out at a speed of 50 r / min for 2 h to obtain a silicon powder slurry;

[0040] S3: The silicon powder slurry is ultrasonically dispersed at a power of 2.5 KW and a frequency of 18 KHz for 25 min to obtain a pretreated silicon powder slurry;

[0041] S4: Polyvinyl alcohol and deionized water are mixed, heated to 75℃, and stirred at a stirring speed of 900 r / min for 7 h to obtain a colloid;

[0042] S5: The colloid and dibutyl phthalate are added into the pretreated silicon powder slurry, and the ball milling is carried out at a speed of 60 r / min for 8 h to obtain a multi-particle-size silicon powder slurry.

[0043] The raw material composition of the one kind of multi-particle-size silicon powder slurry is: 100 parts of silicon powder, 12 parts of additive, 100 parts of ethanol, 60 parts of colloid, 5 parts of dibutyl phthalate, in weight parts;

[0044] The raw material composition of the colloid in step S4 is: 5 parts of polyvinyl alcohol, 40 parts of deionized water;

[0045] The mass ratio of the large-particle-size silicon powder to the small-particle-size silicon powder in the silicon powder slurry is 55:45; the particle size of the large-particle-size silicon powder is 1.0 μm; and the particle size of the small-particle-size silicon powder is 0.2 μm;

[0046] The additive in step S1 is yttrium oxide, magnesium oxide, and castor oil, which are compounded in a mass ratio of 8:2:2.

[0047] Embodiment 2: A method for preparing a multi-particle-size silicon powder slurry, comprising the following steps:

[0048] S1: Dry large-particle-size silicon powder, additive, and ethanol are sequentially added into a ball mill, and nitrogen is passed through; after the oxygen content reaches 800 ppm, the ball milling is carried out at a speed of 60 r / min for 1 h to obtain a large-particle-size silicon powder slurry after ball milling;

[0049] S2: Dry small-particle-size silicon powder is added into the large-particle-size silicon powder slurry after ball milling, and nitrogen is passed through; after the oxygen content reaches 800 ppm, the ball milling is carried out at a speed of 48 r / min for 2 h to obtain a silicon powder slurry;

[0050] S3: The silicon powder slurry is ultrasonically dispersed at a power of 3 KW and a frequency of 12 KHz for 15 min to obtain a pretreated silicon powder slurry;

[0051] S4: Polyvinyl alcohol and deionized water are mixed, heated to 70℃, and stirred at a stirring speed of 1000 r / min for 8 h to obtain a colloid;

[0052] S5: The colloid and dibutyl phthalate are added into the pretreated silicon powder slurry, and ball milling is carried out at a speed of 50 r / min for 10 h to obtain a multi-particle-size silicon powder slurry;

[0053] The raw material composition of the one kind of multi-particle-size silicon powder slurry is: 100 parts of silicon powder, 12 parts of additive, 100 parts of ethanol, 60 parts of colloid, 5 parts of dibutyl phthalate, in weight parts;

[0054] The raw material composition of the colloid in step S4 is: 3 parts of polyvinyl alcohol, 50 parts of deionized water;

[0055] The mass ratio of the large-particle-size silicon powder to the small-particle-size silicon powder in the silicon powder slurry is 55:45; the particle size of the large-particle-size silicon powder is 1.0 μm; and the particle size of the small-particle-size silicon powder is 0.2 μm;

[0056] The external additive in step S1 is yttrium oxide, magnesium oxide and castor oil with a mass ratio of 9:1:2;

[0057] The binder is modified polyvinyl alcohol, and the preparation process of the modified polyvinyl alcohol is as follows: polyvinyl alcohol and deionized water are added into a reaction kettle, heated to 75℃ and stirred for 80 min, the pH is adjusted to 4.2, acetaldehyde, sulfuric acid and boric acid are added, and the reaction is carried out for 60 min; the temperature is lowered to 55℃, tributyl phosphate, modified boron nitride and Yb-MOF are added, and stirred for 45 min; the temperature is lowered to 30℃, and the pH is adjusted to 7.2 to obtain the modified polyvinyl alcohol;

[0058] The raw material composition of the modified polyvinyl alcohol is 20 parts of polyvinyl alcohol, 92 parts of deionized water, 3 parts of acetaldehyde, 0.1 parts of sulfuric acid, 0.2 parts of boric acid, 0.06 parts of tributyl phosphate, 2 parts of modified boron nitride and 0.5 parts of Yb-MOF, by weight;

[0059] The preparation process of the modified boron nitride is as follows: 10g of 3-aminopropyltrimethoxysilane, 70mL of ethanol and 30mL of deionized water are added into a reaction kettle, the pH is adjusted to 4.5 with citric acid, the temperature is raised to 55℃ and the reaction is carried out for 3h, 100g of boron nitride, 100mL of 50% mass concentration ethanol aqueous solution and 0.5g of polyacrylammonium are added, the pH is adjusted to 8.5 with ammonia water, and then filtered, washed and vacuum dried to obtain the modified boron nitride;

[0060] The preparation process of the Yb-MOF is as follows: 1.2g of 2,5-dihydroxyterephthalic acid and 1.9g of ytterbium acetate tetrahydrate are added into a polytetrafluoroethylene reaction kettle, 15mL of deionized water and 6g of 1-hexyl-3-methylimidazolium bromide are added, ultrasonic stirring is carried out for 40min, the temperature is raised to 160℃ and the reaction is carried out for 24h, and then cooling, centrifugation, dimethylformamide washing, filtration and ethanol cleaning are carried out, and vacuum drying is carried out to obtain the Yb-MOF.

[0061] Comparative Example 1: The silicon powder is a large particle size silicon powder and a small particle size silicon powder with a mass ratio of 80:20, and other procedures are normal.

[0062] Comparative Example 2: The nitrogen purging steps in S1 and S2 are cancelled, and other procedures are normal.

[0063] Comparative Example 3: The ultrasonic dispersion step in S3 is cancelled, and other procedures are normal.

[0064] Comparative Example 4: The oxygen content in the nitrogen purging in S1 and S2 is changed to 5000ppm, and other procedures are normal.

[0065] Comparative Example 5: The ultrasonic dispersion time in S3 is changed to 10min, and other procedures are normal.

[0066] The source of the raw materials used (only as an example) is as follows:

[0067] The raw materials in the technical solution are all products currently sold on the market. Silicon powder (7440-21-3, 99%): Nanjing Chemical Reagent Co., Ltd.; Yttrium oxide: 1314-36-9, 99%, 0.5 μm; Magnesium oxide: 1309-48-4, 99%, 1.0 μm; Castor oil (8001-79-4, 99.9%): Shanghai Fangye Chemical Co., Ltd.; Dibutyl phthalate (84-74-2, 99.5%): Shandong Yukang Chemical Co., Ltd.; Polyvinyl alcohol (S30196, 99%): Shanghai Yuan Ye Biological Technology Co., Ltd.; Acetaldehyde (75-07-0, 99%): Condiss Chemical Industry (Hubei) Co., Ltd.; Boric acid (10043-35-3, 99.9%): Jinhanu Chemical Co., Ltd. in Jinan; Tributyl phosphate (126-73-8, 98%): Taizhou Xianhe Pharmaceutical and Biological Technology Co., Ltd.; Boron nitride: 10043-11-5, 99.9%, 2 μm; 3-Aminopropyltrimethoxysilane (13822-56-5, 99%): Hubei Baodu Chemical Co., Ltd.; Ammonium polyacrylate (9003-03-6, 99%): Hubei Jusheng Technology Co., Ltd.; 2,5-Dihydroxyterephthalic acid (610-92-4, 98%): Hubei Weishi Chemical Reagent Co., Ltd.; Ytterbium acetate tetrahydrate (15280-58-7, 99.9%): Beijing Huawei Ruikex Chemical Technology Co., Ltd.; 1-Hexyl-3-methylimidazolium bromide (85100-78-3, 98%): Hubei Weideli Chemical Technology Co., Ltd.; Sulfuric acid, sodium hydroxide, ammonia, citric acid, ethanol, hydrochloric acid, dimethylformamide, analytical pure, commercially available.

[0068] Performance test: the multi-particle size silicon powder slurries prepared in the examples and comparative examples were tested.

[0069] The silicon powder slurry was placed in a mold and sintered to form a silicon nitride ceramic.

[0070] (1) The particle size distribution of the silicon powder slurry of Examples 1 and Comparative Examples 1-5 was tested, as shown in the figure.

[0071] (2) The oxygen content of the dried slurry of Examples 1-2 and Comparative Examples 1-5 was tested: using inert gas melting-infrared analysis method, taking 1.0 g of dried slurry powder and placing it in a graphite crucible, flushing the system with high-purity helium at a flow rate of 500 mL / min, releasing oxygen by heating to 3000℃ through a pulse furnace, quantifying CO by an infrared detector, using NIST SRM 1106a standard material for calibration, repeating the measurement until the deviation is <50 ppm, and testing in parallel for 3 times, as shown in Table 2.

[0072] (3) The bending strength test of the silicon nitride ceramic prepared in Example 1-2 was carried out: an electronic universal testing machine was used to prepare 3mmx4mmx40mm ceramic sheet samples, the surface was polished to Ra 0.05μm, the three-point bending method was used for testing, the span was 30mm, the loading rate was 0.5mm / min, 5 effective samples were tested in each group, the data deviating from the mean value ± 15% was eliminated, and the arithmetic mean value was taken as the bending strength result, as shown in Table 2.

[0073] (4) The thermal conductivity test of the silicon nitride ceramic prepared in Example 1-2 was carried out: a laser flash method thermal conductivity instrument was used, the ceramic sheet was processed into a 12.7mmx1.0mm disc, the double sides were sprayed with a graphite coating, the test conditions were: 25℃ constant temperature, pulse energy 2J, data acquisition frequency 1MHz, repeated measurement 3 times, the mean value was taken when the fluctuation value was <3%, and the thermal conductivity was calculated, as shown in Table 2.

[0074] The test results are as follows:

[0075] Table 1

[0076]

[0077] Table 2

[0078] Flexural strength (MPa) Thermal conductivity (W / (m-K)) Experimental Example 1 819 86.8 Experimental Example 2 880 92.3

[0079] The analysis results are as follows:

[0080] As can be seen from the data in the above table, the performance of the silicon nitride ceramic in the application has a positive effect, and the bending strength and thermal conductivity are significantly improved. The electronic universal testing machine is used to analyze the silicon nitride ceramic, the modified polyvinyl alcohol is added, the bending strength of the ceramic is determined by the three-point bending method, which is 880℃, which is higher than that of the unmodified system; the laser flash method thermal conductivity instrument is used to test the thermal conductivity of the silicon nitride ceramic sheet, and the result is more than 90%. In the scheme, the polyvinyl alcohol is replaced by the modified polyvinyl alcohol, which loses the acetalization reaction, which will cause the crosslinking degree and the resistance of the silicon material to decrease, the modified silicon nitride added has excellent wear resistance, which can significantly compensate for the loss of bending strength caused by grinding, and has a promoting effect on the density and thermal conductivity of the silicon nitride ceramic; the silanol generated by the silane coupling agent condenses with the hydroxyl group on the surface of boron nitride to form Si-O-BN bond, the interfacial bonding force is improved, and the peeling strength is increased; the amino group grafted on the surface of boron nitride forms a hydrogen bond with polyvinyl alcohol, which can improve the wear resistance and dispersibility, and cooperates with Yb-MOF to improve the peeling strength and thermal conductivity performance, so as to reduce the ceramic wear rate.

[0081] As shown in the figure, there is large particle agglomeration when the silicon powder is not ultrasonic dispersed or the ultrasonic dispersion time is not enough. It takes a long time to grind the large particle size silicon powder. The preparation of the silicon powder slurry is carried out by using silicon powder with multiple particle sizes. The addition of small particle size silicon powder can shorten the ball milling time. At the same time, the oxygen content and cost of large particle size silicon powder are low, which can reduce the slurry preparation cost and the overall oxygen content of the slurry. In addition, the use of two particle sizes can customize the adjustment of the slurry particle size distribution, so as to obtain wide or narrow slurry particle size distribution. The tank is washed by passing nitrogen before ball milling, which can effectively reduce the oxygen increase of the silicon powder slurry in the ball milling process.

[0082] In summary, the silicon nitride ceramic sheet prepared by the application has better bending strength and thermal conductivity, effectively solves the dilemma that low oxygen content and small particle size cannot be achieved in the existing silicon powder slurry preparation technology, and can be widely applied.

[0083] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of the equivalent elements of the claims are intended to be included in the present application.

Claims

1. A method of slurrying a multi-particle size silicon powder, characterized by, It comprises the following steps: S1: dry large particle size silicon powder, admixture, solvent are added into the ball mill in turn, nitrogen is passed, after the oxygen content is lower than 1000ppm, ball milling for 1-2h, to obtain the large particle size silicon powder slurry after ball milling; S2: dry small particle size silicon powder is added into the large particle size silicon powder slurry after ball milling, nitrogen is passed, after the oxygen content is lower than 1000ppm, ball milling for 1-2h, to obtain the silicon powder slurry; S3: the silicon powder slurry is treated by ultrasonic dispersion, to obtain the pretreated silicon powder slurry; S4: the binder and deionized water are mixed, heated to 70-80℃ and stirred for 6-8h, to obtain the colloid; S5: the colloid and plasticizing agent are added into the pretreated silicon powder slurry, ball milling for 8-10h, to obtain a multi-particle size silicon powder slurry; The binder is modified polyvinyl alcohol, and the preparation process of the modified polyvinyl alcohol is as follows: polyvinyl alcohol and deionized water are added into a reaction kettle, heated to 75-80℃ and stirred for 60-80min, the pH is adjusted to 4-5, acetaldehyde, sulfuric acid and boric acid are added, and reacted for 50-60min; the temperature is lowered to 50-60℃, tributyl phosphate, modified boron nitride and Yb-MOF are added, and stirred for 35-45min; the temperature is lowered to 25-30℃, the pH is adjusted to 6.8-7.2, and the modified polyvinyl alcohol is obtained; The preparation process of the modified boron nitride is as follows: 3-aminopropyltrimethoxysilane, ethanol and deionized water are added into a reaction kettle in a mass ratio of 1:7:3, the pH is adjusted to 4.5-5.0, the temperature is raised to 55-60℃ and reacted for 2-3h, boron nitride, ethanol aqueous solution and polyammonium acrylate are added, the pH is adjusted to 8-9, filtered and washed, and vacuum dried to obtain the modified boron nitride; The large particle size silicon powder and the small particle size silicon powder in the silicon powder slurry are compounded in a mass ratio of (55-65):(35-45); the particle size of the large particle size silicon powder ranges from 0.9μm to 3.0μm; the particle size of the small particle size silicon powder ranges from 0.2μm to 0.5μm; and the ultrasonic dispersion treatment working conditions are as follows: power 2-3kW, frequency 10-20kHz, and time 15-30min; The raw material composition of the modified polyvinyl alcohol is as follows: 15-20 parts of polyvinyl alcohol, 90-100 parts of deionized water, 2-4 parts of acetaldehyde, 0.05-0.1 parts of sulfuric acid, 0.1-0.2 parts of boric acid, 0.03-0.07 parts of tributyl phosphate, 1-3 parts of modified boron nitride, and 0.5-1.5 parts of Yb-MOF.

2. The method of claim 1, wherein the method is characterized by: The raw material composition of the multi-particle size silicon powder slurry is as follows: 95-100 parts of silicon powder, 11-14 parts of admixture, 100-120 parts of solvent, 30-60 parts of colloid, and 3-5 parts of plasticizing agent, all by weight; 3. The method of claim 1, wherein the method further comprises: The admixture in step S1 is yttrium oxide, magnesium oxide and castor oil, compounded in a mass ratio of (8-9):(1-2):(2-3). ​ 4. The method of claim 1, wherein the method further comprises: The plasticizing agent is one or a combination of dibutyl phthalate, dibutyl phthalate, polyethylene glycol, polyacrylate and dibutyl sebacate. ​ 5. The method of claim 1, wherein the method further comprises: The preparation process of the Yb-MOF is as follows: 2,5-dihydroxyterephthalic acid, ytterbium acetate tetrahydrate are added into a polytetrafluoroethylene reaction kettle, deionized water and 1-hexyl-3-methylimidazolium bromide are added, ultrasonic stirring is carried out for 30-40 min, the temperature is increased to 150-165 DEG C, and reaction is carried out for 20-24 h, then cooling, centrifugation, dimethylformamide washing, filtration, ethanol cleaning and vacuum drying are carried out to obtain the Yb-MOF. ​ 6. A multi-particle size silicon powder slurry characterized by: The pulp is prepared according to the pulp preparation method of any one of claims 1-5.

Images