A nano-silicon reaction sintered silicon carbide support plate and a preparation method thereof

Abstract

This invention belongs to the field of refractory material preparation technology, specifically a nano-silicon reaction-sintered silicon carbide sintering plate and its preparation method. 0.5-30 μm silicon carbide powder, 1-45 μm biomass charcoal, and 20-200 nm nano-silicon powder are ball-milled and mixed in a certain mass ratio, followed by drying, grinding, and sieving to obtain fine powder. The fine powder is pressed into a green body, and then subjected to vacuum high-temperature reaction sintering at 1500-1800℃ for 2-5 h. After completion, a nano-silicon reaction-sintered silicon carbide sintering plate is obtained. This invention introduces nano-sized silicon powder into the reaction sintering system and uses biomass charcoal as a carbon source. During the sintering process, silicon carbide is fully generated and in-situ silicon carbide whiskers are induced, achieving densification and toughening effects on the silicon carbide sintering plate. It disrupts the continuous liquid-phase silicon spreading, reduces the risk of adhesion, and achieves an anti-adhesion effect without the need for a coating.

Description

A nano-silicon reaction sintered silicon carbide sintering plate and its preparation method Technical Field

[0001] This invention belongs to the field of refractory material preparation technology, specifically a nano-silicon reaction sintered silicon carbide sintering plate and its preparation method. Background Technology

[0002] Silicon carbide firing plates are widely used in the high-temperature firing of daily-use and industrial ceramics due to their advantages such as high temperature resistance, good thermal conductivity, and high strength. Compared with traditional mullite firing plates, silicon carbide firing plates can significantly reduce thickness, increase load-bearing capacity, and improve kiln thermal efficiency, thus gradually becoming an important firing support component in high-end kilns.

[0003] In the prior art, silicon carbide sintering plates are mainly prepared by reaction sintering process. This process usually involves mixing raw silicon carbide powder with a binder and pressing it into a blank, which is then densified by high-temperature heat treatment. However, silicon carbide sintering plates prepared by this reaction sintering process still have the following shortcomings during long-term high-temperature service: (1) Free silicon is easily generated during the reaction sintering process. Free silicon has high chemical activity at high temperatures and is easy to stick to the fired products, affecting the quality of the products; (2) In order to avoid adhesion, it is usually necessary to coat the sintering plate with an anti-stick coating such as alumina before use, which increases the complexity of the process and the cost of use. Moreover, the coating is prone to failure after multiple uses; (3) The traditional reaction sintering process is mainly based on particle sintering. The fracture toughness of silicon carbide sintering plates is limited. Under repeated thermal shock and heavy load conditions, cracking or deformation is likely to occur, affecting the service life.

[0004] Based on the above problems, there is an urgent need to develop a new type of silicon carbide sintering plate and its preparation method that can reduce the adverse effects of free silicon, improve the mechanical properties of silicon carbide sintering plates, and give them intrinsic anti-adhesion capabilities while maintaining the advantages of reaction sintering process. Summary of the Invention

[0005] The purpose of this invention is to provide a nano-silicon reaction sintered silicon carbide sintering plate and its preparation method. By introducing nano-sized silicon powder into the reaction sintering system and using biochar as a carbon source, the porous structure and surface activity of biochar are utilized to promote the wetting and diffusion of nano-silicon. During the sintering process, silicon carbide is generated more fully and silicon carbide whiskers are induced to form in situ. At the microstructural level, the silicon carbide sintering plate is densified and toughened. This disrupts the continuous liquid phase silicon spreading, reduces the risk of adhesion, and achieves an anti-adhesion effect without the need for a coating.

[0006] This invention is specifically achieved through the following technical solution: a method for preparing a nano-silicon reaction-sintered silicon carbide sintering plate according to this invention includes the following steps:

[0007] (1) Weigh 60-85 wt% of silicon carbide powder with a particle size of 0.5-30 μm, 5-20 wt% of biochar with a particle size of 1-45 μm and 10-20 wt% of nano-silicon powder with a particle size of 20-200 nm as raw materials according to mass percentage, add them together to a ball mill jar for ball milling and mixing to obtain a uniformly dispersed slurry;

[0008] (2) The resulting mixed slurry is dried, ground, and sieved to obtain a uniformly mixed fine powder;

[0009] (3) Press the obtained uniformly mixed fine powder into shape to obtain the green blank of the firing plate;

[0010] (4) The green blank of the sintering plate is placed in a vacuum reaction sintering furnace for high-temperature reaction sintering. The sintering temperature is 1500-1800℃ and the sintering time is 2-5 h to obtain a whisker-reinforced nano-silicon reaction sintered silicon carbide sintering plate.

[0011] The aforementioned method for preparing nano-silicon reaction sintered silicon carbide sintering plate, wherein the silicon carbide powder is a multi-particle-size graded silicon carbide powder, including coarse silicon carbide particles with a particle size of 10-30 μm, medium silicon carbide particles with a particle size of 3-10 μm, and fine silicon carbide particles with a particle size of 0.5-3 μm, wherein the mass percentages of the coarse silicon carbide particles, medium silicon carbide particles, and fine silicon carbide particles to the total mass of the raw materials are 25-45 wt%, 15-25 wt%, and 15-25 wt%, respectively.

[0012] In the aforementioned method for preparing nano-silicon reaction sintered silicon carbide sintering plate, the biomass charcoal is selected from one or more of coconut shell charcoal, corn cob charcoal, bamboo charcoal, and rice husk charcoal.

[0013] Preferably, in step (1), anhydrous ethanol or isopropanol is used as the ball milling medium, and the mass ratio of the ball milling medium to the raw material is (3-6):1.

[0014] Preferably, in step (1), the ball mill speed is 80-300 r / min and the ball milling time is 2-10 h.

[0015] Preferably, the drying temperature in step (2) is 60-120℃ and the drying time is 8-24 h.

[0016] Preferably, the molding pressure in step (3) is 100-200 MPa and the holding time is 10-90 s.

[0017] In the aforementioned method for preparing the nano-silicon reaction-sintered silicon carbide sintering plate, during the sintering process, nano-silicon powder reacts in situ with biomass char to generate silicon carbide and induces the formation of silicon carbide whiskers. The length of the silicon carbide whiskers is 1-25 μm, and the diameter is 50-500 nm. The bulk density of this nano-silicon reaction-sintered silicon carbide sintering plate is 3.0-3.3 g / cm³. 3 The flexural strength is 400-480 MPa, and the fracture toughness is 5.2-5.9 MPa·m. 1 / 2 .

[0018] The present invention also provides a silicon carbide sintering plate obtained by the aforementioned preparation method, wherein silicon carbide whiskers are uniformly distributed in situ, and the silicon carbide whiskers form an interwoven network structure in the silicon carbide grain boundary region and the pore connection region, which plays a bridging and deflecting role in crack propagation, effectively improving the density and bending strength of the silicon carbide sintering plate.

[0019] Compared with the prior art, the present invention has significant advantages and beneficial effects, achieving considerable technological progress and practicality, and has broad application value. It possesses at least the following advantages:

[0020] (1) The present invention uses nano silicon powder as the reaction silicon source in the reaction sintering process. Nano silicon powder has the characteristics of large specific surface area and high reaction activity. It can fully react with biochar in the early stage of reaction sintering. The porous structure and active sites of biochar provide an effective mass transfer channel for silicon diffusion and reaction, making the silicon-carbon reaction more complete, reducing the amount of free silicon residue in the sintering plate, and improving the chemical stability and service reliability of the sintering plate under high temperature conditions.

[0021] (2) During the reaction sintering process, the nano-silicon powder in the green blank of the sintering plate reacts with biomass char, generating silicon carbide in situ inside the silicon carbide sintering plate matrix and inducing the formation of silicon carbide whiskers. The silicon carbide whiskers are formed synchronously with the sintering plate matrix, and the interface is tightly bonded. This allows for bridging, deflection, and pinning of cracks at the microscale, effectively inhibiting crack propagation. Compared with external whisker reinforcement, this invention avoids the problems of uneven dispersion of the reinforcing phase and weak interface bonding, and improves the bending strength, fracture toughness, and thermal shock resistance of the sintering plate.

[0022] (3) The in-situ formed silicon carbide whiskers create a "rough-discontinuous" microstructure, which effectively disrupts the formation and spreading of continuous liquid silicon under high-temperature conditions, weakens the wetting behavior of liquid silicon on sintered products, and thus greatly reduces the tendency of silicon carbide sintering plates to stick to products during high-temperature sintering. Compared with the existing technology that relies on surface coating for anti-sticking, this invention achieves an intrinsic anti-sticking effect without additional coating, avoiding the use risks caused by coating peeling or failure.

[0023] (4) This invention uses biomass charcoal such as coconut shell charcoal and corn cob charcoal to replace part of the traditional carbon source. The sources are wide-ranging and the cost is low, which is conducive to the high-value utilization of resources and green and low-carbon manufacturing. At the same time, the preparation process of this invention is still based on the conventional reaction sintering process, which does not require the introduction of complex or high-cost special equipment. The process is stable and highly controllable, and is particularly suitable for the industrial preparation of large-size silicon carbide sintering plates. It has good economic benefits and prospects for promotion and application. Attached Figure Description

[0024] Figure 1 is a SEM image of the nano-silicon reaction sintered silicon carbide sintering plate prepared in Example 1.

[0025] Figure 2 is the XRD pattern of the nano-silicon reaction sintered silicon carbide sintering plate prepared in Example 1.

[0026] Figure 3 is a SEM image of the nano-silicon reaction sintered silicon carbide sintering plate prepared in Example 2.

[0027] Figure 4 is a SEM image of the nano-silicon reaction sintered silicon carbide sintering plate prepared in Example 3.

[0028] Figure 5 is a SEM image of the silicon carbide sintering plate prepared in Comparative Example 1. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise specified, all conditions in the following examples were performed under conventional conditions or conditions recommended by the manufacturer. Raw materials and reagents whose manufacturers are not specified are all commercially available products. Unless otherwise stated, all percentages used in this invention are mass percentages.

[0031] Example 1

[0032] A nano-silicon reaction-sintered silicon carbide sintering plate comprises, by weight percentage: 75 wt% silicon carbide powder with a particle size of 0.5-30 μm, 10 wt% coconut shell carbon with a particle size of 30-45 μm, and 15 wt% nano-silicon powder with a particle size of 20-100 nm. The silicon carbide powder is a multi-particle-size graded silicon carbide powder, including coarse silicon carbide particles with a particle size of 10-30 μm, medium silicon carbide particles with a particle size of 3-10 μm, and fine silicon carbide particles with a particle size of 0.5-3 μm. The mass percentages of the coarse, medium, and fine silicon carbide particles in the total mass of the raw materials are 30 wt%, 20 wt%, and 25 wt%, respectively.

[0033] The preparation method of this nano-silicon reaction sintered silicon carbide sintering plate includes the following steps:

[0034] (1) Weigh 75 parts of silicon carbide powder, 10 parts of coconut shell carbon and 15 parts of nano silicon powder according to the above raw materials and mass percentages, add them together to the ball mill jar, add anhydrous ethanol as the grinding medium, the mass ratio of anhydrous ethanol to solid raw materials is 4:1, use silicon carbide grinding balls as grinding balls, the ball-to-material ratio is 3:1, and carry out ball milling and mixing in a ball mill, the ball mill speed is 200 r / min, the ball milling time is 5 h, and a uniformly dispersed mixed slurry is obtained;

[0035] (2) The ball-milled slurry was placed in a drying oven for drying at 80 ℃ for 12 h. After drying, the material was ground and passed through a 60-mesh sieve to obtain a uniformly mixed fine powder.

[0036] (3) The fine powder that is mixed evenly above is loaded into a stainless steel mold for unidirectional pressing and molding. The molding pressure is 150MPa and the holding time is 20s to obtain the green blank of the firing plate.

[0037] (4) The green blank of the sintering plate was placed in a vacuum reaction sintering furnace for high-temperature reaction sintering. The sintering atmosphere was vacuum, the sintering temperature was 1700 ℃, and the holding time was 3 h. During the sintering process, the nano-silicon powder reacted with coconut shell carbon to form silicon carbide. The high reactivity of coconut shell carbon and the gas-phase reaction environment it formed promoted the in-situ growth of silicon carbide whiskers. After sintering, the product was cooled to room temperature with the furnace to obtain a whisker-reinforced nano-silicon reaction sintered silicon carbide sintering plate, which was denoted as sample S1.

[0038] Figure 1 and Figure 2 are the SEM and XRD images of sample S1, respectively. As can be seen from Figure 1, silicon carbide whiskers generated in situ are uniformly distributed in sample S1. The length of the silicon carbide whiskers is 5-15 μm and the diameter is 150-400 nm. The silicon carbide whiskers play a bridging and deflecting role in crack propagation.

[0039] As shown in Figure 2, the phases of the prepared silicon carbide sintering plate are mainly composed of α-SiC and β-SiC, and no free Si phase was detected, indicating that Si has fully reacted and completely transformed into SiC.

[0040] Example 2

[0041] A nano-silicon reaction sintered silicon carbide support plate comprises, by weight percentage: 70 wt% silicon carbide powder with a particle size of 0.5-30 μm, 12 wt% coconut shell carbon with a particle size of 30-45 μm, and 18 wt% nano-silicon powder with a particle size of 50-200 nm. The silicon carbide powder is a multi-particle-size graded silicon carbide powder, including coarse silicon carbide particles with a particle size of 10-30 μm, medium silicon carbide particles with a particle size of 3-10 μm, and fine silicon carbide particles with a particle size of 0.5-3 μm. The mass percentages of the coarse, medium, and fine silicon carbide particles in the total mass of the raw materials are 25 wt%, 25 wt%, and 20 wt%, respectively.

[0042] The preparation method of this nano-silicon reaction sintered silicon carbide sintering plate includes the following steps:

[0043] (1) Weigh 70 parts of silicon carbide powder, 12 parts of coconut shell carbon and 18 parts of nano silicon powder according to the above raw materials and mass percentages, add them together into a ball mill jar, add isopropanol as grinding medium, the mass ratio of isopropanol to solid raw materials is 4:1, use silicon carbide grinding balls as grinding balls, the ball-to-material ratio is 3:1, and carry out ball milling and mixing in a ball mill, the ball mill speed is 220 r / min, the ball milling time is 6 h, and a uniformly dispersed mixed slurry is obtained;

[0044] (2) The ball-milled slurry was placed in a drying oven for drying at a temperature of 85 ℃ for 12 h. After drying, the material was ground and passed through a 60-mesh sieve to obtain a finely mixed powder.

[0045] (3) The fine powder mixed evenly above is loaded into a stainless steel mold for unidirectional pressing and molding. The molding pressure is 160MPa and the holding time is 60s to obtain the green blank of the firing plate.

[0046] (4) The green blank of the sintering plate was placed in a vacuum reaction sintering furnace for high-temperature reaction sintering. The sintering atmosphere was vacuum, the sintering temperature was 1750 ℃, and the holding time was 3 h. During the sintering process, the nano-silicon powder reacted with coconut shell carbon to form silicon carbide. The high reactivity of coconut shell carbon and the gas-phase reaction environment it formed promoted the in-situ growth of silicon carbide whiskers. After sintering, the product was cooled to room temperature with the furnace to obtain a whisker-reinforced nano-silicon reaction sintered silicon carbide sintering plate, which was denoted as sample S2.

[0047] Figure 3 is an SEM image of sample S2 prepared in this embodiment. It can be seen that silicon carbide whiskers generated in situ are uniformly distributed in sample S2. The length of the silicon carbide whiskers is 10-25 μm and the diameter is 50-200 nm. The silicon carbide whiskers are mainly distributed in the silicon carbide pore connection region, which plays a bridging and deflecting role in crack propagation.

[0048] Example 3

[0049] A nano-silicon reaction-sintered silicon carbide sintering plate comprises, by mass percentage, 80 wt% silicon carbide powder with a particle size of 0.5-30 μm, 8 wt% corn cob char with a particle size of 20-40 μm, and 12 wt% nano-silicon powder with a particle size of 20-100 nm. The silicon carbide powder is a multi-particle-size graded silicon carbide powder, including coarse silicon carbide particles with a particle size of 10-30 μm, medium silicon carbide particles with a particle size of 3-10 μm, and fine silicon carbide particles with a particle size of 0.5-3 μm. The mass percentages of the coarse, medium, and fine silicon carbide particles in the total mass of the raw materials are 35 wt%, 25 wt%, and 20 wt%, respectively.

[0050] The preparation method of this nano-silicon reaction sintered silicon carbide sintering plate includes the following steps:

[0051] (1) Weigh 80 parts of silicon carbide powder, 8 parts of corn cob carbon and 12 parts of nano silicon powder according to the above raw materials and mass percentages, add them together to the ball mill jar, add anhydrous ethanol as the grinding medium, the mass ratio of anhydrous ethanol to solid raw materials is 3.5:1, use silicon carbide grinding balls as grinding balls, the ball-to-material ratio is 2.5:1, and carry out ball milling and mixing in a ball mill at a speed of 180 r / min for 5 h to obtain a uniformly dispersed mixed slurry;

[0052] (2) The ball-milled slurry was placed in a drying oven for drying at a temperature of 75 ℃ for 10 h. After drying, the material was ground and passed through an 80-mesh sieve to obtain a finely mixed powder.

[0053] (3) The fine powder mixed evenly above is loaded into a stainless steel mold for unidirectional pressing and molding. The molding pressure is 140MPa and the holding time is 90s to obtain the green blank of the firing plate.

[0054] (4) The green blank of the sintering plate was placed in a vacuum reaction sintering furnace for high-temperature reaction sintering. The sintering atmosphere was vacuum, the sintering temperature was 1750 ℃, and the holding time was 5 h. During the sintering process, the nano-silicon powder reacted with corn cob carbon to form silicon carbide. The high reactivity of the corn cob carbon and the gas-phase reaction environment it formed promoted the in-situ growth of silicon carbide whiskers. After sintering, the product was cooled to room temperature with the furnace to obtain a whisker-reinforced nano-silicon reaction sintered silicon carbide sintering plate, which was designated as sample S3.

[0055] Figure 4 is an SEM image of sample S3 prepared in this embodiment. It can be seen that silicon carbide whiskers generated in situ are uniformly distributed in sample S3. The length of the silicon carbide whiskers is 8-20 μm and the diameter is 100-300 nm. The silicon carbide whiskers form an interwoven network structure in the silicon carbide grain boundary region and the pore connection region, which effectively improves the density and bending strength of the silicon carbide sintering plate.

[0056] Example 4

[0057] A nano-silicon reaction sintered silicon carbide support plate comprises, by mass percentage: 60 wt% silicon carbide powder with a particle size of 0.5-30 μm, 20 wt% bamboo charcoal with a particle size of 1-20 μm, and 20 wt% nano-silicon powder with a particle size of 50-200 nm. The silicon carbide powder is a multi-particle-size graded silicon carbide powder, including coarse silicon carbide particles with a particle size of 10-30 μm, medium silicon carbide particles with a particle size of 3-10 μm, and fine silicon carbide particles with a particle size of 0.5-3 μm. The mass percentages of the coarse, medium, and fine silicon carbide particles in the total mass of the raw materials are 30 wt%, 15 wt%, and 15 wt%, respectively.

[0058] The preparation method of this nano-silicon reaction sintered silicon carbide sintering plate includes the following steps:

[0059] (1) Weigh 60 parts of silicon carbide powder, 20 parts of bamboo charcoal and 20 parts of nano silicon powder according to the above raw materials and mass percentages, add them together to the ball mill jar, add anhydrous ethanol as the grinding medium, the mass ratio of anhydrous ethanol to solid raw materials is 5:1, use silicon carbide grinding balls as grinding balls, the ball-to-material ratio is 3:1, and carry out ball milling and mixing in a ball mill, the ball mill speed is 250 r / min, the ball milling time is 5 h, and a uniformly dispersed mixed slurry is obtained;

[0060] (2) The ball-milled slurry was placed in a drying oven for drying at a temperature of 90 ℃ for 8 hours. After drying, the material was ground and passed through an 80-mesh sieve to obtain a uniformly mixed fine powder.

[0061] (3) The fine powder that is mixed evenly above is loaded into a stainless steel mold for unidirectional pressing and molding. The molding pressure is 200MPa and the holding time is 40s to obtain the green blank of the firing plate.

[0062] (4) The green blank of the sintering plate was placed in a vacuum reaction sintering furnace for high-temperature reaction sintering. The sintering atmosphere was vacuum, the sintering temperature was 1800 ℃, and the holding time was 4 h. During the sintering process, the nano-silicon powder reacted with bamboo charcoal to form silicon carbide. The high reactivity of bamboo charcoal and the gas-phase reaction environment it formed promoted the in-situ growth of silicon carbide whiskers. After sintering, the product was cooled to room temperature with the furnace to obtain a whisker-reinforced nano-silicon reaction sintered silicon carbide sintering plate, which was designated as sample S4.

[0063] Example 5

[0064] A nano-silicon reaction sintered silicon carbide support plate comprises, by weight percentage: 85 wt% silicon carbide powder with a particle size of 0.5-30 μm, 5 wt% rice husk charcoal with a particle size of 10-35 μm, and 10 wt% nano-silicon powder with a particle size of 50-200 nm. The silicon carbide powder is a multi-particle-size graded silicon carbide powder, including coarse silicon carbide particles with a particle size of 10-30 μm, medium silicon carbide particles with a particle size of 3-10 μm, and fine silicon carbide particles with a particle size of 0.5-3 μm. The mass percentages of the coarse, medium, and fine silicon carbide particles in the total mass of the raw materials are 45 wt%, 20 wt%, and 20 wt%, respectively.

[0065] The preparation method of this nano-silicon reaction sintered silicon carbide sintering plate includes the following steps:

[0066] (1) Weigh 85 parts of silicon carbide powder, 5 parts of rice husk charcoal and 10 parts of nano silicon powder according to the above raw materials and mass percentages, add them together to the ball mill jar, add anhydrous ethanol as the grinding medium, the mass ratio of anhydrous ethanol to solid raw materials is 6:1, use silicon carbide grinding balls as grinding balls, the ball-to-material ratio is 3:1, and carry out ball milling and mixing in a ball mill, the ball mill speed is 200 r / min, the ball milling time is 4 h, and a uniformly dispersed mixed slurry is obtained;

[0067] (2) The ball-milled slurry was placed in a drying oven for drying at 80 ℃ for 9 hours. After drying, the material was ground and passed through an 80-mesh sieve to obtain a uniformly mixed fine powder.

[0068] (3) The fine powder that is mixed evenly above is loaded into a stainless steel mold for unidirectional pressing and molding. The molding pressure is 180MPa and the holding time is 50s to obtain the green blank of the firing plate.

[0069] (4) The green blank of the sintering plate was placed in a vacuum reaction sintering furnace for high-temperature reaction sintering. The sintering atmosphere was vacuum, the sintering temperature was 1650 ℃, and the holding time was 5 h. During the sintering process, the nano-silicon powder reacted with rice husk char to generate silicon carbide. The high reactivity of rice husk char and the gas-phase reaction environment it formed promoted the in-situ growth of silicon carbide whiskers. After sintering, the product was cooled to room temperature with the furnace to obtain a whisker-reinforced nano-silicon reaction sintered silicon carbide sintering plate, which was designated as sample S5.

[0070] Comparative Example 1

[0071] A silicon carbide sintered plate, the raw materials of which, by mass percentage, include: 75 wt% silicon carbide powder with a particle size of 0.5-30 μm, 10 wt% carbon source with a particle size of 30-45 μm, and 15 wt% nano-silicon powder with a particle size of 20-100 nm. The carbon source is a mixture of carbon black and graphite, and the mass ratio of carbon black to graphite is 1:1. All other conditions and preparation processes are the same as in Example 1. The SEM image of the final silicon carbide sintered plate sample D1 is shown in Figure 5. It can be seen that the silicon carbide whiskers in sample D1 are underdeveloped and few in number, making it difficult to form an effective reinforcing network structure within the matrix. The material still retains many interconnected pores, and the grain boundary bonding is relatively weak, resulting in low overall mechanical properties and service stability.

[0072] Comparative Example 2

[0073] A silicon carbide sintering plate, the raw materials of which, by mass percentage, include: 75 wt% silicon carbide powder with a particle size of 0.5-30 μm, 25 wt% coconut shell carbon with a particle size of 30-45 μm, and do not contain nano-silicon powder. The remaining conditions and preparation process are the same as in Example 1, and the silicon carbide sintering plate sample D2 is finally obtained.

[0074] Comparative Example 3

[0075] A silicon carbide sintering plate, the raw materials of which, by mass percentage, include: 75 wt% silicon carbide powder with a particle size of 0.5-30 μm, 22 wt% coconut shell carbon with a particle size of 30-45 μm, and 3 wt% nano-silicon powder with a particle size of 20-100 nm. All other conditions and preparation processes are the same as in Example 1, and the final silicon carbide sintering plate sample D3 is obtained.

[0076] Comparative Example 4

[0077] A silicon carbide sintering plate, the raw materials of which, by mass percentage, include: 75 wt% silicon carbide powder with a particle size of 0.5-30 μm, 3 wt% coconut shell carbon with a particle size of 30-45 μm, and 22 wt% nano-silicon powder with a particle size of 20-100 nm. All other conditions and preparation processes are the same as in Example 1, and the final silicon carbide sintering plate sample D4 is obtained.

[0078] Performance testing:

[0079] (1) Bulk density test method: The bulk density of the silicon carbide sintered plate samples (hereinafter referred to as "samples") prepared in Examples 1-5 and Comparative Examples 1-4 was measured by Archimedes' displacement method according to the method of standard GB / T 2997-2015. The detailed measurement method is a mature existing technology and will not be described in detail.

[0080] (2) The room temperature bending strength of the specimen was tested in accordance with the standard GB / T3001-2007.

[0081] (3) The room temperature fracture toughness of the specimen was tested in accordance with the standard GB / T 23806-2009.

[0082] The silicon carbide sintering plates obtained in Examples 1-5 and Comparative Examples 1-4 were tested according to the above test methods. The test results are shown in Table 1 below.

[0083] Table 1. Performance test results of silicon carbide sintered plates in the examples and comparative examples

[0084]

[0085] Comparing the test results of each embodiment and comparative example in Table 1, it can be seen that the nano-silicon reaction sintered silicon carbide sintering plate provided by the present invention exhibits significant advantages in terms of bulk density, flexural strength, and fracture toughness. Compared with Example 1, the bulk density, flexural strength, and fracture toughness of the silicon carbide sintering plate obtained by replacing the carbon source with non-biomass charcoal (Comparative Example 1) or not adding nano-silicon powder to the raw materials (Comparative Example 2) are all inferior to those of Example 1. Similarly, if the mass percentages of silicon carbide powder, non-biomass charcoal, and nano-silicon powder are not within the preferred range described in the present invention, the various properties of the prepared silicon carbide sintering plate are also significantly lower than those of Example 1. This demonstrates that using biomass charcoal as the raw material and adding an appropriate proportion of nano-silicon powder, under the condition of reasonable control of the raw material ratio and process parameters, can effectively improve the density and mechanical properties of the silicon carbide sintering plate, demonstrating good technical effects and industrial application value.

[0086] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a nano-silicon reaction-sintered silicon carbide sintering plate, characterized in that, Includes the following steps: (1) Weigh 60-85 wt% of silicon carbide powder with a particle size of 0.5-30 μm, 5-20 wt% of biochar with a particle size of 1-45 μm and 10-20 wt% of nano-silicon powder with a particle size of 20-200 nm as raw materials according to mass percentage, and add them together to a ball mill jar for ball milling and mixing to obtain a uniformly dispersed mixed slurry; (2) Dry, grind and sieve the obtained mixed slurry to obtain a uniformly mixed fine powder; (3) Press the obtained uniformly mixed fine powder into shape to obtain a green plate for sintering; (4) Place the green plate for sintering in a vacuum reaction sintering furnace for high-temperature reaction sintering at a sintering temperature of 1500-1800℃ and a sintering time of 2-5 h to obtain a nano-silicon reaction sintered silicon carbide sintering plate.

2. The method for preparing the nano-silicon reaction sintered silicon carbide sintering plate as described in claim 1, characterized in that, The silicon carbide powder is a multi-particle-size graded silicon carbide powder, including coarse silicon carbide particles with a particle size of 10-30 μm, medium silicon carbide particles with a particle size of 3-10 μm, and fine silicon carbide particles with a particle size of 0.5-3 μm. The mass percentages of coarse silicon carbide, medium silicon carbide, and fine silicon carbide particles in the total mass of the raw materials are 25-45 wt%, 15-25 wt%, and 15-25 wt%, respectively.

3. The method for preparing the nano-silicon reaction-sintered silicon carbide sintering plate as described in claim 1, characterized in that, Biochar is selected from one or more of coconut shell charcoal, corn cob charcoal, bamboo charcoal, and rice husk charcoal.

4. The method for preparing the nano-silicon reaction sintered silicon carbide sintering plate as described in claim 1, characterized in that, Step (1) uses anhydrous ethanol or isopropanol as the ball milling medium, and the mass ratio of the ball milling medium to the raw material is (3-6):

1.

5. The method for preparing the nano-silicon reaction sintered silicon carbide sintering plate as described in claim 1, characterized in that, In step (1), the ball mill speed is 80-300 r / min and the ball milling time is 2-10 h.

6. The method for preparing the nano-silicon reaction sintered silicon carbide sintering plate as described in claim 1, characterized in that, In step (2), the drying temperature is 60-120℃ and the drying time is 8-24 h.

7. The method for preparing the nano-silicon reaction sintered silicon carbide sintering plate as described in claim 1, characterized in that, In step (3), the molding pressure is 100-200 MPa and the holding time is 10-90 s.

8. The method for preparing the nano-silicon reaction-sintered silicon carbide sintering plate according to any one of claims 1-7, characterized in that, During the sintering process, nano-silicon powder reacts in situ with biomass char to generate silicon carbide and induces the formation of silicon carbide whiskers. The length of the silicon carbide whiskers is 1-25 μm and the diameter is 50-500 nm.

9. The method for preparing the nano-silicon reaction-sintered silicon carbide sintering plate according to any one of claims 1-7, characterized in that, The resulting nano-silicon reaction-sintered silicon carbide substrate has a bulk density of 3.0-3.3 g / cm³. 3 The flexural strength is 400-480 MPa, and the fracture toughness is 5.2-5.9 MPa·m. 1 / 2 .

10. The nano-silicon reaction sintered silicon carbide sintering plate obtained by any one of the preparation methods described in claims 1-7.

Images