Graphite composite material, method for preparing the same, and use thereof

Abstract

The application relates to a graphite composite material and a preparation method and application thereof. The preparation raw materials of the graphite composite material include 55-75% carbon-based aggregate, 15-25% pore-forming agent and 15-30% polyamide acid in percentage by mass. The graphite composite material includes the carbon-based aggregate, the pore-forming agent and the polyamide acid in a specific proportion, so that the graphite composite material has excellent tensile strength, bending strength and through-hole rate, and can improve the efficiency of removing carbon inclusions in the growth of silicon carbide crystals.

Description

Technical Field

[0001] This application relates to the field of materials, and in particular to a graphite composite material, its preparation method, and its application. Background Technology

[0002] Silicon carbide (SiC) crystal is a representative material of third-generation wide-bandgap semiconductors, characterized by its large bandgap, high critical breakdown electric field, high carrier saturation migration velocity, high thermal conductivity, and good chemical stability. It has wide applications in microelectronics and optoelectronics. Currently, the vapor phase transport (PVT) method is the most mature and the only method that can meet the requirements for commercially available silicon carbide substrates.

[0003] In the PVT process for producing SiC crystals, carbon particles generated by the volatilization of SiC powder are easily transported to the crystal surface by the gas flow and enter the crystal during growth, creating so-called "carbon inclusions" and inducing microtubes or dislocation defects. This is a significant factor contributing to poor crystal growth quality. Therefore, traditional techniques typically use porous graphite separators to filter the silicon carbide crystal growth atmosphere, blocking tiny carbon particles and thus improving the quality of the resulting SiC crystals. In the early stages of production, the porous graphite separator, as a porous material, can adjust the silicon atmosphere content, i.e., adjust the Si / C ratio, suppressing silicon droplet formation and improving crystal quality. However, porous graphite separators produced by traditional processes inevitably exhibit residual carbon and aggregate pulverization during high-temperature use, making them a new source of "carbon inclusions," further affecting the quality of silicon carbide single crystals.

[0004] Therefore, traditional technologies still need improvement. Summary of the Invention

[0005] Therefore, it is necessary to provide a graphite composite material with excellent tensile strength, flexural strength, and porosity, as well as its preparation method and application. The specific solution is as follows:

[0006] This application provides a graphite composite material, wherein the raw materials for preparing the graphite composite material, by weight percentage, include: 55%~75% carbon-based aggregate, 15%~25% pore-forming agent, and 15%~30% binder, wherein the binder includes polyamic acid.

[0007] In one embodiment, the pore-forming agent includes at least one of walnut powder, PVB, ammonium bicarbonate, sodium chloride, benzoic acid, PVP, PVA, PS microspheres, and PMMA microspheres.

[0008] In one embodiment, the carbon-based aggregate has a particle size of 50 μm to 300 μm; and / or

[0009] The carbon-based aggregate includes needle coke.

[0010] This application also provides a method for preparing graphite composite materials, comprising the following steps:

[0011] The raw materials and solvents for preparing graphite composite materials as described above are mixed to prepare a mixed slurry;

[0012] The mixed slurry is subjected to molding, carbonization and graphitization processes in sequence to prepare a graphite composite material.

[0013] In one embodiment, prior to the molding process, the mixture is further subjected to a drying process, wherein the drying process satisfies at least one of the following conditions (1) to (2):

[0014] (1) The drying temperature is 40℃~180℃;

[0015] (2) The drying time is 20 min to 60 min.

[0016] In one embodiment, the drying process includes the following steps:

[0017] The mixed slurry is subjected to a first drying treatment at 40℃~45℃ for 8min~12min to obtain a first dried slurry;

[0018] The first dried slurry is subjected to a second drying treatment at 50℃~55℃ for 18min~22min to obtain a second dried slurry;

[0019] The second dried slurry is subjected to a third drying treatment at 70℃~75℃ for 18min~22min to obtain the dried slurry, which is then subjected to molding treatment.

[0020] In one embodiment, the molding process satisfies at least one of the conditions (1) to (3):

[0021] (1) The pressure of the molding process is 0.5 MPa to 10 MPa;

[0022] (2) The molding process temperature is 260℃~300℃;

[0023] (3) The molding process takes 20 min to 90 min.

[0024] In one embodiment, the carbonization process includes the following steps:

[0025] The slurry after the molding process is subjected to a first calcination treatment at a constant temperature of 300℃~400℃ for 10h~15h to obtain the first calcined slurry.

[0026] The first calcining slurry was subjected to a second calcination treatment at a constant temperature of 450℃~650℃ for 20h~30h to obtain the second calcining slurry.

[0027] The second calcined slurry was subjected to a third calcination treatment at a constant temperature of 700℃~1100℃ for 50h~90h to obtain the third calcined slurry.

[0028] In one embodiment, the graphitization process satisfies at least one of the conditions (1) to (3):

[0029] (1) The temperature of the graphitization treatment is 2000℃~2300℃;

[0030] (2) The graphitization treatment time is 20h~70h;

[0031] (3) After the carbonization step and before the graphitization step, the following steps are also included:

[0032] Inert gas is introduced and the temperature is raised to 1700℃~1900℃, then purified gas is introduced for purification treatment;

[0033] Optionally, the purified gas includes at least one of Freon and chlorine.

[0034] This application also provides a method for preparing silicon carbide material, comprising the following steps:

[0035] Silicon carbide was prepared on a separator using a vapor-phase transport method.

[0036] The partition comprises a graphite composite material as described above or a graphite composite material prepared by the method described above.

[0037] The method for preparing the graphite composite material of this application includes carbon-based aggregates, pore-forming agents, and binders in a specific ratio, wherein the binder includes polyamic acid. Polyamic acid is selected as the binder component because, on the one hand, it has good miscibility with the carbon-based aggregates, enabling the components to form a good adhesive system, thereby improving the mechanical strength of the graphite composite material; on the other hand, it solidifies during sintering and transforms into a high-temperature resistant, dense polyimide film. Therefore, the aforementioned graphite composite material, on the one hand, allows the polyimide film to encapsulate the carbon-based aggregates, reducing... The low probability of graphite composite material itself pulverizing and forming carbon inclusions that detach from the graphite composite material; on the other hand, the addition of a certain pore-forming agent increases the porosity of the graphite composite material, making the pore size distribution uniform and the components coordinated, so that the graphite composite material has excellent tensile strength, flexural strength and porosity. When used as a separator to prepare silicon carbide, it can maintain good mechanical properties during silicon carbide crystal growth, is not easy to pulverize and can reduce the probability of graphite composite material itself pulverizing and forming carbon inclusions that detach from the graphite composite material, thereby reducing the probability of carbon inclusions appearing. Attached Figure Description

[0038] Figure 1 The image shows the metallographic results of the graphite composite material prepared in Example 1. Detailed Implementation

[0039] To facilitate understanding of this application, a more complete description is provided below, along with preferred embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] The terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element preceded by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The indefinite articles “a” and “an” preceding an element or component in this application are not restrictive in terms of the quantity (i.e., the number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and singular elements or components also include plural forms, unless the quantity clearly refers only to the singular. “A plurality” means at least two, such as two, three, etc., unless otherwise expressly specified.

[0042] Unless otherwise shown or indicated in the operational embodiments, all figures used to represent the amounts, physicochemical properties, etc., of ingredients in the specification and claims are to be understood to be adjusted by the term "about" in all cases. For example, therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired characteristics by utilizing the teachings disclosed herein. The use of numerical ranges indicated by endpoints includes all numbers within that range and any range within that range; for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0043] In traditional techniques, the aggregate in porous graphite separators inevitably pulverizes during high-temperature use. Technicians proposed using binders to bond the aggregates and prepare graphite composites. However, further research and development revealed that graphitization of the binder leaves behind numerous pores and residual carbon, making porous graphite separators a new source of "carbon encapsulation."

[0044] Therefore, through extensive creative experimental research, the applicant discovered that using polyamic acid as a binder component has several advantages. First, polyamic acid has good miscibility with carbon-based aggregates, enabling the components to form a good adhesive system, thereby improving the mechanical strength of graphite composites. Second, during sintering, it solidifies and transforms into a high-temperature resistant, dense polyimide film. By controlling the specific proportions of specific components in the graphite composite, the graphite composite possesses excellent tensile strength, flexural strength, and porosity. When used as a separator in the preparation of silicon carbide, it can maintain good mechanical properties during silicon carbide crystal growth, is less prone to pulverization, and reduces the probability of carbon inclusions detaching from the graphite composite due to pulverization, thus reducing the likelihood of carbon inclusions appearing.

[0045] One embodiment of this application provides a graphite composite material, wherein the raw materials for preparing the graphite composite material include, by mass percentage: 55%~75% carbon-based aggregate, 15%~25% pore-forming agent, and 15%~30% binder, wherein the binder includes polyamic acid.

[0046] The method for preparing the graphite composite material of this application includes carbon-based aggregates, pore-forming agents, and binders in a specific ratio, wherein the binder includes polyamic acid. Polyamic acid is selected as the binder component because, on the one hand, it has good miscibility with the carbon-based aggregates, enabling the components to form a good adhesive system, thereby improving the mechanical strength of the graphite composite material; on the other hand, it solidifies during sintering and transforms into a high-temperature resistant, dense polyimide film. Therefore, the aforementioned graphite composite material, on the one hand, allows the polyimide film to encapsulate the carbon-based aggregates, reducing... The low probability of graphite composite material itself pulverizing and forming carbon inclusions that detach from the graphite composite material; on the other hand, the addition of a certain pore-forming agent increases the porosity of the graphite composite material, making the pore size distribution uniform and the components coordinated, so that the graphite composite material has excellent tensile strength, flexural strength and porosity. When used as a separator to prepare silicon carbide, it can maintain good mechanical properties during the growth of silicon carbide crystals, is not easy to pulverize and can reduce the probability of graphite composite material itself pulverizing and forming carbon inclusions that detach from the graphite composite material, thereby reducing the probability of carbon inclusions appearing.

[0047] It is understood that when a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0048] It should be noted that the value range of carbon-based aggregate is "55%~75%", that is, the minimum and maximum values ​​within the range of 55%~75%, as well as every value between these minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 55%, 55.5%, 56%, 56.5%, 57%, 57.5%, 58%, 58.5%, 59%, 59.5%, 60%, 60.5%, 61%, 61.5%, 62%, 62.5%, 63%, 63.5%, 64%, 64.5%, 65%, 65.5%, 66%, 66.5%, 67%, 67.5%, 68%, 68.5%, 69%, 69.5%, 70%, 70.5%, 71%, 71.5%, 72%, 72.5%, 73%, 73.5%, 74%, 74.5%, or 75%; or any range consisting of any two of these values.

[0049] The pore-forming agent has a value range of "15%~25%", which means it can take the minimum and maximum values ​​within the range of 15%~25%, as well as every value between these minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5% or 25%; or any range consisting of any two of these values.

[0050] It is understandable that the purpose of adding pore-forming agents is to form a porous structure. If too much pore-forming agent is added, it will affect the structural stability of the graphite composite material and reduce the mechanical properties of the composite. If too little pore-forming agent is added, there will be too few pores, which will affect the efficiency of gaseous material flow through in the subsequent preparation of silicon carbide materials.

[0051] The adhesive value ranges from 15% to 30%, meaning it can be the minimum and maximum value within this range, as well as every value between these values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, or 35%; or any range consisting of any two of these values.

[0052] Understandably, the purpose of adding polyamic acid binder is to facilitate the molding of carbon-based aggregates under pressure. If too much binder is added, the binder will form an overly dense polyimide film, affecting the efficiency of gaseous material flow through in the subsequent preparation of silicon carbide materials. If too little binder is added, it will result in failure to bond, and the resulting graphite composite material will be easily broken.

[0053] In some embodiments, the pore-forming agent includes at least one of walnut powder, polyvinyl butyral (PVB), ammonium bicarbonate, sodium chloride, benzoic acid, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polystyrene (PS) microspheres, and polymethyl methacrylate (PMMA) microspheres.

[0054] In some embodiments, the particle size of the carbon-based aggregate is 50 μm to 300 μm.

[0055] By controlling the particle size of the aforementioned carbon-based aggregates, the carbon-based aggregates can be easily molded under certain pressure.

[0056] In some embodiments, the carbon-based aggregates described above include needle coke.

[0057] This application also provides a method for preparing graphite composite materials, including steps S10 to S20.

[0058] Step S10: Mix the above-mentioned raw materials and solvents for preparing graphite composite materials to prepare a mixed slurry.

[0059] In some embodiments, the solvent includes at least one of N,N-dimethylacetamide, hexafluoroisopropanol, and dimethyl sulfoxide.

[0060] Step S20: The above mixed slurry is subjected to molding treatment, carbonization treatment and graphitization treatment in sequence to prepare graphite composite material.

[0061] In some embodiments, the mixture is dried prior to the molding process.

[0062] In some embodiments, the temperature of the drying process described above is 40°C to 180°C.

[0063] It is understood that when a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0064] The drying temperature range is "40℃~180℃", which includes the minimum and maximum values ​​within the range of 40℃~180℃, as well as every value between these values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, or 180℃; or any range consisting of any two of these values.

[0065] In some embodiments, the drying time is 20 min to 60 min.

[0066] The drying time ranges from 20 min to 60 min, specifically the minimum and maximum values ​​within this range, as well as every value between them. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 31 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, 46 min, 47 min, 48 min, 49 min, 50 min, 51 min, 52 min, 53 min, 54 min, 55 min, 56 min, 57 min, 58 min, 59 min, or 60 min; or any range consisting of any two of these values.

[0067] In a specific example, the drying process described above includes steps a, b, and c.

[0068] Step a: The mixed slurry is subjected to a first drying treatment at 40℃~45℃ for 8min~12min to obtain the first dried slurry.

[0069] Step b: The first dried slurry is subjected to a second drying treatment at 50℃~55℃ for 18min~22min to obtain the second dried slurry.

[0070] Step c: The second dried slurry is subjected to a third drying treatment at 70℃~75℃ for 18min~22min to obtain the dried slurry, which is then subjected to molding treatment.

[0071] In some embodiments, the pressure of the above molding process is 0.5 MPa to 10 MPa.

[0072] It should be noted that the pressure range for the molding process is "0.5 MPa to 10 MPa", which includes the minimum and maximum values ​​within the range of 0.5 MPa to 10 MPa, as well as every value between these two values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, or 10 MPa; or any range consisting of any two of these values.

[0073] In some embodiments, the temperature of the molding process described above is 260°C to 300°C.

[0074] The temperature range for the molding process is "260℃~300℃", which includes the minimum and maximum values ​​within the range of 260℃~300℃, as well as every value between these values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 290℃, 295℃, or 300℃; or any range consisting of any two of these values.

[0075] In some embodiments, the molding process takes 20 to 90 minutes.

[0076] The temperature range for the molding process is "20 min to 90 min", which includes the minimum and maximum values ​​within this range, as well as every value between these values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, or 90 min; or any range consisting of any two of these values.

[0077] In some embodiments, the carbonization process described above includes steps a, b, and c.

[0078] Step a: The slurry after molding is subjected to a first calcination treatment at a constant temperature of 300℃~400℃ for 10h~15h to obtain the first calcined slurry.

[0079] Step b: The first calcined slurry is subjected to a second calcination treatment at a constant temperature of 450℃~650℃ for 20h~30h to obtain the second calcined slurry.

[0080] Step c: The second calcination slurry is subjected to a third calcination treatment at a constant temperature of 700℃~1100℃ for 50h~90h to obtain the third calcination slurry, which is then subjected to graphitization treatment.

[0081] In some embodiments, the temperature of the graphitization process is 2000°C to 2300°C.

[0082] It should be noted that the temperature range for graphitization treatment is "2000℃~2300℃", which includes the minimum and maximum values ​​within the range of 2000℃~2300℃, as well as every value between these two values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 2000℃, 2050℃, 2100℃, 2150℃, 2200℃, 2250℃, 2300℃, 2350℃, 2400℃, 2450℃, 2500℃, 2550℃, 2600℃, 2650℃, 2700℃, 2750℃, 2800℃, 2850℃, 2900℃, 2950℃, or 2300℃; or any range consisting of any two of these values.

[0083] In some embodiments, the graphitization process is carried out for 20 to 70 hours.

[0084] The graphitization treatment time ranges from 20h to 70h, specifically the minimum and maximum values ​​within this range, as well as every value between these values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, or 70h; or any range consisting of any two of these values.

[0085] In some embodiments, after the carbonization step and before the graphitization step, an inert gas is introduced to raise the temperature to 1700°C~1900°C, and a purification gas is introduced for purification.

[0086] In some embodiments, the purified gas includes at least one of Freon and chlorine.

[0087] In a specific example, the purification process includes purging with Freon for 2 to 7 hours, then heating to 2000°C to 2300°C, purging with chlorine for 7 to 9 hours, and then vacuum graphitizing at 2000°C to 2300°C for 20 to 30 hours.

[0088] It should be noted that the graphitization furnace used above can be a commonly used graphitization furnace in this field, such as a vacuum graphitization furnace.

[0089] In some of these embodiments, the absolute vacuum is 50 Pa to 150 Pa.

[0090] This application also provides a method for preparing silicon carbide material, including the step of preparing silicon carbide on a separator using a gas phase transport method, wherein the separator comprises the above-mentioned graphite composite material or a graphite composite material prepared by the above-mentioned method for preparing graphite composite material.

[0091] It is understandable that by using the gas-phase transport method to prepare silicon carbide materials on the separator, the aforementioned separator can maintain good mechanical properties during the growth of silicon carbide crystals and is not easy to pulverize, thereby reducing the probability of carbon inclusions.

[0092] The present application will be described below with reference to specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the appended claims summarize the scope of the present application. Under the guidance of the concept of the present application, those skilled in the art should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0093] To make the objectives, technical solutions, and advantages of this application clearer and more concise, the following specific embodiments are used for illustration, but this application is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of this application and can be used to describe this application, but should not be construed as limiting the scope of this application. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

[0094] Example 1

[0095] (1) The needle coke was screened by a vibrating sieve instrument, and needle coke with a size of 50 μm was selected as aggregate. It was then wet-mixed with polyamic acid, walnut powder and N,N-dimethylacetamide for 30 min to prepare a mixed slurry, in which needle coke was 55 wt%, polyamic acid was 30 wt% and walnut powder was 15 wt%.

[0096] (2) The well-stirred slurry is loaded into the mold by a certain weight and flattened. Then the mold is kept at 40°C for 10 minutes, then at 50°C for 20 minutes, and then at 70°C for 20 minutes to evaporate the solvent, so as to obtain the dried slurry.

[0097] (3) The dried slurry obtained in step (2) is directly heated to 280°C and a pressure of 1 MPa is applied to the mold for curing for 30 minutes to form the material and obtain the slurry after molding.

[0098] (4) Carbonize the slurry obtained in step (3) and calcine it under air-isolated conditions; wherein, the first stage is heated to 250°C for 2 hours; the second stage is heated to 650°C for 40 hours; the third stage is heated to 750°C for 6 hours and kept at a constant temperature for 4 hours to obtain the carbonized slurry.

[0099] (5) The carbonized slurry obtained in step (4) is subjected to graphitization treatment. First, under N2 protection, the temperature is raised from room temperature to 1900℃ and purified by purifying with Freon for 3h; then the temperature is raised to 2100℃ and purified by purifying with chlorine for 8h; then vacuum graphitization is carried out at 2300℃ for 20h. The absolute vacuum degree of the vacuum graphitization furnace is 100Pa to prepare graphite composite material.

[0100] (6) The prepared graphite composite material was subjected to the following performance tests.

[0101] 1. The tensile strength properties of the graphite composite materials prepared in the examples and comparative examples were tested using a universal mechanical instrument, specifically referring to the ISO 527-2 standard.

[0102] 2. The flexural strength of the graphite composite materials prepared in the examples and comparative examples was tested using a universal mechanical instrument, specifically in accordance with ISO 178 standard.

[0103] 3. The porosity of the graphite composite materials prepared in the examples and comparative examples was tested using the liquid saturation method, specifically referring to the ASTM D737 standard.

[0104] 4. The pore size of the graphite composite materials prepared in the examples and comparative examples was analyzed by metallographic testing. Specifically, the samples were prepared by cold mounting, and then the cold-mounted samples were polished. Finally, the plates were tested and analyzed by polarizing microscope.

[0105] The preparation methods of the graphite composite materials in Examples 2-6 are basically the same as those in Example 1, with the only difference being the relevant parameters in Table 1. The specific parameters and mixing slurry ratios are shown in Table 1 below.

[0106] The preparation methods of the graphite composite materials in Examples 7-9 are basically the same as those in Example 1, except for the relevant parameters in Table 2. The specific parameters and mixing ratio of the slurry are shown in Table 2 below.

[0107] The preparation methods of the graphite composite materials of Comparative Examples 1 and 2 are basically the same as those of Example 1, except for the relevant parameters in Table 2. The specific parameters and mixing slurry ratios are shown in Table 2 below.

[0108] Table 1

[0109]

[0110] Table 2

[0111]

[0112] Note: " / " indicates that the component does not exist.

[0113] Figure 1 The metallographic results of the graphite composite material prepared in Example 1 are shown in Tables 1-2. The tensile strength, flexural strength, porosity, and average pore size of the graphite composite materials in Examples 1-9 and Comparative Examples 1-3 are shown in Tables 1-2. It can be seen that the graphite composite material prepared in the examples of this application has higher tensile strength and flexural strength and higher porosity than the graphite composite material prepared in the comparative examples. When used as a separator to prepare silicon carbide, it can maintain good mechanical properties during the growth of silicon carbide crystals and is not easy to pulverize, thereby reducing the probability of carbon inclusions.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be defined by the appended claims.

Claims

1. A graphite composite material, characterized in that, The raw materials for preparing the graphite composite material, by mass percentage, include: 55%~75% carbon-based aggregate, 15%~25% pore-forming agent, and 15%~30% binder, wherein the binder is polyamic acid; the particle size of the carbon-based aggregate is 50μm~300μm. The carbon-based aggregate includes needle coke; the pore-forming agent includes at least one of walnut powder, PVB, ammonium bicarbonate, sodium chloride, benzoic acid, PVP, PVA, PS microspheres, and PMMA microspheres; the preparation method of the graphite composite material includes the following steps: The raw materials and solvents for preparing the graphite composite material are mixed to prepare a mixed slurry; The mixed slurry is subjected to molding, carbonization and graphitization processes in sequence to prepare a graphite composite material; the molding process is carried out at a pressure of 0.5 MPa to 10 MPa, a temperature of 260°C to 300°C and a time of 20 min to 90 min.

2. The graphite composite material as described in claim 1, characterized in that, Prior to the molding process, the mixture is further subjected to a drying process, wherein the drying process satisfies at least one of the following conditions (1) to (2): (1) The drying temperature is 40℃~180℃; (2) The drying time is 20 min to 60 min.

3. The graphite composite material as described in claim 2, characterized in that, The drying process includes the following steps: The mixed slurry is subjected to a first drying treatment at 40℃~45℃ for 8min~12min to obtain a first dried slurry; The first dried slurry is subjected to a second drying treatment at 50℃~55℃ for 18min~22min to obtain a second dried slurry; The second dried slurry is subjected to a third drying treatment at 70℃~75℃ for 18min~22min.

4. The graphite composite material according to any one of claims 1 to 3, characterized in that, The carbonization process includes the following steps: The slurry after the molding process is subjected to a first calcination treatment at a constant temperature of 300℃~400℃ for 10h~15h to obtain the first calcined slurry. The first calcining slurry was subjected to a second calcination treatment at a constant temperature of 450℃~650℃ for 20h~30h to obtain the second calcining slurry. The second calcined slurry was subjected to a third calcination treatment at a constant temperature of 700℃~1100℃ for 50h~90h to obtain the third calcined slurry, which was then subjected to graphitization treatment.

5. The graphite composite material according to any one of claims 1 to 3, characterized in that, The graphitization treatment satisfies at least one of the conditions in (1) to (3): (1) The temperature of the graphitization treatment is 2000℃~2300℃; (2) The graphitization treatment time is 20h~70h; (3) After the carbonization step and before the graphitization step, the following steps are also included: Inert gas is introduced and the temperature is raised to 1700℃~1900℃, then purified gas is introduced for purification.

6. The graphite composite material as described in claim 5, characterized in that, The purified gas includes at least one of Freon and chlorine.

7. A method for preparing silicon carbide material, characterized in that, Includes the following steps: Silicon carbide was prepared on a separator using a vapor-phase transport method. The partition comprises a graphite composite material as described in any one of claims 1 to 6.

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