Preparation method of sulfonated graphene reinforced antioxidant carbon graphite sealing material

Abstract

The invention discloses a sulfonated graphene enhanced antioxidant carbon graphite sealing material preparation method, which comprises: (1) carrying out surface treatment on a hexagonal boron nitride nanosheet by using an alkali liquid to obtain a surface hydroxylated hexagonal boron nitride nanosheet; (2) mixing and reacting the surface hydroxylated hexagonal boron nitride nanosheet and sulfonated graphene in a solvent, and collecting a reaction product to obtain mixed powder; (3) mixing the mixed powder, graphite powder and calcined coke aggregate to obtain composite aggregate powder; and (4) adding the composite aggregate powder into a mixing and kneading pot, adding asphalt, performing mixing and kneading treatment, performing sheet rolling and crushing to obtain pressed powder, and performing mold pressing and roasting treatment on the pressed powder to obtain the carbon-graphite sealing material. According to the preparation method, sulfonated graphene and hexagonal boron nitride are used for synergistic modification, so that the problems that antioxidant h-BN additive powder is non-uniformly dispersed in a carbon graphite material, the interface bonding strength of h-BN and a carbon graphite matrix material is poor, and thermal expansion coefficients are mismatched are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of carbon materials, and particularly relates to a preparation method of carbon graphite sealing material. BACKGROUND

[0002] Carbon graphite material is widely used in the sealing device of aero-engine due to its self-lubricating property, wear resistance, chemical stability and thermal shock resistance. However, in the oxidizing environment with a temperature exceeding 400℃, the active carbon atoms in the carbon graphite crystallite are prone to oxidation reaction, which causes the oxidation loss of the carbon graphite material. The oxidation loss of the carbon graphite mainly includes surface oxidation and pore oxidation in the internal structure. The surface oxidation mainly causes the uniform loss of the material surface, while the pore oxidation in the internal structure causes the material organization damage, loose structure, reduced thermal conductivity and performance, and poor use reliability. With the development of the aviation industry, the demand for the graphite sealing material for aero-engine is increasing, and the working conditions are becoming more and more severe. Therefore, ensuring the oxidation resistance of the carbon graphite material becomes the prerequisite for utilizing its excellent performance.

[0003] In order to improve the oxidation resistance of the carbon graphite product, in recent years, different research teams at home and abroad have carried out research on adding different additives in the production of carbon graphite material, which plays a certain promoting role in improving the oxidation resistance of the carbon graphite material. Hexagonal boron nitride (h-BN) has outstanding high-temperature oxidation resistance, thermal stability and thermal conductivity, can reduce the reaction dynamics of carbon and oxygen, and has a similar hexagonal crystal structure with graphite, and has good structural compatibility with graphite composite material. The oxidation of h-BN in the oxidation environment above 580℃ produces a glassy B2O3 film, which can effectively fill the pores and micro-cracks of the carbon graphite material, coat the oxidation active sites in the carbon graphite material, and prevent the oxidation of the carbon graphite material by oxygen. At the same time, h-BN has excellent self-lubricating property, and the self-lubricating property is not as dependent on the presence of gas and liquid medium as the graphite material, which can adapt to the high-temperature dry grinding working conditions.

[0004] As proposed in patent document CN117865675A, a high-temperature oxidation-resistant carbon graphite material for an aero-engine and a preparation method thereof are provided. An activator is used to build an active layer on the surface of carbon aggregate and h-BN. The carbon aggregate and h-BN are separately subjected to semi-coking treatment, then crushed and sieved to obtain modified powder. The modified powder and pitch are then put into a mixing pot for mixing and kneading. After rolling, crushing and sieving, a pressed powder is obtained. The pressed powder is subjected to mold pressing, baking and graphitization to obtain a carbon graphite block material with good mechanical properties and oxidation resistance. However, the surface of h-BN has few active groups and stable chemical activity. The compatibility of h-BN powder treated by conventional methods with carbon aggregate is poor. After the binder melts, it is difficult to uniformly distribute on the surface of the powder. Therefore, it is difficult to make h-BN and carbon graphite material present good combination effect. Moreover, the thermal expansion coefficients of the two materials are mismatched, which can easily cause congenital microcracks and develop into pores, so that a uniformly distributed B2O3 film with self-healing performance cannot be formed in a high-temperature oxidation environment, resulting in deviation of the homogeneity and oxidation resistance of the carbon graphite. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the above background art and to provide a preparation method of a sulfonated graphene reinforced oxidation-resistant carbon graphite sealing material with excellent high-temperature oxidation resistance.

[0006] To solve the above technical problems, the technical solution proposed by the present application is as follows: A preparation method of a sulfonated graphene reinforced oxidation-resistant carbon graphite sealing material, characterized in that it comprises the following steps: (1) Surface treatment of hexagonal boron nitride nanosheets with an alkali solution to obtain surface-hydroxylated hexagonal boron nitride nanosheets; (2) Mixing and reacting the surface-hydroxylated hexagonal boron nitride nanosheets and sulfonated graphene in a solvent to collect the reaction product to obtain a mixed powder; (3) Mixing the mixed powder, graphite powder and calcined coke aggregate to obtain a composite aggregate powder; (4) Adding the composite aggregate powder to a mixing pot and adding pitch for mixing and kneading treatment. The pressed powder obtained after rolling and crushing is subjected to mold pressing and baking treatment to obtain a carbon graphite sealing material.

[0007] In the above preparation method, preferably, the concentration of the alkali solution is 3-5 mol / L, and the alkali solution is a mixed solution of sodium hydroxide and potassium hydroxide. The surface treatment is stirring in an oil bath pot at 100-120℃ for 12-24h, then natural cooling, water washing 2-3 times and drying.

[0008] In the above preparation method, preferably, before mixing and reacting the surface-hydroxylated hexagonal boron nitride nanosheets and sulfonated graphene in a solvent, the surface-hydroxylated hexagonal boron nitride nanosheets and sulfonated graphene are first placed in an N,N-dimethylformamide solution and subjected to low-temperature plasma treatment in an argon atmosphere. After washing and drying, they are then mixed and reacted in anhydrous ethanol solvent. During the low-temperature plasma treatment, the treatment temperature is controlled at 40-60℃, the treatment time is 20-40 min, and the radio frequency power is 10-15 MHz. The treatment temperature of 40-60℃ can avoid thermal damage to the material due to excessive temperature. Low-temperature treatment can ensure that free radicals and ions in the plasma can effectively perform physical etching and chemical reactions on the material surface, while ensuring the integrity of the material. The treatment time is 20-40 min for the following reasons: Maintaining the treatment time at 20-40 min allows the free radicals to complete the etching effect, increasing the surface roughness of h-BN-OH and sulfonated graphene, and increasing the number of active reaction sites. Too short a treatment time may lead to insufficient surface modification, while too long a time may cause over-etching, affecting the surface properties of the material. A radio frequency power of 10-15MHz can effectively excite argon gas to form a stable low-temperature plasma, enabling high-energy electrons and ions in the plasma to undergo efficient physical and chemical reactions with the material surface, while avoiding damage to the material from high temperatures.

[0009] In the above preparation method, preferably, the collected reaction products are further subjected to vacuum heat treatment. The vacuum heat treatment involves placing the reaction products in a vacuum heat treatment furnace, slowly heating them to 100-120°C at a rate of 5-10°C / min, holding them at that temperature for 1-2 hours, and then cooling them with high-purity nitrogen for 15-30 minutes.

[0010] In the above preparation method, preferably, the hexagonal boron nitride nanosheets have 5-30 layers and a thickness of 5-30 nm.

[0011] In the above preparation method, preferably, the mass ratio of the surface-hydroxylated hexagonal boron nitride nanosheets to sulfonated graphene is (2-4):(1-3). Hydroxylated boron nitride primarily acts as an oxidation inhibitor to improve the material's antioxidant properties, while sulfonated graphene acts as a reinforcing agent and dispersant. On the one hand, it improves the dispersibility of the mixed powder with hydroxylated boron nitride; on the other hand, it enhances the physical properties of the composite material. This ratio ensures high mechanical strength while also achieving a certain degree of dispersibility, which is quite reasonable. If the mixing ratio is not correct, the overall performance of the composite material is poor.

[0012] In the above preparation method, preferably, the mixing reaction is carried out by ultrasonic oscillation in a water bath at 40-60℃ for 10-12 hours, followed by magnetic stirring at 500-800 r / min for 1-2 hours. The grafting reaction of hydroxylated boron nitride and sulfonated graphene is carried out under these conditions. On the one hand, the agglomeration of sulfonated graphene is avoided by ultrasonic treatment; on the other hand, treatment in anhydrous ethanol at 40-60℃ avoids damaging the structure of both materials, achieving effective grafting.

[0013] In the above preparation method, preferably, the graphite powder is natural graphite powder or artificial graphite powder with a particle size D50 of 5-7 μm; the particle size D50 of the calcined coke aggregate is 8-12 μm; the graphite powder and calcined coke aggregate are first dried at 110-150℃ using a vacuum drying system to remove some air and moisture from their surfaces and pores.

[0014] In the above preparation method, preferably, the mass ratio of the mixed powder, graphite powder, and calcined coke aggregate is (1-8):(9-12):(80-90). The mixed powder is used as an additive for modification. If the amount of mixed powder is too small, it cannot effectively change the chemical properties and physical structure of the graphite material. At the same time, too little modifier will result in uneven dispersion in the matrix, leading to segregation of the composite material and poor overall performance. If the amount of mixed powder is too large, it may cause the graphite particles to agglomerate, destroy the layered structure of graphite, and reduce its mechanical properties.

[0015] In the above preparation method, preferably, the process involves adding asphalt and kneading, followed by rolling and crushing to obtain pressed powder, including the following steps: first, dry mixing at 110-140℃ for 1-2 hours to remove moisture, then continuing to raise the temperature to 160-180℃, adding molten modified coal tar pitch at a mass ratio of (62-70):(30-38), maintaining the kneading temperature at 185-200℃, kneading speed at 30-50 rpm, kneading for 0.5-2 hours, then hot rolling at 180-200℃ 3-5 times, and after cooling to room temperature, crushing and passing through a 160-325 mesh sieve to obtain pressed powder.

[0016] In the above preparation method, preferably, the molding and calcination treatment includes the following steps: After the powder is pressed into shape at 1-3 MPa, it is left to stand for 10-20 hours. Then, the green body is vacuum sealed with aluminum-plastic film and preheated in an oven at 80-120℃ for 2-10 hours. At the same time, the hydraulic oil of the isostatic press is heated to 80-120℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated green body in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 150-200 MPa to prepare the carbon graphite material green body. Carbon graphite material green body is placed in a graphite crucible. After the six sides of the green body are filled with calcining material, it is placed in a tube furnace. Argon / nitrogen gas is introduced during the calcination process. The green body is calcined at 1000-1200℃ for 4-10 hours. After the temperature is controlled by the program to drop to 100-300℃, it is naturally cooled to room temperature to obtain calcined graphite block. After treating the calcined graphite blocks in a graphitization furnace at 2000-3000℃ for 1-5 hours, the temperature is then controlled by a program to cool down to 100-300℃, and then naturally cooled to room temperature to obtain carbon graphite sealing material.

[0017] This invention addresses the challenge of poor high-temperature oxidation resistance in carbon-graphite materials, which limits their high-temperature performance. It proposes using sulfonated graphene and hexagonal boron nitride to enhance the oxidation resistance of carbon-graphite materials. Sulfonated graphene is grafted onto hydroxylated boron nitride as an additive, improving the dispersibility of the mixed powder and enhancing the physical properties of the composite material. This effectively improves both oxidation resistance and physical properties. Specifically, the abundant functional groups on the surface of sulfonated graphene can solve the problems of uneven dispersion of the antioxidant h-BN and poor interfacial bonding strength between pitch and BN. h-BN can shrink and densify synchronously with the carbon material components. As a reinforcing agent, during sintering, the surface functional groups of sulfonated graphene easily break, adsorbing free radicals generated during the thermal decomposition of modified coal tar pitch. This effectively avoids chain reactions such as microcrack propagation caused by these free radicals, increases the heat uniformity of heat-treated products, and thus improves the thermal shock resistance and mechanical strength of carbon-graphite sealing materials. Sulfonated graphene can mitigate microcracks and defects caused by thermal stress and mechanical deformation, improve the flexural strength, compressive strength and bulk density of the product, and ultimately produce carbon-graphite materials with uniform h-BN particle distribution, good interfacial bonding strength with carbon materials and excellent oxidation resistance.

[0018] Specifically, this invention, from a surface chemistry perspective, utilizes hexagonal boron nitride nanosheets with oxygen-containing functional groups such as hydroxyl groups on their surface after treatment. The numerous carboxyl, epoxy, and sulfonic acid groups on the sulfonated graphene framework readily undergo dehydration condensation grafting onto the hydroxyl groups on the modified BN nanosheets, forming a three-dimensional interface structure through strong chemical bonds. The -OH groups in the hydroxylated boron nitride exhibit hydrophilicity, as do the -SO3H groups in the sulfonated graphene, improving the dispersibility and compatibility of the mixed powder in aggregates. This allows for better and more uniform mixing with other aggregates and enhances the wettability of modified coal tar pitch with aggregates, thereby reducing agglomeration of the mixed powder during kneading and achieving simultaneous shrinkage and densification during subsequent calcination. Low-temperature plasma treatment further enhances the surface activity of both materials, followed by a grafting reaction that enables surface interactions through hydrogen and covalent bonds. Simultaneously, the formation of hydrogen bonds and covalent bonds effectively prevents the aggregation of the two sheet materials. Furthermore, hydrogen bonds and covalent bonds act as a "bridge" and "anchor," allowing the mixed powder to be effectively dispersed in the matrix material. (Hydrogen bonds and covalent bonds connect sulfonated graphene and hydroxylated boron nitride sheet materials, forming an ordered network structure in the mixed powder, preventing aggregation and disordered stacking between sheet materials. This also keeps the distance between sheet materials stable, avoiding re-aggregation due to electrostatics or van der Waals forces. The anchoring effect restricts the free movement of sheet materials in the matrix material, resulting in a uniform distribution within the matrix. It also strengthens the interfacial bonding between the sheet materials and the matrix material, preventing interfacial separation due to stress concentration.) Furthermore, the mixed powder formed by grafting hydroxylated boron nitride and sulfonated graphene retains the thermal conductivity of sulfonated graphene while possessing the low thermal expansion of boron nitride. When applied to graphite matrix materials, it can effectively reduce the overall system's coefficient of thermal expansion, improve interfacial thermal conduction, and reduce the accumulation of thermal stress. At the same time, the chemical bonds formed by the grafting reaction can further improve the interfacial stability of the matrix material, thus stabilizing the overall coefficient of thermal expansion.

[0019] To better ensure the synergistic effect of sulfonated graphene and hexagonal boron nitride, this invention employs low-temperature plasma treatment and vacuum heat treatment before and after their reaction, respectively. In argon atmosphere, free radical bombardment and physical etching increase the surface roughness of hydroxylated boron nitride and sulfonated graphene, increasing the number of active reaction sites and laying a foundation for subsequent grafting reactions. Then, vacuum heat treatment promotes the formation of chemical bonds between h-BN-OH and sulfonated graphene, improving the chemical stability of the interface and further optimizing the interface structure. This further strengthens covalent bonds, resulting in a stronger bond between the mixed powder and the graphite matrix. The introduction of covalent bonds also leads to a more uniform stress distribution in the interface region, reducing local stress concentration. Simultaneously, the vacuum environment prevents oxidation of the mixed powder surface, maintaining surface chemical activity and promoting element diffusion within the mixed powder, further optimizing the interface structure.

[0020] Compared with the prior art, the advantages of the present invention are as follows: The present invention discloses a method for preparing an antioxidant carbon graphite sealing material reinforced with sulfonated graphene. This method utilizes the synergistic modification of sulfonated graphene and hexagonal boron nitride to solve the problems of uneven dispersion of the antioxidant h-BN additive powder in the carbon graphite material, poor interfacial bonding strength between h-BN and the carbon graphite matrix material, and mismatch of thermal expansion coefficients. At the same time, it improves the flexural strength, compressive strength, and bulk density of the carbon graphite material, resulting in a final product with excellent antioxidant and mechanical properties. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The image shows the infrared spectrum of h-BN hydroxylation.

[0023] Figure 2 This is a schematic diagram showing the connection between hydroxylated h-BN and sulfonated graphene.

[0024] Figure 3 The diagrams show the flexural and compressive strength of the graphite material prepared in Example 1, along with the corresponding cross-sectional and surface microstructure diagrams.

[0025] Figure 4 The diagrams show the flexural and compressive strength of the graphite material prepared in Comparative Example 1, along with the corresponding cross-sectional and surface microstructure diagrams.

[0026] Figure 5The diagrams show the flexural and compressive strength of the graphite material prepared in Comparative Example 2, along with the corresponding cross-sectional and surface microstructure diagrams.

[0027] Figure 6 The diagrams show the flexural and compressive strength of the graphite material prepared in Comparative Example 3, along with the corresponding cross-sectional and surface microstructure diagrams. Detailed Implementation

[0028] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0029] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0031] Example 1: A method for preparing a sulfonated graphene-reinforced antioxidant carbon graphite sealing material includes the following steps: 1) Hexagonal boron nitride nanosheets (h-BN) were added to a 5 mol / L mixed solution of sodium hydroxide and potassium hydroxide (1:1), ultrasonically stirred in an oil bath at 120°C for 24 h, naturally cooled, washed with water and filtered three times, and dried in a vacuum drying oven at 80°C for 12 h to obtain surface-hydroxylated h-BN nanosheets.

[0032] 2) The surface-hydroxylated h-BN nanosheets and sulfonated graphene obtained in step 1) were placed in N,N-dimethylformamide (DMF) solution and subjected to low-temperature plasma treatment under argon atmosphere at 50°C for 30 min with a radio frequency power of 12 MHz. After washing and drying, they were mixed in anhydrous ethanol at a mass ratio of 2:1. After ultrasonic oscillation in a water bath at 60°C for 12 h, magnetic stirring at 800 r / min for 2 h, centrifugation, filtration and washing three times, the mixed powder after grafting reaction was placed in a vacuum heat treatment furnace and slowly heated to 120°C at a rate of 10°C / min, held at that temperature for 1 h, and then cooled with high-purity nitrogen for 30 min. The mixture was then ground into powder to obtain a mixed powder of surface-grafted modified h-BN and sulfonated graphene.

[0033] 3) Natural graphite powder or artificial graphite powder with a particle size D50 of 5μm and calcined coke aggregate with a D50 of 12μm were prepared using Raymond mill and high-energy air jet mill. Some air and moisture in the surface and pores were removed by vacuum drying system at 110℃.

[0034] 4) The mixed powder obtained in step 2) and the natural graphite powder or artificial graphite powder and calcined coke aggregate obtained in step 3) are added to a mixer in a mass ratio of 5:10:85 and mixed for 1 hour to obtain composite aggregate powder.

[0035] 5) Add the composite aggregate powder prepared in step 4) into a kneading pot, dry mix at 110℃ for 1 hour to remove moisture, continue to heat to 150℃, add molten modified coal tar pitch at a mass ratio of 64:36, maintain the kneading temperature at 190℃ and the kneading speed at 50 r / min, knead for 1.5 hours, hot roll the powder at 190℃ 3 times, after cooling to room temperature, crush it, and pass it through a 200 mesh sieve to obtain compressed powder.

[0036] 6) After the powder prepared in step 5) is molded at 1 MPa, it is left to stand for 10 hours. Then, the blank is vacuum-sealed with aluminum-plastic film and preheated in an oven at 110℃ for 10 hours. At the same time, the pressure medium (hydraulic oil) of the isostatic press is heated to 110℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated blank in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 200 MPa to obtain a powder with a density of 1.60 g / cm³. 3 Carbon graphite material green body.

[0037] 7) Place the carbon-graphite material green body prepared in step 6) into a graphite crucible. After the six sides of the green body are filled with calcining material, place it in a tube furnace. During the calcination process, argon / nitrogen gas is introduced, and the furnace is calcined at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.68 g / cm³. 3 Calcinated carbon graphite blocks.

[0038] 8) The carbon-graphite material obtained in step 7) was treated at 2500℃ for 4 hours in a graphitization furnace, then the temperature was controlled to decrease to 200℃ and then allowed to cool naturally to room temperature, resulting in a material with a density of 1.82 g / cm³. 3 Graphitized bulk material.

[0039] Infrared spectra of surface-hydroxylated h-BN nanosheets are shown below. Figure 1 As shown, Figure 1 The results show that h-BN has two typical characteristic peaks, namely the BN stretching peak (1388 cm⁻¹). -1 ) and curved peak (812cm) -1 While h-BN-OH showed a new hydroxyl peak (3210 cm⁻¹),-1 This is because the -OH generated by hydrolysis is grafted onto the BN surface, which is an important manifestation of hydroxylation.

[0040] Figure 2 The diagram shows the effective grafting of sulfonated graphene and hydroxylated boron nitride. The first step is the hydroxylation process of boron nitride. Under the action of a strong alkali, the modified hydroxylated boron nitride is obtained by ultrasonic stirring. The second step is the grafting of hydroxylated boron nitride with sulfonated graphene. Both -OH and -SO3H are hydrophilic and combine with each other to form chemical bonds, thus achieving effective grafting.

[0041] The test results of the flexural strength and compressive strength of the carbon-graphite material obtained in this embodiment are as follows: Figure 3 (a) and Figure 3 As shown in (c), the cross-sectional and surface microstructures of the carbon-graphite material are shown in the following figures. Figure 3 (b) and Figure 3 As shown in (d), by Figure 3 (a) and Figure 3 As shown in (c), the flexural strength and compressive strength of the graphite material are 69.46 MPa and 121.15 MPa, respectively, which represent a significant improvement in performance compared to carbon-graphite materials prepared by traditional processes. The corresponding microstructure diagrams show that the aggregates are tightly connected, exhibiting high density, and the pores between particles are small, with no cracks forming.

[0042] Example 2: A method for preparing a sulfonated graphene-reinforced antioxidant carbon graphite sealing material includes the following steps: 1) Hexagonal boron nitride nanosheets (h-BN) were added to a 5 mol / L mixed solution of sodium hydroxide and potassium hydroxide (1:1), ultrasonically stirred in an oil bath at 120°C for 24 h, naturally cooled, washed with water and filtered three times, and dried in a vacuum drying oven at 80°C for 12 h to obtain surface-hydroxylated h-BN nanosheets.

[0043] 2) The surface-hydroxylated h-BN nanosheets and sulfonated graphene obtained in step 1) were mixed in anhydrous ethanol at a mass ratio of 2:1. After ultrasonic oscillation in a water bath at 60°C for 12 h, the mixture was magnetically stirred at 800 r / min for 2 h, centrifuged, filtered, washed three times, and then ground into powder to obtain a mixed powder of surface-grafted modified h-BN and sulfonated graphene.

[0044] 3) Natural graphite powder or artificial graphite powder with a particle size D50 of 5μm and calcined coke aggregate with a D50 of 12μm were prepared using Raymond mill and high-energy air jet mill. Some air and moisture in the surface and pores were removed by vacuum drying system at 110℃.

[0045] 4) The mixed powder obtained in step 2) and the natural graphite powder or artificial graphite powder and calcined coke aggregate obtained in step 3) are added to a mixer in a mass ratio of 5:10:85 and mixed for 1 hour to obtain composite aggregate powder.

[0046] 5) Add the composite aggregate powder prepared in step 4) into a kneading pot, dry mix at 110℃ for 1 hour to remove moisture, continue to heat to 150℃, add molten modified coal tar pitch at a mass ratio of 66:34, maintain the kneading temperature at 190℃ and the kneading speed at 50 r / min, knead for 1.5 hours, hot roll the powder at 190℃ 3 times, cool to room temperature, crush, and pass through a 200 mesh sieve to obtain pressed powder.

[0047] 6) After the powder prepared in step 5) is molded at 1 MPa, it is left to stand for 10 hours. Then, the blank is vacuum-sealed with aluminum-plastic film and preheated in an oven at 110℃ for 10 hours. At the same time, the pressure medium (hydraulic oil) of the isostatic press is heated to 110℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated blank in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 200 MPa to obtain a density of 1.56 g / cm³. 3 Carbon graphite material green body.

[0048] 7) Place the carbon-graphite material green body prepared in step 6) into a graphite crucible. After the six sides of the green body are filled with the calcining material, place it in a tube furnace. During the calcination process, argon / nitrogen gas is introduced, and the furnace is calcined at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.65 g / cm³. 3 Calcinated carbon graphite blocks.

[0049] 8) The carbon-graphite material obtained in step 7) was treated at 2500℃ for 4 hours in a graphitization furnace, then the temperature was controlled to decrease to 200℃ and then allowed to cool naturally to room temperature, resulting in a material with a density of 1.78 g / cm³. 3 Graphitized bulk material.

[0050] Example 3: A method for preparing a sulfonated graphene-reinforced antioxidant carbon graphite sealing material includes the following steps: 1) Hexagonal boron nitride nanosheets (h-BN) were added to a 5 mol / L mixed solution of sodium hydroxide and potassium hydroxide (1:1), ultrasonically stirred in an oil bath at 120°C for 24 h, naturally cooled, washed with water and filtered three times, and dried in a vacuum drying oven at 80°C for 12 h to obtain surface-hydroxylated h-BN nanosheets.

[0051] 2) The surface-hydroxylated h-BN nanosheets and sulfonated graphene obtained in step 1) were added to anhydrous ethanol and mixed, with a mass ratio of 2:1. After ultrasonic oscillation in a water bath at 60°C for 12 hours, the mixture was magnetically stirred at 800 r / min for 2 hours, centrifuged, filtered and washed three times, and then the mixed powder after the grafting reaction was placed in a vacuum heat treatment furnace. The temperature was slowly increased to 120°C at a rate of 10°C / min and held for 1 hour. After cooling with high-purity nitrogen for 30 minutes, the mixture was ground into powder to obtain a mixed powder of surface-grafted modified h-BN and sulfonated graphene.

[0052] 3) Natural graphite powder or artificial graphite powder with a particle size D50 of 5μm and calcined coke aggregate with a D50 of 12μm were prepared using Raymond mill and high-energy air jet mill. Some air and moisture in the surface and pores were removed by vacuum drying system at 110℃.

[0053] 4) The mixed powder obtained in step 2) and the natural graphite powder or artificial graphite powder and calcined coke aggregate obtained in step 3) are added to a mixer in a mass ratio of 5:10:85 and mixed for 1 hour to obtain composite aggregate powder.

[0054] 5) Add the composite aggregate powder prepared in step 4) into a kneading pot, dry mix at 110℃ for 1 hour to remove moisture, continue to heat to 150℃, add molten modified coal tar pitch at a mass ratio of 64:36, maintain the kneading temperature at 190℃ and the kneading speed at 50 r / min, knead for 1.5 hours, hot roll the powder at 190℃ 3 times, after cooling to room temperature, crush it, and pass it through a 200 mesh sieve to obtain compressed powder.

[0055] 6) After the powder prepared in step 5) is molded at 1 MPa, it is left to stand for 10 hours. Then, the blank is vacuum-sealed with aluminum-plastic film and preheated in an oven at 110℃ for 10 hours. At the same time, the pressure medium (hydraulic oil) of the isostatic press is heated to 110℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated blank in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 200 MPa to obtain a powder with a density of 1.61 g / cm³. 3 Carbon graphite material green body.

[0056] 7) Place the carbon-graphite material green body prepared in step 6) into a graphite crucible. After the six sides of the green body are filled with calcining material, place it in a tube furnace. During the calcination process, argon / nitrogen gas is introduced, and the furnace is calcined at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.69 g / cm³. 3 Calcinated carbon graphite blocks.

[0057] 8) The carbon-graphite material obtained in step 7) was treated at 2500℃ for 4 hours in a graphitization furnace, then the temperature was controlled to decrease to 200℃ and allowed to cool naturally to room temperature, resulting in a material with a density of 1.81 g / cm³. 3 Graphitized bulk material.

[0058] Example 4: A method for preparing a sulfonated graphene-reinforced antioxidant carbon graphite sealing material includes the following steps: 1) Hexagonal boron nitride nanosheets (h-BN) were added to a 5 mol / L mixed solution of sodium hydroxide and potassium hydroxide (1:1), ultrasonically stirred in an oil bath at 120°C for 24 h, naturally cooled, washed with water and filtered three times, and dried in a vacuum drying oven at 80°C for 12 h to obtain surface-hydroxylated h-BN nanosheets.

[0059] 2) The surface-hydroxylated h-BN nanosheets and sulfonated graphene obtained in step 1) were placed in N,N-dimethylformamide (DMF) solution and subjected to low-temperature plasma treatment at 50°C for 30 min under argon atmosphere with a radio frequency power of 12 MHz. After washing and drying, they were mixed in anhydrous ethanol at a mass ratio of 2:1. After ultrasonic oscillation in a water bath at 60°C for 12 h, magnetic stirring at 800 r / min for 2 h, centrifugation, filtration and washing three times, and grinding into powder to obtain a mixed powder of surface-grafted modified h-BN and sulfonated graphene.

[0060] 3) Natural graphite powder or artificial graphite powder with a particle size D50 of 5μm and calcined coke aggregate with a D50 of 12μm were prepared using Raymond mill and high-energy air jet mill. Some air and moisture in the surface and pores were removed by vacuum drying system at 110℃.

[0061] 4) The mixed powder obtained in step 2) and the natural graphite powder or artificial graphite powder and calcined coke aggregate obtained in step 3) are added to a mixer in a mass ratio of 5:10:85 and mixed for 1 hour to obtain composite aggregate powder.

[0062] 5) Add the composite aggregate powder prepared in step 4) into a kneading pot, dry mix at 110℃ for 1 hour to remove moisture, continue to heat to 150℃, add molten modified coal tar pitch at a mass ratio of 64:36, maintain the kneading temperature at 190℃ and the kneading speed at 50 r / min, knead for 1.5 hours, hot roll the powder at 190℃ 3 times, after cooling to room temperature, crush it, and pass it through a 200 mesh sieve to obtain compressed powder.

[0063] 6) After the powder prepared in step 5) is molded at 1 MPa, it is left to stand for 10 hours. Then, the blank is vacuum-sealed with aluminum-plastic film and preheated in an oven at 110℃ for 10 hours. At the same time, the pressure medium (hydraulic oil) of the isostatic press is heated to 110℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated blank in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 200 MPa to obtain a powder with a density of 1.59 g / cm³. 3 Carbon graphite material green body.

[0064] 7) Place the carbon-graphite material green body prepared in step 6) into a graphite crucible. After the six sides of the green body are filled with calcining material, place it in a tube furnace. During the calcination process, argon / nitrogen gas is introduced, and the furnace is calcined at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.67 g / cm³. 3 Calcinated carbon graphite blocks.

[0065] 8) The carbon-graphite material obtained in step 7) was treated at 2500℃ for 4 hours in a graphitization furnace, then the temperature was controlled to decrease to 200℃ and allowed to cool naturally to room temperature, resulting in a material with a density of 1.79 g / cm³. 3 Graphitized bulk material.

[0066] Comparative Example 1: A method for preparing a sulfonated graphene-reinforced antioxidant carbon-graphite sealing material, without surface hydroxylation treatment of hexagonal boron nitride nanosheets, includes the following steps: 1) Hexagonal boron nitride nanosheets (h-BN) and sulfonated graphene were placed in N,N-dimethylformamide (DMF) solution and subjected to low-temperature plasma treatment at 50°C for 30 min under argon atmosphere with a radio frequency power of 12 MHz. After washing and drying, they were mixed in anhydrous ethanol at a mass ratio of 2:1. After ultrasonic vibration in a water bath at 60°C for 12 h, magnetic stirring at 800 r / min for 2 h was performed. After centrifugation, filtration and washing three times, the mixed powder after the grafting reaction was placed in a vacuum heat treatment furnace and slowly heated to 120°C at a rate of 10°C / min, held at that temperature for 1 h, and then cooled with high-purity nitrogen for 30 min. The powder was then ground into powder to obtain a mixed powder of surface-grafted modified h-BN and sulfonated graphene.

[0067] 2) Natural graphite powder or artificial graphite powder with a particle size D50 of 5μm and calcined coke aggregate with a D50 of 12μm were prepared using Raymond mill and high-energy air jet mill. Some air and moisture in the surface and pores were removed by vacuum drying system at 110℃.

[0068] 3) The mixed powder obtained in step 1) and the natural graphite powder or artificial graphite powder and calcined coke aggregate obtained in step 2) are added to a mixer in a mass ratio of 5:10:85 and mixed for 1 hour to obtain composite aggregate powder.

[0069] 4) Add the composite aggregate powder prepared in step 3) into a kneading pot, dry mix at 110℃ for 1 hour to remove moisture, continue to heat to 150℃, add molten modified coal tar pitch at a mass ratio of 64:36, maintain the kneading temperature at 190℃ and the kneading speed at 50 r / min, knead for 1.5 hours, hot roll the powder at 190℃ 3 times, after cooling to room temperature, crush it, and pass it through a 200 mesh sieve to obtain compressed powder.

[0070] 5) After the powder prepared in step 4) is molded at 1 MPa, it is left to stand for 10 hours. Then, the blank is vacuum-sealed with aluminum-plastic film and preheated in an oven at 110℃ for 10 hours. At the same time, the pressure medium (hydraulic oil) of the isostatic press is heated to 110℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated blank in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 200 MPa to obtain a powder with a density of 1.58 g / cm³. 3 Carbon graphite material green body.

[0071] 6) Place the carbon-graphite material green body prepared in step 5) into a graphite crucible. After the six sides of the green body are filled with calcining material, place it in a tube furnace. During the calcination process, argon / nitrogen gas is introduced, and the furnace is calcined at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.67 g / cm³. 3 Calcinated carbon graphite blocks.

[0072] 7) The carbon-graphite material obtained in step 6) was treated in a graphitization furnace at 2500℃ for 4 hours, then the temperature was controlled to decrease to 200℃ and then allowed to cool naturally to room temperature, resulting in a material with a density of 1.80 g / cm³. 3 Graphitized bulk material.

[0073] The test results of the flexural strength and compressive strength of the carbon-graphite material obtained in this comparative example are as follows: Figure 4 (a) and Figure 4 As shown in (c), the cross-sectional and surface microstructures of the carbon-graphite material are shown in the following figures. Figure 4 (b) and Figure 4 As shown in (d), by Figure 4 (a) and Figure 4As shown in (c), the flexural strength and compressive strength of the graphite material are 61.99 MPa and 115.66 MPa, respectively, which are significantly improved compared to the carbon-graphite material prepared by traditional processes. However, due to the incomplete grafting reaction, its physical properties and oxidation resistance are worse than those in Example 1. As can be seen from the corresponding microstructure diagram, the aggregates are tightly packed together, with fewer pores, smaller pore sizes between particles, and no through-holes.

[0074] Comparative Example 2: A method for preparing a sulfonated graphene-reinforced antioxidant carbon graphite sealing material includes the following steps: 1) Natural graphite powder or artificial graphite powder with a particle size D50 of 5μm and calcined coke aggregate with a D50 of 12μm were prepared using Raymond mill and high-energy air jet mill. Some air and moisture in the surface and pores were removed by vacuum drying system at 110℃.

[0075] 2) Add sulfonated graphene, natural graphite powder or artificial graphite powder obtained in step 1), and calcined coke aggregate to a mixer in a mass ratio of 5:10:85 and mix for 1 hour to obtain composite aggregate powder.

[0076] 3) The composite aggregate powder prepared in step 2) is put into a kneading pot and dry-mixed at 110℃ for 1 hour to remove moisture. The temperature is then raised to 150℃, and molten modified coal tar pitch is added at a mass ratio of 64:36. The kneading temperature is maintained at 190℃ and the kneading speed is 50 r / min. After kneading for 1.5 hours, the mixture is hot-rolled into sheets three times at 190℃. After cooling to room temperature, the sheets are crushed and passed through a 200-mesh sieve to obtain pressed powder.

[0077] 4) After the powder prepared in step 3) is molded at 1 MPa, it is left to stand for 10 hours. Then, the blank is vacuum-sealed with aluminum-plastic film and preheated in an oven at 110℃ for 10 hours. At the same time, the pressure medium (hydraulic oil) of the isostatic press is heated to 110℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated blank in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 200 MPa to obtain a density of 1.64 g / cm³. 3 Carbon graphite material green body.

[0078] 5) Place the carbon-graphite material green body prepared in step 4) into a graphite crucible. After the six sides of the green body are filled with sintering material, place it in a tube furnace. During the sintering process, argon / nitrogen gas is introduced, and the furnace is sintered at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.74 g / cm³. 3 Calcinated carbon graphite blocks.

[0079] 6) The carbon-graphite material obtained in step 5) was treated at 2500℃ for 4 hours in a graphitization furnace, then the temperature was controlled to decrease to 200℃ and allowed to cool naturally to room temperature, resulting in a material with a density of 1.85 g / cm³. 3 Graphitized bulk material.

[0080] The test results of the flexural strength and compressive strength of the carbon-graphite material obtained in this comparative example are as follows: Figure 5 (a) and Figure 5 As shown in (c), the cross-sectional and surface microstructures of the carbon-graphite material are shown in the following figures. Figure 5 (b) and Figure 5 As shown in (d), by Figure 5 (a) and Figure 5 As shown in (c), the flexural strength and compressive strength of the graphite material are 72.85 MPa and 141.99 MPa, respectively, which represent a significant improvement in performance compared to carbon-graphite materials prepared by traditional processes. The microstructure image reveals a clear and tightly bonded structure of particles of varying sizes, with few pores and small pore sizes, and no cracks. Therefore, the prepared carbon-graphite material exhibits superior flexural and compressive strength, but its oxidation resistance is poor.

[0081] Comparative Example 3: A method for preparing an antioxidant carbon graphite sealing material includes the following steps: 1) Hexagonal boron nitride nanosheets (h-BN) were added to a 5 mol / L mixed solution of sodium hydroxide and potassium hydroxide (1:1), ultrasonically stirred in an oil bath at 120°C for 24 h, naturally cooled, washed with water and filtered three times, and dried in a vacuum drying oven at 80°C for 12 h to obtain surface-hydroxylated h-BN nanosheets.

[0082] 2) Natural graphite powder or artificial graphite powder with a particle size D50 of 5μm and calcined coke aggregate with a D50 of 12μm were prepared using Raymond mill and high-energy air jet mill. Some air and moisture in the surface and pores were removed by vacuum drying system at 110℃.

[0083] 3) The surface-hydroxylated h-BN nanosheets obtained in step 1) and the natural graphite powder or artificial graphite powder obtained in step 2) and the calcined coke aggregate are added to a mixer in a mass ratio of 5:10:85 and mixed for 1 hour to obtain composite aggregate powder.

[0084] 4) Add the composite aggregate powder prepared in step 3) into a kneading pot, dry mix at 110℃ for 1 hour to remove moisture, continue to heat to 150℃, add molten modified coal tar pitch at a mass ratio of 64:36, maintain the kneading temperature at 190℃ and the kneading speed at 50 r / min, knead for 1.5 hours, hot roll the powder at 190℃ 3 times, after cooling to room temperature, crush it, and pass it through a 200 mesh sieve to obtain compressed powder.

[0085] 5) After the powder prepared in step 4) is molded at 1 MPa, it is left to stand for 10 hours. Then, the blank is vacuum-sealed with aluminum-plastic film and preheated in an oven at 110℃ for 10 hours. At the same time, the pressure medium (hydraulic oil) of the isostatic press is heated to 110℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated blank in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 200 MPa to obtain a density of 1.56 g / cm³. 3 Carbon graphite material green body.

[0086] 6) Place the carbon-graphite material green body prepared in step 5) into a graphite crucible. After the six sides of the green body are filled with sintering material, place it in a tube furnace. During the sintering process, argon / nitrogen gas is introduced, and the furnace is sintered at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.65 g / cm³. 3 Calcinated carbon graphite blocks.

[0087] 7) The carbon-graphite material obtained in step 6) was treated at 2500℃ for 4 hours in a graphitization furnace, then the temperature was controlled to decrease to 200℃ and then allowed to cool naturally to room temperature, resulting in a material with a density of 1.79 g / cm³. 3 Graphitized bulk material.

[0088] The test results of the flexural strength and compressive strength of the carbon-graphite material obtained in this comparative example are as follows: Figure 6 (a) and Figure 6 As shown in (c), the cross-sectional microstructure and surface morphology of the carbon-graphite material are respectively as follows: Figure 6 (b) and Figure 6 As shown in (d), by Figure 6 (a) and Figure 6 As shown in (c), the flexural strength and compressive strength of the graphite material are 59.82 MPa and 106.78 MPa, respectively, which are significantly improved compared to carbon-graphite materials prepared by traditional processes. The corresponding microstructure diagrams show that the aggregates are tightly connected, with small pores between particles, no through-holes, and no cracks. However, the material exhibits poor oxidation resistance.

[0089] Antioxidant carbon-graphite sealing materials were prepared using the methods described in Examples 1-4 and Comparative Examples 1-3, respectively. The bulk density, flexural strength, and compressive strength were calculated according to the YB / T4379-2014 standard, and the thermal oxidation weight loss was tested according to the Q / JBQN13-2017 standard. The results are shown in Table 1 below.

[0090] Table 1: Performance parameters of carbon-graphite materials obtained in Examples 1-4 and Comparative Examples 1-3

[0091] As shown in Table 1 above, the carbon-graphite material prepared in Example 1 using hydroxylated hexagonal boron nitride as an oxidation inhibitor and sulfonated graphene exhibits the best performance. A comparison between Example 1 and Example 2 shows that the grafting reaction of the mixed powder obtained by low-temperature plasma treatment and vacuum heat treatment is sufficient, improving the oxidation resistance of the carbon-graphite material. A comparison between Example 1 and Example 3 shows that the grafting reaction of the mixed powder obtained by simultaneous low-temperature plasma treatment and vacuum heat treatment is sufficient, resulting in a graphite material with higher bulk density and better oxidation resistance. A comparison between Example 1 and Example 4 shows that the grafting reaction of the mixed powder obtained by simultaneous low-temperature plasma treatment and vacuum heat treatment is sufficient, resulting in a graphite material with higher bulk density and better oxidation resistance. A comparison between Example 1 and Comparative Example 1 shows that the carbon-graphite material prepared by grafting hydroxylated boron nitride and sulfonated graphene has higher bulk density, higher flexural and compressive strength, and better oxidation resistance. A comparison of Example 1 and Comparative Example 2 shows that the carbon-graphite material prepared by simultaneously adding sulfonated graphene and hydroxylated hexagonal boron nitride exhibits better oxidation resistance than that prepared by using sulfonated graphene alone as an additive. A comparison of Example 1 and Comparative Example 3 shows that the carbon-graphite material prepared by simultaneously adding sulfonated graphene and hydroxylated hexagonal boron nitride exhibits better oxidation resistance than that prepared by using hydroxylated hexagonal boron nitride alone as an oxidation inhibitor.

Claims

1. A method for preparing a sulfonated graphene-reinforced antioxidant carbon graphite sealing material, characterized in that, Includes the following steps: (1) Hexagonal boron nitride nanosheets were surface-treated with alkaline solution to obtain surface-hydroxylated hexagonal boron nitride nanosheets; (2) The surface-hydroxylated hexagonal boron nitride nanosheets and sulfonated graphene are mixed and reacted in a solvent, and the reaction products are collected to obtain a mixed powder; (3) The mixed powder, graphite powder and calcined coke aggregate are mixed to obtain composite aggregate powder; (4) The composite aggregate powder is added to a mixing pot and asphalt is added for kneading. Then, it is rolled and crushed to obtain pressed powder. The pressed powder is then molded and calcined to obtain carbon graphite sealing material.

2. The preparation method according to claim 1, characterized in that, The concentration of the alkaline solution is 3-5 mol / L, and the alkaline solution is a mixed solution of sodium hydroxide and potassium hydroxide. The surface treatment involves stirring in an oil bath at 100-120℃ for 12-24 hours, then naturally cooling, washing with water 2-3 times, and drying.

3. The preparation method according to claim 1, characterized in that, Before mixing and reacting the surface-hydroxylated hexagonal boron nitride nanosheets and sulfonated graphene in a solvent, the surface-hydroxylated hexagonal boron nitride nanosheets and sulfonated graphene are first placed in an N,N-dimethylformamide solution and subjected to low-temperature plasma treatment in an argon atmosphere. After washing and drying, they are then mixed and reacted in anhydrous ethanol solvent. During the low-temperature plasma treatment, the treatment temperature is controlled at 40-60℃, the treatment time is 20-40 min, and the radio frequency power is 10-15 MHz.

4. The preparation method according to claim 1, characterized in that, The collected reaction products are also subjected to vacuum heat treatment, which involves placing the reaction products in a vacuum heat treatment furnace, slowly heating them to 100-120°C at a rate of 5-10°C / min, holding them at that temperature for 1-2 hours, and then cooling them with high-purity nitrogen for 15-30 minutes.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the surface-hydroxylated hexagonal boron nitride nanosheets to sulfonated graphene is (2-4):(1-3).

6. The preparation method according to claim 1, characterized in that, The mixing reaction is carried out by ultrasonic oscillation in a water bath at 40-60℃ for 10-12 hours, followed by magnetic stirring at 500-800 r / min for 1-2 hours.

7. The preparation method according to any one of claims 1-6, characterized in that, The graphite powder is natural or artificial graphite powder with a particle size D50 of 5-7 μm; the calcined coke aggregate has a particle size D50 of 8-12 μm; the graphite powder and calcined coke aggregate are first dried at 110-150℃ using a vacuum drying system to remove some air and moisture from their surfaces and pores.

8. The preparation method according to any one of claims 1-6, characterized in that, The mass ratio of the mixed powder, graphite powder and calcined coke aggregate is (1-8):(9-12):(80-90).

9. The preparation method according to any one of claims 1-6, characterized in that, The process involves adding asphalt and kneading, followed by rolling and crushing to obtain pressed powder. The steps include: first, dry mixing at 110-140℃ for 1-2 hours to remove moisture, then continuing to heat to 140-170℃, adding molten modified coal tar pitch at a mass ratio of (62-70):(30-38), maintaining the kneading temperature at 185-200℃, kneading speed at 30-50 rpm, kneading for 0.5-2 hours, then hot rolling at 180-200℃ 3-5 times, and after cooling to room temperature, crushing and passing through a 160-325 mesh sieve to obtain pressed powder.

10. The preparation method according to any one of claims 1-6, characterized in that, The molding and baking process includes the following steps: After the powder is pressed into shape at 1-3 MPa, it is left to stand for 10-20 hours. Then, the green body is vacuum sealed with aluminum-plastic film and preheated in an oven at 80-120℃ for 2-10 hours. At the same time, the hydraulic oil of the isostatic press is heated to 80-120℃. After the temperature of the hydraulic oil in the isostatic press is constant, the preheated green body in the oven is placed in the isostatic pressing cylinder and warm isostatically pressed at 150-200 MPa to prepare the carbon graphite material green body. Carbon graphite material green body is placed in a graphite crucible. After the six sides of the green body are filled with calcining material, it is placed in a tube furnace. Argon / nitrogen gas is introduced during the calcination process. The green body is calcined at 1000-1200℃ for 4-10 hours. After the temperature is controlled by the program to drop to 100-300℃, it is naturally cooled to room temperature to obtain calcined graphite block. After treating the calcined graphite blocks in a graphitization furnace at 2000-3000℃ for 1-5 hours, the temperature is then controlled by a program to cool down to 100-300℃, and then naturally cooled to room temperature to obtain carbon graphite sealing material.

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