Carbon pitch graphitization method

Abstract

The invention provides a carbon pitch graphitization method, and solves the problems of high energy consumption, insufficient graphitization degree, non-uniform product performance and the like in the existing graphitization process. The method comprises the following steps: firstly, selecting a carbon asphalt raw material with a softening point of 180-250 DEG C, and drying and screening to remove impurities; then pre-carbonization treatment is carried out at 500-700 DEG C, volatile components are removed, and a primary carbon crystal nucleus structure is formed; crushing the pre-carbonized asphalt to a specified particle size, adding 10%-20% of a conductive reinforcing material according to a mass ratio, and uniformly mixing by using a high-energy ball mill; the green body is formed through a mold pressing or isostatic pressing technology, so that the density is uniform; the blank is placed in an ultra-high-temperature graphitization furnace, graphitization treatment is completed under the protection of inert gas at the temperature of 3000-3200 DEG C, and the heat preservation time is 3-10 hours. The graphitization degree of the obtained graphite material is greater than or equal to 94%, the conductivity is greater than or equal to 22.5 S / cm, the thermal conductivity is greater than or equal to 160W / m.K, and the graphite material can be widely applied to the fields of lithium battery cathodes, high-temperature lubricants, conductive coatings and refractory materials.

Description

Technical Field

[0001] The present invention relates to the technical field of pitch graphitization, and particularly to a method for graphitizing carbon pitch. Background Art

[0002] Graphite materials are widely used in fields such as energy, electronics, aerospace, and chemical industry due to their excellent physical and chemical properties. Graphite has high electrical conductivity, high thermal conductivity, good corrosion resistance, and high temperature resistance, and is an important component of the negative electrode of lithium-ion batteries, electrode materials, lubricants, and high-temperature refractory materials. Due to the limited natural graphite resources and complex processing, the preparation technology of artificial graphite has received extensive attention in recent years. Artificial graphite is usually based on carbon sources such as coal tar pitch and petroleum pitch, and is graphitized through high-temperature treatment. However, there are still many deficiencies in the existing technology during the preparation of artificial graphite, which limits its large-scale application and further improvement of performance.

[0003] Graphitization is the core process in the preparation of artificial graphite. By high temperature, the carbon atom structure is gradually rearranged to form an ordered graphite crystal structure. However, the activation energy required for the rearrangement of carbon atoms is extremely high, and usually a high temperature above 3000 °C is required to achieve a high degree of graphitization. In traditional graphitization processes, due to the low temperature control accuracy of the equipment, it is difficult to precisely control the heating rate and holding time, resulting in low energy utilization efficiency. In addition, due to the dependence of the graphitization furnace body on high-temperature materials, the equipment cost and energy consumption remain high, making the graphitization process a significant burden on the overall production cost.

[0004] Coal tar pitch or petroleum pitch as the main carbon source usually contains a relatively high proportion of volatile components in its molecules, such as light aromatic hydrocarbons and low-molecular hydrocarbons. These volatile components will decompose and be discharged during the high-temperature graphitization process, resulting in pores or cracks in the green body, affecting the density and mechanical properties of the graphite material. In addition, the presence of volatile components will interfere with the orderly rearrangement of carbon atoms and reduce the graphitization efficiency. Therefore, in actual production, it is usually necessary to perform pre-carbonization treatment on the raw materials to remove volatile components. However, the current pre-carbonization technology still has the problem of low volatile component removal rate, resulting in the inability of the subsequent graphitization process to proceed efficiently.

[0005] The previous step of the graphitization process is to form the pretreated carbon material into a green body. In the traditional molding process by pressing, due to uneven pressure application, the density distribution inside the green body is uneven, and it is easy to have problems such as local overheating, stress concentration, or cracks during the subsequent graphitization process, thus reducing the material performance. In recent years, the isostatic pressing molding process has been gradually applied to the preparation of graphite materials, but there are still great challenges in the optimization of its pressure and molding parameters, and some processes have not solved the problems of high porosity and high defect rate of the green body during the control process.

[0006] The performance requirements of graphite materials in applications are becoming increasingly stringent. For example, lithium battery negative electrode materials require higher specific capacity and excellent cycle stability, conductive materials require higher electrical conductivity, and refractory materials and high-temperature lubricants place higher requirements on thermal conductivity and corrosion resistance. However, existing graphitized products often exhibit high lattice defect rates, low electrical conductivity and thermal conductivity due to insufficient graphitization. In addition, traditional processes lack refined control over key performance indicators (such as graphitization degree, electrical conductivity, and impurity content) in the preparation of high-end graphite products (such as lithium battery negative electrodes and conductive coatings), limiting their further application in high-performance fields.

[0007] Graphitization treatment usually uses a resistance furnace or an induction heating furnace, but traditional equipment has major deficiencies in temperature control accuracy, atmosphere protection, and furnace temperature uniformity. Local overheating or temperature fluctuations in the furnace will lead to uneven graphitization rearrangement of carbon atoms, ultimately forming an uneven graphite crystal structure. In addition, high-temperature equipment has high operating and maintenance costs, and is prone to efficiency decline in continuous large-scale production, which affects the production capacity and quality of graphite materials.

[0008] In the process of artificial graphitization, conductive reinforcing materials (such as graphite powder, graphene or carbon nanotubes) are usually added for compounding to improve material performance. However, in the traditional composite process, the problem of uneven dispersion of auxiliary materials has not been effectively solved, resulting in limited reinforcement effect. At the same time, some composite materials are prone to thermal decomposition or agglomeration under high temperature conditions of graphitization, affecting the stability and reliability of the final product performance.

[0009] In summary, the existing technology has deficiencies in graphitization temperature, energy consumption, raw material processing, green body molding, product performance and equipment performance. These problems not only limit the quality and performance of graphitized products, but also significantly increase production costs and energy consumption. Therefore, how to optimize raw material processing, improve molding technology, improve graphitization efficiency, and control the performance and uniformity of graphitized products are still technical problems that need to be solved in the field of artificial graphite preparation.

[0010] To this end, we proposed a carbon pitch graphitization method to solve the above problems. Summary of the invention

[0011] The purpose of the present invention is to solve the above technical problems and provide a carbon pitch graphitization method.

[0012] In order to achieve the above purpose, the present invention is implemented as follows:

[0013] Pre-carbonization treatment: The sieved carbon pitch is placed in a tube furnace or box furnace protected by nitrogen or argon and heated. The gas flow rate is maintained at 1 - 2 L / min to ensure that the reaction environment is not disturbed by oxygen. The temperature range is 500 - 700 °C, and the heating rate is controlled at 3 - 5 °C / min to ensure uniform heating of the pitch and avoid material cracking or incomplete volatilization caused by sudden temperature rise. During this process, the temperature accuracy is required to be controlled within ±2 °C to ensure the stability of the pitch structure. The treatment time is maintained for 2 - 5 hours to remove low-molecular-weight volatiles and impurities and form a stable pre-carbonized pitch structure;

[0014] Mixing and homogenization: The pre-carbonized pitch is crushed to 50 - 100 mesh, and 10% - 20% of highly conductive filler is added by mass ratio. The mixture is homogenized by a ball mill for 30 - 60 minutes to ensure uniform dispersion of the filler and enhance the conductivity and crystallinity of the subsequent graphitized material;

[0015] Forming process: The mixed material is formed by die pressing or isostatic pressing process;

[0016] High-temperature graphitization treatment: The formed green body is placed in an ultra-high-temperature graphitization furnace and gradually heated to 3000 °C - 3200 °C at a heating rate of 3 - 5 °C / min under the protection of nitrogen or argon. It is kept at this temperature range for 3 - 10 hours to promote the ordered arrangement of carbon atoms and form a structure with high graphitization degree. During this process, through real-time temperature and gas flow control, the material is prevented from being damaged due to local overheating or oxidation;

[0017] Slow cooling and temperature reduction: After graphitization is completed, it is gradually cooled to room temperature at a cooling rate of 1 - 2 °C / min to ensure the release of internal stress in the graphite material and thus avoid the formation of microcracks;

[0018] Post-treatment and finishing: The cooled graphitized material is treated by physical or chemical methods to remove impurities. Chemical treatment can use mixed acid immersion to remove residual metal impurities; then according to the product use, it is sieved, crushed or machined to form the required particle size or shape;

[0019] Performance testing and grading: The treated graphite material is subjected to performance testing, including graphitization degree, conductivity, thermal conductivity and purity index; according to the test results, the products are graded and stored for different application scenarios.

[0020] As a preferred technical solution of the present invention, the pre-carbonization treatment is completed through a dynamic temperature control program. The heating rate is controlled at 3 - 5 °C / min, and the holding time is 2 - 5 hours. The removal rate of low-molecular-weight volatiles reaches 90% - 95%, and a carbon crystal nucleus structure is initially formed.

[0021] As a preferred technical solution of the present invention, in the mixing and homogenization step, the filler is one or more of carbon nanotubes, graphite powder, graphene or carbon fiber, and the addition amount is 10%-20% of the mass of carbon pitch; the mixing and homogenization is carried out by a ball mill, and the ball milling time is controlled within 30-60 minutes to ensure uniform distribution of the filler and enhance the electrical conductivity.

[0022] As a preferred technical solution of the present invention, the molding process includes the following methods:

[0023] Compression molding: Under a pressure of 20-40 MPa, a block or columnar blank is formed through a compression molding device;

[0024] Isostatic pressing: Pressurize in an isostatic pressing device of 100-200 MPa, the density of the blank is uniform, and the internal distribution structure is dense.

[0025] As a preferred technical solution of the present invention, the graphitization process includes the following specific optimization measures:

[0026] The graphitization temperature is 3000°C - 3200°C;

[0027] The heating rate is 3-5°C / minute;

[0028] The heat preservation time is 6-10 hours. By monitoring the temperature distribution and gas flow in the furnace in real time, local overheating or oxidation phenomena can be avoided.

[0029] As a preferred technical solution of the present invention, the slow cooling process is carried out at a rate of 1-2°C / minute to cool down to room temperature, so as to effectively release the internal stress of the graphitized material and avoid the generation of thermal cracks and microstructural defects.

[0030] As a preferred technical solution of the present invention, the post-treatment step includes the following contents:

[0031] Soak the graphite material with a mixed acid solution of concentrated nitric acid and hydrofluoric acid to remove residual metal impurities;

[0032] After rinsing with pure water and drying, screen to a particle size range of 20-200 μm;

[0033] According to the application requirements, perform a coating treatment on the graphite material to enhance the lubricity or corrosion resistance.

[0034] As a preferred technical solution of the present invention, the prepared graphite material exhibits the following characteristics in performance testing:

[0035] The graphitization degree ≥ 92%;

[0036] The electrical conductivity ≥ 20 S / cm;

[0037] The thermal conductivity ≥ 150 W / m·K;

[0038] The purity is ≥99.5%.

[0039] As a preferred technical solution of the present invention, the prepared graphite material is applicable to the following fields:

[0040] Anode material for lithium-ion batteries, having excellent cycle stability and specific capacity;

[0041] Conductive material, with a conductivity superior to that of traditional graphite products;

[0042] High-temperature lubricant and refractory material, used for mechanical equipment in extreme environments.

[0043] As a preferred technical solution of the present invention, the pre-carbonization treatment of the raw materials is synergistically optimized with the high-temperature graphitization process. The pre-carbonization step significantly reduces the volatile content and forms a preliminary carbon crystal nucleus structure, providing an ordered crystal nucleus for high-temperature graphitization. The lattice integrity and conductivity of the final graphitized product are significantly improved.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention effectively promotes the ordered arrangement of carbon atoms by optimizing the pre-carbonization treatment, mixing and homogenization process, and ultra-high-temperature graphitization conditions, enabling the graphitization degree to reach 94.2%, which is significantly higher than that of traditional graphitization methods. The prepared graphite material has excellent electrical conductivity (≥22.5 S / cm) and thermal conductivity (≥160.2 W / m·K), meeting the performance requirements of lithium battery anodes, high-temperature conductive materials, and high-thermal-conductivity materials.

[0046] The present invention significantly reduces the volatile content through pre-carbonization treatment, provides a stable carbon-based structure for the graphitization process, and reduces the energy consumption of the graphitization process. In addition, the isostatic pressing forming process improves the density and uniformity of the green body, avoids performance loss caused by internal defects in the traditional process, and significantly improves the yield of the graphite material.

[0047] By precisely controlling process conditions such as adjusting the graphitization temperature, filler ratio, and forming pressure, this method can flexibly adjust product performance according to actual needs. The prepared high-purity graphite material is not only applicable to high-end lithium battery anodes but also can be used in various fields such as conductive coatings, high-temperature lubricants, and refractory materials, having broad industrial application prospects. Specific embodiments

[0048] To make the objectives, technical solutions and advantages of the present invention clearer, the following will, in conjunction with the embodiments of the present invention, clearly and completely describe the technical solutions in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0049] The following will, in conjunction with the embodiments, describe in detail the specific implementation manners of the present invention.

[0050] Embodiment 1: Conventional graphitization process of carbon pitch;

[0051] 1. Raw material selection and pretreatment: Select coal tar-based carbon pitch with a softening point of 200°C (industrial purity of 98%), put it into a drying oven, and dry it at 80°C for 8 hours to remove the water and volatile impurities adsorbed on the surface. The dried carbon pitch particles are subjected to screening treatment to control the particle diameter to be 3 - 5 mm to ensure the uniformity of the pre-carbonization process.

[0052] 2. Pre-carbonization treatment: Place the dried and screened carbon pitch particles in a tube furnace and conduct heat pretreatment under a nitrogen protection atmosphere. The experimental conditions are as follows: Raise the temperature from room temperature to 600°C at a heating rate of 4°C per minute, and keep the temperature for 4 hours. During this period, low-molecular volatile substances (such as light components and polycyclic aromatic hydrocarbons) are fully removed. Through measurement by a gas capture system, the removal rate of volatile components reaches 92%, and at the same time, the residual carbon components form a preliminary carbon crystal nucleus structure.

[0053] 3. Mixing and homogenization: Process the pre-carbonized pitch to a fineness of 80 meshes (particle size of about 180 μm) through a pulverizer, and then add 15% of graphite powder (conductivity-enhancing filler, conductivity of 50 S / cm) by mass ratio. Place the mixture in a high-energy ball mill and uniformly mix it at a rotation speed of 300 rpm for 60 minutes to ensure that the graphite powder is fully dispersed and forms a uniform composite structure with the carbon-based material.

[0054] 4. Molding process: Conduct preliminary blank molding on the mixed material through a molding process. The specific conditions are as follows: Use a hydraulic die equipment to prepare a cylindrical blank with a diameter of 50 mm and a height of 20 mm under a pressure of 30 MPa. This molding process ensures that the blank has good density and lays a foundation for subsequent graphitization.

[0055] 5. High-temperature graphitization: Place the cylindrical preliminary blank into an ultra-high-temperature graphitization furnace and conduct graphitization treatment under an argon protection atmosphere. The graphitization conditions are as follows:

[0056] Heating rate: 4°C per minute;

[0057] Final temperature: 3100°C;

[0058] Insulation time: 8 hours. Under high-temperature conditions, carbon atoms gradually arrange into an ordered hexagonal graphite structure. The optimized design of temperature and insulation time effectively improves the graphitization degree of the product.

[0059] 6. Slow cooling and temperature reduction: After graphitization, it is gradually cooled from 3100 °C to room temperature at a cooling rate of 1.5 °C per minute. The slow cooling process effectively avoids the accumulation of internal stress and the generation of microcracks in the material.

[0060] 7. Post-treatment and detection: The cooled graphite material is treated with a mixed acid to remove residual impurities. The pickling conditions are as follows: Immerse the graphite block in a mixed solution of concentrated nitric acid and hydrofluoric acid (volume ratio 3:1), control the temperature at 60 °C, and the time is 2 hours. After treatment, it is rinsed with pure water until neutral and dried in a vacuum drying oven for 12 hours.

[0061] After detection, the product performance is as follows:

[0062]

[0063] Example 2: Preparation of high-density graphite material (isostatic pressing process);

[0064] 1. Raw material selection and treatment: Select high-purity coal-tar-based carbon pitch with a softening point of 230 °C and an industrial purity ≥ 99%. To improve the uniformity and processability of the raw material, the carbon pitch particles are dried in a drying oven at 80 °C for 6 hours to remove adsorbed moisture, and then the particle size is controlled to be 2 - 4 mm by screening.

[0065] 2. Pre-carbonization treatment: Place the dried carbon pitch particles in a tube furnace under a nitrogen protection atmosphere for pre-carbonization treatment. The heating conditions are as follows:

[0066] Heating rate: 5 °C per minute;

[0067] Target temperature: 650 °C;

[0068] Insulation time: 3 hours.

[0069] During this process, the light volatile components (such as low-molecular-weight aromatic hydrocarbons) in the carbon pitch are completely decomposed, and the residual volatile content is reduced to 8%. The pre-carbonized pitch has higher thermal stability and a preliminary carbon crystal nucleus structure, which is suitable for subsequent high-temperature treatment.

[0070] 3. Mixing and homogenization: The pre-carbonized asphalt is crushed into particles of 100 mesh (particle size about 150 μm). The following conductive enhancing materials are added according to the mass ratio: carbon nanotubes: 12% (mass ratio); graphene: 8% (mass ratio). The mixed materials are placed in a high-energy planetary ball mill for mixing and homogenization. The ball milling parameters are: rotation speed 400 rpm, processing time 40 minutes, and ball-to-material ratio 5:1. The homogenized mixture has excellent uniformity.

[0071] 4. Isostatic pressing: The mixed and homogenized materials are placed in an isostatic pressing device, and a uniform pressure of 150 MPa is applied to prepare a cylindrical green body with a uniform density distribution. The dimensions of the green body are a diameter of 40 mm and a height of 15 mm, and the density reaches 1.85 g / cm 3 .

[0072] 5. High-temperature graphitization: The formed green body is placed in an ultra-high-temperature graphitization furnace, and graphitization treatment is carried out with argon as the protective gas. The graphitization conditions are as follows: heating rate: 4 °C / minute; target temperature: 3200 °C; holding time: 10 hours. In the ultra-high-temperature environment of 3200 °C, carbon atoms are gradually rearranged into a hexagonal crystal structure, and the graphitization degree of the green body is significantly improved, and the electrical conductivity and thermal conductivity of the material are enhanced.

[0073] 6. Slow cooling and temperature reduction: After graphitization is completed, it is cooled to room temperature at a cooling rate of 1 °C / minute. The slow cooling process effectively prevents the generation of microcracks caused by high-temperature stress and maintains the integrity of the internal structure of the green body.

[0074] 7. Post-treatment and performance testing: The graphitized material is post-treated by the following steps: The graphite block is soaked in a mixed acid solution of nitric acid and hydrofluoric acid (volume ratio 3:1), soaked at 60 °C for 2 hours to remove metal impurities; rinsed with deionized water until neutral; vacuum dried at 120 °C for 12 hours. The finally obtained high-density graphite material is subjected to performance testing, and the test results are as follows:

[0075]

[0076]

[0077] The experiment verified that the isostatic pressing combined with the ultra-high-temperature graphitization process can prepare graphite materials with high density and high performance.

[0078] Example 3: Influence of different graphitization temperatures on the performance of graphite materials;

[0079] In order to study the influence of graphitization temperature on the material performance, the same raw materials and processing processes are used, and only the graphitization temperature is adjusted to investigate the influence of graphitization temperature on the product performance.

[0080] 1. Raw material selection and pre-carbonization: The raw materials are the same as those in Example 2, and high-purity carbon pitch with a softening point of 230 °C is used. The pre-carbonization process conditions are as follows: heating rate: 5 °C / min; target temperature: 600 °C; holding time: 3 hours. After pre-carbonization, the light volatile components in the carbon pitch are removed, and a pre-carbonized material with a residual volatile content of 10% is obtained.

[0081] 2. Mixing and homogenization: According to the ratio in Example 2 (12% carbon nanotubes, 8% graphene), the mixture is subjected to mixing and homogenization treatment by a high-energy ball mill to ensure the uniform dispersion of the conductive filler.

[0082] 3. Compression molding: The homogenized mixture is formed by compression molding, and a cylindrical blank (diameter 50 mm, height 20 mm) is prepared under a pressure of 30 MPa.

[0083] 4. High-temperature graphitization: The formed blank is placed in a graphitization furnace and protected by argon. The graphitization temperatures are adjusted to 2800 °C, 3000 °C, 3100 °C, and 3200 °C respectively, and other conditions are the same: heating rate: 4 °C / min; holding time: 6 hours (2800 °C and 3000 °C), 8 hours (3100 °C and 3200 °C).

[0084] 5. Slow cooling and post-treatment: After graphitization, the temperature is cooled to room temperature at a rate of 1.5 °C / min. The cooled material is soaked in a mixed acid to remove impurities, rinsed with deionized water, and vacuum dried before performance testing.

[0085] 6. Test results and analysis: The performance test results of the graphite materials prepared under different temperature conditions are as follows:

[0086]

[0087] Analysis: With the increase of the graphitization temperature, the graphitization degree, electrical conductivity, and thermal conductivity of the material are significantly improved; when the temperature rises from 2800 °C to 3200 °C, the graphitization degree increases from 87.5% to 94.2%, and the electrical conductivity increases from 15.2 S / cm to 22.5 S / cm; the performance of the graphite material under the condition of 3200 °C is the best, and the bulk density reaches 1.86 g / cm 3 , and the impurity content is less than 0.2%.

[0088] Example 4: Preparation process of graphite material for high-temperature lubricant

[0089] 1. Raw material selection and treatment: High-purity coal-tar-based carbon pitch with a softening point of 210 °C and an industrial purity of ≥98.5% is selected. To reduce the moisture content in the raw material, it is placed in a drying oven and dried at 90 °C for 12 hours. After drying, the particle diameter is controlled to be 2 - 3 mm by screening to ensure the uniformity of the subsequent process.

[0090] 2. Pre-carbonization treatment: Place the treated carbon pitch particles in a tube furnace and conduct pre-carbonization treatment under a nitrogen protection atmosphere. The heating conditions are as follows:

[0091] Heating rate: 3 °C / minute;

[0092] Target temperature: 600 °C;

[0093] Insulation time: 4 hours.

[0094] During this process, low-molecular-weight volatiles (including light aromatics and small-molecule hydrocarbons) are fully removed, and the volatile matter removal rate reaches 93%. The material after pre-carbonization treatment has a higher density and forms a preliminary carbon crystal nucleus structure.

[0095] 3. Mixing and homogenization: Crush the carbon pitch particles after pre-carbonization treatment to 100 mesh and add reinforcing materials according to the following ratio:

[0096] Graphite powder (high thermal conductivity filler, thermal conductivity > 200 W / m·K): 20%;

[0097] Graphene (conductivity and anti-friction property enhancing material): 5%.

[0098] Place the above materials in a high-energy planetary ball mill and conduct homogenization mixing at a rotation speed of 400 rpm for 60 minutes. The material after mixing has good uniformity, the reinforcing filler is evenly dispersed, and the surface coating is relatively sufficient.

[0099] 4. Isostatic pressing forming: Load the mixed and homogenized material into a mold and adopt the isostatic pressing forming process. The forming conditions are as follows:

[0100] Forming pressure: 150 MPa;

[0101] Green body size: diameter 40 mm, height 20 mm;

[0102] Forming density: 1.85 g / cm 3 .

[0103] The isostatic pressing process makes the density distribution inside the green body uniform, reduces the porosity, and provides a high-quality foundation for subsequent graphitization.

[0104] 5. High-temperature graphitization treatment: Place the formed green body in an induction heating furnace for high-temperature graphitization treatment. The graphitization conditions are as follows:

[0105] Heating rate: 3 °C / minute;

[0106] Target temperature: 3200 °C;

[0107] Insulation time: 8 hours.

[0108] During the graphitization process, carbon atoms are gradually rearranged into a hexagonal crystal structure, significantly enhancing the thermal conductivity and anti-friction properties of the material. Argon is used as a protective gas to prevent the billet from oxidizing in a high-temperature environment.

[0109] 6. Slow cooling and temperature reduction: After graphitization is completed, it is cooled to room temperature at a cooling rate of 1.5 °C per minute. The slow cooling process effectively releases the thermal stress inside the billet, avoids the generation of cracks, and at the same time ensures the structural integrity of the material.

[0110] 7. Post-treatment and finishing: The cooled graphite material is immersed in a mixed acid solution of nitric acid and hydrofluoric acid (volume ratio 3:1) and treated at 70 °C for 3 hours to remove residual impurities. Subsequently, it is rinsed with deionized water until neutral and dried in a vacuum drying oven at 120 °C for 12 hours. The dried material is crushed and size-graded according to application requirements to obtain special graphite powder for high-temperature lubricants with a particle size in the range of 10 - 20 μm.

[0111] 8. Performance testing: The prepared graphite material undergoes multiple performance tests, and the results are shown in the following table:

[0112]

[0113] 9. Application testing of high-temperature lubricant: The above-prepared graphite material is applied to a high-temperature mechanical lubrication environment (temperature range 300 - 700 °C) to test its anti-friction performance and lubrication performance. The results show that:

[0114] At a high temperature of 700 °C, the friction coefficient of the lubricant is reduced by 40%;

[0115] The material shows excellent stability and low volatility in high-temperature lubrication tests.

[0116] Analysis: In this example, an isostatic pressing process combined with an ultra-high-temperature graphitization technology was used to prepare a special graphite material for high-temperature lubrication. By adding graphite powder and graphene as reinforcing materials, the thermal conductivity and anti-friction properties of the material were significantly improved, while ensuring the high purity and excellent structural uniformity of the product. The experimental results show that this material has great market potential in high-temperature lubrication applications and meets the special needs of aerospace and industrial high-temperature equipment.

[0117] The above experimental results show that the optimization of the graphitization temperature plays a key role in improving the performance of graphite materials. Especially for high-conductivity and high-thermal-conductivity application fields, an ultra-high-temperature graphitization process at 3200 °C is recommended.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for graphitizing carbon pitch, characterized in that: The method comprises the following steps: Raw material selection and processing: Carbon pitch with a softening point of 180-250℃ is selected as the main raw material, and it is dried to remove moisture and surface adsorbed impurities; the raw material is sieved and the particle size is controlled within the range of 2-5mm; Pre-carbonization treatment: Place the screened carbon asphalt in a tubular furnace or box furnace protected by nitrogen or argon for heating treatment, and keep the gas flow rate at 1-2L / min to ensure that the reaction environment is not disturbed by oxygen. The temperature range is 500-700℃, and the heating rate is controlled at 3-5℃ / minute to ensure that the asphalt is heated evenly to avoid sudden temperature rise causing material cracking or incomplete volatilization. In this process, the temperature accuracy is required to be controlled within ±2℃ to ensure the stability of the asphalt structure. The treatment time is maintained at 2-5 hours to eliminate low molecular volatiles and impurities and form a stable pre-carbonized asphalt structure; Mixing and homogenization: crush the pre-carbonized asphalt into 50-100 meshes, add 10%-20% of high-conductivity filler by mass ratio, and use a ball mill to mix and homogenize for 30-60 minutes to ensure that the filler is evenly dispersed and enhance the conductivity and crystallinity of the subsequent graphitized material; Molding process: The mixed materials are molded by molding or isostatic pressing; High-temperature graphitization treatment: Place the preformed blank in an ultra-high temperature graphitization furnace, and gradually heat it to 3000℃-3200℃ at a heating rate of 3-5℃ / min under the protection of nitrogen or argon. Keep it in this temperature range for 3-10 hours to promote the orderly arrangement of carbon atoms and form a structure with a high degree of graphitization; Slow cooling and cooling: After graphitization is completed, gradually cool to room temperature at a cooling rate of 1-2℃ / min; Post-processing and finishing: After cooling, the graphitized material is subjected to physical or chemical methods to remove impurities. Chemical treatment can be carried out by soaking in mixed acid to remove residual metal impurities. Then, according to the product application, the desired particle size or shape is formed by screening, crushing or mechanical processing; Performance testing and grading: The processed graphite materials are subjected to performance testing, including graphitization degree, electrical conductivity, thermal conductivity and purity indicators; based on the test results, the products are graded and stored for different application scenarios.

2. The carbon pitch graphitization method according to claim 1, characterized in that: The pre-carbonization treatment is completed through a dynamic temperature control program, the heating rate is controlled at 3-5°C / minute, the insulation time is 2-5 hours, the removal rate of low molecular volatiles reaches 90%-95%, and a carbon crystal core structure is initially formed.

3. The carbon pitch graphitization method according to claim 1, characterized in that: In the mixing and homogenizing step, the filler is one or more of carbon nanotubes, graphite powder, graphene or carbon fiber, and the added amount is 10%-20% of the mass of the carbon asphalt; the mixing and homogenizing is carried out by a ball mill, and the ball milling time is controlled at 30-60 minutes.

4. The carbon pitch graphitization method according to claim 1, characterized in that: The molding process includes the following methods: Compression molding: Under a pressure of 20-40MPa, a block or columnar blank is formed by a compression molding device; Isostatic pressing: Pressurized in 100-200MPa isostatic pressing equipment, the density of the green body is uniform and the internal distribution structure is dense.

5. The carbon pitch graphitization method according to claim 1, characterized in that: The graphitization process includes the following specific optimization measures: The graphitization temperature is 3000℃-3200℃; the heating rate is 3-5℃ / minute; the insulation time is 6-10 hours, and the temperature distribution and gas flow in the furnace are monitored in real time.

6. The carbon pitch graphitization method according to claim 1, characterized in that: The slow cooling process is performed at a rate of 1-2°C / min to cool down to room temperature, thereby effectively releasing the internal stress of the graphitized material and avoiding the generation of thermal cracks and microstructural defects.

7. The carbon pitch graphitization method according to claim 1, characterized in that: The post-processing steps include the following: Soak the graphite material in a mixed acid solution of concentrated nitric acid and hydrofluoric acid to remove residual metal impurities; After being rinsed with pure water and dried, the particles are sieved to a particle size range of 20-200 μm; Depending on the application requirements, graphite materials can be coated to enhance lubricity or corrosion resistance.

8. The carbon pitch graphitization method according to claim 1, characterized in that: The prepared graphite material exhibits the following characteristics in performance testing: Graphitization degree ≥92%; Conductivity ≥20S / cm; Thermal conductivity ≥150W / m·K; Purity ≥99.5%.

9. The carbon pitch graphitization method according to claim 1, characterized in that: The prepared graphite material is suitable for the following fields: Lithium-ion battery negative electrode material with excellent cycle stability and specific capacity; Conductive material, conductivity is better than traditional graphite products; High temperature lubricants and refractory materials for machinery and equipment in extreme environments.

10. The carbon pitch graphitization method according to claim 1, characterized in that: The pre-carbonization treatment of the raw materials is synergistically optimized with the high-temperature graphitization process. The pre-carbonization step significantly reduces the volatile content and forms a preliminary carbon crystal core structure, providing an ordered crystal core for high-temperature graphitization. The lattice integrity and conductivity of the final graphitized product are significantly improved.

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