Preparation method of high-purity graphite materials

Abstract

This invention discloses a method for preparing high-purity graphite material, comprising the following steps: (1) mixing carbonaceous aggregate with asphalt and kneading under pressure to obtain a paste; (2) rolling, crushing, and sieving the paste obtained in step (1) to obtain pressed powder; subjecting the pressed powder to cold isostatic pressing to obtain green blocks; (3) subjecting the green blocks obtained in step (2) to pressure calcination to obtain calcined blocks; (4) subjecting the calcined blocks obtained in step (3) to graphitization treatment to obtain high-purity graphite material. The preparation method of this invention utilizes the synergistic effect of pressure kneading and pressure calcination to allow asphalt to spread more uniformly on the surface of carbonaceous aggregate and penetrate into the pores of the carbonaceous aggregate, forming sintering necks. Pressure calcination promotes the carbonization and ring formation of asphalt, achieving tight connection of different aggregates, improving material homogeneity, and preparing a high-purity graphite material that does not require impregnation or multiple calcinations.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials, and particularly relates to a method for preparing graphite materials. Background Technology

[0002] High-purity graphite materials are those with a carbon content of over 99.9%. They possess advantages such as low resistivity, good thermal shock resistance, high mechanical strength, high temperature resistance, corrosion resistance, self-lubrication, and ease of precision machining. They are widely used in heaters for single-crystal furnaces, graphite crystallizers for continuous casting of metals, electrode plates for hydrogen fuel cells, graphite electrodes for electrical discharge machining, and in defense technology and the nuclear industry. Currently, the preparation of high-purity graphite materials in China continues with traditional processes, using asphalt as a binder and calcined coke as aggregate, involving processes such as screening, batching, mixing, rolling, grinding, molding, calcination, impregnation, graphitization, and purification. To achieve high density and high strength, carbon-graphite material samples require multiple impregnation and calcination processes, which not only prolongs the preparation cycle, increases energy consumption, and raises production costs, but also reduces the homogeneity of the graphite material.

[0003] Patent application CN116573937A discloses a highly efficient method for preparing special carbon and its kneading process. The method involves kneading, crushing, molding, calcining, impregnating, and graphitizing raw materials. Modified asphalt is used as a binder and kneaded under pressure with coke powder, allowing the modified asphalt to penetrate evenly into the pores of the coke powder and coat the particle surface uniformly. This significantly improves the physicochemical properties of the product, resulting in a denser structure and higher yield, indicating good industrialization prospects. However, the pressure kneading method used in this patent results in a simple physical bond between the asphalt and aggregate, leading to low bond strength and significantly impacting the overall performance of the graphite material.

[0004] Therefore, existing technologies need improvement, and there is an urgent need to improve the efficiency of high-purity graphite material preparation and enhance its overall performance by modifying the raw materials themselves and improving the preparation process. Thus, providing a method for preparing high-purity graphite materials that is simple in process, short in cycle, low in production cost, and has excellent overall performance is of great significance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a method for preparing high-purity graphite materials with simple preparation process, short preparation cycle, low production cost and excellent comprehensive performance.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A method for preparing high-purity graphite material includes the following steps:

[0008] (1) Mix carbonaceous aggregate with asphalt and knead under pressure to obtain a paste;

[0009] (2) The paste obtained in step (1) is rolled, crushed and sieved to obtain pressed powder; the pressed powder is subjected to cold isostatic pressing to obtain green block;

[0010] (3) The green block obtained in step (2) is subjected to pressure roasting to obtain roasted block;

[0011] (4) The calcined block obtained in step (3) is graphitized to obtain high-purity graphite material.

[0012] In the above preparation method, preferably, the carbonaceous aggregate is first mixed with a chemical modifier, and then mixed with asphalt and kneaded under pressure. The chemical modifier includes an organic modifier and / or an inorganic modifier. The organic modifier includes one or more of oleic acid, wash oil and nitronaphthalene. The inorganic modifier includes ammonium persulfate. The mass ratio of the chemical modifier to the carbonaceous aggregate is (1-5):100.

[0013] This invention first mixes carbonaceous aggregate with a chemical modifier. The chemical modifier constructs interfacial functional groups and a free radical transition layer between the primary and secondary aggregates, possessing high chemical activity and wettability. During pressurized kneading, when the asphalt penetrates into the aggregate gaps, the aggregate and liquid asphalt are fully adsorbed and evenly spread. Furthermore, during subsequent pressurized calcination, the interfacial functional groups and the free radical transition layer exhibit self-sintering behavior. Due to the homogeneity of the asphalt-aggregate bond during pressurized kneading, the rapid migration of lightweight components in the asphalt is inhibited, resulting in a more homogeneous product. The functional groups in the chemical modifier can promote decomposition and condensation reactions, increasing the asphalt carbonization ring-forming rate, increasing the residual carbon content of the asphalt, shortening the calcination time, and improving the yield. In short, this invention first mixes carbonaceous aggregate with a chemical modifier, utilizing the chemical modifier to modify the aggregate, which is beneficial for improving the effectiveness of pressurized kneading and pressurized calcination, enhancing their synergistic effect.

[0014] In the above preparation method, more preferably, the chemical modifier includes an organic modifier and an inorganic modifier, wherein the organic modifier is wash oil and the inorganic modifier is ammonium persulfate, and the mass ratio of wash oil to ammonium persulfate is 1:(0.5-3). More preferably, the mass ratio of wash oil to ammonium persulfate is 1:2. In a more preferred embodiment, wash oil and ammonium persulfate are used in combination, and their synergistic effect results in better modification of the aggregate. Specifically, wash oil acts as a lubricant during the pressurized kneading stage, which can reduce friction between aggregate particles, improve the fluidity of the mixture, and make it easier for ammonium persulfate and asphalt to penetrate between the aggregate particles, forming a close contact. At the same time, it prevents the aggregate particles from breaking during the kneading process. Intact particles help maintain their original surface properties, allowing ammonium persulfate to react more efficiently with the aggregate surface, forming a functional group and free radical transition layer. During the subsequent pressurized kneading to promote the reaction between the modifier and aggregate, some low-boiling-point hydrocarbon molecules in the wash oil will begin to evaporate, while higher-boiling-point hydrocarbon molecules will not volatilize. The wash oil partially volatilizes and decomposes, releasing light hydrocarbons and volatile components. Under pressure, these components, along with ammonium persulfate, promote the formation of interfacial functional groups and a free radical transition layer. The unvaporized portion continues to act as a lubricant, improving the fluidity of the mixture and enhancing mass transfer efficiency during subsequent pressurized calcination. During the subsequent pressurized kneading to promote the reaction between the modifier and aggregate, ammonium persulfate decomposes to produce ammonia and sulfate ions. Ammonia reacts with carbon atoms in the aggregate to form amino functional groups, which can react with functional groups produced by asphalt. The free radicals (nitrogen and hydrogen) produced by the covalent bond breakage of ammonia at around 200℃ can also react with hydroxyl and carboxyl groups produced by asphalt to form a transition layer. Sulfate ions can react with the surface of carbon materials to form stable chemical bonds. Using ammonium persulfate as a modifier can promote the formation of interfacial functional groups and free radical transition layers, improve the bonding between asphalt and aggregate during pressurized kneading, and facilitate the obtaining of high-performance carbon materials after subsequent pressurized calcination.

[0015] In the above preparation method, preferably, the process of first mixing the carbonaceous aggregate with a chemical modifier includes the following steps:

[0016] After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of (1-3):100, carbonaceous aggregate is added, and after mixing evenly, the anhydrous ethanol is removed. Then, the mixture is placed in a pressure kneading pot and mixed at 100-110℃ for 1-2 hours with the kneading pot speed at 10-50 r / min to remove moisture.

[0017] Then, the mixture is pressed and mixed at 0.5-1 MPa for 1-3 hours at 200-250℃, with the kneading pot speed at 10-50 r / min, to obtain modified carbonaceous aggregate.

[0018] This invention first involves kneading the aggregate at 100-110℃ under normal pressure to facilitate moisture removal and ensure thorough dispersion. Then, the aggregate is pressurized and mixed at 200-250℃ and 0.5-1 MPa for 1-3 hours. During this process, the chemical modifier and carbonaceous aggregate are thoroughly mixed and react, promoting the formation of interfacial functional groups and free radical transition layers between the aggregates. This process is carried out under pressure, preferably in a very small, enclosed space, such as a container. After sealing, the remaining volume is only half the total volume of the chemical modifier and carbonaceous aggregate. Under these pressurized conditions, the synergistic effect of wash oil and ammonium persulfate is enhanced, allowing the volatile components of the wash oil and the decomposition products of ammonium persulfate to react more effectively with the carbonaceous aggregate. Simultaneously, the pressure promotes the chemical reaction between the chemical modifier and the aggregate surface, strengthening intermolecular forces.

[0019] In the above preparation method, preferably, during pressure kneading, asphalt is added to a pressure kneading pot containing modified carbonaceous aggregate, and pressure kneading is carried out in a closed space at a pressure of 0.5-3 MPa. The pressure kneading temperature is controlled at 240-270℃, the kneading time is 1-2 hours, and the volatile matter content of the paste is controlled between 11-12%. Under pressure, the fluidity of the asphalt increases, and pressure kneading allows the asphalt to continuously penetrate into the gaps between the aggregates, increasing the plasticity of the paste. This is beneficial for the carbonization and ring formation of the asphalt during subsequent pressure calcination, achieving a tight bond between different aggregates. Pressure kneading at 0.5-3 MPa causes the volatile components in the asphalt to volatilize. Maintaining the asphalt volatiles as the pressure atmosphere, the pressure of the volatiles helps to push the asphalt into tiny pores, thereby increasing the saturation of the carbon materials. Aromatic hydrocarbon molecules in the asphalt volatiles readily undergo polymerization reactions, forming larger polymer molecules, promoting the reaction between aromatic hydrocarbon molecules, increasing the molecular weight and cross-linking degree of the asphalt, thereby improving its adhesion and adsorption properties. Meanwhile, the sulfur, nitrogen, and other heteroatoms in the volatile matter of asphalt can act as catalysts, promoting cross-linking reactions between asphalt molecules. During subsequent pressure calcination, the various components in the asphalt undergo decomposition and condensation reactions with the aggregate, resulting in uniform shrinkage of the green body and improved yield. Furthermore, after modification with chemical modifiers, under pressure, asphalt can better react with the functional groups on the surface of carbon materials to form chemical bonds, thereby enhancing the interaction force between asphalt and carbon materials.

[0020] In the above preparation method, preferably, the carbonaceous aggregate comprises calcined petroleum coke aggregate (main aggregate) with a D50 of 15-20 μm and graphite powder (secondary aggregate) with a D50 of 1-5 μm, wherein the mass ratio of the calcined petroleum coke aggregate to the graphite powder is (7-9):(1-3). By controlling the particle size ratio and mass ratio of the main aggregate and the secondary aggregate, the large particles of the main aggregate form the skeleton, and the secondary aggregate fills the gaps between the large particles, making the aggregate packing more compact.

[0021] In the above preparation method, preferably, the asphalt is high-temperature molten asphalt with a softening point of 160-200℃, and the mass ratio of carbonaceous aggregate to asphalt is (7-9):(1-3). This invention uses high-temperature molten asphalt, which is more effective than modified asphalt. This is because the high-temperature molten asphalt has a better synergistic effect with the pressure mixing and pressure calcination of this application. During the pressure mixing stage, the high-temperature molten asphalt has high fluidity, which allows the asphalt to better penetrate between carbon material particles, forming a close contact. Simultaneously, during the pressure calcination stage, the volatiles in the high-temperature molten asphalt diffuse and transfer more easily at high temperatures, which helps the beneficial components in the asphalt migrate more quickly to the surface and interior of the carbon material, further enhancing the effect of subsequent pressure calcination.

[0022] The mass ratio of carbonaceous aggregate to bitumen is (7-9):(1-3). The reason for this limitation is as follows:

[0023] On the one hand, the use of two types of aggregates, with smaller particles filling the gaps between larger particles, results in uniform pores and a suitable specific surface area on the aggregate surface. Controlling the aforementioned mass ratio allows for thorough adsorption of the aggregates and asphalt. On the other hand, controlling this mass ratio, during pressurized mixing, utilizes asphalt volatiles as a pressurizing atmosphere, enhancing the asphalt's adsorption capacity. In subsequent firing, the pressure increases the shrinkage of the green body, allowing volatile gases to penetrate into the interior of the green body, causing condensation reactions to deposit internally and improving the material's density.

[0024] In the above preparation method, preferably, the process of rolling, crushing, and sieving the paste to obtain pressed powder includes the following steps: rolling the paste into sheets 1-3 times, with a sheet thickness of 1-2 mm, the rolling temperature corresponding to the pressure kneading temperature, cooling, crushing, passing through a 160-325 mesh sieve, and mixing for 0.5-1 h to obtain pressed powder.

[0025] During cold isostatic pressing, the powder is loaded into the mold sleeve of the isostatic pressing mold, vibrated and then vacuum sealed. It is then placed in a cold isostatic pressing equipment and pressed at 150-200MPa for 5-20 minutes. After the pressure is released, the green block is obtained.

[0026] In the above preparation method, preferably, the pressure calcination is carried out in a closed space at a pressure of 0.1-3 MPa, at 800-1200℃ for 2-4 hours, followed by cooling to obtain the calcined block. Controlling the calcination pressure to 0.1-3 MPa helps ensure the effectiveness of the pressure calcination while not placing high demands on the equipment's capacity.

[0027] In the above preparation method, preferably, the graphitization treatment is carried out at 2000-3000℃ for 1-2 hours, followed by cooling, to obtain high-purity graphite material.

[0028] The preparation method of high-purity graphite material in this invention may more specifically include the following steps:

[0029] (1) Calcined petroleum coke aggregate with a particle size D50 of 15-20 μm and artificial graphite powder, flake graphite powder (high purity) or high power graphite electrode powder with a D50 of 1-5 μm are prepared by Raymond mill and high energy air jet mill. The chemical modifier is one or more of oleic acid, wash oil, nitronaphthalene and ammonium persulfate.

[0030] (2) Add the calcined petroleum coke obtained in step (1) and the graphite powder obtained in step (1) to a mixer in a mass ratio of 7-9:1-3 and mix for 1-2 hours. The mixture is uniform and there is no particle segregation, thus obtaining carbonaceous aggregate.

[0031] (3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 1-3:100, carbonaceous aggregate is added at a mass ratio of 1-5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and mixed at 100-110℃ for 1-2 hours with a kneading pot speed of 10-50 r / min to remove moisture. Then, the mixture is pressure-mixed at 200-250℃ and 0.5-1 MPa for 1-3 hours with a kneading pot speed of 10-50 r / min to obtain modified carbonaceous aggregate.

[0032] (4) Add high-temperature molten asphalt with a softening point of 160-200℃ to a pressure kneading pot at a mass ratio of 7-9:1-3, and knead under pressure of 0.5-3MPa. The pressure kneading temperature is controlled at 240-270℃, the kneading time is 1-2h, and the volatile matter of the paste is controlled between 11-12%.

[0033] (5) After kneading, roll the paste obtained in step (4) into sheets 1-3 times, with a sheet thickness of 1-2 mm. The rolling temperature corresponds to the kneading temperature. After cooling to room temperature, crush the paste, pass it through a 160-325 mesh sieve, and mix it for 0.5-1 h to obtain pressed powder.

[0034] (6) The pressed powder obtained in step (5) is placed into the mold sleeve of an isostatic pressing mold, compacted by vibration, vacuum sealed, and placed in a cold isostatic pressing device. After pressing at 150-200 MPa for 5-20 minutes, the pressure is gradually released, the sample is taken out, the sealing tape is peeled off, and after being left for 2-10 hours, a density of 1.55-1.60 g / cm³ can be obtained. 3 The green blank;

[0035] (7) Place the green body prepared in step (6) into a graphite crucible. After the six sides of the green body are filled with sintering material, place it in a calcining furnace. During the calcination process, argon / nitrogen gas is introduced, and the pressure inside the furnace is maintained at 0.1-3 MPa. The pressure is maintained and calcination is carried out according to the set temperature curve. After the temperature is controlled to drop to 150-300℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.59-1.70 g / cm³. 3 calcined blocks;

[0036] (8) Place the calcined block obtained in step (7) into a vacuum graphitization furnace under a protective atmosphere and treat it at 2000-3000℃ for 1-2 hours. After the temperature is controlled to drop to 100-300℃, allow it to cool naturally to room temperature to obtain a density of 1.65-1.85 g / cm³. 3 The graphitized bulk material is high-purity graphite material.

[0037] To address the problems of long production cycles, high production costs, and low material homogeneity caused by multiple impregnation and calcination in traditional methods for preparing high-purity graphite materials, this invention uses one or more of oleic acid, wash oil, nitronaphthalene, and ammonium persulfate as chemical modifiers. Utilizing the strong electron-withdrawing ability of their chemical groups, the modifiers are first mixed with carbonaceous aggregates to modify them. During pressurized kneading, the chemical modifiers, under pressure, create interfacial functional groups and free radical transition layers between the primary and secondary aggregates. (The chemical modifiers enhance the adhesion between the primary and secondary aggregates through chemical bonding, improving the overall quality.) The stability of the structure contributes to the formation of interfacial functional groups. Simultaneously, the resulting free radical transition layer provides additional interaction forces between primary and secondary aggregates through covalent or non-covalent bonds. This allows for the formation of interfacial functional groups and a free radical transition layer between the primary and secondary aggregates, exhibiting high chemical activity and wettability. During subsequent pressure kneading with asphalt, the chemical groups promote the polymerization of aromatic free radicals in the binder, making the binder asphalt easier to wet and spread evenly on the surface of the carbonaceous aggregate. It also penetrates quickly into the pores of the carbonaceous aggregate, forming a uniformly kneaded paste with good homogeneity. Simultaneously, asphalt also promotes the formation of interfacial functional groups and a free radical transition layer. The chemical reaction of asphalt also forms free radicals and functional groups, which react with the free radicals or functional groups on the surface of the modified carbon materials to form stable chemical bonds, resulting in a tighter bond and better kneading effect. During the pressure roasting stage, the release of volatiles can be suppressed, resulting in homogenized products. Under pressure, the chemical modifier causes unstable molecules that should have pyrolyzed and volatilized during carbonization to polymerize into stable polycyclic aromatic hydrocarbon macromolecules, which remain in the binder carbon. Simultaneously, the generated intermediates are converted into polycyclic aromatic hydrocarbons, further associating binder molecules into macromolecules, promoting the binder dehydrogenation condensation reaction, catalyzing coking condensation, and causing the interfacial functional groups and free radical transition layer to exhibit self-sintering behavior. This allows the macromolecules, which are uniformly spread and penetrated into the aggregate surface and pores, to effectively form sintering necks between the carbonaceous aggregates. Simultaneously, under pressure, during roasting, the aromatic free radicals generated by the binder first attack the oxygen on the chemical groups and are consumed, prematurely terminating the thermal decomposition reaction of the generated free radicals. This avoids the pyrolysis and release of a large number of unstable components in the form of volatiles, increasing the residual char content and improving the overall performance of the material.

[0038] Unlike the common pressurization method that introduces inert gas, this invention uses pressurized kneading without introducing inert gas. Instead, it relies on the combined action of air and asphalt volatiles as the pressurizing atmosphere. Pressure is maintained by the up-and-down movement of a pressure valve piston, resulting in simple operation and cost savings. Simultaneously, the asphalt volatiles, acting as the pressurizing atmosphere, maintain the activity of the α and β components. During kneading, this facilitates the bonding and adsorption of asphalt with aggregates, ensuring uniform asphalt distribution and laying the foundation for subsequent pressurized calcination. Using air as the pressurizing atmosphere increases the cross-linking degree of the asphalt, thereby improving the strength of the graphite material.

[0039] Compared with the prior art, the advantages of the present invention are as follows:

[0040] The preparation method of this invention, through process improvement, utilizes the synergistic effect of pressurized kneading and pressurized calcination to allow asphalt to spread more uniformly on the surface of carbonaceous aggregates and penetrate into the pores of the carbonaceous aggregates, forming sintering necks. Furthermore, pressurized calcination promotes the carbonization and ring formation of the asphalt, achieving tight bonding between different aggregates, improving material homogeneity, and producing a high-purity graphite material that requires no impregnation or multiple calcinations. This enhances the overall performance of the material, shortens the production cycle, and increases the company's capacity and profits. Attached Figure Description

[0041] 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.

[0042] Figure 1 The figures show the test results of the flexural strength and compressive strength of the high-purity graphite material in Example 1, as well as the corresponding cross-sectional microstructure diagrams (in the figures, (a) is the flexural strength diagram, (c) is the compressive strength diagram, (b) is the 5μm cross-sectional microstructure diagram, and (d) is the 10μm cross-sectional microstructure diagram).

[0043] Figure 2 The images show the surface polarization pattern and surface microstructure of the high-purity graphite material in Example 1 (in the images, (a) is the 100μm surface polarization pattern, (c) is the 500μm surface polarization pattern, (b) is the 5μm surface microstructure, and (d) is the 20μm surface microstructure).

[0044] Figure 3 The figures show the test results of the flexural strength and compressive strength of the high-purity graphite material in Comparative Example 1, as well as the corresponding cross-sectional microstructures (in the figures, (a) is the flexural strength figure, (c) is the compressive strength figure, (b) is the 5μm cross-sectional microstructure, and (d) is the 10μm cross-sectional microstructure).

[0045] Figure 4 The images show the surface polarization pattern and surface microstructure of the high-purity graphite material in Comparative Example 1 (in the images, (a) is the surface polarization pattern at 100 μm, (c) is the surface polarization pattern at 500 μm, (b) is the surface microstructure at 5 μm, and (d) is the surface microstructure at 20 μm). Detailed Implementation

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Example 1:

[0050] A method for preparing high-purity graphite material includes the following steps:

[0051] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill. Wash oil and ammonium persulfate were used as chemical modifiers. High-temperature molten asphalt with a softening point of 170℃ was prepared for use.

[0052] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour; prepare a chemical modifier by mixing the wash oil and ammonium persulfate at a mass ratio of 1:2.

[0053] 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is pressure-mixed at 210℃ and 1 MPa for 2.5 hours at a speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0054] 4) Add the high-temperature molten asphalt to a pressure kneading pot containing modified carbonaceous aggregate at a mass ratio of 7:3 for the mixed powder and high-temperature molten asphalt. Maintain pressure of 3MPa for kneading, control the kneading temperature at 250℃, and knead for 1 hour. After kneading, quickly transfer the paste to the material hopper of a rolling mill, roll it 3 times, with a rolling thickness of 2mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material. After the material temperature drops to room temperature, let it stand for 10 hours before crushing and grinding. Pass the powder through a 200-mesh sieve, and then mix it for 0.5 hours to obtain pressed powder.

[0055] 5) Press the powder obtained in step 4) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.60 g / cm³. 3 The green blank.

[0056] 6) Place the green body prepared in step 5) in a graphite crucible. After the six sides of the green body are filled with sintering material, place it in a tube furnace. During the calcination process, argon / nitrogen gas is introduced and the furnace pressure is maintained at 3 MPa. Calcination is carried out 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 The roasted blocks.

[0057] 7) The calcined block obtained in step 6) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was allowed to cool naturally to room temperature, resulting in a density of 1.83 g / cm³. 3 The graphitized bulk material is a type of graphitized graphite material.

[0058] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 6) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.83 g / cm³. 3 The open porosity is 11.0%, the resistivity is 12.8 μΩ·m, the flexural strength is 61.85 MPa, the compressive strength is 120.27 MPa, and the Shore hardness is 77 HSD.

[0059] The test results of the flexural strength and compressive strength of the graphite material obtained in this embodiment are as follows: Figure 1 (a) and Figure 1 As shown in (c), the cross-sectional microstructures of the flexural strength and compressive strength are respectively as follows: Figure 1 (b) and Figure 1 As shown in (d), by Figure 1 (a) and Figure 1 As shown in (c), the flexural strength and compressive strength of the graphite material are 61.85 MPa and 120.27 MPa, respectively, representing a significant improvement in performance compared to graphite materials prepared using traditional processes. The corresponding microstructure images show that the aggregates are tightly connected, exhibiting high density, and the pores between particles are small, with an average pore diameter of less than 2 μm; no through-holes are observed. Figure 2 As shown in the surface polarization pattern and surface microstructure diagram, the sample exhibits a relatively uniform pore structure with generally small pore sizes, mostly consisting of single, independent pores. Therefore, the resulting graphite material demonstrates excellent flexural and compressive strength.

[0060] Example 2:

[0061] A method for preparing high-purity graphite material includes the following steps:

[0062] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill. Oleic acid and ammonium persulfate were used as chemical modifiers. High-temperature molten asphalt with a softening point of 170℃ was prepared for use.

[0063] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour; prepare a chemical modifier by mixing oleic acid and ammonium persulfate at a mass ratio of 1:2.

[0064] 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is pressure-mixed at 210℃ and 1 MPa for 2.5 hours at a speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0065] 4) Add the high-temperature molten asphalt to a pressure kneading pot containing modified carbonaceous aggregate at a mass ratio of 7:3 for the mixed powder and high-temperature molten asphalt. Maintain pressure of 1 MPa for kneading, control the kneading temperature at 250℃, and knead for 1 hour. After kneading, quickly transfer the paste to the material hopper of a rolling mill, roll it 3 times, with a rolling thickness of 2 mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material. After the material temperature drops to room temperature, let it stand for 10 hours, then crush and grind it, pass it through a 200-mesh sieve, and mix it again for 0.5 hours to obtain pressed powder.

[0066] 5) Press the powder obtained in step 4) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.58 g / cm³. 3 The green blank.

[0067] 6) Place the green body prepared in step 5) in a graphite crucible, and after the six sides of the green body are filled with sintering material, place it in a tube furnace. During the calcination process, argon / nitrogen gas is introduced and the pressure inside the furnace is maintained at 1 MPa. Calcination is carried out at 1050℃ for 4 hours. After the temperature is controlled by a program to drop to 200℃, it is allowed to cool naturally to room temperature, resulting in a density of 1.64 g / cm³. 3 The roasted blocks.

[0068] 7) The calcined block obtained in step 6) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was allowed to cool naturally to room temperature, resulting in a density of 1.81 g / cm³. 3 The graphitized bulk material is a type of graphitized graphite material.

[0069] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 6) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.81 g / cm³. 3 The open porosity is 12.0%, the resistivity is 13.2 μΩ·m, the flexural strength is 59.82 MPa, the compressive strength is 113.44 MPa, and the Shore hardness is 69 HSD.

[0070] Example 3:

[0071] A method for preparing high-purity graphite material includes the following steps:

[0072] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill; nitronaphthalene and ammonium persulfate were used as chemical modifiers; and high-temperature molten asphalt with a softening point of 170℃ was prepared for use.

[0073] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour; prepare a chemical modifier by mixing nitronaphthalene and ammonium persulfate at a mass ratio of 1:2.

[0074] 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is pressure-mixed at 210℃ and 1 MPa for 2.5 hours at a speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0075] 4) Add the high-temperature molten asphalt to a pressure kneading pot containing modified carbonaceous aggregate at a mass ratio of 7:3 for the mixed powder and high-temperature molten asphalt. Maintain pressure of 3MPa for kneading, control the kneading temperature at 250℃, and knead for 1 hour. After kneading, quickly transfer the paste to the material hopper of a rolling mill, roll it 3 times, with a rolling thickness of 2mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material. After the material temperature drops to room temperature, let it stand for 10 hours before crushing and grinding. Pass the powder through a 200-mesh sieve, and then mix it for 0.5 hours to obtain pressed powder.

[0076] 5) Press the powder obtained in step 4) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.57 g / cm³. 3 The green blank.

[0077] 6) Place the 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 calcination process, argon / nitrogen gas is introduced and the furnace pressure is maintained at 3 MPa. Calcination is carried out 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 1.62 g / cm³. 3 The roasted blocks.

[0078] 7) The calcined block obtained in step 6) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was allowed to cool naturally to room temperature, resulting in a density of 1.78 g / cm³. 3 The graphitized bulk material is a type of graphitized graphite material.

[0079] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 6) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.78 g / cm³. 3 The open porosity is 13.2%, the resistivity is 14.1 μΩ·m, the flexural strength is 45.57 MPa, the compressive strength is 106.78 MPa, and the Shore hardness is 58 HSD.

[0080] Example 4:

[0081] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill. Wash oil was used as a chemical modifier. High-temperature molten asphalt with a softening point of 170℃ was prepared for use.

[0082] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour.

[0083] 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is pressure-mixed at 210℃ and 1 MPa for 2.5 hours at a speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0084] 4) Add the high-temperature molten asphalt to a pressure kneading pot containing modified carbonaceous aggregate at a mass ratio of 7:3 for the mixed powder and high-temperature molten asphalt. Maintain pressure of 3MPa for kneading, control the kneading temperature at 250℃, and knead for 1 hour. After kneading, quickly transfer the paste to the material hopper of a rolling mill, roll it 3 times, with a rolling thickness of 2mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material. After the material temperature drops to room temperature, let it stand for 10 hours before crushing and grinding. Pass the powder through a 200-mesh sieve, and then mix it for 0.5 hours to obtain pressed powder.

[0085] 5) Press the powder obtained in step 4) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.55 g / cm³. 3 The green blank.

[0086] 6) Place the green body prepared in step 5) in 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 pressure is maintained at 3 MPa. Sinter at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, allow it to cool naturally to room temperature to obtain a density of 1.59 g / cm³. 3 The roasted blocks.

[0087] 7) The calcined block obtained in step 6) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was allowed to cool naturally to room temperature, resulting in a density of 1.70 g / cm³. 3 The graphitized bulk material is a type of graphitized graphite material.

[0088] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 7) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.70 g / cm³. 3 The open porosity is 13.8%, the resistivity is 15.1 μΩ·m, the flexural strength is 40.58 MPa, the compressive strength is 96.47 MPa, and the Shore hardness is 53 HSD.

[0089] Example 5:

[0090] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill, with ammonium persulfate as a chemical modifier; high-temperature molten asphalt with a softening point of 170℃ was prepared for use.

[0091] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour.

[0092] 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is pressure-mixed at 210℃ and 1 MPa for 2.5 hours at a speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0093] 4) Add the high-temperature molten asphalt to a pressure kneading pot containing modified carbonaceous aggregate at a mass ratio of 7:3 for the mixed powder and high-temperature molten asphalt. Maintain pressure of 3MPa for kneading, control the kneading temperature at 250℃, and knead for 1 hour. After kneading, quickly transfer the paste to the material hopper of a rolling mill, roll it 3 times, with a rolling thickness of 2mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material. After the material temperature drops to room temperature, let it stand for 10 hours before crushing and grinding. Pass the powder through a 200-mesh sieve, and then mix it for 0.5 hours to obtain pressed powder.

[0094] 5) Press the powder obtained in step 4) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.56 g / cm³. 3 The green blank.

[0095] 6) Place the green body prepared in step 5) in 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 pressure is maintained at 3 MPa. Sinter at 1050℃ for 4 hours. After the temperature is controlled to drop to 200℃, it is allowed to cool naturally to room temperature, yielding a density of 1.61 g / cm³. 3 The roasted blocks.

[0096] 7) The calcined block obtained in step 6) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was allowed to cool naturally to room temperature, resulting in a density of 1.72 g / cm³. 3 The graphitized bulk material is a type of graphitized graphite material.

[0097] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 6) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.72 g / cm³. 3 The open porosity is 13.6%, the resistivity is 14.7 μΩ·m, the flexural strength is 42.66 MPa, the compressive strength is 100.68 MPa, and the Shore hardness is 56 HSD.

[0098] Example 6:

[0099] Compared to Example 1, the main difference lies in step 3), while all other conditions remain the same. Step 3) is as follows:

[0100] Step 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in Step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is mixed at 210℃ and normal pressure for 2.5 hours at a kneading pot speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0101] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 6) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.82 g / cm³. 3 The open porosity is 11.5%, the resistivity is 13.1 μΩ·m, the flexural strength is 60.16 MPa, the compressive strength is 115.62 MPa, and the Shore hardness is 74 HSD.

[0102] Comparative Example 1:

[0103] A method for preparing high-purity graphite material includes the following steps:

[0104] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill. Wash oil and ammonium persulfate were used as chemical modifiers. High-temperature molten asphalt with a softening point of 170℃ was prepared for use.

[0105] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour; prepare a chemical modifier by mixing the wash oil and ammonium persulfate at a mass ratio of 1:2.

[0106] 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is mixed at 210℃ and atmospheric pressure for 2.5 hours at a kneading pot speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0107] 4) Add the high-temperature molten asphalt to a pressurized kneading pot containing modified carbonaceous aggregate at a mass ratio of 7:3 (mixed powder and high-temperature molten asphalt). Do not pressurize. Control the kneading temperature at 250℃ and knead for 1 hour. After kneading, quickly transfer the paste to the material hopper of a rolling mill. Roll the material three times to a thickness of 2mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material until it reaches room temperature. Let it stand for 10 hours, then crush and grind it. Pass the powder through a 200-mesh sieve and mix it again for 0.5 hours to obtain pressed powder.

[0108] 5) Press the powder obtained in step 4) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.50 g / cm³. 3 The green blank.

[0109] 6) Place the 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 calcination process, argon / nitrogen gas is introduced and the furnace pressure is maintained at 0.1 MPa (atmospheric pressure). Calcination is carried out 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 1.54 g / cm³. 3 The roasted blocks.

[0110] 7) The calcined block obtained in step 6) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was allowed to cool naturally to room temperature, resulting in a density of 1.73 g / cm³.3 The graphitized bulk material is a type of graphitized graphite material.

[0111] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 6) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.73 g / cm³. 3 The open porosity is 14.0%, the resistivity is 15.4 μΩ·m, the flexural strength is 39.61 MPa, the compressive strength is 87.99 MPa, and the Shore hardness is 54 HSD.

[0112] The test results of the flexural strength and compressive strength of the graphite material obtained in this comparative example are as follows: Figure 3 (a) and Figure 1 As shown in (c), the cross-sectional microstructures of the flexural strength and compressive strength are respectively as follows: 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 39.61 MPa and 87.99 MPa, respectively, which are inferior to the graphite material prepared by pressure kneading in Example 1. The corresponding microstructure images show that the aggregates are not tightly bonded, have many cracks, and exhibit poor structural density. Figure 4 As shown in the surface polarization diagram and surface microstructure diagram, the sample has poor uniformity in pore structure distribution and large pore size.

[0113] Comparative Example 2:

[0114] A method for preparing high-purity graphite material includes the following steps:

[0115] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill. Wash oil and ammonium persulfate were used as chemical modifiers to prepare modified asphalt with a softening point of 105℃, which were then ready for use.

[0116] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour; prepare a chemical modifier by mixing the wash oil and ammonium persulfate at a mass ratio of 1:2.

[0117] 3) After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of 2:100, the carbonaceous aggregate obtained in step 2) is added at a mass ratio of 5:100. After mixing evenly, the anhydrous ethanol is removed, and then the mixture is placed in a pressure kneading pot and dry-mixed at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Then, it is pressure-mixed at 210℃ and 1 MPa for 2.5 hours at a speed of 10 r / min to obtain the modified carbonaceous aggregate.

[0118] 4) When the temperature is lowered to 150℃, add the modified asphalt to the pressurized kneading pot containing modified carbonaceous aggregate at a mass ratio of 7:3 (mixed powder and modified asphalt). Maintain the pressure at 3MPa for pressurized kneading, control the kneading temperature at 190℃, and knead for 1 hour. After kneading, quickly transfer the paste to the material hopper of the rolling mill, roll it 3 times, with a rolling thickness of 2mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material. After the material temperature drops to room temperature, let it stand for 10 hours, then crush and grind it, pass it through a 200-mesh sieve, and mix it again for 0.5 hours to obtain pressed powder.

[0119] 5) Press the powder obtained in step 4) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.45 g / cm³. 3 The green blank.

[0120] 6) Place the 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 calcination process, argon / nitrogen gas is introduced and the furnace pressure is maintained at 3 MPa. Calcination is carried out 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 1.50 g / cm³. 3 The roasted blocks.

[0121] 7) The calcined block obtained in step 6) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was naturally cooled to room temperature, resulting in a density of 1.66 g / cm³. 3 The graphitized bulk material is a type of graphitized graphite material.

[0122] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 7) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.66 g / cm³. 3The open porosity is 14.1%, the resistivity is 15.3 μΩ·m, the flexural strength is 36.84 MPa, the compressive strength is 77.07 MPa, and the Shore hardness is 50 HSD.

[0123] Comparative Example 3:

[0124] A method for preparing high-purity graphite material includes the following steps:

[0125] 1) Calcined petroleum coke with a particle size D50 of 17 μm and artificial graphite powder with a D50 of 5 μm were prepared using Raymond mill and high-energy air jet mill; high-temperature molten asphalt with a softening point of 170℃ was prepared for use.

[0126] 2) Add the calcined petroleum coke obtained in step 1) and the graphite powder obtained in step 1) to a mixer at a mass ratio of 8:2 and mix for 1 hour.

[0127] 3) Add the mixed aggregate obtained in step 2) to a pressure kneading pot and dry mix at 110℃ for 1 hour at a speed of 10 r / min to remove moisture. Continue heating to 210℃, add high-temperature molten asphalt at a mass ratio of 7:3 (mixed powder to high-temperature molten asphalt), and melt it to the corresponding temperature. Do not perform pressure kneading. Control the kneading temperature at 250℃, the kneading speed at 50 r / min, and the kneading time at 1 hour. After kneading, quickly transfer the paste to the material hopper of the rolling mill, roll it 3 times, with a rolling thickness of 2 mm. The rolling temperature corresponds to the kneading temperature. After rolling, cool the material. After the material temperature drops to room temperature, let it stand for 10 hours, then crush and grind it. Pass it through a 200-mesh sieve, and then mix it for 0.5 hours to obtain pressed powder.

[0128] 4) Press the powder obtained in step 3) into a block at 1 MPa for 60 seconds, vacuum seal it in a bag, and let it stand for 2-10 hours. Then, place it in a cold isostatic press and press it at 200 MPa for 10 minutes. After gradually releasing the pressure, take out the sample, peel off the sealing tape, and let it stand for 10 hours to obtain a sample with a density of 1.46 g / cm³. 3 The green blank.

[0129] 5) Place the 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 calcination process, argon / nitrogen gas is introduced and the furnace pressure is maintained at 0.1 MPa (atmospheric pressure). Calcination is carried out 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 1.49 g / cm³. 3 The roasted blocks.

[0130] 6) The calcined block obtained in step 5) was placed in a vacuum graphitization furnace under a protective atmosphere and treated at 2500℃ for 2 hours. After the temperature was controlled to drop to 300℃, it was allowed to cool naturally to room temperature, resulting in a density of 1.67 g / cm³. 3 The graphitized bulk material is a type of graphitized graphite material.

[0131] Referring to the YB / T4379-2014 standard, the graphite material obtained in step 6) was tested for bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness. The measured bulk density was 1.67 g / cm³. 3 The open porosity is 13.4%, the resistivity is 14.5 μΩ·m, the flexural strength is 34.89 MPa, the compressive strength is 69.56 MPa, and the Shore hardness is 47 HSD.

[0132] Ultra-high purity isostatic graphite materials were prepared according to the methods in Examples 1-6 and Comparative Examples 1-3, and the bulk density, open porosity, resistivity, flexural strength, compressive strength, and Shore hardness were calculated according to the YB / T4379-2014 standard. The measurement results are shown in Table 1 below.

[0133] Table 1: Performance data of graphite materials in Examples 1-6 and Comparative Examples 1-3

[0134] Example 1 <![CDATA[1.83g / cm 3 ]]> 11.0％ 12.8 μΩ·m 61.85MPa 120.27MPa 77HSD Example 2 <![CDATA[1.81g / cm 3 ]]> 12.0％ 13.2 μΩ·m 59.82MPa 113.44MPa 69HSD Example 3 <![CDATA[1.78g / cm 3 ]]> 13.2％ 14.1 μΩ·m 45.57MPa 106.78MPa 58HSD Example 4 <![CDATA[1.70g / cm 3 ]]> 13.8％ 15.1 μΩ·m 40.58MPa 96.47MPa 53HSD Example 5 <![CDATA[1.72g / cm 3 ]]> 13.6％ 14.7 μΩ·m 42.66MPa 100.68MPa 56HSD Example 6 <![CDATA[1.82g / cm 3 ]]> 11.5％ 13.1 μΩ·m 60.16MPa 115.62MPa 74HSD Comparative Example 1 <![CDATA[1.73g / cm 3 ]]> 14.0％ 15.4 μΩ·m 39.61MPa 87.99MPa 54HSD Comparative Example 2 <![CDATA[1.66g / cm 3 ]]> 14.1％ 15.3 μΩ·m 36.84MPa 77.07MPa 50HSD Comparative Example 3 <![CDATA[1.67g / cm 3 ]]> 13.4％ 14.5 μΩ·m 34.89MPa 69.56MPa 47HSD

[0135] It can be seen from Table 1 above:

[0136] In Example 1, washing oil and ammonium persulfate were used as chemical modifiers, and the graphite material with the best performance was obtained by synergistic pressure kneading and pressure calcination.

[0137] A comparison of Examples 1 and 2 shows that wash oil and ammonium persulfate are preferred as chemical modifiers. Furthermore, pressure kneading and calcination at 3 MPa are superior to pressure kneading and calcination at 1 MPa. During the kneading stage, the degree of crosslinking of the asphalt is increased, promoting the polymerization of macromolecules in the asphalt. During the calcination stage, it is more conducive to the formation of sintering necks. The resulting graphite material has higher bulk density, lower open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness.

[0138] A comparison of Examples 1 and 3 shows that using washing oil and ammonium persulfate as chemical modifiers results in graphite materials with higher bulk density, lower open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness.

[0139] A comparison of Examples 1 and 4 shows that using wash oil and ammonium persulfate in combination as chemical modifiers results in graphite materials with higher bulk density, lower open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness than using wash oil alone as a chemical modifier.

[0140] A comparison of Examples 1 and 5 shows that using wash oil and ammonium persulfate in combination as chemical modifiers results in graphite materials with higher bulk density, lower open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness than using ammonium persulfate alone as a chemical modifier.

[0141] A comparison of Examples 1 and 6 shows that using wash oil and ammonium persulfate in combination as chemical modifiers, and using pressurized kneading when modifying aggregates with chemical modifiers, results in graphite materials with higher bulk density, lower open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness compared to kneading under normal pressure.

[0142] As can be seen from the comparison between Example 1 and Comparative Example 1, when washing oil and ammonium persulfate are added alone as chemical modifiers without the synergistic effect of pressure kneading and pressure calcination, the green body density is low and the residual carbon content during calcination is low, which is not conducive to the formation of sintering necks during carbonization. However, the graphite material prepared by the synergistic effect of pressure kneading and pressure calcination under the action of chemical modifiers has higher bulk density, smaller open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness.

[0143] A comparison of Example 1 and Comparative Example 2 shows that using high-temperature molten asphalt as a binder is optimal, demonstrating the advantages of high-temperature molten asphalt under the synergistic effect of pressurized kneading and pressurized calcination. During the kneading stage, the modified asphalt has low wettability and weak polymerization ability of macromolecules, which is even more unfavorable for the formation of sintering necks during the calcination stage. Only under the action of chemical modifiers, high-temperature molten asphalt, through the synergistic effect of pressurized kneading and pressurized calcination, can produce graphite materials with higher bulk density, smaller open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness.

[0144] As can be seen from the comparison between Example 1 and Comparative Example 3, only the graphite material prepared by using wash oil and ammonium persulfate as chemical modifiers, and simultaneously employing the synergistic effect of 3MPa pressure kneading and 3MPa pressure calcination, has higher bulk density, lower open porosity, lower resistivity, higher flexural strength and compressive strength, and higher Shore hardness.

Claims

1. A method for preparing high-purity graphite material, characterized in that, Includes the following steps: (1) Mix carbonaceous aggregate with asphalt and knead under pressure to obtain a paste; (2) The paste obtained in step (1) is rolled, crushed and sieved to obtain pressed powder; the pressed powder is subjected to cold isostatic pressing to obtain green block; (3) The green block obtained in step (2) is subjected to pressure roasting to obtain roasted block; (4) The calcined block obtained in step (3) is graphitized to obtain high-purity graphite material; The carbonaceous aggregate is first mixed with a chemical modifier, and then mixed with asphalt and kneaded under pressure. The chemical modifier includes an organic modifier and an inorganic modifier. The organic modifier is wash oil, and the inorganic modifier is ammonium persulfate. The mass ratio of wash oil to ammonium persulfate is 1:(0.5-3). The process of mixing the carbonaceous aggregate with the chemical modifier includes the following steps: After the chemical modifier and anhydrous ethanol are stirred and dispersed evenly at a mass ratio of (1-3):100, carbonaceous aggregate is added, and after mixing evenly, the anhydrous ethanol is removed. Then, the mixture is placed in a pressure kneading pot and mixed at 100-110℃ for 1-2 hours with the kneading pot speed at 10-50 r / min to remove moisture. Then, at 200-250℃ and 0.5-1MPa, the mixture is pressurized and mixed for 1-3 hours with a kneading speed of 10-50 r / min to obtain modified carbonaceous aggregate.

2. The preparation method according to claim 1, characterized in that, During pressurized kneading, asphalt is added to a pressurized kneading pot containing modified carbonaceous aggregate. The kneading is carried out in a closed space at a pressure of 0.5-3 MPa. The pressurized kneading temperature is controlled at 240-270℃, the kneading time is 1-2 hours, and the volatile matter content of the paste is controlled between 11-12%.

3. The preparation method according to claim 1, characterized in that, The carbonaceous aggregate includes calcined petroleum coke aggregate with a D50 of 15-20 μm and graphite powder with a D50 of 1-5 μm, and the mass ratio of the calcined petroleum coke aggregate to the graphite powder is (7-9):(1-3).

4. The preparation method according to claim 1, characterized in that, The asphalt is a high-temperature molten asphalt with a softening point of 160-200℃, and the mass ratio of carbonaceous aggregate to asphalt is (7-9):(1-3).

5. The preparation method according to any one of claims 1-4, characterized in that, The process of rolling, crushing, and sieving the paste to obtain pressed powder includes the following steps: rolling the paste into sheets 1-3 times, with a sheet thickness of 1-2 mm, and the rolling temperature corresponding to the pressure kneading temperature. After cooling, the paste is crushed, passed through a 160-325 mesh sieve, and mixed for 0.5-1 h to obtain pressed powder. During cold isostatic pressing, the powder is loaded into the mold sleeve of the isostatic pressing mold, vibrated and then vacuum sealed. It is then placed in a cold isostatic pressing equipment and pressed at 150-200MPa for 5-20 minutes. After the pressure is released, the green block is obtained.

6. The preparation method according to any one of claims 1-4, characterized in that, During pressure calcination, the process is carried out in a closed space at a pressure of 0.1-3 MPa and at 800-1200℃ for 2-4 hours. After cooling, the calcined block is obtained.

7. The preparation method according to any one of claims 1-4, characterized in that, The graphitization process involves treating the material at 2000-3000℃ for 1-2 hours, followed by cooling, to obtain high-purity graphite material.

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