Preparation method of high-density and high-strength graphite material

Abstract

The present invention discloses a preparation method of high-density and high-strength graphite material, belonging to the technical field of graphite material preparation. The preparation method of the present invention includes raw material grinding: grinding pitch coke into fine powder; gas-phase adsorption: placing the above-mentioned powder in a closed mixing chamber for stirring and introducing pitch fumes; forming - impregnation: taking out the mixed material and forming it, and placing the formed green body in an impregnation tank for impregnation; roasting - graphitization: sequentially performing roasting and graphitization treatments on the impregnated product, and obtaining the high-density and high-strength graphite material after cooling. The present invention adopts gas-phase adsorption technology to replace the traditional kneading process. Through the penetration of pitch fumes to the surface of fine powder particles, the fine powder particles have certain adhesiveness, avoiding a series of problems caused by excessive pitch usage in traditional kneading, thereby improving the preparation efficiency of the product. In addition, directly impregnating after forming, low-temperature coal tar pitch penetrates into the pores of the green body, playing a role in filling and densifying, so that the density and strength of the product are greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of graphite material preparation, and more specifically, relates to a method for preparing a high-density and high-strength graphite material. Background Art

[0002] High-density and high-strength graphite materials have characteristics such as low specific gravity, high mechanical strength, good electrical and thermal conductivity, high temperature resistance, corrosion resistance, and self-lubrication. They are widely used in the semiconductor industry, photovoltaic industry, electrical discharge machining, metal continuous casting, optical fibers, mold manufacturing, as well as aerospace and nuclear industries. They are key new materials indispensable in strategic emerging industries, and their research and application have very broad prospects.

[0003] The preparation of high-density and high-strength graphite generally uses calcined pitch coke as raw material, which is ground to several microns to dozens of microns, and then mixed with binder pitch by kneading. Then, rolling, grinding, forming, two impregnations and three roastings (or three impregnations and four roastings), and graphitization treatments are carried out in sequence. The whole technological process is very complex, especially the need for repeated impregnation and roasting treatments. This not only increases the production cost of graphite materials, but also it is difficult to guarantee the performance of the materials. There is an urgent need in the industry to find an efficient method for preparing high-strength and high-density graphite.

[0004] After retrieval, an application case with the Chinese patent publication number CN 108863365 A discloses an isostatic pressing graphite preparation method and preparation device. The preparation method includes: crushing acicular petroleum coke, calcining acicular petroleum coke powder, acid-leaching the calcined acicular petroleum coke powder, kneading the purified acicular petroleum coke powder with modified pitch, rolling the acicular petroleum coke powder paste, cooling and crushing the acicular petroleum coke thin sheet, extruding the crushed acicular petroleum coke into a cylindrical rod, crushing and sieving the petroleum coke cylindrical rod, kneading the secondary petroleum coke powder with modified pitch, loading the raw material mixture into a rubber mold, loading the isostatic pressing formed blank into a jacket, roasting to obtain a roasted product, and sealing and immersing the roasted product in an impregnation tank to obtain the isostatic pressing graphite. This method significantly reduces the porosity of the isostatic pressing graphite finished product, making the structure of the isostatic pressing graphite finished product uniform to improve the mechanical strength of the isostatic pressing graphite product. However, in this application case, kneading operation is also required. The pitch added in the kneading operation undergoes pyrolysis and polycondensation reactions during roasting, releasing a large amount of volatile gases, which causes a large number of pores or defects in the green body, affecting the final product performance. Summary of the Invention

[0005] 1. Problems to be Solved

[0006] In view of at least some of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing a high-density and high-strength graphite material. According to the technical solution of the present invention, the gas-phase adsorption technology is used to replace the traditional kneading process. The asphalt fume penetrates through the surface of the fine powder particles by adsorption, so that the fine powder particles have a certain adhesiveness, avoiding a series of problems caused by excessive asphalt dosage in the traditional kneading, and thus improving the preparation efficiency of the product.

[0007] 2. Technical Solution

[0008] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a high-density and high-strength graphite material of the present invention includes the following specific steps:

[0010] S1. Raw material grinding

[0011] Grind the pitch coke into fine powder.

[0012] S2. Gas-phase adsorption

[0013] Place the above-mentioned powder in a closed mixing chamber and stir, and introduce asphalt fume to maintain a certain pressure.

[0014] S3. Molding - Impregnation

[0015] Take out the mixture and perform molding, and place the molded green body in an impregnation tank for impregnation.

[0016] S4. Roasting - Graphitization

[0017] Perform roasting and graphitization treatments on the impregnated product in sequence, and the high-density and high-strength graphite material can be obtained after cooling.

[0018] Further, in the step S1, the pitch coke is calcined pitch coke, the average particle size of the fine powder is 5 - 15 μm, and the morphology of the fine powder is spherical or quasi-spherical structure.

[0019] Further, in the step S2, the asphalt fume is the fume generated by asphalt during the conventional kneading process, and the asphalt fume is compressed before being introduced.

[0020] Further, in the step S2, the pressure in the mixing chamber is maintained at 0 - 1.0 MPa, the mixing time is 30 - 120 min, and after the mixing is completed, it is left standing for more than 60 min.

[0021] Further, in the step S3, the softening point of the impregnating asphalt in the impregnation tank is 65 - 80 °C.

[0022] Further, in the step S3, the forming method is isostatic pressing. Before forming, mechanical vibration compaction and vacuum pumping treatment are carried out. The forming pressure is 150 - 220 MPa, the pressure holding time is 5 - 20 min, and pressure relief is carried out in the later stage after the pressure holding ends.

[0023] Further, in the step S3, vacuum pumping treatment is carried out before impregnation. The impregnation temperature is 130 - 160 °C, the impregnation pressure is 0 - 3.0 MPa, and the impregnation time is 1 - 10 h.

[0024] Further, in the step S4, the highest roasting temperature is 900 °C, the heat preservation time is 10 - 20 h, and the roasting duration is 20 - 50 days.

[0025] Further, in the step S4, the highest graphitization temperature is 2850 °C, the heat preservation time is 6 - 15 h, and the graphitization duration is 15 - 30 days.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) In the preparation method of a high-density and high-strength graphite material of the present invention, during the mixing process, asphalt fume is introduced. The purpose is to ensure that the pitch coke fine powder is in full contact with the asphalt fume and penetrates to the surface of the fine powder particles through adsorption, so that the fine powder particles have a certain adhesiveness, thus meeting the requirements of forming and roasting. This step replaces the traditional kneading process and avoids a series of problems caused by excessive asphalt kneading, such as high porosity of the product, low yield rate, and multiple roasting and leaching treatments due to a large amount of volatile matter escaping. Therefore, the process flow is greatly shortened, and the preparation efficiency of the graphite material is improved.

[0029] (2) In the preparation method of a high-density and high-strength graphite material of the present invention, after forming, direct impregnation is carried out. The low-temperature coal tar pitch penetrates into the pores of the green body, playing a role of filling and densifying; at the same time, the entry of the pitch makes up for the possible lack of adhesiveness caused by gas adsorption, and the density and strength of the product are greatly improved.

[0030] (3) In the preparation method of a high-density and high-strength graphite material of the present invention, the average particle size of the fine powder is 5 - 15 μm, and the morphology of the fine powder is spherical or quasi-spherical; the spherical structure has a high packing density, which is beneficial to improving the product strength; at the same time, the spherical structure has good fluidity, which is beneficial to full contact and adsorption with the asphalt fume. Brief description of the drawings

[0031] Figure 1 It is a process flow schematic diagram of the preparation method of a high-density and high-strength graphite material of the present invention. Detailed implementation manners

[0032] Reference Figure 1As shown in the figure, a preparation method of a high-density and high-strength graphite material of the present invention is as follows:

[0033] A. Raw material grinding: Grind the pitch coke into fine powder.

[0034] B. Gas-phase adsorption: Place the above-mentioned powder in a closed mixing chamber and stir, and introduce pitch fumes.

[0035] C. Molding - impregnation: Take out the mixed material and carry out molding, and place the molded green body in an impregnation tank for impregnation.

[0036] D. Baking - graphitization: Carry out baking and graphitization treatments on the impregnated product in sequence, and the high-density and high-strength graphite material is obtained after cooling.

[0037] Among them,

[0038] In step A, calcined pitch coke is used, and it is ground to an average particle size of 5 - 15 μm. The produced fine powder particles have a spherical-like structure, thereby improving the fluidity and bulk density of the fine powder particles, which is beneficial to the improvement of the properties of the graphite material.

[0039] In step B, the raw material fine powder is placed in a closed mixing chamber and stirred. During the mixing process, a certain amount of compressed pitch fumes are introduced. The pressure in the mixing chamber is maintained at 0 - 1.0 MPa, the mixing time is 30 - 120 min, and after mixing, it is left standing for more than 60 min.

[0040] During the mixing process, introducing a certain amount of compressed pitch fumes aims to ensure that the pitch coke fine powder is in full contact with the pitch fumes and penetrates to the surface of the fine powder particles through adsorption, so that the fine powder particles have a certain adhesiveness, thus meeting the requirements of molding and baking. This step replaces the traditional kneading process and avoids a series of problems caused by excessive pitch kneading, such as high porosity of the product, low yield, and multiple baking and leaching treatments due to a large amount of volatile matter escaping.

[0041] The pitch fumes in step B are the fumes generated by pitch during the conventional kneading process, and need to be compressed to maintain the pressure in the mixing chamber within 0 - 1.0 MPa. This pressure range is beneficial to gas-phase adsorption in the mixing chamber, but the improvement of the adsorption effect by pressure is not obvious, and it may also cause waste of energy.

[0042] In step C, the powder wetted with pitch fumes is molded. Before molding, mechanical vibration compaction and vacuum pumping treatments are carried out. The molding pressure is 150 - 220 MPa, the pressure holding time is 5 - 20 min, and after the pressure holding ends, the pressure is released in stages.

[0043] Subsequently, the molded green body is placed in an impregnation tank for impregnation. The impregnating pitch is low-temperature coal tar pitch with a softening point of 65 - 80 °C. The low-temperature coal tar pitch has good fluidity, which is beneficial to the penetration of the green body.

[0044] Further, vacuum pumping treatment is carried out before impregnation, the impregnation temperature is 130 - 160°C, the impregnation pressure is 0 - 3.0 MPa, and the impregnation time is 1 - 10 h.

[0045] In step C, the purpose of directly impregnating the formed green body is that there are inevitably pores in the formed green body. Through vacuum pumping and pressure application treatment, low-temperature coal tar pitch penetrates into the pores of the green body, playing a role in filling and densifying. At the same time, the entry of the pitch makes up for the possible lack of adhesiveness in the above-mentioned gas-phase adsorption, greatly improving the density and strength of the product.

[0046] In step D, the above-mentioned impregnated product is subjected to roasting and graphitization in sequence. The maximum roasting temperature is 900°C, the heat preservation time is 10 - 20 h, and the roasting duration is 20 - 50 days. After roasting, graphitization is carried out. The maximum graphitization temperature is 2850°C, the heat preservation time is 6 - 15 h, and the graphitization duration is 15 - 30 days.

[0047] The present invention adopts key technologies such as gas-phase adsorption and direct impregnation after forming, greatly shortening the process flow, improving the preparation efficiency of high-density and high-strength graphite materials, and more importantly, improving the performance of graphite materials. The graphite material prepared by the method of the present invention has a flexural strength greater than 38.0 MPa and a bulk density greater than 1.76 g / cm 3 。

[0048] The present invention will be further described below in conjunction with specific embodiments.

[0049] Example 1

[0050] Using calcined pitch coke as the raw material, it is ground into fine powder with an average particle size of 10 μm, and the morphology of the fine powder is spherical or quasi-spherical structure.

[0051] Subsequently, the fine powder is placed in a closed mixing chamber and stirred, while compressed pitch flue gas is introduced, so that the pressure in the mixing chamber is maintained at 0.5 MPa, and the mixing duration is 120 min.

[0052] After mixing, the fine powder adsorbed with pitch flue gas is isostatically pressed into shape. The forming pressure is 180 MPa, the pressure holding time is 10 min, and then the pressure is released in stages.

[0053] Then the formed green body is placed in an impregnation tank for impregnation. Vacuum pumping treatment is carried out before impregnation, the impregnation temperature is 150°C, the impregnation pressure is 2.5 MPa, and the impregnation time is 4 h.

[0054] After impregnation, roasting and graphitization treatments are carried out in sequence according to the curve, and a high-density and high-strength graphite material is obtained after cooling.

[0055] Its measured bulk density is 1.80 g / cm 3 and the flexural strength is 42.5 MPa.

[0056] Example 2

[0057] Using calcined pitch coke as raw material, it is ground into fine powder with an average particle size of 5 μm, and the morphology of the fine powder is spherical or quasi-spherical structure.

[0058] Subsequently, the fine powder is placed in a closed mixing chamber and stirred, while compressed asphalt fume is introduced, so that the pressure in the mixing chamber is maintained at 1.0 MPa, and the mixing time is 30 min.

[0059] After mixing, the fine powder adsorbed with asphalt fume is isostatically pressed into shape, the forming pressure is 220 MPa, the pressure holding time is 20 min, and then the pressure is released in stages.

[0060] Then the formed green body is placed in an impregnation tank for impregnation. Before impregnation, vacuum treatment is carried out. The impregnation temperature is 160 °C, the impregnation pressure is 3.0 MPa, and the impregnation time is 1 h.

[0061] After impregnation, roasting and graphitization treatments are carried out in sequence according to the curve, and the high-density and high-strength graphite material is obtained after cooling. Its volume density is measured to be 1.84 g / cm 3 , and the flexural strength is 47.3 MPa.

[0062] Example 3

[0063] Using calcined pitch coke as raw material, it is ground into fine powder with an average particle size of 15 μm, and the morphology of the fine powder is spherical or quasi-spherical structure.

[0064] Subsequently, the fine powder is placed in a closed mixing chamber and stirred, while compressed asphalt fume is introduced, so that the pressure in the mixing chamber is maintained at 0.7 MPa, and the mixing time is 90 min.

[0065] After mixing, the fine powder adsorbed with asphalt fume is isostatically pressed into shape, the forming pressure is 150 MPa, the pressure holding time is 5 min, and then the pressure is released in stages.

[0066] Then the formed green body is placed in an impregnation tank for impregnation. Before impregnation, vacuum treatment is carried out. The impregnation temperature is 130 °C, the impregnation pressure is 1.0 MPa, and the impregnation time is 10 h.

[0067] After impregnation, roasting and graphitization treatments are carried out in sequence according to the curve, and the high-density and high-strength graphite material is obtained after cooling.

[0068] Its volume density is measured to be 1.78 g / cm 3 , and the flexural strength is 38.7 MPa.

[0069] Comparative Example 1

[0070] The same method as in Example 1 was adopted, but no asphalt fume was introduced during the mixing process, and other processes remained unchanged. The graphite material prepared by this method was tested, and its bulk density was 1.75 g / cm 3 , and the flexural strength was 34.3 MPa. And due to the lack of adhesive substances, the products showed cracks to varying degrees.

[0071] Comparative Example 2

[0072] The same method as in Example 1 was adopted, but after molding, it was directly calcined without impregnation, and other processes remained unchanged. The graphite material prepared by this method was tested, and its bulk density was 1.70 g / cm 3 , and the flexural strength was 26.6 MP.

[0073] The present invention and its implementation manners are schematically described above. The description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments to the technical solution without creative efforts without departing from the purpose of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A preparation method of high-density and high-strength graphite material, characterized in that: It includes the following specific steps, S1. Raw material grinding Grind the pitch coke into fine powder; S2. Gas-phase adsorption Place the above-mentioned fine powder in a closed mixing chamber and stir, and introduce pitch fumes to maintain a certain pressure; S3. Molding - impregnation Take out the mixture and carry out molding, and place the molded green body in an impregnation tank for impregnation; S4. Roasting - graphitization Carry out roasting and graphitization treatments on the impregnated product in sequence, and the high-density and high-strength graphite material can be obtained after cooling; wherein, In step S1, the pitch coke is calcined pitch coke, the average particle size of the fine powder is 5 - 15 μm, and the morphology of the fine powder is spherical or quasi-spherical structure; In step S2, the pitch fumes are the fumes generated by pitch during the conventional kneading process, and the pitch fumes are compressed before being introduced; wherein, the pressure in the mixing chamber is maintained at 0 - 1.0 MPa, the mixing time is 30 - 120 min, and after mixing, it is left standing for more than 60 min; In step S3, the impregnating pitch in the impregnation tank is low-temperature coal tar pitch; vacuum pumping treatment is carried out before impregnation, the impregnation temperature is 130 - 160 °C, the impregnation pressure is 0 - 3.0 MPa, and the impregnation time is 1 - 10 h.

2. A preparation method of high-density and high-strength graphite material according to claim 1, characterized in that: In the step S3 described above, the softening point of the impregnating pitch in the impregnation tank is 65 - 80 °C.

3. A preparation method of high-density and high-strength graphite material according to claim 2, characterized in that: In the step S3 described above, the molding method is isostatic pressing molding, mechanical vibration compaction and vacuum pumping treatment are carried out before molding, the molding pressure is 150 - 220 MPa, the pressure holding time is 5 - 20 min, and stage pressure relief is carried out after the pressure holding ends.

4. A preparation method of high-density and high-strength graphite material according to claim 3, characterized in that: In the step S4 described above, the highest roasting temperature is 900 °C, the heat preservation time is 10 - 20 h, and the roasting time is 20 - 50 days.

5. A preparation method of high-density and high-strength graphite material according to claim 4, characterized in that: In the step S4 described above, the highest graphitization temperature is 2850 °C, the heat preservation time is 6 - 15 h, and the graphitization time is 15 - 30 days.

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