Preparation method of ultra-high thermal conductive short-cut mesophase pitch-based graphite fiber

Abstract

The application discloses a preparation method of super-high thermal conductive short-cut mesophase pitch-based graphite fiber and belongs to the technical field of fiber materials. The mesophase pitch fiber is obtained through twice melt spinning treatment, then the mesophase pitch fiber is cut into fixed-length fibers and subjected to non-fusion treatment, tension is applied to the obtained non-fusion fiber during carbonization treatment, then the non-fusion fiber is cut, and finally, graphitization treatment is performed. The mesophase pitch is used as raw material, twice melt spinning is performed, the fiber with more highly ordered aromatic molecular arrangement can be obtained by not adding a filter screen during the second spinning, the aromatic macromolecule can be converted into more regular carbon layers by applying tension during the carbonization process, the orientation of graphite microcrystals is favorable, and thus the super-high thermal conductive short-cut mesophase pitch-based graphite fiber can be obtained, and the carbonization is followed by short cutting, which is helpful to maintaining the orientation structure of the graphite microcrystals. The thermal conductivity of the short-cut mesophase pitch-based graphite fiber can be up to 1358 W / (m*K).

Description

Technical Field

[0001] This invention relates to the field of fiber materials technology, specifically to a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers. Background Technology

[0002] In fields such as electronics, electrical engineering, and aerospace, the accumulation of heat generated by equipment can lead to an increase in internal temperature, affecting its normal operation. To ensure steady-state operation, the generated heat must be dissipated in a timely manner, thus placing high demands on the thermal conductivity of materials. Graphite materials possess excellent properties such as high thermal conductivity, low coefficient of thermal expansion, low density, high temperature resistance, corrosion resistance, self-lubrication, and good thermal shock resistance, making them one of the most promising heat dissipation materials in recent years. They have extremely broad development prospects in aviation, aerospace, nuclear industry, military industry, and many civilian industrial sectors.

[0003] Mesophase pitch-based graphite fiber (MPCF) is a graphite microcrystalline material with a carbon content of over 90%, composed of sheet-like graphite microcrystals stacked along the fiber axis. It is an important component of carbon fiber and has wide applications in national defense and economic development. Mesophase pitch-based carbon fiber possesses a series of excellent properties, including high specific modulus, high specific strength, good thermal conductivity, corrosion resistance, creep resistance, low coefficient of thermal expansion, high temperature resistance, and electromagnetic shielding. Its most outstanding properties are high modulus and high thermal conductivity; the elastic modulus can reach over 800 GPa, and the thermal conductivity can reach over 800 W / (m·K).

[0004] However, due to the high planarity of mesophase pitch molecules, wedge-shaped split structures are easily formed after infusibility, carbonization, and graphitization, which affects their mechanical properties. Therefore, researchers have modified the final cross-sectional morphology by adding inorganic additives such as graphene, carbon black, boron carbide, and silicon during the spinning process. However, these methods undoubtedly sacrifice some of the thermal conductivity of mesophase pitch-based graphite fibers. Furthermore, current research and technologies on mesophase pitch-based graphite fibers mainly focus on filament preparation and modification of fiber cross-sectional morphology; research and technical solutions for ultra-high thermal conductivity chopped mesophase pitch-based graphite fibers are relatively rare. Moreover, the filament preparation process for mesophase pitch-based graphite fibers suffers from high cost, complex procedures, and high preparation difficulty. To address these issues, this invention proposes a method for preparing ultra-high thermal conductivity chopped mesophase pitch-based graphite fibers. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers. By performing two melt spinning, non-melting, carbonization and graphitization treatments on mesophase pitch, short-cut mesophase pitch-based graphite fibers with ultra-high thermal conductivity are obtained.

[0006] To achieve the above objectives, this invention provides a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, specifically including the following steps:

[0007] (1) After crushing and sieving the mesophase pitch, add it to the melt spinning equipment. Place 1-5 metal filter screens at the feed end of the spinneret. Then heat the melt spinning equipment to above the softening point of the mesophase pitch and keep it at a constant temperature for 5-30 minutes before spinning the mesophase pitch fiber I.

[0008] (2) After crushing the mesophase pitch fiber I by a pulverizer, add it to the melt spinning equipment, heat the melt spinning equipment to above the softening point of the mesophase pitch, keep the temperature constant for 5 to 30 minutes, and then spin the mesophase pitch fiber II.

[0009] (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace for non-melting treatment to obtain a fixed length mesophase pitch-based non-melting fiber.

[0010] (4) Apply a tension of 0.01 to 2 Newtons to the fixed-length mesophase pitch-based infusible fibers and place them in a carbonization furnace for carbonization treatment to obtain fixed-length mesophase pitch-based carbon fibers.

[0011] (5) Cut the fixed-length mesophase pitch-based carbon fiber into short carbon fiber, and then place it in a graphitization furnace for graphitization to obtain ultra-high thermal conductivity short-cut mesophase pitch-based graphite fiber.

[0012] Preferably, the mesophase pitch is one of coal-based mesophase pitch, oil-based mesophase pitch, or naphthalene-based mesophase pitch, and the mesophase pitch has a mesophase content of ≥80%, a softening point of 250-330℃, and an ash content of ≤500ppm.

[0013] Preferably, in step (1), the sieve aperture size is 40-400 mesh; the spinneret aperture diameter is ≤0.25mm and the spinneret length-to-diameter ratio is ≥2:1; the metal filter mesh aperture size is 100-300 mesh; and the take-up rate of the mesophase pitch fiber I is 30-600m / min.

[0014] Preferably, in step (2), the sieve aperture size is 40-400 mesh; the spinneret aperture diameter is ≤0.25mm, and the length-to-diameter ratio of the spinneret aperture is ≥2:1; no filter screen is placed at the feed end, and the winding rate of the mesophase pitch fiber II is 30-600m / min.

[0015] Preferably, in step (3), the non-melting treatment temperature is ±10℃ of the softening point of the mesophase asphalt, the time is 20~240min, and the heating rate is 0.2~2.5℃ / min.

[0016] Preferably, in step (4), the carbonization temperature is 700-1500℃, the carbonization time is 30-180min, and the heating rate is 2-10℃ / min.

[0017] Preferably, the length of the short-cut carbon fiber in step (5) is 0.1 to 30 mm, the graphitization temperature is 2500 to 3200 °C, and the graphitization time is 1 to 60 min.

[0018] Therefore, the present invention employs the above-mentioned method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, and the beneficial effects are as follows:

[0019] (1) The present invention can obtain fibers with a more highly ordered arrangement of aromatic molecules by two melt spinning processes, and the second spinning process without the addition of a filter screen, thereby obtaining mesophase pitch-based graphite fibers.

[0020] (2) Applying tension during carbonization in this invention can cause aromatic macromolecules to evolve into more regular carbon layers, which is beneficial to the uniform orientation of graphite microcrystals, thereby determining the ultra-high thermal conductivity of short-cut mesophase pitch-based graphite fibers. Short-cutting after carbonization helps to maintain the orientation structure of graphite microcrystals.

[0021] (3) The preparation method of the present invention is simple. The non-melting, carbonization and graphitization processes are carried out in stages, which does not require continuous equipment and reduces production costs.

[0022] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0024] This invention provides a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, specifically including the following steps:

[0025] (1) After crushing and sieving the mesophase pitch, add it to the melt spinning equipment. Place 1-5 metal filter screens at the feed end of the spinneret. Then heat the melt spinning equipment to above the softening point of the mesophase pitch and keep it at a constant temperature for 5-30 minutes before spinning the mesophase pitch fiber I.

[0026] (2) After crushing the mesophase pitch fiber I by a pulverizer, add it to the melt spinning equipment, heat the melt spinning equipment to above the softening point of the mesophase pitch, keep the temperature constant for 5 to 30 minutes, and then spin the mesophase pitch fiber II.

[0027] (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace for non-melting treatment to obtain a fixed length mesophase pitch-based non-melting fiber.

[0028] (4) Apply a tension of 0.01 to 2 Newtons to the fixed-length mesophase pitch-based infusible fibers and place them in a carbonization furnace for carbonization treatment to obtain fixed-length mesophase pitch-based carbon fibers.

[0029] (5) Cut the fixed-length mesophase pitch-based carbon fiber into short carbon fiber, and then place it in a graphitization furnace for graphitization to obtain ultra-high thermal conductivity short-cut mesophase pitch-based graphite fiber.

[0030] The mesophase pitch is one of coal-based mesophase pitch, oil-based mesophase pitch, or naphthalene-based mesophase pitch, with a mesophase content ≥80%, a softening point of 250–330℃, and an ash content ≤500ppm. The sieve aperture is 40–400 mesh; the spinneret orifice diameter is ≤0.25mm, and the length-to-diameter ratio is ≥2:1; the metal filter screen aperture is 100–300 mesh; and the fiber take-up rate of the mesophase pitch fibers I / II is 30–600m / min.

[0031] The non-melting treatment temperature is ±10℃ from the softening point of the mesophase pitch, the time is 20–240 min, and the heating rate is 0.2–2.5℃ / min; the carbonization temperature is 700–1500℃, the carbonization time is 30–180 min, and the heating rate is 2–10℃ / min; the length of the short-cut carbon fiber is 0.1–30 mm, the graphitization temperature is 2500–3200℃, and the graphitization time is 1–60 min.

[0032] Example 1

[0033] This embodiment provides a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, specifically including the following steps:

[0034] (1) Naphthalene-based mesophase pitch with a mesophase content of 100% and a softening point of 280℃ is crushed, passed through a 200-mesh sieve, and added to a melt spinning device. Two 300-mesh metal filters are placed at the feed end of a spinneret with a spinneret orifice diameter of 0.2 mm and an aspect ratio of 3:1. The spinneret is then heated to 330℃ and held for 20 min before spinning to obtain mesophase pitch fiber I with a take-up rate of 300 m / min.

[0035] (2) After crushing the mesophase pitch fiber I, it was added to the melt spinning equipment. This time, no filter screen was placed at the feed end of the spinneret. The spinneret orifice diameter was 0.12 mm and the length-to-diameter ratio of the spinneret orifice was 6:1. Then it was heated to 335℃ and kept at a constant temperature for 10 min to obtain mesophase pitch fiber II. The take-up rate was 150 m / min.

[0036] (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace and subjected to non-melting treatment at a temperature of 275℃ to obtain a fixed length mesophase pitch-based non-melting fiber. The non-melting time is 120 min and the heating rate is set to 1℃ / min.

[0037] (4) Apply a tension of 1 Newton to the fixed-length mesophase pitch-based non-melting fiber and place it in a carbonization furnace. Carbonize it at a carbonization temperature of 1200℃ to obtain fixed-length mesophase pitch-based carbon fiber. The carbonization time is 60 min and the heating rate is 5℃ / min.

[0038] (5) Cut the fixed-length mesophase pitch-based carbon fiber into 10mm short carbon fibers, and then place them in a graphitization furnace at 3000℃ for 30min to obtain short-cut mesophase pitch-based graphite fibers.

[0039] The short-cut mesophase pitch-based graphite fibers prepared by the above process have a wedge-shaped split cross-sectional structure and a thermal conductivity as high as 1358 W / (m·K), which is significantly higher than the index data of mesophase pitch-based graphite fiber filaments and short-cut fibers currently sold on the market. This indicates that the technical solution has obtained ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, giving full play to the high thermal conductivity functional characteristics of mesophase pitch-based graphite fibers.

[0040] Example 2

[0041] This embodiment provides a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, specifically including the following steps:

[0042] (1) Coal-based mesophase pitch with a mesophase content of 100% and a softening point of 290℃ is crushed, passed through a 200-mesh sieve, and added to a melt spinning device. Two 300-mesh metal filters are placed at the feed end of a spinneret with a spinneret orifice diameter of 0.2 mm and an aspect ratio of 6:1. The spinneret is then heated to 340℃ and held for 20 min before spinning to obtain mesophase pitch fiber I with a take-up rate of 150 m / min.

[0043] (2) After crushing the mesophase pitch fiber I, it was added to the melt spinning equipment. This time, no filter screen was placed at the feed end of the spinneret. The spinneret orifice diameter was 0.12 mm and the length-to-diameter ratio of the spinneret orifice was 6:1. Then it was heated to 345℃ and kept at a constant temperature for 10 min to obtain mesophase pitch fiber II. The take-up rate was 100 m / min.

[0044] (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace and subjected to non-melting treatment at a temperature of 285℃ to obtain a fixed length mesophase pitch-based non-melting fiber. The non-melting time is 60 min and the heating rate is set to 0.5℃ / min.

[0045] (4) Apply a tension of 0.5 Newtons to the fixed-length mesophase pitch-based infusible fiber and place it in a carbonization furnace. Carbonize it at a carbonization temperature of 1300℃ to obtain fixed-length mesophase pitch-based carbon fiber. The carbonization time is 60 min and the heating rate is 5℃ / min.

[0046] (5) Cut the fixed-length mesophase pitch-based carbon fiber into 10mm short carbon fibers, and then place them in a graphitization furnace at 3000℃ for 30min to obtain short-cut mesophase pitch-based graphite fibers.

[0047] The short-cut mesophase pitch-based graphite fibers prepared by the above process have a wedge-shaped split cross-sectional structure and a thermal conductivity as high as 1274 W / (m·K), which is significantly higher than the index data of mesophase pitch-based graphite fiber filaments and short-cut fibers currently sold on the market. This indicates that the technical solution has obtained ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, giving full play to the high thermal conductivity functional characteristics of mesophase pitch-based graphite fibers.

[0048] Example 3

[0049] This embodiment provides a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, specifically including the following steps:

[0050] (1) Petroleum-based mesophase pitch with a mesophase content of 100% and a softening point of 285℃ is crushed, passed through a 300-mesh sieve, and added to a melt spinning equipment. A 300-mesh metal filter is placed at the feed end of a spinneret with a spinneret orifice diameter of 0.25mm and an aspect ratio of 6:1. Then, it is heated to 335℃ and kept at that temperature for 20 minutes before spinning to obtain mesophase pitch fiber I with a take-up rate of 400m / min.

[0051] (2) After crushing the mesophase pitch fiber I, it was added to the melt spinning equipment. This time, no filter screen was placed at the feed end of the spinneret. The spinneret orifice diameter was 0.15 mm and the length-to-diameter ratio of the spinneret orifice was 6:1. Then it was heated to 340℃ and kept at a constant temperature for 10 min to obtain mesophase pitch fiber II. The take-up rate was 150 m / min.

[0052] (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace and subjected to non-melting treatment at a temperature of 282℃ to obtain a fixed length mesophase pitch-based non-melting fiber. The non-melting time is 120 min and the heating rate is set to 1℃ / min.

[0053] (4) Apply a tension of 0.5 Newtons to the fixed-length mesophase pitch-based infusible fiber and place it in a carbonization furnace. Carbonize it at a carbonization temperature of 1200℃ to obtain fixed-length mesophase pitch-based carbon fiber. The carbonization time is 60 min and the heating rate is 3℃ / min.

[0054] (5) Cut the fixed-length mesophase pitch-based carbon fiber into 20mm short carbon fibers, and then place them in a graphitization furnace at 2800℃ for 30min to obtain short-cut mesophase pitch-based graphite fibers.

[0055] The short-cut mesophase pitch-based graphite fibers prepared by the above process have a wedge-shaped split cross-sectional structure and a thermal conductivity as high as 1207 W / (m·K), which is significantly higher than the index data of mesophase pitch-based graphite fiber filaments and short-cut fibers currently sold on the market. This indicates that the technical solution has obtained ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, giving full play to the high thermal conductivity functional characteristics of mesophase pitch-based graphite fibers.

[0056] Example 4

[0057] This embodiment provides a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, specifically including the following steps:

[0058] (1) Petroleum-based mesophase pitch with a mesophase content of 100% and a softening point of 285℃ is crushed, passed through a 300-mesh sieve, and added to a melt spinning equipment. Three 300-mesh metal filters are placed at the feed end of a spinneret with a spinneret orifice diameter of 0.15mm and an aspect ratio of 3:1. The spinneret is then heated to 335℃ and kept at that temperature for 20 minutes before spinning to obtain mesophase pitch fiber I with a take-up rate of 300m / min.

[0059] (2) After crushing the mesophase pitch fiber I, it was added to the melt spinning equipment. This time, no filter screen was placed at the feed end of the spinneret. The spinneret orifice diameter was 0.1 mm and the length-to-diameter ratio of the spinneret orifice was 6:1. Then it was heated to 340℃ and kept at a constant temperature for 10 min to obtain mesophase pitch fiber II. The take-up rate was 150 m / min.

[0060] (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace and subjected to non-melting treatment at a temperature of 282℃ to obtain a fixed length mesophase pitch-based non-melting fiber. The non-melting time is 120 min and the heating rate is set to 1℃ / min.

[0061] (4) Apply a tension of 0.5 Newtons to the fixed-length mesophase pitch-based infusible fiber and place it in a carbonization furnace. Carbonize it at a carbonization temperature of 1200℃ to obtain fixed-length mesophase pitch-based carbon fiber. The carbonization time is 60 min and the heating rate is 3℃ / min.

[0062] (5) Cut the fixed-length mesophase pitch-based carbon fiber into 20mm short carbon fibers, and then place them in a graphitization furnace at 2800℃ for 30min to obtain short-cut mesophase pitch-based graphite fibers.

[0063] The short-cut mesophase pitch-based graphite fibers prepared by the above process have a wedge-shaped split cross-sectional structure and a thermal conductivity as high as 1319 W / (m·K), which is significantly higher than the index data of mesophase pitch-based graphite fiber filaments and short-cut fibers currently sold on the market. This indicates that the technical solution has obtained ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, giving full play to the high thermal conductivity functional characteristics of mesophase pitch-based graphite fibers.

[0064] Example 5

[0065] This embodiment provides a method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, specifically including the following steps:

[0066] (1) Coal-based mesophase pitch with a mesophase content of 100% and a softening point of 300℃ is crushed, passed through a 200-mesh sieve, and added to a melt spinning equipment. Two 300-mesh metal filters are placed at the feed end of a spinneret with a spinneret orifice diameter of 0.15mm and an aspect ratio of 3:1. The spinneret is then heated to 345℃ and kept at that temperature for 20 minutes before spinning to obtain mesophase pitch fiber I with a take-up rate of 150m / min.

[0067] (2) After crushing the mesophase pitch fiber I, it was added to the melt spinning equipment. This time, no filter screen was placed at the feed end of the spinneret. The spinneret orifice diameter was 0.1 mm and the length-to-diameter ratio of the spinneret orifice was 6:1. Then it was heated to 350℃ and kept at a constant temperature for 10 min to obtain mesophase pitch fiber II. The take-up rate was 100 m / min.

[0068] (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace and subjected to non-melting treatment at a temperature of 295℃ to obtain a fixed length mesophase pitch-based non-melting fiber. The non-melting time is 60 min and the heating rate is set to 0.5℃ / min.

[0069] (4) Apply a tension of 0.5 Newtons to the fixed-length mesophase pitch-based infusible fiber and place it in a carbonization furnace. Carbonize it at a carbonization temperature of 1200℃ to obtain fixed-length mesophase pitch-based carbon fiber. The carbonization time is 60 min and the heating rate is 5℃ / min.

[0070] (5) Cut the fixed-length mesophase pitch-based carbon fiber into 5mm short carbon fibers, and then place them in a graphitization furnace at 2800℃ for 30min to obtain short-cut mesophase pitch-based graphite fibers.

[0071] The short-cut mesophase pitch-based graphite fibers prepared by the above process have a wedge-shaped split cross-sectional structure and a thermal conductivity as high as 1321 W / (m·K), which is significantly higher than the index data of mesophase pitch-based graphite fiber filaments and short-cut fibers currently sold on the market. This indicates that the technical solution has obtained ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, giving full play to the high thermal conductivity functional characteristics of mesophase pitch-based graphite fibers.

[0072] This invention employs the aforementioned method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers. Through two melt spinning processes, mesophase pitch-based graphite fibers with ordered aromatic molecules are obtained. During the carbonization process, tension is applied to transform the aromatic macromolecules into more regular carbon layers, which is beneficial to the orientation of graphite microcrystals and thus determines the ultra-high thermal conductivity of the short-cut mesophase pitch-based graphite fibers. The preparation method of this invention is simple, with the melting, carbonization, and graphitization processes carried out in stages, eliminating the need for continuous equipment. When used as a thermally conductive additive, the fiber cross-sectional morphology does not need to be considered, reducing production costs.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers, characterized in that: Specifically, the following steps are included: (1) After crushing and sieving the mesophase pitch, add it to the melt spinning equipment. Place 1-5 metal filter screens at the feed end of the spinneret. Then heat the melt spinning equipment to above the softening point of the mesophase pitch and keep it at a constant temperature for 5-30 minutes before spinning the mesophase pitch fiber I. (2) After crushing the mesophase pitch fiber I by a pulverizer, it is added back into the melt spinning equipment. No filter screen is placed at the feed end. The melt spinning equipment is heated to above the softening point of the mesophase pitch and kept at a constant temperature for 5~30 minutes before spinning the mesophase pitch fiber II. (3) The mesophase pitch fiber II on the take-up roller is cut along the roller axis to obtain a fixed length fiber, and then it is placed in an oxidation furnace for non-melting treatment to obtain a fixed length mesophase pitch-based non-melting fiber. (4) Apply a tension of 0.01~2 Newtons to the fixed-length mesophase pitch-based infusible fibers and place them in a carbonization furnace for carbonization treatment to obtain fixed-length mesophase pitch-based carbon fibers; (5) Cut the fixed-length mesophase pitch-based carbon fiber into short carbon fiber, and then place it in a graphitization furnace for graphitization to obtain ultra-high thermal conductivity short-cut mesophase pitch-based graphite fiber.

2. The method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers according to claim 1, characterized in that: The mesophase pitch is one of coal-based mesophase pitch, oil-based mesophase pitch, or naphthalene-based mesophase pitch. The mesophase pitch has a mesophase content of ≥80%, a softening point of 250~330℃, and an ash content of ≤500ppm.

3. The method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers according to claim 1, characterized in that: In step (1), the sieve aperture size is 40~400 mesh; the spinneret aperture diameter is ≤0.25mm and the spinneret length-to-diameter ratio is ≥2:1; the metal filter mesh aperture size is 100~300 mesh; and the take-up rate of the mesophase pitch fiber I is 30~600m / min.

4. The method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers according to claim 1, characterized in that: In step (2), the spinneret has a spinneret orifice diameter ≤ 0.25 mm and a spinneret orifice length-to-diameter ratio ≥ 2:1; the mesophase pitch fiber II has a take-up rate of 30~600 m / min.

5. The method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers according to claim 1, characterized in that: In step (3), the non-melting treatment temperature is ±10℃ of the softening point of the mesophase asphalt, the time is 20~240min, and the heating rate is 0.2~2.5℃ / min.

6. The method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers according to claim 1, characterized in that: In step (4), the carbonization temperature is 700~1500℃, the carbonization time is 30~180min, and the heating rate is 2~10℃ / min.

7. The method for preparing ultra-high thermal conductivity short-cut mesophase pitch-based graphite fibers according to claim 1, characterized in that: The length of the short-cut carbon fiber in step (5) is 0.1~30mm, the graphitization temperature is 2500~3200℃, and the graphitization time is 1~60min.