PAN-based carbon fiber reinforced high-thermal-conductivity C / C composite material and preparation method thereof

Abstract

The invention relates to the technical field of composite materials, and discloses a preparation method of a PAN-based carbon fiber reinforced high-thermal-conductivity C / C composite material, which comprises the following steps: laying multiple layers of PAN-based carbon fiber cloth in a mold along the same direction, and uniformly spreading mesophase pitch powder on each layer of fiber cloth to obtain a C / C composite material preform; and carrying out hot press molding on the C / C composite material preform by using a hot press, and then carrying out carbonization and graphitization treatment to obtain the one-dimensional low-density C / C composite material. Sequentially carrying out liquid-phase impregnation, carbonization treatment and graphitization treatment on the one-dimensional low-density C / C composite material to obtain the PAN-based carbon fiber reinforced high-thermal-conductivity C / C composite material, and repeating the steps of liquid phase impregnation, carbonization and graphitization for multiple times until the PAN-based carbon fiber reinforced high-thermal-conductivity C / C composite material with the target density is obtained. The bending strength of the high-thermal-conductivity C / C composite material is 202-360 MPa, the unidirectional thermal conductivity reaches 445-525 (W / m.K), and low-cost preparation of high-heat component structural materials suitable for aerospace and the like is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material and a preparation method thereof. Background Art

[0002] The demand for high-performance carbon-carbon composite materials in the fields of aerospace, automobiles and energy is increasing, and the materials need to have high strength, thermal shock resistance, high temperature resistance and other characteristics. High thermal conductivity C / C composite materials have good chemical stability, low thermal expansion coefficient, high strength and low density, and have stable thermal physical properties. They can still maintain good thermal conductivity and mechanical properties in high temperature environments. They have broad application prospects in aerospace, brake systems, nuclear energy and new energy, high-temperature industrial equipment, biomedicine, military and ultra-high-speed equipment and other fields.

[0003] High thermal conductivity C / C composite materials are mainly composed of reinforcement and matrix. Common reinforcements include mesophase pitch-based carbon fiber and polyacrylonitrile (PAN)-based carbon fiber. PAN-based carbon fiber has excellent mechanical properties, but its thermal conductivity is relatively low (axial thermal conductivity: 5-175W / (m·K)). Although the thermal conductivity of mesophase pitch-based carbon fiber reaches 600W / (m·K), its production process is complicated and the price is high. Common matrix carbons include resin carbon, pyrolytic carbon and asphalt carbon. Pyrolytic carbon is usually obtained by chemical vapor infiltration (CVI) process, and its textures include high texture, medium texture, low texture and isotropic structure. Among them, high-texture pyrolytic carbon has high orientation order, is easy to graphitize, and has good thermal conductivity, but the process is extremely difficult to control; resin carbon and asphalt carbon are generally obtained by liquid precursor impregnation-carbonization (PIP) process. Resin carbon generally has an isotropic structure and is difficult to graphitize. Asphalt carbon is generally obtained by pressurized impregnation carbonization of medium-temperature asphalt or mesophase asphalt, but the residual carbon rate of mesophase asphalt is significantly higher than that of medium-temperature asphalt. The obtained asphalt carbon has a higher graphite crystallite orientation along the carbon fiber surface, which is beneficial to improving the thermal conductivity of the material.

[0004] Therefore, it is necessary to propose a method for preparing low-cost and high thermal conductivity C / C composite materials using PAN as a reinforcement and mesophase pitch carbon as a matrix carbon. Summary of the invention

[0005] Based on the above, the object of the present invention is to provide a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material and a preparation method thereof, which has low cost and excellent thermal conductivity.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material comprises the following steps:

[0008] Laying out multiple layers of PAN-based carbon fiber cloth in the same direction in a mold, and evenly spreading mesophase pitch powder on each layer of the fiber cloth to obtain a C / C composite preform;

[0009] The C / C composite material preform is hot-pressed by a hot press, and then carbonized and graphitized to obtain a one-dimensional low-density C / C composite material;

[0010] The one-dimensional low-density C / C composite material is sequentially subjected to liquid phase impregnation, carbonization treatment and graphitization treatment to obtain a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material;

[0011] The liquid phase impregnation-carbonization-graphitization steps are repeated multiple times until a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material with a target density is obtained.

[0012] As a preferred solution for the preparation of a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, mesophase asphalt powder with a mesh size of 200 or more is evenly spread on each layer of fiber cloth.

[0013] As a preferred solution for the preparation method of a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, during the hot pressing process, when the temperature rises to the molding temperature of 300-350°C, the molding pressure is increased to 3-4MPa, maintained for 3-4min, and then released to 0-0.1MPa for 3-4min, and the pressurization and release steps are repeated multiple times.

[0014] As a preferred solution for the preparation method of a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, in the process of obtaining the one-dimensional low-density C / C composite material, the carbonization temperature is 350-600°C and the graphitization temperature is 2900-3000°C.

[0015] As a preferred solution for the preparation method of a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, liquid phase impregnation is performed, the one-dimensional low-density C / C composite material is placed in an impregnation box, and is embedded with mesophase asphalt powder, and then placed in a high-pressure reactor and replaced with inert gas. After the temperature is raised to a predetermined temperature, the vacuum is maintained for a period of time, and then an inert gas is introduced to maintain a certain pressure for liquid phase impregnation treatment.

[0016] As a preferred solution for the preparation method of a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, the predetermined temperature is 340-380°C, the certain pressure maintained by the introduction of inert gas is 3-6 MPa, and the liquid phase impregnation treatment time is 3-4 hours.

[0017] As a preferred solution for the preparation method of a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, after the liquid phase impregnation treatment, the carbonization temperature is 350-600°C and the graphitization temperature is 2900-3000°C.

[0018] As a preferred embodiment of a method for preparing a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, during the repeated liquid phase impregnation-carbonization-graphitization process, the density of the C / C composite material is less than 1.4 g / cm 3 When the density of the composite material is higher than 1.4g / cm 3 When the temperature is increased, the heating rate in the carbonization temperature range of 350-600℃ can reach 0.8~1℃ / min.

[0019] A PAN-based carbon fiber reinforced high thermal conductivity C / C composite material is prepared by any of the above-mentioned preparation methods.

[0020] The beneficial effects of the present invention are:

[0021] The present invention provides a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material and a preparation method thereof. The PAN-based material is used as a reinforcement and the mesophase asphalt carbon is used as a matrix carbon. The cost is low. The mesophase asphalt is fully impregnated with the carbon fiber by hot pressing and the mesophase asphalt is fully oriented in the composite material. After hot pressing, the carbonization-graphitization treatment is performed to open the pores so as to improve the impregnation efficiency of the C / C composite material. Liquid phase impregnation, carbonization, and graphitization densification treatment are then repeated to obtain a high thermal conductivity C / C composite material with a target density. The high thermal conductivity C / C composite material has a bending modulus of 202-360 Mpa and a thermal conductivity of 445-525 W·m -1 ·k -1 The high thermal conductivity C / C composite material prepared by this process can reach a density of 1.8-1.9 g / cm 3 And above, the fiber volume percentage can reach 50% to 65%. In addition, since PAN-based carbon fiber is a common civilian carbon fiber, it is cheaper than mesophase asphalt-based carbon fiber, which can save reaction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0023] Figure 1is a microscopic morphology of a high thermal conductivity C / C composite material provided by an embodiment of the present invention;

[0024] Figure 2 is a polarization diagram of a high thermal conductivity C / C composite material provided by an embodiment of the present invention;

[0025] Figure 3 is an XRD diagram of a cross-sectional direction of a high thermal conductivity C / C composite material provided by an embodiment of the present invention;

[0026] Figure 4 This is an XRD diagram of the plane direction of the high thermal conductivity C / C composite material provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] For ease of understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Unless otherwise defined, all technical and scientific terms used in the present invention belong to the technical field of the present invention.

[0028] Example 1

[0029] This embodiment provides a method for preparing a one-dimensional high thermal conductivity C / C composite material, which comprises the following steps:

[0030] Cut one-dimensional T700 PAN cloth, sieve asphalt powder on the PAN base cloth with a 100-mesh screen, repeat the laying steps until all the fibers are placed in the mold, and close the mold;

[0031] The asphalt-impregnated one-dimensional carbon fiber preform is placed in a mold and hot-pressed by a hot press; the temperature is raised from room temperature to 340-350°C at 2-3°C / min, and the temperature is kept at 30 minutes, and the pressure is increased by 0.1-0.3 MPa, and then the temperature is raised to 355-370°C at 1-2°C / min, and the pressure is increased by 3-4 MPa, and the pressure is kept for 3 minutes, and the pressure is released by 0-0.1 MPa for 3 minutes, and the pressure increase and pressure release steps are repeated 4-6 times, and the pressure is increased to 3-4 MPa again, and the temperature is raised to 375-390°C at 1-2°C / min, and the temperature is kept for 180 minutes, and the temperature is raised to 420-450°C at 0.3-0.5°C / min, and the temperature is kept for 240 minutes, and the temperature is cooled to room temperature;

[0032] Carbonization-graphitization step: subjecting the hot-pressed one-dimensional C / C composite material preform to carbonization-graphitization treatment to obtain a low-density one-dimensional C / C composite material;

[0033] Repeating liquid phase impregnation densification-carbonization 8 to 9 times, and then graphitizing, to obtain the one-dimensional high thermal conductivity C / C composite material, and finally obtaining a composite material density of 1.91g / cm3, and a composite material fiber volume percentage of 55%;

[0034] The carbonization heating program is: when the density of the composite material is lower than 1.4g·cm-3, the carbonization program is to heat up to 340-350℃ at 3-4℃ / min, keep warm for 1200-1300min, heat up to 500-550℃ at 0.01-0.02℃ / min, heat up to 700-800℃ at 0.1-0.15℃ / min, heat up to 800-850℃ at 0.34-0.4℃ / min, heat up to 1000-1020℃ at 0.5-0.6℃ / min, and keep warm for 60-80min. When the density of the composite material is higher than 1.4 g·cm-3, the carbonization procedure is to heat up to 340-350°C at 3-4°C / min, heat up to 450-500°C at 0.8-1°C / min, keep warm for 120-130min, heat up to 750-800°C at 1-1.1°C / min, heat up to 1000-1020°C at 3-4°C / min, and keep warm for 60-80min.

[0035] Example 2

[0036] This embodiment provides a method for preparing a one-dimensional high thermal conductivity C / C composite material, which comprises the following steps:

[0037] Cut one-dimensional T700 PAN cloth, sieve asphalt powder on the PAN base cloth with a 100-mesh screen, repeat the laying steps until all the fibers are placed in the mold, and close the mold;

[0038] The asphalt-impregnated one-dimensional carbon fiber preform is placed in a mold and hot-pressed by a hot press; the hot-pressing heating procedure is: heating from room temperature to 340-350°C at 2-3°C / min, keeping warm for 30 minutes, pressurizing by 0.1-0.3 MPa, then heating to 355-370°C at 1-2°C / min, pressurizing by 3-4 MPa, keeping warm for 3 minutes, releasing pressure by 0-0.1 MPa, and continuing for 3 minutes, cyclically pressing and releasing pressure steps for 4-6 times, pressurizing to 3-4 MPa again, heating to 375-390°C at 1-2°C / min, keeping warm for 180 minutes, heating to 420-450°C at 0.3-0.5°C / min, keeping warm for 240 minutes, and cooling to room temperature;

[0039] Carbonization-graphitization step: subjecting the hot-pressed one-dimensional C / C composite material preform to carbonization-graphitization treatment to obtain a low-density one-dimensional C / C composite material;

[0040] Repeating liquid phase impregnation densification-carbonization 8 to 9 times, and then graphitizing, to obtain the claimed one-dimensional high thermal conductivity C / C composite material, and finally obtaining a composite material density of 1.91g / cm3, and a composite material fiber volume percentage of 60%;

[0041] The carbonization heating program is: when the density of the composite material is lower than 1.4g·cm-3, the carbonization program is to heat up to 340-350℃ at 3-4℃ / min, keep warm for 1200-1300min, heat up to 500-550℃ at 0.01-0.02℃ / min, heat up to 700-800℃ at 0.1-0.15℃ / min, heat up to 800-850℃ at 0.34-0.4℃ / min, heat up to 1000-1020℃ at 0.5-0.6℃ / min, and keep warm for 60-80min. When the density of the composite material is higher than 1.4 g·cm-3, the carbonization procedure is to heat up to 340-350°C at 3-4°C / min, heat up to 450-500°C at 0.8-1°C / min, keep warm for 120-130min, heat up to 750-800°C at 1-1.1°C / min, heat up to 1000-1020°C at 3-4°C / min, and keep warm for 60-80min.

[0042] Example 3

[0043] This embodiment provides a method for preparing a one-dimensional high thermal conductivity C / C composite material, which comprises the following steps:

[0044] Cut one-dimensional T700 PAN cloth, sieve asphalt powder on the PAN base cloth with a 100-mesh screen, repeat the laying steps until all the fibers are placed in the mold, and close the mold;

[0045] The asphalt-impregnated one-dimensional carbon fiber preform is placed in a mold and hot-pressed by a hot press; the hot-pressing heating program is as follows: the hot-pressing heating program is as follows: the temperature is increased from room temperature to 340-350°C at 2-3°C / min, and the temperature is kept at 30 minutes, and the pressure is increased by 0.1-0.3 MPa, and then the temperature is increased to 355-370°C at 1-2°C / min, and the pressure is increased by 3-4 MPa, and the pressure is kept at 3 minutes, and the pressure is released by 0-0.1 MPa, and the pressure is continued for 3 minutes, and the pressure increase and pressure release steps are repeated 4-6 times, and the pressure is increased to 3-4 MPa again, and the temperature is increased to 375-390°C at 1-2°C / min, and the temperature is kept at 180 minutes, and the temperature is increased to 420-450°C at 0.3-0.5°C / min, and the temperature is kept at 240 minutes, and the temperature is cooled to room temperature;

[0046] Carbonization-graphitization step: subjecting the hot-pressed one-dimensional C / C composite material preform to carbonization-graphitization treatment to obtain a low-density one-dimensional C / C composite material;

[0047] The one-dimensional high thermal conductivity C / C composite material was obtained by repeating liquid phase impregnation densification-carbonization 8 to 9 times and then graphitizing. The final composite material density was 1.91 g / cm3 and the volume percentage of composite fiber was 65%.

[0048] The carbonization heating program is: when the density of the composite material is lower than 1.4g·cm-3, the carbonization program is to heat up to 340-350℃ at 3-4℃ / min, keep warm for 1200-1300min, heat up to 500-550℃ at 0.01-0.02℃ / min, heat up to 700-800℃ at 0.1-0.15℃ / min, heat up to 800-850℃ at 0.34-0.4℃ / min, heat up to 1000-1020℃ at 0.5-0.6℃ / min, and keep warm for 60-80min. When the density of the composite material is higher than 1.4 g·cm-3, the carbonization procedure is to heat up to 340-350°C at 3-4°C / min, heat up to 450-500°C at 0.8-1°C / min, keep warm for 120-130min, heat up to 750-800°C at 1-1.1°C / min, heat up to 1000-1020°C at 3-4°C / min, and keep warm for 60-80min.

[0049] The properties of the high thermal conductivity C / C composite materials prepared in Examples 1-3 are characterized below.

[0050] Figure 1 This is an electron microscope picture of the composite material, showing the structural morphology of the composite material. Figure 2 It is the polarization image of the composite material, showing the optical morphology of the composite material. Figure 3 is the XRD diagram of the composite material in the cross-section direction, indicating the growth of the composite material crystallites. Figure 4 It is the XRD diagram of the composite material in the plane direction, indicating the axial orientation and crystallite growth of the composite material.

[0051] Table 1 Bending strength of Examples 1-3

[0052]

[0053] Table 2 Density and energy conduction performance of Examples 1-3

[0054]

[0055] Table 3 Growth chart of graphite microcrystals of high thermal conductivity C / C composite materials prepared in Examples 1-3

[0056]

[0057] From Tables 1-3, it can be seen that the high thermal conductivity C / C composite material prepared in the present application has excellent thermal conductivity and high bending strength, which meets the application requirements of structural materials for high-heat components in aerospace and other fields, and at the same time has low cost.

[0058] The above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material, characterized in that: The following steps are involved: Laying out multiple layers of PAN-based carbon fiber cloth in the same direction in a mold, and evenly spreading mesophase pitch powder on each layer of the fiber cloth to obtain a C / C composite material preform; The C / C composite material preform is hot-pressed by a hot press, and then carbonized and graphitized to obtain a one-dimensional low-density C / C composite material; The one-dimensional low-density C / C composite material is sequentially subjected to liquid phase impregnation, carbonization treatment and graphitization treatment to obtain a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material; The liquid phase impregnation-carbonization-graphitization steps are repeated multiple times until a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material with a target density is obtained.

2. The method for preparing the PAN-based carbon fiber reinforced high thermal conductivity C / C composite material according to claim 1, characterized in that: Mesophase asphalt powder with a mesh size of 200 or more is evenly spread on each layer of fiber cloth.

3. The method for preparing the PAN-based carbon fiber reinforced high thermal conductivity C / C composite material according to claim 1, characterized in that: During the hot pressing process, when the temperature rises to the molding temperature of 300-350°C, the molding pressure is increased to 3-4MPa, maintained for 3-4min, and then released to 0-0.1MPa for 3-4min, and the pressure is repeated for multiple times.

4. The method for preparing the PAN-based carbon fiber reinforced high thermal conductivity C / C composite material according to claim 1, characterized in that: In the process of obtaining the one-dimensional low-density C / C composite material, the carbonization temperature is 350-600°C and the graphitization temperature is 2900-3000°C.

5. The method for preparing the PAN-based carbon fiber reinforced high thermal conductivity C / C composite material according to claim 1, characterized in that: Liquid phase impregnation is carried out, the one-dimensional low-density C / C composite material is placed in an impregnation box, and is embedded with mesophase asphalt powder, and then placed in a high-pressure reactor and replaced with inert gas. After heating to a predetermined temperature, vacuum is maintained for a period of time, and then inert gas is introduced to maintain a certain pressure for liquid phase impregnation treatment.

6. The method for preparing the PAN-based carbon fiber reinforced high thermal conductivity C / C composite material according to claim 5, characterized in that: The predetermined temperature is 340-380° C., the pressure maintained by introducing inert gas is 3-6 MPa, and the liquid phase immersion treatment time is 3-4 hours.

7. The method for preparing the PAN-based carbon fiber reinforced high thermal conductivity C / C composite material according to claim 1, characterized in that: After the liquid phase impregnation treatment, the carbonization temperature is 350-600°C and the graphitization temperature is 2900-3000°C.

8. The method for preparing a PAN-based carbon fiber reinforced high thermal conductivity C / C composite material according to claim 1, characterized in that: During the repeated liquid phase impregnation-carbonization-graphitization process, the density of the C / C composite material is less than 1.4 g / cm 3 When the density of the composite material is higher than 1.4g / cm 3 When the temperature is increased, the heating rate in the carbonization temperature range of 350-600℃ can reach 0.8~1℃ / min.

9. A PAN-based carbon fiber reinforced high thermal conductivity C / C composite material prepared by the preparation method according to any one of claims 1 to 8.

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