A carbon-carbon composite material and a method for producing the same

Abstract

The application provides a carbon-carbon composite material and a preparation method thereof, which comprises the following steps: (1) mixing a matrix material and aggregate at a mass ratio of (5-60):(40-95) to obtain carbon-carbon composite particles; (2) shearing the carbon-carbon composite particles at a shearing linear velocity of 20-100 m / s to obtain a precursor, and carbonizing and delayed coking the precursor under a closed hot-pressing condition; and (3) re-carbonizing the material obtained in the step (2) to obtain a carbon-carbon composite material; wherein the matrix material in the step (1) is selected from pitch, and the aggregate is selected from graphite and carbon fiber. The carbon-carbon composite material provided by the application has higher density and more excellent heat-conducting and electric-conducting properties.

Description

Technical Field

[0001] This invention belongs to the technical field of carbon composite materials, and particularly relates to a carbon-carbon composite material and its preparation method. Background Technology

[0002] Currently, carbon-based composite materials are widely used in many fields due to their excellent properties. For example, compared with metallic materials, carbon-based composite materials have lower density, higher thermal conductivity, and lower coefficient of thermal expansion, and can replace metals as heat dissipation materials in fields such as computers, communication equipment, integrated circuits, and electronic packaging. They also possess characteristics such as high electronic conductivity, large lithium-ion diffusion coefficient, small volume change before and after lithium intercalation in a layered structure, high lithium intercalation capacity, and low lithium intercalation potential, making them suitable as anode materials for lithium-ion batteries. Furthermore, carbon-based composite materials, due to their excellent mechanical strength, can be used to manufacture mechanical parts such as molds and pressure heads.

[0003] However, the traditional preparation methods currently used to repeatedly mix aggregates and binders in kneaders, mills, and impregnation machines, which makes the process very complicated, has many defects, and results in a poor yield.

[0004] Patent CN 106241775A discloses a graphite material, its raw material composition, its preparation method, and its uses. Specifically, it uses natural graphite, artificial graphite, mesophase carbon microspheres, and a binder, which are mixed through methods such as kneading, extrusion, crushing, and sieving, and then pressed into a green body for carbonization to obtain the graphite material. This method has a cumbersome process in preparing the mixture, and the additives are not adequately treated during the preparation process. The additives have large particle sizes, and although the kneading process is used, it only achieves the dispersion of large particles.

[0005] Patent CN 101708838A discloses a natural flake graphite-based highly oriented graphite material and its preparation method. This method involves mixing natural graphite and a binder (different types of pitch and resin) in a solvent, then drying and hot-pressing the mixture, finally carbonizing it to obtain a high thermal conductivity carbon material. However, this method cannot control the graphite layer, and the mixing uniformity is poor, failing to achieve the nanoscale level.

[0006] Patent CN 105705606A describes a carbon composite material, its preparation method, and its uses. It involves mechanically mixing expanded graphite with at least one of a filler or reinforcement to form a composite, which is then compressed under isostatic pressure to obtain the carbon-carbon composite material, used in sealing elements, etc. However, because the size and lamellar thickness of the expanded graphite are not specified, this material cannot effectively control the particle size and lamellar thickness of the graphite. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention provides a carbon-carbon composite material and a method for preparing the same.

[0008] To achieve the objectives of this invention, the following technical solution is adopted:

[0009] The present invention provides a method for preparing a carbon-carbon composite material in a first aspect, comprising:

[0010] (1) The matrix material and aggregate are initially mixed in a mass ratio of (5-60):(40-95) to obtain carbon-carbon composite particles;

[0011] (2) The carbon-carbon composite particles are sheared at a shear line velocity of 20 to 100 m / s to obtain a precursor, and the obtained precursor is carbonized and delayed coking under closed hot pressing conditions.

[0012] (3) The material obtained after step (2) is subjected to recarbonization treatment to obtain carbon-carbon composite material;

[0013] In step (1), the matrix material is selected from asphalt, and the aggregate is selected from graphite and carbon fiber.

[0014] In some specific embodiments of the preparation method of the present invention, the softening point of the asphalt used in step (1) is 60-360℃, preferably 80-320℃, for example, 100℃, 200℃; in some preferred embodiments, the particle size of the asphalt is 50-300μm, for example, 100-250μm, 150-200μm; specifically, the asphalt used can be pulverized to the above particle size range before preparation.

[0015] In some specific embodiments, the asphalt is selected from one or more of coal tar pitch, petroleum asphalt, mesophase asphalt, or oxidized asphalt.

[0016] In some specific embodiments, the particle size of the aggregate in step (1) is 0.1–50 μm, preferably 2–40 μm. Specifically, the carbon fiber is selected from one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, or vapor-grown carbon fiber; the graphite is selected from one or more of natural graphite, graphene, natural microcrystalline graphite, or expanded graphite.

[0017] In a specific embodiment of step (2) of the preparation method of the present invention, the obtained carbon-carbon composite particles are placed in a kneader, extruder or roller press for shearing treatment. In some preferred embodiments, the shearing treatment is carried out at 80 to 350°C for 30 min to 2 h, for example, 45 min, 1 h, 1.5 h, so that the carbon-carbon composite particles are obtained as nanoscale dispersed precursors under strong shearing force.

[0018] In the preparation method of this invention, the sheared precursor is directly placed into a mold and carbonized and delayed coking is carried out under hot pressing conditions of 10-50 MPa under inert gas protection. In some specific embodiments, the carbonization conditions are: heating to 300-450°C at a heating rate of 1-10°C / min and holding at that temperature for 0.5-6 hours, which reduces the formation of pores in the material during carbonization and increases the density of the material. In some preferred embodiments, heating to 350-450°C at a heating rate of 1-8°C / min and holding at that temperature for 0.5-4 hours.

[0019] In some specific embodiments of the present invention, the delayed coking treatment conditions in step (2) are as follows: heating to 480-600°C at a heating rate of 1-16°C / min, holding at the temperature for 0.5-10 hours and then cooling to room temperature; preferably, heating to 480-550°C at a heating rate of 1-12°C / min, holding at the temperature for 1-8 hours and then cooling to room temperature.

[0020] In some specific embodiments of the present invention, the recarbonization conditions in step (3) can be: heating to 1000-1600°C at a heating rate of 1-16°C / min, holding at that temperature for 0.5-10 hours, and then cooling to room temperature. Recarbonization reduces the content of organic components and other elements in the composite material, increases the crystallinity of the carbon material, and is beneficial for improving the compressive strength, flexural strength, and thermal conductivity of the material. In some preferred embodiments, heating to 1100-1500°C at a heating rate of 3-12°C / min, holding at that temperature for 1-8 hours, and then cooling to room temperature.

[0021] In a second aspect, the present invention provides a carbon-carbon composite material prepared by the above-described preparation method.

[0022] The dispersion coefficient δ of the Id / Ig ratio Id / Ig of the carbon-carbon composite material, measured by Raman spectroscopy, is ≤0.2, and further 0.05 to 0.2; the composite material prepared by the present invention has high uniformity and few internal defects.

[0023] The ratio k of the peak area of ​​the (002) plane of the graphite crystalline phase to the peak area of ​​the amorphous carbon, as measured by XRD, is 0.2 to 0.8, preferably 0.3 to 0.6;

[0024] The true density of the carbon-carbon composite material is 1.8–2.3 g / cm³. 3The thermal conductivity is 250–600 W / m·K, preferably 250–310 W / m·K, for example, 260 W / m·K, 270 W / m·K, 300 W / m·K; the compressive strength is 50–100 MPa, preferably 60–80 MPa, for example, 65 MPa, 70 MPa, 75 MPa; the flexural strength is 30–80 MPa, preferably 40–70 MPa, for example, 50 MPa, 55 MPa, 60 MPa.

[0025] The above technical solution achieves the following technical effects:

[0026] The preparation method of the present invention achieves nanoscale dispersion of matrix materials and aggregates by shearing at a specific linear velocity and carbonizing and delayed coking under closed hot pressing, thereby obtaining carbon-carbon composite materials with higher density and better thermal and electrical conductivity. At the same time, the preparation method of the present invention can control the ratio of amorphous structure to ordered structure in the composite material, thereby controlling the mechanical properties of the composite material. Detailed Implementation

[0027] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0029] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0030] The evaluation methods used in the various examples of this invention are as follows:

[0031] 1. Discrete coefficient δ:

[0032] (1) The composite carbon material powder sample to be tested is spread in the sample cell, and 20 different random locations in the sample are tested to obtain the corresponding Raman spectrum Id and Ig values.

[0033] (2) Calculate the ratios of Id to Ig, μ1, μ2, ..., μg, respectively. n , and according to μ=(μ1+μ2+……+μ n ) / n calculate the average value μ;

[0034] (3) Calculate the standard deviation σ using the following formula:

[0035] σ=sqrt{[(μ1–μ) 2 +(μ2–μ) 2 +……+(μ n –μ) 2 ] / n};

[0036] Where n = 20, and sqrt is the square root.

[0037] (4) Calculate the dispersion coefficients δ of these Id / Ig using the following formula:

[0038] δ = σ / μ.

[0039] 2. Peak area k value: The ratio of the peak area of ​​the (002) plane of the graphite crystalline phase to the peak area of ​​the amorphous carbon phase as measured by XRD.

[0040] 3. Thermal conductivity: The thermal conductivity of the material was measured using a NETZSCH Group LFA467 HyperFlash thermal conductivity meter according to the method of ASTM E1461-2011.

[0041] 4. Compressive strength: GB / T13465.3-2014;

[0042] 5. Flexural strength: GB / T 13465.2-2014.

[0043] Example 1

[0044] (1) Coal tar pitch (softening point of 150℃) was pulverized to 150μm and used as matrix material; it was then preliminarily mixed with polyacrylonitrile-based carbon fiber aggregate at a mass ratio of 10:50 to obtain carbon-carbon composite particles.

[0045] (2) The obtained carbon-carbon composite particles were placed in a kneader and sheared at 160℃ and 30m / s linear velocity for 60min to obtain a precursor. The precursor was then placed in a mold and heated to 420℃ at a heating rate of 2℃ / min under inert gas protection and closed hot pressing at 10MPa. The temperature was held for 1h, and then heated to 500℃ at a heating rate of 3℃ / min. The temperature was held for 2h and then cooled to room temperature.

[0046] (3) The material obtained after step (2) is subjected to recarbonization under nitrogen conditions. Specifically, the temperature is increased to 1200℃ at a heating rate of 5℃ / min, and then kept at the temperature for 5 hours before being cooled to room temperature to obtain carbon-carbon composite material.

[0047] Example 2

[0048] (1) Petroleum asphalt (softening point of 200℃) was pulverized to 120μm and used as matrix material; it was initially mixed with natural graphite aggregate at a mass ratio of 10:40 to obtain carbon-carbon composite particles.

[0049] (2) The carbon-carbon composite particles were placed in a ball mill and sheared at 160°C at a linear velocity of 50 m / s for 2 hours to obtain a precursor. The precursor was then placed in a mold and heated to 400°C at a heating rate of 1°C / min under inert gas protection and closed hot pressing at 15 MPa. The temperature was held for 3 hours and then heated to 550°C at a heating rate of 2°C / min. The temperature was held for 5 hours and then cooled to room temperature.

[0050] (3) The material obtained after step (2) is subjected to recarbonization under nitrogen conditions. Specifically, the temperature is increased to 1500℃ at a heating rate of 3℃ / min, and then kept at the temperature for 3 hours before being cooled to room temperature to obtain carbon-carbon composite material.

[0051] Example 3

[0052] (1) Coal tar pitch (softening point is 180℃) was pulverized to 80μm and used as matrix material; it was initially mixed with pitch-based carbon fiber aggregate at a mass ratio of 10:90 to obtain carbon-carbon composite particles.

[0053] (2) The carbon-carbon composite particles were placed in a ball mill and sheared at 200°C at a linear velocity of 100 m / s for 2 hours to obtain a precursor. The precursor was then placed in a mold and heated to 450°C at a heating rate of 5°C / min under inert gas protection and closed hot pressing at 15 MPa. The temperature was held for 2 hours and then heated to 520°C at a heating rate of 8°C / min. The temperature was held for 3 hours and then cooled to room temperature.

[0054] (3) The material obtained after step (2) is subjected to recarbonization under nitrogen conditions. Specifically, the temperature is increased to 1200℃ at a heating rate of 5℃ / min, and then kept at the temperature for 4 hours before being cooled to room temperature to obtain carbon-carbon composite material.

[0055] Example 4

[0056] (1) The mesophase pitch (softening point of 280℃) was pulverized to 60μm and used as the matrix material; it was then mixed with aggregate (polyacrylonitrile-based carbon fiber and natural graphite at a mass ratio of 1:3) at a mass ratio of 10:40 to obtain carbon-carbon composite particles.

[0057] (2) The carbon-carbon composite particles were placed in a kneader and sheared at 300°C at a linear velocity of 80 m / s for 1 h to obtain a precursor. The precursor was then placed in a mold and heated to 380°C at a heating rate of 3°C / min under inert gas protection and closed hot pressing at 30 MPa. The temperature was held for 3 h and then heated to 480°C at a heating rate of 5°C / min. The temperature was held for 5 h and then cooled to room temperature.

[0058] (3) The material obtained after step (2) is subjected to recarbonization under nitrogen conditions. Specifically, the temperature is increased to 1400℃ at a heating rate of 5℃ / min, and then kept at the temperature for 5 hours before being cooled to room temperature to obtain carbon-carbon composite material.

[0059] Example 5

[0060] (1) Petroleum asphalt (softening point of 220℃) was pulverized to 180μm and used as matrix material; it was then preliminarily mixed with aggregate (asphalt-based carbon fiber and graphene mixed at a mass ratio of 5:1) at a mass ratio of 50:50 to obtain carbon-carbon composite particles.

[0061] (2) The carbon-carbon composite particles were placed in a kneader and sheared at 230°C at a linear velocity of 50 m / s for 1 h to obtain a precursor. The precursor was then placed in a mold and heated to 420°C at a heating rate of 10°C / min under inert gas protection and closed hot pressing at 45 MPa. The temperature was held for 2 h and then heated to 600°C at a heating rate of 5°C / min. The temperature was held for 1 h and then cooled to room temperature.

[0062] (3) The material obtained after step (2) is subjected to recarbonization under nitrogen conditions. Specifically, the temperature is increased to 1500℃ at a heating rate of 10℃ / min, and then kept at the temperature for 3 hours before being cooled to room temperature to obtain carbon-carbon composite material.

[0063] Comparative Example 1

[0064] (1) Petroleum asphalt (softening point of 150℃) was pulverized to 180μm and used as matrix material; it was initially mixed with asphalt-based carbon fiber aggregate at a mass ratio of 10:40 to obtain carbon-carbon composite particles.

[0065] (2) The carbon-carbon composite particles were placed in a kneader and sheared at 230°C and 50 m / s linear velocity for 1 hour to obtain the precursor. The precursor was then placed in a mold and molded under closed hot pressing conditions of 45 MPa.

[0066] (3) The material obtained after step (2) is subjected to recarbonization under nitrogen conditions. Specifically, the temperature is increased to 1500℃ at a heating rate of 10℃ / min, and then kept at the temperature for 3 hours before being cooled to room temperature to obtain carbon-carbon composite material.

[0067] Comparative Example 2

[0068] (1) Petroleum asphalt (softening point of 150℃) was pulverized to 180μm and used as matrix material; it was initially mixed with asphalt-based carbon fiber aggregate at a mass ratio of 10:40 to obtain carbon-carbon composite particles.

[0069] (2) The carbon-carbon composite particles were placed in a kneader and sheared at 230°C at a linear velocity of 10 m / s for 1 h to obtain a precursor. The precursor was then placed in a mold and heated to 600°C at a heating rate of 10°C / min under inert gas protection and closed hot pressing at 5 MPa. After holding at the temperature for 3 h, it was cooled to room temperature.

[0070] (3) The material obtained after step (2) is subjected to recarbonization under nitrogen conditions. Specifically, the temperature is increased to 1500℃ at a heating rate of 10℃ / min, and then kept at the temperature for 3 hours before being cooled to room temperature to obtain carbon-carbon composite material.

[0071] The carbon-carbon composite materials obtained above were subjected to performance tests, and the test results are shown in Table 1 below:

[0072] Table 1

[0073]

[0074] Note: In Table 1, "peak area ratio k" refers to the ratio of the peak area of ​​the (002) plane of the graphite crystalline phase to the peak area of ​​the amorphous carbon as measured by XRD; "dispersion coefficient" refers to the ratio of Id to Ig, Id / Ig, as measured by Raman spectroscopy.

Claims

1. A method for preparing a carbon-carbon composite material, characterized in that, The preparation method includes: (1) The matrix material and aggregate are initially mixed in a mass ratio of (5~60):(40~95) to obtain carbon-carbon composite particles; (2) The carbon-carbon composite particles are sheared at a shear line velocity of 20~100 m / s to obtain a precursor, and the obtained precursor is carbonized and delayed coking under closed hot pressing conditions. The shearing process is carried out at 80~350℃; The carbonization conditions are as follows: heating to 300-450℃ at a heating rate of 1-10℃ / min, and holding at that temperature for 0.5-6 h. The conditions for the delayed coking process are as follows: heating to 480-600℃ at a heating rate of 1-16℃ / min, holding at that temperature for 0.5-10 hours, and then cooling to room temperature. (3) The material obtained after step (2) is subjected to recarbonization treatment to obtain carbon-carbon composite material; the recarbonization conditions are: heating to 1000~1600℃ at a heating rate of 1~16℃ / min, holding at the temperature for 0.5~10 h and then cooling to room temperature. In step (1), the matrix material is selected from asphalt, and the softening point of the asphalt is 80~320℃; the aggregate is selected from graphite and carbon fiber.

2. The preparation method according to claim 1, characterized in that, The particle size of the asphalt in step (1) is 50~300μm.

3. The preparation method according to claim 2, characterized in that, The asphalt is selected from one or more of coal tar pitch, petroleum asphalt, mesophase asphalt, or oxidized asphalt.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The aggregate in step (1) has a particle size of 0.1~50 μm; The carbon fiber is selected from one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, or vapor-grown carbon fiber. The graphite is selected from one or more of natural graphite, graphene, natural microcrystalline graphite, or expanded graphite.

5. The preparation method according to claim 4, characterized in that, The aggregate in step (1) has a particle size of 2~40 μm.

6. The preparation method according to any one of claims 1 to 3 and 5, characterized in that, In step (2), the carbon-carbon composite particles are placed in a kneader, extruder, or roller press for shearing.

7. The preparation method according to claim 6, characterized in that, The shearing process lasts from 30 min to 2 h.

8. The preparation method according to any one of claims 1 to 3, 5, and 7, characterized in that, In step (2), the carbonization and delayed coking process is carried out under inert gas protection and hot pressing conditions of 10~50 MPa. The carbonization conditions are as follows: heating to 350-450℃ at a heating rate of 1-8℃ / min, and holding at that temperature for 0.5-4 hours.

9. The preparation method according to claim 8, characterized in that, The conditions for the delayed coking process are as follows: heating to 480-550°C at a heating rate of 1-12°C / min, holding at that temperature for 1-8 hours, and then cooling to room temperature.

10. The preparation method according to claim 9, characterized in that, The recarbonization conditions in step (3) are as follows: heat to 1100-1500℃ at a heating rate of 3-12℃ / min, hold at the temperature for 1-8 h, and then cool to room temperature.

11. A carbon-carbon composite material, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 10.

12. The carbon-carbon composite material according to claim 11, characterized in that, The coefficient of variation δ for the Id / Ig ratio of the carbon-carbon composite material, measured by Raman spectroscopy, is ≤0.

2. The ratio k of the peak area of ​​the (002) plane of the graphite crystalline phase to the peak area of ​​the amorphous carbon, as measured by XRD, is 0.2~0.

8. The true density of the carbon-carbon composite material is 1.8~2.3 g / cm³. 3 It has a thermal conductivity of 250~600 W / m·k, a compressive strength of 50~100 MPa, and a flexural strength of 30~80 MPa.

13. The carbon-carbon composite material according to claim 12, characterized in that, The coefficient of variation δ of the Id / Ig ratio of the carbon-carbon composite material, measured by Raman spectroscopy, is 0.05~0.

2.

14. The carbon-carbon composite material according to claim 12, characterized in that, The ratio k of the peak area of ​​the (002) plane of the graphite crystalline phase to the peak area of ​​the amorphous carbon, as measured by XRD, is 0.3~0.6.

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