Asphalt-based C / C composite material as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a pitch-based C / C composite material with high uniformity, and the preparation method comprises the following steps: weaving carbon fibers into a preform, and carrying out graphitization treatment; carrying out oxygen plasma treatment on the prefabricated body subjected to graphitization treatment to obtain a modified graphitized prefabricated body; and embedding the modified graphitized preform into isotropic asphalt powder, carrying out vacuum impregnation under a microwave heating condition, then carrying out an in-situ polymerization reaction in an alternating magnetic field, and finally, respectively carrying out carbonization and graphitization under the protection of inert gas to obtain the asphalt-based C / C composite material with high uniformity. The range of the multi-point Raman ID / IG value of the carbon matrix in the asphalt-based C / C composite material prepared by the method is less than or equal to 0.1.

Description

Technical Field

[0001] The present invention relates to the field of integrated manufacturing of C / C composite structures with functions in aerospace and high-temperature thermal fields, and particularly relates to a C / C composite material with a highly uniform pitch carbon matrix, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, C / C composite materials have been developing towards larger sizes, and the requirement for the overall uniformity of the materials has been continuously increasing. Especially in more functional application fields such as high thermal conductivity and high-temperature thermal fields, it is necessary to maintain the consistency of each region to improve the stability of the composite material. Currently, the carbon matrix of C / C composite materials is usually pyrolytic carbon, resin carbon, and pitch carbon deposited by gas phase. Among them, pitch is a preferred precursor for preparing a uniform carbon matrix because it can undergo a certain degree of mesophase transformation during the carbonization process. However, due to the difficulty in controlling the mesophase transformation process of molten pitch inside the preform and the fact that mesophase pitch is prone to clogging the preform due to its high quinoline insoluble content, both lead to the non-uniformity of the finally formed pitch carbon matrix. Therefore, there is an urgent need to develop a new method that can control the uniformity of pitch inside the preform and the consistency of pitch mesophase transformation. Summary of the Invention

[0003] The first object of the present invention is to provide a preparation method of a pitch-based C / C composite material with high uniformity to meet the current demand for the overall uniformity of C / C composite materials.

[0004] The second object of the present invention is to provide a pitch-based C / C composite material prepared by the above method.

[0005] The third object of the present invention is to provide an application of the pitch-based C / C composite material.

[0006] The present invention is achieved through the following technical solutions:

[0007] A preparation method of a pitch-based C / C composite material includes the following steps:

[0008] (1) Perform first graphitization on a three-dimensional preform woven from continuous carbon fiber tows to obtain a graphitized preform;

[0009] (2) Perform oxygen plasma treatment on the graphitized preform to hydroxylate the surface of the graphitized preform to obtain a modified graphitized preform;

[0010] (3) Perform vacuum impregnation on the modified graphitized preform with isotropic pitch to obtain a first intermediate;

[0011] (4) Heat the first intermediate with an alternating magnetic field to create a temperature difference between the modified graphitized preform and the isotropic pitch, causing the isotropic pitch near the modified graphitized preform to first undergo a polymerization reaction and transform into mesophase pitch. In the alternating magnetic field, a temperature difference is formed between the mesophase pitch and the isotropic pitch, and the isotropic pitch near the mesophase pitch undergoes a polymerization reaction to form new mesophase pitch. Thus, the boundary of the mesophase pitch continuously advances outward, and finally all the isotropic pitch is transformed into mesophase pitch, obtaining the second intermediate;

[0012] (5) Carbonize and secondarily graphitize the second intermediate under the protection of an inert gas to obtain the asphalt-based C / C composite material.

[0013] The continuous carbon fiber includes one or two of polyacrylonitrile carbon fiber and pitch carbon fiber;

[0014] The volume fraction of the continuous carbon fiber in the preform is 25%-55%.

[0015] The temperature of the first graphitization is 2600-3000 °C.

[0016] The purity of the oxygen used in the oxygen plasma treatment is ≥99%;

[0017] The gas flow rate of the oxygen used in the oxygen plasma treatment is 20-60 sccm;

[0018] The content of C-C and C=C bonds in the groups of carbon atoms on the surface of the modified graphitized preform is 70-95%.

[0019] The vacuum degree of the vacuum impregnation is 0-100 Pa;

[0020] The temperature of the vacuum impregnation is 150-200 °C;

[0021] The heating method used in the vacuum impregnation is microwave heating;

[0022] The frequency of the microwave used in the microwave heating is 0.5-3 GHz;

[0023] The power of the microwave heating is 300-500 W;

[0024] The time of the microwave heating is 1-2 h.

[0025] The isotropic pitch is petroleum-based pitch;

[0026] The softening point of the petroleum-based pitch is 80-120 °C;

[0027] The content of S element in the petroleum-based asphalt is ≤0.3%, the content of N element is ≤0.4%, the ash content is ≤300 ppm, the toluene-soluble matter is ≥93%, and the content of quinoline-insoluble matter is ≤0.1%.

[0028] The power of the alternating magnetic field is 3 - 5 kw;

[0029] The in-situ polymerization reaction is carried out at 400 - 420 °C;

[0030] The time for the in-situ polymerization reaction to proceed is 4 - 10 h.

[0031] The temperature of the carbonization treatment is 900 - 1000 °C, and the heating rate is 1 - 5 °C / min;

[0032] The temperature of the second graphitization is 2900 - 3000 °C.

[0033] The pitch-based C / C composite material prepared by the preparation method of the pitch-based C / C composite material described above.

[0034] The application of the pitch-based C / C composite material described above is applied to thermal management materials; or applied to thermal management systems.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The method provided by the present invention subjects the preform to graphitization treatment, which improves the thermal conductivity and electrical conductivity of the carbon fibers in the preform, enabling the carbon fibers to preferentially heat up during induction heating, forming a temperature gradient between the carbon fibers and the pitch, and causing the pitch to undergo in-situ polymerization reaction starting from the outer wall of the carbon fibers, improving the stability and uniformity of the growth of the mesophase carbon matrix. The oxygen plasma treatment forms oxygen-containing groups on the surface of the carbon fibers, which can serve as active sites for pitch nucleation. At the same time, this activation method mainly generates C-OH groups on the fiber surface, causing less damage to the structure and thermal conductivity of the graphitized fibers themselves. In addition, compared with other activation schemes that mainly rely on destroying the carbon ring structure to form C=O, C-OH has a stronger polarity and a stronger attraction to pitch molecules. In the Raman spectrum results of the C / C composite material prepared by the method described in the present invention, the range of the I D / I G value between different positions is less than 0.1. The I D / I G value represents the degree of structural disorder of the carbon material, and the smaller the range, the better the uniformity of the carbon material. Specific Embodiments

[0037] The present invention provides a method for preparing a pitch-based C / C composite material with high uniformity, including the following steps:

[0038] (1) Weave continuous carbon fiber tows into a three-dimensional preform and perform the first graphitization treatment.

[0039] (2) Perform oxygen plasma treatment on the preform after graphitization treatment to obtain a modified graphitized preform.

[0040] (3) Embed the modified graphitized preform in isotropic pitch powder and perform vacuum impregnation to obtain a first intermediate.

[0041] (4) Perform in-situ polymerization reaction on the first intermediate in an alternating magnetic field to obtain a second intermediate.

[0042] (5) Subject the second intermediate to carbonization and the second graphitization treatment under the protection of inert gas to obtain the C / C composite material with a highly uniform pitch carbon matrix.

[0043] In the preparation process of existing pitch-based C / C composite materials, such as the technical solution disclosed in CN118459230A, due to the lack of precise control of the mesophase transformation process, different forms of mesophase transformation occur simultaneously on the surface of carbon fibers and in the pitch mother liquor. These two types of pitch carbon have structural differences, resulting in an uneven structure of the final carbon matrix. Therefore, the present invention uses an alternating magnetic field to perform electromagnetic induction heating on the modified graphitized preform after vacuum impregnation to improve the problem of uneven carbon matrix structure. Specifically, since the carbon fiber preform is graphitized, the electrical and thermal conductivity of the carbon fibers are improved. When using an induction coil to heat the mixture, the graphitized carbon fibers with higher electrical conductivity can reach a higher temperature, forming a temperature difference between the carbon fibers and the pitch, causing the pitch near the surface of the carbon fibers to preferentially undergo polymerization transformation. At the same time, due to the increase in the content of C-OH groups on the surface of the carbon fibers by oxygen plasma treatment, the aggregation efficiency and nucleation rate of the pitch on the surface of the carbon fibers are increased.

[0044] The pitch undergoes polymerization transformation to form a mesophase layer on the surface of the carbon fibers. The mesophase pitch molecules have higher order and larger graphite crystallite size compared to isotropic pitch, enabling them to have better thermal conductivity. Furthermore, a temperature difference is formed between the mesophase pitch and the isotropic pitch in the alternating magnetic field, causing the pitch to further generate new mesophase from the boundary of the existing mesophase pitch and continuously advance outward until they meet to form a complete mesophase pitch. During this process, due to the higher temperature and faster reaction rate, the pitch is more inclined to undergo heterogeneous nucleation on the surface of the carbon fibers, and almost no homogeneous nucleation reaction occurs in the mother liquor. Therefore, through the in-situ mesophase growth method based on induction heating in the present invention, a pitch carbon matrix with strong consistency can be stably prepared, thereby obtaining the preparation of a C / C composite material with a highly uniform carbon matrix.

[0045] Specifically, the carbon fiber in the carbon fiber preform in step (1) can be one or both of polyacrylonitrile carbon fiber and pitch carbon fiber that are easy to graphitize; it can also be other graphitizable carbon fibers. The volume fraction of the carbon fiber in the preform is 25%-55%. If the volume fraction is too low, the gap between the fibers will be large, making it difficult to achieve complete in-situ transformation. If the volume fraction is too high, it will affect the overall performance of the C / C composite material; the graphitization temperature is 2600-3000 °C.

[0046] Specifically, in step (2), the process gas for oxygen plasma treatment is oxygen with a purity ≥99%, the gas flow rate is 20-60 sccm, the vacuum degree is 20-100 Pa, the power is 100-300 W, and the treatment time is 1-3 min. Plasma treatment mainly performs oxidative grafting at the edge of the carbon ring to generate strongly polar C-OH groups, which have a stronger attraction to asphalt molecules. The content of C-C and C=C bonds in the carbon atom-containing groups of the carbon atoms on the surface of the modified graphitized preform is 70-95%, ensuring the stability of the carbon fiber structure and macroscopic physical properties. At the same time, this method needs to control the number of surface functional groups. The content of C-C and C=C bonds is characterized by the surface XPS C1s spectrum.

[0047] Specifically, when performing vacuum impregnation, it is preferred to use microwave for heating. In the impregnation stage using microwave heating, the movement of asphalt molecules is accelerated under the action of microwave, the viscosity is reduced, and it is easier to penetrate into the preform. At the same time, because microwave heating can act on all molecules, the overall heating of asphalt can be more uniform. During the impregnation process under microwave heating conditions, since microwave synchronously heats the whole asphalt powder, and at the same time the movement of asphalt molecules is accelerated under the action of microwave, finally the distribution of the impregnated asphalt is more uniform. Using the conventional heating method may generate temperature gradient and concentration gradient during the impregnation process, resulting in uneven distribution of asphalt in the preform.

[0048] Specifically, when using microwave for vacuum impregnation, the microwave frequency of the vacuum impregnation is 0.5-3 GHz, preferably 2.45 GHz, the heating power is maintained at 300-500 W. Too high heating power will cause the destruction of asphalt molecules and affect their physical and chemical properties, and too low will be difficult to achieve the above effects. The vacuum degree is 0-100 Pa, the temperature is 150-200 °C, and the heat preservation time is 1-2 h. The vacuum degree of the vacuum impregnation is 0-100 Pa, and the temperature is 150-200 °C.

[0049] Specifically, the isotropic pitch in step (4) is preferably petroleum-based pitch, with a softening point of 80-120°C, S element content ≤ 0.3%, N element content ≤ 0.4%, ash content ≤ 300 ppm, toluene-soluble matter ≥ 93%, and quinoline-insoluble matter content ≤ 0.1%; ash and quinoline-insoluble matter will become nucleation sites during the transformation of the pitch mesophase, and excessive introduction will affect the consistency of in-situ transformation; too many heteroelements such as S and N will result in poor thermal conductivity of the final carbon matrix.

[0050] Specifically, the alternating magnetic field in step (4) can be generated by an induction electric heating device. The induction electric heating device is a low-frequency induction heating furnace or an intermediate-frequency induction heating furnace; in an alternating magnetic field with a power of 3-5 kw, the first intermediate is heated to 400-420°C and held for 4-10 h, so that the first intermediate undergoes an in-situ polymerization reaction and is transformed into a second intermediate.

[0051] Specifically, the temperature of the carbonization treatment in step (5) is 900-1000°C, and the heating rate is 1-5°C / min; the high-temperature graphitization temperature is 2900-3000°C.

[0052] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] Example 1

[0054] Continuous pitch-based carbon fibers are woven into a preform with a volume fraction of 55% and subjected to graphitization treatment at 2800°C to obtain a graphitized preform.

[0055] The graphitized preform is subjected to oxygen plasma treatment to obtain a modified graphitized preform. The treatment conditions for oxygen plasma treatment are a power of 300 W, an air flow rate of 30 sccm, and a vacuum degree of 40 Pa.

[0056] The modified graphitized preform is embedded in petroleum-based pitch with a softening point of 85-95°C, ash content ≤ 150 ppm, and quinoline-insoluble matter ≤ 0.1%. Then, the modified graphitized preform and petroleum-based pitch are heated to 190°C using 500 W of microwave, and the modified graphitized preform is subjected to vacuum impregnation at 1.9 MPa to obtain a first intermediate.

[0057] The first intermediate is heated to 405°C and held for 8 h under an alternating magnetic field of 5 kw to obtain a second intermediate.

[0058] The second intermediate is carbonized at 1000 °C (heating rate: 2 °C / min) and graphitized at 3000 °C to obtain a pitch-based C / C composite material with high uniformity.

[0059] Example 2

[0060] A preform is woven from polyacrylonitrile carbon fiber with a volume fraction of 40%, and graphitized at 2600 °C to obtain a graphitized preform.

[0061] The graphitized preform is treated with oxygen plasma to obtain a modified graphitized preform. The treatment conditions for oxygen plasma treatment are a power of 200 W, a gas flow rate of 20 sccm, and a vacuum degree of 20 Pa.

[0062] The modified graphitized preform is embedded in an oil-based pitch with a softening point of 90 - 100 °C, an ash content of ≤200 ppm, and a quinoline insoluble content of ≤0.1%. Then, the modified graphitized preform and the petroleum-based pitch are heated to 180 °C by 400 W of microwave and vacuum impregnated under 1.3 MPa to obtain a first intermediate.

[0063] The first intermediate is heated to 420 °C under an alternating magnetic field of 3 kw and held for 4 h to obtain a second intermediate.

[0064] The second intermediate is carbonized at 900 °C (heating rate: 5 °C / min) and graphitized at 2800 °C to obtain a pitch-based C / C composite material with high uniformity.

[0065] Comparative Example 1

[0066] A preform is woven from polyacrylonitrile carbon fiber with a volume fraction of 55% without graphitization and modification.

[0067] The preform is embedded in an oil-based pitch with a softening point of 100 - 110 °C, an ash content of ≤150 ppm, and a quinoline insoluble content of ≤0.1%. Then, the modified graphitized preform and the petroleum-based pitch are heated to 190 °C by 500 W of microwave and vacuum impregnated under 1.9 MPa.

[0068] The first intermediate is heated to 405 °C under an alternating magnetic field of 5 kw and held for 4 h to obtain an intermediate.

[0069] The intermediate is carbonized at 1000 °C (heating rate: 2 °C / min) and graphitized at 3000 °C to obtain a C / C composite material. For the C / C composite materials prepared in Example 1, Example 2, and Comparative Example 1, Raman spectroscopy is performed on 5 carbon matrix positions with a distance of more than 5 mm from each other, and the I D / I G values and ranges are calculated, and the results are shown in Table 1.

[0070] Table 1 for each sample I D / I G values and ranges

[0071]

[0072] Table 1 shows that the C / C composite material prepared by the method of the present invention has a lower I D / I G range of values, indicating that the carbon matrix of this material has better uniformity.

[0073] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an asphalt-based C / C composite material, characterized in that: The steps include: (1) performing a first graphitization on a three-dimensional preform woven from continuous carbon fiber bundles to obtain a graphitized preform; (2) treating the graphitized preform with oxygen plasma to hydroxylate the surface of the graphitized preform to obtain a modified graphitized preform; (3) vacuum impregnating the modified graphitized preform with isotropic asphalt to obtain a first intermediate; (4) heating the first intermediate by using an alternating magnetic field to generate a temperature difference between the modified graphitized preform and the isotropic asphalt, so that the isotropic asphalt near the modified graphitized preform undergoes a polymerization reaction first and is converted into an intermediate phase asphalt. In the alternating magnetic field, a temperature difference is formed between the intermediate phase asphalt and the isotropic asphalt, and the isotropic asphalt near the intermediate phase asphalt undergoes a polymerization reaction to form a new intermediate phase asphalt, so that the boundary of the intermediate phase asphalt is continuously pushed outward, and finally the isotropic asphalt is completely converted into the intermediate phase asphalt, thereby obtaining a second intermediate; (5) Carrying out a carbonization and a second graphitization on the second intermediate under the protection of an inert gas to obtain the asphalt-based C / C composite material.

2. The method for preparing the asphalt-based C / C composite material according to claim 1, characterized in that: The continuous carbon fiber includes one or both of polyacrylonitrile carbon fiber and pitch carbon fiber; The volume fraction of the continuous carbon fibers in the preform is 25%-55%.

3. The method for preparing the asphalt-based C / C composite material according to claim 1, characterized in that: The temperature of the first graphitization is 2600-3000°C.

4. The method for preparing the asphalt-based C / C composite material according to claim 1, characterized in that: The purity of oxygen used in the oxygen plasma treatment is ≥99%; The oxygen gas flow rate used in the oxygen plasma treatment is 20-60 sccm; The content of CC and C=C bonds in the groups of carbon atoms on the surface of the modified graphitized preform is 70-95%.

5. The method for preparing the asphalt-based C / C composite material according to claim 1, characterized in that: The vacuum degree of the vacuum impregnation is 0-100 Pa; The vacuum impregnation temperature is 150-200°C; The heating method adopted by the vacuum impregnation is microwave heating; The microwave frequency used in the microwave heating is 0.5-3 GHz; The power of the microwave heating is 300-500W; The microwave heating time is 1-2h.

6. The method for preparing the asphalt-based C / C composite material according to claim 1, characterized in that: The isotropic asphalt is petroleum-based asphalt; The petroleum-based asphalt has a softening point of 80-120°C; The petroleum-based asphalt has an S element content of ≤0.3%, an N element content of ≤0.4%, an ash content of ≤300ppm, a toluene soluble matter of ≥93%, and a quinoline insoluble matter content of ≤0.1%.

7. The method for preparing the asphalt-based C / C composite material according to claim 1, characterized in that: The power of the alternating magnetic field is 3-5kw; The in-situ polymerization reaction is carried out at 400-420° C.; The in-situ polymerization reaction is carried out for 4-10 hours.

8. The method for preparing the asphalt-based C / C composite material according to claim 1, characterized in that: The temperature of the carbonization treatment is 900-1000°C, and the heating rate is 1-5°C / min; The temperature of the second graphitization is 2900-3000°C.

9. The asphalt-based C / C composite material prepared by the method for preparing an asphalt-based C / C composite material according to any one of claims 1 to 8.

10. The use of the asphalt-based C / C composite material according to claim 9, characterized in that: Applied in thermal management materials.

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