Preparation method of carbon fiber reinforced boron carbide composite material

Abstract

The invention provides a preparation method of a carbon fiber reinforced boron carbide composite material, and belongs to the technical field of boron carbide composites.The preparation method comprises the steps that S1, 88-92 parts by weight of boron carbide powder and 5-7 parts by weight of modified graphene nanosheets are mixed, subjected to wet ball milling treatment, filtered and dried, and primary powder is obtained; the modified graphene nanosheet is prepared by modifying a graphene nanosheet with a silane coupling agent; s2, uniformly mixing the primary powder obtained in the step S1 with 8-10 parts of porous carbon fibers to obtain final powder, and granulating and sieving the final powder by using a binder to obtain mixed granules; and S3, pouring the mixed granules obtained in the S2 into a mold, maintaining the pressure for 5-8 minutes under 280-300 MPa, releasing the pressure, stripping from the mold, keeping the temperature at 2100-2300 DEG C for 1.5-2 hours, carrying out vacuum pressureless sintering, and cooling to room temperature along with a furnace to obtain the carbon fiber reinforced boron carbide composite material. The toughness of the prepared composite material can be enhanced, and meanwhile, the thermal conductivity of the composite material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of boron carbide composites, and particularly relates to a preparation method of carbon fiber reinforced boron carbide composites. Background Art

[0002] Electronic packaging materials refer to matrix materials that are used to carry electronic components and their interconnections, play roles such as mechanical support, sealed environmental protection, and dissipation of heat from electronic components, and have good electrical insulation properties, and are the seals of integrated circuits. With the development of microelectronic packaging technology towards multi-chip modules and surface mount technology, traditional packaging materials can no longer meet the requirements of high-density packaging, and new composite materials must be developed. Electronic packaging materials will develop towards multi-phase composite. In addition, the packaging materials also need to simultaneously meet high toughness and high thermal conductivity to cope with the heat accumulation and mechanical shock problems generated during the high-power operation of electronic devices.

[0003] The existing Chinese invention patent with the publication number of CN111892414A discloses a short carbon fiber reinforced boron carbide composite material and a preparation method thereof. The composite material comprises the following components by volume percentage: 80-99vt.% of boron carbide and 1-20vt.% of short carbon fibers; the preparation method comprises: weighing boron carbide powder and short carbon fibers according to the designed component ratio of the short boron carbide composite material, adding them into a deionized aqueous solution containing polyethylene glycol, mixing evenly, and drying to obtain a mixed powder; then loading the mixed powder into a graphite mold and performing spark plasma sintering to obtain a short carbon fiber reinforced boron carbide composite material. The sample prepared by the present invention has a high density, and while retaining a certain strength, the toughness is also improved to a certain extent.

[0004] However, the random distribution of carbon fibers results in the inability to form a continuous axial heat conduction path in the boron carbide matrix, and the random orientation makes the heat transfer path tortuous, and the thermal conductivity (thermal conductivity) of the composite material needs to be further improved. Summary of the Invention

[0005] To solve the problems in the background art, the present invention provides a preparation method of carbon fiber reinforced boron carbide composites, which can enhance the toughness of the prepared composite material while improving its thermal conductivity (thermal conductivity).

[0006] To achieve the above object, the present invention provides a preparation method of carbon fiber reinforced boron carbide composites, comprising the following steps:

[0007] S1. By weight, mix 88-92 parts of boron carbide powder and 5-7 parts of modified graphene nanosheets, perform wet ball milling treatment, filter, and dry to obtain a preliminary powder; the modified graphene nanosheets are prepared by modifying graphene nanosheets with a silane coupling agent;

[0008] S2. Mix the primary powder obtained in S1 with 8 - 10 parts of porous carbon fiber to obtain the final powder, granulate it with a binder, and sieve it to obtain the mixed granular material;

[0009] S3. Pour the mixed granular material obtained in S2 into a mold, keep the pressure at 280 - 300 MPa for 5 - 8 min, then relieve the pressure and take out the mold. Perform vacuum non-pressure sintering at 2100 - 2300 °C for 1.5 - 2 h, and cool it to room temperature with the furnace, then the carbon fiber reinforced boron carbide composite material is obtained.

[0010] Furthermore, the preparation method of the porous carbon fiber is as follows:

[0011] A1. Mix polyacrylonitrile and itaconic acid, dissolve them in dimethyl sulfoxide, and prepare a spinning solution with a mass fraction of 11 - 13%. Electrospinning is used to prepare a fiber film;

[0012] A2. Immerse the fiber film obtained in A1 into an aqueous solution of diammonium hydrogen phosphate, stir at room temperature, dry it, carbonize it in an inert atmosphere, centrifuge and wash it until neutral, and then dry it to obtain carbon fiber;

[0013] A3. Add the carbon fiber obtained in A2 into a KOH solution, stir, dry it, calcine it in an inert atmosphere, wash it until neutral, and then dry it to obtain the porous carbon fiber.

[0014] Furthermore, in A2, the mass fraction of the aqueous solution of diammonium hydrogen phosphate is 10 - 12%.

[0015] Furthermore, in A2, the carbonization temperature is 700 - 800, and the carbonization time is 2 - 2.5 h; in A3, the calcination includes two stages. The first stage is to keep the temperature at 400 ± 10 °C for 1 - 1.2 h, and the second stage is to keep the temperature at 800 ± 10 °C for 2 - 2.2 h.

[0016] Furthermore, in A3, the concentration of the KOH solution is 20 - 25 mg / mL.

[0017] Furthermore, the silane coupling agent includes γ-mercaptopropyltrimethoxysilane and / or 3-aminopropyltriethoxysilane.

[0018] Furthermore, in S1, in the wet ball milling treatment, ethanol is used as the wet milling solvent, and the mass of the wet milling solvent is 2 - 2.5 times the total mass of the boron carbide powder and the modified graphene nanosheets; zirconia balls / tungsten carbide balls are used as the wet milling balls, and the mass of the wet milling balls is 5 - 8 times the total mass of the boron carbide powder and the modified graphene nanosheets.

[0019] Furthermore, in S1, the specific operation of the drying is: drying in a vacuum drying oven at 60 - 70 °C until the moisture content ≤ 1%.

[0020] Further, in S2, the binder is an aqueous solution of polyvinyl alcohol with a mass concentration of 2-2.6%.

[0021] Further, in S2, the mass of the binder is 5-6% of the mass of the final powder.

[0022] The present application has the following beneficial effects:

[0023] 1. The present invention uses boron carbide powder, modified graphene nanosheets and porous carbon fibers to prepare carbon fiber reinforced boron carbide composites; on the one hand, the porous structure of the porous carbon fibers can serve as the anchoring points of the modified graphene nanosheets. Through solid-state diffusion and interfacial wetting, the modified graphene nanosheets are preferentially adsorbed on the pores during the sintering process, forming local high-thermal-conductivity regions. While eliminating the negative impact brought by the pores destroying the axial thermal conductivity continuity of the carbon fibers, it can better transversely connect the porous carbon fibers and form a three-dimensional thermal conduction channel of "fiber-graphene-matrix", synergistically improving the thermal conductivity (thermal conductivity) of the composite material.

[0024] On the other hand, the two-dimensional structure of the modified graphene nanosheets can fill the pores between the porous carbon fibers and the boron carbide matrix, inhibiting the increase of the interfacial thermal resistance. At the same time, the synergistic distribution of the graphene sheets and the porous fibers can also guide the heat flow around the residual pore defects, synergistically improving the overall thermal conduction efficiency.

[0025] 2. In the preparation of the modified graphene nanosheets, silane modification can not only reduce the surface energy of the graphene nanosheets, reduce their agglomeration in the boron carbide matrix, promote the uniform dispersion of the graphene nanosheets and form a continuous interface; but also enhance the interfacial bonding strength between the graphene nanosheets and the boron carbide matrix to a moderate state. Under the action of external stress, local plastic deformation (instead of brittle fracture) can occur through micro-sliding at the interface between the graphene and the boron carbide, absorbing the energy of crack propagation, and thus enhancing the fracture toughness of the composite material.

[0026] In addition, the porous carbon fibers and the modified graphene nanosheets can better form a "fiber-nanosheet" toughening network in the boron carbide matrix. The porous carbon fibers dissipate energy through crack deflection and bridging, and the modified graphene nanosheets inhibit crack propagation through sheet pulling out and slipping, thereby achieving a cross-scale toughening synergistic effect. Description of the Drawings

[0027] Figure 1 The comparison trend chart of the thermal conductivity test data of the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 in the test examples of the present invention;

[0028] Figure 2 The comparison trend chart of the toughness test data of the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 in the test examples of the present invention. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. 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.

[0030] Unless otherwise specified, the raw materials in the embodiments and comparative examples of this application are all commercially available.

[0031] Example 1: (1) Preparation of porous carbon fiber, and the preparation method is as follows: A1. Mix polyacrylonitrile and itaconic acid in a mass ratio of 5:1, dissolve them in dimethyl sulfoxide solvent, magnetically stir at 240 r / min for 4 h at 80 °C until completely dissolved, perform vacuum degassing treatment for 30 min, and prepare a spinning solution with a mass fraction of 12%. Electrospinning (using a 22G needle, spinning voltage of 18 kV, receiving distance of 15 cm, and spinning solution flow rate of 1.2 mL / h) is used to obtain a fiber film. After the fiber film is collected, it is vacuum dried at 60 °C for 24 h to avoid the influence of residual solvent on subsequent treatment.

[0032] A2. Prepare an aqueous solution of diammonium hydrogen phosphate with a mass fraction of 12% using water. Immerse the fiber film in the aqueous solution of diammonium hydrogen phosphate, and the mass ratio of the fiber film to diammonium hydrogen phosphate is 2:5. After stirring at 180 r / min at 50 °C for 6 h, take out the fiber film and dry it in an oven at 90 °C for 3 h, then put it into a tube furnace and carbonize it under a nitrogen atmosphere. Specifically, it is heated to a carbonization temperature of 750 °C at a rate of 5 °C / min, and the carbonization time is 2.5 h. After the carbonization is completed, it is naturally cooled to room temperature. First, centrifuge and wash it twice with 0.1 M HCl solution (centrifuge at 8000 rpm for 10 min each time), then centrifuge and wash it with deionized water until neutral, and then vacuum dry it at 60 °C for 12 h to obtain carbon fiber.

[0033] A3. Prepare a potassium hydroxide (KOH) solution with a concentration of 22 mg / mL using water. Add the carbon fiber to the KOH solution, and the mass ratio of the carbon fiber to KOH is 1:1. Ultrasonically disperse it for 30 min, dry it, and then put it into a tube furnace and calcine it under a nitrogen atmosphere. The calcination includes two stages. The first stage is to heat it to 400 °C at a rate of 3 °C / min and hold it for 1 h. The second stage is to continue heating it to 800 °C at a rate of 2 °C / min and hold it for 2.4 h. Take it out, and alternately wash it 5 times with 1 M HCl solution and deionized water (centrifuge at 8000 rpm for 10 min each time) until neutral (pH = 7), and vacuum dry it at 80 °C for 18 h to obtain porous carbon fiber.

[0034] (2) Prepare modified graphene nanosheets, and the preparation method is as follows: B1. Mix γ-mercaptopropyltrimethoxysilane (KH590) and water at a mass ratio of 8:1, adjust the pH to about 4.0 with 1M hydrochloric acid, and stir at 160 r / min at room temperature for 4 h to promote hydrolysis, obtaining a silane hydrolysis solution.

[0035] B2. Add graphene nanosheets into a 60% (volume fraction) ethanol aqueous solution containing 0.1% (volume fraction) polyethylene glycol (PEG6000), and perform ultrasonic treatment (power 300 W, frequency 20 kHz) for 50 min. Control the temperature in an ice bath to prevent overheating and ensure uniform dispersion, obtaining a 1.5 mg / mL graphene nanosheet dispersion. Among them, the graphene nanosheets (purity ≥ 99.5%) are purchased from Suzhou Beike Nano Technology Co., Ltd.

[0036] B3. Dropwise add the silane hydrolysis solution into the graphene nanosheet dispersion. The mass ratio of graphene nanosheets to γ-mercaptopropyltrimethoxysilane is 1:0.35. After magnetic stirring at 180 r / min at about 60 °C for 12 h, centrifuge the product, wash it alternately with ethanol and deionized water 5 times to remove unreacted γ-mercaptopropyltrimethoxysilane and by-products, and then dry it in a vacuum at 65 °C for 18 h to obtain the modified graphene nanosheets.

[0037] (3) A preparation method of a carbon fiber reinforced boron carbide composite material includes the following steps: S1. By weight, mix 90 parts of boron carbide powder (purity ≥ 99.5%, D50 = 1.2 μm) and 6 parts of modified graphene nanosheets, disperse them in ethanol and perform ultrasonic treatment (power 300 W) for 30 min. The mass of ethanol is 2.2 times the total mass of boron carbide powder and modified graphene nanosheets. Use zirconia balls (diameter 3 mm), and the ball-to-material mass ratio is 6:1. Use a planetary ball mill (rotation speed 300 rpm, alternating forward and reverse, cooling at intervals of 10 min), and the ball milling time is 8 h. Fill the ball milling tank with nitrogen for protection to prevent oxidation. Pass the slurry through a 200-mesh nylon sieve, and dry the filter cake in a vacuum drying oven at 65 °C in two stages. The first stage is atmospheric drying for 2 h, and the second stage is vacuum drying at -0.08 MPa for 3 h, with the water content ≤ 1% to obtain the primary powder.

[0038] S2. By weight in the same standard number of parts, mix the initial powder material with 9 parts of porous carbon fiber (stir at 120 r / min for 1 h) to obtain the final powder material, granulate it with a binder to obtain the mixed granular material. The binder is an aqueous solution of polyvinyl alcohol with a mass fraction of 2.4%, and the mass of the binder is 5.5% of the mass of the final powder material. The specific granulation operation is as follows: Mix the final powder material and the binder in a kneader at a low speed (30 rpm, 15 min) to form a wet material. The wet material is granulated by a screw extrusion granulator (aperture 1.2 mm). The granules are dried in a fluidized bed at 40 °C until the moisture content is about 3%, and then sieved (80 mesh) to remove fine powder and lumps, thus obtaining the mixed granular material.

[0039] S3. Coat the cemented carbide die (cavity size Φ50 mm × 10 mm) with boron nitride release agent, preheat it to 80 °C, pour the mixed granular material into the die, apply bidirectional pressure (290 MPa, hold the pressure for 7 min), the pressing rate is 0.5 mm / s, and the green density is 2.6 g / cm 3 , release the pressure and take out of the die, put it into the furnace, first heat it at a heating rate of 10 °C / min to 1000 °C, and then heat it at a heating rate of 5 °C / min to 2200 °C, hold the temperature for 1.8 h, sinter under vacuum (vacuum degree ≤ 1×10 -2 Pa) without pressure, and cool it naturally in the furnace to 200 °C, then fill it with high-purity argon to accelerate the cooling to room temperature, thus obtaining the carbon fiber reinforced boron carbide composite material.

[0040] Example 2: The difference between this example and Example 1 is as follows: A preparation method of a carbon fiber reinforced boron carbide composite material, including the following steps: S1. By weight, mix 88 parts of boron carbide powder and 5 parts of modified graphene nanosheets, perform wet ball milling treatment, filter, and dry in a vacuum drying oven at 60 °C until the moisture content ≤ 1% to obtain the initial powder material.

[0041] S2. Mix the initial powder material with 8 parts of porous carbon fiber evenly to obtain the final powder material, granulate it with a binder, and sieve it to obtain the mixed granular material. The binder is an aqueous solution of polyvinyl alcohol with a mass concentration of 2%, and the mass of the binder is 5% of the mass of the final powder material.

[0042] S3. Pour the mixed granular material into the die, hold the pressure at 280 MPa for 8 min, then release the pressure and take out of the die, put it into the furnace, first heat it at a heating rate of 10 °C / min to 1000 °C, and then heat it at a heating rate of 5 °C / min to 2100 °C, hold the temperature for 2 h, sinter under vacuum without pressure, and cool it naturally in the furnace to 200 °C, then fill it with high-purity argon to accelerate the cooling to room temperature, thus obtaining the carbon fiber reinforced boron carbide composite material.

[0043] Example 3: The difference between this example and Example 1 lies in: A preparation method of carbon fiber reinforced boron carbide composite material, which comprises the following steps: S1. By weight, mix 92 parts of boron carbide powder and 7 parts of modified graphene nanosheets, perform wet ball milling treatment, filter, and dry in a vacuum drying oven at 70 °C until the moisture content ≤ 1% to obtain the initial powder material.

[0044] S2. Mix the initial powder material with 10 parts of porous carbon fiber evenly to obtain the final powder material, granulate with a binder, and sieve to obtain the mixed granular material. The binder is an aqueous solution of polyvinyl alcohol with a mass concentration of 2.6%, and the mass of the binder is 6% of the mass of the final powder material.

[0045] S3. Pour the mixed granular material into a mold, keep the pressure at 300 MPa for 5 minutes, then relieve the pressure and take out the mold, put it into a furnace, first heat it up to 1000 °C at a heating rate of 10 °C / min, and then heat it up to 2150 °C at a heating rate of 5 °C / min and keep it warm for 2 h for vacuum non-pressure sintering. Naturally cool with the furnace to 200 °C and then fill with high-purity argon to accelerate cooling to room temperature to obtain the carbon fiber reinforced boron carbide composite material.

[0046] Example 4: The difference between this example and Example 1 lies in: A preparation method of carbon fiber reinforced boron carbide composite material, which comprises the following steps: S1. By weight, mix 88 parts of boron carbide powder and 7 parts of modified graphene nanosheets, perform wet ball milling treatment, filter, and dry in a vacuum drying oven at 65 °C until the moisture content ≤ 1% to obtain the initial powder material.

[0047] S2. Mix the initial powder material with 9 parts of porous carbon fiber evenly to obtain the final powder material, granulate with a binder, and sieve to obtain the mixed granular material. The binder is an aqueous solution of polyvinyl alcohol with a mass concentration of 2.4%, and the mass of the binder is 5.5% of the mass of the final powder material.

[0048] S3. Pour the mixed granular material into a mold, keep the pressure at 290 MPa for 6 minutes, then relieve the pressure and take out the mold, put it into a furnace, first heat it up to 1000 °C at a heating rate of 10 °C / min, and then heat it up to 2200 °C at a heating rate of 5 °C / min and keep it warm for 1.8 h for vacuum non-pressure sintering. Naturally cool with the furnace to 200 °C and then fill with high-purity argon to accelerate cooling to room temperature to obtain the carbon fiber reinforced boron carbide composite material.

[0049] Comparative Example 1: The difference between this comparative example and Example 1 is only that: the porous carbon fiber is replaced by carbon fiber, and the modified graphene nanosheets are deleted.

[0050] Specifically, a preparation method of carbon fiber reinforced boron carbide composite material, which comprises the following steps: S1. By weight, mix 90 parts of boron carbide powder and 9 parts of carbon fiber evenly to obtain the final powder material, granulate with a binder, and sieve to obtain the mixed granular material.

[0051] S2. Pour the mixed granular material into the mold, maintain the pressure at 290 MPa for 7 minutes, release the pressure and remove from the mold, put into the furnace, first heat it to 1000°C at a heating rate of 10°C / min, then heat it to 2200°C at a heating rate of 5°C / min, and maintain it for 1.8 hours for vacuum pressureless sintering. After naturally cooling to 200°C in the furnace, fill it with high-purity argon gas to accelerate cooling to room temperature, and obtain carbon fiber reinforced boron carbide composite material.

[0052] Comparative Example 2: The difference between this comparative example and Example 1 is that the modified graphene nanosheets are deleted.

[0053] Comparative Example 3: The difference between this comparative example and Example 1 is that the porous carbon fiber is replaced by carbon fiber.

[0054] Test example: Test object: Composite materials were prepared from Example 1 to Example 4 and Comparative Example 1 to Comparative Example 3. Test items: ① Fracture toughness: tested with reference to SEPB method; ② Thermal conductivity: tested with reference to ASTM D5470. Test results: see Table 1.

[0055] Table 1. Test data of the experimental example

[0056] <![CDATA[Toughness (MPa·m 1 / 2 )]]> Thermal conductivity W / (m·K) Example 1 5.7 47.2 Example 2 5.5 46.9 Example 3 6.0 48.1 Example 4 5.7 47.7 Comparative Example 1 4.4 41.2 Comparative Example 2 4.7 37.5 Comparative Example 3 5.1 44.3

[0057] Result analysis: Analyze Example 1-Example 4 and combine the data in Table 1 and Figure 1 - Figure 2 It can be seen that the toughness of the composite material obtained in the present invention (Example 1-Example 4) reaches 5.5MPa·m 1 / 2 Above, the thermal conductivity reaches above 46.9W / (m·K).

[0058] Analyze Example 1 and Comparative Examples 1-3 and combine the data in Table 1 and Figure 1 - Figure 2 By comparing Comparative Example 1 with Comparative Example 2, it can be seen that compared with Comparative Example 1, Comparative Example 2 replaces carbon fiber with porous carbon fiber, and the toughness test data of the composite material obtained is improved, and the thermal conductivity decreases instead of increasing. This shows that in the carbon fiber + boron carbide system, replacing carbon fiber with porous carbon fiber, that is, introducing a porous structure into the carbon fiber, can improve the toughness of the composite material obtained, but at the same time it will also cause the thermal conductivity of the composite material to decrease.

[0059] This is because replacing carbon fiber with porous carbon fiber introduces a porous structure, which can absorb crack energy and complicate the crack propagation path, thereby slightly improving toughness. However, at the same time, the introduction of a porous structure will also destroy the continuity of thermal conductivity, causing the thermal conductivity (thermal conductivity) of the composite material to decrease instead of increase.

[0060] By comparing Comparative Example 1 and Comparative Example 3, it can be seen that, compared with Comparative Example 1, modified graphene nanosheets are added to the raw material components in Comparative Example 3, and as a result, both the toughness test data and the thermal conductivity test data of the prepared composite material are improved. This shows that adding modified graphene nanosheets to the carbon fiber + boron carbide system can simultaneously improve the toughness and thermal conductivity of the prepared composite material.

[0061] Combined with the comparison of Example 1, it can be seen that, compared with Comparative Example 3, in Example 1, carbon fiber is replaced with porous carbon fiber, and as a result, both the toughness test data and the thermal conductivity test data of the prepared composite material are improved. This shows that in the carbon fiber + boron carbide + modified graphene nanosheet system, replacing carbon fiber with porous carbon fiber, that is, introducing a porous structure into the carbon fiber, can further improve the toughness and thermal conductivity of the prepared composite material. In summary, it can be seen that there is a synergistic effect between porous carbon fiber (introducing a porous structure) and modified graphene nanosheets, which synergistically improves the toughness and thermal conductivity of the finally prepared composite material.

[0062] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a carbon fiber reinforced boron carbide composite material, characterized in that, It includes the following steps: S1. By weight parts, mix 88 - 92 parts of boron carbide powder and 5 - 7 parts of modified graphene nanosheets, conduct wet ball milling treatment, filter, and dry to obtain preliminary powder materials; the modified graphene nanosheets are prepared by modifying graphene nanosheets with a silane coupling agent; S2. Mix the preliminary powder materials obtained in S1 with 8 - 10 parts of porous carbon fibers evenly to obtain final powder materials, granulate with a binder, and sieve to obtain mixed granular materials; S3. Pour the mixed granular materials obtained in S2 into a mold, keep the pressure at 280 - 300 MPa for 5 - 8 min, then relieve the pressure and take out of the mold, conduct vacuum non-pressure sintering at 2100 - 2300 °C for 1.5 - 2 h, and cool to room temperature with the furnace, thus obtaining the carbon fiber reinforced boron carbide composite material.

2. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 1, characterized in that, The preparation method of the porous carbon fiber is as follows: A1. Mix polyacrylonitrile and itaconic acid, dissolve them in dimethyl sulfoxide, and prepare a spinning solution with a mass fraction of 11 - 13%, and electrospin to obtain a fiber film; A2. Immerse the fiber film obtained in A1 into an aqueous solution of diammonium hydrogen phosphate, stir at room temperature, dry, carbonize in an inert atmosphere, centrifuge and wash until neutral, and dry to obtain carbon fibers; A3. Add the carbon fibers obtained in A2 into a KOH solution, stir, dry, calcine in an inert atmosphere, wash until neutral, and dry to obtain porous carbon fibers.

3. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 2, characterized in that, In A2, the mass fraction of the aqueous solution of diammonium hydrogen phosphate is 10 - 12%.

4. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 2, wherein, In A2, the carbonization temperature is 700 - 800 °C and the carbonization time is 2 - 2.5 h; in A3, the calcination includes two stages, the first stage is to keep the temperature at 400 ± 10 °C for 1 - 1.2 h, and the second stage is to keep the temperature at 800 ± 10 °C for 2 - 2.2 h.

5. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 2, wherein, In A3, the concentration of the KOH solution is 20 - 25 mg / mL.

6. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 1, characterized in that, The silane coupling agent includes γ-mercaptopropyltrimethoxysilane and / or 3-aminopropyltriethoxysilane.

7. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 1, wherein, In S1, in the wet ball milling treatment, ethanol is used as the wet milling solvent, and the mass of the wet milling solvent is 2 - 2.5 times the total mass of the boron carbide powder and the modified graphene nanosheets; zirconia balls / tungsten carbide balls are used as the wet milling balls, and the mass of the wet milling balls is 5 - 8 times the total mass of the boron carbide powder and the modified graphene nanosheets.

8. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 1, wherein, In S1, the specific operation of the drying is: dry in a vacuum drying oven at 60 - 70 °C until the moisture content ≤ 1%.

9. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 1, characterized in that, In S2, the binder is an aqueous solution of polyvinyl alcohol with a mass concentration of 2 - 2.6%.

10. The preparation method of the carbon fiber reinforced boron carbide composite material according to claim 1, characterized in that, In S2, the mass of the binder is 5 - 6% of the mass of the final powder materials.

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