A method for preparing a controllable CNTs@PyC interface layer in carbon / carbon composite material

Abstract

A preparation method of a controllable CNTs@PyC interface layer in carbon / carbon composite material, ZIF-67 with different distribution patterns is carried on the surface of carbon fiber; CNTs are in-situ generated from ZIF-67 through chemical vapor deposition, CNTs are distributed on the surface of carbon fiber in different growth patterns; PyC is deposited on the surface of carbon fiber, different shapes of CNTs@PyC interface layer shape are obtained, by controlling the different growth patterns of ZIF-67 on the surface of carbon fiber, the different distribution states of CNTs derived exist, so as to realize the controllable and adjustable interface layer shape, to meet the application requirements under different conditions: the circular ring shape reduces the stress concentration of CNTs@PyC interface layer, avoids a large number of cracks in the composite material. The wave shape is beneficial to the application of carbon / carbon composite material in the service environment under the tensile condition, prolongs the crack propagation path along the interface layer, effectively relieves the PyC ring cracking phenomenon around the fiber, and is more easy to realize the interlocking effect between the interface layer and the carbon matrix, effectively prevents the interface debonding phenomenon, and greatly improves the mechanical properties of carbon / carbon composite material.

Description

A method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material Technical Field

[0001] This invention relates to the field of carbon / carbon composite material interface modification technology, specifically to a method for constructing fiber / matrix interface layers of different shapes on the surface of carbon fibers by utilizing the ability of metal-organic framework material ZIF-67 to derive carbon nanotubes (CNTs). Background Technology

[0002] Carbon / carbon composites are lightweight, high-strength, and high-temperature resistant composite materials, widely used in mechanical structural components in aerospace and other fields due to their excellent physicochemical properties. The fiber / matrix interface layer is a crucial factor affecting the overall mechanical properties of fiber-reinforced composites. A suitable interface layer can effectively transfer the load on the matrix to the fibers, achieving load dispersion and improving the load-bearing capacity of the composite. However, the relatively smooth surface of carbon fibers used in carbon / carbon composites results in weak interfacial bonding between them and the carbon matrix, severely limiting further improvements in the load-bearing capacity of carbon / carbon composites. Therefore, modifying the fiber / matrix interface layer by attaching nanomaterials to the carbon fiber surface is a research hotspot in the modification of the interface layer of carbon / carbon composites. CNTs (carbon nanotubes) have good compatibility with carbon / carbon composites and are commonly used as nano-reinforcements.

[0003] Currently, common processes for mounting CNTs on carbon fiber surfaces include electrophoresis, chemical grafting, and chemical vapor deposition (CVD). CVD allows for in-situ growth of CNTs on carbon fiber surfaces and provides flexible control over the growth orientation of CNTs, making it a highly promising CNT preparation process. When carbon fibers with CNTs mounted on their surfaces are subjected to a carbon deposition process to deposit pyrolytic carbon (PyC), the carbon fiber / carbon matrix interface layer becomes rich in CNTs (hereinafter referred to as the CNTs@PyC interface layer), thus modifying the interface layer. For example, in Feng L, Li KZ, Sun JJ, et al. Influence of carbon nanotube extending length on pyrocarbon microstructure and mechanical behavior of carbon / carbon composites[J]. Applied Surface Science, 2015, 355: 1020-1027 and Feng L, Li KZ, Xue B, et al. Optimizing matrix and fiber / matrix interface to achieve combination of strength, ductility and toughness in carbon nanotube-reinforced carbon / carbon composites[J]. Materials & Design, 2017, 113: 9-16, it was proposed to use chemical vapor deposition to prepare coiled and upright CNTs respectively, which improved the compressive properties of carbon / carbon composites by 200.0% and 81.5% respectively. It is not difficult to find that the CNTs prepared by chemical vapor deposition are uniformly distributed on the carbon fiber surface in a covering form, and the final CNTs@PyC interface layer surrounds the carbon fiber in a single ring shape. However, different interface layer shapes produce different strengthening effects. Therefore, by structurally designing the interface of CNTs-reinforced carbon / carbon composites, carbon / carbon composites can meet the application requirements under different service conditions. That is, by controlling the microstructure and distribution of CNTs on the carbon fiber surface, CNTs@PyC interface layers of different shapes can be constructed, and the strengthening effect of different structural interface layers on carbon / carbon composites can be explored.

[0004] Metal-organic frameworks (MOFs) are composed of metal ions and organic ligands. ZIF-67, as one type of MOF, has been demonstrated in the literature Zhu XY, Qiu HF, Chen P, et al. Anemone-shaped ZIF-67@CNTs as effective electromagnetic absorbent covered the whole X-band[J]. Carbon, 2021, 173: 1-10, to have great potential for CNT derivatization. However, CNTs derived from ZIF-67 are mostly used in special functional fields, such as chemical catalysis and microwave absorption, and their role in modifying the interface of composite materials has not yet been observed. Summary of the Invention

[0005] To improve the reinforcing effect of CNTs on carbon / carbon composites and change the monotony of the shape of existing carbon fiber / carbon matrix interface layers, this invention proposes a method for preparing a controllable CNTs@PyC interface layer in carbon / carbon composites.

[0006] The specific process of this invention is as follows:

[0007] Step 1, Pretreatment of carbon fiber cloth:

[0008] Cut multiple pieces of carbon fiber cloth, ultrasonically clean and dry them for later use;

[0009] Step 2, prepare the mixed solution:

[0010] The mixed solution is prepared by mixing cobalt nitrate solution and 2-methylimidazole solution.

[0011] To prepare this mixed solution, a cobalt nitrate solution and a 2-methylimidazole solution with a volume ratio of 1:1 are mixed and magnetically stirred for 60 seconds to obtain a homogeneous mixed solution. The concentration ratio of the cobalt nitrate solution to the 2-methylimidazole solution is 1:4.

[0012] The cobalt nitrate solution is prepared by dissolving cobalt nitrate hexahydrate powder in methanol and stirring until homogeneous. The concentration of the cobalt nitrate solution is 0.02–0.1 mol / L.

[0013] The 2-methylimidazole solution is prepared by dissolving 2-methylimidazole powder in methanol and stirring until homogeneous. The concentration of the 2-methylimidazole solution is 0.08–0.4 mol / L.

[0014] Step 3, ZIF-67 is mounted on the surface of the carbon fiber cloth:

[0015] By synthesizing ZIF-67, carbon fiber cloth with ZIF-67 on its surface was obtained.

[0016] The specific process of mounting ZIF-67 on the surface of carbon fiber cloth is as follows:

[0017] I. Synthesis of ZIF-67. The multiple carbon fiber cloths obtained in step 1 are immersed in the mixed solution described in step 2; the mixed solution containing the carbon fiber cloths is placed in a water bath at 30-50°C and heated at a constant temperature for 1 hour, so that cobalt nitrate in the mixed solution reacts chemically with 2-methylimidazole, thereby synthesizing ZIF-67 with a dodecahedral shape along the surface of the carbon fibers, resulting in multiple carbon fiber cloths with ZIF-67 on their surface.

[0018] II. Washing the carbon fiber cloth. After heating in a water bath for 1 hour, remove the carbon fiber cloths with ZIF-67 coating, rinse them three times with methanol reagent, and dry them in a 70°C oven.

[0019] Step 4, Synthesis of CNTs by Chemical Vapor Deposition:

[0020] I. Preparation for Chemical Vapor Deposition: Weigh melamine powder and spread it evenly under the graphite crucible. Place the carbon fiber cloth with ZIF-67 coated on its surface obtained in step 3 on top of the melamine powder. After sealing the graphite crucible, place it inside the quartz tube of a tubular heat treatment furnace, ready for the chemical vapor deposition process.

[0021] The amount of melamine powder used is determined based on the total mass of carbon fiber cloth in the graphite crucible; the ratio of melamine mass to total carbon fiber cloth mass is 1:3; the ratio is a mass ratio.

[0022] II. Synthesis of CNTs by Chemical Vapor Deposition: A tubular heat treatment furnace was set up to heat to 800-900℃ at a heating rate of 5℃ / min and held for 2 hours. After the holding period, the carbon fiber cloth was cooled to room temperature with the furnace to obtain carbon fiber cloth with CNTs distributed on the carbon fiber surface.

[0023] During the heating and cooling of the tubular heat treatment furnace, argon gas is continuously introduced into the quartz tube of the furnace; the argon gas flow rate is 200 sccm.

[0024] Step 5: Prepare carbon cloth laminated 2D carbon / carbon composite material:

[0025] I. Fabrication of 2D carbon fiber preforms with carbon cloth laminates:

[0026] Take multiple pieces of carbon fiber fabric with CNTs distributed on the surface of the carbon fiber obtained in step 4. Stack and sew them along the normal direction of the carbon fiber fabric plane. Obtain a 2D carbon fiber preform with carbon fiber fabric laminate.

[0027] When stacking, keep the four sides of the multiple carbon fiber fabrics vertically aligned and ensure that each layer of the fabric is in full contact. When sewing, use a carbon fiber bundle containing 1,000 carbon fibers to pass through an embroidery needle with a diameter of 0.6 mm. Tie the end of the carbon fiber bundle into a knot. Insert the embroidery needle along the inside of the four sides of the carbon fiber fabric every 5 mm until the four sides are completely sewn. Finally, tighten the carbon fiber bundle and tie the end of the carbon fiber bundle into a knot.

[0028] II. Preparation of carbon / carbon composite materials:

[0029] Carbon fiber preforms with carbon cloth laminates are subjected to carbon deposition treatment through chemical vapor infiltration. After the preforms are densified, a 2D carbon / carbon composite material with a CNTs@PyC interface layer is obtained.

[0030] The density of the carbon cloth laminated 2D carbon / carbon composite material is 1.66–1.68 g / cm³. 3 .

[0031] The specific process for preparing the 2D carbon / carbon composite material with the CNTs@PyC interface layer is as follows: A carbon cloth laminated 2D carbon fiber preform is placed in the furnace tube of an isothermal chemical vapor deposition (CVD) furnace. The furnace temperature is controlled to rise to 1200°C at a rate of 5°C / min. During the heating period, argon gas is continuously introduced into the furnace tube at a flow rate of 100 sccm. When the CVD furnace reaches 1200°C, methane gas is introduced into the furnace tube at a flow rate of 500 sccm, and argon gas is introduced into the furnace tube at a flow rate of 2000 sccm, maintaining this for 150 hours. After 150 hours of deposition, the methane gas is stopped, the argon gas flow rate is adjusted to 100 sccm, the CVD furnace is shut off, and the furnace is allowed to cool naturally to room temperature.

[0032] This invention first mounts ZIF-67 with different distribution morphologies on the carbon fiber surface, then uses chemical vapor deposition to induce CNTs to grow in situ on the ZIF-67, so that the CNTs are distributed on the carbon fiber surface with different growth morphologies. Finally, PyC is deposited on the carbon fiber surface using chemical vapor infiltration process to obtain CNTs@PyC interface layer shapes with different shapes.

[0033] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0034] This invention controls the growth morphology of ZIF-67 on the carbon fiber surface, resulting in different distribution states of the derived CNTs. This allows for controllable and adjustable interface layer shape, meeting application requirements under various conditions. Specific benefits are as follows:

[0035] 1. The prepared CNTs are dispersed on the carbon fiber surface with different morphologies, ultimately altering the shape of the CNTs@PyC interface layer. By controlling the concentration of the cobalt nitrate and 2-methylimidazole mixed solution used in the synthesis of ZIF-67, the distribution of ZIF-67 on the carbon fiber surface can be controlled. ZIF-67 also possesses the ability to synthesize CNTs in situ, thus enabling control over the growth morphology of CNTs on the carbon fiber surface. When CNTs are neatly and densely distributed on the carbon fiber surface, the final carbon / carbon composite fiber / matrix interface layer, i.e., the CNTs@PyC interface layer, exhibits a ring shape; when CNTs are dispersed on the carbon fiber surface, the CNTs@PyC interface layer exhibits a wavy shape. The formation principle of the wavy CNTs@PyC interface layer is given in Figure 1. Simply put, the CNTs synthesized by ZIF-67 catalysis first densify to form carbon spheres, which in turn affects the shape of the outer PyC deposition, ultimately resulting in a wavy CNTs / PyC interface layer.

[0036] 2. Different shapes of CNTs@PyC interface layers can meet application requirements under different conditions. Circular CNTs@PyC interface layers are beneficial for carbon / carbon composites in service environments under compression conditions. The circular shape reduces stress concentration at the CNTs@PyC interface layer, preventing numerous cracks from forming inside the composite material due to stress concentration. Wavy CNTs@PyC interface layers are beneficial for carbon / carbon composites in service environments under tension conditions. The wavy shape lengthens the crack propagation path along the interface layer, effectively mitigating the ring-shaped cracking phenomenon around the PyC fibers. Furthermore, wavy CNTs@PyC interface layers facilitate the interlocking effect between the interface layer and the carbon matrix, effectively preventing interface debonding and significantly improving the mechanical properties of carbon / carbon composites.

[0037] 3. This invention obtained CNTs@PyC interface layers of different shapes through process control. The mechanical properties of carbon / carbon composites containing interface layers of different shapes all showed good enhancement results. Specifically, the annular CNTs@PyC interface layer increased the out-of-plane compressive strength and flexural strength of the carbon / carbon composite by 76.1% and 28.1%, respectively; the wavy CNTs@PyC interface layer increased the out-of-plane compressive strength and flexural strength of the carbon / carbon composite by 67.3% and 57.5%, respectively. Attached Figure Description

[0038] Figure 1 is a block diagram illustrating the forming principle of the wave-shaped CNTs@PyC interface layer of the present invention;

[0039] Figure 2 is a SEM image of the ZIF-67 distribution morphology on the carbon fiber surface in Embodiment 1 of the present invention;

[0040] Figure 3 is a SEM image of the CNT distribution morphology on the carbon fiber surface in Embodiment 1 of the present invention;

[0041] Figure 4 is a SEM image of the CNTs@PyC interface layer in Embodiment 1 of the present invention;

[0042] Figure 5 is a SEM image of the ZIF-67 distribution morphology on the carbon fiber surface in Example 2 of the present invention;

[0043] Figure 6 is a SEM image of the CNT distribution morphology on the carbon fiber surface in Embodiment 2 of the present invention;

[0044] Figure 7 is a SEM image of the CNTs@PyC interface layer in Embodiment 2 of the present invention;

[0045] Figure 8 is a SEM image of the ZIF-67 distribution morphology on the carbon fiber surface in Example 3 of the present invention;

[0046] Figure 9 is a SEM image of the CNT distribution morphology on the carbon fiber surface in Example 3 of the present invention;

[0047] Figure 10 is a SEM image of the CNTs@PyC interface layer in Embodiment 3 of the present invention;

[0048] Figure 11 is a SEM image of the carbon fiber surface in Comparative Example 1 of the present invention;

[0049] Figure 12 is a SEM image of the carbon fiber / PyC interface layer in Comparative Example 1 of the present invention.

[0050] Figure 13 is a flowchart of the present invention.

[0051] In the figure: 1. PyC represents pyrolytic carbon in carbon / carbon composite material; 2. CF represents carbon fiber in carbon / carbon composite material; 3. CNTs represent carbon nanotubes introduced into carbon / carbon composite material; 4. Carbon spheres are the densification products of CNTs synthesized using ZIF-67 in this invention; 5. Wavy indicates that the shape of PyC is wavy at this time. Detailed Implementation

[0052] This invention relates to a method for preparing a controllable CNTs@PyC interface layer in carbon / carbon composite materials, and its technical solution will be specifically illustrated through three examples and one comparative example.

[0053] The specific process of this invention is as follows:

[0054] Step 1, Pretreatment of carbon fiber cloth:

[0055] Cut carbon fiber cloth with dimensions of 40-60mm x 50-80mm, ultrasonically clean it in deionized water for 2 minutes, and then dry it in a 70℃ oven for later use.

[0056] Step 2, prepare the mixed solution:

[0057] The mixed solution is prepared by mixing cobalt nitrate solution and 2-methylimidazole solution.

[0058] To prepare this mixed solution, a cobalt nitrate solution and a 2-methylimidazole solution with a volume ratio of 1:1 are mixed and magnetically stirred for 60 seconds to obtain a homogeneous mixed solution. The concentration ratio of the cobalt nitrate solution to the 2-methylimidazole solution is 1:4.

[0059] The cobalt nitrate solution is prepared by dissolving cobalt nitrate hexahydrate powder in methanol and stirring until homogeneous. The concentration of the cobalt nitrate solution is 0.02–0.1 mol / L, meaning that 0.02–0.1 mol of cobalt nitrate hexahydrate is dissolved in every 1 L of methanol.

[0060] The 2-methylimidazole solution is prepared by dissolving 2-methylimidazole powder in methanol and stirring until homogeneous, using methanol as the solvent. The concentration of the 2-methylimidazole solution is 0.08–0.4 mol / L, meaning that 0.08–0.4 mol of 2-methylimidazole is dissolved in every 1 L of methanol.

[0061] Table 1 Parameters of each embodiment in step 2

[0062]

[0063] Step 3, ZIF-67 is mounted on the surface of the carbon fiber cloth:

[0064] I. Synthesis of ZIF-67. Several pieces of carbon fiber cloth described in step 1 are immersed in the mixed solution described in step 2; the mixed solution containing the carbon fiber cloth is placed in a water bath at 30-50°C and heated at a constant temperature for 1 hour, so that cobalt nitrate in the mixed solution reacts chemically with 2-methylimidazole, thereby synthesizing ZIF-67 with a regular dodecahedral shape along the surface of the carbon fiber, and obtaining carbon fiber cloth with ZIF-67 on its surface.

[0065] II. Washing the carbon fiber cloth. After heating in a water bath for 1 hour, remove the carbon fiber cloth with ZIF-67 coating, rinse it three times with methanol reagent, and dry it in a 70℃ oven.

[0066] Table 2 Parameters of each embodiment in step 3

[0067]

[0068]

[0069] Step 4, Synthesis of CNTs by Chemical Vapor Deposition:

[0070] I. Preparation for Chemical Vapor Deposition: Weigh an appropriate amount of melamine powder and spread it evenly under the graphite crucible. Place the dried carbon fiber cloth with ZIF-67 surface loaded in step 3 on top of the melamine powder. After sealing the graphite crucible, place it inside the quartz tube of a tubular heat treatment furnace, ready for the chemical vapor deposition process.

[0071] The amount of melamine powder used is determined based on the total mass of carbon fiber cloth in the graphite crucible; the ratio of melamine mass to total carbon fiber cloth mass is 1:3; the ratio is a mass ratio.

[0072] II. Synthesis of CNTs by Chemical Vapor Deposition: A tubular heat treatment furnace was set up to heat to 800-900℃ at a heating rate of 5℃ / min and held for 2 hours. After the holding period, the carbon fiber cloth was cooled to room temperature with the furnace to obtain carbon fiber cloth with CNTs distributed on the carbon fiber surface.

[0073] During the heating and cooling of the tubular heat treatment furnace, argon gas is continuously introduced into the quartz tube of the furnace at a flow rate of 200 sccm.

[0074] Table 3 Parameters of each embodiment in step 4

[0075]

[0076] Step 5: Prepare carbon cloth laminated 2D carbon / carbon composite material:

[0077] I. Fabrication of 2D carbon fiber preforms with carbon cloth laminates:

[0078] Take 20-30 pieces of carbon fiber fabric with CNTs distributed on the surface as described in step 4. Stack and sew them along the normal direction of the carbon fiber fabric plane. When stacking, the 20-30 pieces of carbon fiber fabric should keep the four sides perpendicularly aligned, and each layer of plane should be in complete contact. When sewing, use a carbon fiber bundle containing 1000 carbon fibers to pass through a 0.6mm diameter embroidery needle, tie the end of the carbon fiber bundle into a knot, and insert the embroidery needle every 5mm along the inside of the four sides of the carbon fiber fabric until the four sides are completely sewn. Finally, tighten the carbon fiber bundle and tie the head of the carbon fiber bundle into a knot. The final product is a 2D carbon fiber preform with carbon fiber fabric lamination.

[0079] II. Preparation of carbon / carbon composite materials:

[0080] Carbon fiber laminated 2D carbon fiber preforms were subjected to carbon deposition treatment using a chemical vapor infiltration process. After densification, a 2D carbon / carbon composite material with a CNTs@PyC interface layer was obtained. The density of the carbon fiber laminated 2D carbon / carbon composite material was 1.68 g / cm³. 3 .

[0081] The specific process for preparing the 2D carbon / carbon composite material with the CNTs@PyC interface layer is as follows: A carbon cloth laminated 2D carbon fiber preform is placed in the furnace tube of an isothermal chemical vapor deposition (CVD) furnace. The furnace temperature is controlled to rise to 1200°C at a rate of 5°C / min, with argon gas continuously introduced into the furnace tube at a flow rate of 100 sccm during the heating period. Once the furnace reaches 1200°C, methane gas is introduced into the furnace tube at a flow rate of 500 sccm, and argon gas is introduced at a flow rate of 2000 sccm, maintaining this for 150 hours. After 150 hours of deposition, the methane gas is stopped, the argon gas flow rate is adjusted to 100 sccm, and the furnace is shut down, allowing it to cool naturally to room temperature. Finally, the carbon cloth laminated 2D carbon / carbon composite material is obtained.

[0082] The distribution of ZIF-67 on the carbon fiber surface and the synthesized CNTs were observed by SEM, as shown in Figures 2 and 3 of the accompanying description. ZIF-67 is relatively dispersed on the carbon fiber surface, and the distribution of the in-situ synthesized CNTs is similar to that of ZIF-67. The SEM image of the carbon / carbon composite CNTs@PyC interface layer prepared in this example is shown in Figure 4 of the accompanying description. Due to the influence of the CNTs distribution morphology, the CNTs@PyC interface layer exhibits a wavy morphology.

[0083] Table 4 Parameters of each embodiment in step 5

[0084]

[0085]

[0086] Mechanical property tests were conducted on the carbon / carbon composite materials obtained in various embodiments of the present invention. The results showed that the out-of-plane compressive strength of the carbon / carbon composite material was 331–361 MPa, which was 61.4%–76.1% higher than that of the carbon / carbon composite material without the CNTs / PyC interface layer; the three-point flexural strength was 256–315 MPa, which was 28.1%–57.5% higher than that of the carbon / carbon composite material without the CNTs / PyC interface layer.

[0087] Table 5. Mechanical property test parameters of carbon / carbon composite materials obtained in each embodiment.

[0088]

[0089] This invention provides a comparative example. The specific process of this comparative example is as follows:

[0090] Step 1, carbon fiber cloth pretreatment:

[0091] Cut a piece of carbon fiber cloth with a size of 60mm x 80mm, ultrasonically clean it in deionized water for 2 minutes, and then dry it in a 70℃ oven for later use.

[0092] Step 2, prepare carbon cloth laminated 2D carbon / carbon composite material:

[0093] Ⅰ. Fabrication of carbon cloth laminated 2D carbon fiber preform: Take 25 pieces of carbon fiber cloth described in step 1, stack them along the normal direction of the carbon fiber cloth plane and sew them together to obtain carbon cloth laminated 2D carbon fiber preform.

[0094] II. Preparation of Carbon / Carbon Composite Material: A carbon cloth laminated 2D carbon fiber preform was subjected to carbon deposition treatment using a chemical vapor infiltration process. After densification of the preform, a 2D carbon / carbon composite material was obtained. The density of the carbon cloth laminated 2D carbon / carbon composite material was 1.68 g / cm³. 3 .

[0095] The carbon fiber surface was observed using SEM, as shown in Figure 11 of the accompanying description. The carbon fiber surface is smooth and free of ZIF-67 and CNTs. The SEM image of the carbon / carbon composite carbon fiber / PyC interface layer prepared in this example is shown in Figure 12 of the accompanying description. Due to the influence of the carbon fiber surface shape, the carbon fiber / PyC interface layer exhibits a ring shape.

[0096] The mechanical properties of the carbon / carbon composite material finally obtained in this embodiment were tested. The results showed that the out-of-plane compressive strength and three-point bending strength of the pure carbon / carbon composite material were 205 MPa and 200 MPa, respectively.

Claims

1. A method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material, characterized in that, The specific process is as follows: Step 1, pretreatment of carbon fiber cloth: multiple pieces of carbon fiber cloth are cut, ultrasonically cleaned, and dried for later use; Step 2, preparation of mixed solution: the mixed solution is prepared by mixing cobalt nitrate solution and 2-methylimidazole solution; when preparing the mixed solution, cobalt nitrate solution and 2-methylimidazole solution with a volume ratio of 1:1 are mixed and magnetically stirred for 60 seconds to obtain a uniformly mixed solution; the ratio of the concentration of cobalt nitrate solution to the concentration of 2-methylimidazole solution is 1:4; Step 3, ZIF-67 is loaded onto the surface of carbon fiber cloth: ZIF-67 is synthesized to obtain carbon fiber cloth with ZIF-67 loaded on the surface; Step 4, synthesis of CNTs by chemical vapor deposition: I Preparation for chemical vapor deposition: Weigh melamine powder and spread it evenly under a graphite crucible. Place the carbon fiber cloth with ZIF-67 coating obtained in step 3 on top of the melamine powder. After sealing the graphite crucible, place it inside the quartz tube of a tubular heat treatment furnace, ready for the chemical vapor deposition process. The amount of melamine powder used is determined according to the total mass of the carbon fiber cloth in the graphite crucible. The ratio of melamine mass to total carbon fiber cloth mass is 1:

3. II. Synthesis of CNTs by chemical vapor deposition: Set the tubular heat treatment furnace to 800℃, with a heating rate of 5℃ / min, and hold for 2 hours. After the heat preservation is completed, the carbon fiber cloth is cooled to room temperature with the furnace to obtain carbon fiber cloth with CNTs distributed on the surface of the carbon fiber; Step 5, prepare carbon cloth laminated 2D carbon / carbon composite material: Ⅰ Make carbon cloth laminated 2D carbon fiber preform: take multiple pieces of carbon fiber cloth with CNTs distributed on the surface of the carbon fiber obtained in step 4; stack and sew them along the normal direction of the carbon fiber cloth plane. II. Preparation of carbon / carbon composite material: The carbon cloth laminated 2D carbon fiber preform is subjected to carbon deposition treatment by chemical vapor infiltration process. After the preform is densified, a 2D carbon / carbon composite material with CNTs@PyC interface layer is obtained.

2. The method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material as described in claim 1, characterized in that, The cobalt nitrate solution is prepared by dissolving cobalt nitrate hexahydrate powder in methanol and stirring until homogeneous, using methanol as the solvent; the concentration of the cobalt nitrate solution is 0.02~0.1 mol / L.

3. The method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material as described in claim 1, characterized in that, The 2-methylimidazole solution is prepared by dissolving 2-methylimidazole powder in methanol and stirring until homogeneous, using methanol as the solvent; the concentration of the 2-methylimidazole solution is 0.08~0.4 mol / L.

4. The method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material as described in claim 1, characterized in that, The specific process of mounting ZIF-67 on the surface of carbon fiber cloth in step 3 is as follows: Ⅰ Synthesize ZIF-67; Immerse multiple pieces of carbon fiber cloth obtained in step 1 into the mixed solution described in step 2; Place the mixed solution containing the carbon fiber cloth in a 30°C water bath and heat it at a constant temperature for 1 hour, so that cobalt nitrate in the mixed solution reacts chemically with 2-methylimidazole to synthesize ZIF-67 with a dodecahedral shape along the surface of the carbon fiber, and obtain multiple pieces of carbon fiber cloth with ZIF-67 mounted on the surface; Ⅱ Wash the carbon fiber cloth; After heating in the water bath at a constant temperature for 1 hour, take out each piece of carbon fiber cloth with ZIF-67 mounted on the surface, rinse it three times with methanol reagent, and dry it in a 70°C oven.

5. The method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material as described in claim 1, characterized in that, In step 4, during the heating and cooling of the tubular heat treatment furnace, argon gas is continuously introduced into the quartz tube of the tubular heat treatment furnace; the argon gas flow rate is 200 sccm.

6. The method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material as described in claim 1, characterized in that, In step 5, when stacking, keep the four sides of the multiple carbon fiber fabrics vertically aligned and ensure that each layer of the fabric is in full contact. When sewing, use a carbon fiber bundle containing 1,000 carbon fibers to pass through an embroidery needle with a diameter of 0.6 mm. Tie the end of the carbon fiber bundle into a knot. Insert the embroidery needle along the inside of the four sides of the carbon fiber fabric every 5 mm until the four sides are completely sewn. Finally, tighten the carbon fiber bundle and tie the end of the carbon fiber bundle into a knot.

7. The method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material as described in claim 1, characterized in that, The specific process for preparing the 2D carbon / carbon composite material with the CNTs@PyC interface layer in step 5 is as follows: A carbon cloth laminated 2D carbon fiber preform is placed in the furnace tube of an isothermal chemical vapor deposition (CVD) furnace. The CVD furnace is heated to 1200°C at a rate of 5°C / min. During the heating period, argon gas is continuously introduced into the furnace tube at a flow rate of 100 sccm. When the CVD furnace reaches 1200°C, methane gas is introduced into the furnace tube at a flow rate of 500 sccm, and argon gas is introduced into the furnace tube at a flow rate of 2000 sccm, maintaining this for 150 hours. After 150 hours of deposition, the methane gas is stopped, the argon gas flow rate is adjusted to 100 sccm, the CVD furnace is shut off, and the furnace is allowed to cool naturally to room temperature.

8. The method for preparing a controllable CNTs@PyC interface layer in a carbon / carbon composite material as described in claim 1, characterized in that, The density of the carbon cloth laminated 2D carbon / carbon composite material is 1.66~1.68 g / cm³. 3 .

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