A non-ablative directional thermally conductive composite material and its preparation method

Abstract

This invention provides a non-ablative directional thermally conductive composite material and its preparation method, belonging to the technical field of thermal protection materials. The preparation method of the non-ablative directional thermally conductive composite material includes the following steps: S1. Mixing phenolic resin, catalyst, and solvent to obtain a precursor solution; S2. Placing the directional thermally conductive framework material in the precursor solution for vacuum impregnation, sol-gel reaction, drying, and carbonization treatment to obtain the non-ablative directional thermally conductive composite material; the directional thermally conductive framework material consists of at least one alternating layer of heat-insulating fiber and heat-conducting fiber. The non-ablative directional thermally conductive composite material provided by this invention has thermal insulation properties along the vertical in-plane direction and high thermal conductivity along the in-plane direction, which can rapidly conduct locally generated high temperatures to other low-temperature areas, achieving heat homogenization, effectively preventing excessively high local temperatures, thereby increasing the service temperature of the material and significantly improving the thermal insulation efficiency of thermal protection materials.

Description

Technical Field

[0001] This invention belongs to the field of thermal protection materials technology, and specifically relates to a non-ablative directional thermal conductive composite material and its preparation method. Background Technology

[0002] Currently, existing non-ablative thermal insulation materials in the field of thermal protection exhibit low thermal conductivity in all internal directions, failing to rapidly dissipate locally generated high temperatures to other low-temperature zones and achieve heat homogenization. This results in low insulation efficiency and a tendency to generate sharp singularities. Therefore, there is an urgent need to provide a thermal protection material that can quickly dissipate locally generated high temperatures to other low-temperature zones and possesses high insulation efficiency. This would allow for an increase in the operating temperature of thermal protection materials while ensuring thermal insulation safety, enabling them to meet the demands of more demanding application scenarios. Summary of the Invention

[0003] To address one or more technical problems existing in the prior art, the present invention provides a non-ablative directional thermal conductive composite material and its preparation method. The non-ablative directional thermal conductive composite material provided by the present invention has thermal insulation properties along the vertical in-plane direction and high thermal conductivity along the in-plane direction. It can quickly conduct locally generated high temperatures to other low-temperature areas, realize heat homogenization, effectively prevent the phenomenon of excessively high local temperatures, thereby increasing the service temperature of the material and significantly improving the thermal insulation efficiency of thermal protection materials.

[0004] The present invention provides a method for preparing a non-ablative directional thermally conductive composite material in a first aspect, the method comprising the following steps:

[0005] S1. Mix phenolic resin, catalyst and solvent to obtain precursor solution;

[0006] S2. The directional thermally conductive framework material is placed in a precursor solution and subjected to vacuum impregnation, sol-gel reaction, drying, and carbonization to obtain the non-ablative directional thermally conductive composite material.

[0007] The directional heat-conducting skeleton material consists of at least one alternating layer of heat-insulating fiber and one layer of heat-conducting fiber.

[0008] Preferably, the phenolic resin and catalyst account for 15-25% of the mass of the precursor solution; more preferably, the phenolic resin is a thermosetting phenolic resin; and the catalyst is hexamethylenetetramine.

[0009] Preferably, the mass ratio of the phenolic resin to the catalyst is (5-8):1.

[0010] Preferably, the directional heat-conducting skeleton material is obtained by integral curing and heat treatment of alternating layers of heat-insulating fiber and heat-conducting fiber;

[0011] Preferably, the directional heat-conducting skeleton material has one more heat-insulating fiber layer than the heat-conducting fiber layer.

[0012] Preferably, the heat-insulating fiber layer comprises viscose-based carbon fiber and phenolic resin; more preferably, the mass ratio of the viscose-based carbon fiber and phenolic resin is 1:1.

[0013] Preferably, the thermally conductive fiber layer comprises highly thermally conductive carbon fiber and phenolic resin; more preferably, the mass ratio of the highly thermally conductive carbon fiber to the phenolic resin is 1:1.

[0014] Preferably, the number of thermally conductive fiber layers in the directional thermally conductive skeleton material is 1 to 4; more preferably, the thickness of a single thermally conductive fiber layer is 1 to 4 mm.

[0015] Preferably, the vacuum impregnation time is 24–36 hours; and / or

[0016] The sol-gel reaction is carried out at a temperature of 75–85°C (e.g., 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, or 85°C) for a time of 48–52 h (e.g., 48 h, 49 h, 50 h, 51 h, or 52 h).

[0017] Preferably, the carbonization process involves heating the temperature to 800–1000°C at a rate of 2°C / min in a protective atmosphere and holding the temperature for 2–3 hours.

[0018] In a second aspect, the present invention provides a non-ablative directional thermally conductive composite material, which is prepared using the preparation method described in the first aspect.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects.

[0020] This invention involves impregnating a precursor solution with phenolic aerogel and a directional thermally conductive framework material comprising alternating layers of insulating and conductive fibers. The mixture is then carbonized to introduce carbon aerogel into the directional thermally conductive framework material, resulting in a non-ablative directional thermally conductive composite material with both insulating and conductive layers. This composite material exhibits thermal insulation along the vertical in-plane direction and high thermal conductivity along the in-plane direction. It can rapidly dissipate locally generated high temperatures to other low-temperature areas, achieving heat homogenization and effectively preventing excessively high local temperatures. This improves the material's operating temperature and significantly enhances the thermal insulation efficiency of thermal protection materials. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a physical image of the non-ablative directional thermally conductive composite material provided by the present invention;

[0023] Figure 2 These are infrared images of the non-ablative directional thermally conductive composite material provided in Embodiments 1-4 and Comparative Example 1 of the present invention;

[0024] Figure 3 These are infrared images of the non-ablative directional thermally conductive composite materials provided in Comparative Examples 2-6 of this invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] The present invention provides a method for preparing a non-ablative directional thermally conductive composite material in a first aspect, the method comprising the following steps:

[0027] S1. Mix phenolic resin, catalyst and solvent to obtain precursor solution;

[0028] S2. The directional thermally conductive framework material is placed in a precursor solution and subjected to vacuum impregnation, sol-gel reaction, drying, and carbonization to obtain the non-ablative directional thermally conductive composite material.

[0029] The directional heat-conducting skeleton material consists of at least one alternating layer of heat-insulating fiber and one layer of heat-conducting fiber.

[0030] This invention involves impregnating a precursor solution with phenolic aerogel and a directional thermally conductive framework material comprising alternating layers of insulating and conductive fibers. The mixture is then carbonized to introduce carbon aerogel into the directional thermally conductive framework material, resulting in a non-ablative directional thermally conductive composite material with both insulating and conductive layers. This composite material exhibits thermal insulation along the vertical in-plane direction and high thermal conductivity along the in-plane direction. It can rapidly dissipate locally generated high temperatures to other low-temperature areas, achieving heat homogenization and effectively preventing excessively high local temperatures. This improves the material's operating temperature and significantly enhances the thermal insulation efficiency of thermal protection materials.

[0031] Carbon aerogels are excellent high-temperature insulation materials for aerospace applications due to their advantages of resistance to ultra-high temperatures and low radiation thermal conductivity, which can withstand temperatures up to 3000°C in an oxygen-free environment. However, carbon aerogels have low strength and are brittle, making them difficult to withstand the complex and harsh thermal environments such as strong vibrations and rapid thermal shocks of new hypersonic aircraft. Therefore, this invention introduces carbon aerogels into a directional thermally conductive skeleton material comprising alternating layers of insulating and conductive fibers to improve the strength of the aerogel material.

[0032] According to some preferred embodiments, the phenolic resin and catalyst account for 15-25% of the mass of the precursor solution (e.g., 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%); preferably, the phenolic resin is a thermosetting phenolic resin; the thermosetting phenolic resin used in this invention is THC-800 from Shaanxi Taihang Fire Retardant Polymer Co., Ltd., but is not limited to this model, other thermosetting phenolic resins may also be used; the catalyst is hexamethylenetetramine.

[0033] The mass ratio of the phenolic resin to the catalyst is (5-8):1 (for example, it can be 5:1, 6:1, 7:1 or 8:1);

[0034] The inventors discovered that when the total content of reactants (phenolic resin and catalyst) is less than 15%, for example, 10%, although a three-dimensional network structure of beaded chains is formed after carbonization, the particle size is large and uneven, and many large pores exist inside the aerogel. As the mass fraction of reactants in the aerogel increases, the particle size and pore size of both phenolic aerogel and carbon aerogel decrease significantly. When the mass fraction of reactants is too high (greater than 25%), due to the limited solubility of ethanol, the phenolic resin cannot react completely with hexamethylenetetramine, thus forming a solid precipitate. The cross-linking of the three-dimensional network structure is poor, the sample surface is smooth and glossy, and the density is high. Controlling the mass fraction of reactants to 15-25% allows for the formation of a complete three-dimensional network structure, which can be dried at normal pressure to form an aerogel with a certain strength.

[0035] The inventors discovered that as the catalyst content (mass ratio of catalyst to phenolic resin) decreases, both the particle size and pore size of the aerogel gradually decrease. This is because hexamethylenetetramine (HMTA) acts as both a catalyst and a cross-linking agent in the reaction. HMTA's catalytic effect causes the phenolic resin to continuously aggregate, forming oligomer clusters, while HMTA's cross-linking effect causes the oligomers to interlock and form chain-like structures. When the HMTA content is relatively high, the clusters and oligomer chains continue to grow while overlapping and agglomerating, reaching a critical point of compatibility with the solvent, and the diameter continues to increase until spinomeric phase separation occurs. When the HMTA content is relatively low, the catalytic effect promoting polymer particle growth is relatively weak, but cross-linking still occurs, resulting in tightly bound oligomers and polymers. The aerogel pore size and particle size decrease, but the chain length increases. As the catalyst content decreases, the linear shrinkage during the drying process of the phenolic aerogel initially increases and then decreases, while the linear shrinkage rate increases during the carbonization process. When the linear shrinkage rate is too high, the aerogel is prone to cracking. Therefore, by controlling the catalyst content (mass ratio of catalyst to phenolic resin) within the above-mentioned range, the present invention can ensure the production of phenolic aerogels and carbon aerogels with superior structure and performance.

[0036] According to some preferred embodiments, the directional thermal conductive skeleton material is obtained by integral curing and heat treatment of alternating layers of thermally insulating fiber and thermally conductive fiber; preferably, the curing temperature is 150-160°C and the time is 1-1.5h; the heat treatment is carried out in an argon atmosphere, with the temperature increased to 1000°C at a heating rate of 2°C / min and held for 2h; the argon flow rate is 100mL / min.

[0037] Preferably, the directional thermal conductive skeleton material has one more thermal insulation fiber layer than the thermal conductive fiber layer;

[0038] The preparation method of the directional thermally conductive framework material of the present invention is as follows:

[0039] (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained, wherein the mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers; Short-cut high thermal conductivity carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion II is obtained; wherein the mass ratio of high thermal conductivity carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers. The mass of the amide is 5-7% of the mass of the high thermal conductivity carbon fiber; (2) Dispersion I and dispersion II are divided into several portions, and each portion of dispersion I and each portion of dispersion II are poured into the mold alternately until all of dispersion I and dispersion II are poured out. After each portion of dispersion I or dispersion II is poured out, it is filtered once. Finally, it is cured at 150-160℃ for 1-1.5h. Under argon atmosphere, the temperature is raised to 1000℃ at a heating rate of 2℃ / min and kept at the temperature for 2h. The argon flow rate is 100mL / min to obtain the directional thermal conductivity skeleton material.

[0040] According to some preferred embodiments, the heat-insulating fiber layer comprises viscose-based carbon fiber and phenolic resin; preferably, the mass ratio of the viscose-based carbon fiber and phenolic resin is 1:1.

[0041] According to some preferred embodiments, the thermally conductive fiber layer comprises highly thermally conductive carbon fibers and phenolic resin; preferably, the mass ratio of the highly thermally conductive carbon fibers to the phenolic resin is 1:1.

[0042] According to some preferred embodiments, the number of thermally conductive fiber layers in the directional thermally conductive skeleton material is 1 to 4 (e.g., 1, 2, 3 or more); preferably, the thickness of a single thermally conductive fiber layer is 1 to 4 mm (e.g., 1 mm, 2 mm, 3 mm or 4 mm).

[0043] The present invention comprises a non-ablative directional thermally conductive composite material containing carbon aerogel, which exhibits significantly higher thermal conductivity in the XY and Z directions than the composite material without thermally conductive fiber layers (0 layers). At room temperature, the difference in thermal conductivity between the XY and Z directions increases exponentially with the increase of the number of high thermally conductive fiber layers (1 to 4 layers), indicating that the thermal management performance of the non-ablative directional thermally conductive composite material containing carbon aerogel is better with the increase of the number of thermally conductive fiber layers, exhibiting better in-plane thermal conductivity and vertical in-plane thermal insulation.

[0044] According to some preferred embodiments, the vacuum impregnation time is 24–36 hours (e.g., 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, or 36 hours); and / or

[0045] The sol-gel reaction is carried out at a temperature of 75–85°C (for example, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, or 85°C) for a time of 48–52 h.

[0046] According to some preferred embodiments, the carbonization process involves heating the temperature to 800–1000°C (e.g., 800°C, 850°C, 900°C, 950°C, or 1000°C) at a rate of 2°C / min in a protective atmosphere and holding at that temperature for 2–3 hours. The inventors have found that when the carbonization temperature is too high (e.g., 1200°C and above), the aerogel micropores begin to close.

[0047] In a second aspect, the present invention provides a non-ablative directional thermally conductive composite material, which is prepared using the preparation method described in the first aspect.

[0048] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below in conjunction with embodiments.

[0049] The materials and reagents used in this invention can be purchased directly from the market or synthesized in-house, and there are no restrictions on the specific models.

[0050] Example 1

[0051] S1. Place the thermosetting phenolic resin in a beaker containing anhydrous ethanol, seal it with plastic wrap, place it on a magnetic stirrer, and stir at 80°C until the phenolic resin is completely dissolved. Then add hexamethylenetetramine and wait for it to completely dissolve to obtain a precursor solution. The thermosetting phenolic resin and hexamethylenetetramine account for 15% of the mass of the precursor solution, and the mass ratio of thermosetting phenolic resin to hexamethylenetetramine is 7:1.

[0052] S2. The directional thermally conductive framework material is placed in a precursor solution for vacuum impregnation, kept at 80℃ for 48h for sol-gel reaction, dried under normal pressure, and carbonized at 1000℃ for 2h to obtain a non-ablative directional thermally conductive composite material. The directional thermally conductive framework material includes two alternately distributed thermal insulation fiber layers and one thermally conductive fiber layer, with a thickness of 1mm for each thermally conductive fiber layer. The total thickness of the directional thermally conductive framework material is 15mm.

[0053] The performance data of the non-ablative directional thermally conductive composite material prepared in Example 1 are shown in Table 1.

[0054] Example 2

[0055] S1. Place the thermosetting phenolic resin in a beaker containing anhydrous ethanol, seal it with plastic wrap, place it on a magnetic stirrer, and stir at 80°C until the phenolic resin is completely dissolved. Then add hexamethylenetetramine and wait for it to completely dissolve to obtain a precursor solution. The thermosetting phenolic resin and hexamethylenetetramine account for 15% of the mass of the precursor solution, and the mass ratio of thermosetting phenolic resin to hexamethylenetetramine is 7:1.

[0056] S2. The directional thermally conductive framework material is placed in a precursor solution for vacuum impregnation, kept at 80℃ for 48h for sol-gel reaction, dried under normal pressure, and carbonized at 1000℃ for 2h to obtain a non-ablative directional thermally conductive composite material. The directional thermally conductive framework material includes three alternately distributed thermal insulation fiber layers and two thermally conductive fiber layers, with a single thermally conductive fiber layer thickness of 1mm. The total thickness of the directional thermally conductive framework material is 15mm.

[0057] The performance data of the non-ablative directional thermally conductive composite material prepared in Example 2 are shown in Table 1.

[0058] Example 3

[0059] S1. Place the thermosetting phenolic resin in a beaker containing anhydrous ethanol, seal it with plastic wrap, place it on a magnetic stirrer, and stir at 80°C until the phenolic resin is completely dissolved. Then add hexamethylenetetramine and wait for it to completely dissolve to obtain a precursor solution. The thermosetting phenolic resin and hexamethylenetetramine account for 15% of the mass of the precursor solution, and the mass ratio of thermosetting phenolic resin to hexamethylenetetramine is 7:1.

[0060] S2. The directional thermally conductive framework material is placed in a precursor solution for vacuum impregnation, kept at 80℃ for 48h for sol-gel reaction, dried under normal pressure, and carbonized at 1000℃ for 2h to obtain a non-ablative directional thermally conductive composite material. The directional thermally conductive framework material includes 4 layers of thermally insulating fiber and 3 layers of thermally conductive fiber, with a thickness of 1mm for each thermally conductive fiber layer. The total thickness of the directional thermally conductive framework material is 15mm.

[0061] The performance data of the non-ablative directional thermally conductive composite material prepared in Example 3 are shown in Table 1.

[0062] Example 4

[0063] S1. Place the thermosetting phenolic resin in a beaker containing anhydrous ethanol, seal it with plastic wrap, place it on a magnetic stirrer, and stir at 80°C until the phenolic resin is completely dissolved. Then add hexamethylenetetramine and wait for it to completely dissolve to obtain a precursor solution. The thermosetting phenolic resin and hexamethylenetetramine account for 15% of the mass of the precursor solution, and the mass ratio of thermosetting phenolic resin to hexamethylenetetramine is 7:1.

[0064] S2. The directional thermally conductive framework material is placed in a precursor solution for vacuum impregnation, kept at 80℃ for 48h for sol-gel reaction, dried under normal pressure, and carbonized at 1000℃ for 2h to obtain a non-ablative directional thermally conductive composite material. The directional thermally conductive framework material includes 5 layers of heat-insulating fiber and 4 layers of heat-conducting fiber, with a thickness of 1mm for each heat-conducting fiber layer. The total thickness of the directional thermally conductive framework material is 15mm.

[0065] The performance data of the non-ablative directional thermally conductive composite material prepared in Example 4 are shown in Table 1.

[0066] Comparative Example 1

[0067] S1. Place the thermosetting phenolic resin in a beaker containing anhydrous ethanol, seal it with plastic wrap, place it on a magnetic stirrer, and stir at 80°C until the phenolic resin is completely dissolved. Then add hexamethylenetetramine and wait for it to completely dissolve to obtain a precursor solution. The thermosetting phenolic resin and hexamethylenetetramine account for 15% of the mass of the precursor solution, and the mass ratio of thermosetting phenolic resin to hexamethylenetetramine is 7:1.

[0068] S2. The directional thermally conductive skeleton material is placed in a precursor solution for vacuum impregnation, kept at 80℃ for 48h for sol-gel reaction, dried under normal pressure, and carbonized at 1000℃ for 2h to obtain a non-ablative directional thermally conductive composite material, wherein the directional thermally conductive skeleton material is a 15mm thick heat-insulating fiber layer.

[0069] The performance data of the non-ablative directional thermally conductive composite material prepared in Comparative Example 1 are shown in Table 1.

[0070] Comparative Example 2

[0071] (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added in sequence. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained. The mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers. (2) Dispersion I is poured into a mold, filtered by pressure, and finally cured at 150°C for 1 hour. Under an argon atmosphere, the temperature is raised to 1000°C at a heating rate of 2°C / min and held for 2 hours. The argon flow rate is 100 mL / min, and a directional thermally conductive skeleton material with a total thickness of 15 mm is obtained.

[0072] The performance data of the non-ablative directional thermally conductive composite material prepared in Comparative Example 2 are shown in Table 1.

[0073] Comparative Example 3

[0074] (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained, wherein the mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers; Short-cut high thermal conductivity carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion II is obtained; wherein the mass ratio of high thermal conductivity carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of high thermal conductivity carbon fibers. (2) Divide dispersion I into two equal parts and dispersion II into one equal part. Pour the three parts of dispersion I and the two parts of dispersion II into the mold alternately until all of dispersion I and dispersion II are poured out. After each part of dispersion I or dispersion II is poured out, perform a pressure filter. Finally, solidify at 150°C for 1 hour. Under an argon atmosphere, raise the temperature to 1000°C at a heating rate of 2°C / min and keep it at that temperature for 2 hours. The argon flow rate is 100 mL / min. Two layers of heat-insulating fiber and one layer of heat-conducting fiber are alternately distributed. The thickness of a single layer of heat-conducting fiber is 1 mm, and the total thickness is 15 mm.

[0075] The performance data of the non-ablative directional thermally conductive composite material prepared in Comparative Example 3 are shown in Table 1.

[0076] Comparative Example 4

[0077] (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained, wherein the mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers; Short-cut high thermal conductivity carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion II is obtained; wherein the mass ratio of high thermal conductivity carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of high thermal conductivity carbon fibers. (2) Divide dispersion I into 3 equal parts and dispersion II into 2 equal parts. Pour the three parts of dispersion I and the two parts of dispersion II into the mold alternately until all of dispersion I and dispersion II are poured out. After each part of dispersion I or dispersion II is poured out, perform a pressure filter. Finally, solidify at 150°C for 1 hour. Under an argon atmosphere, raise the temperature to 1000°C at a heating rate of 2°C / min and keep it at that temperature for 2 hours. The argon flow rate is 100 mL / min. This yields a directional thermal conductive skeleton material with 3 layers of heat insulation fiber and 2 layers of heat conduction fiber, with a single layer of heat conduction fiber having a thickness of 1 mm and a total thickness of 15 mm.

[0078] The performance data of the non-ablative directional thermally conductive composite material prepared in Comparative Example 4 are shown in Table 1.

[0079] Comparative Example 5

[0080] (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained, wherein the mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers; Short-cut high thermal conductivity carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion II is obtained; wherein the mass ratio of high thermal conductivity carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of high thermal conductivity carbon fibers. (2) Divide dispersion I into 4 equal parts and dispersion II into 3 equal parts. Pour the three parts of dispersion I and the two parts of dispersion II into the mold alternately until all of dispersion I and dispersion II are poured out. After each part of dispersion I or dispersion II is poured out, perform a pressure filtration. Finally, solidify at 150°C for 1 hour. Under an argon atmosphere, raise the temperature to 1000°C at a heating rate of 2°C / min and keep it at that temperature for 2 hours. The argon flow rate is 100 mL / min. This yields a directional thermal conductive skeleton material with 4 layers of heat-insulating fiber and 3 layers of heat-conducting fiber, with a single layer of heat-conducting fiber having a thickness of 1 mm and a total thickness of 15 mm.

[0081] The performance data of the non-ablative directional thermally conductive composite material prepared in Comparative Example 5 are shown in Table 1.

[0082] Comparative Example 6

[0083] (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained, wherein the mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers; Short-cut high thermal conductivity carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion II is obtained; wherein the mass ratio of high thermal conductivity carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of high thermal conductivity carbon fibers. (2) Divide dispersion I into 5 equal parts and dispersion II into 4 equal parts. Pour three parts of dispersion I and two parts of dispersion II into the mold in turn until all dispersion I and dispersion II are poured out. After each part of dispersion I or dispersion II is poured out, perform a pressure filter. Finally, solidify at 150°C for 1 hour. Under an argon atmosphere, raise the temperature to 1000°C at a heating rate of 2°C / min and keep it at that temperature for 2 hours. The argon flow rate is 100 mL / min. This yields 5 layers of heat-insulating fiber and 4 layers of heat-conducting fiber with alternating distribution. The thickness of a single heat-conducting fiber layer is 1 mm, and the total thickness is 15 mm.

[0084] The performance data of the non-ablative directional thermally conductive composite material prepared in Comparative Example 6 are shown in Table 1.

[0085] Table 1

[0086]

[0087] It should be noted that the thermal conductivity difference multiple in the table refers to the thermal conductivity difference multiple between the XY direction and the Z direction; the directional thermal conduction skeleton materials in Examples 1-4 were prepared by the methods of Comparative Examples 3-6, and the directional thermal conduction skeleton materials in Comparative Example 1 were prepared by the method of Comparative Example 2.

[0088] As shown in Table 1, in Examples 1-4, the thermal conductivity of the non-ablative directional thermally conductive composite material in the XY plane increases with the increase of the number of thermally conductive fiber layers. The addition of thermally conductive fiber layers has a significant effect on improving the thermal conductivity of the non-ablative directional thermally conductive composite material in the XY plane. At room temperature, the greater the difference in thermal conductivity between the composite material in the XY and Z directions with the increase of the number of high thermally conductive fiber layers, the better the thermal management performance of the composite material in terms of in-plane thermal conductivity and vertical plane insulation. After impregnation with aerogel, the difference in thermal conductivity between the composite material in the XY and Z directions increases rapidly, and the rate of increase is much greater than before aerogel impregnation. This indicates that aerogel impregnation greatly improves the thermal conductivity of the material in the XY direction, which helps to improve the thermal management capability of the composite material. At room temperature, the greater the difference in thermal conductivity between the composite material in the XY and Z directions with the increase of the number of high thermally conductive fiber layers, the better the thermal management performance of the composite material in terms of in-plane thermal conductivity and vertical plane insulation. Furthermore, after carbon aerogel composite, the compressive strength and compressive modulus of the material are significantly improved, indicating that carbon aerogel composite can effectively improve the mechanical properties of composite materials.

[0089] Example 5

[0090] S1. Place the thermosetting phenolic resin in a beaker containing anhydrous ethanol, seal it with plastic wrap, place it on a magnetic stirrer, and stir at 80°C until the phenolic resin is completely dissolved. Then add hexamethylenetetramine and wait for it to completely dissolve to obtain a precursor solution. The thermosetting phenolic resin and hexamethylenetetramine account for 15% of the mass of the precursor solution, and the mass ratio of thermosetting phenolic resin to hexamethylenetetramine is 7:1.

[0091] S2. The directional thermally conductive framework material is placed in a precursor solution for vacuum impregnation, kept at 80℃ for 48h for sol-gel reaction, dried under normal pressure, and carbonized at 1000℃ for 2h to obtain a non-ablative directional thermally conductive composite material. The directional thermally conductive framework material includes two alternately distributed layers of thermal insulation fiber and one layer of thermally conductive fiber, with the thermally conductive fiber layer having a thickness of 3mm. The total thickness of the directional thermally conductive framework material is 15mm.

[0092] The performance data of the non-ablative directional thermally conductive composite material prepared in Example 5 are shown in Table 2.

[0093] Comparative Example 7

[0094] (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained. The mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers. Short-cut high thermal conductivity carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added sequentially. After being dispersed evenly by a mechanical stirrer, dispersion II is obtained. The mass ratio of high thermal conductivity carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of high thermal conductivity carbon fibers.

[0095] (2) Divide dispersion I into two equal parts. Pour dispersion I and dispersion II into the mold alternately until all dispersion I and dispersion II are poured out. After each part of dispersion I or dispersion II is poured out, perform a pressure filtration. Finally, solidify at 150°C for 1 hour. Under an argon atmosphere, raise the temperature to 1000°C at a heating rate of 2°C / min and keep it at that temperature for 2 hours. The argon flow rate is 100 mL / min. This yields two layers of heat-insulating fiber and one layer of heat-conducting fiber, with a single layer of heat-conducting fiber having a thickness of 3 mm and a total thickness of 15 mm, forming a directional heat-conducting skeleton material.

[0096] The performance data of the non-ablative directional thermally conductive composite material prepared in Comparative Example 7 are shown in Table 2.

[0097] Table 2

[0098]

[0099] It should be noted that the directional thermal conduction skeleton material in Example 5 was prepared using the method of Comparative Example 6.

[0100] As shown in Table 2, compared with the directional thermally conductive skeleton material (Comparative Example 7), the non-ablative directional thermally conductive composite material (Example 5) after composite carbon aerogel has increased compressive strength in the XY and Z directions by 116.4% and 196.3%, respectively, and compressive modulus by 91.0% and 15.5%, respectively. This is because the carbon aerogel fills the pores between the fibers, providing resistance to fiber bending and breakage or elastic bending / rotation.

[0101] This invention uses an electric heating stage to simultaneously heat the sample at a temperature of 100°C in the XY direction, obtaining an infrared image. Figure 2It can be seen that in the oriented thermally conductive skeleton material containing thermally conductive fiber layers, the thermally conductive fiber layers exhibit a faster heating trend, and their surface temperature remains higher than that of the oriented thermally conductive skeleton material without thermally conductive fiber layers. It should be noted that under the same heating conditions, a higher surface temperature implies stronger heat transfer capacity, indicating that the thermally conductive fiber layers have better thermal management capabilities. As the number of thermally conductive fiber layers increases, the thermally conductive fiber layers heat up faster. After heating for 500 seconds, the temperature of the thermally conductive fiber layers in Comparative Example 6 (with 4 layers of thermally conductive fiber) reached 62.5℃, while the highest temperature of the thermally insulating fiber layer in Comparative Example 2 (without thermally conductive fiber layers) was only 44.3℃. Figure 3 It can be seen that the temperature changes of the thermally conductive fiber layer and the thermally insulating fiber layer are significant. As the heating time increases, the temperature difference between the two becomes more and more obvious. After heating for 500 seconds, in Example 4, the temperature of the non-ablative directional thermally conductive composite material with 4 layers of thermally conductive fiber added can reach a maximum of 85°C, while the temperature of the thermally insulating fiber layer is only 45°C. This indicates that after the composite carbon aerogel, the addition of the thermally conductive fiber layer significantly improves the thermal conductivity of the composite material in the XY direction. It should be noted that the XY direction in this invention is the in-plane direction, and the Z direction is the perpendicular in-plane direction.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a non-ablative directional thermally conductive composite material, characterized in that, The preparation method includes the following steps: S1. Phenolic resin, catalyst and solvent are mixed to obtain a precursor solution; the phenolic resin and catalyst account for 15-25% of the mass of the precursor solution; the phenolic resin is a thermosetting phenolic resin; the catalyst is hexamethylenetetramine; the mass ratio of phenolic resin to catalyst is (5-8):

1. S2. The directional thermally conductive framework material is placed in a precursor solution and subjected to vacuum impregnation, sol-gel reaction, drying, and carbonization to obtain the non-ablative directional thermally conductive composite material. The directional heat-conducting skeleton material is composed of at least one alternating layer of heat-insulating fiber and one layer of heat-conducting fiber; the directional heat-conducting skeleton material has one more layer of heat-insulating fiber than the heat-conducting fiber. The preparation method of the directional thermally conductive framework material is as follows: (1) Short-cut viscose-based carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added in sequence. After being dispersed evenly by a mechanical stirrer, dispersion I is obtained. The mass ratio of viscose-based carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of viscose-based carbon fibers. Short-cut high thermal conductivity carbon fibers with a length of 1-3 mm are dispersed in water, and phenolic resin and polyacrylamide are added in sequence. After being dispersed evenly by a mechanical stirrer, dispersion II is obtained. The mass ratio of high thermal conductivity carbon fibers to phenolic resin is 1:1, and the mass of polyacrylamide is 5-7% of the mass of high thermal conductivity carbon fibers. (2) Divide dispersion I and dispersion II into several equal portions. Pour each portion of dispersion I and each portion of dispersion II into the mold alternately until all of dispersion I and dispersion II are poured out. After each portion of dispersion I or dispersion II is poured out, perform a pressure filtration. Finally, solidify at 150~160℃ for 1~1.5h. Under an argon atmosphere, raise the temperature to 1000℃ at a heating rate of 2℃ / min and hold for 2h. The argon flow rate is 100mL / min to obtain the directional thermal conductive skeleton material.

2. The preparation method according to claim 1, characterized in that, The number of thermally conductive fiber layers in the directional thermally conductive skeleton material is 1 to 4.

3. The preparation method according to claim 2, characterized in that, The thickness of a single thermally conductive fiber layer is 1~4mm.

4. The preparation method according to claim 1, characterized in that, The vacuum impregnation time is 24~36 hours.

5. The preparation method according to claim 1, characterized in that, The sol-gel reaction is carried out at a temperature of 75-85°C for 48-52 hours.

6. The preparation method according to claim 1, characterized in that, The carbonization process involves heating the temperature to 800-1000°C at a rate of 2°C / min in a protective atmosphere and holding it at that temperature for 2-3 hours.

7. A non-ablative directional thermally conductive composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

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