A fungal dendritic heterogeneous structure heat-conducting filler, a preparation method thereof and a preparation method of a heat-conducting composite material

Abstract

The application discloses a fungal dendritic heterogeneous structure heat-conducting filler and a preparation method thereof and a preparation method of a heat-conducting composite material, and the preparation method of the fungal dendritic heterogeneous structure heat-conducting filler comprises the following steps: dissolving melamine in ethylene glycol to form a saturated solution, continuously adding the melamine into the saturated solution and uniformly dispersing, adding an aqueous nitric acid solution, mixing to form white flocculation, washing the white flocculation with anhydrous ethanol, and obtaining white precipitate through centrifugation; drying the white precipitate to obtain white powder, and calcining the white powder at high temperature to obtain the fungal dendritic heterogeneous structure heat-conducting filler. The fungal dendritic heterogeneous structure heat-conducting filler, the preparation method thereof and the preparation method of the heat-conducting composite material are characterized in that a fungal dendritic heterogeneous structure heat-conducting filler is synthesized, and a covalent action is formed between the filler, so that the heat transfer performance between carbon nitride nanotubes and carbon nitride nanosheets is enhanced, and the heat-conducting performance of a polyimide-based polymer composite material is significantly improved at a low filler content.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-conducting polymer composites, and particularly relates to a fungal dendritic heterogeneous structure heat-conducting filler, a preparation method thereof and a preparation method of a heat-conducting composite material. BACKGROUND

[0002] With the rapid development of science and technology, the demand for electronic devices has also shown diversification, further promoting the development of microelectronic devices towards miniaturization and high integration, which inevitably leads to the problem of local heat accumulation caused by the increase in power density and integrated circuit dense packaging. If there is no effective heat dissipation, the generated heat will accumulate to cause the temperature of the device to rise, thereby affecting the service life and stability. Polymer-based composites have become the best choice for heat management materials in electronic components due to their high thermal conductivity.

[0003] The structural design of the heat-conducting filler is an effective means to regulate the interfacial thermal resistance between the fillers. It is still challenging to further improve the thermal conductivity of the polymer composite while maintaining the excellent comprehensive performance of the polymer composite. In the current research, advanced structural design of the heat-conducting filler is considered as a key approach to reduce the interfacial thermal resistance of the filler / matrix interface, establish a continuous heat transport path and efficiently and quickly transport phonons. For a composite material containing multiple fillers, heat-conducting fillers with high aspect ratio can serve as a bridge connecting two-dimensional fillers, which can improve the continuity of phonon transport and increase the number of phonon transport paths. How to further improve the thermal conductivity of the polymer-based composite through the structural design of the heat-conducting filler is the focus of current research. SUMMARY

[0004] Based on the problems existing in the prior art, the present application provides a fungal dendritic heterogeneous structure heat-conducting filler, a preparation method thereof and a preparation method of a heat-conducting composite material, aiming to improve the interfacial thermal resistance between the fillers and obtain a polyimide (PI) -based composite material with good thermal conductivity.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of a fungal dendritic heterogeneous structure heat-conducting filler, which comprises the following steps:

[0006] Firstly, melamine is used as raw material, and a saturated solution is formed after being dissolved in ethylene glycol, then melamine is continuously added to the saturated solution, and then nitric acid aqueous solution is added dropwise, and white flocculent substances are formed after mixing;

[0007] Then, the white flocculent substances are washed with anhydrous ethanol and centrifuged to obtain white flocculent precipitate, and the white flocculent precipitate is dried at 50-70 DEG C for 3-6h to obtain white powder;

[0008] Finally, the white powder is heated to 350-450℃ in a muffle furnace and kept for 0.5-3h, and finally the fungal dendritic heterogeneous structure heat-conducting filler is obtained.

[0009] The amounts of the components are as follows: 0.34g of melamine for preparing a saturated solution, 0.11g of melamine for adding again in the saturated solution, 60ml of 0.12M nitric acid solution, and 20ml of ethylene glycol as a reference.

[0010] As a further preferred technical solution of the present application, the melamine is continuously added in the saturated solution by ultrasonic stirring at a speed of 300-500rpm for 10-30min.

[0011] As a further preferred technical solution of the present application, the nitric acid solution is added dropwise at a rate of 10ml / min.

[0012] As a further preferred technical solution of the present application, the white powder is calcined at high temperature in a muffle furnace, and the temperature is increased to 400℃ at a rate of 10℃ / min and kept for 1h.

[0013] According to another aspect of the present application, the present application further provides a fungal dendritic heterogeneous structure heat-conducting filler prepared by the above method.

[0014] According to another aspect of the present application, the present application further provides a preparation method of a heat-conducting composite material based on the fungal dendritic heterogeneous structure heat-conducting filler, which comprises the following steps:

[0015] S1, 4, 4'-diamino diphenyl ether (ODA) is dissolved in N, N-dimethylacetamide (DMAc), then 1, 2, 4, 5-pyromellitic dianhydride (PMDA) is added and stirred uniformly, and then an excess of deionized water is added to obtain a light yellow precipitate, which is filtered, washed and dried to obtain a solid polyamide acid (PAA); the solid polyamide acid and triethylamine (TEA) are mixed in deionized water, stirred at room temperature to obtain a water-soluble PAA solution, and the fungal dendritic heterogeneous structure heat-conducting filler is added to the water-soluble polyamide acid solution and dispersed uniformly to form a dispersion;

[0016] S2, the dispersion is poured into a mold with polytetrafluoroethylene as the inner wall and copper sheet as the bottom, the growth direction of ice crystals is controlled by immersing the bottom end of the mold in liquid nitrogen, and then freeze-drying is performed to obtain an aerogel with a three-dimensional skeleton structure;

[0017] S3, the aerogel is subjected to hot pressing treatment to obtain a heat-conducting composite material.

[0018] As a further preferred technical solution of the present application, the component allocation of the preparation of the solid polyamic acid is: 4,4'-oxydianiline is 0.5g, N,N-dimethylacetamide is 5.9g, and pyromellitic dianhydride is 0.545g.

[0019] As a further preferred technical solution of the present application, the component allocation of the preparation of the solid polyamic acid is: 4,4'-oxydianiline is 0.5g, N,N-dimethylacetamide is 5.9g, and pyromellitic dianhydride is 0.545g.

[0020] As a further preferred technical solution of the present application, the component allocation of the preparation of the solid polyamic acid is: 4,4'-oxydianiline is 0.5g, N,N-dimethylacetamide is 5.9g, and pyromellitic dianhydride is 0.545g.

[0021] As a further preferred technical solution of the present application, the component allocation of the preparation of the solid polyamic acid is: 4,4'-oxydianiline is 0.5g, N,N-dimethylacetamide is 5.9g, and pyromellitic dianhydride is 0.545g.

[0022] As a further preferred technical solution of the present application, the component allocation of the preparation of the solid polyamic acid is: 4,4'-oxydianiline is 0.5g, N,N-dimethylacetamide is 5.9g, and pyromellitic dianhydride is 0.545g.

[0023] The fungus-like dendritic heterostructure heat-conducting filler of the present application has the following beneficial effects:

[0024] 1) The method of the present application promotes the growth of two-dimensional carbon nitride nanosheets on one-dimensional carbon nitride nanotubes to form a fungus-like dendritic heterostructure through covalent action, thereby enhancing the heat transfer performance between the carbon nitride nanotubes and the carbon nitride nanosheets, and significantly improving the thermal conductivity of the polyimide-based polymer composite at a low filler content;

[0025] 2) The fungus-like dendritic heterostructure heat-conducting filler of the present application reduces the interfacial thermal resistance between the filler and the matrix through the rich active groups on the surfaces of the CNNs and the CNNTs;

[0026] 3) When the fungus-like dendritic heterostructure heat-conducting filler of the present application is applied to an imide-based polymer composite, it can effectively reduce the interfacial thermal resistance between the fillers, establish a continuous heat transfer path, and efficiently and quickly transfer phonons, and through the construction of a three-dimensional skeleton heat-conducting network, it effectively increases the heat conduction path, thereby improving the thermal conductivity of the PI-based polymer composite.

[0027] 4) The fungus-like dendritic heterostructure heat-conducting filler of the present application has a simple preparation process and a high yield of up to 68%. BRIEF DESCRIPTION OF DRAWINGS

[0028] The present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0029] Figure 1Synthesis flowchart of carbon nitride nanosheet@carbon nitride nanotube / polyimide (CNNs@CNNTs / PI) for embodiment 1 of the present application;

[0030] Figure 2 Scanning electron microscope image of CNNs@CNNTs obtained in embodiment 1 of the present application;

[0031] Figure 3 Transmission electron microscope image of CNNs@CNNTs obtained in embodiment 1 of the present application;

[0032] Figure 4 Scanning electron microscope image of CNNs@CNNTs / PAA three-dimensional skeleton obtained in embodiment 1 of the present application;

[0033] Figure 5 Thermal conductivity test results of the composite materials obtained in each embodiment and the comparative example of embodiment 1 of the present application.

[0034] The purposes, functional features and advantages of the present application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0035] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0036] Unless defined, the technical terms used in the following embodiments have the same meanings as generally understood by those skilled in the art to which the present application belongs. The test reagents used in the following embodiments are conventional biochemical reagents unless otherwise specified; and the experimental methods described are conventional methods unless otherwise specified.

[0037] Embodiment 1

[0038] The preparation method of the heat-conducting composite material based on the fungal dendritic heterogeneous structure heat-conducting filler provided in the present embodiment (see Figure 1 ) is specifically prepared as follows to obtain a 10wt% CNNs@CNNTs / PI composite material.

[0039] Step 1, synthesis of CNNs@CNNTs

[0040] First, 0.34g of melamine was dissolved in 20ml of ethylene glycol at room temperature to form a saturated solution, 0.11g of melamine was added to the saturated solution, and ultrasonic stirring was performed for 30min to disperse it, 60ml of 0.12M nitric acid aqueous solution was added to the solution at a dropping rate of 10ml / min under 500rpm to obtain a white flocculent precipitate, which was washed with anhydrous ethanol by ultrasonic washing for 3 times and centrifuged to obtain a white precipitate, which was dried at 60℃ for 5h to obtain a white powder.

[0041] Secondly, the white powder was heated to 350℃ at a heating rate of 10℃ / min in a muffle furnace and kept for 1h, and finally a fungal dendritic heterogeneous structure heat-conducting filler, denoted as CNNs@CNNTs heat-conducting filler (also called CNNs@CNNTs or heat-conducting filler) was obtained.

[0042] Step 2, synthesis of water-soluble PAA

[0043] Firstly, 0.5g of 4,4'-diaminodiphenyl ether (ODA) was dissolved in 5.9g of N,N-dimethylacetamide (DMAC), then 0.545g of pyromellitic dianhydride (PMDA) was added to the mixture, and mechanical stirring was carried out for 5h. After adding excess deionized water to the obtained mixture, the light yellow precipitate was filtered, washed, and dried to obtain a solid polyamic acid;

[0044] Secondly, 1g of solid polyamic acid (PAA) and 0.48g of triethylamine (TEA) were mixed in 23.52mL of deionized water, and stirred at room temperature for 5h to prepare a water-soluble polyamic acid (PAA) solution with a solid content of 4%.

[0045] Step 3, preparation of CNNs@CNNTs / PAA three-dimensional skeleton

[0046] 0.055g of CNNs@CNNTs heat-conducting filler was uniformly dispersed in 12.5g of PAA aqueous solution with a solid content of 4% to obtain a CNNs@CNNTs / PAA dispersion, which was poured into a mold with a polytetrafluoroethylene inner wall and a copper sheet bottom; then the bottom of the mold was immersed in liquid nitrogen, and by controlling the growth direction of ice crystals, the CNNs@CNNTs / PAA formed a three-dimensional oriented structure. The structure after liquid nitrogen freezing was placed in a freeze-drying machine at -50℃ and 25Pa, and freeze-dried for 24h to remove water in the skeleton structure, and finally a CNNs@CNNTs / PAA aerogel with a three-dimensional skeleton structure was obtained.

[0047] Step 4, preparation of CNNs@CNNTs / PI composite material

[0048] The CNNs@CNNTs / PAA aerogel was heat-pressed at 10Mpa, at temperatures of 100℃, 200℃, and 220℃ for 1h each, and finally a CNNs@CNNTs / PI composite material was obtained.

[0049] The scanning electron microscope image of the CNNs@CNNTs heat-conducting filler of Example 1 is as follows: Figure 2As shown in the figure, carbon nitride nanosheets are wrapped on carbon nitride nanotubes to form a fungal dendritic heterostructure, and there is no obvious separation interface between the CNNs and the CNNTs, which is conducive to the effective construction of a multi-level heat conduction path.

[0050] The transmission electron micrograph of the CNNs@CNNTs heat-conducting filler obtained in Example 1 is shown in FIG. 1. Figure 3 As shown in the figure, carbon nitride nanosheets are wrapped on carbon nitride nanotubes to form a fungal dendritic heterostructure, and there is no obvious separation interface between the CNNs and the CNNTs, which is conducive to the effective construction of a multi-level heat conduction path.

[0051] The scanning electron micrograph of the CNNs@CNNTs / PAA aerogel with a three-dimensional skeleton structure obtained in Example 1 is shown in FIG. 2. Figure 4 As shown in the figure, the CNNs@CNNTs are orderly arranged layer by layer to form a long-range ordered orientation structure, which is conducive to the effective construction of a heat conduction path.

[0052] Example 2

[0053] In this example, a 20wt% CNNs@CNNTs / PI composite material was prepared by the same method as in Example 1, except that in step 3: 0.125g of CNNs@CNNTs was uniformly dispersed in 12.5g of a PAA aqueous solution with a solid content of 4% to obtain a CNNs@CNNTs / PAA dispersion, which was poured into a mold with a polytetrafluoroethylene inner wall and a copper sheet bottom; then, the bottom end of the mold was immersed in liquid nitrogen, and by controlling the growth direction of ice crystals, the CNNs@CNNTs / PAA formed a three-dimensional orientation structure, and the structure after being frozen in liquid nitrogen was placed in a freeze-drying machine at-50℃ and 25Pa for 24h to remove water in the skeleton structure, thereby obtaining a CNNs@CNNTs / PAA aerogel.

[0054] Example 3

[0055] The 30wt% CNNs@CNNTs / PI composite material was prepared by the substantially same method as in Example 1, with the only difference being that in step 3: 0.214 g of CNNs@CNNTs was uniformly dispersed in 12.5 g of a PAA aqueous solution with a solid content of 4% to obtain a CNNs@CNNTs / PAA dispersion liquid, which was poured into a mold with a polytetrafluoroethylene inner wall and a copper sheet bottom, then the bottom end of the mold was immersed in liquid nitrogen, and by controlling the ice crystal growth direction, the CNNs@CNNTs / PAA formed a three-dimensional oriented structure, the structure after liquid nitrogen freezing was placed in a freeze dryer at -50°C and 25 Pa, and freeze-dried for 24 h to remove water in the skeleton structure, to obtain a CNNs@CNNTs / PAA aerogel.

[0056] Example 4

[0057] The 40wt% CNNs@CNNTs / PI composite material was prepared by the substantially same method as in Example 1, with the only difference being that in step 3: 0.333 g of CNNs@CNNTs was uniformly dispersed in 12.5 g of a PAA aqueous solution with a solid content of 4% to obtain a CNNs@CNNTs / PAA dispersion liquid, which was poured into a mold with a polytetrafluoroethylene inner wall and a copper sheet bottom; then the bottom end of the mold was immersed in liquid nitrogen, and by controlling the ice crystal growth direction, the CNNs@CNNTs / PAA formed a three-dimensional oriented structure, the structure after liquid nitrogen freezing was placed in a freeze dryer at -50°C and 25 Pa, and freeze-dried for 24 h to remove water in the skeleton structure, to obtain a CNNs@CNNTs / PAA aerogel.

[0058] Comparative Example 1

[0059] As a control experiment of Example 1, the difference is that the CNNs and CNNTs are prepared by a blending method to prepare a CNNs-CNNTs filler. Specifically, a 10wt% CNNs-CNNTs / PI heat-conducting composite material was prepared according to the following steps:

[0060] Step 1, synthesis of CNNs-CNNTs

[0061] First, 0.34 g of melamine was dissolved in 20 ml of ethylene glycol at room temperature to form a saturated solution, which was ultrasonically stirred for 30 min to disperse, and 60 ml of 0.12M nitric acid aqueous solution was added dropwise to the solution at a rate of 5 ml / min at 500 rpm to obtain a white flocculent precipitate, which was washed with water three times and centrifuged to obtain a white precipitate, which was dried at 60°C for 12 h to obtain a white powder, which was heated to 350°C at a rate of 10°C / min in a muffle furnace and kept for 1 h, and finally CNNTs were obtained.

[0062] Secondly, a certain amount of melamine was placed in a dry pot and heated to 550℃ at a rate of 10℃ / min in a muffle furnace and kept for 1h. The obtained yellow block was ground into powder and laid on a ceramic plate and heated to 50℃ at a rate of 10℃ / min in a muffle furnace and kept for 1h. Finally, CNNs were obtained.

[0063] Finally, the CNNTs and the CNNs were mixed in a mass ratio of 1:1 to prepare a CNNs-CNNTs thermal conductive filler.

[0064] Step 2, synthesis of water-soluble PAA

[0065] Firstly, 0.5g of 4,4'-diaminodiphenyl ether (ODA) was dissolved in 5.9g of N,N-dimethylacetamide (DMAC), then 0.545g of pyromellitic dianhydride (PMDA) was added to the mixture, and mechanical stirring was carried out for 5h. After adding excess deionized water to the obtained mixture, the light yellow precipitate was filtered, washed, and dried to obtain a solid polyamic acid;

[0066] Secondly, 1g of solid polyamic acid (PAA) and 0.48g of triethylamine (TEA) were mixed in 23.52mL of deionized water, and stirred at room temperature for 5h to prepare a water-soluble polyamic acid (PAA) solution with a solid content of 4%.

[0067] Step 3, preparation of CNNs-CNNTs / PAA three-dimensional skeleton

[0068] 0.055g of CNNs-CNNTs thermal conductive filler was uniformly dispersed in 12.5g of PAA aqueous solution with a solid content of 4%, to obtain a CNNs-CNNTs / PAA dispersion, which was poured into a mold with a polytetrafluoroethylene inner wall and a copper bottom. Then, the bottom end of the mold was immersed in liquid nitrogen, and by controlling the growth direction of ice crystals, the CNNs-CNNTs / PAA formed a three-dimensional oriented structure. The structure after liquid nitrogen freezing was placed in a freeze-drying machine at -50℃ and 25Pa, and freeze-dried for 24h to remove water in the skeleton structure, to obtain a CNNs-CNNTs / PAA aerogel with a three-dimensional skeleton structure.

[0069] Step 4, preparation of CNNs-CNNTs / PI composite material

[0070] The CNNs-CNNTs / PAA aerogel was heat pressed at 10Mpa, at temperatures of 100℃, 200℃ and 220℃ for 1h each, to finally obtain a CNNs-CNNTs / PI composite material.

[0071] Comparative Example 2

[0072] The comparative example 2 was prepared according to the same method as comparative example 1, except that in step 3, 0.125 g of CNNs-CNNTs was dispersed in 12.5 g of PAA aqueous solution with a solid content of 4% to obtain a CNNs-CNNTs / PAA dispersion, which was poured into a mold with polytetrafluoroethylene as the inner wall and a copper sheet as the bottom. Then, the bottom end of the mold was immersed in liquid nitrogen, and the CNNs-CNNTs / PAA formed a three-dimensional oriented structure by controlling the growth direction of ice crystals. The structure after liquid nitrogen freezing was placed in a freeze dryer at -50°C and 25 Pa, and freeze-dried for 24 h to remove water in the skeleton structure, obtaining a CNNs-CNNTs / PAA aerogel.

[0073] Comparative example 3

[0074] The comparative example 3 was prepared according to the same method as comparative example 1, except that in step 3, 0.214 g of CNNs-CNNTs was dispersed in 12.5 g of PAA aqueous solution with a solid content of 4% to obtain a CNNs-CNNTs / PAA dispersion, which was poured into a mold with polytetrafluoroethylene as the inner wall and a copper sheet as the bottom. Then, the bottom end of the mold was immersed in liquid nitrogen, and the CNNs-CNNTs / PAA formed a three-dimensional oriented structure by controlling the growth direction of ice crystals. The structure after liquid nitrogen freezing was placed in a freeze dryer at -50°C and 25 Pa, and freeze-dried for 24 h to remove water in the skeleton structure, obtaining a CNNs-CNNTs / PAA aerogel.

[0075] Comparative example 4

[0076] The comparative example 4 was prepared according to the same method as comparative example 1, except that in step 3, 0.333 g of CNNs-CNNTs was dispersed in 12.5 g of PAA aqueous solution with a solid content of 4% to obtain a CNNs-CNNTs / PAA dispersion, which was poured into a mold with polytetrafluoroethylene as the inner wall and a copper sheet as the bottom. Then, the bottom end of the mold was immersed in liquid nitrogen, and the CNNs-CNNTs / PAA formed a three-dimensional oriented structure by controlling the growth direction of ice crystals. The structure after liquid nitrogen freezing was placed in a freeze dryer at -50°C and 25 Pa, and freeze-dried for 24 h to remove water in the skeleton structure, obtaining a CNNs-CNNTs / PAA aerogel.

[0077] The thermal diffusivity test results of the heat-conducting composite materials obtained in the above examples and comparative examples are shown in Table 1. Figure 5 Figure 5 ​It can be seen that by realizing the coating of carbon nitride nanosheets on carbon nitride nanotubes to form a fungal dendritic heterostructure, the thermal conductivity of the CNNs@CNNTs / PI composite material is significantly improved compared with that of pure PI and the CNNs-CNNTs / PI composite material.

[0078] Although the specific embodiments of the present application are described above, those skilled in the art should understand that these are only illustrative, and various changes or modifications can be made to the present embodiments without departing from the principles and essence of the present application, and the protection scope of the present application is only defined by the appended claims.

Claims

1. A method for preparing a fungal dendritic heterostructure thermally conductive filler, characterized in that, The method comprises the following steps: Melamine is dissolved in ethylene glycol to form a saturated solution, and then melamine is continuously added to the saturated solution to be uniformly dispersed, and an aqueous nitric acid solution is added, and then white floccules are formed after mixing, and the white floccules are washed with anhydrous ethanol and centrifuged to obtain a white precipitate; the white precipitate is dried to obtain white powder, and the white powder is calcined at high temperature to obtain a fungal dendritic heterogeneous structure heat-conducting filler; The aqueous nitric acid solution is added dropwise at a rate of 10 ml / min; the white powder is calcined at high temperature in a muffle furnace, and the temperature is increased to 350-400 ℃ at a rate of 10 ℃ / min and kept for 0.5-2 h.

2. The method of claim 1, wherein the fungal dendritic heterostructure thermally conductive filler is prepared by the steps of: The amounts of the components are as follows: 0.34 g of melamine is used to prepare a saturated solution based on 20 ml of ethylene glycol, and 0.11 g of melamine is added to the saturated solution, and 60 ml of an aqueous nitric acid solution with a concentration of 0.12 M is used.

3. The method for preparing the fungal dendritic heterostructure thermally conductive filler according to claim 1, characterized in that, When the melamine is continuously added to the saturated solution, ultrasonic stirring is used at a speed of 300-500 rpm for 10-30 min.

4. A fungal dendritic heterostructure thermally conductive filler, characterized in that, The method is prepared by any one of claims 1-3.

5. A method for producing a heat conducting composite material based on the fungal dendritic heterostructure heat conducting filler according to claim 4, characterized in that, The method comprises the following steps: S1, mixing solid polyamic acid and triethylamine in deionized water, stirring at room temperature to obtain a water-soluble polyamic acid solution, adding the fungal dendritic heterogeneous structure heat-conducting filler to the water-soluble polyamic acid solution to disperse uniformly to form a dispersion liquid; S2, pouring the dispersion liquid into a mold with polytetrafluoroethylene as the inner wall and copper sheet as the bottom, controlling the growth direction of ice crystals by immersing the bottom end of the mold in liquid nitrogen, and then freeze-drying to obtain an aerogel with a three-dimensional skeleton structure; S3, the aerogel is treated by hot pressing to obtain a heat-conducting composite material.

6. The method of claim 5, wherein the thermally conductive composite material is prepared by a method comprising: The proportioning ratio of the components for preparing the dispersion liquid is as follows: 0.8 g-1.0 g of solid polyamic acid, 0.48 g of triethylamine, and 18.52 ml-23.52 ml of deionized water.

7. The method of claim 5, wherein the thermally conductive composite material is prepared by a process comprising: The solid content of the water-soluble polyamic acid solution is 4%.

8. The method of claim 5, wherein the thermally conductive composite material is prepared by a process comprising: The hot pressing process is as follows: under a pressure of 10 MPa, the temperature is increased to 100 ℃, 200 ℃ and 220 ℃ respectively, and each temperature is kept for 1 h.

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