Graphite / carbon fiber felt / epoxy composite material with three-dimensional heat conduction network and preparation method thereof

Abstract

The invention relates to the technical field of preparation of heat-conducting epoxy composite materials, in particular to a graphite / carbon fiber felt / epoxy composite material with a three-dimensional heat-conducting network, which is prepared by forming a graphite / carbon fiber felt three-dimensional heat-conducting network by graphite and a carbon fiber surfacing felt and then compounding the graphite / carbon fiber felt three-dimensional heat-conducting network with an epoxy resin matrix. The preparation method disclosed by the invention has the characteristics of simple and convenient process and easiness in operation mastering, and the obtained composite material shows good convenience in the aspect of processing and is relatively low in cost. Experimental results show that the in-plane heat conductivity of the prepared heat-conducting composite material can reach 0.763 W / mK, and compared with a pure epoxy resin matrix, the heat conductivity of the heat-conducting composite material is improved by about 302%, and the heat-conducting composite material shows excellent heat-conducting property.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing thermally conductive epoxy composites, and particularly relates to a graphite / carbon fiber felt / epoxy composite with a three-dimensional thermal conduction network and a preparation method thereof. Background Art

[0002] With the rapid development of the electronics industry, miniaturization, high integration, and high power density have become the main research directions of different electronic components. These characteristics bring more portable and efficient electronic devices, but also bring new thermal challenges. High integration and compact packaging technologies have greatly reduced the available heat dissipation space in electronic devices, resulting in the accumulation of waste heat inside the devices and being unable to be released quickly enough. Excessive temperature will limit the performance and lifespan of electronic devices and affect their normal operation.

[0003] Applying thermal interface materials (TIMs) between heating components and heat sinks for effective heat transfer is considered the most direct method to improve the overall thermal performance of electronic devices. Due to their advantages such as light weight, easy processing, and low cost, polymers are usually selected as the matrix of TIMs in the electronics industry.

[0004] Adding highly thermally conductive fillers to the polymer matrix can effectively improve the thermal conductivity of the polymer. The final performance of the thermally conductive composite is jointly determined by the polymer matrix, thermally conductive fillers, and their microstructure. The processing technology and preparation strategy of the composite are also crucial for improving the thermal conductivity.

[0005] The construction of a three-dimensional continuous thermal conduction network channel can increase the contact area between fillers and between fillers and the polymer matrix, provide abundant heat conduction paths, and reduce the interfacial thermal resistance between fillers. Therefore, forming a three-dimensional thermal conduction network in the polymer matrix through different preparation methods is an effective way to achieve high thermal conductivity with low-loading fillers. Summary of the Invention

[0006] Aiming at the above-mentioned drawbacks of the prior art, the present invention provides a graphite / carbon fiber felt / epoxy composite with a three-dimensional thermal conduction network and a preparation method thereof. The purpose is to improve the thermal conductivity of the composite by constructing a three-dimensional thermal conduction graphite / carbon fiber felt network in the epoxy polymer matrix. The present invention constructs an epoxy-based composite with a three-dimensional thermal conduction network by overlapping two-dimensional graphite flakes and layered carbon fiber felt, and prepares a graphite / carbon fiber felt / epoxy composite with a three-dimensional thermal conduction network by using a vacuum-assisted impregnation process and a mold forming technology.

[0007] Technical Solution

[0008] To achieve the above object, the present invention is realized through the following technical solutions:

[0009] The present invention provides a graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network, which is prepared by forming a three-dimensional thermal conduction network of graphite and carbon fiber surface felt, and then compounding the three-dimensional thermal conduction network of graphite / carbon fiber felt with an epoxy resin matrix.

[0010] Furthermore, the three-dimensional thermal conduction network of graphite / carbon fiber felt is prepared by impregnating the carbon fiber surface felt in a graphite ethanol mixture, and then drying to remove ethanol.

[0011] Furthermore, the specification of the carbon fiber surface felt is 50 g / cm 2 .

[0012] Furthermore, the graphite content in the graphite ethanol mixture is 10-30 wt%, and the mixing conditions are: rotation speed 400-600 r / min, time 5-20 min;

[0013] Preferably, the graphite ethanol mixture includes graphite and ethanol; and the graphite content in the graphite ethanol mixture is 20 wt%, and the mixing conditions are: rotation speed 500 r / min, time 10 min;

[0014] Furthermore, the drying and removal conditions of ethanol in the graphite / carbon fiber felt are 20-50 h at room temperature and 5-7 h in an oven at 70-90 °C;

[0015] Preferably, the drying and removal conditions of ethanol in the graphite / carbon fiber felt are 24 h at room temperature and 6 h in an oven at 80 °C.

[0016] Furthermore, the carbon fiber surface felt is a layered carbon fiber surface felt, and the layered carbon fiber surface felt is provided with 5-40 layers; preferably, the layered carbon fiber surface felt is provided with 10-30 layers.

[0017] Furthermore, the mass ratio of graphite to carbon fiber felt in the three-dimensional thermal conduction network of graphite / carbon fiber felt is 4-10:11-50; preferably, the mass ratio of graphite to carbon fiber felt in the three-dimensional thermal conduction network of graphite / carbon fiber felt is 5-8:15-30.

[0018] Furthermore, the graphite / carbon fiber felt / epoxy composite material is prepared by vacuum-assisted impregnation process and hot pressing in a mold, and the three-dimensional thermal conduction network of graphite / carbon fiber felt is compounded with an epoxy resin matrix; the epoxy resin matrix includes epoxy resin and polyamine hardener, and the weight ratio of epoxy resin to polyamine hardener is 2-4:1.

[0019] Preferably, the weight ratio of epoxy resin to polyamine hardener is 3:1.

[0020] Further, the temperature of the vacuum-assisted impregnation process is 20-30°C, the vacuum degree is 0.05-0.2 Pa, and the number of impregnation times is 2-3 times;

[0021] Preferably, the temperature of the vacuum-assisted impregnation process is 25°C, the vacuum degree is 0.1 Pa, and the number of impregnation times is 3 times;

[0022] Further, the temperature of the die hot pressing is 90-120°C, the pressure is 5-15 MPa, and the duration is 0.5-2 h;

[0023] Preferably, the temperature of the die hot pressing is 100°C, the pressure is 10 MPa, and the duration is 1 h.

[0024] A preparation method of a graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network, comprising the following steps:

[0025] (1) Prepare a layered carbon fiber surface felt from carbon fibers by a wet process:

[0026] First, soak the chopped carbon fibers in an ethanol solution, and successively add a dispersant (sodium dodecylbenzenesulfonate) for beating and a binder (polyvinyl alcohol) for fixation. Then, use a filter screen to dehydrate the paper stock to form a planar network carbon fiber surface felt. Finally, dry it in an oven at 50-70°C for 4-7 h to remove the liquid and obtain a dry carbon fiber surface felt. Among them, the weight ratio of the ethanol, dispersant, and binder is 4-8:0.5-2:2-4; preferably, the weight ratio of the ethanol, dispersant, and binder is: 6:1:3.

[0027] (2) Immerse the carbon fiber surface felt in a graphite ethanol mixture, and dry it to remove ethanol to obtain a three-dimensional thermal conduction network of graphite / carbon fiber felt.

[0028] (3) Compound the three-dimensional network of graphite / carbon fiber felt with epoxy resin through a vacuum-assisted impregnation process and a die hot pressing technology to prepare a graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network.

[0029] Further, in step (2), the graphite content in the graphite ethanol mixture is 10-30 wt%, and the mixing conditions are: rotation speed 400-600 r / min, time 5-20 min; the conditions for drying and removing ethanol in the graphite / carbon fiber felt are 20-50 h at room temperature and 5-7 h in an oven at 70-90°C.

[0030] Preferably, in step (2), the number of impregnation times of the carbon fiber surface felt in the graphite ethanol mixture is 4 times;

[0031] Preferably, the specific operation of step (2) is as follows: Cut the carbon fiber surface felt obtained in step (1) into a specification that fits the mold, i.e., 4 cm * 4 cm. Stack the cut carbon fiber surface felts into 10 layers and immerse them in a graphite ethanol mixed solution with a content of 20 wt%. After the preliminary impregnation treatment for 10 minutes, take out the carbon fiber surface felt from the mixed solution, and use a tweezer tool to separate each layer of felt sheet layer by layer. Subsequently, spread out each layer of carbon fiber felt evenly and let it air dry naturally at room temperature for 12 hours to achieve sufficient drying. After the drying process is completed, stack and arrange these 10 layers of carbon fiber felt, immerse them again in a newly prepared graphite ethanol mixed solution with a content of 20 wt%, keep the impregnation time for 10 minutes, and repeat the aforementioned drying procedure. This impregnation and drying process is carried out for the entire 10-layer carbon fiber surface felt and needs to be cycled four times to ensure sufficient impregnation and treatment effects. After the four impregnation and drying processes are completed, place the sample in an oven at 80 °C for 6 h to prepare a graphite / carbon fiber felt three-dimensional thermal conduction network. After impregnation, the graphite flakes in the graphite ethanol mixed solution adhere to the surface of the carbon fiber, and two-dimensional flaky graphite and one-dimensional carbon fiber are used to form a three-dimensional thermal conduction network. Among them, the graphite content in the graphite ethanol mixed solution is 20 wt%, and the mixing conditions are: rotation speed 500 r / min, time 10 min.

[0032] Furthermore, in step (3), the temperature of the vacuum-assisted impregnation process is 20 - 30 °C, the vacuum degree is 0.05 - 0.2 Pa, and the number of impregnation times is 2 - 3 times; the temperature of the mold hot pressing is 90 - 120 °C, the pressure is 5 - 15 MPa, and the duration is 0.5 - 2 h.

[0033] Furthermore, the specific operation of step (3) is as follows: At 25 °C, immerse the graphite / carbon fiber felt three-dimensional thermal conduction network in a plastic cup filled with an epoxy resin matrix, and then place the plastic cup in a vacuum oven with a vacuum degree of 0.1 Pa for vacuum-assisted impregnation treatment, that is, perform vacuum filtration in the oven for 5 minutes, and then take out the container. At this time, it is observed that the graphite / carbon fiber felt three-dimensional thermal conduction network floats in the epoxy resin. To ensure its complete immersion, it is necessary to apply appropriate pressure to the sample with a glass rod to promote its settlement and full absorption of the resin. After confirming that the graphite / carbon fiber felt three-dimensional thermal conduction network has completely sunk in the epoxy resin, place the plastic cup in the vacuum oven again for vacuum-assisted impregnation treatment. The vacuum-assisted impregnation treatment needs to be repeated three times to ensure sufficient vacuum-assisted impregnation effect.

[0034] After the three vacuum-assisted impregnation treatments are completed, place the sample in a mold and hot press it for 1 h under the conditions of a hot press with a temperature of 100 °C and a pressure of 10 MPa. Among them, the epoxy resin matrix includes epoxy resin and polyamine hardener, and the weight ratio of the epoxy resin to the polyamine hardener is 3:1。

[0035] Beneficial effects

[0036] The technical solution provided by the present invention has the following beneficial effects compared with the known public technologies:

[0037] (1) The carbon fiber material adopted in the present invention is a laminated carbon fiber surface felt prepared by a wet process. Partially interconnected carbon fibers already exist inside the material, which is beneficial to the construction of the subsequent three-dimensional heat conduction network.

[0038] (2) The present invention effectively and simply constructs an epoxy-based composite material with a three-dimensional heat conduction network through the lap joint of two-dimensional graphite sheets and laminated carbon fiber felts. At the same time, composite materials with different densities and different heat conduction properties can be obtained by controlling the content of graphite sheets, and the operation is simple and can be processed and applied on a large scale.

[0039] (3) The present invention constructs a three-dimensional heat conduction framework composed of two-dimensional graphite sheets and laminated carbon fiber felts. Subsequently, the heat conduction network is compounded with an epoxy resin matrix through a vacuum-assisted impregnation process and a die forming technique to obtain the graphite / carbon fiber felt / epoxy composite material. In this composite material, the graphite sheets are attached to the surface of the carbon fibers in a face-to-face contact manner, significantly increasing the effective contact area between the fillers and between the fillers and the epoxy resin, and thus forming a more abundant heat conduction channel inside the material and optimizing the transmission path of phonons (heat carriers). At the same time, adjacent carbon fibers are bridged with each other through graphite sheets, effectively reducing the interfacial thermal resistance and promoting the rapid transmission of phonons, further improving the heat conduction performance of the material.

[0040] (4) The preparation method of the present invention has the characteristics of simple process and easy operation. Moreover, the obtained composite material shows good convenience in processing and relatively low cost. Experimental results show that the in-plane thermal conductivity of the prepared heat conduction composite material can reach 0.763 W / mK, and its thermal conductivity is increased by about 302% compared with the pure epoxy resin matrix, showing excellent heat conduction performance. Description of the drawings

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0042] Figure 1 It is a flowchart for the preparation of the graphite / carbon fiber felt / epoxy composite material in Embodiment 1 of the present invention;

[0043] Figure 2 Microscopic morphology diagrams and carbon fiber diameter distribution diagrams of the materials in Example 1 and Example 5 of the present invention: (a) carbon fiber felt; (b) in-plane direction of the graphite / carbon fiber felt / epoxy composite with a graphite content of 15.12 wt% in Example 1; (c) out-of-plane direction of the graphite / carbon fiber felt / epoxy composite with a graphite content of 15.12 wt% in Example 1; (d) in-plane direction of the graphite / carbon fiber felt / epoxy composite with a graphite content of 48.23 wt% in Example 5; (e) out-of-plane direction of the graphite / carbon fiber felt / epoxy composite with a graphite content of 48.23 wt% in Example 5. Detailed implementation manners

[0044] 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 with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] The present invention will be further described below with reference to the embodiments.

[0046] The purchasing manufacturers of the raw materials used in the examples and comparative examples are as follows:

[0047] The carbon fiber felt is provided by Hangzhou Woken Co., Ltd.

[0048] Graphite is purchased from Henkel, USA.

[0049] Epoxy resin is purchased from Huntsman Corporation LY 1564;

[0050] The polyamine hardener is purchased from Huntsman Corporation 3486;

[0051] Alcohol is purchased from Sinopharm Chemical Reagent Co., Ltd.

[0052] Example 1:

[0053] A graphite / carbon fiber felt / epoxy composite with a three-dimensional heat conduction network, as Figure 1 shown, includes the following steps:

[0054] (1) Prepare a layered carbon fiber surface felt through a wet process to obtain a carbon fiber surface felt with a mass per unit area of 50 g / cm 2 . The specific preparation steps are as follows:

[0055] First, the short carbon fiber is soaked in an ethanol solution, and a dispersant (sodium dodecylbenzenesulfonate) is added successively for beating and a binder (polyvinyl alcohol) is added for fixation. Then, a filter screen is used to dehydrate the stock to form a planar reticulated carbon fiber surface felt. Finally, it is dried in an oven at 60 °C for 5 h to remove the liquid, and a dry carbon fiber surface felt is obtained. Among them, the weight ratio of ethanol, dispersant and binder is: 6:1:3.

[0056] (2) The carbon fiber surface felt obtained in step (1) is cut into a specification that fits the mold, that is, 4 cm * 4 cm. The cut carbon fiber surface felt is stacked into 10 layers and impregnated in a graphite ethanol mixed solution with a content of 20 wt%. After the preliminary impregnation treatment for 10 min, the carbon fiber surface felt is taken out of the mixed solution, and each layer of felt is separated layer by layer with a tweezer tool. Subsequently, each layer of carbon fiber felt is evenly spread out and naturally air-dried at room temperature for 12 hours to achieve sufficient drying. After the drying process is completed, the 10 layers of carbon fiber felt are stacked and sorted out, and then immersed again in a newly prepared graphite ethanol mixed solution with a content of 20 wt% for 10 minutes, and the aforementioned drying procedure is repeated. This impregnation and drying process is carried out on the whole 10-layer carbon fiber surface felt and needs to be cycled four times to ensure sufficient impregnation and treatment effects. After the four impregnation and drying processes are completed, the sample is placed in an oven at 80 °C for 6 h to prepare a graphite / carbon fiber felt three-dimensional thermal conduction network. After impregnation, the graphite flakes in the graphite ethanol mixed solution adhere to the carbon fiber surface, and two-dimensional flaky graphite and one-dimensional carbon fiber are built to form a three-dimensional thermal conduction network. Among them, the graphite content in the graphite ethanol mixed solution is 20 wt%, and the mixing conditions are: rotation speed 500 r / min, time 10 min.

[0057] (3) At 25 °C, the graphite / carbon fiber felt three-dimensional thermal conduction network is impregnated in a plastic cup containing an epoxy resin matrix, and then the plastic cup is placed in a vacuum oven with a vacuum degree of 0.1 Pa for vacuum-assisted impregnation treatment, that is, vacuum filtration is carried out in the oven for 5 min, and then the container is taken out. At this time, it is observed that the three-dimensional thermal conduction network of the graphite / carbon fiber felt in the container floats in the epoxy resin. To ensure its complete immersion, a moderate pressure is applied to the sample with a glass rod to promote its settlement and full absorption of the resin. After confirming that the three-dimensional thermal conduction network of the graphite / carbon fiber felt has completely sunk into the epoxy resin, the plastic cup is placed in the vacuum oven again for vacuum-assisted impregnation treatment. The vacuum-assisted impregnation treatment needs to be repeated three times to ensure sufficient vacuum-assisted impregnation effect.

[0058] After the three vacuum-assisted impregnation treatments are completed, the sample is placed in a mold and hot-pressed for 1 h under the conditions of a hot press with a temperature of 100 °C and a pressure of 10 MPa. Among them, the epoxy resin matrix includes epoxy resin and polyamine hardener, and the weight ratio of the epoxy resin to the polyamine hardener is 3:1.

[0059] Example 2:

[0060] A graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network, which is different from Example 1 in that the number of layers of the carbon fiber felt is increased to 15 layers.

[0061] Example 3:

[0062] A graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network, which is different from Example 1 in that the number of layers of the carbon fiber felt is increased to 20 layers.

[0063] Example 4:

[0064] A graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network, which is different from Example 1 in that the number of layers of the carbon fiber felt is increased to 25 layers.

[0065] Example 5:

[0066] A graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network, which is different from Example 1 in that the number of layers of the carbon fiber felt is increased to 30 layers.

[0067] Comparative Example 1:

[0068] A pure epoxy resin matrix, comprising the following steps:

[0069] Prepare a mixed solution according to the weight ratio of epoxy resin to polyamine hardener of 3:1, and naturally cure the mixed solution at room temperature for 48 h. The obtained solid is a pure epoxy resin matrix without thermal conductive fillers.

[0070] Comparative Example 2:

[0071] A graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conduction network, comprising the following steps:

[0072] (1) Prepare a layered carbon fiber surface felt by a wet process to obtain a carbon fiber surface felt of 50 g / cm 2 The specific preparation steps are as follows:

[0073] First, soak the chopped carbon fibers in an ethanol solution, and successively add a dispersant (sodium dodecylbenzenesulfonate) for beating and a binder (polyvinyl alcohol) for fixing. Then, use a filter screen to dehydrate the paper stock to form a planar network carbon fiber surface felt. Finally, dry it in an oven at 60 °C for 5 h to remove the liquid to obtain a dry carbon fiber surface felt. Among them, the weight ratio of ethanol, dispersant and binder is: 6:1:3.

[0074] (2) Cut the carbon fiber surface felt obtained in step (1) into a specification that matches the mold, that is, 4 cm * 4 cm.

[0075] (3) At room temperature, stack the cut carbon fiber surface felts into 10 layers and immerse them in a plastic cup filled with an epoxy resin matrix. Then, place the plastic cup in a vacuum oven with a vacuum degree of 0.1 Pa for vacuum-assisted impregnation treatment, that is, conduct vacuum filtration in the oven for 5 minutes, and then take out the container. At this time, it is observed that the three-dimensional thermal conduction network of graphite / carbon fiber felt in the container shows a floating phenomenon in the epoxy resin. To ensure its complete immersion, apply appropriate pressure to the sample with a glass rod to promote its settlement and full absorption of the resin. After confirming that the three-dimensional thermal conduction network of graphite / carbon fiber felt has completely sunk into the epoxy resin, place the plastic cup in the vacuum oven again for vacuum-assisted impregnation treatment. The vacuum-assisted impregnation treatment needs to be repeated three times to ensure sufficient vacuum-assisted impregnation effect.

[0076] After three times of vacuum-assisted impregnation treatment, place the sample in a mold and hot press it for 1 h under the conditions of a hot press with a temperature of 100 °C and a pressure of 10 MPa. Among them, the epoxy resin matrix includes epoxy resin and polyamine hardener, and the weight ratio of the epoxy resin to the polyamine hardener is 3:1.

[0077] (2) Performance testing

[0078] Use a laser flash thermal conductivity tester (NETZSCH, LFA 467, Germany) to measure the thermal diffusivity of the sample, and use differential scanning calorimetry (NETZSCH, DSC 214, Germany) to determine the specific heat, and calculate the thermal conductivity λ of pure epoxy resin and its composite materials according to the formula λ = α × Cp × ρ. The results are shown in Table 1.

[0079] Table 1 Thermal diffusivity and thermal conductivity of the composite materials prepared in each example and comparative example

[0080]

[0081] Note: For Comparative Example 2, only the in-plane thermal conductivity was measured, and other values were not measured.

[0082] Table 1 shows the thermal diffusivity and thermal conductivity of the composite materials prepared in each example and comparative example. It can be seen from Table 1 that the more the number of layers and the more the filler content, the corresponding increase in the number of contact points and thermal conduction channels between the fillers and between the fillers and the epoxy matrix. Compared with the comparative examples, the thermal diffusivity and thermal conductivity of Examples 1-5 have been improved, and the thermal diffusivity and thermal conductivity of Example 5 are the highest, increasing by 302% compared with Comparative Example 1. The reason is as follows:

[0083] In the present invention, by combining two-dimensional flaky graphite materials with one-dimensional carbon fibers, an enhanced thermal conduction network is achieved. This structural design significantly expands the effective path of heat conduction by increasing the contact points between filler particles and the interconnection nodes between the filler and the epoxy resin matrix at the microscale. The increase in these interconnection nodes provides more favorable channels for the transmission of phonons (i.e., heat energy carriers), thereby optimizing the thermal conductivity of the material. Specifically, as the graphite content increases, the number of formed interconnection nodes and thermal conduction channels increases correspondingly, which directly leads to an increase in the thermal conductivity of the material. This phenomenon can be attributed to the increase in heat conduction paths and the resulting improvement in the phonon scattering mechanism. In addition, through the bridging effect of graphite between adjacent carbon fibers, the interfacial thermal resistance on the surface of the carbon fibers is effectively reduced. This bridging effect promotes the rapid transfer of phonons between carbon fibers, thereby improving the thermal conduction efficiency of the overall composite material.

[0084] Figure 2 Figure 4 is the micrograph of the carbon fiber surface felt and the graphite / carbon fiber felt / epoxy composite material. In this structure, two-dimensional flaky graphite is closely connected to the carbon fibers, thus significantly increasing the contact points between the fillers and between the fillers and the epoxy resin. These increased contact points create a richer heat conduction path for heat energy transfer, thereby optimizing the transmission channels of phonons (i.e., heat energy carriers) inside the material. As the graphite content increases, the number of formed connection points and heat conduction paths increases correspondingly, which directly leads to an increase in the thermal conductivity of the material. In addition, effective lap joints are achieved between adjacent carbon fibers through graphite glue. This structural design effectively reduces the interfacial thermal resistance on the surface of the carbon fibers, thereby accelerating the propagation speed of phonons and further improving the thermal conductivity of the material.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network, characterized in that: The preparation steps are as follows: (1) preparing carbon fiber into a layered carbon fiber surface felt by a wet process; (2) immersing the carbon fiber surface felt in a graphite ethanol mixture, and drying and removing the ethanol to obtain a graphite / carbon fiber felt three-dimensional thermal conductive network; (3) The three-dimensional network of graphite / carbon fiber felt is compounded with epoxy resin by vacuum-assisted impregnation process and mold hot pressing technology to prepare a graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network; Among them, the preparation method of the layered carbon fiber surface felt described in step (1) is as follows: first, the short-cut carbon fiber is immersed in an ethanol solution, and a dispersant is added for pulping and an adhesive is added for fixing; then, a filter is used to dehydrate the paper material to form a flat mesh carbon fiber surface felt; finally, it is dried in an oven to remove the liquid to obtain a dry carbon fiber surface felt.

2. The graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network according to claim 1, characterized in that: The graphite content in the graphite-ethanol mixed solution is 10-30wt%, and the mixing conditions are: rotation speed 400-600r / min, time 5-20min; The drying and removal conditions of the ethanol in the graphite / carbon fiber felt are: 20-50 hours at room temperature and 5-7 hours in an oven at 70-90°C.

3. The graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network according to claim 1, characterized in that: The weight ratio of the ethanol, the dispersant and the adhesive is 4-8:0.5-2:2-4.

4. The graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network according to claim 1, characterized in that: The mass ratio of graphite to carbon fiber felt in the graphite / carbon fiber felt three-dimensional heat-conducting network is 4-10:11-50.

5. The graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network according to claim 1, characterized in that: The epoxy resin matrix comprises epoxy resin and polyamine hardener, and the weight ratio of the epoxy resin to the polyamine hardener is 2-4:

1.

6. The graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network according to claim 1, characterized in that: The temperature of the vacuum-assisted impregnation process is 20-30° C., the vacuum degree is 0.05-0.2 Pa, and the number of impregnations is 2 to 3 times.

7. The graphite / carbon fiber felt / epoxy composite material with a three-dimensional thermal conductive network according to claim 1, characterized in that: The temperature of the mold hot pressing molding is 90-120° C., the pressure is 5-15 MPa, and the duration is 0.5-2 hours.

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