Graphene high-thermal-conductivity composite paste and preparation method thereof

Abstract

The application relates to the field of heat-conducting materials, in particular to a graphene high-heat-conducting composite slurry and a preparation method thereof. In order to solve the problem that graphene materials are difficult to load a large number of and uniform nano silver particles, so that the heat-conducting performance of the heat-conducting filler is limited, the application comprises the following steps: preparing an Ag / Ti3AlC2 template, mixing glucose with the Ag / Ti3AlC2 template, and then performing a hydrothermal reaction to form carbon-modified powder, then dispersing and mixing the carbon-modified powder and graphene oxide in deionized water, adding glucose to perform secondary hydrothermal reaction, obtaining three-dimensional aerogel solid particles, placing the three-dimensional aerogel solid particles in an HF solution to remove the MXene template, obtaining an Ag@GO composite material, so that a large number of and uniform Ag is loaded to the surface of the GO material, and finally mixing the final product with epoxy resin to obtain the graphene high-heat-conducting composite slurry. The application can realize the uniform loading of a large number of silver nano particles, and improve the heat-conducting capacity of the material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-conducting materials, in particular to a graphene high-thermal-conductivity composite paste and a preparation method thereof. BACKGROUND

[0002] High-thermal-conductivity paste is widely used in the field of electronic devices. Metal fillers are mostly used in the material. Metal materials transfer heat through free electrons, and the efficiency is extremely high, which is the first choice for thermal conductive materials. However, metal thermal conductive materials mostly exist in the form of powder or block, and it is difficult to stably and reliably transfer heat between two irregular objects. In order to maximize the heat transfer of thermal conductive materials, fluid substances are used as carriers of thermal conductive metal powder, thereby forming a thermal conductive paste with good adhesion.

[0003] In existing research, silver powder is mostly used for the selection of thermal conductive metal powder. Its ultra-high thermal conductivity is widely used. For example, the patent document with publication number CN106987123A uses resin as a coating for the thermal carrier, uses graphene and boron nitride as the carrier of nano-silver particles, forms a thermal conductive network through the bridging of silver and graphene materials, and finally improves the thermal conductivity of the material. However, the limitation of using graphene and boron nitride is that they cannot be used in excess. Excessive use of graphene can easily lead to agglomeration due to the van der Waals force between the layers, forming a "bottleneck" in heat conduction. In addition, it is found that during the modification of the material, the nano-silver particles are not uniformly distributed on the surface of the graphene. The inertness of the graphene surface needs to be modified additionally. Therefore, the interface bonding ability of graphene and silver is weak, and peeling off easily occurs under mechanical stress, making it difficult to use for a long time.

[0004] In view of the above difficulties, for example, the patent document with publication number CN113105735A uses MXene as a carrier for loading nano-silver particles. MXene material is easy to disperse in water, and its surface naturally has reducing properties, so it can directly react with silver nitrate without modification, thereby forming a uniform load of nano-silver particles, and the processing convenience is extremely strong. However, MXene material is easily oxidized in water and air, and its chemical stability will be slowly oxidized to form titanium dioxide and other oxides, resulting in permanent attenuation of structure and thermal conductivity. The carrier resin carrying MXene material is inevitably cracked under the influence of high temperature for a long time. The thermal stability of MXene is not as good as that of graphene material, and its long-term use is not as good as that of graphene carrier. SUMMARY

[0005] In order to solve the problems of poor interface bonding force of graphene material, difficult dispersion, difficult loading of nano-silver particles, limited performance of graphene-based thermal conductive filler, and shorter oxidation resistance of the reducing carrier than graphene, the present application provides a graphene high-thermal-conductivity composite slurry and a preparation method thereof.The technical scheme adopted by the present application is as follows:

[0006] A preparation method of a graphene high-thermal-conductivity composite slurry, comprising the following preparation steps:

[0007] S1, stirring and reacting Ti3AlC2 powder in an HF solution, washing to neutral after the reaction, ultrasonic treatment in ice water, centrifugation to obtain a supernatant to obtain an MXene dispersion, and adding an AgNO3 solution to the MXene dispersion to obtain an MXene / Ag composite dispersion;

[0008] S2, ultrasonic dissolution of glucose in the MXene / Ag composite dispersion, then heating to 155-180 DEG C for hydrothermal reaction for 2-4h, post-treatment after the reaction to obtain carbon modified powder;

[0009] S3, dispersing and mixing the carbon modified powder and graphene oxide in deionized water for 3-6h, then adding glucose and heating to 155-180 DEG C for hydrothermal reaction for 5-7h, and sequentially performing displacement and drying after the reaction to obtain three-dimensional aerogel solid particles;

[0010] S4, reacting the three-dimensional aerogel solid particles in an HF solution with a volume concentration of 5-15% for 18-30h, washing and soaking to obtain an Ag@GO composite material;

[0011] S5, mixing the Ag@GO composite material with epoxy resin to obtain a graphene high-thermal-conductivity composite slurry.

[0012] The preparation method of the present application first uses MXene material, in the preparation process, the surface of the MXene sheet layer has a large number of reducing groups, which can react with the AgNO3 solution to generate a large number of and uniformly distributed nano-silver particles, which can be used as a template loaded on the surface of graphene, and then glucose is added for primary hydrothermal carbon coating, in this step operation, by strictly limiting the temperature and time of the glucose hydrothermal reaction, the glucose is limited to nucleate and grow around the silver nanoparticles, avoiding the formation of a dense blanket during the carbonization process of the glucose, this step operation has two effects, the first effect is to expose a large area of MXene material, which is convenient for subsequent etching removal by HF solution, which can provide pores and channels, and the channel is a multi-hole, non-continuous network with nano-silver particles as nodes, thereby greatly strengthening the thermal conduction network;

[0013] The second action point of the above operation is that the carbon layer grown around the silver nanoparticles can be connected with the subsequently added graphene through π-π interaction and physical adsorption, and the double connection of silver-carbon makes the connection between graphene and silver very stable, which greatly enhances the binding ability of graphene and silver, and it is difficult to peel off under the influence of a larger external mechanical force, thus greatly increasing the service life and not reducing the heat conduction ability after long-term use.

[0014] The present application uses twice hydrothermal carbonization for the first time, and single hydrothermal carbonization is not enough to generate a corresponding porous network, because when the subsequent HF solution elution removes the MXene template, the connection part of the graphene and the carbon layer formed by the first hydrothermal carbonization is destroyed, so that the distribution of silver nanoparticles becomes uneven; and the second hydrothermal carbonization can enhance the connection between graphene and the carbon layer formed by the first hydrothermal carbonization, so that in the new glucose hydrothermal environment, the newly born amorphous carbon will be generated between the graphene sheets, thereby strengthening the contact point deposition between the graphene sheets and the primary nano-carbon layer, and cooperating with the first formed porous carbon network, to form a highly cross-linked three-dimensional network with higher integration.

[0015] Preferably, the particle size of the Ti3AlC2 powder in S1 is 200-400 mesh, the reaction time is 24-36 h, the volume concentration of the HF solution is 40%, the centrifugal speed is 3500 rpm, and the concentration of the MXene dispersion liquid is controlled at 5 mg / mL.

[0016] In the present application, the black liquid in the supernatant is selected when collecting the etching reactants, which can ensure that the MXene material as a template can be removed better, and on the other hand can ensure that the three-dimensional porous graphene / silver / carbon network material formed subsequently will not have the phenomenon of excessively large cavity, so as not to collapse and shrink, and ensure the integrity of the three-dimensional heat conduction network.

[0017] Preferably, the concentration of the AgNO3 solution in S1 is 10 mM, the volume ratio of the MXene dispersion liquid to the AgNO3 solution is 4:1, and the reaction time of the MXene dispersion liquid and the AgNO3 solution is 12-24 h.

[0018] Preferably, the solid-liquid ratio of the glucose to the MXene / Ag composite dispersion liquid in S2 is 80-100 mg:50 mL.

[0019] Preferably, the post-processing operation in S2 includes natural cooling, centrifugal washing and vacuum drying, and the temperature of the vacuum drying is 60°C.

[0020] Preferably, the mass ratio of the carbon modified powder, graphene and glucose in S3 is 2.0-2.5:1:1, and the dispersion concentration of the graphene oxide is 1-2 mg / mL.

[0021] Preferably, the solution used for replacing the three-dimensional aerogel solid particles in S3 is tert-butyl alcohol.

[0022] The secondary hydrothermal reaction in step S3 of the application forms a new solid network, in which the inner cavity is filled with liquid, the surface of the graphene oxide has both hydrophilic and hydrophobic regions, and the liquid crystal phase is generated due to the π-π stacking effect, thereby forming a hydrogel. Therefore, when direct drying is performed, the surface tension of water will generate a large capillary force on the network skeleton, causing the pores to be flattened and the sheet structure to be adhered together. Therefore, tert-butyl alcohol is used to replace water, and the surface tension of tert-butyl alcohol is only one-third of that of water, so that the carbon nanometer skeleton can be more gently reserved, thereby ensuring the reservation of the heat conduction network of the material.

[0023] Preferably, the drying method in S3 is supercritical CO2 drying or freeze vacuum drying.

[0024] Preferably, the mixing mass ratio of the Ag@GO composite material and the epoxy resin in S5 is 3-6:4-7.

[0025] On the other hand, the graphene high-thermal-conductivity composite paste prepared by the preparation method of the graphene high-thermal-conductivity composite paste provided by the application can be widely applied in technical fields such as electronic heat dissipation and new energy, and can help to quickly transfer heat, improve heat dissipation efficiency and reduce the weight of equipment.

[0026] The application has the following beneficial effects:

[0027] The primary point of the application is to use MXene as a template for the distribution of silver nanoparticles, so as to ensure that the silver nanoparticles can be uniformly and massively distributed in the three-dimensional carbon network, thereby greatly improving the uniform loading capacity of the graphene material.

[0028] The Ag@GO composite material prepared by the application has a new three-dimensional pore network, and even if it is agglomerated, it will not produce the "stacking" phenomenon, so there will be no bottleneck in heat conduction.

[0029] The application uses silver nanoparticles as core nodes, which greatly reduces the interfacial thermal resistance between the epoxy resin and the carbon network. The silver nanoparticles exist in the form of being embedded in the carbon network, rather than growing on the surface of the carbon layer, so that the thermal conductivity efficiency is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The thermal conductivity column chart of the examples and comparative examples of the application.

[0031] Figure 2 The broken line trend chart of the thermal conductivity retention rate of the examples and the comparative examples of the present application is shown in the following figure. DETAILED DESCRIPTION

[0032] The present application will be described in detail below with reference to the accompanying drawings. Figure 1 The accompanying drawings are referred to in order to further assist in understanding of the present application. Figure 2 The embodiments of the present application will be described in detail. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0033] Example 1

[0034] First step: preparation of a few-layer MXene dispersion

[0035] 1 g of Ti3AlC2 powder with a particle size of 300 mesh was slowly added to 20 mL of HF solution with a volume concentration of 40%, and was magnetically stirred at 35℃ for 30 hours. After the reaction was completed, deionized water was used for washing until the supernatant pH>6, and then the washed precipitate was placed in 100 mL of ice water under an argon environment for ultrasonic treatment for 1 hour, and then was centrifuged at 3500 rpm for 1 hour. The black supernatant was collected, and the concentration of MXene in the supernatant was controlled to be 5 mg / mL by filtration or water addition;

[0036] Second step: reduction of silver nanoparticles on MXene

[0037] 40 mL of the MXene dispersion was taken and magnetically stirred, and 10 mL of AgNO3 solution with a concentration of 10 mM was added dropwise. The mixture was stirred at room temperature for 18 hours in the dark. After the reaction was completed, deionized water was used for washing, and the precipitate was re-dispersed in 40 mL of deionized water to form a MXene / Ag composite dispersion.

[0038] Third step: primary hydrothermal carbon coating

[0039] 90 mg of glucose was added to 50 mL of the MXene / Ag composite dispersion, and was dissolved using ultrasonic treatment and then transferred to a reaction kettle and placed in a blast drying oven for high-temperature treatment. The treatment temperature was 160℃, and the treatment time was 3 hours. After being taken out, the mixture was naturally cooled and centrifuged and washed, and the washed precipitate was placed in a vacuum drying oven at 60℃ for drying to obtain a black carbon-modified powder;

[0040] Fourth step: GO connection and secondary hydrothermal carbon crosslinking

[0041] The third step carbon modified powder 180 mg was placed in 40 mL of deionized water and ultrasonically dispersed, then mixed with 40 mL of graphene oxide dispersion solution with a concentration of 2 mg / mL, and magnetically stirred for 4.5 h. Then 80 mg of glucose was added to the mixture, and after dissolution, it was placed in a blast drying oven at 160°C for 6 h. After the reaction was completed, it was naturally cooled, centrifuged with deionized water, and the precipitate was placed in a t-butyl alcohol solution for freeze-drying to obtain three-dimensional aerogel solid particles;

[0042] Fifth step: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 10%, etched at room temperature for 24 hours, washed and soaked with deionized water until the washing liquid was neutral, and freeze-dried again to obtain Ag@GO composite materials;

[0043] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0044] Example 2

[0045] First step: Preparation of a few-layer MXene dispersion

[0046] 1 g of Ti3AlC2 powder with a particle size of 200 mesh was slowly added to 20 mL of HF solution with a volume concentration of 40%, and magnetically stirred at 35°C for 24 hours. After the reaction was completed, the washing liquid was washed with deionized water until the pH was > 6, and then the washed precipitate was placed in 100 mL of ice water under an argon environment and ultrasonically treated for 1 hour. Then it was centrifuged at 3500 rpm for 1 hour, and the black supernatant was collected. The concentration of MXene in the supernatant was controlled to be 5 mg / mL by filtration or adding water;

[0047] Second step: Reduction of silver nanoparticles on MXene

[0048] 40 mL of MXene dispersion was taken and magnetically stirred, and 10 mL of AgNO3 solution with a concentration of 10 mM was added dropwise. It was stirred at room temperature for 12 h in the dark. After the reaction was completed, it was washed with deionized water, and the precipitate was re-dispersed in 40 mL of deionized water to form a MXene / Ag composite dispersion.

[0049] Third step: Primary hydrothermal carbon coating

[0050] 80 mg of glucose was added to 50 mL of MXene / Ag composite dispersion, which was dissolved using ultrasonic and then transferred to a reaction kettle and treated at a high temperature in a blast drying oven. The treatment temperature was 155°C, and the treatment time was 24 hours. After being taken out, it was naturally cooled and centrifuged, and the washed precipitate was dried in a vacuum drying oven at 60°C to obtain black carbon modified powder;

[0051] Fourth step: GO connection and secondary hydrothermal carbon cross-linking

[0052] The third step carbon modified powder 160 mg was placed in 40 mL of deionized water and ultrasonically dispersed, then mixed with 80 mL of graphene oxide dispersion solution with a concentration of 1 mg / mL, and magnetically stirred for 3 h. Then 80 mg of glucose was added to the mixture, and after dissolution, it was placed in a blast drying oven at 155°C for 5 h. After the reaction was completed, it was naturally cooled, centrifuged with deionized water, and the precipitate was placed in a tert-butyl alcohol solution for freeze-drying to obtain three-dimensional aerogel solid particles.

[0053] Fifth step: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 5%, etched at room temperature for 30 hours, washed and soaked with deionized water until the washing liquid was neutral, and freeze-dried again to obtain Ag@GO composite materials.

[0054] The Ag@GO composite materials were mixed with epoxy resin at a mass ratio of 3:7 to obtain a graphene high-thermal-conductivity composite slurry.

[0055] Example 3

[0056] First step: Preparation of a few-layer MXene dispersion

[0057] 1 g of Ti3AlC2 powder with a particle size of 400 mesh was slowly added to 20 mL of HF solution with a volume concentration of 40%, and magnetically stirred at 35°C for 36 hours. After the reaction was completed, the washing liquid was washed with deionized water until the pH was > 6, and then the washed precipitate was placed in 100 mL of ice water under an argon environment and ultrasonically treated for 1 hour. Then it was centrifuged at 3500 rpm for 1 hour, and the black supernatant was collected. The concentration of MXene in the supernatant was controlled to be 5 mg / mL by filtration or adding water.

[0058] Second step: Reduction of silver nanoparticles on MXene

[0059] 40 mL of MXene dispersion was taken and magnetically stirred, and 10 mL of AgNO3 solution with a concentration of 10 mM was added dropwise. It was stirred at room temperature for 24 h in the dark. After the reaction was completed, it was washed with deionized water, and the precipitate was redispersed in 40 mL of deionized water to form a MXene / Ag composite dispersion.

[0060] Third step: Primary hydrothermal carbon coating

[0061] 100 mg of glucose was added to 50 mL of MXene / Ag composite dispersion, which was dissolved using ultrasonic and then transferred to a reaction kettle and treated at a high temperature in a blast drying oven. The treatment temperature was 180°C, and the treatment time was 4 hours. After being taken out, it was naturally cooled and centrifuged, and the washed precipitate was dried in a vacuum drying oven at 60°C to obtain black carbon modified powder.

[0062] Fourth step: GO connection and secondary hydrothermal carbon cross-linking

[0063] The third step carbon modified powder 200 mg was placed in 40 mL of deionized water and ultrasonically dispersed, then mixed with 40 mL of graphene oxide dispersion solution with a concentration of 2 mg / mL, and magnetically stirred for 6 h. Then 80 mg of glucose was added to the mixture, and after dissolution, it was placed in a blast drying oven at 180°C for 7 h. After the reaction was completed, it was naturally cooled, centrifuged with deionized water, and the precipitate was placed in a tert-butyl alcohol solution for freeze-drying to obtain three-dimensional aerogel solid particles.

[0064] Fifth step: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 15%, etched at room temperature for 18 hours, and then washed and soaked with deionized water until the washing liquid was neutral. Freeze-drying was performed again to obtain Ag@GO composite materials.

[0065] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 6:4 to obtain a graphene high-thermal-conductivity composite slurry.

[0066] Comparative Example 1 - No MXene used as a template for silver nanoparticles

[0067] First step: Preparation of hexagonal boron nitride dispersion

[0068] 1 g of hexagonal boron nitride powder with a particle size of 200 mesh was placed in a hydrogen environment and heated to 600°C for modification. After the reaction was completed, reduced hexagonal boron nitride was obtained, which was placed in deionized water to form a hexagonal boron nitride dispersion with a concentration of 5 mg / mL.

[0069] Second step: Reduction of silver nanoparticles on hexagonal boron nitride

[0070] 40 mL of hexagonal boron nitride dispersion was taken and magnetically stirred, and 10 mL of AgNO3 solution with a concentration of 10 mM was added dropwise. The mixture was stirred at room temperature in the dark for 24 h. After the reaction was completed, the precipitate was washed with deionized water and re-dispersed in 40 mL of deionized water to form a MXene / Ag composite dispersion.

[0071] Third step: Primary hydrothermal carbon coating

[0072] 80 mg of glucose was added to 50 mL of MXene / Ag composite dispersion, which was dissolved using ultrasonic and then transferred to a reaction kettle and subjected to high-temperature treatment in a blast drying oven. The treatment temperature was 160°C, and the treatment time was 2 hours. After being taken out and naturally cooled, the precipitate was washed by centrifugation and dried in a vacuum drying oven at 60°C to obtain black carbon modified powder.

[0073] Fourth step: GO connection and secondary hydrothermal carbon cross-linking

[0074] The third step carbon modified powder 160 mg was placed in 40 mL of deionized water and ultrasonically dispersed, then mixed with 40 mL of graphene oxide dispersion solution with a concentration of 2 mg / mL, magnetically stirred for 3 h, then 80 mg of glucose was added to the mixture, after dissolution, placed in a blast drying oven at 160°C for 6 h, after the reaction was completed, it was naturally cooled, centrifuged with deionized water, and the precipitate was placed in a t-butyl alcohol solution for freeze-drying to obtain three-dimensional aerogel solid particles;

[0075] Step 5: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 5%, etched at room temperature for 24 hours, washed and soaked with deionized water until the washing liquid was neutral, and freeze-dried again to obtain Ag@GO composite material;

[0076] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0077] Comparative Example 2 - No secondary hydrothermal carbonization

[0078] Step 1: Preparation of few-layer MXene dispersion

[0079] 1 g of Ti3AlC2 powder with a particle size of 300 mesh was slowly added to 20 mL of HF solution with a volume concentration of 40%, magnetically stirred at 35°C for 30 hours, after the reaction was completed, washed with deionized water until the supernatant pH>6, then the washed precipitate was placed in 100 mL of ice water under an argon environment and ultrasonically treated for 1 hour, then centrifuged at 3500 rpm for 1 hour, the black supernatant was collected, and the concentration of MXene in the supernatant was controlled to 5 mg / mL by filtration or adding water;

[0080] Step 2: Reduction of silver nanoparticles on MXene

[0081] 40 mL of MXene dispersion was magnetically stirred, 10 mL of AgNO3 solution with a concentration of 10 mM was added dropwise, stirred at room temperature in the dark for 18 h, after the reaction was completed, deionized water was used for washing, and the precipitate was re-dispersed in 40 mL of deionized water to form a MXene / Ag composite dispersion.

[0082] Step 3: Primary hydrothermal carbon coating

[0083] 90 mg of glucose was added to 50 mL of MXene / Ag composite dispersion, dissolved using ultrasonic, then transferred to a reaction kettle and placed in a blast drying oven for high-temperature treatment, the treatment temperature was 160°C and the treatment time was 3 hours, then it was taken out, naturally cooled and centrifuged, the washed precipitate was placed in a vacuum drying oven at 60°C for drying, and black carbon modified powder was obtained.

[0084] Fourth step: GO connection

[0085] The third step carbon modified powder 180mg was placed in 40mL deionized water and ultrasonically dispersed, then mixed with 40mL graphene oxide dispersion solution with a concentration of 2mg / mL, magnetic stirring for 4.5h, and graphene solid particles were obtained;

[0086] Fifth step: The graphene solid particles were placed in 50mL HF solution with a volume concentration of 10%, etched at room temperature for 24 hours, centrifuged and soaked with deionized water until the washing liquid was neutral, and then freeze-dried again to obtain Ag@GO composite material;

[0087] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0088] Comparative example 3 - hydrothermal carbonization using too high temperature and time

[0089] First step: Preparation of few-layer MXene dispersion

[0090] 1g of Ti3AlC2 powder with a particle size of 300 mesh was slowly added to 20mL of HF solution with a volume concentration of 40%, and magnetic stirring was carried out at 35℃ for 30h. After the reaction, deionized water was used for washing until the supernatant pH>6, then the washed precipitate was placed in 100mL ice water under argon environment and ultrasonically treated for 1h, then centrifuged at 3500rpm for 1h, the black supernatant was collected, and the concentration of MXene in the supernatant was controlled to 5mg / mL by filtration or adding water;

[0091] Second step: Reduction of silver nanoparticles on MXene

[0092] 40mL of MXene dispersion was taken and magnetic stirring was carried out, 10mL of AgNO3 solution with a concentration of 10mM was added dropwise, and stirring was carried out at room temperature in the dark for 18h. After the reaction, deionized water was used for washing, and the precipitate was re-dispersed in 40mL of deionized water to form a MXene / Ag composite dispersion.

[0093] Third step: First hydrothermal carbon coating

[0094] 90mg of glucose was added to 50mL of MXene / Ag composite dispersion, dissolved using ultrasonic, then transferred to a reaction kettle, and placed in a blast drying oven for high temperature treatment, the treatment temperature was 240℃, and the treatment time was 6h. After taking out, natural cooling and centrifugal washing were carried out, and the washed precipitate was placed in a vacuum drying oven at 60℃ for drying to obtain black carbon modified powder;

[0095] Fourth step: GO connection and second hydrothermal carbon cross-linking

[0096] The third step carbon modified powder 180 mg was placed in 40 mL of deionized water and ultrasonically dispersed, then mixed with 40 mL of graphene oxide dispersion solution with a concentration of 2 mg / mL, and magnetically stirred for 4.5 h. Then 80 mg of glucose was added to the mixture, and after dissolution, it was placed in a blast drying oven at 200°C for 12 h. After the reaction was completed, it was naturally cooled, centrifuged with deionized water, and the precipitate was placed in a t-butyl alcohol solution for freeze-drying to obtain three-dimensional aerogel solid particles.

[0097] Step 5: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 10%, etched at room temperature for 24 hours, washed and soaked with deionized water until the washing liquid was neutral, and freeze-dried again to obtain Ag@GO composite materials.

[0098] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0099] Comparative Example 4 - Hydrothermal carbonization using too low a temperature and time

[0100] Step 1: Preparation of a few-layer MXene dispersion

[0101] 1 g of Ti3AlC2 powder with a particle size of 300 mesh was slowly added to 20 mL of HF solution with a volume concentration of 40%, and magnetically stirred at 35°C for 30 hours. After the reaction was completed, the washing liquid was washed with deionized water until the pH was > 6, and then the washed precipitate was placed in 100 mL of ice water under an argon environment and ultrasonically treated for 1 hour, then centrifuged at 3500 rpm for 1 hour. The black supernatant was collected, and the concentration of MXene in the supernatant was controlled to be 5 mg / mL by filtration or adding water.

[0102] Step 2: Reduction of silver nanoparticles on MXene

[0103] 40 mL of the MXene dispersion was magnetically stirred, and 10 mL of AgNO3 solution with a concentration of 10 mM was added dropwise. The mixture was stirred at room temperature in the dark for 18 h. After the reaction was completed, the precipitate was redispersed in 40 mL of deionized water to form a MXene / Ag composite dispersion.

[0104] Step 3: First hydrothermal carbon coating

[0105] 90 mg of glucose was added to 50 mL of the MXene / Ag composite dispersion, which was dissolved using ultrasonication and then transferred to a reaction kettle. The reaction kettle was placed in a blast drying oven for high-temperature treatment at a temperature of 150°C for 1 hour. The product was naturally cooled, centrifuged, and the precipitate was dried in a vacuum drying oven at 60°C to obtain black carbon modified powder.

[0106] Fourth step: GO connection and secondary hydrothermal carbon cross-linking

[0107] The third step carbon modified powder 180 mg was placed in 40 mL of deionized water and ultrasonically dispersed, then mixed with 40 mL of graphene oxide dispersion solution with a concentration of 2 mg / mL, and magnetically stirred for 4.5 h. Then 80 mg of glucose was added to the mixture, and after dissolution, it was placed in a blast drying oven at 150°C for 3 h. After the reaction was completed, it was naturally cooled, centrifuged with deionized water, and the precipitate was placed in a tert-butyl alcohol solution for freeze-drying to obtain three-dimensional aerogel solid particles.

[0108] Fifth step: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 10%, etched at room temperature for 24 hours, centrifuged and soaked with deionized water until the washing liquid was neutral, and freeze-dried again to obtain Ag@GO composite materials.

[0109] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0110] Comparative Example 5 - HF solution etching concentration too high

[0111] Fifth step: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 40%, etched at room temperature for 24 hours, centrifuged and soaked with deionized water until the washing liquid was neutral, and freeze-dried again to obtain Ag@GO composite materials.

[0112] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0113] The remaining steps were the same as in Example 1.

[0114] Comparative Example 6 - HF solution etching concentration too low

[0115] Fifth step: The three-dimensional aerogel solid particles were placed in 50 mL of HF solution with a volume concentration of 1%, etched at room temperature for 24 hours, centrifuged and soaked with deionized water until the washing liquid was neutral, and freeze-dried again to obtain Ag@GO composite materials.

[0116] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0117] The remaining steps were the same as in Example 1.

[0118] Comparative Example 7 - No replacement of tert-butyl alcohol

[0119] First step: preparation of a few-layer MXene dispersion

[0120] 1 g of Ti3AlC2 powder with a particle size of 300 mesh was slowly added to 20 mL of HF solution with a volume concentration of 40%, and was stirred magnetically at 35°C for 30 hours. After the reaction was completed, the product was washed with deionized water until the supernatant pH was > 6, and then the washed precipitate was placed in 100 mL of ice water under an argon environment and was ultrasonically treated for 1 hour. Then, the product was centrifuged at 3500 rpm for 1 hour, and the black supernatant was collected. The concentration of MXene in the supernatant was controlled to be 5 mg / mL by filtration or by adding water.

[0121] Second step: reduction of silver nanoparticles on MXene

[0122] 40 mL of the MXene dispersion was taken and was magnetically stirred. Then, 10 mL of AgNO3 solution with a concentration of 10 mM was added dropwise, and the mixture was stirred at room temperature for 18 hours in the dark. After the reaction was completed, the product was washed with deionized water, and the precipitate was re-dispersed in 40 mL of deionized water to form a MXene / Ag composite dispersion.

[0123] Third step: primary hydrothermal carbon coating

[0124] 90 mg of glucose was added to 50 mL of the MXene / Ag composite dispersion, and was dissolved using ultrasonic treatment. Then, the product was transferred to a reaction kettle and was treated at a high temperature in a blast drying oven. The treatment temperature was 160°C, and the treatment time was 3 hours. The product was removed, was naturally cooled, and was centrifugally washed. The washed precipitate was dried in a vacuum drying oven at 60°C to obtain a black carbon-modified powder.

[0125] Fourth step: GO connection and secondary hydrothermal carbon crosslinking

[0126] The carbon-modified powder of 180 mg from the third step was ultrasonically dispersed in 40 mL of deionized water, and then was mixed with 40 mL of graphene oxide dispersion with a concentration of 2 mg / mL. The mixture was magnetically stirred for 4.5 hours, and then 80 mg of glucose was added to the mixture. After the glucose was dissolved, the mixture was placed in a blast drying oven at 160°C for 6 hours. After the reaction was completed, the product was naturally cooled, was centrifugally washed with deionized water, and was freeze-dried to obtain a three-dimensional aerogel solid particle.

[0127] The three-dimensional aerogel solid particle was placed in 50 mL of HF solution with a volume concentration of 10%, and was etched at room temperature for 24 hours. The product was centrifugally washed and soaked with deionized water until the washing liquid was neutral. The product was freeze-dried again to obtain an Ag@GO composite material.

[0128] The Ag@GO composite material was mixed with epoxy resin at a mass ratio of 4:6 to obtain a graphene high-thermal-conductivity composite slurry.

[0129] Experiments and data

[0130] The graphene high-thermal-conductivity composite paste prepared in the above examples and comparative examples was subjected to thermal conductivity and life test in an oxidation environment, and the specific test method was as follows:

[0131] The thermal conductivity test standard was carried out according to GB / T22588-2008, and the unit was W / (m·K).

[0132] The life test of oxidation resistance: the test had no significant effect on the graphene high-thermal-conductivity composite paste, therefore, the Ag@GO composite material before preparation was used for the test, the Ag@GO composite material was subjected to heat treatment at 150℃ and 180℃ for 48h, and then the thermal conductivity was tested according to the standard of GB / T22588-2008.

[0133] The experimental data after the thermal conductivity test is shown in Table 1:

[0134]

[0135] The experimental data of the life test of oxidation resistance is shown in Table 2:

[0136]

[0137] The data of the above Table 1 and Table 2 were plotted, as shown in Figure 1 and Figure 2 .

[0138] Analysis and conclusion

[0139] From the data in Table 1 and Table 2, it can be seen that the Ag@GO composite material and the graphene high-thermal-conductivity composite paste prepared in the examples 1-3 have strong thermal conductivity and oxidation resistance, and can retain sufficient thermal conductivity at high temperature.

[0140] According to the data in Table 1 and Table 2, the thermal conductivity of Comparative Example 1 is low, but the thermal conductivity retention rate is high, and the difference between Comparative Example 1 and the present application is that MXene is not used as the substrate for arranging silver nanoparticles, therefore, it cannot be removed when etched by HF solution in the subsequent process, but it has good oxidation resistance, which can prove that the carbon network formed by graphene and nanocarbon layer has extremely high thermal conductivity efficiency, which can greatly improve the cooperation effect of graphene and silver nanoparticles.

[0141] The data of Comparative Example 2 shows that the thermal conductivity is extremely low, and the thermal conductivity retention rate shows a small decrease, and the difference between Comparative Example 2 and the present application is that it does not undergo secondary hydrothermal reaction, and its effect is to enhance the connection between the graphene material and the nanocarbon layer as a carbon cement, which has a great influence on the formation of three-dimensional porous carbon material, and can significantly affect the thermal conductivity of the material.

[0142] The data of Comparative Example 3 shows that the thermal conductivity is low, but the thermal conductivity retention rate is excellent, and the difference between Comparative Example 3 and the present application is that the hydrothermal carbonization uses a higher temperature and time, which can prove that excessive hydrothermal carbonization reaction can form a continuous carbon layer, thus hindering the etching of the subsequent HF solution, resulting in the absence of a three-dimensional porous network, thus unable to achieve good thermal conduction effect, but forming good oxidation resistance.

[0143] The data of Comparative Example 4 shows that the thermal conductivity is very poor, and the thermal conductivity retention rate also decreases seriously, and the difference between Comparative Example 4 and the present application is that the hydrothermal carbonization uses a too low temperature and time, so the formation degree of carbon nanolayer is small, so it cannot form effective connection with graphene, and after subsequent centrifugal washing operation, it is completely impossible to form a graphene / carbon network, so silver is also not loaded on the surface of graphene in large quantities and uniformly, so it will appear winding and agglomeration, which can prove that suitable hydrothermal carbonization temperature and time can perfectly form a three-dimensional hole expansion network.

[0144] The data of Comparative Example 5 shows that the thermal conductivity is the worst, and the thermal conductivity retention rate shows a moderate decrease, which uses a higher concentration of HF solution, and the thermal conductivity of Comparative Example 6 is relatively good, and has a good thermal conductivity retention rate, which proves that a suitable HF solution concentration can perfectly etch a good three-dimensional porous material, and too high concentration will damage the connection between graphene and carbon nanolayer, and too low concentration will make MXene unable to be removed, and the cavity will become a void, making it difficult to conduct heat.

[0145] The data of Comparative Example 7 shows that its thermal conductivity is moderate, and the thermal conductivity retention rate is the best, and the difference between Comparative Example 7 is that no tert-butyl alcohol is replaced, so it can be known that the replacement of tert-butyl alcohol has a certain effect on the retention of the three-dimensional porous network, and the use of no tert-butyl alcohol leads to the collapse and shrinkage of the pore, so that the void is exposed less, thus having the strongest oxidation resistance and the best thermal conductivity retention.

[0146] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Without deviating from the principles of the present application, those skilled in the art can make equivalent changes or replacements to related technical features, and the technical solutions after these changes or replacements will fall within the protection scope of the present application.

Claims

1. A method for preparing a graphene high thermal conductivity composite slurry, characterized in that, The preparation steps include the following: S1. Place Ti3AlC2 powder in HF solution and stir to react. After the reaction is complete, wash until neutral and place in ice water for ultrasonic treatment. Centrifuge and take the supernatant to obtain MXene dispersion. Add AgNO3 solution to MXene dispersion to react and obtain MXene / Ag composite dispersion. S2. Dissolve glucose in MXene / Ag composite dispersion by ultrasonication, then heat to 155-180℃ for hydrothermal reaction for 2-4 hours. After the reaction is completed, perform post-processing to obtain carbon-modified powder. S3. Disperse and mix carbon-modified powder and graphene oxide in deionized water for 3-6 hours, then add glucose and heat to 155-180℃ for hydrothermal reaction for 5-7 hours. After the reaction is completed, perform displacement and drying in sequence to obtain three-dimensional aerogel solid particles. S4. The three-dimensional aerogel solid particles were placed in an HF solution with a volume concentration of 5-15% and reacted for 18-30 hours. After washing and soaking, Ag@GO composite material was obtained. S5. Mix Ag@GO composite material with epoxy resin to obtain graphene high thermal conductivity composite slurry.

2. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The Ti3AlC2 powder in S1 has a particle size of 200-400 mesh, the reaction time is 24-36 h, the volume concentration of the HF solution is 40%, the centrifugation speed is 3500 rpm, and the concentration of the MXene dispersion is controlled at 5 mg / mL.

3. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The concentration of AgNO3 solution in S1 is 10 mM, the volume ratio of MXene dispersion to AgNO3 solution is 4:1, and the reaction time of MXene dispersion and AgNO3 solution is 12-24 h.

4. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The solid-liquid ratio of glucose to MXene / Ag composite dispersion in S2 is 80-100 mg: 50 mL.

5. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The post-processing operation in S2 includes natural cooling, centrifugal washing, and vacuum drying, wherein the vacuum drying temperature is 60°C.

6. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The mass ratio of carbon-modified powder, graphene oxide, and glucose in S3 is 2.0-2.5:1:1, and the dispersion concentration of graphene oxide is 1-2 mg / mL.

7. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The solution used for the replacement of the three-dimensional aerogel solid particles in S3 is tert-butanol.

8. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The drying method in S3 is supercritical CO2 drying or freeze-vacuum drying.

9. The method for preparing a graphene high thermal conductivity composite slurry according to claim 1, characterized in that, The mass ratio of Ag@GO composite material to epoxy resin in S5 is 3-6:4-7.

10. A graphene high thermal conductivity composite slurry prepared by the preparation method of a graphene high thermal conductivity composite slurry according to any one of claims 1-9.

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