Magnetic field induction and non-solvent induced phase separation synergistic composite film with high vertical thermal conductivity and preparation method of magnetic field induction and non-solvent induced phase separation synergistic composite film

Abstract

The invention belongs to the technical field of heat-conducting composite materials, and particularly relates to a high-vertical-heat-conductivity composite film with synergic magnetic field induction and non-solvent induced phase separation and a preparation method thereof. The method comprises the following steps: performing in-situ growth of magnetic nanoparticles on the surface of a two-dimensional material by a hydrothermal synthesis method, and performing magnetic response modification; dispersing the modified two-dimensional material in a polymer solution, and realizing the vertical orientation of the material at the micro-scale under the action of an external vertical magnetic field, namely the orientation of a two-dimensional lamellar layer; immersing the mixed system into a poor solvent coagulating bath of a polymer solution under the condition of keeping the action of a vertical magnetic field, and inducing two-dimensional material synergistic assembly through non-solvent-induced phase separation of a polymer to obtain a vertically oriented polymer / two-dimensional material porous skeleton; and filling the flexible elastic polymer matrix into the porous skeleton by adopting a vacuum impregnation process to obtain the high-thermal-conductivity polymer / two-dimensional material composite film. The composite film is suitable for heat dissipation of electronic devices, energy storage systems and other occasions needing efficient vertical heat conduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermally conductive composite materials, and in particular relates to a high vertical thermal conductivity film and a preparation method thereof. Background Art

[0002] In recent years, as electronic components continue to develop towards high integration and high power, the large amount of heat generated during operation has become a serious challenge to device reliability. In order to effectively dissipate heat, the industry is in urgent need of high thermal conductivity composite materials. Adding high thermal conductivity two-dimensional materials such as graphene and boron nitride to a polymer matrix is ​​an effective means to improve the thermal conductivity of composite materials. Two-dimensional materials have unique anisotropy, and their in-plane thermal conductivity is even better. The improvement of thermal conductivity of disordered two-dimensional materials is very limited. Traditional blending methods face the problems of low filler orientation and discontinuous thermal conduction paths. Therefore, how to promote the orderly orientation of two-dimensional materials has become the focus and difficulty of fully utilizing high thermal conductivity two-dimensional materials.

[0003] The present invention constructs a two-dimensional material skeleton with multi-scale ordered orientation in the vertical direction through multi-scale collaborative orientation of magnetic field (microscopic layers) + phase separation (macroscopic skeleton), effectively enhancing the continuity of the heat conduction path and improving the vertical thermal conductivity of the material, providing an innovative solution for the thermal management of electronic devices, which has important scientific research significance and practical application value. Summary of the Invention

[0004] The purpose of the present invention is to provide a high vertical thermal conductivity polymer composite film based on the synergistic effect of magnetic field induction and non-solvent induced phase separation and a preparation method thereof, so as to overcome the shortcomings of existing two-dimensional film materials.

[0005] The present invention provides a method for preparing a high vertical thermal conductivity composite film based on the synergistic effect of magnetic field induction and non-solvent induced phase separation, comprising the following steps:

[0006] (1) In situ growth of magnetic nanoparticles on the surface of two-dimensional materials by hydrothermal synthesis to achieve magnetic responsiveness modification;

[0007] (2) dispersing the modified two-dimensional material in a polymer solution to obtain a mixed slurry;

[0008] (3) Achieving microscopic vertical orientation of materials, i.e., orientation of two-dimensional sheets, under the action of an external vertical magnetic field;

[0009] (4) immersing the mixed system in a poor solvent coagulation bath of the polymer solution while maintaining the vertical magnetic field, thereby inducing the coordinated assembly of the two-dimensional material through the non-solvent induced phase separation of the polymer to obtain a vertically oriented polymer / two-dimensional material porous skeleton;

[0010] (5) A vacuum impregnation process is used to fill the flexible and elastic polymer matrix into the porous skeleton, and finally a high thermal conductivity polymer / two-dimensional material composite film with a vertically oriented two-dimensional material network is obtained.

[0011] This invention, through the multi-scale coordinated orientation of a magnetic field (microscopic lamellae) and phase separation (macroscopic skeleton), constructs a two-dimensional material framework with multi-scale ordered orientation in the vertical direction (i.e., vertical orientation of the two-dimensional lamellae at the microscopic level and vertical orientation of the two-dimensional material framework at the macroscopic level). This effectively enhances the continuity of the thermal conductivity pathway and further produces a composite film material with excellent vertical thermal conductivity. This overcomes the technical bottleneck of low orientation of thermally conductive fillers in traditional processes and achieves the multi-scale coordinated construction of a thermal network. This invention has important scientific value for the design and preparation of thermal management materials and is suitable for applications requiring efficient vertical thermal conductivity, such as electronic device heat dissipation and energy storage systems.

[0012] Furthermore, the specific operations are as follows:

[0013] (1) Taking 1.2-4.8 g of the two-dimensional material, in situ growing magnetic particles on the surface of the two-dimensional material by a hydrothermal method, and obtaining a magnetically modified two-dimensional material powder after centrifugation and drying;

[0014] (2) 5-20 mL of solvent A was measured, 0.8-1.2 g of polymer B was added, and after fully dissolved, 0.5-1.5 g of the magnetically modified two-dimensional material was added and stirred thoroughly to obtain a mixed slurry;

[0015] (3) applying the mixed slurry obtained in step (2) to a flat mold by blade coating to obtain a wet film with a thickness of 200-400 μm, transferring the mold coated with the wet film to a vertical magnetic field with a magnetic field strength of 0.1T-1T, and maintaining it for 5-100 minutes to fully induce magnetic field orientation to complete microscopic vertical orientation, i.e., orientation of two-dimensional sheets;

[0016] (4) While maintaining a perpendicular magnetic field, immersing the wet film in a non-solvent coagulation bath of the polymer solution to undergo non-solvent-induced phase separation, thereby achieving vertical orientation on a macroscale, i.e., vertical orientation of the polymer / two-dimensional material porous framework. The wet film rapidly solidifies to form a porous film, which is then removed from the mold, washed, and dried to yield a polymer / two-dimensional material framework with a multi-scale vertically oriented structure.

[0017] (5) Preparation of composite film: the above-mentioned two-dimensional material skeleton is compounded with polymer C by vacuum impregnation to obtain a dense thermal conductive composite film material with a vertically oriented polymer / two-dimensional material skeleton.

[0018] Further:

[0019] In step (1), the magnetic particles are at least one of ferroferric oxide, cobalt ferrite, nickel ferrite, cobalt nanoparticles or nickel nanoparticles.

[0020] In step (1), the two-dimensional material is at least one of graphene, boron nitride, boron arsenide, Mxene or molybdenum disulfide.

[0021] In step (2), the solvent A is at least one of N,N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone.

[0022] In step (2), the polymer B material is at least one of polyacrylonitrile, polyvinylidene fluoride, thermoplastic polyurethane or polyimide.

[0023] In step (4), the coagulation bath is a poor solvent for polymer B in step (2) that has better miscibility with solvent A in step (2).

[0024] In step (5), the flexible and elastic polymer C is at least one of polyurethane, polyacrylate, polyvinyl alcohol, epoxy resin or silicone rubber.

[0025] The present invention uses a multi-scale synergistic orientation of magnetic field (microscopic lamellae) + phase separation (macroscopic skeleton) to construct a two-dimensional material skeleton with multi-scale ordered orientation in the vertical direction (i.e., the vertical orientation of the two-dimensional lamellae at the microscopic level and the vertical orientation of the two-dimensional material skeleton at the macroscopic level). This effectively enhances the continuity of the thermal conduction path and further produces a composite film material with excellent vertical thermal conductivity. This overcomes the technical bottleneck of low orientation of thermal conductive fillers in traditional processes, realizes the multi-scale synergistic construction of the thermal network, and has a simple preparation process. The present invention has important scientific value for the design and preparation of thermal management materials and is suitable for occasions requiring efficient vertical thermal conductivity, such as electronic device heat dissipation and energy storage systems.

[0026] The thermally conductive material obtained by this method, which is a composite of a graphene skeleton and a flexible polymer, has a vertical thermal conductivity of 33.2W / mK, which is higher than the 5-10W / mK of currently common thermally conductive composite materials. It has demonstrated excellent heat dissipation effects in actual heat dissipation tests of microcomputer central processing units (CPUs). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope image of the graphene sheet after magnetic modification in Example 1 with ferrosoferric oxide particles in situ grown on the surface.

[0028] Figure 2 These are the vibrating sample magnetometer curves (VSM curves) of ferrosoferric oxide particles (Fe3O4), unmodified graphene (Graphene) and magnetically modified graphene (m-Graphene) in Example 1.

[0029] Figure 3 This is a scanning electron microscope image of the graphene skeleton with a multi-scale vertical ordered structure in Example 1. (b) is a high-magnification image of (a).

[0030] Figure 4 The wide-angle X-ray scattering azimuthally integrated spectrum (WAXS) of the polyacrylonitrile / graphene skeleton in Example 1 and the corresponding orientation factor.

[0031] Figure 5 These are the appearance photos and scanning electron microscope images of the polymer / graphene composite film obtained by filling the graphene skeleton with silicone rubber in Example 1. (a) is the appearance photo of the polymer / graphene composite film, and (b) is the scanning electron microscope image of the polymer / graphene composite film.

[0032] Figure 6 is the thermal conductivity in the vertical direction of the polymer / graphene composite film in Example 1.

[0033] Figure 7 These are the thermal expansion curve and nanoindentation curve of the polymer / graphene composite film in Example 1.

[0034] Figure 8 This is the change in CPU core temperature when the polymer / graphene composite film in Example 1 is used for CPU heat dissipation.

[0035] Figure 9 This is a scanning electron microscope image of the graphene skeleton with a multi-scale vertical ordered structure in Example 2. (b) is a high-magnification image of (a).

[0036] Figure 10 is the thermal conductivity in the vertical direction of the polymer boron nitride composite film in Example 2. DETAILED DESCRIPTION

[0037] The present invention is further described below by way of examples with reference to the accompanying drawings. However, the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified. The raw materials described can be obtained from publicly available commercial sources unless otherwise specified.

[0038] Example 1,

[0039] First, 2.4 g of graphene powder, 3.6 g of anhydrous sodium acetate (NaAC), 1 g of polyethylene glycol (PEG, Mw = 2000), and 1.2 g of ferric chloride hexahydrate (FeCl3·6H2O) were evenly dispersed in 50 ml of ethylene glycol. The above solution was transferred to a hydrothermal autoclave and reacted at 200°C for 12 h. The magnetically modified graphene powder was obtained by filtration and drying.

[0040] 1.0 g of polyacrylonitrile powder (PAN, Mw = 250,000) was stirred and fully dissolved in 10 mL of dimethyl sulfoxide, and then 1.0 g of the magnetically modified graphene powder obtained above was added and stirred for 1 h to fully mix;

[0041] The mixed solution obtained above was applied by doctor blade onto a flat substrate to form a wet film approximately 200 μm thick. This wet film was then placed in a perpendicular magnetic field formed by two parallel neodymium magnets for 2 minutes. While maintaining the perpendicular magnetic field, the wet film was immersed in a room temperature water bath for non-solvent-induced phase separation. After 2 minutes, the cured porous membrane was peeled from the substrate, washed with ethanol and n-hexane, and then dried in a 60°C oven, resulting in a polyacrylonitrile / graphene framework with a multi-scale vertically oriented structure. This framework was then composited with silicone rubber by vacuum impregnation to form a polymer / graphene composite film.

[0042] Figure 1 Demonstrated in situ growth of graphene sheets with Fe3O4 particles on the surface;

[0043] Figure 2 The vibrating sample magnetometer curve (VSM curve) of magnetically modified graphene (m-Graphene) is shown. The modified graphene has magnetic responsiveness.

[0044] like Figure 3 As shown, the cross-sectional SEM image of the polyacrylonitrile / graphene skeleton shows that the two-dimensional sheets in the skeleton have a multi-scale vertical orientation structure, that is, each graphene sheet is oriented in the vertical direction at the microscopic level, and the graphene skeleton is oriented in the vertical direction at the macroscopic level;

[0045] Figure 4 Wide-angle X-ray scattering azimuthally integrated spectra (WAXS) of polyacrylonitrile / graphene frameworks prepared by different preparation processes and their corresponding orientation factors are presented. The multi-scale vertical polyacrylonitrile / graphene frameworks constructed by the synergistic construction of magnetic field-induced and non-solvent-induced phase separation have a larger orientation factor.

[0046] like Figure 5 As shown, the prepared polymer / graphene composite film has a black appearance, and the cross-sectional SEM image shows that the polymer can completely fill the gaps in the skeleton to obtain a dense composite material;

[0047] Figure 6 The vertical thermal conductivity of pure polymer films and polymer / graphene composite films was demonstrated, and the introduction of vertically ordered graphene skeletons effectively improved the thermal conductivity.

[0048] Figure 7 It was demonstrated that polymer / graphene composite films have low thermal expansion coefficient and good compression properties;

[0049] Figure 8 The core temperature curve when the polymer / graphene composite film is used as the thermal interface material of the CPU is shown. It can be seen that after using the polymer / graphene composite film, the core temperature of the CPU running at full load can be reduced by 31°C compared to when no thermal interface material is used.

[0050] Example 2,

[0051] First, 60 mL of ethylene glycol and 7.2 g of BN (boron nitride) were mixed and stirred by ultrasonication until uniform. Then, 2.4 g of ferric chloride hexahydrate, 7.2 g of anhydrous sodium acetate, and 2 g of polyethylene glycol were added and fully dissolved and stirred. The mixture was transferred to a hydrothermal autoclave and kept at 200 ° C for 12 h. The mixture was filtered, washed, and dried to obtain magnetically responsive boron nitride.

[0052] Then, 1 g of polyacrylonitrile powder was stirred with 9 mL of dimethyl sulfoxide and fully dissolved, and then 1.5 g of magnetically responsive boron nitride was added and continued to stir and ultrasonicate until fully dissolved;

[0053] The evenly mixed casting solution was scraped onto a glass substrate with a thickness of 120 μm and immersed in an aqueous solution with a pre-set uniform magnetic field of 100 mT perpendicular to the horizontal plane to obtain a BN / polyacrylonitrile skeleton with a multi-scale vertically oriented structure.

[0054] The silicone rubber is compounded with the skeleton through vacuum impregnation to obtain a polymer / boron nitride composite film.

[0055] Figure 9 The cross-sectional SEM image of the BN / polyacrylonitrile skeleton after carbonization shows a multi-scale vertically oriented structure. The BN sheets are tightly attached to the pore walls, and the overall orientation degree is high.

[0056] Figure 10 The out-of-plane thermal conductivity of pure silicone rubber film and the film obtained by filling silicone rubber with BN / polyacrylonitrile framework is shown.

Claims

1. A method for preparing a high vertical thermal conductivity composite film by synergistic magnetic field-induced and non-solvent-induced phase separation, characterized in that: The specific steps are: (1) In situ growth of magnetic nanoparticles on the surface of two-dimensional materials by hydrothermal synthesis to achieve magnetic responsiveness modification; (2) dispersing the modified two-dimensional material in a polymer solution to obtain a mixed slurry; (3) Achieving microscopic vertical orientation of materials, i.e., orientation of two-dimensional sheets, under the action of an external vertical magnetic field; (4) Under the condition of maintaining the vertical magnetic field, the mixed system is immersed in a poor solvent coagulation bath of the polymer solution, and the non-solvent-induced phase separation of the polymer induces the coordinated assembly of the two-dimensional material to obtain a vertically oriented polymer / two-dimensional material porous skeleton; (5) A vacuum impregnation process is used to fill the above-mentioned porous skeleton with a flexible and elastic polymer matrix, and finally a high thermal conductivity polymer / two-dimensional material composite film with a vertically oriented two-dimensional material network is obtained.

2. The preparation method according to claim 1, characterized in that The specific operation process is as follows: (1) Take 1.2-4.8g of two-dimensional material, grow magnetic particles in situ on the surface of the two-dimensional material by hydrothermal method, and obtain magnetically modified two-dimensional material powder after centrifugation and drying; (2) Measure 5-20 mL of solvent, add 0.8-1.2 g of polymer material, and after fully dissolving, add 0.5-1.5 g of magnetically modified two-dimensional material and stir thoroughly to obtain a mixed slurry; (3) The mixed slurry obtained in step (2) is applied to a flat mold by scraping to obtain a wet film with a thickness of 200-400 μm, and the mold coated with the wet film is transferred to a vertical magnetic field with a magnetic field strength of 0.1T-1T and maintained for 5-100 minutes to fully induce magnetic field orientation and complete microscopic vertical orientation, that is, orientation of two-dimensional sheets; (4) While maintaining the vertical magnetic field, the wet film is immersed in a non-solvent coagulation bath of the polymer solution to perform a non-solvent-induced phase separation process, thereby completing the vertical orientation on a macroscopic scale, i.e., the vertical orientation of the polymer / two-dimensional material porous skeleton. At this time, the wet film is rapidly solidified to obtain a porous film, which is removed from the mold, washed, and dried to obtain a polymer / two-dimensional material skeleton with a multi-scale vertical orientation structure. (5) Preparation of composite film: the above-mentioned two-dimensional material skeleton is compounded with a polymer by vacuum impregnation to obtain a dense thermal conductive composite film material with a vertically oriented polymer / two-dimensional material skeleton.

3. The preparation method according to claim 2, characterized in that The magnetic particles in step (1) are at least one of ferroferric oxide, cobalt ferrite, nickel ferrite, cobalt nanoparticles, and nickel nanoparticles; and the two-dimensional material is at least one of graphene, boron nitride, boron arsenide, Mxene, or molybdenum disulfide.

4. The preparation method according to claim 2, characterized in that The solvent in step (2) is at least one of N,N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone; and the polymer material is at least one of polyacrylonitrile, polyvinylidene fluoride, thermoplastic polyurethane or polyimide.

5. The preparation method according to claim 2, characterized in that The coagulation bath in step (4) is a poor solvent for the polymer in step (2) that has better miscibility with the solvent in step (2).

6. The preparation method according to claim 2, characterized in that The flexible and elastic polymer in step (5) is at least one of polyurethane, polyacrylate, polyvinyl alcohol, epoxy resin or silicone rubber.

7. A composite film with high vertical thermal conductivity obtained by the preparation method according to any one of claims 1 to 6.

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