Double-sided oriented Janus structure heat-conducting soaking film and preparation method thereof

Abstract

The invention relates to the technical field of functional film materials, in particular to a double-sided oriented Janus structure heat-conducting soaking film and a preparation method thereof. The preparation method of the double-sided oriented Janus structure heat-conducting soaking film comprises the following steps: preparing a carbon fiber dispersion liquid; directional forming of the carbon fiber dispersion liquid is carried out, and at least one part of carbon fibers in the carbon fiber directional layer protrude out of the upper surface of the carbon fiber directional layer; preparing a graphene dispersion liquid; graphene dispersion liquid is dropped into the upper surface of the oriented carbon fiber film, and then oriented forming is performed, so that at least one part of the carbon fibers protruding out of the upper surface of the carbon fiber oriented layer are inserted into the graphene oriented layer. According to the double-sided directional Janus structure heat-conducting soaking film provided by the invention, a heat-conducting material can have high in-plane heat conductivity and high inter-plane heat conductivity, so that the problems that heat distribution is not uniform and local hot spots are difficult to dissipate heat in heat dissipation of an electronic device are solved.

Description

Technical Field

[0001] This invention relates to the field of functional thin film materials technology, and in particular to a double-sided oriented Janus structure thermally conductive and heat-spreading film and its preparation method. Background Technology

[0002] Modern chips integrate enormous computing power onto a tiny area through advanced packaging, but power consumption is also concentrated in a very small area (such as the core area of ​​a CPU / GPU), forming "hot spots" with extremely high power density (potentially exceeding 1000 W / cm²). 2 While the power density in other areas of the chip may be very low, traditional heat dissipation designs assume that the heat source is uniform. However, local hot spots lead to highly concentrated heat flow, forming huge lateral and longitudinal temperature gradients. Currently, heat dissipation for local hot spots in high-power electronic chips is mainly achieved through high-performance thermal interface materials. Traditional high-performance thermal interface materials generally include liquid metals, thermally conductive graphene / nanomaterial films, and thermally conductive silicone grease. Although liquid metals have extremely high thermal conductivity (~20-80 W / (m·K)) and can fill tiny gaps, their conductivity and corrosiveness will affect electronic components. Thermally conductive graphene / nanomaterial films have anisotropic thermal conductivity, with their in-plane thermal conductivity being much higher than their inter-plane thermal conductivity.

[0003] Existing thermal conductive films typically only possess high in-plane thermal conductivity or high inter-plane thermal conductivity, which often makes it difficult to solve the problem of "local hot spots". Therefore, it is of great significance to enable composite materials to have high inter-plane thermal conductivity for heat dissipation, while also having high in-plane thermal conductivity for heat uniformity. Summary of the Invention

[0004] To address the problem that existing thermally conductive films often lack both high in-plane thermal conductivity and high inter-plane thermal conductivity, this invention provides a double-sided oriented Janus structure thermally conductive and heat-spreading film and its preparation method.

[0005] To address the aforementioned technical problems, one of the technical solutions provided by this invention is as follows: A method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film includes the following steps: Prepare carbon fiber dispersion; The carbon fiber dispersion is transferred to a non-magnetic container, and an external magnetic field perpendicular to the bottom surface of the non-magnetic container is applied to make the carbon fiber vertically oriented. Then, the dispersion is dried so that the oriented carbon fiber dispersion changes from a liquid state to a carbon fiber oriented layer that is solid at the bottom and not yet solidified on the surface. Then, the non-magnetic container is removed from the magnetic field. The carbon fiber orientation layer has an upper surface and a lower surface opposite to each other; the lower surface is in contact with the bottom surface of the container, and at least a portion of the carbon fibers in the carbon fiber orientation layer protrude from the upper surface of the carbon fiber orientation layer; Prepare a graphene dispersion; The graphene dispersion is added to a non-magnetic container containing the carbon fiber orientation layer, and an external magnetic field parallel to the bottom surface of the non-magnetic container is applied to make the graphene horizontally oriented. Then, the graphene dispersion is dried so that the orientation layer is formed and the carbon fiber dispersion that was not in a solid state is converted into a solid state. At least a portion of the carbon fibers protruding from the upper surface of the carbon fiber orientation layer are inserted into the interior of the graphene orientation layer.

[0006] In one embodiment of the present invention, the method for preparing the carbon fiber dispersion includes: Prepare polymer matrix solutions; Carbon fibers and plasticizers are added to the polymer matrix solution and mixed.

[0007] In one embodiment of the present invention, the mass ratio of the carbon fiber to the polymer matrix solution is (1-4):10; and / or The mass ratio of the plasticizer to the polymer matrix solution is (1-2):50.

[0008] In one embodiment of the present invention, the polymer matrix is ​​polyvinyl alcohol; and / or The plasticizer is glycerol.

[0009] In one embodiment of the present invention, the length of the carbon fiber is more than 120 μm and less than 180 μm.

[0010] In one embodiment of the present invention, the thickness of the carbon fiber orientation layer is 0.5 mm or more and 1.0 mm or less; The thickness of the graphene orientation layer is greater than 0.25 mm and less than 0.5 mm; In a preferred embodiment of the present invention, the thickness of the graphene orientation layer is half the thickness of the carbon fiber orientation layer.

[0011] In one embodiment of the present invention, a method for preparing a graphene dispersion includes: Prepare polymer matrix solutions; Graphene and plasticizer are added to the polymer matrix solution and mixed.

[0012] In one embodiment of the present invention, the mass ratio of the carbon fiber to the polymer matrix solution is (1-3):10; and / or The mass ratio of the plasticizer to the polymer matrix solution is (1-2):50.

[0013] In one embodiment of the present invention, the graphene sheet diameter is greater than 7 μm and less than 10 μm.

[0014] The second technical solution provided by this invention is as follows: A double-sided oriented Janus structure thermally conductive and heat-spreading film prepared by the method described above.

[0015] This invention employs a magnetic field orientation method and a method for constructing a bifacial heterostructure to create a carbon fiber-graphene bifacially oriented reinforced thermally conductive and heat-dissipating Janus structure composite material. This invention innovatively constructs a Janus... A structural method was employed to prepare a bi-directionally reinforced, thermally conductive, and heat-monopolizing Janus structure composite material of carbon fiber and graphene films by magnetically oriented them. On one hand, the magnetic field orientation of the graphene and carbon fiber films creates directional heat-conducting channels, significantly improving thermal conductivity. On the other hand, the Janus structure allows for synergistic effects between the lateral heat homogenization of the polyvinyl alcohol (PVA) / graphene nanoplatelets (GNP) layer and the longitudinal heat conduction of the PVA / carbon fiber (CF) layer, overcoming the limitations of heat diffusion in single-oriented materials. This bi-directionally reinforced, thermally conductive, and heat-monopolizing Janus structure composite material constructs a synergistic "in-plane diffusion-out-plane extraction" heat-conducting network within the PVA matrix, resulting in a PVA-based thermally conductive composite material (PVA / GNP / CF composite material) that possesses both thermal conductivity and heat homogenization capabilities. This material is particularly valuable for the thermal management of high-power electronic devices with localized hot spots, demonstrating significant application potential.

[0016] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other beneficial effects of the invention can be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Unless otherwise specified, the positional relationships shown in the drawings in the following description are based on the direction in which the components are drawn in the figure.

[0018] Figure 1 The in-plane and inter-plane thermal conductivity of the carbon fiber film and the graphene film prepared in Example 1 are shown. Figure 2 (a) shows the distribution of GNP and CF in the PVA / GNP / CF composite material prepared in Example 1, (b) is a cross-sectional SEM image of the CF layer, and (c) is a cross-sectional SEM image of the GNP layer. Figure 3 The images show (a) and (b) of the actual sample of the CF film prepared in Example 1 after being oriented by a vertical magnetic field. Figure 4 Images (a), (b), (c), and (d) are cross-sectional SEM images of the carbon fiber-graphene composite film prepared in Example 1. Figure 5 The surface temperature distribution of the sample prepared in Example 1 after contact with a heat source for 1s, 10s, and 20s. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0021] Those skilled in the art will understand that the order in which the steps are written in the various implementations or embodiments does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps 1 and 2, it means that the method may include steps 1 and 2 performed sequentially, or it may include steps 2 and 1 performed sequentially. For example, if the method may also include step 3, it means that step 3 can be added to the method in any order. For example, the method may include steps 1, 2, and 3, or it may include steps 1, 3, and 2, or it may include steps 3, 1, and 2, etc.

[0022] An embodiment of the present invention provides a method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film, comprising the following steps: Step 1: Prepare carbon fiber dispersion; In step 1 of this embodiment, the method for preparing the carbon fiber dispersion includes: S1, preparing a polymer matrix solution; and S2, adding carbon fiber and plasticizer to the polymer matrix solution and mixing.

[0023] In specific implementation of step S1, the polymer matrix is ​​preferably polyvinyl alcohol (molecular weight 205000). First, polyvinyl alcohol is dissolved in deionized water, and then heated and stirred in a water bath to obtain a uniform polymer matrix solution. It is worth noting that when preparing the polymer matrix solution, the polyvinyl alcohol with a molecular weight of 205,000 is mixed with deionized water in a ratio of (1-10):100, for example, 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, or any range of the above values, wherein the polyvinyl alcohol is calculated by mass (g) and the deionized water is calculated by volume (ml); the water bath heating temperature is 90°C, and the stirring time can be 2h~6h, for example, 2h, 3h, 4h, 5h, 6h, or any range of the above values.

[0024] In specific implementation of step S2, the plasticizer is glycerol. First, carbon fibers and glycerol are added to the polymer matrix solution obtained in step S1, and then completely dissolved under magnetic stirring to obtain a carbon fiber dispersion. The mass ratio of the carbon fibers to the polymer matrix solution is (1-4):10, for example, 1:10, 2:10, 3:10, 4:10, or any value within the range above. The mass ratio of the plasticizer to the polymer matrix solution is (1-2):50, for example, 1:50, 1.2:50, 1.4:50, 1.6:50, 1.8:50, 2:50, or any value within the range above.

[0025] In a preferred embodiment of the present invention, the length of the carbon fiber is greater than 120 μm and less than 180 μm, for example 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm or within any of the above values.

[0026] The thickness of the carbon fiber oriented layer is greater than 0.5 mm and less than 1.0 mm, for example, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, or within any range of the above values; the thickness of the graphene oriented layer is greater than 0.25 mm and less than 0.5 mm, for example, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or within any range of the above values.

[0027] The length of the carbon fiber is preferably 150mm-180mm, so that it has a suitable length when combined with an appropriate carbon fiber orientation layer thickness (0.5mm-0.75mm) so that at least a portion of the carbon fiber protrudes from the upper surface of the carbon fiber orientation layer after orientation molding.

[0028] Step 2: Transfer the carbon fiber dispersion to a non-magnetic container, apply an external magnetic field perpendicular to the bottom of the non-magnetic container to make the carbon fibers vertically oriented, and then dry it so that the oriented carbon fiber dispersion changes from a liquid state to a carbon fiber orientation layer that is solid at the bottom and not yet solidified on the surface. Then remove the non-magnetic container from the magnetic field.

[0029] In practice, an appropriate amount of carbon fiber dispersion is dropped into a polytetrafluoroethylene container (mold), and then the container is placed under a vertical magnetic field with a magnetic field strength of 0.4T for 24-48 hours for orientation and drying, so that the oriented carbon fiber dispersion changes from a liquid state to a solid state to form a carbon fiber orientation layer. The carbon fiber orientation layer has an upper surface and a lower surface opposite each other; the lower surface is in contact with the bottom surface of the container, and at least a portion of the carbon fibers in the carbon fiber orientation layer protrude from the upper surface of the carbon fiber orientation layer.

[0030] Step 3: Prepare the graphene dispersion; In step 3 of this embodiment, the method for preparing the graphene dispersion includes: S1, preparing a polymer matrix solution; and S2, adding graphene and plasticizer to the polymer matrix solution and mixing.

[0031] In specific implementation of step S1, the polymer matrix is ​​preferably polyvinyl alcohol (molecular weight 205000). First, polyvinyl alcohol is dissolved in deionized water, and then heated and stirred in a water bath to obtain a uniform polymer matrix solution. It is worth noting that when preparing the polymer matrix solution, the polyvinyl alcohol with a molecular weight of 205,000 is mixed with deionized water at a ratio of (1-5):100, for example, 1:100, 2:100, 3:100, 4:100, 5:100 or any range of the above values, wherein the polyvinyl alcohol is calculated by mass (g) and the deionized water is calculated by volume (ml); the water bath heating temperature is 90°C, and the stirring time can be 2h-6h, for example, 2h, 3h, 4h, 5h, 6h or any range of the above values.

[0032] It should be noted that there is no specific order in which the carbon fiber dispersion and the graphene dispersion are prepared, but there is a specific order in which the magnetic field is used for orientation. This order is one of the main innovations of this application. The purpose is to allow the graphene solution to penetrate to the upper surface of the carbon fiber protrusions when the two oriented film layers are composited, so that the two layers are more tightly bonded and have a better thermal conductivity.

[0033] In specific implementation of step S2, the plasticizer is glycerol. Graphene and glycerol are first added to the polymer matrix solution obtained in step S1, and then completely dissolved under stirring with a magnetic stirrer to obtain a graphene dispersion. The mass ratio of graphene to the polymer matrix solution is (1-3):10, for example, 1:10, 2:10, 3:10, or any value within the range above. The mass ratio of the plasticizer to the polymer matrix solution is (1-2):50, for example, 1:50, 1.2:50, 1.4:50, 1.6:50, 1.8:50, 2:50, or any value within the range above.

[0034] In a preferred embodiment of the present invention, the graphene sheet diameter is greater than 7 μm and less than 10 μm, for example 7 μm, 8 μm, 9 μm, 10 μm or within any of the above values.

[0035] Step 4: Add the graphene dispersion to a non-magnetic container containing the carbon fiber orientation layer, apply an external magnetic field parallel to the bottom surface of the non-magnetic container to make the graphene horizontally oriented, and then dry it so that the orientation graphene dispersion changes from a liquid state to a solid state to form a graphene orientation layer and the non-solid carbon fiber dispersion becomes solid.

[0036] In a specific implementation, the obtained graphene dispersion is dropped into a non-magnetic container (mold) containing the carbon fiber orientation layer, and the non-magnetic container is placed under a horizontal magnetic field of 0.4T for 24-48 hours for orientation and drying, so that the orientation graphene dispersion changes from a liquid state to a solid state to form a graphene orientation layer; so that at least a portion of the carbon fibers protruding from the upper surface of the carbon fiber orientation layer are inserted into the interior of the graphene orientation layer.

[0037] This invention presents a carbon fiber-graphene bifacially oriented reinforced thermally conductive and homogeneous Janus structure composite material. The Janus structure is constructed from carbon fiber (CF), graphene nanoplatelets (GNP), and polyvinyl alcohol (PVA), giving it both the excellent in-plane thermal conductivity of graphene films and the excellent inter-plane thermal conductivity of carbon fiber films. The preparation principle involves preparing a carbon fiber film with inter-plane thermal conductive channels under a vertical magnetic field. The carbon fibers are vertically aligned under the influence of the vertical magnetic field, and then dried under the same field until the bottom of the film solidifies while the top surface remains unsolidified. A polyvinyl alcohol (PVA) / graphene composite solution is then poured in and transferred to a horizontal magnetic field. This allows the graphene in the film to construct in-plane oriented thermal conductive channels within the horizontal magnetic field, resulting in a graphene film with high in-plane thermal conductivity. Finally, the film is dried at room temperature to obtain the carbon fiber-graphene bifacially oriented reinforced thermally conductive and homogeneous Janus structure composite material. This material can be used in equipment to solve the problem of "localized hot spots," for example, the instantaneous heat flux density of millimeter-wave power amplifiers can reach 250~350W / cm². 2 The adjacent area has only 50W / cm 2 .

[0038] An embodiment of the present invention provides a double-sided oriented Janus structure thermally conductive and heat-dissipating film prepared as described in the method described above.

[0039] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where the technology or conditions are not specified in the embodiments, they are performed according to the technology or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0040] Example 1 In this embodiment, carbon fiber films and graphene films are prepared by magnetic field orientation method, and a carbon fiber and graphene double-sided oriented reinforced thermally conductive and heat-equalizing Janus structure composite material is prepared by constructing Janus structure. The specific preparation method is as follows: (1) Weigh 2.5g of polyvinyl alcohol (Mw: 205000) and dissolve it in 97.5mL of deionized water. Stir for 120min under a water bath at 90℃ to prepare a 2.5wt% PVA solution.

[0041] (2) Weigh 2g of carbon fiber with an average length of 150μm and 0.25g of glycerol and dissolve them in 10g of 2.5wt% PVA solution and stir for 30min.

[0042] (3) Take 1.5g of the mixed solution obtained in step (2) and drop it into the polytetrafluoroethylene mold, and place the mold in a vertical magnetic field with a magnetic field strength of 0.4T for 36h.

[0043] (4) Weigh 20g of the 2.5wt% PVA solution from step (1) and add an equal mass of deionized water to prepare a 1.25wt% PVA solution.

[0044] (5) Take 10g of the 1.25wt% PVA solution obtained above, add 1.2g of graphene microplates with a diameter of 7~10μm and 0.25g of glycerol, and mix and stir for 30min.

[0045] (6) Take 1.5g of the mixed solution obtained in step (5) and drop it onto the sample surface in step (3).

[0046] (7) Place the sample obtained in step (6) in a horizontal magnetic field with a magnetic field strength of 0.4T for 36 hours.

[0047] (8) Dry the oriented sample in step (7) in the air for 3 days.

[0048] (9) Peel the sample obtained in step (8) off the polytetrafluoroethylene mold.

[0049] Example 2 In this embodiment, carbon fiber films and graphene films are prepared by magnetic field orientation method, and a carbon fiber and graphene bi-sided oriented reinforced thermally conductive and heat-spreading Janus structure composite material is prepared by constructing a bi-sided heterostructure. The specific preparation method is as follows: (1) Weigh 5g of polyvinyl alcohol (Mw: 205000) and dissolve it in 95mL of deionized water. Stir for 180min under a water bath at 90℃ to prepare a 5wt% PVA solution.

[0050] (2) Weigh 3g of carbon fiber with an average length of 150μm and 0.25g of glycerol and dissolve them in 10g of 5wt% PVA solution and stir for 1h.

[0051] (3) Take 1.2g of the mixed solution obtained in step (2) and drop it into the polytetrafluoroethylene mold, and place the mold in a vertical magnetic field with a magnetic field strength of 0.4T for 36h.

[0052] (4) Weigh 20g of the 5wt% PVA solution from step (1) and add an equal mass of deionized water to prepare a 2.5wt% PVA solution.

[0053] (5) Take 10g of the 2.5wt% PVA solution obtained above, add 1.8g of graphene microplates with a diameter of 7~10μm and 0.25g of glycerol, and mix and stir for 1h.

[0054] (6) Take 1.2g of the mixed solution obtained in step (5) and drop it onto the sample surface in step (3).

[0055] (7) Place the sample obtained in step (6) in a horizontal magnetic field with a magnetic field strength of 0.4T for 36 hours.

[0056] (8) Dry the oriented sample in step (7) in the air for 5 days.

[0057] (9) Peel the sample obtained in step (8) off the polytetrafluoroethylene mold.

[0058] Example 3 In this embodiment, carbon fiber films and graphene films are prepared by magnetic field orientation method, and a carbon fiber and graphene bi-sided oriented reinforced thermally conductive and heat-spreading Janus structure composite material is prepared by constructing a bi-sided heterostructure. The specific preparation method is as follows: (1) Weigh 7.5g of polyvinyl alcohol (Mw: 205000) and dissolve it in 92.5mL of deionized water. Stir for 360min under a water bath at 90℃ to prepare a 7.5wt% PVA solution.

[0059] (2) Weigh 3g of carbon fiber with an average length of 150μm and 0.5g of glycerol and dissolve them in 10g of 7.5wt% PVA solution and stir for 2h.

[0060] (3) Take 1g of the mixed solution obtained in step (2) and drop it into the polytetrafluoroethylene mold, and place the mold in a vertical magnetic field with a magnetic field strength of 0.4T for 48h.

[0061] (4) Weigh 5g of polyvinyl alcohol (Mw: 205000) and dissolve it in 95mL of deionized water. Stir the solution for 60min under a water bath at 90℃ to prepare a 5wt% PVA solution.

[0062] (5) Take 10g of the 5wt% PVA solution obtained above, add 2.4g of graphene microplates with a diameter of 7~10μm and 0.5g of glycerol, and mix and stir for 2h.

[0063] (6) Take 1g of the mixed solution obtained in step (5) and drop it onto the sample surface in step (3).

[0064] (7) Place the sample obtained in step (6) in a horizontal magnetic field with a magnetic field strength of 0.4T for 48 hours.

[0065] (8) Dry the oriented sample in step (7) in the air for 7 days.

[0066] (9) Peel the sample obtained in step (8) off the polytetrafluoroethylene mold.

[0067] Figure 1 The interplane and in-plane thermal conductivity of the carbon fiber film and graphene film prepared in Example 1 are presented. Calculations based on the thermal conductivity equation show that the interplane thermal conductivity of the carbon fiber film is 45.47 W / (m·K), and the in-plane thermal conductivity is 1.67 W / (m·K). The interplane thermal conductivity of the graphene film is 1.01 W / (m·K), and the in-plane thermal conductivity is 8.80 W / (m·K). This demonstrates that the graphene film prepared in Example 1 possesses high in-plane thermal conductivity, which allows for uniform heat distribution when bonded to the surface of electronic devices; the carbon fiber film possesses high interplane thermal conductivity, which aids in heat dissipation for electronic devices. Combining the two can achieve directional enhanced thermal conductivity and uniform heat distribution.

[0068] Figure 2 (a) A diagram showing the distribution of GNP and CF in the PVA / GNP / CF composite material prepared in Example 1 is provided. Figure 2 (b) is a cross-sectional SEM image of the GNP layer. It can be seen that the graphene flakes in the graphene film after being oriented by a horizontal magnetic field are roughly parallel to the plane, and in-plane heat conduction channels can be constructed by the orientation of the horizontal magnetic field. Figure 2(c) is a cross-sectional SEM image of the CF layer. It can be seen that the carbon fibers in the carbon fiber film after vertical magnetic field orientation are aligned in the same direction and are all arranged in the vertical direction. Interfacial heat conduction channels can be constructed by vertical magnetic field orientation.

[0069] Figure 3 The CF film prepared in Example 1 is shown in (a) and (b) figures. (a) shows the carbon fiber film after being oriented by a vertical magnetic field and (b) shows the carbon fiber film before being oriented by a magnetic field. It can be observed that the carbon fibers on the upper surface of the carbon fiber film after being oriented by a magnetic field will be vertically aligned under the action of the magnetic field, and the carbon fibers on the upper surface will protrude, which is beneficial to the composite of graphene film layers.

[0070] Figure 4 A cross-sectional SEM image of the graphene carbon fiber film prepared in Example 1 is given. Figure 4 (a) and Figure 4 (b) It can be seen that after the carbon fiber solution is oriented by a vertical magnetic field, the carbon fibers are arranged vertically. Subsequent dripping of graphene solution allows the carbon fibers to interweave within the graphene film, and... Figure 4 (c) and Figure 4 (d) It can be seen that there are some graphene microflakes in the carbon fiber layer, which can make the two more tightly connected, reduce the interfacial thermal resistance between the carbon fiber film and the graphene film, and improve its thermal and mechanical properties.

[0071] Figure 5 The temperature changes of the upper surface of the PVA / CF film, PVA / GNP film, and PVA / GNP / CF film prepared in Example 1 when placed on a circular heat source (positioned in the center) are shown. The temperature distribution of the upper surface of each sample was observed after 1s, 10s, and 20s of contact with the heat source. It was found that the average upper surface temperature of the PVA / GNP / CF composite material was consistently the highest at 1s, 10s, and 20s of contact with the heat source, indicating its optimal overall thermal conductivity. Furthermore, the surface temperature distribution uniformity was similar to that of the PVA / GNP layer; neither exhibited localized heat concentration as observed by infrared thermal imager, and no significant temperature gradient (significantly higher temperature at the center than at the edges) was observed in the PVA / CF layer due to its high interfacial thermal conductivity and low in-facial thermal conductivity. This confirms that the Janus structure overcomes the limitations of thermal diffusion in single-orientation materials (such as PVA / CF films having high longitudinal thermal conductivity but failing to solve the problem of local heat accumulation, and PVA / GNP films having lateral heat homogenization but hindering longitudinal heat transfer) through the synergistic effect of lateral heat homogenization and longitudinal heat conduction of the PVA / CF layer. It significantly improves the overall performance of heat flux density and heat dissipation uniformity, providing an innovative solution for the problem of local hot spots in electronic devices that combines efficient heat conduction and dynamic heat homogenization.

[0072] In summary, this invention prepares a directional thermally conductive and homogenizing heterogeneous composite material by compositing PVA / CF film and PVA / GNP film. Composite the PVA / GNP film onto the PVA / CF film improves the overall in-plane thermal conductivity, resulting in carbon fiber / graphene composites with both high inter-plane and in-plane thermal conductivity. Furthermore, the proportions of each filler can be adjusted to meet different mechanical performance requirements in practical applications. In the preparation of the carbon fiber / graphene directional thermally conductive and homogenizing composite material, an inter-plane thermally conductive PVA / CF film is first prepared, and inter-plane thermal channels are constructed using a vertical magnetic field. After the PVA / CF film has set but is not completely dry, a PVA / GNP composite solution is dropped in to form a carbon fiber / graphene heterostructure, and inter-plane thermal channels are constructed in a horizontal magnetic field, ultimately yielding the carbon fiber / graphene directional thermally conductive and homogenizing composite material. In addition, this invention has advantages such as low cost, ability to meet diverse application needs, and mass production capability, making it highly valuable for application. This invention enables inter-surface thermal conductive materials to have the function of uniform heat distribution, which can solve the problems of uneven heat distribution and difficulty in heat dissipation of local hot spots in electronic devices.

[0073] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0074] Although this document frequently uses terms such as carbon fiber, dispersion, non-magnetic container, external magnetic field graphene, polymer matrix, and plasticizer, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention. The terms "first," "second," etc. (if present) in the specification, claims, and accompanying drawings of the embodiments of the invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film, characterized in that, Includes the following steps: Prepare carbon fiber dispersion; The carbon fiber dispersion is transferred to a non-magnetic container, and an external magnetic field perpendicular to the bottom surface of the non-magnetic container is applied to make the carbon fiber vertically oriented. Then, the dispersion is dried so that the oriented carbon fiber dispersion changes from a liquid state to a carbon fiber oriented layer that is solid at the bottom and not yet solidified on the surface. Then, the non-magnetic container is removed from the magnetic field. The carbon fiber orientation layer has an upper surface and a lower surface opposite to each other; the lower surface is in contact with the bottom surface of the container, and at least a portion of the carbon fibers in the carbon fiber orientation layer protrude from the upper surface of the carbon fiber orientation layer; Prepare a graphene dispersion; The graphene dispersion is added to a non-magnetic container containing the carbon fiber orientation layer, and an external magnetic field parallel to the bottom surface of the non-magnetic container is applied to make the graphene horizontally oriented. Then, the graphene dispersion is dried so that the orientation layer is formed and the carbon fiber dispersion that was not in a solid state is converted into a solid state. At least a portion of the carbon fibers protruding from the upper surface of the carbon fiber orientation layer are inserted into the interior of the graphene orientation layer.

2. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to claim 1, characterized in that, The method for preparing the carbon fiber dispersion includes: Prepare polymer matrix solutions; Carbon fibers and plasticizers are added to the polymer matrix solution and mixed.

3. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to claim 2, characterized in that, The mass ratio of the carbon fiber to the polymer matrix solution is (1-4):10; and / or The mass ratio of the plasticizer to the polymer matrix solution is (1-2):

50.

4. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to claim 2, characterized in that, The polymer matrix is ​​polyvinyl alcohol; and / or The plasticizer is glycerol.

5. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to claim 1, characterized in that, The length of the carbon fiber is greater than 120 μm and less than 180 μm.

6. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to claim 1, characterized in that, The thickness of the carbon fiber orientation layer is greater than 0.5 mm and less than 1.0 mm; The thickness of the graphene orientation layer is greater than 0.25 mm and less than 0.5 mm.

7. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to any one of claims 1-6, characterized in that, Methods for preparing graphene dispersions include: Prepare polymer matrix solutions; Graphene and plasticizer are added to the polymer matrix solution and mixed.

8. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to claim 7, characterized in that, The mass ratio of the graphene to the polymer matrix solution is (1-3):10; and / or The mass ratio of the plasticizer to the polymer matrix solution is (1-2):

50.

9. The method for preparing a double-sided oriented Janus structure thermally conductive and heat-spreading film according to claim 7, characterized in that, The graphene sheet diameter is greater than 7 μm and less than 10 μm.

10. A double-sided oriented Janus structure thermally conductive and heat-dissipating film prepared by the method according to any one of claims 1-9.

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