A heat dissipation film

Abstract

The present invention discloses a heat dissipation film comprising horizontally oriented two-dimensional heat-conducting elements, which are prepared by the following simple, low-cost, and stable method: the two-dimensional heat-conducting elements and a gel component are dispersed in water to form an assembly liquid; a planar substrate capable of releasing charged particles is placed in the assembly liquid, and the two-dimensional heat-conducting elements are assembled along the surface of the substrate; the substrate is removed to obtain the heat dissipation film. The present invention uses gel-induced methods to prepare a highly oriented heat dissipation film with a thickness of more than 25 μm. The method is simple to operate, low-cost, and stable, with an in-plane thermal conductivity of 15.5 W / (m*K). The material obtained by the gel-induced assembly of the present invention is compressible and can be further processed to achieve an in-plane thermal conductivity of 50.9 W / (m*K).

Description

Technical Field

[0001] The present invention relates to a new material, in particular to a high thermal conductivity heat dissipation film. Background Art

[0002] In the 5G communications era, the functional innovations of 5G terminal products such as mobile phones, laptops, and computers have led to increased power consumption, rapidly escalating heat dissipation requirements. 5G base stations consume significantly more power than 4G, and their size is becoming smaller and lighter, necessitating more efficient heat dissipation methods. Cloud computing and cloud storage in 5G data centers continue to flourish, offering enormous potential for development and driving strong heat dissipation demands. Heat dissipation film, a transverse heat dissipation component inserted between electronic devices and heat sinks, converts point heat sources within the device into surface heat sources and transfers heat quickly and efficiently to the heat sink, preventing localized overheating and ensuring operational stability, safety, and reliability. Its thermal conductivity directly determines the efficiency of heat dissipation.

[0003] Traditional heat dissipation films are primarily prepared by blending thermally conductive fillers with a polymer matrix. The weak coupling between the fillers and the polymer matrix and the random arrangement of the fillers result in extremely high interfacial thermal resistance, severely reducing the film's thermal conductivity. With the rapid development of the 5G industry, heat dissipation films prepared using traditional methods are no longer able to meet the intense heat dissipation demands necessitated by the highly integrated nature of high-power, high-frequency electronic devices. Assembly methods such as vacuum filtration, electrospinning, machining, and 3D printing can align the thermally conductive fillers in a planar direction, creating effective thermal conduction pathways and thereby improving the film's in-plane thermal conductivity. Vacuum filtration can achieve high in-plane orientation of the thermally conductive fillers, resulting in a heat dissipation film with high in-plane thermal conductivity. However, this method is time-consuming and results in a small film area, making it impractical for large-scale production of high-performance heat dissipation films. Electrospinning, 3D printing, and machining, on the other hand, are complex processes and produce films with poor in-plane orientation of the thermally conductive fillers, resulting in limited thermal conduction pathways and insufficient in-plane thermal conductivity to meet application requirements. Therefore, it is necessary to develop a heat dissipation film based on ordered assembly that can be quickly and mass-produced and also has high in-plane thermal conductivity. Summary of the Invention

[0004] The purpose of the present invention is to provide a heat dissipation film in view of the deficiencies in the prior art.

[0005] The objective of the present invention is achieved through the following technical solution: comprising oriented and assembled two-dimensional thermally conductive elements, prepared by the following method: dispersing the two-dimensional thermally conductive elements and a gel component in water to form an assembly liquid, wherein the volume fraction of the two-dimensional thermally conductive elements is less than 20 vol%; placing a planar substrate capable of releasing charged particles in the assembly liquid, and assembling the two-dimensional thermally conductive elements along the surface of the substrate; removing the substrate to obtain a heat dissipation film composed of horizontally oriented two-dimensional thermally conductive elements; wherein the assembly elements can form an electrostatic interaction with the charged particles; and the gel component can form a gel under the induction of the charged particles. In the present invention, the gel component can form a gel under the induction of the charged particles, which synchronizes the diffusion of the charged particles with the formation of the gel. The gel interface contains a large number of charged particles, making the interface electrically conductive, and the interface continuously attracts nanosheets of opposite charge to migrate toward the interface. When the nanosheets are parallel to the gel surface, they have the maximum contact area and reach the most stable state, so the nanosheets are oriented parallel to the gel interface. When the nanosheets are in contact and orientation with the gel interface, as the charged particles further diffuse, the nanosheets are fixed, and the charged particles continue to diffuse forward in a direction perpendicular to the substrate to continue to orient and fix the subsequent nanosheets; therefore, based on the present invention, a thick film with high orientation and excellent thermal conductivity can be directly obtained, which is expected to be widely used in 5G terminal products such as mobile phones, laptops, computers, 5G base stations, and 5G data centers.

[0006] Experiments have shown that the volume fraction of two-dimensional thermal conductive elements should be below 20 vol%; if the content is too high, the steric hindrance between the nanosheets will be relatively large, affecting the turning of the nanosheets in space and reducing the degree of orientation.

[0007] Because assembly units are assembled under the influence of charged particles released from the substrate, those skilled in the art can foresee that the concentration of charged particles released from the substrate will affect the thickness of the aligned assembly. A higher concentration of charged particles results in a thicker assembly; experiments have shown that ordered assembly can be achieved at a concentration of 0.1 mol / L. Those skilled in the art can adjust the concentration of charged particles released from the substrate based on desired product thickness.

[0008] In the present invention, the content of the gel component is subject to the following premises: ① the concentration cannot be too low, otherwise, gel cannot be formed under the induction of the charged particles; ② the concentration cannot be too high, otherwise the viscosity of the assembly liquid is too high, causing orientation resistance; under normal circumstances, the viscosity of the assembly liquid should be below 500mPa·s.

[0009] Since the formation speed of the gel is directly related to the release speed of the charged particles of the substrate, it has been proved through experiments that when the formation speed of the gel is below 0.2 mm / min, the effective orientation induction of the gel for the assembly unit can be guaranteed. For example, for divalent calcium ions, under adsorption conditions, the concentration of the charged particles adsorbed by the substrate is set to below 5 mol / L, which can ensure that the speed of gel formation is below 0.2 mm / min; and for trivalent iron ions, under adsorption conditions, the concentration of the charged particles adsorbed by the substrate is set to below 1 mol / L to ensure that the speed of gel formation is below 0.2 mm / min. Those skilled in the art can regulate the concentration of the adsorbed charged particles by detecting the formation speed of the gel, or regulate the electrochemical reaction speed (such as the current size, for the metal that releases the charged particles in situ in the reaction), so as to achieve the best promoting effect of the gel.

[0010] In some preferred embodiments of the present invention, the in-plane thermal conductivity is also improved by compression. Specifically, the thick film obtained after removing the substrate and drying is compressed by means of room temperature roller pressing, heated roller pressing, flat plate hot pressing, etc.

[0011] Furthermore, the two-dimensional thermal conductive element is at least one of boron nitride nanosheets, graphene nanosheets, aluminum oxide nanosheets, and silver nanosheets.

[0012] Furthermore, the charged particles are selected from Na + , Ca 2+ 、Zn 2+ 、Ba 2+ 、Cu 2+ 、Fe 3+ 、Al 3+ 、Zr 4+ , citrate, and tripolyphosphate.

[0013] Furthermore, the gel component is selected from at least one of polyurethane, sodium alginate, pectin, cellulose, chitosan, sodium polygalacturonate, branched polyethyleneimine, and cationic polyacrylamide.

[0014] The present invention has the following beneficial effects: A highly oriented heat dissipation film with a thickness exceeding 25 μm is produced by gel-induction, with simple operation, low cost, and stable results, achieving an in-plane thermal conductivity of 15.5 W / (m*K). The material obtained by gel-induction assembly is compressible and, through further processing, can achieve an in-plane thermal conductivity of 50.9 W / (m*K). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a cross-sectional morphology of the boron nitride / sodium alginate film prepared in Example 1 of the present invention.

[0016] Figure 2 This is a cross-sectional morphology of the boron nitride / sodium alginate heat dissipation film after compression treatment in Example 1 of the present invention.

[0017] Figure 3 This is a cross-sectional morphology of the graphene / sodium alginate heat dissipation film prepared in Example 2 of the present invention.

[0018] Figure 4 This is a cross-sectional morphology of the pure graphene film prepared in Comparative Example 2 of the present invention.

[0019] Figure 5 This is a cross-sectional morphology of the boron nitride / polyurethane film prepared in Example 3 of the present invention.

[0020] Figure 6 This is a cross-sectional morphology of the boron nitride / polyurethane heat dissipation film after compression treatment in Example 3 of the present invention.

[0021] Figure 7 This is a cross-sectional morphology of the boron nitride / polyurethane film prepared in Example 4 of the present invention.

[0022] Figure 8 This is a cross-sectional morphology of the boron nitride / polyurethane heat dissipation film after compression treatment in Example 4 of the present invention.

[0023] Figure 9 This is a cross-sectional morphology of the boron nitride / polyurethane film prepared in Example 5 of the present invention.

[0024] Figure 10 This is a cross-sectional morphology of the boron nitride / polyurethane heat dissipation film after compression treatment in Example 5 of the present invention.

[0025] Figure 11 This is a cross-sectional morphology of the aluminum oxide / sodium alginate membrane prepared in Example 6 of the present invention. DETAILED DESCRIPTION

[0026] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0027] In the description of the present invention, it should be understood that the terms "plane", "xy plane", "front and back", "left and right", "vertical direction", "normal", "up and down", "upward", "downward", etc., indicating orientations or positional relationships, are orientations or positional relationships, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] Since the concentration of the assembly units, the viscosity of the assembly liquid, and the concentration of charged particles in the solution adsorbed on the substrate can all be adjusted according to needs through simple experiments, in the following embodiments, unless otherwise specified, the concentration of the assembly units is calculated to be 0-20 vol%, the viscosity of the assembly liquid is tested to be below 500 mPa·s, the concentration of charged particles adsorbed on the substrate is above 0.1 mol / L, and the gelation speed is ensured to be below 0.2 mm / min.

[0029] Example 1

[0030] This embodiment provides a boron nitride heat dissipation film in which heat-conducting elements are arranged along a plane and a method for assembling the film in an orderly manner. The preparation method includes the following steps:

[0031] (1) 30 g of hexagonal boron nitride powder, 10 g of polyurethane and 110 ml of deionized water were mixed, and the solution was ultrasonically treated for 3 h at 30% power using a cell crusher to obtain a mixed solution containing hexagonal boron nitride nanosheets.

[0032] (2) The mixed solution prepared in step 1 was centrifuged at 500 rpm for 5 min, the supernatant was taken, and the supernatant was centrifuged at 8000 rpm for 10 min to obtain a bottom precipitate. The precipitate was mixed with deionized water for washing, and then centrifuged at 8000 rpm for 10 min. The above centrifugal washing operation was repeated 2-3 times, and the bottom precipitate after centrifugal washing was freeze-dried to obtain hexagonal boron nitride nanosheets.

[0033] (3) 10 g of hexagonal boron nitride nanosheets, 2 g of sodium alginate, and 100 ml of deionized water were mixed and ultrasonically dispersed at 30% power for 30 min to obtain an assembly solution for ordered assembly. The volume fraction of the hexagonal boron nitride nanosheets was 4.4 vol%, and the viscosity of the assembly solution was below 500 mPa·s.

[0034] (4) 40 g of anhydrous calcium chloride and 100 ml of deionized water were mixed to obtain a calcium chloride solution for ordered assembly.

[0035] (5) Take filter paper as the assembly substrate and immerse it in the above calcium chloride solution to obtain an assembly substrate containing calcium ions.

[0036] (6) The calcium ion-containing assembly substrate was horizontally immersed in the assembly solution prepared in step 3, and the solution was left there for 60 seconds. The solution was then slowly removed to obtain a wet film orderly assembled on the substrate with a thickness of 260 μm.

[0037] (7) The wet film was immersed in deionized water to wash away excess calcium ions, and then the substrate was removed and dried at 60°C for 3 min to obtain a film with hexagonal boron nitride nanosheets aligned along the plane. The film had a thickness of 65 μm and a density of 0.96 g / cm 3 The in-plane thermal diffusion coefficient of the film at room temperature was tested by a laser thermal conductivity meter, and the specific heat capacity of the film at room temperature was tested by differential scanning calorimetry. According to the in-plane thermal conductivity = in-plane thermal diffusion coefficient * specific heat capacity * density, the in-plane thermal conductivity of the film at room temperature was calculated to be 14.3W / (m*K).

[0038] (8) The film was compressed by a roller pressing process, with the roller pressing pressure controlled at 20 MPa and the roller pressing rate at 10 mm / s. The film was repeatedly rolled for more than 10 times at room temperature to obtain a film with a thickness of 28 μm and a density of 1.75 g / cm 3 The boron nitride heat dissipation film has a boron nitride filling content of 85 wt.%. The in-plane thermal diffusivity of the boron nitride heat dissipation film at room temperature was measured using a laser thermal conductivity meter, and the specific heat capacity of the boron nitride heat dissipation film at room temperature was measured using differential scanning calorimetry. Based on the formula in-plane thermal conductivity = in-plane thermal diffusivity * specific heat capacity * density, the in-plane thermal conductivity of the boron nitride heat dissipation film at room temperature was calculated to be 50.9 W / (m*K).

[0039] Figure 1 This is a cross-sectional morphology of the boron nitride / sodium alginate film obtained in step 7. It can be seen that inside the film, the hexagonal boron nitride nanosheets are oriented along the planar direction. Figure 2 This is a cross-sectional morphology of the boron nitride / sodium alginate heat dissipation film obtained in step 8. It can be seen that after compression treatment, the hexagonal boron nitride nanosheets inside the film are further oriented along the planar direction and are more closely connected to each other, constructing a more effective in-plane heat conduction path.

[0040] Comparative Example 1

[0041] (1) 30 g of hexagonal boron nitride powder, 10 g of polyurethane and 110 ml of deionized water were mixed, and the solution was ultrasonically treated for 3 h at 30% power using a cell crusher to obtain a mixed solution containing hexagonal boron nitride nanosheets.

[0042] (2) The mixed solution prepared in step 1 was centrifuged at 500 rpm for 5 min, the supernatant was taken, and the supernatant was centrifuged at 8000 rpm for 10 min to obtain a bottom precipitate. The precipitate was mixed with deionized water for washing, and then centrifuged at 8000 rpm for 10 min. The above centrifugal washing operation was repeated 2-3 times, and the bottom precipitate after centrifugal washing was freeze-dried to obtain hexagonal boron nitride nanosheets.

[0043] (3) 10 g of hexagonal boron nitride nanosheets were mixed with 100 ml of deionized water without adding sodium alginate, which can form a gel under the influence of calcium ions. After ultrasonic dispersion at 30% power for 30 minutes, an assembly solution was obtained. The volume fraction of the hexagonal boron nitride nanosheets was 4.4 vol%.

[0044] (4) 40 g of anhydrous calcium chloride and 100 ml of deionized water were blended to obtain a calcium chloride solution for assembly.

[0045] (5) Take filter paper as the assembly substrate and immerse it in the above calcium chloride solution to obtain an assembly substrate containing calcium ions.

[0046] (6) The above-mentioned assembly substrate containing calcium ions was horizontally immersed in the assembly solution prepared in step 3, kept for 60 seconds, and slowly taken out. It was found that a large amount of precipitation appeared in the assembly solution, and the hexagonal boron nitride nanosheets did not form a film on the assembly substrate.

[0047] Example 2

[0048] This embodiment provides a graphene heat dissipation film in which heat-conducting elements are arranged along a plane and an ordered assembly method thereof, wherein the preparation method comprises the following steps:

[0049] (1) 10 ml of a 10 mg / ml aqueous dispersion of monolayer graphene oxide, 1 g of sodium alginate, and 10 ml of deionized water were mixed and stirred at 500 rpm for 30 min to obtain an assembly solution for ordered assembly. The volume fraction of the monolayer graphene oxide was 0.2 vol%, and the viscosity of the assembly solution was less than 500 mPa·s.

[0050] (2) 40 g of anhydrous barium chloride and 100 ml of deionized water were mixed to obtain a barium chloride solution for ordered assembly.

[0051] (3) Take filter paper as an assembly substrate and immerse it in the above-mentioned barium chloride solution to obtain an assembly substrate containing barium ions.

[0052] (4) The above-mentioned assembly substrate containing barium ions is horizontally immersed in the assembly solution prepared in step 1, and stays for 300 seconds. It is slowly taken out to obtain a wet film assembled in an orderly manner on the substrate with a thickness of 800 μm.

[0053] (5) The wet film was immersed in deionized water to wash away excess barium ions, and then the substrate was removed and dried at room temperature. After reduction with hydroiodic acid, hot pressing was performed at 20 MPa and 95°C for 15 min to obtain a graphene heat dissipation film with graphene nanosheets aligned along the plane. The thickness was 13.2 μm and the density was 1.95 g / cm 3The graphene filling amount is 83wt.%. The in-plane thermal diffusion coefficient of the graphene heat dissipation film at room temperature is tested by a laser thermal conductivity meter, and the specific heat capacity of the graphene film at room temperature is tested by differential scanning calorimetry. According to the in-plane thermal conductivity = in-plane thermal diffusion coefficient * specific heat capacity * density, the in-plane thermal conductivity of the graphene heat dissipation film at room temperature is calculated to be 885.2W / (m*K).

[0054] Figure 3 This is a cross-sectional image of the graphene / sodium alginate heat dissipation film produced in step 5. It shows that the graphene nanosheets are aligned along the planar direction within the film. Furthermore, the graphene / sodium alginate heat dissipation film is thick, which means it has more thermal conduction pathways and thus a higher heat flux.

[0055] Comparative Example 2

[0056] (1) 10 ml of a 10 mg / ml monolayer graphene oxide aqueous dispersion was mixed with 10 ml of deionized water without adding sodium alginate, which can form a gel under the induction of barium ions. The mixture was stirred at 500 rpm for 30 minutes to obtain an assembly solution. The volume fraction of the monolayer graphene oxide was 0.2 vol%, and the viscosity of the assembly solution was less than 500 mPa·s.

[0057] (2) 40 g of anhydrous barium chloride and 100 ml of deionized water were mixed to obtain a calcium chloride solution for assembly.

[0058] (3) Take filter paper as an assembly substrate and immerse it in the above-mentioned barium chloride solution to obtain an assembly substrate containing barium ions.

[0059] (4) The above-mentioned assembly substrate containing barium ions is horizontally immersed in the assembly solution prepared in step 1, and stays for 300 seconds. It is slowly taken out to obtain a wet film assembled on the substrate with a thickness of only 250 μm.

[0060] (5) The wet film was immersed in deionized water to wash away excess barium ions, and then the substrate was removed and dried at room temperature. After reduction with hydroiodic acid, it was hot pressed at 20 MPa and 95°C for 15 minutes to obtain a graphene film with graphene nanosheets aligned along the plane, with a thickness of only 1.9 μm.

[0061] Figure 4 This is a cross-sectional morphology of the pure graphene film obtained in step 5. It can be seen that without adding components that can form a gel under the induction of charged particles, the charged particles cannot continuously diffuse to the gel interface, so the prepared pure graphene film has a very small thickness and a low heat flux.

[0062] Example 3

[0063] This embodiment provides a boron nitride heat dissipation film in which heat-conducting elements are arranged along a plane and a method for assembling the film in an orderly manner. The preparation method includes the following steps:

[0064] (1) 30 g of hexagonal boron nitride powder, 10 g of polyurethane and 110 ml of deionized water were mixed, and the solution was ultrasonically treated for 3 h at 30% power using a cell crusher to obtain a mixed solution containing hexagonal boron nitride nanosheets.

[0065] (2) The mixed solution prepared in step 1 was centrifuged at 500 rpm for 5 min, the supernatant was taken, and the supernatant was centrifuged at 8000 rpm for 10 min to obtain a bottom precipitate. The precipitate was mixed with deionized water for washing, and then centrifuged at 8000 rpm for 10 min. The above centrifugal washing operation was repeated 2-3 times, and the bottom precipitate after centrifugal washing was freeze-dried to obtain hexagonal boron nitride nanosheets.

[0066] (3) 5 g of hexagonal boron nitride nanosheets, 5 g of polyurethane, and 100 ml of deionized water were mixed and ultrasonically dispersed at 30% power for 30 min to obtain an assembly solution for ordered assembly. The volume fraction of the hexagonal boron nitride nanosheets was 2.2 vol%, and the viscosity of the assembly solution was below 500 mPa·s.

[0067] (4) 40 g of anhydrous calcium chloride and 100 ml of deionized water were mixed to obtain a calcium chloride solution for ordered assembly.

[0068] (5) Take filter paper as the assembly substrate and immerse it in the above calcium chloride solution to obtain an assembly substrate containing calcium ions.

[0069] (6) The calcium ion-containing assembly substrate was horizontally immersed in the assembly solution prepared in step 3, and the solution was left there for 60 seconds. The solution was then slowly removed to obtain a wet film orderly assembled on the substrate with a thickness of 190 μm.

[0070] (7) The wet film was immersed in deionized water to wash away excess calcium ions, and then the substrate was removed and dried at 60°C for 3 min to obtain a film with hexagonal boron nitride nanosheets aligned along the plane. The film had a thickness of 63 μm and a density of 0.91 g / cm 3 The in-plane thermal diffusion coefficient of the film at room temperature was tested by a laser thermal conductivity meter, and the specific heat capacity of the film at room temperature was tested by differential scanning calorimetry. According to the in-plane thermal conductivity = in-plane thermal diffusion coefficient * specific heat capacity * density, the in-plane thermal conductivity of the film at room temperature was calculated to be 15.5W / (m*K).

[0071] (8) The film was compressed by a heated roller pressing process, with the roller pressing pressure controlled at 20 MPa and the roller pressing rate at 10 mm / s. The film was repeatedly rolled at a temperature of 40°C for more than 10 times to obtain a film with a thickness of 30 μm and a density of 1.67 g / cm 3 The boron nitride heat dissipation film has a boron nitride filling content of 73 wt.%. The in-plane thermal diffusivity of the boron nitride heat dissipation film at room temperature was measured using a laser thermal conductivity meter, and the specific heat capacity of the boron nitride heat dissipation film at room temperature was measured using differential scanning calorimetry. Based on the formula in-plane thermal conductivity = in-plane thermal diffusivity * specific heat capacity * density, the in-plane thermal conductivity of the boron nitride heat dissipation film at room temperature was calculated to be 38.4 W / (m*K).

[0072] Figure 5 This is a cross-sectional morphology of the boron nitride / polyurethane film obtained in step 7. It can be seen that after replacing the gel component, the hexagonal boron nitride nanosheets inside the film are still oriented along the planar direction. Figure 6 This is a cross-sectional morphology of the boron nitride / polyurethane heat dissipation film obtained in step 8. It can be seen that after compression treatment, the hexagonal boron nitride nanosheets inside the film are further oriented along the planar direction and are more closely connected to each other, constructing a more effective in-plane heat conduction path.

[0073] Example 4

[0074] This embodiment provides a boron nitride heat dissipation film in which heat-conducting elements are arranged along a plane and a method for assembling the film in an orderly manner. The preparation method includes the following steps:

[0075] (1) 30 g of hexagonal boron nitride powder, 10 g of polyurethane and 110 ml of deionized water were mixed, and the solution was ultrasonically treated for 3 h at 30% power using a cell crusher to obtain a mixed solution containing hexagonal boron nitride nanosheets.

[0076] (2) The mixed solution prepared in step 1 was centrifuged at 500 rpm for 5 min, the supernatant was taken, and the supernatant was centrifuged at 8000 rpm for 10 min to obtain a bottom precipitate. The precipitate was mixed with deionized water for washing, and then centrifuged at 8000 rpm for 10 min. The above centrifugal washing operation was repeated 2-3 times, and the bottom precipitate after centrifugal washing was freeze-dried to obtain hexagonal boron nitride nanosheets.

[0077] (3) 15 g of hexagonal boron nitride nanosheets, 5 g of polyurethane, and 100 ml of deionized water were mixed and ultrasonically dispersed at 30% power for 30 min to obtain an assembly solution for ordered assembly. The volume fraction of the hexagonal boron nitride nanosheets was 6.6 vol%, and the viscosity of the assembly solution was below 500 mPa·s.

[0078] (4) 25 g of anhydrous calcium chloride and 100 ml of deionized water were mixed to obtain a calcium chloride solution for ordered assembly.

[0079] (5) Take filter paper as the assembly substrate and immerse it in the above calcium chloride solution to obtain an assembly substrate containing calcium ions.

[0080] (6) The calcium ion-containing assembly substrate was horizontally immersed in the assembly solution prepared in step 3, and the solution was kept for 60 seconds. The solution was slowly removed to obtain a wet film orderly assembled on the substrate with a thickness of 160 μm.

[0081] (7) The wet film was immersed in deionized water to wash away excess calcium ions, and then the substrate was removed and dried at 60°C for 3 min to obtain a thin film of hexagonal boron nitride nanosheets oriented along the plane with a thickness of 57 μm and a density of 0.92 g / cm 3 The in-plane thermal diffusion coefficient of the film at room temperature was tested by a laser thermal conductivity meter, and the specific heat capacity of the film at room temperature was tested by differential scanning calorimetry. According to the in-plane thermal conductivity = in-plane thermal diffusion coefficient * specific heat capacity * density, the in-plane thermal conductivity of the film at room temperature was calculated to be 13.5W / (m*K).

[0082] (8) The film was compressed by a roller pressing process, with the roller pressing pressure controlled at 20 MPa and the roller pressing rate at 10 mm / s. The film was repeatedly rolled for more than 10 times at room temperature to obtain a film with a thickness of 36 μm and a density of 1.36 g / cm 3 The boron nitride heat dissipation film has a boron nitride filling content of 71 wt.%. The in-plane thermal diffusivity of the boron nitride heat dissipation film at room temperature was measured using a laser thermal conductivity meter, and the specific heat capacity of the boron nitride heat dissipation film at room temperature was measured using differential scanning calorimetry. Based on the formula in-plane thermal conductivity = in-plane thermal diffusivity * specific heat capacity * density, the in-plane thermal conductivity of the boron nitride heat dissipation film at room temperature was calculated to be 23.8 W / (m*K).

[0083] Figure 7 This is a cross-sectional morphology of the boron nitride / polyurethane film obtained in step 7. It can be seen that after changing the concentration of the calcium chloride solution used for ordered assembly, the hexagonal boron nitride nanosheets inside the film are still oriented along the planar direction. Figure 8 This is a cross-sectional morphology of the boron nitride / polyurethane heat dissipation film obtained in step 8. It can be seen that after compression treatment, the hexagonal boron nitride nanosheets inside the film are further oriented along the planar direction and are more closely connected to each other, constructing a more effective in-plane heat conduction path.

[0084] Example 5

[0085] This embodiment provides a boron nitride heat dissipation film in which heat-conducting elements are arranged along a plane and a method for assembling the film in an orderly manner. The preparation method includes the following steps:

[0086] (1) 30 g of hexagonal boron nitride powder, 10 g of polyurethane and 110 ml of deionized water were mixed, and the solution was ultrasonically treated for 3 h at 30% power using a cell crusher to obtain a mixed solution containing hexagonal boron nitride nanosheets.

[0087] (2) The mixed solution prepared in step 1 was centrifuged at 500 rpm for 5 min, the supernatant was taken, and the supernatant was centrifuged at 8000 rpm for 10 min to obtain a bottom precipitate. The precipitate was mixed with deionized water for washing, and then centrifuged at 8000 rpm for 10 min. The above centrifugal washing operation was repeated 2-3 times, and the bottom precipitate after centrifugal washing was freeze-dried to obtain hexagonal boron nitride nanosheets.

[0088] (3) 100 ml of deionized water was added to the container, along with a certain amount of hexagonal boron nitride nanosheets to achieve a volume content of approximately 20 vol%. Polyurethane was then slowly added while monitoring the viscosity in real time. When the viscosity of the assembly solution reached approximately 500 mPa·s, the addition was stopped, completing the preparation of the assembly solution. The assembly solution was then ultrasonically dispersed at 30% power for 30 minutes to obtain the assembly solution for ordered assembly.

[0089] (4) 65 g of anhydrous zinc chloride and 100 ml of deionized water were mixed to obtain a zinc chloride solution for ordered assembly.

[0090] (5) Take filter paper as an assembly substrate and immerse it in the above zinc chloride solution to obtain an assembly substrate containing zinc ions.

[0091] (6) The above-mentioned assembly substrate containing zinc ions is horizontally immersed in the assembly solution prepared in step 3, left for 120 seconds, and slowly taken out to obtain a wet film orderly assembled on the substrate with a thickness of 230 μm.

[0092] (7) The wet film was immersed in deionized water to wash away excess zinc ions, and then the substrate was removed and dried at 60°C for 3 min to obtain a thin film of hexagonal boron nitride nanosheets oriented along the plane with a thickness of 48 μm and a density of 1.09 g / cm 3 The in-plane thermal diffusion coefficient of the film at room temperature was tested by a laser thermal conductivity meter, and the specific heat capacity of the film at room temperature was tested by differential scanning calorimetry. According to the in-plane thermal conductivity = in-plane thermal diffusion coefficient * specific heat capacity * density, the in-plane thermal conductivity of the film at room temperature was calculated to be 14.8W / (m*K).

[0093] (8) The film was compressed by a flat-plate hot pressing process at a pressure of 20 MPa and a temperature of 50°C for 30 min to obtain a film with a thickness of 35 μm and a density of 1.46 g / cm 3The boron nitride heat dissipation film has a boron nitride filling content of 67 wt.%. The in-plane thermal diffusivity of the boron nitride heat dissipation film at room temperature was measured using a laser thermal conductivity meter, and the specific heat capacity of the boron nitride heat dissipation film at room temperature was measured using differential scanning calorimetry. Based on the formula in-plane thermal conductivity = in-plane thermal diffusivity * specific heat capacity * density, the in-plane thermal conductivity of the boron nitride heat dissipation film at room temperature was calculated to be 35.6 W / (m*K).

[0094] Figure 9 This is a cross-sectional morphology of the boron nitride / polyurethane film obtained in step 7. It can be seen that after replacing the charged particles, the hexagonal boron nitride nanosheets inside the film are still oriented along the planar direction. Figure 10 This is a cross-sectional morphology of the boron nitride / polyurethane heat dissipation film obtained in step 8. It can be seen that after compression treatment, the hexagonal boron nitride nanosheets inside the film are further oriented along the planar direction and are more closely connected to each other, constructing a more effective in-plane heat conduction path.

[0095] Example 6

[0096] This embodiment provides an aluminum oxide heat dissipation film in which heat-conducting elements are arranged along a plane and an orderly assembly method thereof, wherein the preparation method comprises the following steps:

[0097] (1) 15 g of alumina nanosheets, 2 g of sodium alginate, and 100 ml of deionized water were mixed and ultrasonically dispersed at 30% power for 30 min to obtain an assembly solution for ordered assembly. The volume fraction of the alumina nanosheets was 4.1 vol%, and the viscosity of the assembly solution was below 500 mPa·s.

[0098] (2) Prepare a calcium chloride solution with a concentration of 0.1 mol / L for ordered assembly.

[0099] (3) Take filter paper as an assembly substrate and immerse it in the above calcium chloride solution to obtain an assembly substrate containing calcium ions.

[0100] (4) The calcium ion-containing assembly substrate was horizontally immersed in the assembly solution prepared in step 1, and stayed there for 30 seconds. The substrate was slowly removed to obtain a wet film orderly assembled on the substrate with a thickness of 750 μm.

[0101] (5) The wet film was immersed in deionized water to wash away excess calcium ions, and then the substrate was removed and dried at 60°C for 10 min to obtain a thick film with aluminum oxide nanosheets aligned along the plane. The thickness was 670 μm and the density was 1.31 g / cm 3The alumina filling amount is 97wt.%. The in-plane thermal diffusivity of the alumina heat dissipation film at room temperature is tested by a laser thermal conductivity meter, and the specific heat capacity of the alumina heat dissipation film at room temperature is tested by differential scanning calorimetry. According to the in-plane thermal conductivity = in-plane thermal diffusivity * specific heat capacity * density, the in-plane thermal conductivity of the alumina heat dissipation film at room temperature is calculated to be 4.3W / (m*K).

[0102] Figure 11 This is a cross-sectional morphology of the aluminum oxide / sodium alginate heat dissipation film obtained in step 5. It can be seen that inside the film, the aluminum oxide nanosheets are oriented along the planar direction, constructing an effective in-plane heat conduction path.

[0103] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A heat dissipation film comprising two-dimensional heat-conducting elements assembled in an oriented manner, characterized in that: The method is as follows: dispersing a two-dimensional thermal conductive element and a gel component in water to form an assembly liquid, wherein the volume fraction of the two-dimensional thermal conductive element is less than 20 vol%; A planar substrate capable of releasing charged particles is placed in an assembly liquid, and two-dimensional heat-conducting elements are assembled along the surface of the substrate; the substrate is removed to obtain a heat dissipation film; wherein the two-dimensional heat-conducting elements can form an electrostatic interaction with the charged particles; and the gel component can form a gel under the induction of the charged particles; The viscosity of the assembly fluid should be below 500 mPa·s, and the charged particle concentration should be greater than or equal to 0.1 mol / L; The two-dimensional heat-conducting element is a nanosheet having a thermal conductivity of 1 W / (m*K) or more; the nanosheet having a thermal conductivity of 1 W / (m*K) or more is at least one of boron nitride nanosheets, graphene nanosheets, aluminum oxide nanosheets, and silver nanosheets; The charged particles are selected from Na + , Ca 2+ 、Zn 2+ 、Ba 2+ 、Cu 2+ 、Fe 3+ 、Al 3+ 、Zr 4+ At least one of; The gel component is selected from at least one of polyurethane, sodium alginate, pectin and cellulose.

2. The heat dissipation film according to claim 1, wherein It also includes compressing the heat dissipation film.

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