Preparation method of heat-conducting film and heat-conducting film
By preparing carbon nanotube composites loaded with magnetic metals and arranging them in a magnetic field, the problem of spatial orientation of carbon nanotubes in thermally conductive films was solved, resulting in a significant improvement in thermal conductivity and meeting the heat dissipation requirements of high-power electronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-10
AI Technical Summary
Existing thermally conductive films are difficult to prepare by achieving spatial orientation of carbon nanotubes, resulting in limited improvement in thermal conductivity.
A carbon nanotube composite loaded with magnetic metal was prepared and stirred under a uniform magnetic field to orient the carbon nanotubes along the magnetic field lines. The composite was then combined with thermally conductive resin and filler to form a slurry, which was finally cured by adding a curing agent.
It significantly improves the thermal conductivity of the thermal conductive film in a specific direction, constructs a continuous thermal conductive path, and meets the heat dissipation requirements of high-power electronic devices.
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Figure CN121825007A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of thermal conductive material preparation technology, and more specifically, to a method for preparing a thermal conductive film and the thermal conductive film itself. Background Technology
[0002] In recent years, thermally conductive films containing carbon nanotubes, such as carbon nanotube films and graphene-carbon nanotube composite thermally conductive films, have been increasingly widely used in aerospace, electronic devices, energy, and other fields. However, in the preparation process of such thermally conductive films in existing technologies, it is difficult to achieve the spatial orientation of carbon nanotubes, thus limiting the improvement of thermal conductivity.
[0003] In view of this, it is necessary to propose a new technical solution to solve the above-mentioned technical problems. Summary of the Invention
[0004] One objective of this application is to provide a method for preparing a thermally conductive film and a new technical solution for thermally conductive films.
[0005] According to a first aspect of this application, a method for preparing a thermally conductive film is provided, the method comprising: Preparation of carbon nanotube composites loaded with magnetic metals; The carbon nanotube composite loaded with magnetic metal was crushed and ground to obtain carbon nanotube composite powder loaded with magnetic metal. The composite powder, thermally conductive resin, and thermally conductive filler are added to a mold to obtain a slurry; A uniform magnetic field is applied to the slurry and the slurry is stirred. After stirring, a curing agent is added to the slurry to solidify and form a thermally conductive film.
[0006] Optionally, the preparation of the carbon nanotube composite loaded with magnetic metal includes: Carbon nanotubes were dispersed in deionized water and subjected to ultrasonic treatment to obtain a carbon nanotube dispersion. Magnetic metal salt powder is added to the carbon nanotube dispersion and homogenized to form a mixed solution; A reducing agent is added to the mixed solution and the solution is placed at a temperature of 50~70°C to carry out a reduction reaction and obtain a reaction solution. The reaction solution is dried to obtain a carbon nanotube composite loaded with magnetic metal.
[0007] Optionally, the mass ratio of the carbon nanotubes, the magnetic metal salt powder, and the reducing agent is 100:5~10:1~2.
[0008] Optionally, the median particle size of the carbon nanotube composite powder loaded with magnetic metal is 10~15 μm.
[0009] Optionally, the mass ratio of the composite powder, the thermally conductive resin, and the thermally conductive filler is 5~10:50~70:10~30.
[0010] Optionally, the thermally conductive resin is silicone grease, polyurethane, epoxy resin, or polyacrylic resin.
[0011] Optionally, the viscosity of the thermally conductive resin is 1000 ~ 5000 mPa·s.
[0012] Optionally, the strength of the uniform magnetic field is 0.5~2T.
[0013] Optionally, the thermally conductive filler is AlN, SiC, Al2O3, or graphite.
[0014] According to a second aspect of this application, a thermally conductive film is provided, which is manufactured using the preparation method described in the first aspect.
[0015] The method for preparing the thermally conductive film provided in this application provides a method for imparting magnetic response characteristics to carbon nanotubes and then applying a stable uniform magnetic field to orient the magnetically responsive carbon nanotubes along the direction of the magnetic field lines, thereby effectively constructing a continuous thermally conductive path and significantly improving the thermal conductivity of the thermally conductive film in a specific direction.
[0016] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description
[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present application and, together with their description, serve to explain the principles of the present application.
[0018] Figure 1 A flowchart illustrating the steps of a method for preparing a thermally conductive film according to an embodiment of this application. Detailed Implementation
[0019] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the present application.
[0020] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.
[0021] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.
[0022] In all the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.
[0023] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.
[0024] According to one embodiment of this application, refer to Figure 1 As shown, a method for preparing a thermally conductive film is provided, the method comprising: S101. Preparation of carbon nanotube composites loaded with magnetic metals; S102. The carbon nanotube composite loaded with magnetic metal is crushed and ground to obtain carbon nanotube composite powder loaded with magnetic metal. S103. The composite powder, thermally conductive resin and thermally conductive filler are added into a mold to obtain a slurry; a uniform magnetic field is applied to the slurry and the slurry is stirred; after stirring, a curing agent is added to the slurry to cure and form a thermally conductive film.
[0025] In the method for preparing the thermally conductive film provided in this application embodiment, in step S101, carbon nanotubes that are not magnetic can be functionalized by chemical modification, giving them magnetic response characteristics, creating material conditions for subsequent directional arrangement using a magnetic field; ensuring that carbon nanotubes can rotate and orient under the action of an external magnetic field, thereby changing from a disordered random state to an ordered directional arrangement.
[0026] Step S102 breaks down carbon nanotube agglomerates that may form during the preparation process, controlling their particle size. This ensures that the magnetic carbon nanotubes in the slurry can respond to the external magnetic field with smaller units, achieving a finer and more uniform arrangement. This improves the dispersibility of the magnetic metal-loaded carbon nanotube composite powder in the subsequent resin matrix, preventing localized performance inhomogeneities and defects caused by large agglomerates. Processing the composite into a suitable powder particle size means that each powder particle contains a moderate number of carbon nanotubes of appropriate length. This ensures good flowability in the slurry and that each unit can be effectively driven in the magnetic field, thus forming a long-range and continuous thermal conductivity pathway.
[0027] Step S103 is the core stage of film formation, in which carbon nanotube composite powder loaded with magnetic metal is mixed with thermally conductive resin and thermally conductive filler to form a slurry; wherein, the thermally conductive filler provides basic thermal conductivity, and the resin serves as a matrix for bonding and molding.
[0028] Then, applying a uniform magnetic field to the slurry provides the driving force for the oriented alignment of magnetic carbon nanotubes (typically along the film thickness direction). Under the action of this magnetic field, the magnetically responsive carbon nanotube composite loaded with magnetic metal (magnetic carbon nanotubes) is subjected to a magnetic torque, causing it to align along the magnetic field lines. The uniform magnetic field ensures that the magnetic torque experienced by the carbon nanotubes is consistent throughout the entire slurry region, thereby achieving a large-area, ordered arrangement structure. Furthermore, stirring is performed simultaneously with the application of the uniform magnetic field. The mechanical force of stirring prevents the carbon nanotubes from agglomerating too quickly or forming chain-like structures and settling under the influence of the magnetic field. Through continuous mechanical stirring, it is ensured that the carbon nanotubes are fully and uniformly mixed in the resin while being oriented.
[0029] Finally, a curing agent is added to cure and form a thermally conductive film. After the carbon nanotubes are oriented, a curing agent is immediately added to cure them, thereby locking the oriented structure of the carbon nanotubes. The resin changes from liquid to solid, firmly locking the oriented carbon nanotubes and dispersed thermally conductive fillers in place, thus transforming the temporary ordered structure induced by the magnetic field into a permanent high-performance thermally conductive material.
[0030] In summary, the method for preparing the thermally conductive film provided in this application provides a continuous thermally conductive path by imparting magnetic response characteristics to carbon nanotubes and then applying a stable uniform magnetic field to orient the magnetically responsive carbon nanotubes along the direction of the magnetic field lines, thereby significantly improving the thermal conductivity of the thermally conductive film in a specific direction.
[0031] In the prior art, the thermally conductive filler particles are isolated from each other and isolated by a polymer matrix with extremely high thermal resistance, making it impossible to form a continuous heat flow path; however, in the embodiments of this application, the oriented carbon nanotubes can form a long-range continuous thermally conductive path. The combination of the two forms a three-dimensional continuous thermally conductive network in which carbon nanotubes interweave and overlap and are connected to countless thermally conductive filler particles.
[0032] In one embodiment, the preparation of the carbon nanotube composite loaded with magnetic metal includes: S1011. Disperse carbon nanotubes in deionized water and sonicate them to obtain a carbon nanotube dispersion. S1012. Magnetic metal salt powder is added to the carbon nanotube dispersion and homogenized to form a mixed solution; S1013. Add a reducing agent to the mixed solution and carry out a reduction reaction at a temperature of 50~70°C to obtain a reaction solution; S1014. The reaction solution is dried to obtain a carbon nanotube composite loaded with magnetic metal.
[0033] In this specific example, in step S1011, carbon nanotubes are dispersed in deionized water and ultrasonically treated to obtain a carbon nanotube dispersion, which is beneficial for the carbon nanotubes to better contact and react with the magnetic metal salt powder in subsequent steps.
[0034] In steps S1012 and S1013, magnetic metal salt powder is added to the carbon nanotube dispersion for homogenization to form a mixed solution. Specifically, mechanical stirring or ultrasonic treatment is used to fully dissolve the metal salt and uniformly adsorb it onto the surface or inside the cavity of the carbon nanotubes. The carbon nanotubes have a diameter <10 nm and a length of 50–150 μm. A diameter <10 nm indicates a large specific surface area, providing abundant attachment sites for the adsorption of the magnetic metal salt and the subsequent reduction to form magnetic nanoparticles. This facilitates high-density, uniform loading of the nanoparticles, thereby enhancing the overall magnetic response of the composite material. Furthermore, if the carbon nanotube length is too short, there will be too many bridging sites between the nanotubes; if the length is too long, it will affect the uniformity of the carbon nanotube dispersion. A length of 50–150 μm is more suitable for easier interconnection in the composite to form a stable, continuous network structure.
[0035] A reducing agent is then added and a reduction reaction is carried out at a certain temperature to reduce the metal ions into magnetic nano-metal particles (such as Fe, Co, Ni, etc.), which are then firmly and uniformly loaded onto carbon nanotubes. This yields a carbon nanotube composite with stable performance and uniform magnetism, laying the foundation for subsequent directional alignment of carbon nanotubes. Magnetic metal salts can be, for example, FeCl3, CoCl2, or NiCl2; reducing agents can be, for example, sodium borohydride, hydrazine hydrate, etc.
[0036] In step S1014, the solvent is completely removed by rotary evaporation at a speed of 100-200 ppm and a temperature of 60-80°C, resulting in a dry carbon nanotube composite with magnetically responsive properties loaded with magnetic metal. The rotary evaporation process at 100-200 ppm and 60-80°C enables slow, stirred evaporation, keeping the reduction reaction within the optimal temperature range and preventing localized overheating that could lead to bumping.
[0037] In summary, in this specific example, the method of directly adding metal salts to the pre-dispersed carbon nanotube suspension and reducing them in situ allows magnetic nanoparticles to be uniformly loaded on the surface or inside the carbon nanotubes, resulting in a strong bond that is not easily detached, thus providing reliable magnetic response characteristics for subsequent magnetic field orientation.
[0038] In one embodiment, the mass ratio of the carbon nanotubes, the magnetic metal salt powder, and the reducing agent is 100:5~10:1~2.
[0039] In this specific example, the mass ratio of carbon nanotubes, magnetic metal salt powder, and reducing agent was clearly defined. An appropriate mass ratio helps to uniformly and firmly load magnetic metal nanoparticles onto the surface or within the cavity of carbon nanotubes under mild conditions via in-situ reduction, ensuring the quality of the prepared magnetic metal-loaded carbon nanotube composite and thus providing stable raw materials for the subsequent preparation of thermally conductive films. This ratio ensures that sufficient magnetic metal is reduced and loaded onto the carbon nanotubes to provide adequate magnetic response, enabling effective orientation under specific magnetic field strengths. Simultaneously, this ratio avoids the problems of carbon nanotube agglomeration, decreased thermal conductivity, and increased cost caused by excessive metal particles.
[0040] In one embodiment, the median particle size of the carbon nanotube composite powder loaded with magnetic metal is 10~15 μm.
[0041] In this specific example, the bulk carbon nanotube composite loaded with magnetic metal is first subjected to preliminary mechanical crushing, followed by fine refining using air jet milling technology to obtain carbon nanotube composite powder with a median particle size of 10~15μm. This effectively disperses the carbon nanotube aggregates that have re-agglomerated due to drying, while avoiding excessive damage to the structure of the carbon nanotubes themselves, ensuring the acquisition of ultrafine composite powder with uniform particle size distribution and good dispersibility.
[0042] In one embodiment, the mass ratio of the composite powder, the thermally conductive resin, and the thermally conductive filler is 5~10:50~70:10~30.
[0043] In this specific example, a reasonable mass ratio allows each component to fully exert its function in the slurry. Through the synergistic effect of carbon nanotubes and thermally conductive fillers, a three-dimensional, highly efficient thermally conductive network is constructed, significantly improving the thermal conductivity of the composite material in the thickness direction and meeting the heat dissipation requirements of high-power electronic devices. Specifically, the above ratio is key to constructing high-performance composite materials: the proportion of composite powder ensures a sufficient amount of "oriented skeleton" to form an effective thermally conductive network; the thermally conductive resin ensures good formability, flexibility, and mechanical strength of the material, while this amount will not introduce excessive interfacial thermal resistance due to excessive resin content; the thermally conductive filler provides basic thermal conductivity and filling density, and synergistically constructs a three-dimensional network with the oriented CNTs. This formulation pursues high thermal conductivity while also considering the processability and practicality of the material. In one embodiment, the thermally conductive resin is silicone grease, polyurethane, epoxy resin, or polyacrylic resin.
[0044] In this specific example, the type of thermally conductive resin is specified, including silicone grease, polyurethane, epoxy resin, or polyacrylic resin. Different types of thermally conductive resins have different performance characteristics. Selecting different thermally conductive resins provides a variety of matrix materials for preparing thermally conductive films, so as to meet the performance requirements of thermally conductive films in different application scenarios.
[0045] In one embodiment, the viscosity of the thermally conductive resin is 1000 ~ 5000 mPa·s.
[0046] In this specific example, the viscosity range of the thermally conductive resin is specified. A suitable viscosity helps the composite powder and thermally conductive filler disperse better in the resin, ensuring the uniformity of the slurry. This, in turn, facilitates the orientation of carbon nanotubes along the magnetic field lines during subsequent magnetic field molding, constructing a continuous thermally conductive pathway. If the viscosity is too low, the carbon nanotubes are prone to deviating from their orientation before curing; if the viscosity is too high, the carbon nanotubes are difficult to rotate and align under the influence of a magnetic field. A viscosity range of 1000 ~ 5000 mPa•s allows the magnetic force to overcome fluid resistance and orient the carbon nanotubes. After orientation, a higher viscosity can better lock the alignment of the carbon nanotubes until curing.
[0047] In one embodiment, the strength of the uniform magnetic field is 0.5~2T.
[0048] In this specific example, the stronger the uniform magnetic field, the better the orientation of the carbon nanotubes. If the magnetic field is too weak, it may not be able to generate a sufficient magnetic response from the carbon nanotubes, making it difficult to achieve effective orientation. However, if the magnetic field is too strong, it will increase the cost of the equipment and energy consumption, and will not significantly improve the orientation of the carbon nanotubes. A magnetic field strength range of 0.5~2T can ensure the orientation of the carbon nanotubes while taking into account the feasibility and economy of practical applications.
[0049] In one embodiment, the thermally conductive filler is AlN, SiC, Al2O3, or graphite.
[0050] In this specific example, the fillers themselves possess high thermal conductivity, forming the basis for the high thermal conductivity of the composite material. These fillers, together with the oriented carbon nanotubes, construct a three-dimensional thermally conductive network. The fillers bridge these filler particles, filling the thermally conductive gaps between the fillers, significantly reducing the thermal interface and contact thermal resistance of the entire composite system, and achieving a synergistic thermal conductivity effect.
[0051] In summary, this application provides a simple, highly controllable method for preparing a carbon nanotube thermally conductive film suitable for large-scale production. By optimizing the preparation of the magnetic composite, crushing and grinding, and magnetic field forming processes, the method achieves efficient orientation of carbon nanotubes and a significant improvement in their thermal conductivity. Through the synergistic effect of carbon nanotubes and thermally conductive fillers, a three-dimensional high-efficiency thermally conductive network is constructed, significantly improving the thermal conductivity of the composite material in the thickness direction and meeting the heat dissipation requirements of high-power electronic devices. This method overcomes the technical difficulties of complex magnetic modification processes, uneven modification, and easy detachment of magnetic particles. It uniformly and firmly loads magnetic metal nanoparticles onto the surface and within the cavity of carbon nanotubes using an in-situ reduction method under mild conditions. It solves the problem in existing technologies where carbon nanotubes are randomly distributed in the polymer matrix, making it difficult to form effective thermal conductive paths. By inducing the orientation of carbon nanotubes in a specific direction through magnetic field induction, the oriented carbon nanotubes effectively bridge other thermally conductive filler particles, thereby constructing a continuous thermally conductive network.
[0052] According to another embodiment of this application, a thermally conductive film is provided, which is prepared using the preparation method described above.
[0053] The thermally conductive film provided in this application has a high thermal conductivity because it has a three-dimensional continuous thermally conductive network formed by the directional arrangement of magnetic carbon nanotubes induced by a magnetic field and connected to countless thermally conductive filler particles. This network can meet the heat dissipation requirements of high-power electronic devices.
[0054] Example 1: S101. Disperse 100g of CNTs in deionized water and sonicate for 30 minutes to form a uniform carbon nanotube dispersion; add 6g of FeCl3 powder to the carbon nanotube dispersion and mechanically stir for 1 hour to allow Fe³⁺ to dissolve. + The Fe³⁺ ions were fully adsorbed onto the surface of CNTs. 1.2 g of sodium borohydride was added as a reducing agent, and the mixture was reacted in a 60°C water bath for 2 hours to allow Fe³⁺ to fully adsorb onto the surface of CNTs. + Fe nanoparticles were reduced in situ and loaded onto CNTs to obtain a reaction solution; the reaction solution was dried by rotary evaporation at 150 rpm and 70 °C to remove the solvent, resulting in a dried CNTs / Fe composite. S102. After preliminary crushing of the CNTs / Fe composite, it is refined by air jet milling to obtain CNTs / Fe composite powder with a D50 particle size of about 12 μm. S103. Weigh 8g of CNTs / Fe composite powder, 60g of silicone grease (viscosity 4000 mPa·s), and 20g of AlN thermally conductive filler, and add them together into the mold. Apply a uniform magnetic field of 1.0T in a direction perpendicular to the bottom surface of the mold and stir continuously for 20 minutes to orient the CNTs along the direction of the magnetic field. After stirring, add an appropriate amount of curing agent and cure at 80℃ for 2 hours to obtain a thermally conductive film.
[0055] The thermal conductivity of the CNTs alignment direction was measured to be 23.7 W / m·K.
[0056] Example 2: S101. Disperse 100g of CNTs in deionized water and sonicate for 30 minutes to form a uniform carbon nanotube dispersion; add 8g of CoCl2 powder to the carbon nanotube dispersion and mechanically stir for 1.5 hours to allow the Co²⁻ to form a uniform carbon nanotube dispersion. + The adsorption was fully achieved on the surface of CNTs; 1.5 g of hydrazine hydrate was added as a reducing agent, and the reaction was carried out in a water bath at 55°C for 3 hours to allow Co²⁻ to fully adsorb onto the surface of CNTs. + The reaction solution was obtained by in-situ reduction to Co nanoparticles and loading them onto CNTs. The reaction solution was then dried by rotary evaporation at 120 rpm and 65 °C to remove the solvent, resulting in a dried CNTs / Co composite. S102. After preliminary crushing of the CNTs / Co composite, it is refined by air jet milling to obtain CNTs / Fe composite powder with a D50 particle size of about 10 μm. S103. Weigh 6g of CNTs / Co composite powder, 65g of polyurethane prepolymer (viscosity 3000 mPa·s), and 15g of SiC thermally conductive filler, and add them together into the mold. Apply a uniform magnetic field of 1.5T in a direction parallel to the bottom surface of the mold and stir continuously for 15 minutes to orient the CNTs along the direction of the magnetic field. After stirring, add an appropriate amount of curing agent and cure at 100℃ for 1.5 hours to obtain a thermally conductive film.
[0057] The thermal conductivity of the CNTs alignment direction was measured to be 20.4 W / m·K.
[0058] Example 3: S101. Disperse 100g of CNTs in deionized water and sonicate for 30 minutes to form a uniform carbon nanotube dispersion; add 7g of NiCl2 powder to the carbon nanotube dispersion and mechanically stir for 2 hours to allow Ni²⁻ to form a uniform carbon nanotube dispersion. + The Ni²⁻ fully adsorbs onto the surface of CNTs; 1.8 g of sodium borohydride is added as a reducing agent, and the reaction is carried out in a 70°C water bath for 2.5 hours to allow Ni²⁻ to fully adsorb onto the surface of CNTs; +Ni nanoparticles were reduced in situ and loaded onto CNTs to obtain a reaction solution; the reaction solution was dried by rotary evaporation at 180 rpm and 75 °C to remove the solvent, resulting in a dried CNTs / Ni composite. S102. After preliminary crushing of the CNTs / Ni composite, it is refined by air jet milling to obtain CNTs / Ni composite powder with a D50 particle size of about 14 μm. S103, weigh 10g of CNTs / Ni composite powder, 55g of epoxy resin (viscosity 1500 mPa·s), and 25g of Al2O3 thermally conductive filler, and add them together into the mold; apply a uniform magnetic field of 0.8T in a direction perpendicular to the bottom surface of the mold, and stir continuously for 25 minutes to orient the CNTs along the direction of the magnetic field; after stirring, add an appropriate amount of curing agent and cure at 120℃ for 1 hour to obtain a thermally conductive film.
[0059] The thermal conductivity of the CNTs alignment direction was measured to be 25.2 W / m·K.
[0060] Example 4: S101. Disperse 100g of CNTs in deionized water and sonicate for 60 minutes to form a uniform carbon nanotube dispersion; add 5g of FeCl3 powder to the carbon nanotube dispersion and mechanically stir for 1 hour to allow Fe³⁺ to dissolve. + The Fe³⁺ ions were fully adsorbed onto the surface of CNTs. 1.0 g of sodium borohydride was added as a reducing agent, and the mixture was reacted in a 60°C water bath for 2 hours to allow Fe³⁺ to fully adsorb onto the surface of CNTs. + Fe nanoparticles were reduced in situ and loaded onto CNTs to obtain a reaction solution; the reaction solution was dried by rotary evaporation at 150 rpm and 70 °C to remove the solvent, resulting in a dried CNTs / Fe composite. S102. After preliminary crushing of the CNTs / Fe composite, it is refined by air jet milling to obtain CNTs / Fe composite powder with a D50 particle size of about 15 μm. S103. Weigh 5g of CNTs / Fe composite powder, 50g of silicone grease (viscosity 2000 mPa·s), and 10g of AlN thermally conductive filler, and add them together into the mold. Apply a uniform magnetic field of 2.0T in a direction perpendicular to the bottom surface of the mold and stir continuously for 40 minutes to orient the CNTs along the direction of the magnetic field. After stirring, add an appropriate amount of curing agent and cure at 80℃ for 2 hours to obtain a thermally conductive film.
[0061] The thermal conductivity of the CNTs alignment direction was measured to be 18.5 W / m·K.
[0062] Example 5: S101. Disperse 100g of CNTs in deionized water and sonicate for 30 minutes to form a uniform carbon nanotube dispersion; add 10g of CoCl2 powder to the carbon nanotube dispersion and mechanically stir for 1.5 hours to allow the Co²⁻ to form a uniform carbon nanotube dispersion. + The adsorption was fully achieved on the surface of CNTs; 2.0 g of hydrazine hydrate was added as a reducing agent, and the reaction was carried out in a water bath at 55°C for 3 hours to allow Co²⁻ to fully adsorb onto the surface of CNTs. + The reaction solution was obtained by in-situ reduction to Co nanoparticles and loading them onto CNTs. The reaction solution was then dried by rotary evaporation at 120 rpm and 65 °C to remove the solvent, resulting in a dried CNTs / Co composite. S102. After preliminary crushing of the CNTs / Co composite, it is refined by air jet milling to obtain CNTs / Fe composite powder with a D50 particle size of about 13 μm. S103. Weigh 10g of CNTs / Co composite powder, 70g of polyurethane prepolymer (viscosity 2000 mPa·s), and 30g of SiC thermally conductive filler, and add them together into the mold. Apply a uniform magnetic field of 0.5T in a direction parallel to the bottom surface of the mold and stir continuously for 15 minutes to orient the CNTs along the direction of the magnetic field. After stirring, add an appropriate amount of curing agent and cure at 100℃ for 1.5 hours to obtain a thermally conductive film.
[0063] The thermal conductivity of the CNTs alignment direction was measured to be 25.1 W / m·K.
[0064] Example 6: S101. Disperse 100g of CNTs in deionized water and sonicate for 30 minutes to form a uniform carbon nanotube dispersion; add 5g of NiCl2 powder to the carbon nanotube dispersion and mechanically stir for 2 hours to allow Ni²⁻ to form a uniform dispersion. + The Ni²⁻ fully adsorbs onto the surface of CNTs; 2.0 g of sodium borohydride is added as a reducing agent, and the mixture is reacted in a 70°C water bath for 2.5 hours to allow Ni²⁻ to fully adsorb onto the surface of CNTs. + Ni nanoparticles were reduced in situ and loaded onto CNTs to obtain a reaction solution; the reaction solution was dried by rotary evaporation at 180 rpm and 75 °C to remove the solvent, resulting in a dried CNTs / Ni composite. S102. After preliminary crushing of the CNTs / Ni composite, it is refined by air jet milling to obtain CNTs / Ni composite powder with a D50 particle size of about 11 μm. S103, weigh 5g of CNTs / Ni composite powder, 70g of epoxy resin (viscosity 1500 mPa·s), and 30g of Al2O3 thermally conductive filler, and add them together into the mold; apply a uniform magnetic field of 1.2T in a direction perpendicular to the bottom surface of the mold, and stir continuously for 25 minutes to orient the CNTs along the direction of the magnetic field; after stirring, add an appropriate amount of curing agent and cure at 120℃ for 1 hour to obtain a thermally conductive film.
[0065] The thermal conductivity of the CNTs alignment direction was measured to be 17.6 W / m·K.
[0066] Comparative Example 1: The preparation process is exactly the same as in Example 1, except that the uniform magnetic field is not applied in S103.
[0067] The thermal conductivity of the material perpendicular to the mold direction was measured to be 9.8 W / m·K.
[0068] Comparative Example 2: Take 100g of CNTs and perform air jet milling until the D50 particle size is about 12μm. Weigh 8g of CNTs powder, 60g of silicone grease, and 20g of AlN thermally conductive filler, and add them together into the mold. Apply a uniform magnetic field of 1.0T in a direction perpendicular to the bottom surface of the mold and stir continuously for 20 minutes. After stirring, add an appropriate amount of curing agent and cure at 80℃ for 2 hours before demolding.
[0069] The thermal conductivity of the material perpendicular to the mold direction was measured to be 10.6 W / m·K.
[0070] Comparative Example 3: The preparation process is exactly the same as in Example 1, except that in step S101, metallic Fe powder is used instead of FeCl3 powder.
[0071] The thermal conductivity of the material perpendicular to the mold direction was measured to be 14.1 W / m·K.
[0072] No external magnetic field was applied in Comparative Example 1; no magnetic modification was performed on CNTs in Comparative Example 2, as CNTs themselves are non-magnetic and the magnetic field has no directional effect on them; metal powder was used in Comparative Example 3 instead of magnetic metal salt, and the metal powder could not adhere well to the surface of carbon nanotubes, resulting in low magnetism of the carbon nanotubes.
[0073] In summary, the thermal conductivity of the thermal conductive films obtained in Examples 1 to 4 is better than that of the thermal conductive films obtained in Comparative Examples 1 to 3.
[0074] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technological improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of this application is defined by the appended claims.
Claims
1. A method for preparing a thermally conductive film, characterized in that, The preparation method includes: Preparation of carbon nanotube composites loaded with magnetic metals; The carbon nanotube composite loaded with magnetic metal was crushed and ground to obtain carbon nanotube composite powder loaded with magnetic metal. The composite powder, thermally conductive resin, and thermally conductive filler are added to a mold to obtain a slurry; A uniform magnetic field is applied to the slurry and the slurry is stirred. After stirring, a curing agent is added to the slurry to solidify and form a thermally conductive film.
2. The preparation method according to claim 1, characterized in that, The preparation of the carbon nanotube composite loaded with magnetic metal includes: Carbon nanotubes were dispersed in deionized water and subjected to ultrasonic treatment to obtain a carbon nanotube dispersion. Magnetic metal salt powder is added to the carbon nanotube dispersion and homogenized to form a mixed solution; A reducing agent is added to the mixed solution and the solution is placed at a temperature of 50~70°C to carry out a reduction reaction and obtain a reaction solution. The reaction solution is dried to obtain a carbon nanotube composite loaded with magnetic metal.
3. The preparation method according to claim 2, characterized in that, The mass ratio of the carbon nanotubes, the magnetic metal salt powder, and the reducing agent is 100:5~10:1~2.
4. The preparation method according to claim 1, characterized in that, The median particle size of the carbon nanotube composite powder loaded with magnetic metal is 10~15 μm.
5. The preparation method according to claim 1, characterized in that, The mass ratio of the composite powder, the thermally conductive resin, and the thermally conductive filler is 5~10:50~70:10~30.
6. The preparation method according to claim 1, characterized in that, The thermally conductive resin is silicone grease, polyurethane, epoxy resin, or polyacrylic resin.
7. The preparation method according to claim 1, characterized in that, The viscosity of the thermally conductive resin is 1000~5000 mPa·s.
8. The preparation method according to claim 1, characterized in that, The strength of the uniform magnetic field is 0.5~2T.
9. The preparation method according to claim 1, characterized in that, The thermally conductive filler is AlN, SiC, Al2O3, or graphite.
10. A thermally conductive film, characterized in that, The thermally conductive film is prepared using the method described in any one of claims 1-9.