Polydopamine modified liquid metal microsphere / boron nitride nanosheet heat-conducting composite film as well as preparation method and application thereof

Abstract

The invention discloses a polydopamine modified liquid metal microsphere / boron nitride nanosheet heat-conducting composite film as well as a preparation method and application thereof. The polydopamine modified liquid metal microsphere / boron nitride nanosheet heat-conducting composite film comprises polydopamine modified liquid metal microspheres, boron nitride nanosheets and a polymer base material, wherein the polydopamine modified liquid metal microspheres are filled and distributed in lamellar gaps of the adjacent boron nitride nanosheets. When the composite film is prepared, gallium-based liquid metal microspheres coated with polydopamine are adopted, a heat-conducting bridging medium with the characteristics of insulation, high heat conductivity and extremely easy deformation is obtained, effective filling of lapped ultra-micro gaps among rigid boron nitride nanosheets can be achieved, the transverse heat conductivity of the composite material is improved, and the composite film has good mechanical characteristics and is suitable for large-scale production. The problem that the existing soaking film is poor in heat dissipation efficiency under the severe application working conditions of insulation and high heat conduction in the current development situation can be effectively solved, and the heat management requirements of the industries such as semiconductors are met.

Description

Technical Field

[0001] This invention relates to a thermally conductive composite thin film material, specifically to a polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite thin film, its preparation method and application, belonging to the field of thermally conductive materials technology. Background Technology

[0002] With the rapid miniaturization and integration of electronic components, power systems, and communication equipment, system power density has increased significantly, leading to a rapid rise in operating ambient temperature. To ensure long-term stable and reliable operation, immediate heat dissipation capability has become a key factor determining the performance, reliability, and lifespan of electronic devices. Currently, the general consensus in academia and industry is that the heat dissipation capability of electronic devices depends on the thermal management materials used, rather than the devices themselves. This means that developing a high-performance thermal management material has become a critical issue that urgently needs to be addressed. Polymer materials are currently the most widely used encapsulation materials, characterized by low density, light weight, excellent mechanical properties, low cost, and ease of processing; however, their intrinsic thermal conductivity is very low. Therefore, modifying polymer materials by adding high thermal conductivity fillers has become an important technical means for developing a new generation of high-performance thermal management materials.

[0003] Hexagonal boron nitride nanosheets, also known as "white graphene," possess not only a very high in-plane thermal conductivity (1000 W / m²), but also... -1 K -1 It also has strong resistance to electrical breakdown (breakdown strength: 35kV mm). -1 Hexagonal boron nitride (BN) nanosheets have shown unparalleled advantages in special applications requiring thermal insulation and conductivity, attracting increasing attention. However, their inherent flexibility is poor. When they directly self-assemble into a thermally conductive network, numerous overlapping microvoids form between the rigid, inflexible layers, resulting in extremely high thermal resistance at the interfaces. This is a major reason limiting further improvements in the thermal conductivity of BN-based thermally conductive composites. Therefore, it is necessary to introduce a self-adhesive thermally conductive medium with high deformation capacity and develop corresponding compounding methods to effectively fill the microvoids between rigid BN nanosheet layers, thereby achieving a new breakthrough in the thermal conductivity of hexagonal BN-based thermally conductive composites. Summary of the Invention

[0004] The main objective of this invention is to provide a polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film, its preparation method, and its application, in order to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] One aspect of the present invention provides a thermally conductive composite film of polydopamine-modified liquid metal microspheres / boron nitride nanosheets, comprising: polydopamine-modified liquid metal microspheres, boron nitride nanosheets and a polymer substrate, wherein the polydopamine-modified liquid metal microspheres are distributed and filled in the interlayer voids of adjacent boron nitride nanosheets.

[0007] In some embodiments, the polydopamine-modified liquid metal microspheres include gallium-based liquid metal microspheres and a polydopamine coating layer disposed on the surface of the gallium-based liquid metal microspheres.

[0008] Another aspect of the present invention provides a method for preparing a polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film, comprising:

[0009] A first dispersion comprising a first dispersant and polydopamine-modified liquid metal microspheres dispersed in the first dispersant is provided;

[0010] A second dispersion is provided, comprising a second dispersant, boron nitride nanosheets dispersed in the second dispersant, and a polymeric substrate;

[0011] The first dispersion and the second dispersion are mixed, and the resulting mixture is subjected to a film-forming treatment to obtain the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film.

[0012] Another aspect of the present invention provides the application of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film in the field of thermal management.

[0013] Accordingly, another aspect of the present invention provides a thermal management material comprising the aforementioned polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects:

[0015] The polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film provided by this invention utilizes gallium-based liquid metal microspheres coated with polydopamine, resulting in a thermally conductive bridging medium that combines insulation, high thermal conductivity, and highly deformable properties. This allows for the effective filling of micro-voids between the layers of rigid boron nitride nanosheets. The lateral thermal conductivity of the composite film is between 40 and 130 W / m. -1 K -1 It combines excellent mechanical properties (tensile strength greater than 40MPa) and can effectively solve the problem of poor heat dissipation performance of existing heat sinks in demanding applications with high thermal conductivity and insulation, thus meeting the thermal management needs of industries such as semiconductors. Attached Figure Description

[0016] 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 only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a microscopic morphology diagram of liquid metal microspheres in a typical embodiment of the present invention;

[0018] Figure 2 This is a microscopic morphology diagram of polydopamine-encapsulated liquid metal microspheres in a typical embodiment of the present invention. Detailed Implementation

[0019] In view of the shortcomings of the prior art, the inventors of this case, after long-term research, proposed the technical concept of the present invention, which mainly provides a method for preparing a thermally conductive composite thin film material of polydopamine modified liquid metal microspheres / boron nitride nanosheets. The composite thin film material is composed of polydopamine modified liquid metal microspheres, high aspect ratio boron nitride nanosheets and a polymer substrate.

[0020] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0021] As one aspect of the technical solution of the present invention, a thermally conductive composite film of polydopamine modified liquid metal microspheres / boron nitride nanosheets includes: a polymer substrate and a thermally conductive reinforcing filler composited with the polymer substrate. The thermally conductive reinforcing filler includes polydopamine modified liquid metal microspheres and boron nitride nanosheets, and the polydopamine modified liquid metal microspheres are filled and distributed in the interlayer voids of adjacent boron nitride nanosheets.

[0022] In a preferred embodiment, the polydopamine-modified liquid metal microspheres comprise gallium-based liquid metal microspheres and a polydopamine coating layer disposed on the surface of the gallium-based liquid metal microspheres. After the gallium-based liquid metal microspheres are completely coated with polydopamine, a thermally conductive bridging medium with insulating, high thermal conductivity, and highly deformable properties is obtained, which can effectively fill the micro-voids between the layers of rigid boron nitride nanosheets.

[0023] In a preferred embodiment, the polydopamine-modified liquid metal microspheres are prepared by modifying liquid metal microspheres with polydopamine. The liquid metal microspheres can be obtained through high-intensity ultrasonic treatment, and surface modification can be achieved using polydopamine. Therefore, based on the large deformation capacity of liquid metal and the excellent adhesion properties of polydopamine, the overlapping ultra-micro voids between rigid boron nitride nanosheets can be effectively filled, improving the lateral thermal conductivity of the composite material. Furthermore, the polydopamine coating effectively avoids the negative impact of the liquid metal microspheres on the insulation performance of the composite material, better meeting the thermal management requirements of industries such as semiconductors in demanding applications requiring insulation and high thermal conductivity.

[0024] In a preferred embodiment, the diameter of the gallium-based liquid metal microspheres is between 10 and 1000 nm.

[0025] Furthermore, the diameter of the gallium-based liquid metal microspheres is between 50 and 500 nm. This invention controls the size of the liquid metal microsphere nanoparticles through centrifugal screening, making them more compatible with the micro-nano gap sizes between boron nitride particles, thus enhancing their interstitial filling ability. While increasing the thermal conductivity pathway, it also maintains the excellent horizontal alignment of the boron nitride nanosheets, preventing deterioration of the boron nitride nanosheet alignment due to excessively large bridging medium sizes.

[0026] In a preferred embodiment, the liquid metal is a gallium-based liquid metal, and its material includes, but is not limited to, at least one of pure gallium, gallium-indium materials, gallium-indium-tin materials, gallium-indium-bismuth materials, gallium-tin materials, and gallium-indium-tin-zinc materials. Gallium-based liquid metals are metallic materials that melt at room temperature and are characterized by their softness and deformability. Therefore, when liquid metal nanoparticles are used to bridge boron nitride nanosheets, they can fill the overlapping micro-gaps between adjacent boron nitride nanosheets relatively perfectly due to their own rigidity.

[0027] Furthermore, the composition of the gallium-based liquid metal includes, but is not limited to, any one or more combinations of pure gallium, gallium 75.5%-indium 24.5%, gallium 68.5%-indium 21.5%-tin 10%, gallium 50%-indium 30%-bismuth 20%, gallium 86.5%-tin 13.5%, gallium 61%-indium 25%-tin 13% zinc, etc.

[0028] In a preferred embodiment, the thickness of the polydopamine coating layer is between 1 and 60 nm.

[0029] Furthermore, the thickness of the polydopamine coating layer is between 4 and 10 nm. Polydopamine coating effectively enhances the bonding strength between the liquid metal microspheres and boron nitride, reduces interfacial thermal resistance, and improves the overall mechanical properties of the material. Moreover, the polydopamine coating layer effectively prevents adjacent liquid metal nanoparticles from forming conductive pathways in series, thus effectively maintaining the insulating properties of the composite material.

[0030] In a preferred embodiment, the boron nitride nanosheets comprise boron nitride nanosheets with a high aspect ratio.

[0031] In a preferred embodiment, the lateral dimensions of the high aspect ratio boron nitride nanosheets are between 1 and 15 μm, the thickness is between 1 and 10 nm, and the average aspect ratio is between 600 and 2000.

[0032] In a preferred embodiment, the polymeric substrate includes any one or a combination of two or more of polyurethane, polyvinyl alcohol, polyvinyl butyral, polyvinylidene fluoride, and nanocellulose, but is not limited thereto.

[0033] In a preferred embodiment, the mass ratio of the polydopamine-modified liquid metal microspheres to boron nitride nanosheets is between 1:1 and 1:100.

[0034] Furthermore, the mass ratio of the polydopamine-modified liquid metal microspheres to boron nitride nanosheets is between 1:9 and 1:100.

[0035] In a preferred embodiment, the maximum content of the polymer substrate in the polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film does not exceed 50 wt%.

[0036] In some embodiments, the thickness of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film is between 10 and 100 μm, and the density is between 1.7 and 2.5 g / cm³. -3 between.

[0037] In some more preferred embodiments, the thickness of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film is between 20 and 30 μm, and the density is between 1.9 and 2.1 g / cm³. -3 between.

[0038] In some embodiments, the transverse thermal conductivity (i.e., in-plane thermal conductivity) of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film is between 40 and 130 W / m. -1 K -1It combines good mechanical properties (tensile strength greater than 40MPa) and can effectively solve the problem of poor heat dissipation performance of existing heat dissipation films when facing special applications with insulation and high thermal conductivity.

[0039] In some embodiments, the volume resistivity of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film is greater than 1×10⁻⁶. 9 Ωcm, preferably greater than 1×10 10 Ωcm.

[0040] As another aspect of the technical solution of the present invention, it also relates to a method for preparing a polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film, comprising:

[0041] A first dispersion comprising a first dispersant and polydopamine-modified liquid metal microspheres dispersed in the first dispersant is provided;

[0042] A second dispersion is provided, comprising a second dispersant, boron nitride nanosheets dispersed in the second dispersant, and a polymeric substrate;

[0043] The first dispersion and the second dispersion are mixed, and the resulting mixture is subjected to a film-forming treatment to obtain the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film.

[0044] In some more specific embodiments, a method for preparing a polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film includes the following steps:

[0045] (1) A first dispersion is provided, the first dispersion comprising a first dispersant and polydopamine-modified liquid metal microspheres dispersed in the first dispersant;

[0046] (2) A second dispersion is provided, the second dispersion comprising a second dispersant and high aspect ratio boron nitride nanosheets and a polymer substrate dispersed in the second dispersant;

[0047] (3) The first dispersion and the second dispersion are mixed in a certain proportion and formed into a film to obtain the polydopamine modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film.

[0048] In some preferred embodiments, the second dispersant includes, but is not limited to, any one or a combination of two or more of deionized water, anhydrous ethanol, and N,N-dimethylformamide.

[0049] In a typical implementation, step (1) involves the preparation method of the polydopamine-modified liquid metal microspheres, which includes:

[0050] The liquid metal is mixed with the first dispersant and subjected to top ultrasonic treatment. After being dispersed evenly, it is centrifuged to obtain the supernatant.

[0051] The supernatant was thoroughly mixed with dopamine hydrochloride and reacted at room temperature to obtain the polydopamine-modified liquid metal microspheres. The polydopamine coating thickness was controlled by the reaction time.

[0052] In some preferred embodiments, the first dispersant includes, but is not limited to, any one or a combination of two or more of water (such as deionized water), anhydrous ethanol, and N,N-dimethylformamide.

[0053] In a more preferred embodiment, the preparation process of the polydopamine-modified liquid metal microspheres specifically includes:

[0054] S1: Liquid metal is added to deionized water in a certain proportion, the top is ultrasonically treated to disperse it evenly, and the supernatant is taken after centrifugation;

[0055] S2: Add dopamine hydrochloride to the dispersion and stir until it is fully dissolved. After reacting for a period of time, the polydopamine-modified liquid metal microspheres can be obtained.

[0056] In some preferred embodiments, in step S1, the liquid metal is a gallium-based liquid metal, and its composition includes, but is not limited to: pure gallium, gallium 75.5%-indium 24.5%, gallium 68.5%-indium 21.5%-tin 10%, gallium 50%-indium 30%-bismuth 20%, gallium 86.5%-tin 13.5%, gallium 61%-indium 25%-tin 13%-zinc 1%, etc.

[0057] In some preferred embodiments, in step S1, the diameter of the gallium-based liquid metal microspheres is between 10 and 1000 nm, preferably between 50 and 500 nm.

[0058] In some preferred embodiments, in step S1, the mass ratio of the liquid metal to deionized water is 1:50 to 1:500.

[0059] In some preferred embodiments, in step S1, the power of the top ultrasonic treatment is between 325 and 650 W, and the top ultrasonic treatment time is between 0.5 and 4 hours.

[0060] In a more preferred embodiment, the top ultrasonic treatment power is between 520 and 650 W, and the top ultrasonic treatment time is between 1 and 2.5 h.

[0061] In a more preferred embodiment, the centrifugation speed is between 500 and 4000 rad / min, and the centrifugation time is between 3 and 20 min.

[0062] In some preferred embodiments, step (2) involves the following method for preparing the second dispersion:

[0063] Boron nitride nanosheets with large aspect ratios were prepared using a microfluidic method.

[0064] The polymer substrate is dissolved in a second solvent to form a polymer solution, and boron nitride nanosheets with a large aspect ratio are added to the polymer solution and ultrasonically stirred until homogeneous to obtain the second dispersion.

[0065] In some preferred embodiments, the second solvent includes, but is not limited to, any one or a combination of two or more of deionized water, anhydrous ethanol, and N,N-dimethylformamide.

[0066] In a more preferred embodiment, the boron nitride nanosheets with a large aspect ratio described in step (2) have a lateral dimension between 1 and 15 μm, a thickness between 1 and 10 nm, and an average aspect ratio between 600 and 2000.

[0067] In a more preferred embodiment, the polymer substrate in step (2) includes, but is not limited to, polyurethane, polyvinyl alcohol, polyvinyl butyral, polyvinylidene fluoride, and nanocellulose.

[0068] In a more preferred embodiment, the film-forming process in step (3) includes, but is not limited to, at least one of the following methods: filtration, casting, electrospinning and hot pressing.

[0069] More specifically, the composite film material of the present invention uses hexagonal boron nitride nanosheets with a large aspect ratio and polydopamine-modified liquid metal microspheres as thermally conductive reinforcing fillers, and is composited with a polymer substrate by means including but not limited to filtration, casting, and electrospinning.

[0070] In a more preferred embodiment, in step (3), the mass ratio of polydopamine-modified liquid metal microspheres in the first dispersion to boron nitride nanosheets in the second dispersion is 1:1 to 1:100, preferably 1:9 to 1:100.

[0071] As another aspect of the technical solution of the present invention, it also relates to the application of the aforementioned polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film in the field of thermal management.

[0072] Furthermore, the applications include those in industries such as semiconductors for thermal management in demanding applications requiring insulation and high thermal conductivity.

[0073] Furthermore, another aspect of the present invention provides a thermal management material comprising the aforementioned polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film.

[0074] In summary, by employing the above technical solutions, this invention provides a polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite thin film material, which improves its thermal conductivity in the lateral direction. After the gallium-based liquid metal microspheres are completely coated with polydopamine, a thermally conductive medium with insulating, high thermal conductivity, and highly deformable properties is obtained. This material can effectively fill the ultra-micro gaps between the rigid boron nitride nanosheets, and can be applied to thermal management in demanding applications requiring insulation and high thermal conductivity in industries such as semiconductors.

[0075] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions of the present invention are further described below with reference to several embodiments, but the present invention is not limited to the scope of the embodiments described herein. Unless otherwise specified, the raw materials used in the embodiments are all commercially purchased and used directly without processing; the instruments and equipment used in the embodiments all use the manufacturer's recommended parameters.

[0076] Secondly, the term "an embodiment" or "embodiment" as used in this invention refers to a specific feature, structure, or characteristic that can be included in at least one implementation of this invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0077] The boron nitride nanosheets used in the following examples are hexagonal boron nitride nanosheets with a large aspect ratio, having a lateral dimension of 1–15 μm, a thickness of 1–10 nm, and an average aspect ratio of 600–2000.

[0078] Example 1

[0079] 1 g of gallium-based liquid metal (75.5% gallium - 24.5% indium) was added to 199 ml of deionized water and dispersed by top ultrasonication for 2 h at a power of 650 W. The mixture was then centrifuged at 1000 rad / min for 15 min, and the supernatant was collected to obtain liquid metal microspheres with an average particle size of approximately 100 nm. Then, 0.01 g of dopamine hydrochloride was added, and the mixture was stirred until the reaction was complete to obtain the polydopamine-modified liquid metal microspheres. The thickness of the liquid metal coating layer was between 4 and 10 nm.

[0080] Add 18 mg of hexagonal boron nitride nanosheets to 25 ml of deionized water, sonicate in a water bath for 15 min, then add nanocellulose solution (nanocellulose content is 1 wt%), sonicate in a water bath and stir for 15 min to obtain a uniform dispersion.

[0081] Polydopamine-modified liquid metal microspheres and hexagonal boron nitride nanosheets were mixed at a mass ratio of 1:9 and stirred for 15 minutes. The mixture was then filtered to form a film, which yielded the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film. The content of the polymer matrix in the composite material was controlled to be approximately 30 wt%.

[0082] Testing showed that the transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment is approximately 120 W / m. -1 K -1 .

[0083] A microscopic morphology image of the liquid metal microspheres prepared in a typical embodiment of the present invention can be found in [reference needed]. Figure 1 As shown, the microstructure of the polydopamine-encapsulated liquid metal microspheres can be found in the image. Figure 2 As shown.

[0084] Example 2

[0085] The difference between this embodiment and Example 1 is that the dopamine polymerization time is extended so that the thickness of the polydopamine coating layer is between 8-20 nm, while the other steps are basically the same.

[0086] The transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment is approximately 85 W / m², according to testing. -1 K -1 .

[0087] Comparative Example 1

[0088] The difference between this embodiment and Embodiment 1 is that the liquid metal is not coated with polydopamine, but the other steps are basically the same.

[0089] Testing showed that the transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment is approximately 90 W / m². -1 K -1 .

[0090] Example 3

[0091] The difference between this embodiment and embodiment 1 is that the centrifugation speed is reduced to 500 rad / min and the centrifugation time is 20 min, while the remaining steps are basically the same.

[0092] The transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment was measured to be approximately 111 W / m². -1 K -1 .

[0093] Example 4

[0094] The difference between this embodiment and Embodiment 1 is that the centrifugation speed is increased to 1500 rad / min and the centrifugation time is 10 min, while the remaining steps are basically the same.

[0095] The transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment was measured to be approximately 113 W / m². -1 K -1 .

[0096] Example 5

[0097] The difference between this embodiment and Embodiment 1 is that the centrifugation speed is increased to 4000 rad / min and the centrifugation time is reduced to 3 min, while the remaining steps are basically the same.

[0098] Testing showed that the transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment is approximately 107 W / m. -1 K -1 .

[0099] Example 6

[0100] The difference between this embodiment and Example 1 is that polydopamine-modified liquid metal microspheres and hexagonal boron nitride nanosheets are mixed at a mass ratio of 1:15. The remaining steps are basically the same.

[0101] Testing showed that the transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment is approximately 105 W / m. -1 K -1 .

[0102] Example 7

[0103] The difference between this embodiment and Example 1 is that polydopamine-modified liquid metal microspheres and hexagonal boron nitride nanosheets are mixed in a mass ratio of 2:8, while the remaining steps are basically the same.

[0104] The transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment was tested to be approximately 97 W / m. -1 K -1 .

[0105] Example 8

[0106] The difference between this embodiment and Embodiment 1 is that the composition of the gallium-based liquid metal is changed to 68.5% gallium, 21.5% indium, and 10% tin, while the remaining steps are basically the same.

[0107] Testing showed that the transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment is approximately 115 W / m. -1 K -1 .

[0108] Example 9

[0109] The difference between this embodiment and Example 1 is that the polymer matrix used is changed to polyvinyl alcohol, while the other steps are basically the same.

[0110] The transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment was tested to be approximately 82 W / m. -1 K -1 .

[0111] Example 10

[0112] The difference between this embodiment and embodiment 1 is that the ultrasonic power is changed to 600W and the ultrasonic treatment time is 0.5h, while the other steps are basically the same.

[0113] The transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment was measured to be approximately 10⁶ W / m². -1 K -1 .

[0114] Example 11

[0115] The difference between this embodiment and embodiment 1 is that the ultrasonic power is changed to 325W and the ultrasonic time is changed to 4h, while the remaining steps are basically the same.

[0116] The transverse thermal conductivity of the thermally conductive composite film prepared in this embodiment was measured to be approximately 112 W / m². -1 K -1 .

[0117] Example 12

[0118] The difference between this embodiment and Example 1 is that the mass ratio of liquid metal to deionized water is 1:50, and the polydopamine-modified liquid metal microspheres and hexagonal boron nitride nanosheets are mixed in a mass ratio of 1:1. The remaining steps are basically the same.

[0119] Example 13

[0120] The difference between this embodiment and Example 1 is that the composition of the gallium-based liquid metal is changed to 61% gallium, 25% indium, 13% tin, and 1% zinc, the mass ratio of liquid metal to deionized water is 1:500, and polydopamine-modified liquid metal microspheres and hexagonal boron nitride nanosheets are mixed at a mass ratio of 1:100. The remaining steps are basically the same.

[0121] Example 14

[0122] The difference between this embodiment and Embodiment 1 is that the gallium-based liquid metal composition is changed to 86.5% gallium and 13.5% tin, the deionized water is replaced with N,N-dimethylformamide, and the polymer matrix used is changed to polyvinylidene fluoride. The remaining steps are basically the same.

[0123] Example 15

[0124] The difference between this embodiment and Embodiment 1 is that the gallium-based liquid metal composition is changed to 50% gallium, 30% indium, and 20% bismuth; deionized water is replaced with N,N-dimethylformamide; and the polymer matrix used is changed to polyurethane. The remaining steps are basically the same.

[0125] Example 16

[0126] The difference between this embodiment and Example 1 is that deionized water is replaced with ethanol, and the polymer matrix used is changed to polyvinyl butyral; the remaining steps are basically the same.

[0127] The transverse thermal conductivity of the thermally conductive composite films prepared in Examples 12-16 was tested using the method described above. The results showed that their transverse thermal conductivity was all between 40 and 130 W / m. -1 K -1 between.

[0128] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0129] The above description is merely a few embodiments of this application and does not constitute any limitation on this application. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film, characterized in that, include: The invention comprises polydopamine-modified liquid metal microspheres, boron nitride nanosheets, and a polymer substrate, wherein the polydopamine-modified liquid metal microspheres are distributed and filled within the interlayer voids of adjacent boron nitride nanosheets.

2. The polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film according to claim 1, characterized in that, include: A polymer substrate and a thermally conductive reinforcing filler composited with the polymer substrate, the thermally conductive reinforcing filler comprising polydopamine-modified liquid metal microspheres and boron nitride nanosheets, wherein the polydopamine-modified liquid metal microspheres are distributed and filled within the interlayer voids of adjacent boron nitride nanosheets.

3. The polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film according to claim 1, characterized in that: The polydopamine-modified liquid metal microspheres include gallium-based liquid metal microspheres and a polydopamine coating layer disposed on the surface of the gallium-based liquid metal microspheres; And / or, the polydopamine-modified liquid metal microspheres are prepared by surface modification of liquid metal microspheres with polydopamine.

4. The polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film according to claim 3, characterized in that: The diameter of the gallium-based liquid metal microspheres is 10–1000 nm, preferably 50–500 nm. And / or, the gallium-based liquid metal microsphere material includes at least one of pure gallium, gallium indium material, gallium indium tin material, gallium indium bismuth material, gallium tin material, and gallium indium tin zinc material; And / or, the thickness of the polydopamine coating layer is 1 to 60 nm, preferably, the thickness of the polydopamine coating layer is 4 to 10 nm.

5. The polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film according to claim 1, characterized in that: The boron nitride nanosheets include high aspect ratio boron nitride nanosheets. Preferably, the high aspect ratio boron nitride nanosheets have a lateral dimension of 1-15 μm, a thickness of 1-10 nm, and an average aspect ratio of 600-2000. And / or, the polymer substrate includes any one or a combination of two or more of polyurethane, polyvinyl alcohol, polyvinyl butyral, polyvinylidene fluoride, and nanocellulose. And / or, the mass ratio of the polydopamine-modified liquid metal microspheres to boron nitride nanosheets is 1:1 to 1:00, preferably 1:9 to 1:100; And / or, the content of the polymer substrate in the polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film does not exceed 50 wt%.

6. The polydopamine-modified liquid metal microspheres / boron nitride nanosheet thermally conductive composite film according to claim 1, characterized in that: The polydopamine-modified liquid metal microspheres / boron nitride nanosheets thermally conductive composite film has a thickness of 10–100 μm and a density of 1.7–2.5 g / cm³. -3 Preferably, the polydopamine-modified liquid metal microspheres / boron nitride nanosheets thermally conductive composite film has a thickness of 20–30 μm and a density of 1.9–2.1 g / cm³. -3 ; And / or, the transverse thermal conductivity of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film is 40–130 W / m. -1 K -1 ; And / or, the volume resistivity of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film is greater than 10. 9 Ωcm, preferably greater than 1×10 10 Ωcm.

7. The method for preparing the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film according to any one of claims 1-6, characterized in that, include: A first dispersion comprising a first dispersant and polydopamine-modified liquid metal microspheres dispersed in the first dispersant is provided; A second dispersion is provided, comprising a second dispersant, boron nitride nanosheets dispersed in the second dispersant, and a polymeric substrate; The first dispersion and the second dispersion are mixed, and the resulting mixture is subjected to a film-forming treatment to obtain the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film.

8. The preparation method according to claim 7, characterized in that, include: The liquid metal is mixed with the first dispersant and subjected to top ultrasonic treatment. After being dispersed evenly, it is centrifuged to obtain the supernatant. The supernatant was thoroughly mixed with dopamine hydrochloride and reacted at room temperature to obtain the polydopamine-modified liquid metal microspheres. Preferably, the mass ratio of the liquid metal to the first dispersant is 1:50 to 1:500; Preferably, the top ultrasonic treatment power is 325-650W, and the top ultrasonic treatment time is 0.5-4h; more preferably, the top ultrasonic treatment power is 520-650W, and the top ultrasonic treatment time is 1-2.5h. Preferably, the centrifugation speed is 500–4000 rad / min, and the centrifugation time is 3–20 min; And / or, the first dispersant comprises any one or a combination of two or more of water, anhydrous ethanol, and N,N-dimethylformamide; And / or, the preparation method includes: Boron nitride nanosheets with large aspect ratios were prepared using a microfluidic method. The polymer substrate is dissolved in a second solvent to form a polymer solution, and boron nitride nanosheets with a large aspect ratio are added to the polymer solution and ultrasonically stirred to obtain the second dispersion. And / or, the second solvent includes any one or a combination of two or more of water, anhydrous ethanol, and N,N-dimethylformamide; And / or, the mass ratio of polydopamine-modified liquid metal microspheres in the first dispersion to boron nitride nanosheets in the second dispersion is 1:1 to 1:100, preferably 1:9 to 1:100; And / or, the film-forming process includes any one of vacuum filtration, casting, electrospinning, and hot pressing.

9. The application of the polydopamine-modified liquid metal microsphere / boron nitride nanosheet thermally conductive composite film according to any one of claims 1-6 in the field of thermal management.

10. A thermal management material, characterized in that, The thermally conductive composite film comprising polydopamine-modified liquid metal microspheres / boron nitride nanosheets as described in any one of claims 1-6.

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