High-thermal-conductivity boron nitride / phase change microcapsule composite material as well as preparation and application thereof

Abstract

The invention discloses a high-thermal-conductivity boron nitride / phase change microcapsule composite material as well as preparation and application thereof. The preparation method of the composite material comprises the following steps: (1) mixing boron nitride nanosheets, a polymer binder, phase change microcapsules and water to prepare a boron nitride / phase change microcapsule dispersion liquid; (2) injecting the boron nitride / phase change microcapsule dispersion liquid into a directional freezing device for directional freezing to obtain a frozen block material; and then freeze-drying to obtain the boron nitride / phase change microcapsule porous material with a lamellar structure. And (3) carrying out hot pressing on the boron nitride / phase change microcapsule porous material to obtain the compact boron nitride / phase change microcapsule composite material. The invention provides an application of the boron nitride / phase change microcapsule composite material as a thermal interface material, and solves the problem that effective improvement of heat conductivity and effective packaging of a phase change material cannot be realized at the same time in the prior art.

Description

(1) Technical field

[0001] The present invention relates to the technical field of thermal interface material preparation, and in particular to a high thermal conductivity boron nitride / phase change microcapsule composite material and its preparation and application. (2) Background technology

[0002] As electronic devices increase in power and frequency, their highly integrated designs often lead to significant heat concentration, posing serious challenges to their operational stability and safety [Adv. Funct. Mater. 2025, 35, 2415370.]. Finding effective heat dissipation methods to quickly dissipate the heat generated by electronic devices during operation has become a key technical challenge in advancing electronic packaging technology.

[0003] To address the heat concentration problem caused by the high integration of high-power, high-frequency electronic devices, various heat dissipation technologies have been researched and applied to ensure the operational stability, safety, and reliability of these devices [Adv. Compos. Hybrid Ma. 2023, 6, 27]. Among them, thermally conductive phase change materials (TIPCMs) are a special type of thermal interface material that combines the high energy storage properties of phase change materials (PCMs) with the efficient heat conduction of thermally conductive materials. They are considered one of the most promising new solutions in modern thermal management technology [Adv. Funct. Mater. 2023, 33, 2301549]. During the operation of electronic devices, critical components such as chips generate a large amount of heat. If this heat cannot be dissipated in a timely and effective manner, it can lead to overheating, affecting performance, shortening service life, and even causing damage. The phase change materials in TIPCMs absorb large amounts of heat and undergo a phase change, storing the heat to prevent a sharp temperature rise in components such as chips. At the same time, the thermally conductive material, with its efficient heat conduction capabilities, quickly transfers absorbed heat to the device's cooling system, effectively dissipating the heat. This synergistic effect makes TIPCMs excellent for thermal management in electronic devices. They not only effectively control temperature but also improve device stability and reliability, providing a strong guarantee for the high-performance operation of electronic devices. However, the inherent low thermal conductivity of phase-change materials limits their efficiency in thermal energy storage and conversion devices, making it difficult to achieve the desired heat dissipation effect [Adv. Funct. Mater. 2025, 35, 2412066.]. Furthermore, liquid phase-change materials inevitably leak during repeated cycles of heat absorption and release, significantly impacting the stable operation and safety of the device. Therefore, improving the thermal conductivity of phase-change materials and addressing leakage issues are crucial for the practical application of thermal management [Adv. Mater. 2024, 36, 2411820.].

[0004] The use of high thermal conductivity fillers (such as carbon-based fillers, ceramic fillers, etc.) to construct a three-dimensional thermal conductive network and compound it with phase change materials can effectively improve the thermal conductivity of phase change materials. Among them, boron nitride nanosheets have many excellent properties such as high thermal conductivity, electrical insulation, and good thermal stability. They are one of the ideal fillers for preparing high thermal conductivity phase change composite materials [ACS Nano 2023, 17, 18850-18863.]. At present, the methods for using boron nitride to improve the thermal conductivity of phase change materials mainly include vacuum filtration, surface modification, chemical vapor deposition, etc. [Mat. Sci. Eng. R 2025, 164, 100968.]. These methods are difficult to form an efficient three-dimensional thermal conductive network, which limits the effective improvement of thermal conductivity and cannot fully meet the needs of efficient heat dissipation of electronic devices. The directional freezing method can significantly improve the thermal conductivity of the material by pre-constructing a thermally conductive skeleton and adsorbing the phase change material [ACS Appl. Mater. Interfaces 2024, 16, 66411-66424.].

[0005] Since the micron-scale three-dimensional thermally conductive skeleton is unable to provide sufficient capillary condensation to completely adsorb the molten phase change material, the phase change material still has leakage problems during the heat absorption and release cycle, affecting the stability and safety of the equipment. In order to effectively deal with the above problems, the phase change material is microencapsulated by using a polymer shell layer, which can effectively avoid leakage problems during phase transformation. However, due to the low thermal conductivity of the polymer shell and the phase change material, the thermal conductivity of the phase change microcapsules (PCMCs) is limited. Therefore, modifying or compounding polymer microcapsules with high thermal conductivity fillers has become a key strategy to improve the thermal conductivity of polymer phase change microcapsules.

[0006] The present invention aims to provide a high-thermal-conductivity boron nitride / phase-change microcapsule composite material, its preparation method, and its application. This approach addresses the technical issues in related technologies, which hinder the simultaneous improvement of thermal conductivity and effective encapsulation of the phase-change material, thus failing to meet the requirements for efficient heat dissipation and stable operation of electronic devices. Furthermore, thanks to the stability of the microcapsules, this strategy allows the selection of core materials with appropriate phase-change temperatures for different application scenarios, resulting in a thermal management material with a wide range of applications. (3) Summary of the invention

[0007] The first object of the present invention is to provide a high thermal conductivity boron nitride / phase change microcapsule composite material and its preparation method and application, so as to solve the problem in the related art that it is impossible to simultaneously achieve effective improvement of thermal conductivity and effective encapsulation of phase change materials.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0009] In a first aspect, a method for preparing a boron nitride / phase change microcapsule composite material comprises the following steps:

[0010] (1) mixing boron nitride nanosheets, phase change microcapsules, a polymer binder, and water, and stirring thoroughly to obtain a dispersion; then, ultrasonically treating the dispersion in an ice-water bath using an ultrasonic cell disruptor in a pulse mode to obtain a boron nitride / phase change microcapsule dispersion; wherein the phase change temperature of the phase change material in the phase change microcapsules is between 20° C. and 95° C.;

[0011] (2) injecting the boron nitride / phase change microcapsule dispersion into a directional freezing device, placing the directional freezing device in a refrigerant at -20 to -200°C for directional freezing until the liquid is completely converted into a solid, thereby obtaining a frozen block material; thereafter, freeze-drying the material to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous skeleton material having a lamellar structure; the directional freezing device is a columnar structure with a square, rectangular, trapezoidal or parallelogram bottom surface, and a bevel block is provided inside the directional freezing device, and the bevel block is aligned with the directional freezing device. The bottom and side surfaces of the directional freezing device are in contact with each other, and the intersection line of the inclined surface of the inclined surface block and the horizontal bottom surface is in contact with one of the two parallel sides of the bottom surface of the directional freezing device, and the inclination angle (i.e., the angle between the inclined surface and the horizontal line) of the straight section of the inclined surface block (i.e., the section where the inclined surface block is perpendicular to the two parallel sides of the bottom surface) is in the range of 5 to 45°, the bottom surface of the directional freezing device is made of metal with good thermal conductivity, the side surface of the directional freezing device is made of polytetrafluoroethylene, and the inclined surface block in the directional freezing device is made of polydimethylsiloxane;

[0012] (3) placing the boron nitride / phase change microcapsule porous material in a mold, and hot pressing it at a temperature of 45 to 110° C. and a pressure of 10 to 40 MPa for 5 to 45 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0013] The phase change microcapsules described in the present invention are obtained by encapsulating a phase change material (core material) with a polymer material (wall material) using microcapsule technology. The wall material can be urea-formaldehyde resin, melamine formaldehyde (MF) resin, polystyrene, polymethyl methacrylate, etc. The core material can be paraffin wax. The mass ratio of the core material to the wall material is generally 3-6:1, for example, 3-4:1. The phase change microcapsules can be prepared with reference to the methods reported in the literature, for example, with reference to the following literature: Luo Chenglin, Zhao Lutong, Mi Yifang, Cao Zhihai. Preparation and thermal properties of low formaldehyde, high core-wall ratio phase change microcapsules. Journal of Zhejiang Sci-Tech University, 2022, 47(1): 23-30. In step (1) of the present invention, the phase change microcapsules can be added in the form of phase change microcapsule solids or phase change microcapsules emulsions.

[0014] Preferably, in step (1), the mass ratio of boron nitride nanosheets to polymer binder is 9-12:1, and the mass ratio of boron nitride nanosheets to phase change microcapsules is 20-80%:20-80% (the total mass of boron nitride nanosheets and phase change microcapsules is 100%).

[0015] Preferably, in step (1) of the present invention, the average lateral size of the boron nitride nanosheets is between 1 and 10 μm, more preferably between 4 and 6 μm.

[0016] Preferably, in step (1) of the present invention, the polymer binder is at least one selected from polyvinyl alcohol, sodium carboxymethyl cellulose, styrene-maleic anhydride copolymer, polyacrylamide, and methyl cellulose.

[0017] Preferably, in step (1) of the present invention, the phase change temperature range of the phase change microcapsules is 20 to 90°C.

[0018] Preferably, in step (1), the ultrasonic treatment time is 0.5-3 h. More preferably, the ultrasonic power is 30 W, the operation time is 12 s, and the rest time is 6 s.

[0019] Preferably, in step (1) of the present invention, the volume fraction of boron nitride nanosheets in the boron nitride / phase change microcapsule dispersion is 2.0 to 7.5 vol%, more preferably 2.0 to 3.0 vol%, and most preferably 2.5 vol%.

[0020] Preferably, in step (2) of the present invention, the refrigerant for directional freezing is a refrigerator freezer layer, dry ice or liquid nitrogen.

[0021] Preferably, in step (2) of the present invention, the directional freezing temperature is -150 to -200°C, more preferably -175 to -200°C.

[0022] Preferably, in step (3) of the present invention, the hot pressing temperature is 50-100°C, more preferably 70-90°C; the pressure is 15-40 MPa; more preferably 30-40 MPa; the time is 5-30 min, more preferably 10-20 min; and the most preferred hot pressing temperature is 80°C, the pressure is 35 MPa, and the time is 15 min.

[0023] In a second aspect, a boron nitride / phase change microcapsule composite material is provided, which is prepared by the preparation method described in the first aspect.

[0024] In a third aspect, the invention provides application of the boron nitride / phase change microcapsule composite material described in the second aspect as a thermal interface material.

[0025] In a fourth aspect, an electronic device is provided, comprising a heat dissipation device and a heating device, wherein the boron nitride / phase change microcapsule composite material described in the second aspect is arranged between the heat dissipation device and the heating device as a thermal interface material.

[0026] In a fifth aspect, an intelligent communication device is provided, wherein the boron nitride / phase change microcapsule composite material described in the second aspect is provided in the heating area thereof as a thermal interface material.

[0027] Compared to the prior art, the present invention applies directionally frozen boron nitride / phase-change microcapsule dispersion in a directional freezing device. Under the combined action of vertical and horizontal temperature gradients, ice crystals grow in a planar pattern along the two temperature gradients. During this process, the majority of the boron nitride nanosheets and phase-change microcapsules are squeezed by the growing ice crystals between two adjacent ice crystal layers, where they assemble to form a long-range oriented lamellar structure. Because the selected boron nitride nanosheets and phase-change microcapsules are of similar size, they are captured by ice crystals with similar ease. By adjusting the amount of phase-change microcapsules added, the microcapsules can be maximized within the boron nitride framework without destroying the thermally conductive boron nitride skeleton, simultaneously meeting the requirements of high thermal conductivity and phase-change energy storage. After complete freezing, the ice crystals are removed by freeze-drying to obtain a boron nitride / phase-change microcapsule porous material with a lamellar structure. Further, through simple hot pressing, a layered boron nitride / phase-change microcapsule composite material can be obtained, in which the phase-change microcapsules are uniformly dispersed within the boron nitride framework. Because the microcapsules already encapsulate the phase-change material, a dual-encapsulation strategy is provided at the micron scale, significantly reducing leakage of the phase-change material during phase transitions, thereby ensuring stable operation and safety of the device. Furthermore, polymer microcapsules can encapsulate different phase-change core materials. This invention demonstrates universal applicability for phase-change microcapsules at different temperatures, enabling the preparation of composite materials with varying phase-change temperatures for diverse application scenarios, achieving efficient thermal management. (IV) Description of the accompanying drawings

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0029] Figure 1 Schematic diagram of a directional freezing device according to an embodiment of the present invention.

[0030] Figure 2 This is an electron microscope image of the boron nitride / phase change microcapsule composite skeleton material prepared in Example 1.

[0031] Figure 3 This is an electron microscope image of the boron nitride / phase change microcapsule composite material prepared in Example 1. (V) Specific implementation methods

[0032] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0033] The directional freezing device used in the embodiment is as follows Figure 1 As shown, the directional freezing device is a columnar structure with a square bottom, and a bevel block is arranged inside the directional freezing device. The bevel block is fitted with the bottom and side surfaces of the directional freezing device, and the intersection line of the bevel of the bevel block and the horizontal bottom surface is fitted with one edge of the bottom surface of the directional freezing device, and the inclination angle of the straight section of the bevel block is 15°. The bottom surface of the directional freezing device is made of copper, the side surface of the directional freezing device is made of polytetrafluoroethylene, and the bevel block in the directional freezing device is made of polydimethylsiloxane.

[0034] Some of the raw materials used in the examples of the present invention are from the following sources: melamine (AR, Aladdin Reagent (China) Co., Ltd.), formaldehyde (37%, Shanghai MacLean Biochemical Technology Co., Ltd.), styrene maleic anhydride copolymer (SMA, industrial grade), paraffin wax (commercially available), boron nitride nanosheets (98.5%, commercially available), sodium carboxymethyl cellulose (CMC, 800-1200 mPa.s, Aladdin Reagent (China) Co., Ltd.), and polyvinyl alcohol 1799 (pharmaceutical grade, Aladdin Reagent (China) Co., Ltd.).

[0035] Example 1

[0036] (1) Add 1g melamine and 2g formaldehyde to 6g water, adjust the pH to 8-9 with triethanolamine, and react at 70℃ for 1h to obtain a transparent prepolymer aqueous solution. Dissolve 0.5g SMA in 25g water, adjust the pH to 4.5 with citric acid, and add 10g paraffin (phase transition temperature T m =28°C) was placed in a 70°C water bath. After the paraffin was fully melted, it was sheared at 10,000 rpm for 10 minutes to form a stable O / W dispersion. The dispersion was placed in a 70°C water bath, and the prepolymer aqueous solution was added dropwise within 30 minutes. The reaction was then continued at 70°C for 3 hours to finally obtain a phase change microcapsule emulsion. Hot ethanol aqueous solution and deionized water were used for centrifugal washing (8,000 rpm, 10 minutes, 3 times) in sequence. The purified precipitated product was collected and freeze-dried (-80°C, 0.1 mbar, 24 hours) to obtain a phase change microcapsule powder.

[0037] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of about 100 nm) and 3 g of phase change microcapsule powder were added to 18.5 g of 3 wt% CMC aqueous solution, and mechanically stirred for 30 min to obtain a dispersion, which was then fixed to 100 mL. In an ice-water bath, an ultrasonic cell disruptor was used for ultrasonic treatment in pulse mode for 1 h (power 30 W, working 12 s, rest 6 s) to obtain a boron nitride / phase change microcapsule dispersion, in which the volume fraction of boron nitride nanosheets was 2.5 vol% (the density of boron nitride nanosheets was 2.23 g / cm 3 ).

[0038] (3) The boron nitride / phase change microcapsule dispersion obtained in step (2) is poured into a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0039] (4) The frozen block material obtained in step (3) was placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals to obtain a boron nitride / phase change microcapsule porous material with a lamellar structure, the SEM image of which is shown in FIG. Figure 2 shown.

[0040] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) was placed in a mold and hot pressed at 80°C and 35 MPa for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material, the SEM image of which is shown in FIG. Figure 3 shown.

[0041] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 7.36±0.50 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 76.1 J / g.

[0042] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Subsequent images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 71.5°C within 80 seconds, and a phase transition constant-temperature plateau appeared between 28 and 32°C, which lasted for 10 seconds.

[0043] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 64.7°C.

[0044] The thermal management capabilities of the samples were evaluated using a 5G smartphone. The samples were attached to a hot area on the back of the smartphone and evenly coated with thermal grease to reduce the contact thermal resistance between the composite material and the smartphone back panel. A thermal imager was used to record the surface temperature of the samples during a 20-minute video call. For six minutes, the sample surface remained constant at 27-29°C.

[0045] Comparative Example 1

[0046] (1) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm and thickness of approximately 100 nm) were added to 18.5 g of a 3 wt% CMC aqueous solution and mechanically stirred for 30 min to obtain a dispersion. The volume was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulsed mode (power 30 W, 12 s on, 6 s off) for 1 h using an ultrasonic cell disruptor to obtain a uniformly dispersed boron nitride dispersion containing 2.5 vol% boron nitride nanosheets.

[0047] (2) Pour the boron nitride dispersion obtained in step (1) into a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material, with the freezing temperature being -198°C.

[0048] (3) The frozen block material obtained in step (2) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals to obtain a boron nitride / polymer porous material with a lamellar structure.

[0049] (4) The boron nitride / polymer porous material obtained in step (3) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / polymer block material.

[0050] The thermal conductivity of the prepared boron nitride / polymer composite was measured using a HotDisk-2500s thermal constant analyzer, resulting in a thermal conductivity of 10.65±0.54 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, and the latent heat enthalpy of the sample was not measured.

[0051] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and the first image was captured using an infrared thermal imager (Ex-XT, FLIR). Subsequent images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 71.6°C within 80 seconds, with no phase change in the constant-temperature platform region.

[0052] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 63°C.

[0053] The thermal management capabilities of the samples were evaluated using a 5G smartphone. The samples were attached to the heat-generating area on the back of the smartphone and evenly coated with thermal grease to reduce the contact thermal resistance between the composite material and the smartphone's back panel. A thermal imager recorded the sample's surface temperature during a 20-minute video call, revealing a lack of temperature control.

[0054] By comparing the experimental results with those of Example 1, it was found that the composite material without the addition of phase change microcapsules did not have energy storage properties.

[0055] Comparative Example 2

[0056] (1) Obtain phase change microcapsule powder according to step (1) of Example 1.

[0057] (2) 17 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of about 100 nm) and 3 g of phase change microcapsule powder were added to 56.5 g of 3 wt% CMC aqueous solution, mechanically stirred for 30 min to obtain a dispersion, and the volume was adjusted to 100 mL. In an ice-water bath, ultrasonic cell disruptor was used for 1 h in pulse mode (power 30 W, working 12 s, rest 6 s) to obtain a boron nitride / phase change microcapsule dispersion, in which the volume fraction of boron nitride nanosheets was 7.6 vol% (the density of boron nitride nanosheets was 2.23 g / cm 3 ).

[0058] (3) The boron nitride / phase change microcapsule dispersion obtained in step (2) is poured into a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0059] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0060] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0061] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 5.89±0.33 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 73.4 J / g.

[0062] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 66.9°C within 80 seconds, with a phase transition constant-temperature plateau appearing between 28 and 32°C for 10 seconds.

[0063] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 66°C.

[0064] By comparing the experimental results with those in Example 1, it was found that when the volume fraction of boron nitride nanosheets in the dispersion increased, the critical growth rate of ice crystals decreased, making the freezing process difficult to control, the regularity of the obtained boron nitride / phase change microcapsule composite material decreased, the thermal conductivity decreased significantly, and the heat dissipation capacity deteriorated.

[0065] Comparative Example 3

[0066] (1) Obtain phase change microcapsule powder according to step (1) of Example 1.

[0067] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness approximately 100 nm) and 3 g of phase change microcapsule powder were added to 18.5 g of a 3 wt% CMC aqueous solution and mechanically stirred for 30 min to obtain a dispersion. The volume was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulsed mode (power 30 W, 12 s on, 6 s off) for 1 h using an ultrasonic cell disruptor to obtain a boron nitride / phase change microcapsule dispersion containing 2.5 vol% boron nitride nanosheets.

[0068] (3) The boron nitride / phase change microcapsule dispersion obtained in step (2) is poured into a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0069] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0070] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 15 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0071] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 4.81±0.40 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 76.1 J / g.

[0072] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 65.3°C within 80 seconds, and a phase transition constant-temperature plateau appeared between 28 and 32°C, which lasted for 10 seconds.

[0073] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 70°C.

[0074] By comparing with the experimental results of Example 1, it was found that when the pressure during the hot pressing process decreased, the thermal conductivity coefficient decreased. This is because the degree of hot pressing decreased, the gap between layers increased, the density of the sample decreased, and the presence of air inside affected the overall thermal conductivity of the material, resulting in poor heat dissipation capacity.

[0075] Comparative Example 4

[0076] (1) Obtain phase change microcapsule powder according to step (1) of Example 1.

[0077] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of approximately 100 nm) and 3 g of phase change microcapsule powder were added to 18.5 g of a 3 wt% aqueous solution of polyvinyl alcohol 1799. The mixture was mechanically stirred for 30 min to obtain a dispersion, which was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulsed mode (power 30 W, 12 s on, 6 s off) for 1 h using an ultrasonic cell disruptor to obtain a boron nitride / phase change microcapsule dispersion containing 2.5 vol% boron nitride nanosheets.

[0078] (3) The boron nitride / phase change microcapsule dispersion obtained in step (2) is poured into a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0079] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0080] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0081] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 7.43±0.39 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 74.2 J / g.

[0082] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 70.3°C within 80 seconds, and a phase transition constant-temperature plateau appeared between 28 and 32°C, which lasted for 10 seconds.

[0083] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 61°C.

[0084] By comparing the experimental results with those of Example 1, it was found that when PVA was used as the polymer binder, PVA would shrink and collapse during the freezing process, the layered structure of the resulting boron nitride / phase change microcapsule composite material would shrink, the thermal conductivity would decrease significantly, and the heat dissipation capacity would deteriorate.

[0085] Comparative Example 5

[0086] (1) Obtain phase change microcapsule powder according to step (1) of Example 1.

[0087] (2) 5.5 g of boron nitride nanosheets (average lateral size of 1 μm, thickness of about 100 nm) and 3 g of phase change microcapsule powder were added to 18.5 g of 3 wt% sodium carboxymethyl cellulose aqueous solution, and mechanically stirred for 30 min to obtain a dispersion, which was then fixed to 100 mL. In an ice-water bath, an ultrasonic cell disruptor was used for ultrasonic treatment in pulse mode for 1 h (power 30 W, working 12 s, rest 6 s) to obtain a boron nitride / phase change microcapsule dispersion, in which the volume fraction of boron nitride nanosheets was 2.5 vol% (the density of the boron nitride nanosheets was 2.23 g / cm 3 ).

[0088] (3) The boron nitride / phase change microcapsule dispersion obtained in step (2) is poured into a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0089] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0090] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0091] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 1.12±0.23 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 75.7 J / g.

[0092] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 53.2°C within 80 seconds, with a phase transition constant-temperature plateau appearing between 28 and 32°C for 10 seconds.

[0093] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 78°C.

[0094] By comparing the experimental results with those of Example 1, it was found that when small-sized boron nitride nanosheets (1 μm) were used, the thermal conductivity of the obtained boron nitride / phase change microcapsule composite material decreased significantly, and the heat dissipation capacity became significantly worse.

[0095] Comparative Example 6

[0096] (1) Obtain phase change microcapsule powder according to step (1) of Example 1.

[0097] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of approximately 100 nm) and 3 g of phase change microcapsule powder were added to 18.5 g of a 3 wt% sodium carboxymethyl cellulose aqueous solution and mechanically stirred for 30 min to prepare a dispersion, which was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulsed mode (power 30 W, 12 s on, 6 s off) for 1 h using an ultrasonic cell disruptor to obtain a boron nitride / phase change microcapsule dispersion containing 2.5 vol% boron nitride nanosheets.

[0098] (3) Pour the boron nitride / phase change microcapsule dispersion obtained in step (2) into a centrifuge tube mold and directly freeze it using liquid nitrogen until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0099] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a random structure.

[0100] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0101] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 4.56±0.21 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 76.0 J / g.

[0102] The sample was placed on an intelligent constant-temperature heating platform preheated at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 63.2°C within 80 seconds, and a phase transition constant-temperature plateau appeared between 28 and 32°C, which lasted for 10 seconds.

[0103] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 75°C.

[0104] By comparing and analyzing the experimental results with those of Example 1, it is found that when liquid nitrogen is used directly for freezing, due to the randomness and uncontrollability of the ice crystal growth process, the obtained boron nitride / phase change microcapsule composite material exhibits a disordered microstructure, which significantly reduces the thermal conductivity and thus affects the heat dissipation capacity of the material.

[0105] Example 2

[0106] (1) Obtain phase change microcapsule powder according to step (1) of Example 1.

[0107] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of approximately 100 nm) and 5.5 g of phase change microcapsule powder were added to 18.5 g of a 3 wt% sodium carboxymethyl cellulose aqueous solution and mechanically stirred for 30 min to obtain a dispersion. The volume was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulse mode (power 30 W, 12 s on, 6 s off) using an ultrasonic cell disruptor for 1 h to obtain a boron nitride / phase change microcapsule dispersion containing 2.5 vol% boron nitride nanosheets.

[0108] (3) Pour the boron nitride / phase change microcapsule dispersion obtained in step (2) into a mold of a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0109] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0110] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0111] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 4.36±0.41 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 110.3 J / g.

[0112] The sample was placed on an intelligent constant-temperature heating platform preheated at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 62.2°C within 80 seconds, and a phase transition constant-temperature plateau appeared between 28 and 32°C, which lasted for 30 seconds.

[0113] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 73°C.

[0114] Example 3

[0115] (1) Obtain phase change microcapsule powder according to step (1) of Example 1.

[0116] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of approximately 100 nm) and 16.5 g of phase change microcapsule powder were added to 18.5 g of a 3 wt% sodium carboxymethyl cellulose aqueous solution and mechanically stirred for 30 min to obtain a dispersion. The volume was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulsed mode (power 30 W, 12 s on, 6 s off) for 1 h using an ultrasonic cell disruptor to obtain a boron nitride / phase change microcapsule dispersion containing 2.5 vol% boron nitride nanosheets.

[0117] (3) Pour the boron nitride / phase change microcapsule dispersion obtained in step (2) into a mold of a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0118] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0119] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0120] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 1.14±0.22 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 163.2 J / g.

[0121] The sample was placed on an intelligent constant-temperature heating platform preheated at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 52.2°C within 80 seconds, and a phase transition constant-temperature plateau appeared between 28 and 32°C, which lasted for 50 seconds.

[0122] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 78°C.

[0123] Example 4

[0124] (1) According to step (1) of Example 1, phase change microcapsule powder is obtained, except that paraffin wax (phase change temperature T m =28℃) is replaced by paraffin (phase transition temperature T m =44℃).

[0125] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of approximately 100 nm) and 3 g of phase change microcapsule powder were added to 18.5 g of a 3 wt% sodium carboxymethyl cellulose aqueous solution and mechanically stirred for 30 min to prepare a dispersion, which was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulsed mode (power 30 W, 12 s on, 6 s off) for 1 h using an ultrasonic cell disruptor to obtain a boron nitride / phase change microcapsule dispersion containing 2.5 vol% boron nitride nanosheets.

[0126] (3) Pour the boron nitride / phase change microcapsule dispersion obtained in step (2) into a mold of a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0127] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0128] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0129] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 7.96±0.43 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 87.7 J / g.

[0130] The sample was placed on an intelligent constant-temperature heating platform preheated at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 63.9°C within 80 seconds, with a phase transition constant-temperature plateau appearing between 28 and 32°C for 20 seconds.

[0131] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 62°C.

[0132] Example 5

[0133] (1) According to step (1) of Example 1, phase change microcapsule powder is obtained, except that paraffin wax (phase change temperature T m =28℃) is replaced by paraffin (phase transition temperature T m =65℃).

[0134] (2) 5.5 g of boron nitride nanosheets (average lateral size of 5 μm, thickness of approximately 100 nm) and 3 g of phase change microcapsule powder were added to 18.5 g of a 3 wt% sodium carboxymethyl cellulose aqueous solution and mechanically stirred for 30 min to prepare a dispersion, which was then fixed to 100 mL. In an ice-water bath, the mixture was sonicated in pulsed mode (power 30 W, 12 s on, 6 s off) for 1 h using an ultrasonic cell disruptor to obtain a boron nitride / phase change microcapsule dispersion containing 2.5 vol% boron nitride nanosheets.

[0135] (3) Pour the boron nitride / phase change microcapsule dispersion obtained in step (2) into a mold of a directional freezing device for directional freezing until the liquid is completely converted into a solid to obtain a frozen block material at a freezing temperature of -198°C.

[0136] (4) The frozen block material obtained in step (3) is placed in a freeze dryer and freeze-dried at -80°C for 48 hours to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous material with a lamellar structure.

[0137] (5) The boron nitride / phase change microcapsule porous material obtained in step (4) is placed in a mold and hot-pressed at 80° C. and 35 MPa pressure for 15 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

[0138] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 7.89±0.53 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 72.0 J / g.

[0139] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 67.9°C within 80 seconds, with a phase transition constant-temperature plateau at 57-63°C, which lasted for 30 seconds.

[0140] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 59°C.

[0141] Comparative Example 7

[0142] (1) According to step (1) of Example 1, phase change microcapsule powder was obtained, placed in a mold, and hot pressed at 80° C. and 35 MPa pressure for 15 min to obtain a dense phase change microcapsule block material.

[0143] The thermal conductivity of the prepared boron nitride / phase change microcapsule composite was measured using a HotDisk-2500s thermal constant analyzer, revealing a thermal conductivity of 0.18±0.04 W / mK. The energy storage performance of the resulting material was evaluated using a Q2000 differential scanning calorimeter, revealing a latent heat enthalpy of 219.6 J / g.

[0144] The sample was placed on a preheated intelligent constant-temperature heating platform at 80°C. Timing began the moment the sample contacted the heating platform, and an infrared thermal imager (Ex-XT, FLIR) captured the first image. Thereafter, images were taken every 5 seconds, for a total of approximately 200 seconds. The sample heated to 43.6°C within 80 seconds, and a phase transition constant-temperature plateau zone appeared between 26 and 35°C, which lasted for 60 seconds.

[0145] The sample was placed between the bottom of a 2×2cm, 10W LED lamp module and an aluminum heat sink, acting as a heat sink between the heat sink and the heating element. Thermal grease was evenly applied to eliminate contact thermal resistance. A Ti-400 thermal infrared imager was used to capture the LED lamp during operation, ultimately stabilizing the LED surface temperature at 87°C.

[0146] Compared with the results of Examples 1, 2, and 3, it was found that as the proportion of boron nitride in the composite material system increased, the thermal conductivity of the boron nitride / phase change microcapsule composite material increased accordingly.

[0147] The above embodiments are only for illustration of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solution of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for preparing a boron nitride / phase change microcapsule composite material, characterized in that: The preparation method comprises the following steps: (1) mixing boron nitride nanosheets, phase change microcapsules, a polymer binder, and water, and stirring thoroughly to obtain a dispersion; then, ultrasonically treating the dispersion in an ice-water bath using an ultrasonic cell disruptor in a pulse mode to obtain a boron nitride / phase change microcapsule dispersion; wherein the phase change temperature of the phase change material in the phase change microcapsules is between 20° C. and 95° C.; (2) injecting the boron nitride / phase change microcapsule dispersion into a directional freezing device, placing the directional freezing device in a refrigerant at -20 to -200°C for directional freezing until the liquid is completely converted into a solid, thereby obtaining a frozen block material; thereafter, freeze-drying the material to remove ice crystals, thereby obtaining a boron nitride / phase change microcapsule porous skeleton material having a lamellar structure; the directional freezing device is a columnar structure having a square, rectangular, trapezoidal or parallelogram bottom surface, wherein a bevel block is provided inside the directional freezing device, wherein the bevel block is fitted with the bottom and side surfaces of the directional freezing device, and the intersection line of the bevel block and the horizontal bottom surface is fitted with one of the two parallel sides of the bottom surface of the directional freezing device, and the inclination angle of the straight section of the bevel block is in the range of 5 to 45°, the bottom surface of the directional freezing device is made of a metal with good thermal conductivity, the side surface of the directional freezing device is made of polytetrafluoroethylene, and the bevel block in the directional freezing device is made of polydimethylsiloxane; (3) placing the boron nitride / phase change microcapsule porous material in a mold, and hot pressing it at a temperature of 45 to 110° C. and a pressure of 10 to 40 MPa for 5 to 45 minutes to obtain a dense boron nitride / phase change microcapsule composite material.

2. The preparation method according to claim 1, wherein: In step (1), the mass ratio of boron nitride nanosheets to polymer binder is 9-12:1; taking the total mass of boron nitride nanosheets and phase change microcapsules as 100%, the mass ratio of boron nitride nanosheets to phase change microcapsules is 20-80%:20-80%.

3. The preparation method according to claim 1, wherein: In step (1), the average lateral size of the boron nitride nanosheets is between 1 and 10 μm, preferably between 4 and 6 μm.

4. The preparation method according to claim 1, wherein: In step (1), the polymer binder is selected from at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, styrene-maleic anhydride copolymer, polyacrylamide, and methyl cellulose.

5. The preparation method according to claim 1, wherein: In step (1), the volume fraction of the boron nitride nanosheets in the boron nitride / phase change microcapsule dispersion is 2.0 to 7.5 vol%, more preferably 2.0 to 3.0 vol%, and most preferably 2.5 vol%.

6. The preparation method according to claim 1, wherein: In step (3), the hot pressing temperature is 50-100°C, preferably 70-90°C; the pressure is 15-40 MPa, preferably 30-40 MPa; the time is 5-30 min, preferably 10-20 min; the most preferred hot pressing temperature is 80°C, the pressure is 35 MPa, and the time is 15 min.

7. A boron nitride / phase change microcapsule composite material, prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the boron nitride / phase change microcapsule composite material as claimed in claim 7 as a thermal interface material.

9. An electronic device comprising a heat dissipation device and a heating device, wherein the boron nitride / phase change microcapsule composite material according to claim 7 is arranged between the heat dissipation device and the heating device as a thermal interface material.

10. An intelligent communication device, wherein the boron nitride / phase change microcapsule composite material according to claim 7 is provided as a thermal interface material in a heating area thereof.

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