Phase-change high-thermal-conductivity material with efficient thermal management capability and preparation method of phase-change high-thermal-conductivity material

Abstract

The invention belongs to the technical field of functional composite materials, and particularly relates to a phase-change high-thermal-conductivity material with efficient thermal management capability and a preparation method thereof. The phase-change high-thermal-conductivity material is prepared from the following raw materials: 40 to 45 percent of biomass charcoal, 10 to 15 percent of carbon nanotubes, 0.8 to 1.0 percent of a KH550 coupling agent, 0.3 to 0.6 percent of a KH560 coupling agent, 0.8 to 1.0 percent of a dispersing agent, 35 to 40 percent of a paraffin matrix and 3 to 5 percent of boron nitride nanosheets. By combining the stacking and filling of the boron nitride nanosheets and the bridging effect of the CNT, the thermal conductivity upper limit caused by disordered dispersion and interface scattering of traditional epoxy resin is broken through, and the thermal conductivity is improved by 76%-345%; an all-insulation filler system (BN / biomass charcoal) is adopted, so that the common electric conduction problem of a high-thermal-conductivity material is overcome; meanwhile, the paraffin base body endows the material with flexibility, the rigidity limitation of a traditional graphite material is broken through, and the material is adaptive to emerging scenes such as flexible electronics and special-shaped battery modules.

Description

Technical Field

[0001] The present invention relates to the technical field of functional composite materials, and in particular to a phase-change high thermal conductivity material with efficient thermal management capability and a preparation method thereof. Background Art

[0002] With the continuous increase in the power density of electronic devices and the rapid development of new energy technologies, efficient thermal management materials have become the core bottleneck restricting the performance and reliability of equipment. Although traditional phase change materials (such as paraffin and polyethylene glycol) have excellent phase change latent heat and temperature control capabilities, their intrinsic thermal conductivity is extremely low (usually <0.3W / m·K), which makes it difficult to meet the demand for rapid heat conduction in high-power scenarios. In order to improve thermal conductivity, metal particles (such as aluminum powder, copper powder), carbon materials (graphene, carbon fiber) or ceramic fillers (aluminum nitride, boron nitride) are often added to construct a thermal conductive network. These materials are often expensive and cannot be mass-produced and commercialized. For example, in the following patents, single-scale fillers are prone to the following problems:

[0003] Patent CN106626626: The high graphite content (70%-95%) makes it unsuitable for use in insulation applications such as electronic devices. The high graphite content also increases the material's brittleness and poor impact resistance. Furthermore, pure acid treatment of the nanofiller only improves dispersion and does not achieve directional bonding with the coupling agent (it relies solely on physical adsorption).

[0004] Patent CN101550331: uses Al powder as the main body, but Al is easily oxidized and conductive, there is a risk of short circuit or corrosion at high temperatures, it is prone to failure in a humid environment, the lifespan is unstable, and the thermal conductivity in the vertical direction is as high as 356W / m·K, but the in-plane thermal conductivity is extremely low (1-3W / m·K), which limits the applicable scenarios.

[0005] Patent CN116285564: Although it has insulation advantages, it is limited by the low thermal conductivity of the resin matrix and the upper limit of filler loading (≤40%). Its thermal conductivity is mostly below 5W / m·K. In addition, the volatilization of the solvent (VOC emissions) and the complex curing process (multi-step high-temperature baking) restrict mass production efficiency.

[0006] Therefore, breaking the performance contradiction between insulation and thermal conductivity, optimizing the efficiency of filler network construction, reducing process complexity, and reducing cost consumption have become the core challenges in this field. Summary of the Invention

[0007] In response to the above-mentioned problems, the present invention provides a phase-change high thermal conductivity material with efficient thermal management capabilities and a preparation method thereof. The present invention proposes an innovative solution based on a micron / nano dual-scale filler synergistic strategy: insulating biochar is used as a micron-scale skeleton, and the surface is treated with a coupling agent KH550 (3-aminopropyltriethoxysilane) to achieve efficient interface bonding with BN nanosheets (boron nitride nanosheets). At the same time, by introducing an acidified coupling agent KH560 (γ-glycidyloxypropyltrimethoxysilane), it is directionally coupled with CNTs (carbon nanotubes) as a nanoscale reinforcement, and a three-dimensional interpenetrating thermal conductive network is constructed in a paraffin matrix; the process is mainly based on a low-temperature melt blending process (80°C), supplemented by step-by-step shear dispersion and vacuum degassing, achieving high filler loading (≥40%) and low interfacial thermal resistance.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A phase-change, high-thermal-conductivity material with efficient thermal management capabilities comprises the following raw materials in weight percentage: 40-45% biochar, 10-15% carbon nanotubes, 0.8-1.0% KH550 coupling agent, 0.3-0.6% KH560 coupling agent, 0.8-1.0% dispersant, 35-40% paraffin matrix, and 3-5% boron nitride nanosheets. Biochar increases the specific surface area, improving dispersibility and interfacial contact area. Coupling agent KH550 is used to enhance the connectivity of biochar / BN, while coupling agent KH560 is used to modify the surface of carbon nanotubes (CNTs). Dispersants are used to balance dispersibility and reduce residual effects. Boron nitride (BN) is introduced to fill the gaps between the flake / fiber fillers, allowing them to construct a three-dimensional thermal conductive network, enhancing overall thermal conductivity.

[0010] In the present invention, further specifically, the phase change high thermal conductivity material with efficient thermal management capability includes the following raw materials in weight percentage: 41.46% biochar, 12.20% carbon nanotubes, 0.98% KH550 coupling agent, 0.49% KH560 coupling agent, 0.98% dispersant, 39.02% paraffin matrix and 4.88% boron nitride nanosheets.

[0011] In the present invention, the phase-change high thermal conductivity material with efficient thermal management capabilities further includes 2-4% graphene nanosheets. The graphene nanosheets serve to introduce high thermal conductivity two-dimensional fillers (in-plane thermal conductivity > 3000 W / m·K) to synergistically improve the continuity of the thermal network.

[0012] In the present invention, further, the phase change high thermal conductivity material with efficient thermal management capability further comprises 7-9% hollow glass microspheres as low-density fillers. The density of the hollow glass microspheres is 0.6 g / cm 3 , particle size is 20-50μm.

[0013] In the present invention, further, the hollow glass microspheres are treated with KH570 coupling agent.

[0014] In the present invention, the carbon nanotubes are further subjected to acidification and coupling agent treatment. Specifically, the carbon nanotubes are added to a concentrated H2SO4 / HNO3 mixed acid solution (3:1 by volume), ultrasonically treated at 60°C for 2 hours, centrifuged and washed until neutral, and dried. Acidification enhances surface activity and allows for directional coupling with KH560, reducing aggregation and improving interfacial bonding strength.

[0015] The present invention also provides a method for preparing the above-mentioned phase-change high thermal conductivity material with efficient thermal management capability, comprising the following steps:

[0016] (1) placing high-temperature graphitized biochar in a ball mill to obtain biochar powder, mixing the milled biochar powder with boron nitride nanosheets, adding KH550 coupling agent and anhydrous ethanol, ultrasonically dispersing for 30-40 minutes, and vacuum drying to obtain a modified biochar / BN composite filler for later use;

[0017] (2) adding carbon nanotubes to a concentrated H2SO4 / HNO3 mixture and ultrasonically treating the mixture for 2-2.5 hours, washing the mixture by centrifugation until neutral, and drying the mixture to obtain acidified carbon nanotubes; dispersing the acidified carbon nanotubes in a mixture of anhydrous ethanol and a dispersant, adding a KH560 coupling agent, ultrasonically treating the mixture for 1 hour, and finally vacuum drying the mixture to obtain a modified carbon nanotube dispersion;

[0018] (3) The paraffin matrix, modified biochar / BN composite filler and modified carbon nanotube dispersion were mixed and extruded using a twin-screw extruder through dual-scale fillers and melt blending. The extruded material was injected into a preheated mold at 80°C, a pressure of 5 MPa was applied, and after maintaining the pressure for 1 hour, it was transferred to a vacuum oven and cured for 2 hours to obtain a phase change high thermal conductivity material with efficient thermal management capabilities.

[0019] In the present invention, further, the ball-to-material ratio in the ball mill in step (1) is 10:1, and the powder obtained after ball milling in the ball mill is a micron-sized powder with D50<10μm.

[0020] In the present invention, further, the specific operating steps of the twin-screw extruder in step (3) are as follows:

[0021] A. Parameter Setting: Add the paraffin wax matrix into the melting section of the twin-screw extruder through the main feed port; start the heating system, raise the temperature to 80°C and maintain it at this temperature for 10 minutes to completely melt the paraffin wax into a liquid state; the melted paraffin wax matrix is conveyed to the mixing section by the screw, with the main screw speed at 200 rpm;

[0022] B. Parameter setting: Increase the speed to 300-400 rpm, add the modified biochar / BN composite filler evenly into the mixing section at a rate of 5 g / min through the side feeder, and at the same time, start the high shear dispersion module and continue for 10 minutes;

[0023] C. Parameter Settings: Increase the speed to 600 rpm and add the modified carbon nanotube dispersion as a suspension to the mixing section via the second side feeder. Start the kneading block of the twin-screw extruder and apply local high shear force (800 rpm) to forcibly break up CNT agglomerates. Disperse for 15-20 minutes, pausing the screw every 3-5 minutes to clean any CNT fibers remaining in the kneading block area.

[0024] D. Parameter setting: Close all feeding ports and keep the screw running at a low speed (300rpm) to ensure uniform material flow; open the vacuum degassing valve (-0.1MPa) for 10-15 minutes to remove bubbles and volatiles from the melt; observe the melt state in the sight glass; if there are no bubbles escaping and the surface is smooth, it is qualified;

[0025] Finally, the extruded material was injected into a preheated mold at 80°C, a pressure of 5 MPa was applied, and after maintaining the pressure for 1 hour, it was transferred to a vacuum oven and cured at 150°C for 2 hours.

[0026] By adopting the above technical solution, the present invention achieves at least the following beneficial effects:

[0027] (1) The present invention pre-constructs a thermal conductivity path through a biomass carbon micron skeleton, combines the stacking filling of boron nitride nanosheets with the bridging effect of CNTs, and breaks through the thermal conductivity upper limit of traditional epoxy resins caused by disordered dispersion and interface scattering. The longitudinal thermal conductivity is increased to 8-15 W / m·K, and the transverse (thickness direction) thermal conductivity is increased to 2-4 W / m·K.

[0028] (2) The present invention adopts a fully insulating filler system (BN / biochar) to replace graphite, overcoming the common conductive problem of high thermal conductivity materials; at the same time, the paraffin matrix gives the material flexibility, breaking through the rigidity limitations of traditional graphite materials, and adapting to emerging scenarios such as flexible electronics and special-shaped battery modules.

[0029] (3) The present invention replaces the solvent-based dispersion system with low-temperature melt blending to avoid VOC pollution and solvent recovery costs. At the same time, the use of non-metallic materials as the main ingredients avoids performance degradation caused by metal oxidation and extends the service life to more than twice that of traditional materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 4 is a comparison chart of thermal conductivity of three embodiments of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing a phase-change high thermal conductivity material with efficient thermal management capability comprises the following steps:

[0034] (1) 75 g of high-temperature graphitized biochar was placed in a ball mill, and zirconium oxide balls (ball-to-material ratio 10:1) were added. The mixture was ball milled at 300 rpm for 4 hours to obtain a micron-sized powder with a D50 (median particle size) <10 μm. The ball-milled biochar was then mixed with 15 g of boron nitride (BN) nanosheets and 5 g of graphene nanosheets. 3 g of KH550 coupling agent and 60 ml of anhydrous ethanol were added, and the mixture was ultrasonically dispersed for 40 minutes. The mixture was vacuum dried at 80°C for 12 hours to obtain a KH550-modified biochar / BN composite filler for later use.

[0035] (2) 35 g of CNTs were added to a concentrated H2SO4 / HNO3 (3:1 volume ratio) mixture, ultrasonically treated at 60°C for 2 h, centrifuged and washed until neutral, and dried at 80°C. The acidified CNTs were dispersed in a mixture of 6 g of anhydrous ethanol and 3 g of dispersant Triton X-100 (polyethylene glycol octylphenyl ether), 1.5 g of KH560 was added, ultrasonically treated for 1.5 h, and finally vacuum dried at 80°C for 8 h to obtain a KH560-modified CNTs dispersion.

[0036] (3) The paraffin matrix, modified biochar / BN composite filler and modified carbon nanotube dispersion were mixed and extruded using a twin-screw extruder through dual-scale filler and melt blending.

[0037] The following specific operations were carried out in a twin-screw extruder (L / D=40:1, containing a kneading block unit):

[0038] A. Parameter Settings: Add 70g of paraffin wax matrix into the melting section of the twin-screw extruder through the main feed port. Start the heating system, raise the temperature to 80°C and maintain it at this temperature for 10 minutes to completely melt the paraffin wax into a liquid state. The melted paraffin wax matrix is conveyed to the mixing section by the screw, with the main screw speed at 200 rpm.

[0039] B. Parameter setting: Increase the speed to 400 rpm, and evenly add the modified biochar / BN composite filler to the mixing section at a rate of 5 g / min through the side feeder. At the same time, start the high shear dispersion module and continue for 10 minutes;

[0040] C. Parameter Settings: Increase the speed to 600 rpm and add the modified CNT dispersion as a suspension to the mixing section via the second side feeder. Start the kneading block of the twin-screw extruder and apply local high shear force (1000 rpm) to forcibly break up CNT agglomerates. Disperse for 20 minutes, pausing the screw every 3 minutes to clean any CNT fibers remaining in the kneading block.

[0041] D. Parameter setting: Close all feeding ports and keep the screw running at a low speed (300 rpm) to ensure uniform material flow; open the vacuum degassing valve (-0.1 MPa) for 15 minutes to remove bubbles and volatiles from the melt; observe the melt state in the sight glass; if there are no bubbles escaping and the surface is smooth, it is qualified;

[0042] Finally, the extruded material was injected into a preheated mold at 80°C, a pressure of 5 MPa was applied, and after maintaining the pressure for 1 hour, it was transferred to a vacuum oven and cured at 150°C for 2 hours (vacuum degree ≤ 10-3 Pa).

[0043] Through the above steps, after relevant performance testing and verification, a longitudinal thermal conductivity of 10.5-11.8W / m·K, a transverse thermal conductivity of 5.2-6.0W / m·K, and a density of 1.65-1.75g / cm 3 , a phase change material with a compressive strength of 40-60MPa. The micromorphology of the prepared phase change high thermal conductivity material is shown in the figure Figure 1 shown.

[0044] Example 2

[0045] A method for preparing a phase-change high thermal conductivity material with efficient thermal management capability comprises the following steps:

[0046] (1) Mix 15g of hollow glass microspheres with 1g of KH570 and 30ml of ethanol, ultrasonically treat for 20 minutes, and dry at 60℃ for 6 hours. Place 60g of high-temperature graphitized biochar in a ball mill, add zirconium oxide balls (ball-to-material ratio 10:1), and ball mill at 300rpm for 4 hours to obtain a micron-sized powder with a D50 (median particle size) <10μm. The ball-milled biochar is mixed with 10g of boron nitride (BN) nanosheets, 1.5g of KH550 coupling agent and 50ml of anhydrous ethanol are added, and ultrasonic dispersion is performed for 40 minutes. Dry in a vacuum at 80℃ for 12 hours to obtain a KH550-modified biochar / BN composite filler for later use.

[0047] (2) 20 g of CNTs were added to a concentrated H2SO4 / HNO3 (3:1 volume ratio) mixture, ultrasonically treated at 60°C for 2 h, washed by centrifugation until neutral, and dried at 80°C. The acidified CNTs were dispersed in a mixture of 6 g of anhydrous ethanol and 3 g of dispersant Triton X-100, 1.5 g of KH560 was added, ultrasonically treated for 1.5 h, and finally dried at 80°C in a vacuum for 8 h to obtain a KH560-modified CNT dispersion.

[0048] (3) The paraffin matrix, modified biochar / BN composite filler and modified carbon nanotube dispersion were mixed and extruded using a twin-screw extruder through dual-scale filler and melt blending.

[0049] The following specific operations were carried out in a twin-screw extruder (L / D=40:1, containing a kneading block unit):

[0050] A. Parameter Settings: Add 60g of paraffin wax matrix into the melting section of the twin-screw extruder through the main feed port. Start the heating system, raise the temperature to 80°C and maintain it at this temperature for 10 minutes to completely melt the paraffin wax into a liquid state. The melted paraffin wax matrix is conveyed to the mixing section by the screw, with the main screw speed at 200 rpm.

[0051] B. Parameter setting: Increase the speed to 300 rpm, and evenly add the modified biochar / BN composite filler to the mixing section at a rate of 5 g / min through the side feeder. At the same time, start the high shear dispersion module and continue for 10 minutes;

[0052] C. Parameter Settings: Increase the speed to 600 rpm and add the modified carbon nanotube dispersion as a suspension to the mixing section via the second side feeder. Start the kneading block of the twin-screw extruder and apply local high shear force (800 rpm) to forcibly break up CNT agglomerates. Disperse for 15 minutes, pausing the screw every 3 minutes to clean any CNT fibers remaining in the kneading block.

[0053] D. Parameter setting: Close all feeding ports and keep the screw running at a low speed (300 rpm) to ensure uniform material flow; open the vacuum degassing valve (-0.1 MPa) for 15 minutes to remove bubbles and volatiles from the melt; observe the melt state in the sight glass; if there are no bubbles escaping and the surface is smooth, it is qualified;

[0054] Finally, the extruded material was injected into a preheated mold at 80°C, and a pressure of 5 MPa was applied. After maintaining the pressure for 1 hour, the material was transferred to a vacuum oven and cured at 150°C for 2 hours (vacuum degree ≤ 10-3 Pa). Alternatively, the melt-blended extruded material was injected into a mold and foamed at 80°C for 10 minutes (with 0.5 g azodicarbonamide as the blowing agent) to form a porous structure.

[0055] Through the above steps, after relevant performance testing and verification, a longitudinal thermal conductivity of 4.8-5.5W / m·k, a transverse thermal conductivity of 2.5-3.0W / m·k, and a density of 1.05-1.18g / cm 3 , low-density, high thermal conductivity material with a compressive strength of 15-25MPa.

[0056] Example 3

[0057] A method for preparing a phase-change high thermal conductivity material with efficient thermal management capability comprises the following steps:

[0058] (1) 85 g of high-temperature graphitized biochar was placed in a ball mill, and zirconium oxide balls (ball-to-material ratio 10:1) were added. The mixture was ball milled at 300 rpm for 4 hours to obtain a micron-sized powder with a D50 (median particle size) <10 μm. The ball-milled biochar was then mixed with 10 g of boron nitride (BN) nanosheets, 2 g of KH550 coupling agent, and 50 ml of anhydrous ethanol. The mixture was ultrasonically dispersed for 30 minutes. The mixture was vacuum dried at 60°C for 12 hours to obtain a KH550-modified biochar / BN composite filler for later use.

[0059] (2) 25 g of CNTs were added to a concentrated H2SO4 / HNO3 (3:1 volume ratio) mixture, ultrasonically treated at 60°C for 2 h, washed by centrifugation until neutral, and dried at 80°C. The acidified CNTs were dispersed in a mixture of 5 g of anhydrous ethanol and 2 g of dispersant Triton X-100, 1 g of KH560 was added, ultrasonically treated for 1 h, and finally dried in a vacuum at 60°C for 8 h to obtain a KH560-modified CNT dispersion.

[0060] (3) The paraffin matrix, modified biochar / BN composite filler and modified CNTs dispersion were mixed and extruded using a twin-screw extruder through dual-scale filler and melt blending.

[0061] The following specific operations were carried out in a twin-screw extruder (L / D=40:1, containing a kneading block unit):

[0062] A. Parameter Settings: Add 80g of paraffin wax matrix into the melting section of the twin-screw extruder through the main feed port. Start the heating system, raise the temperature to 80°C and maintain it at this temperature for 10 minutes to completely melt the paraffin wax into a liquid state. The melted paraffin wax matrix is conveyed to the mixing section by the screw, with the main screw speed at 200 rpm.

[0063] B. Parameter setting: Increase the speed to 400 rpm, and evenly add the modified biochar / BN composite filler to the mixing section at a rate of 5 g / min through the side feeder. At the same time, start the high shear dispersion module and continue for 10 minutes;

[0064] C. Parameter Settings: Increase the speed to 600 rpm and add the modified carbon nanotube dispersion as a suspension to the mixing section via the second side feeder. Start the kneading block of the twin-screw extruder and apply local high shear force (800 rpm) to forcibly break up CNT agglomerates. Disperse for 15 minutes, pausing the screw every 5 minutes to clean any CNT fibers remaining in the kneading block.

[0065] D. Parameter setting: Close all feeding ports and keep the screw running at a low speed (300 rpm) to ensure uniform material flow; open the vacuum degassing valve (-0.1 MPa) for 10 minutes to remove bubbles and volatiles from the melt; observe the melt state in the sight glass; if there are no bubbles escaping and the surface is smooth, it is qualified;

[0066] Finally, the extruded material was injected into a preheated mold at 80°C, a pressure of 5 MPa was applied, and after maintaining the pressure for 1 hour, it was transferred to a vacuum oven and cured at 150°C for 2 hours (vacuum degree ≤ 10-3 Pa).

[0067] Through the above steps, efficient dispersion and interface bonding of micron / nano dual-scale fillers can be achieved, and finally a longitudinal thermal conductivity of 7.0-8.5W / m·K, a transverse thermal conductivity of 4.5-6.0W / m·K, and a density of 1.2-1.5g / cm 3 , a high thermal conductivity material with a compressive strength of 30-45MPa. The micromorphology of the prepared phase change high thermal conductivity material is shown in the figure Figure 1 shown.

[0068] The thermal conductivity comparison diagram of the three embodiments of the present invention is as follows: Figure 1 As shown. Figure 1 It can be seen that the present invention pre-constructs a thermal conductive path through the biomass carbon micro-skeleton, combines the stacking filling of boron nitride nanosheets with the bridging effect of CNTs, and breaks through the thermal conductivity upper limit of traditional epoxy resin caused by disordered dispersion and interface scattering. In addition, the introduction of graphene nanosheets, which serve as high thermal conductivity two-dimensional fillers (in-plane thermal conductivity >3000W / m·K), synergistically improves the continuity of the thermal conductive network, resulting in a significant improvement in thermal conductivity.

[0069] Therefore, compared with the existing technology, the present invention improves the thermal conductivity to 7.56W / m·K while maintaining high insulation (breakdown voltage > 30kV / mm). In addition, the process is solvent-free and energy consumption is reduced by more than 60%. It provides an innovative thermal management solution that balances performance and cost for scenarios such as new energy battery modules and flexible electronic devices.

Claims

1. A phase change high thermal conductivity material with efficient thermal management capability, characterized in that: The invention comprises the following raw materials in weight percentage: 40-45% of biochar, 10-15% of carbon nanotubes, 0.8-1.0% of KH550 coupling agent, 0.3-0.6% of KH560 coupling agent, 0.8-1.0% of dispersant, 35-40% of paraffin matrix and 3-5% of boron nitride nanosheets.

2. The phase change high thermal conductivity material with efficient thermal management capability according to claim 1, characterized in that: The invention comprises the following raw materials in weight percentage: 41.46% of biochar, 12.20% of carbon nanotubes, 0.98% of KH550 coupling agent, 0.49% of KH560 coupling agent, 0.98% of dispersant, 39.02% of paraffin matrix and 4.88% of boron nitride nanosheets.

3. The phase change high thermal conductivity material with efficient thermal management capability according to claim 1 or 2, characterized in that: Also included are 2-4% graphene nanosheets.

4. The phase change high thermal conductivity material with efficient thermal management capability according to claim 1 or 2, characterized in that: Also includes hollow glass microspheres 7-9%.

5. The phase change high thermal conductivity material with efficient thermal management capability according to claim 4, characterized in that: The hollow glass microspheres are treated with KH570 coupling agent.

6. The phase change high thermal conductivity material with efficient thermal management capability according to claim 1, characterized in that: The carbon nanotubes need to be acidified and treated with a coupling agent. Specifically, the acidification includes adding the carbon nanotubes to a mixed acid solution composed of concentrated H2SO4 / HNO3 in a volume ratio of 3:1, ultrasonically treating at 60°C for 2 hours, centrifuging and washing until neutral, and drying.

7. A method for preparing a phase-change high thermal conductivity material with efficient thermal management capability according to any one of claims 1 to 6, characterized in that: The steps include: (1) placing graphitized biochar in a ball mill to obtain biochar powder, mixing the milled biochar powder with boron nitride nanosheets, adding KH550 coupling agent and anhydrous ethanol, ultrasonically dispersing for 30-40 minutes, and vacuum drying to obtain a modified biochar / BN composite filler for later use; (2) adding carbon nanotubes to a concentrated H2SO4 / HNO3 mixture and ultrasonically treating the mixture for 2-2.5 hours, washing the mixture by centrifugation until neutral, and drying the mixture to obtain acidified carbon nanotubes; dispersing the acidified carbon nanotubes in a mixture of anhydrous ethanol and a dispersant, adding a KH560 coupling agent, ultrasonically treating the mixture for 1 hour, and finally vacuum drying the mixture to obtain a modified carbon nanotube dispersion; (3) The paraffin matrix, modified biochar / BN composite filler and modified carbon nanotube dispersion were mixed and extruded using a twin-screw extruder through dual-scale fillers and melt blending. The extruded material was injected into a preheated mold and a pressure of 5 MPa was applied. After maintaining the pressure for 1 hour, it was transferred to a vacuum oven and cured for 2 hours to obtain a phase change high thermal conductivity material with efficient thermal management capabilities.

8. The method for preparing a phase-change high thermal conductivity material with efficient thermal management capability according to claim 7, characterized in that: The ball-to-material ratio in the ball mill in step (1) is 10:1, and the powder obtained after ball milling in the ball mill is a micron-sized powder with D50 <10 μm.

9. The method for preparing a phase-change high thermal conductivity material with efficient thermal management capability according to claim 7, characterized in that: The specific operation steps of the twin-screw extruder in step (3) are as follows: A. Parameter Setting: Add the paraffin wax matrix into the melting section of the twin-screw extruder through the main feed port; start the heating system, raise the temperature to 80°C and maintain it at this temperature for 10 minutes to completely melt the paraffin wax into a liquid state; the melted paraffin wax matrix is conveyed to the mixing section by the screw, with the main screw speed at 200 rpm; B. Parameter setting: Increase the speed to 300-400 rpm, add the modified biochar / BN composite filler evenly into the mixing section at a rate of 5 g / min through the side feeder, and at the same time, start the high shear dispersion module and continue for 10 minutes; C. Parameter Settings: Increase the speed to 600-800 rpm and add the modified carbon nanotube dispersion as a suspension to the mixing section via the second side feeder. Start the kneading block of the twin-screw extruder to apply local high shear force to forcibly break up CNT agglomerates. Disperse for 15-20 minutes, pausing the screw every 3-5 minutes to clean any remaining CNT fibers in the kneading block area. D. Parameter setting: Close all feeding ports and keep the screw running at a low speed to ensure uniform material flow; open the vacuum degassing valve for 10-15 minutes to remove bubbles and volatiles from the melt; observe the melt state in the sight glass; if there are no bubbles escaping and the surface is smooth, it is qualified; Finally, the extruded material was injected into a preheated mold at 80°C, a pressure of 5 MPa was applied, and after maintaining the pressure for 1 hour, it was transferred to a vacuum oven and cured at 150°C for 2 hours.

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