A high thermal conductivity and high phase change enthalpy carbon nanocomposite phase change microcapsule and its preparation method

Abstract

The present invention belongs to the field related to phase change materials, and specifically relates to a high thermal conductivity and high phase change enthalpy carbon nanocomposite phase change microcapsule and its preparation method. The present invention uses flaky graphene oxide as a dispersant to form a water-in-oil Pickering emulsion with graphene oxide as the interface, and adds an initiator to the aqueous phase to polymerize the aniline monomer and the cross-linking monomer in the oil phase at the interface of the Pickering emulsion to form a network polymer layer to fix the capsule thermal conductive particle shell. The microcapsule shell is composed of thermal conductive polymer cross-linked polyaniline and thermal conductive particle graphene oxide. The diameter of the thermal conductive carbon nanoparticles first dispersed in the alkane phase change material is equivalent to the diameter of the capsule, and a thermal conductive path supporting the skeleton structure is formed in the confined space inside the microcapsule, thereby improving the thermal conductivity of the microcapsule. It has the characteristics of high thermal conductivity and high phase change heat storage capacity, and can be applied to renewable energy storage, new energy vehicle thermal management, industrial waste heat utilization, aerospace engineering and other fields.

Description

Technical Field

[0001] The present invention belongs to the field related to phase change materials, and specifically relates to a high thermal conductivity and high phase change enthalpy carbon nanocomposite phase change microcapsule and a preparation method thereof. The preparation and application of this composite phase change microcapsule involve the fields of thermal management, energy storage, etc. Background Art

[0002] Solid-liquid phase change materials (PCMs) can absorb or release large amounts of latent heat during a near-isothermal phase change, controlling the ambient temperature near the phase change temperature. This allows for temperature control or heat storage in highly fluctuating thermal environments, and they have broad application prospects, including renewable energy storage, thermal management of new energy vehicles, industrial waste heat utilization, and aerospace engineering. Alkane-based organic PCMs are the most widely used due to their high latent heat of fusion, a wide melting point range (-5°C to 66°C), non-toxicity, non-corrosiveness, chemical stability, minimal volume change upon melting, and good compatibility with most materials. While the latent heat of alkane PCMs is approximately 200–300 kJ / kg, their thermal conductivity is generally low, with a thermal conductivity coefficient of approximately 0.2 W / (m·K). This low thermal conductivity prevents rapid heat transfer and absorption, often failing to achieve the desired temperature control or heat storage effect. Furthermore, after melting into a liquid, there is the problem of liquid leakage. As a result, solid-liquid phase change materials have long had problems such as low thermal conductivity and liquid leakage, which greatly limit the practical application of phase change materials.

[0003] Microencapsulating phase-change materials is an effective method for preventing leakage, and using thermally conductive particles as the capsule wall can effectively enhance thermal conductivity. Existing techniques for preparing phase-change microcapsules suffer from at least one of the following problems: the thermally conductive particles in the shell and the polymer used to fix them are insufficiently thermally conductive, resulting in a limited improvement in thermal conductivity achieved solely through the thermally conductive particles in the shell. Furthermore, during the formation of the microcapsule wall, a large amount of polymer coating is required to stabilize the shell, significantly affecting the melting enthalpy of the composite phase-change microcapsules. Therefore, there is a need to develop composite phase-change microcapsule preparation methods that can improve the thermal conductivity of composite phase-change microcapsules while maintaining their phase-change enthalpy. Summary of the Invention

[0004] One of the purposes of the invention is to address the above-mentioned deficiencies and provide a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. On the one hand, for the shell layer of the composite phase-change microcapsules, graphene oxide is first used as an emulsifier to form a Pickering emulsion, and then interfacial polymerization is used to obtain a thermally conductive polymer cross-linked polyaniline to stabilize the carbon nanoparticles with stronger thermal conductivity to form the microcapsule shell layer, thereby improving the thermal conductivity of the shell layer; on the other hand, carbon particles of a size comparable to the diameter of the microcapsule are introduced into the microcapsule to further form a thermal conductive path within the microcapsule. Through the above two methods, carbon nanocomposite phase-change microcapsules with high thermal conductivity are obtained.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy, comprising the following steps:

[0006] S1, adding graphene oxide with a hydrophilic surface into pure water at a mass ratio of (1-10):1000 and ultrasonically dispersing the mixture to prepare a graphene oxide dispersion;

[0007] S2. Adding aniline, melamine, and thermally conductive carbon nanoparticles with a hydrophobic surface to an alkane phase change material, wherein the mixing mass ratio of aniline, melamine, thermally conductive carbon nanoparticles with a hydrophobic surface, and the alkane phase change material is (2-15):(0.1-1.50):(1-10):100, and ultrasonically dispersing the aniline, melamine, thermally conductive carbon nanoparticles with a hydrophobic surface to the alkane phase change material at a temperature of 5° C. or higher than the melting point of the alkane phase change material and lower than 90° C. to obtain an oil phase;

[0008] S3, mixing the graphene oxide dispersion and the oil phase to obtain a mixed solution, emulsifying the mixed solution at a temperature 5° C. or higher than the melting point of the alkane phase change material and lower than 90° C., adding a water-soluble initiator solution during the emulsification process, and maintaining the temperature for polymerization reaction for 5 to 20 hours after stopping the emulsification to generate an aqueous dispersion of phase change microcapsules;

[0009] S4. Filter the aqueous dispersion of the phase-change microcapsules, and dry the filtered material to obtain the phase-change microcapsules.

[0010] As a further improvement of the preparation method of carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy:

[0011] Preferably, the mixing mass ratio of the graphene oxide dispersion and the oil phase in step S3 is 100:(5-20).

[0012] Preferably, the surface-hydrophilic graphene oxide in step S1 has a sheet diameter of 0.1 to 10 μm and a thickness of 0.5 to 20 nm.

[0013] Preferably, the hydrophobic thermally conductive carbon nanoparticles in step S2 are graphene sheets or carbon nanotubes; the graphene sheets have a diameter of 5 to 20 μm and a thickness of 3 to 40 nm; the carbon nanotubes have an outer diameter of 10 to 100 nm and a length of 1 to 30 μm.

[0014] Preferably, the melting point of the alkane phase change material in step S2 is -30°C to 84°C, specifically one or a combination of two or more of normal alkanes with 10 to 40 carbon atoms and isoalkanes with 10 to 40 carbon atoms.

[0015] Preferably, the water-soluble initiator used in step S3 is one or a combination of two or more of ammonium persulfate, potassium bromate, potassium iodate, and potassium dichromate.

[0016] Preferably, the concentration of the water-soluble initiator solution in step S3 is 30% to 60%, and 0.5 to 1.5 parts by mass of the water-soluble initiator solution is added to 10 parts by mass of the mixed solution.

[0017] Preferably, in step S3, emulsification is performed for 5 to 10 minutes before adding the water-soluble initiator solution, and emulsification is continued for 0.5 to 1 minute after adding the water-soluble initiator solution, and then the emulsification is stopped.

[0018] Preferably, the power of ultrasonic dispersion in steps S1 and S2 is above 500 W and the time is 30 to 120 min; and in step S4, the filtered material is freeze-dried or air-dried at low temperature.

[0019] The second object of the present invention is to provide a high thermal conductivity and high phase change enthalpy carbon nanocomposite phase change microcapsule prepared by the preparation method of any one of the above-mentioned high thermal conductivity and high phase change enthalpy carbon nanocomposite phase change microcapsules.

[0020] The beneficial effects of the present invention compared to the prior art are:

[0021] 1) The present invention provides a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. First, graphene oxide is dispersed in pure water to produce a graphene oxide dispersion. Aniline, melamine (a crosslinking agent), and thermally conductive carbon nanoparticles are then added to an alkane phase-change material and ultrasonically dispersed at a temperature 5°C above the melting point of the phase-change material but not exceeding 90°C to obtain an oil phase. Next, for the shell of the composite phase-change microcapsules, the graphene oxide dispersion and the oil phase are mixed, using the graphene oxide as an emulsifier, to form an oil-in-water Pickering emulsion with the graphene oxide as the interface. The internal phase of the Pickering emulsion is an alkane phase-change material containing thermally conductive carbon nanoparticles, aniline monomer, and a crosslinking monomer. Then, an initiator is further added to the aqueous phase to polymerize the aniline monomer and cross-linking monomer in the oil phase at the Pickering emulsion interface to form a network layer of thermally conductive polymer cross-linked polyaniline to stabilize the carbon nanoparticles with stronger thermal conductivity to form a microcapsule shell, thereby improving the thermal conductivity of the shell.

[0022] 2) The microcapsule shell is composed of a thermally conductive polymer, cross-linked polyaniline, and thermally conductive graphene oxide particles. Due to the lamellar structure of graphene oxide and the interfacial polymerization of polyaniline, the amount of thermally conductive particles and polymer required to form the microcapsule wall is relatively small, which improves the microcapsule's thermal conductivity while maintaining the nanocomposite phase change microcapsule's high phase change enthalpy. The thermally conductive carbon nanoparticles, pre-dispersed into the alkane phase change material, have a diameter comparable to the capsule diameter, forming a thermally conductive pathway within the confined space within the microcapsule to support the skeleton structure. The addition of a small amount of thermally conductive carbon nanoparticles significantly improves the microcapsule's thermal conductivity. Through these two approaches, carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy are obtained.

[0023] Therefore, the composite phase change microcapsules of the present invention have the characteristics of high thermal conductivity and high phase change heat storage capacity, and can be applied to renewable energy storage, new energy vehicle thermal management, industrial waste heat utilization, aerospace engineering and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of a method for preparing a high thermal conductivity carbon nanocomposite phase change microcapsule of the present invention, wherein Figure 1 Figure a is a flow chart of the preparation method of nanocomposite phase-change microcapsules containing graphene in the inner phase of Example 1 and the scanning electron microscope morphology of the nanocomposite phase-change microcapsules. Figure 1 Figure b is a flow chart of the preparation method of nanocomposite phase-change microcapsules containing carbon nanotubes in the inner phase of Example 5 and the scanning electron microscope morphology of the nanocomposite phase-change microcapsules.

[0025] Figure 2 The thermal conductivity of the phase-change microcapsules prepared in the comparative example and the nanocomposite phase-change microcapsules prepared in Examples 1-4 after tableting is compared;

[0026] Figure 3 The comparison of the melting enthalpy of the phase change microcapsules prepared in the comparative example and the nanocomposite phase change microcapsules prepared in Examples 1-4 is shown;

[0027] Figure 4 The thermal conductivity of the phase-change microcapsules prepared in the comparative example and the nanocomposite phase-change microcapsules prepared in Examples 5-8 after tableting is compared;

[0028] Figure 5 This is a comparison of the melting enthalpy of the phase change microcapsules prepared in the comparative example and the nanocomposite phase change microcapsules prepared in Examples 5-8. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings, clearly and completely describing the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments made 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.

[0030] The present invention provides a method for preparing high thermal conductivity carbon nanocomposite phase change microcapsules through improvement. The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0031] Comparative Example

[0032] This comparative example provides a method for preparing phase-change microcapsules, which specifically includes the following steps:

[0033] S1, dispersing 0.4 g of graphene oxide with a diameter of 5 to 10 μm, a thickness of 4 to 20 nm, and a hydrophilic surface in 80 g of pure water, and ultrasonically dispersing at a power of 600 W for 120 min to obtain a graphene oxide dispersion;

[0034] S2, adding 0.8 g of aniline and 0.048 g of melamine to 8 g of eicosane, and ultrasonically dispersing the mixture at 50° C. and 600 W for 2 h to obtain an oil phase containing aniline monomer and crosslinking agent melamine;

[0035] S3, adding the oil phase to the graphene oxide dispersion, emulsifying at 50°C for 10 minutes, with an emulsifier speed of 12000 rpm, adding 8g of a 50% ammonium persulfate aqueous solution, continuing emulsification for 0.5 minutes, then stopping the emulsification, maintaining the polymerization reaction at 50°C for 14 hours, and generating an aqueous dispersion of phase change microcapsules;

[0036] S4. Filter the aqueous dispersion of the phase-change microcapsules and freeze-dry them to obtain phase-change microcapsules.

[0037] Example 1

[0038] This embodiment provides a method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy, which specifically includes the following steps:

[0039] S1, dispersing 0.4 g of graphene oxide with a diameter of 5 to 10 μm, a thickness of 4 to 20 nm, and a hydrophilic surface in 80 g of pure water, and ultrasonically dispersing at a power of 600 W for 120 min to obtain a graphene oxide dispersion;

[0040] S2, adding 0.8 g of aniline, 0.048 g of melamine, and 0.16 g of graphene with a thickness of 4 to 20 nm and a hydrophobic surface to 8 g of eicosane, and ultrasonically dispersing the mixture at 600 W for 120 min at 50° C. to obtain an oil phase containing aniline monomer, crosslinking agent melamine, and graphene;

[0041] S3, adding the oil phase to the graphene oxide dispersion, emulsifying at 50°C for 10 minutes, with an emulsifier speed of 12000 rpm, adding 8g of a 50% ammonium persulfate aqueous solution, continuing emulsification for 0.5 minutes, then stopping the emulsification, maintaining the polymerization reaction at 50°C for 14 hours, and generating an aqueous dispersion of phase change microcapsules;

[0042] S4. Filtering the aqueous dispersion of the phase-change microcapsules, freeze-drying the filtered material to obtain composite phase-change microcapsules.

[0043] Example 2

[0044] This embodiment provides a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. The specific steps are similar to those in Example 1, with the only difference being that 0.32 g of hydrophobic graphene with a thickness of 4 to 20 nm is added in step S2. Finally, composite phase-change microcapsules are produced.

[0045] Example 3

[0046] This embodiment provides a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. The specific steps are similar to those in Example 1, with the only difference being that 0.48 g of hydrophobic graphene with a thickness of 4 to 20 nm is added in step S2. Finally, composite phase-change microcapsules are produced.

[0047] Example 4

[0048] This embodiment provides a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. The specific steps are similar to those in Example 1, with the only difference being that 0.64 g of hydrophobic graphene with a thickness of 4 to 20 nm is added in step S2. Finally, composite phase-change microcapsules are produced.

[0049] Figure 2 The thermal conductivity of the phase-change microcapsules prepared in the comparative example and the nanocomposite phase-change microcapsules prepared in Examples 1-4 after tableting is compared; Figure 3 This is a comparison of the melting enthalpy of the phase change microcapsules prepared in the comparative example and the nanocomposite phase change microcapsules prepared in Examples 1-4. Figure 2 and Figure 3 It can be seen that the internal phase of the composite phase-change microcapsules prepared in the comparative example does not contain carbon nanoparticles, and the thermal conductivity measured after tableting is 0.99 W / (m·K); the internal phase of the composite phase-change microcapsules prepared in Examples 1-4 contains graphene particles of similar size to the microcapsules, and the thermal conductivity measured after tableting is 1.18-2.25 W / (m·K), which is significantly improved. The highest thermal conductivity is more than twice that of the comparative example. At the same time, the melting enthalpy of the composite phase-change microcapsules prepared in Examples 1-4 is between 228.0 and 243.6 J / g, maintaining a high level.

[0050] Example 5

[0051] This embodiment provides a method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy, which specifically includes the following steps:

[0052] S1, dispersing 0.40 g of graphene oxide with a diameter of 5 to 10 μm, a thickness of 4 to 20 nm, and a hydrophilic surface in 80 g of pure water, and ultrasonically dispersing at a power of 600 W for 120 min to obtain a graphene oxide dispersion;

[0053] S2, adding 0.8 g of aniline, 0.048 g of melamine, and 0.16 g of carbon nanotubes with an outer diameter of 50-100 nm, a length of 1-15 μm, and a hydrophobic surface to 8 g of eicosane, and ultrasonically dispersing the mixture at 600 W for 120 min at 50° C. to obtain an oil phase containing aniline monomer, crosslinking agent melamine, and carbon nanotubes;

[0054] S3, adding the oil phase to the graphene oxide dispersion, emulsifying at 50°C for 10 minutes, with an emulsifier speed of 12000 rpm, adding 8g of a 50% ammonium persulfate aqueous solution, continuing emulsification for 0.5 minutes, then stopping the emulsification, maintaining the polymerization reaction at 50°C for 14 hours, and generating an aqueous dispersion of phase change microcapsules;

[0055] S4. Filtering the aqueous dispersion of the phase-change microcapsules, freeze-drying the filtered material to obtain composite phase-change microcapsules.

[0056] Example 6

[0057] This example provides a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. The specific steps are similar to those in Example 5, with the only difference being that, in step S2, 0.32 g of carbon nanotubes with an outer diameter of 50-100 nm, a length of 1-15 μm, and a hydrophobic surface are added. Finally, composite phase-change microcapsules are produced.

[0058] Example 7

[0059] This example provides a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. The specific steps are similar to those in Example 5, with the only difference being that, in step S2, 0.48 g of carbon nanotubes with an outer diameter of 50-100 nm, a length of 1-15 μm, and a hydrophobic surface are added. Finally, composite phase-change microcapsules are produced.

[0060] Example 8

[0061] This example provides a method for preparing carbon nanocomposite phase-change microcapsules with high thermal conductivity and high phase-change enthalpy. The specific steps are similar to those in Example 5, with the only difference being that, in step S2, 0.64 g of carbon nanotubes with an outer diameter of 50-100 nm, a length of 1-15 μm, and a hydrophobic surface are added. Finally, composite phase-change microcapsules are produced.

[0062] Figure 4 The thermal conductivity of the phase-change microcapsules prepared in the comparative example and the nanocomposite phase-change microcapsules prepared in Examples 5-8 after tableting is compared; Figure 5 The comparison of the melting enthalpy of the phase change microcapsules prepared in the comparative example and the nanocomposite phase change microcapsules prepared in Examples 5-8 is shown in FIG. Figure 4 and Figure 5It can be seen that the thermal conductivity of the composite phase-change microcapsules prepared in Examples 5-8 after tableting is measured to be 1.15-1.60 W / (m·K), which is significantly improved compared to the thermal conductivity of 0.99 W / (m·K) of the composite phase-change microcapsules prepared in the comparative example. At the same time, the melting enthalpy of the composite phase-change microcapsules prepared in Examples 5-8 is 231.2-242.3 J / g, which is slightly lower than the melting enthalpy of 243.6 J / g of the composite phase-change microcapsules prepared in the comparative example, but still maintains a high level.

[0063] Example 9

[0064] This embodiment provides a method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy, which specifically includes the following steps:

[0065] S1, dispersing 10 g of graphene oxide with a diameter of 0.1 to 5 μm, a thickness of 0.5 to 20 nm, and a hydrophilic surface in 1000 g of pure water, and ultrasonically dispersing at a power of 600 W for 30 min to obtain a graphene oxide dispersion;

[0066] S2, adding 2 g of aniline, 0.1 g of a cross-linking agent melamine, and 10 g of hydrophobic graphene with a sheet diameter of 5 to 20 μm and a thickness of 3 to 40 nm to 100 g of pentadecane, and ultrasonically dispersing the mixture at a power of more than 500 W at 30° C. for 30 min to obtain an oil phase containing aniline monomer, cross-linking agent melamine, and graphene;

[0067] S3, adding the oil phase to the graphene oxide dispersion, emulsifying at 30°C for 10 minutes, with an emulsifier speed of 5000 rpm, adding 10g of a 30% potassium bromate solution, stopping the emulsification after 0.5 minutes, and maintaining the polymerization reaction at 30°C for 10 hours to generate an aqueous dispersion of phase change microcapsules;

[0068] S4. Filtering the aqueous dispersion of the phase-change microcapsules, and air-drying the microcapsules at low temperature to obtain phase-change microcapsules.

[0069] The thermal conductivity of the composite phase-change microcapsules prepared in Example 9 after tableting was measured at 1.88 W / (m·K), which is significantly improved compared to the thermal conductivity of 0.99 W / (m·K) of the composite phase-change microcapsules prepared in the comparative example. Furthermore, the melting enthalpy of the composite phase-change microcapsules prepared in Example 9 was 212 J / g, which was slightly lower than the melting enthalpy of 243.6 J / g of the composite phase-change microcapsules prepared in the comparative example, but maintained at a relatively high level.

[0070] Those skilled in the art will appreciate that the foregoing descriptions are merely specific embodiments of the present invention, and not exhaustive. It should be noted that numerous variations and modifications are possible for those skilled in the art, and all such variations and modifications that do not exceed the scope of the claims should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy, characterized in that: The following steps are involved: S1, adding graphene oxide with a hydrophilic surface into pure water at a mass ratio of (1-10):1000 and ultrasonically dispersing the mixture to prepare a graphene oxide dispersion; S2. Adding aniline, melamine, and thermally conductive carbon nanoparticles with a hydrophobic surface to an alkane phase change material, wherein the mixing mass ratio of aniline, melamine, thermally conductive carbon nanoparticles with a hydrophobic surface, and the alkane phase change material is (2-15):(0.1-1.50):(1-10):100, and ultrasonically dispersing the mixture at a temperature 5° C. higher than the melting point of the alkane phase change material and lower than 90° C. to obtain an oil phase; the thermally conductive carbon nanoparticles with a hydrophobic surface are graphene sheets or carbon nanotubes; S3, mixing the graphene oxide dispersion and the oil phase to obtain a mixed solution, emulsifying the mixed solution at a temperature 5° C. or higher than the melting point of the alkane phase change material and lower than 90° C., adding a water-soluble initiator solution during the emulsification process, and maintaining the temperature for polymerization reaction for 5 to 20 hours after stopping the emulsification to generate an aqueous dispersion of phase change microcapsules; S4. Filter the aqueous dispersion of the phase-change microcapsules, and dry the filtered material to obtain the phase-change microcapsules.

2. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1, characterized in that: In step S3, the mixing mass ratio of the graphene oxide dispersion and the oil phase is 100:(5-20).

3. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1, characterized in that: The surface-hydrophilic graphene oxide in step S1 has a sheet diameter of 0.1 to 10 μm and a thickness of 0.5 to 20 nm.

4. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1, 2 or 3, characterized in that: The graphene sheet in step S2 has a diameter of 5 to 20 μm and a thickness of 3 to 40 nm; the carbon nanotube has an outer diameter of 10 to 100 nm and a length of 1 to 30 μm.

5. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1, 2 or 3, characterized in that: The melting point of the alkane phase change material in step S2 is -30°C to 84°C, specifically one or a combination of two or more of normal alkanes with 10 to 40 carbon atoms and isoalkanes with 10 to 40 carbon atoms.

6. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1, characterized in that: The water-soluble initiator used in step S3 is one or a combination of two or more of ammonium persulfate, potassium bromate, potassium iodate, and potassium dichromate.

7. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1 or 6, characterized in that: The concentration of the water-soluble initiator solution in step S3 is 30% to 60%, and 0.5 to 1.5 parts by mass of the water-soluble initiator solution is added to 10 parts by mass of the mixed solution.

8. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1 or 2, characterized in that: In step S3, the emulsification is carried out for 5 to 10 minutes before the addition of the water-soluble initiator solution, and the emulsification is continued for 0.5 to 1 minute after the addition of the water-soluble initiator solution, and then the emulsification is stopped.

9. The method for preparing carbon nanocomposite phase change microcapsules with high thermal conductivity and high phase change enthalpy according to claim 1 or 2, characterized in that: In steps S1 and S2, the power of ultrasonic dispersion is above 500W and the time is 30 to 120 minutes; in step S4, the filtered material is freeze-dried.

10. A carbon nanocomposite phase change microcapsule with high thermal conductivity and high phase change enthalpy obtained by the method for preparing the carbon nanocomposite phase change microcapsule with high thermal conductivity and high phase change enthalpy according to any one of claims 1 to 9.

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