Polyurea hybrid silicon nitride phase change nanocapsule and preparation method thereof

Abstract

The application provides a polyurea hybrid phase change nanocapsule and a preparation method thereof. The polyurea hybrid phase change nanocapsule comprises a core material, a shell material and a heat-conducting filler, the shell material is wrapped around the periphery of the core material, and the heat-conducting filler is uniformly dispersed in the shell material; the core material is composed of paraffin, is used for absorbing or releasing latent heat in a phase change process, and realizes temperature regulation and heat energy storage; the shell material is composed of a polyurea material, is wrapped outside the paraffin, and a polyurea shell material is formed on the surface of the paraffin through an interfacial polymerization method; and the heat-conducting filler is uniformly dispersed in the polyurea shell material, is composed of nano silicon nitride modified by KH570, and is uniformly dispersed in the polyurea shell material. The application introduces nano silicon nitride modified by KH570 as the heat-conducting filler, and improves the heat conduction performance and thermal stability of the phase change material. The method can solve the problems of poor heat conduction performance, insufficient thermal stability and low mechanical strength of the existing phase change material in heat management applications.

Description

Technical Field

[0001] This invention relates to the field of nanocapsule technology, and in particular to a polyurea hybrid phase change nanocapsule and its preparation method. Background Technology

[0002] With the development of modern electronic devices towards high performance and high integration, the heat generated by these devices has increased significantly, making thermal management a crucial issue that urgently needs to be addressed. Effective thermal management materials and technologies play a key role in improving the operational stability of electronic devices and extending their service life.

[0003] PCM (Phase Change Material) is widely used in temperature control and thermal management due to its ability to absorb or release a large amount of latent heat during phase change. Paraffin wax, as a commonly used PCM material, has advantages such as adjustable melting point and high latent heat of phase change, thus showing promising prospects in energy storage and temperature control applications. However, paraffin wax itself suffers from low thermal conductivity and is prone to leakage during phase change, which limits its effectiveness in practical applications.

[0004] To address these issues with paraffin, encapsulating it in microcapsules can improve its thermal stability and prevent leakage. Microencapsulation technology forms a shell material on the surface of phase change materials, enabling them to maintain good stability during use. However, existing microencapsulation technologies still have some significant shortcomings:

[0005] Insufficient thermal conductivity: The shell material of microcapsules usually has poor thermal conductivity, which makes it difficult for the latent heat of phase change materials to be transferred quickly, thereby reducing the efficiency of thermal management.

[0006] Size effect limitation: Microcapsules are typically large in size, which not only limits their use in high-precision applications, but also results in poor bonding with the matrix material, reducing overall thermal conductivity.

[0007] Differences in mechanical properties: The shell material of microcapsules may decompose or deform under high temperature conditions, which increases the risk of leakage of phase change materials and thus affects their application under harsh working conditions.

[0008] The aforementioned issues indicate that while microencapsulation technology has improved the performance of phase change materials to some extent, its limitations in enhancing thermal conductivity and achieving high thermal stability remain, making it difficult to meet the stringent thermal management requirements of electronic devices. Therefore, developing a phase change material encapsulation technology with higher thermal stability and conductivity has become a current research hotspot and challenge.

[0009] Currently, one existing encapsulation scheme for phase change materials (PCMs) involves encapsulating the PCM (e.g., paraffin wax) within a polymer shell using physical methods (such as solution impregnation or suspension polymerization) to improve the thermal stability of the PCM and prevent leakage. For example, some existing PCM capsules use a single polymer shell (e.g., polyurethane, polyethylene). The disadvantages of this approach include the poor thermal conductivity of the microcapsule shell material, leading to inefficient transfer of latent heat during the phase change process and consequently affecting thermal management efficiency.

[0010] Another existing encapsulation method for phase change materials involves introducing high thermal conductivity fillers (such as silicon nitride, graphene, etc.) into a polymer shell to enhance thermal conductivity. Disadvantages of this method include: insufficient interfacial bonding: the high thermal conductivity fillers introduced into the polymer shell suffer from insufficient interfacial bonding, affecting the long-term stability and performance of the microcapsules. Preparation complexity: the technology of introducing high thermal conductivity fillers faces significant preparation complexity, especially in terms of uniform filler dispersion and particle size control. Summary of the Invention

[0011] The embodiments of the present invention provide a polyurea hybrid phase change nanocapsule and a method for preparing the same, so as to effectively improve the thermal conductivity, thermal stability and durability of the modified nanocapsule.

[0012] To achieve the above objectives, the present invention adopts the following technical solution.

[0013] According to one aspect of the present invention, a polyurea hybrid phase change nanocapsule is provided, comprising: a core material, a shell material, and a thermally conductive filler, wherein the shell material surrounds the periphery of the core material, and the thermally conductive filler is uniformly dispersed in the shell material;

[0014] The core material is made of paraffin and is used to absorb or release latent heat during the phase change process to achieve temperature regulation and thermal energy storage.

[0015] The shell is made of polyurea material and is wrapped around the outside of the paraffin wax. The polyurea shell is formed on the surface of the paraffin wax by interfacial polymerization.

[0016] The thermally conductive filler is uniformly dispersed in the polyurea shell and is composed of nano-silicon nitride modified with KH570. The nano-silicon nitride is uniformly dispersed in the polyurea shell and forms chemical bonds or physical adsorption with the polyurea shell.

[0017] Preferably, the nanocapsule has a spherical shape.

[0018] According to another aspect of the present invention, a method for preparing polyurea hybrid phase change nanocapsules is provided, comprising:

[0019] Preparation of KH570 modified nano-silicon nitride HK-Si3N4;

[0020] Paraffin wax is heated to a liquid state, and the liquid paraffin wax is mixed and stirred with HK-Si3N4 for a set time to obtain a mixture. The mixture is then mixed with isophorone diisocyanate (IPDI) at 60°C to form a polyurea shell. The polyurea shell coats the surface of the paraffin wax particles to form an oil phase solution.

[0021] Emulsifier OP-10 is dissolved in deionized water and stirred evenly in a 60°C constant temperature water bath to form an aqueous solution. The aqueous solution and the oil solution are homogenized and emulsified for a set time to form an oil-in-water emulsion.

[0022] After dissolving diethylenetriamine (DETA) in deionized water, the deionized water was added dropwise to the oil-in-water emulsion through a constant pressure funnel. The mixture was stirred for 6 hours and then kept at the temperature for another 12 hours to obtain nanocapsules.

[0023] The nanocapsules were washed with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven for a set time to obtain polyurea hybrid phase change nanocapsules (NEPCMs).

[0024] Preferably, the preparation of KH570 modified nano-silicon nitride HK-Si3N4 includes:

[0025] Six grams of nano-silicon nitride Si3N4 were placed in an appropriate amount of 30% hydrogen peroxide solution and stirred at 500 rpm for 6 hours to achieve hydroxylation treatment of silicon nitride.

[0026] The hydroxylated nano-silicon nitride was centrifuged twice at 12,000 rpm for 10 minutes each time, washed with deionized water, and then dried in a vacuum oven at 80°C for 12 hours to obtain centrifuged and washed silicon nitride H-Si3N4.

[0027] H-Si3N4 and KH-570 were mixed in a certain proportion in an ethanol-water solution with an alcohol-to-water ratio of 5:1. The mixture was ultrasonically treated for 20 minutes, and the pH was adjusted to 4.5-5.5 with glacial acetic acid. The mixture was stirred at 800 rpm for 3 hours at 80°C to complete the surface modification of H-Si3N4 by KH-570, thus obtaining KH570 modified nano-silicon nitride HK-Si3N4.

[0028] Preferably, the contact angle of the KH570 modified nano-silicon nitride material is 106.6°±0.3°. During the modification process, the methoxy groups in KH570 react with the hydroxyl groups on the surface of the nano-silicon nitride to form covalent bonds. The long-chain alkyl groups in KH570 are arranged on the surface of the nanoparticles to form a hydrophobic layer. KH570 forms an organic protective layer by forming organosilicon oxygen bonds on the surface of the nano-silicon nitride.

[0029] Preferably, the ratio includes 1:1, 1:1.5, or 1:2.

[0030] Preferably, the HK-Si3N4 is dispersed in the paraffin by uniformly stirring and mixing with paraffin. The IPDI acts as a crosslinking agent, and the diisocyanate groups of the IPDI undergo interfacial polymerization with diethylenetriamine (DETA) to generate polyurea chains, forming a polyurea shell.

[0031] The HK-Si3N4 participates in the formation of the polyurea shell, and the HK-Si3N4 forms a thermally conductive bridge between the paraffin and the polyurea shell.

[0032] As can be seen from the technical solutions provided by the embodiments of the present invention above, the method of the present invention can solve the problems of poor thermal conductivity, insufficient thermal stability, and low mechanical strength of existing phase change materials in thermal management applications. The present invention significantly improves the thermal conductivity and thermal stability of phase change materials by introducing nano-sized silicon nitride modified with KH570 as a thermally conductive filler.

[0033] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a structural diagram of a polyurea hybrid phase change nanocapsule provided in an embodiment of the present invention;

[0036] Figure 2 A schematic diagram illustrating a method for preparing a modified silicon nitride thermally conductive filler according to an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram illustrating the contact angle and dispersibility analysis of KH570-modified nano-silicon nitride, provided as an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram illustrating the dispersion and compatibility analysis of nano-silicon nitride in a paraffin core material, provided as an embodiment of the present invention.

[0039] Figure 5 A flowchart illustrating a method for preparing polyurea hybrid phase change nanocapsules according to an embodiment of the present invention;

[0040] Figure 6 A schematic diagram illustrating the infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis of modified silicon nitride (HK-Si3N4) provided in an embodiment of the present invention;

[0041] Figure 7 This invention provides a phase transition curve of U1-U3 and its coating rate and coating efficiency diagram.

[0042] Figure 8 The present invention provides a phase transition curve of U4-U9 and its coating rate and coating efficiency diagram.

[0043] Figure 9 The diagram illustrates the structural formulas of IPDI and DETA and the preparation principle of polyurea hybrid phase change nanocapsules (NEPCMs) provided in this embodiment of the invention.

[0044] Figure 10 A comparison chart of the thermal conductivity of U1-U9 and NEPCM provided for an embodiment of the present invention.

[0045] Figure 11 A schematic diagram illustrating the thermal cycling stability of a 6% KH570 modified silicon nitride hybrid phase change nanocapsule provided in this embodiment of the invention.

[0046] Figure 12 This is a SEM diagram of U1-U3 provided in an embodiment of the present invention;

[0047] Figure 13 This is a SEM schematic diagram of U4-U9 provided in an embodiment of the present invention;

[0048] Figure 14 This invention provides a TG and DTG curve diagram of U1-U9 and NEPCM. Detailed Implementation

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0050] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0051] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0052] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0053] This invention proposes a phase change material with polyurea as the capsule shell and introduces high thermal conductivity fillers such as silicon nitride, significantly improving the thermal conductivity and thermal stability of the phase change material. This improvement overcomes the technical bottlenecks in existing technologies, such as low thermal management efficiency, high risk of material leakage, and unstable material performance at high temperatures.

[0054] The structure of a polyurea hybrid phase change nanocapsule proposed in this invention is as follows: Figure 1 As shown, the nanocapsule includes a core material 1, a shell material 2, and a thermally conductive filler 3. The shell material surrounds the core material, and the thermally conductive filler is uniformly dispersed within the shell material. The overall shape of the nanocapsule is spherical.

[0055] The core material, which is the internal part of the nanocapsule, is made of paraffin and is responsible for absorbing or releasing a large amount of latent heat during the phase transition, thereby achieving temperature regulation and thermal energy storage.

[0056] The shell, made of polyurea, is a layer that encapsulates the paraffin wax. It provides mechanical protection and chemical stability, prevents paraffin wax leakage, and enhances the overall strength of the nanocapsules. The paraffin wax core is directly encapsulated by the polyurea shell, which is formed on the paraffin wax surface through interfacial polymerization, achieving a tight bond between the core and shell.

[0057] The thermally conductive filler, composed of KH570-modified nano-silicon nitride, is uniformly dispersed in the polyurea shell to improve the thermal conductivity of the nanocapsules and accelerate heat transfer. The modified nano-silicon nitride, through surface modification introducing functional groups, forms chemical bonds or undergoes physical adsorption with the polyurea shell, achieving uniform dispersion and enhancing the shell's thermal conductivity.

[0058] The core material (paraffin wax), as a phase change material, absorbs and releases heat during melting and solidification, serving for temperature regulation and thermal energy storage. The shell material (polyurea) provides physical protection, preventing paraffin leakage, enhancing the mechanical strength and chemical stability of the nanocapsules, and also acts as a carrier for the thermally conductive filler. The thermally conductive filler (modified nano-silicon nitride) improves the thermal conductivity of the nanocapsules, promoting rapid heat transfer and enhancing thermal management efficiency.

[0059] Polyurea shell material is a highly cross-linked polymer material formed by the addition reaction of isocyanate (IPDI) and diethylenetriamine (DETA) at the water-oil emulsion interface. The main function of the polyurea shell material is to encapsulate the paraffin core material, providing mechanical strength and thermal stability while preventing leakage of the phase change material. During preparation, paraffin wax is dispersed in the oil phase as the core material, while thermally conductive fillers (such as modified silicon nitride) are uniformly distributed within the shell layer, forming a composite shell layer together with the polyurea matrix. Through emulsification and interfacial polymerization, a complete polyurea hybrid phase change nanocapsule structure is formed, resulting in the hybrid polyurea shell material. This provides both protection and improved thermal conductivity. The core material (paraffin wax) is located within the hybrid polyurea shell material, serving as the core for the phase change material to store and release energy.

[0060] The present invention provides a method for preparing a modified silicon nitride thermally conductive filler, as follows: Figure 2 As shown, the processing steps include the following:

[0061] Step 1: Hydroxylation treatment of nano-silicon nitride.

[0062] Hydroxylation treatment: 6 grams of nano-silicon nitride (Si3N4) was placed in an appropriate amount of 30% hydrogen peroxide solution and stirred at 500 rpm for 6 hours to achieve hydroxylation treatment of silicon nitride.

[0063] Step 2: Centrifuge and wash.

[0064] The hydroxylated nano-silicon nitride was centrifuged twice at 12,000 rpm for 10 minutes each time, washed with deionized water, and then dried in a vacuum oven at 80°C for 12 hours to obtain centrifuged and washed silicon nitride (H-Si3N4).

[0065] Step 3: Modification of KH-570.

[0066] H-Si3N4 and KH-570 were mixed in a 5:1 ethanol-water solution at a certain ratio and ultrasonically treated for 20 minutes. The pH was adjusted to 4.5-5.5 with glacial acetic acid, and the mixture was stirred at 800 rpm for 3 hours at 80°C to complete the surface modification of H-Si3N4 by KH-570, yielding KH570-modified nano-silicon nitride (HK-Si3N4). In practical applications, the above ratio can be 1:1, 1:1.5, 1:2, etc.

[0067] A schematic diagram illustrating the contact angle and dispersibility analysis of KH570-modified nano-silicon nitride provided in this embodiment of the invention is shown below. Figure 3 As shown, to study the hydrophobic properties of modified nano-silicon nitride, this invention analyzed the surface wettability changes of nano-silicon nitride particles under different modification conditions by static contact angle measurement. Figure 3 As shown in (a), the untreated silicon nitride nanoparticles exhibit a contact angle of 27.5° ± 0.3°, indicating high hydrophilicity. The contact angle of the hydroxylated silicon nitride nanoparticles increased from... Figure 3 As shown in (b), the contact angle is 24.1° ± 0.5°. The further reduction in the contact angle indicates that the introduction of hydroxyl (–OH) groups on the material surface increases the hydrophilicity of the material. Figure 3 (c) The nano-silicon nitride material modified with silane coupling agent KH570 shows a significantly increased contact angle of 106.6°±0.3°, indicating a significant reduction in surface wettability and exhibiting obvious hydrophobicity. This is because silane coupling agent KH570 is an organosilicon compound containing long-chain alkyl groups, with reactive methoxy groups (–OCH3) and long-chain alkyl groups (–(CH2)) in its structure. 16 –CH3) group. During the modification process, the methoxy group in KH570 reacts with the hydroxyl group on the surface of nano-silicon nitride to form a strong covalent bond, while the long-chain alkyl group is arranged on the surface of the nanoparticles to form a hydrophobic layer. This hydrophobic layer effectively reduces the adsorption of water molecules on the surface of the nanoparticles, thereby significantly improving its hydrophobicity.

[0068] To further investigate the dispersibility and compatibility of KH570-modified nano-silicon nitride in paraffin core material, 0.3 g of Si3N4 and HK-Si3N4 were added to the same mass of paraffin, respectively. After ultrasonic dispersion for 1 hour, the materials were placed in an oven and photographed at different time points to observe their dispersion in the paraffin. The results are as follows: Figure 4 As shown, the original silicon nitride suspension exhibited significant stratification at 6 hours, while by 12 hours, it had completely settled, indicating a substantial difference in dispersibility compared to paraffin. In contrast, the HK-Si3N4 modified with KH570 maintained good dispersion throughout the entire dispersion experiment. Figure 4 It can be seen that its suspension still has significant dispersion stability after 18 hours.

[0069] The difference in dispersibility of KH570-modified nano-silicon nitride is mainly due to the formation of an organic protective layer by KH570 on the surface of the nano-silicon nitride through the formation of organosilicon-oxygen bonds. This organic protective layer lowers the surface free energy, significantly reducing the surface activity of the particles and thus decreasing the interaction forces and agglomeration between nano-silicon nitride particles. Before modification, the surface of nano-silicon nitride (Si3N4) typically has a high surface activation energy, which leads to easy agglomeration of particles and affects its dispersibility. Hydrogen peroxide treatment introduces hydroxyl groups (-OH), which increase the reactivity of the nanoparticle surface, making it easier for them to react chemically with the methoxy groups (-OCH3) in the KH570 molecules. The methoxy groups in the KH570 molecules hydrolyze to generate silanols (-Si-OH), which further react with the surface hydroxyl groups to form silicon-oxygen bonds (Si-O-Si). This process lowers the surface activation energy of the nano-silicon nitride, making its surface more stable. The results of the dispersibility experiment show that the dispersibility and stability of HK-Si3N4 in paraffin are significantly improved, making it suitable for inclusion in phase change nanocapsules for experiments.

[0070] The processing flow of a method for preparing polyurea hybrid phase change nanocapsules provided in this embodiment of the invention is as follows: Figure 5 As shown, the processing steps include the following:

[0071] Step 1, Oil Phase Preparation: Paraffin wax is heated to a liquid state and then uniformly mixed and stirred with HK-Si3N4 for 1 hour. Paraffin wax and IPDI have the chemical formula C2. 12 H 18 N2O2 (Isophorone diisocyanate) is mixed at 60°C to form an oil phase.

[0072] In the oil phase stage, the KH570-modified nano-silicon nitride (HK-Si3N4) was effectively dispersed in the paraffin wax through uniform stirring and mixing. As interfacial polymerization proceeded, the phase transformation properties of the paraffin wax were preserved, while the nano-silicon nitride provided additional thermal conductivity support. Nano-silicon nitride (Si3N4), H-Si3N4, and HK-Si3N4, as modified fillers, primarily function as thermally conductive fillers in the oil phase, and through their interaction with paraffin wax, they improve the thermal conductivity and mechanical strength of the final composite material.

[0073] The mixing of IPDI and paraffin wax: In the oil phase stage, paraffin wax is the base material, acting as a phase change material to store and release heat. IPDI is mixed with paraffin wax at this stage to form a stable polyurea shell. At this point, IPDI acts as a crosslinking agent; its diisocyanate groups undergo interfacial polymerization with ethylenediamine (deta) to generate polyurea chains, forming the polyurea shell. This polyurea shell then coats the surface of the paraffin wax particles, forming an oil phase solution. This polyurea shell enhances the stability of the paraffin wax, improves its thermal storage performance, and prevents leakage, further improving its stability.

[0074] Nano-silicon nitride (Si3N4) does not directly participate in the formation of the polyurea shell (it is not a direct participant in the IPDI reaction), but it is dispersed with paraffin as a filler in the oil phase. Its main function is to improve the thermal conductivity of the composite material in the oil phase stage. Due to the high thermal conductivity of silicon nitride, it can form a thermal bridge between the paraffin and the polyurea shell, enhancing the overall thermal conductivity efficiency.

[0075] The role of nano-silicon nitride in the oil-in-water stage is independent of the polyurea shell formed by IPDI, and the two work together through different mechanisms to affect the properties of the final composite material.

[0076] Step 2, Aqueous Phase Preparation and Emulsification: Dissolve emulsifier OP-10 in deionized water and stir evenly in a 60°C constant temperature water bath to form an aqueous phase solution. Then, homogenize and emulsify the aqueous and oil phase solutions for 10 minutes to form a stable oil-in-water emulsion. Step 2 can be performed simultaneously with Step 1.

[0077] Step 3, Polyurea Shell Formation: DETA is dissolved in deionized water and slowly added dropwise to the oil-in-water emulsion over 30 minutes through a constant pressure funnel. After stirring and reacting for 6 hours, the mixture is kept at the same temperature for 12 hours to obtain nanocapsules.

[0078] Step 4, Post-processing: The obtained nanocapsules were washed three times with deionized water and anhydrous ethanol, and dried in a vacuum drying oven for 24 hours to obtain the thermally enhanced polyurea hybrid phase change nanocapsules (NEPCMs) of the present invention.

[0079] To verify the experimental effectiveness of the method of the present invention, unmodified silicon nitride and hydroxylated silicon nitride were used to replace the thermally conductive filler in step 1 above, that is, to replace the KH570 modified nano-silicon nitride (HK-Si3N4). Then, phase change nanocapsules were fabricated according to the same method described above. The performance comparison of nanocapsule samples fabricated with three different thermally conductive fillers at 1% content is shown in Table 1 below:

[0080] Table 1

[0081] 1% Si3N4, 1% H-Si3N4, and 1% HK-Si3N4 correspond to U1, U2, and U3, respectively.

[0082]

[0083] 1.5%, 3%, 4.5%, 6%, 7.5%, and 9% HK-Si3N4, corresponding to U4, U5, U6, U7, U8, and U9 respectively, were used as thermally conductive fillers with different contents and added to the above-mentioned process for preparing phase change nanocapsules.

[0084] Table 2

[0085] 1.5%, 3%, 4.5%, 6%, 7.5%, and 9% HK-Si3N4 correspond to U4, U5, U6, U7, U8, and U9, respectively.

[0086]

[0087] To investigate the role mechanism of modified silicon nitride (HK-Si3N4) in phase change nanocapsules and its influence on chemical structure, Figure 6 A schematic diagram illustrating the infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis of modified silicon nitride (HK-Si3N4) provided in this embodiment of the invention, as shown below. Figure 6 As shown, the present invention performs infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis on modified silicon nitride (HK-Si3N4). Figure 6 (a) The FTIR (Fourier-Transform Infrared Spectroscopy) spectra of modified silicon nitride (HK-Si3N4) and modified silicon nitride hybrid paraffin@polyurea phase change nanocapsule composites (U4-U9) with different contents (1.5%, 3%, 4.5%, 6%, 7.5%, 9%) are shown. By analyzing the position and intensity of characteristic absorption peaks, the Si-N bond (located in the 800-1200 cm⁻¹ region) was found to be present. -1 CH bond (located at 2850-2950 cm) -1 C=O bond (located at 1700-1750 cm⁻¹) -1 ) and NH bonds (located at 3300-3500 cm⁻¹) -1 The characteristic absorption peaks remained essentially unchanged before and after modification, indicating that the modified silicon nitride hybrid nanocapsules did not significantly alter the chemical structure of the composite material. However, the change in the intensity of the characteristic absorption peaks may be related to the effect of increased modifier content on the microstructure of the composite material. Figure 6(b) The XRD patterns of (U4-U9) are shown, indicating that the positions of the main diffraction peaks are consistent (20°, 27°, 35°, and 45°), further confirming that KH570-modified silicon nitride did not alter the crystal structure of the composite material. Combined with SEM results, with increasing silicon nitride content, the particle size of the nanoparticles in the composite material decreased from approximately 100 nm to approximately 70 nm, which is manifested in the XRD patterns as broadening of diffraction peaks and reduction in intensity. These results indicate that although KH570-modified silicon nitride has little impact on the chemical and crystal structures of the composite material, it does improve the microstructure of the material by reducing particle size, thus providing experimental evidence for optimizing thermal conductivity.

[0088] To further investigate the effects of modified silicon nitride on the phase transition enthalpy and phase transition temperature of phase change nanocapsules, this invention used differential scanning calorimetry (DSC) to conduct a series of tests on hybrid phase change nanocapsules with different contents of modified silicon nitride. Figure 7 This invention provides a phase transition curve of U1-U3 and its coating rate and coating efficiency diagram.

[0089] Table 3: Phase transition characteristics curves of U1-U3

[0090]

[0091] The phase transition data obtained from the DSC results are shown in Table 4 above. The phase transition enthalpy of the unmodified phase transition nanocapsule U1 is 163.1 J / g, while the phase transition enthalpies of samples U2 and U3 modified with 1% H-Si3N4 and 1% HK-Si3N4, respectively, are 165.3 J / g and 167.0 J / g. The poor compatibility between the unmodified Si3N4 particles and the nanocapsule shell reduces the density of the shell and the encapsulation efficiency of the nanocapsules, resulting in a decrease in the phase transition enthalpy. However, the hydroxylated H-Si3N4 surface contains active -OH groups, which can interact better with the capsule wall, thereby improving the compatibility and reactivity between Si3N4 and the capsule wall, resulting in a slight increase in the phase transition enthalpy of U2. In contrast, HK-Si3N4 modified with the silane coupling agent KH570, due to the introduction of organosilanes, can form stronger chemical bonds on the Si3N4 surface and a denser bond with the capsule wall, thus significantly improving the phase transition enthalpy of U3 to 167.0 J / g. Data on encapsulation rate and efficiency also support this conclusion. The encapsulation rate and efficiency of U1 were 69.2% and 69.3%, respectively, while those of U2 and U3 reached 70.2% and 70.3%, and 70.9% and 71.0%, respectively. This improvement is mainly due to the better compatibility and bonding force between the modified Si3N4 particles and the nanocapsule shell, thereby enhancing the structural stability and encapsulation efficiency of the nanocapsules.

[0092] Table 4. Specific values ​​of enthalpy and phase transition temperature for phase change nanocapsules.

[0093]

[0094] Figure 8 The present invention provides a phase transition curve of U4-U9 and its coating rate and coating efficiency graphs. The above graphs and results are the phase transition characteristic data of samples U4-U9 with H-KSi3N4 modified nanocapsules of 1.5%, 3%, 4.5%, 6%, 7.5%, and 9%. With the increase of H-KSi3N4 content, the melting enthalpy (ΔHm) and solidification enthalpy (ΔHc) show a trend of first increasing and then decreasing. Specifically, the enthalpy of fusion of U4 is 171.3 J / g, and the enthalpy of solidification is 170.6 J / g. With increasing H-KSi3N4 content, the enthalpies of fusion of U5, U6, and U7 increase to 173.0 J / g, 173.9 J / g, and 178.8 J / g, respectively, with corresponding enthalpies of solidification of 172.6 J / g, 173.3 J / g, and 178.3 J / g. However, when the H-KSi3N4 content further increases to 7.5% (S8) and 9% (S9), the enthalpies of fusion and solidification decrease to 172.8 J / g and 157.7 J / g, and 172.6 J / g and 151.3 J / g, respectively. This trend can be explained by the compatibility of nano-silicon nitride with the capsule shell and the ratio of nano-silicon nitride content to phase change material. At lower content levels (1.5% to 6%), increasing the HKSi3N4 content, due to the modification effect of the silane coupling agent KH570, allows surface organosilicon groups to form chemical bonds with the capsule shell, enhancing the compatibility between nano-silicon nitride and the capsule shell, resulting in a denser bond and improved encapsulation efficiency and phase change performance of the nanocapsules. However, when the HKSi3N4 content further increases to 7.5% and 9%, the excessive addition of nano-silicon nitride occupies more capsule volume, leading to a decrease in the proportion of phase change material and consequently a drop in enthalpy. In conclusion, by rationally controlling the amount of HKSi3N4 added, the phase change performance and encapsulation efficiency of phase change nanocapsules can be significantly improved, with a 6% HKSi3N4 content achieving optimal performance.

[0095] The present invention provides a structural formula for IPDI and DETA and a schematic diagram of the preparation principle of polyurea hybrid phase change nanocapsules (NEPCMs), as shown in the embodiments below. Figure 9As shown in Tables 5-1, 5-2, 5-3, 5-4, and 5-5 below, the reaction conditions for preparing polyurea hybrid phase change nanocapsules (NEPCMs) with different mass ratios of PA, OP-10, IPDI, and DETA, i.e., different core-shell ratios, are also different. The reaction conditions for the NEPCMs mentioned above include the homogenization rate and the stirring rate.

[0096] Table 5-1 Reaction conditions for preparing phase change nanocapsules with different core-shell ratios

[0097]

[0098] Table 5-2 Reaction conditions for preparing phase change nanocapsules with different emulsifier dosages

[0099]

[0100] Table 5-3 Reaction conditions for preparing phase change nanocapsules at different homogenization emulsification rates

[0101]

[0102] Table 5-4 Reaction conditions for preparing phase change nanocapsules at different stirring speeds

[0103]

[0104] Table 5-5 Reaction conditions for orthogonal experiments to prepare phase change nanocapsules

[0105]

[0106]

[0107] Thermal performance analysis: Figure 10 A comparison chart of the thermal conductivity of U1-U9 and NEPCM provided for embodiments of the present invention, as shown below. Figure 10As shown in the figure, samples U1, U2, and U3 were modified with 1% Si3N4, 1% H-Si3N4, and 1% HK Si3N4, respectively, while samples U4 to U9 were modified with 1.5%, 3%, 4.5%, 6%, 7.5%, and 9% HK Si3N4, respectively. The experimental results show the following trends in thermal conductivity for each sample: Significant differences in thermal conductivity were observed for samples with 1% Si3N4, 1% H-Si3N4, and 1% HK Si3N4. Sample U1 had the lowest thermal conductivity at 0.290 W / (m·K), which is attributed to the poor compatibility between unmodified Si3N4 and the nanocapsule shell, resulting in high interfacial thermal resistance. Samples U2 and U3, with the addition of 1% H-Si3N4 and 1% H-KSi3N4, respectively, showed significantly improved thermal conductivity, reaching 0.308 W / (m·K) and 0.321 W / (m·K), respectively. This indicates that surface-modified Si3N4 can effectively improve interfacial compatibility with the nanocapsule shell, reduce interfacial thermal resistance, and increase thermal conductivity. For samples with different contents of HK Si3N4 (U4 to U9), the thermal conductivity showed a trend of first increasing and then decreasing. For samples U4 to U7 (1.5%, 3%, 4.5%, and 6% HK Si3N4), the thermal conductivity gradually increased with increasing HK Si3N4 content, reaching a maximum of 0.443 W / (m·K) in sample U7 (6% HK Si3N4). This phenomenon can be attributed to the following factors: firstly, the formation of a thermal conductivity network; the good dispersion of HK Si3N4 in the nanocapsules helps to form an effective thermal conductivity network, reducing interfacial thermal resistance; secondly, chemical bonds and polar interactions; the functional groups on the surface of HK Si3N4 can form tighter chemical bonds or polar interactions with the nanocapsule shell, thereby improving thermal conductivity.

[0108] However, when the H-KSi3N4 content continued to increase to 7.5% and 9%, the thermal conductivity began to decrease, with sample U9 exhibiting the lowest thermal conductivity at 0.359 W / (m·K). This may be due to the agglomeration effect, where excessive HK Si3N4 aggregates within the nanocapsules, resulting in uneven dispersion, increased interfacial thermal resistance, and reduced overall thermal conductivity. Furthermore, excessively high nano-silicon nitride content may affect the structural stability of the nanocapsules and the crystal structure of the phase change material, thus negatively impacting thermal conductivity. Appropriate addition of HK Si3N4 can significantly improve the thermal conductivity of phase change nanocapsules, but excessive addition leads to performance degradation. Optimizing the amount of HK Si3N4 added can achieve optimal thermal conductivity performance in phase change nanocapsules, which has significant application value for thermal management of electronic devices.

[0109] The experimental results of this invention show that modified silicon nitride (such as H-Si3N4 and HK Si3N4) has a significant impact on the thermal conductivity of phase change nanocapsules. The sample U1 with 1% unmodified Si3N4 added has the lowest thermal conductivity, approximately 0.290 W / (m·K), due to its poor compatibility with the nanocapsule shell and high interfacial thermal resistance. In contrast, the thermal conductivity of samples U2 and U3 with 1% H-Si3N4 and 1% HK Si3N4 added respectively increases to 0.308 W / (m·K) and 0.321 W / (m·K), indicating that surface-modified Si3N4 can improve interfacial compatibility and reduce interfacial thermal resistance. In samples with varying contents of HKSi3N4 (1.5% to 9%), the thermal conductivity initially increased and then decreased with increasing HKSi3N4 content. Sample U7 (6% HKSi3N4) achieved the highest thermal conductivity of 0.443 W / (m·K), mainly due to its good dispersibility and the formation of an effective thermal conduction network. However, when the HKSi3N4 content exceeded 6%, the thermal conductivity began to decrease, especially in samples with 7.5% and 9%, due to the agglomeration effect leading to uneven dispersion, increased interfacial thermal resistance, and consequently, reduced thermal conductivity. The experimental results indicate that appropriate addition of HKSi3N4 significantly improves thermal conductivity, while excessive addition decreases it. The optimal addition amount helps optimize the thermal conductivity of the nanocapsules, demonstrating potential value for thermal management applications in electronic devices.

[0110] Table 6

[0111]

[0112] A schematic diagram illustrating the thermal cycling stability analysis of a 6% KH570 modified silicon nitride hybrid phase change nanocapsule provided in this embodiment of the invention is shown below. Figure 11 As shown, 500 thermal cycling experiments were conducted on it, and the phase transition characteristics, crystal structure, and morphological changes before and after the cycles were compared and analyzed. Figure 11 As shown in (a), the DSC curves of the samples after the 1st and 500th thermal cycles basically overlapped, with similar intensity. The melting temperatures (Tm) were 41.94℃ and 42.26℃, respectively, and the latent heats (ΔHm) were 178.8 J / g and 176.8 J / g, respectively, decreasing by only 1.12%. Similarly, the phase transition temperature (Tc) and phase transition enthalpy (ΔHc) during the solidification process changed from 42.94℃ and 178.3 J / g to 42.76℃ and 176.5 J / g, respectively, with a very small change of only 1.01%. The phase transition enthalpy fluctuated only within ±2.0 J / g. These data indicate that silicon nitride hybridization modification significantly improves the thermal cycling stability of the nanocapsules, giving them superior thermal cycling resistance compared to the unmodified samples.

[0113] Figure 11(b) The XRD pattern shows that after 500 thermal cycles, the position and intensity of the crystal characteristic peaks did not change significantly, indicating that the crystal structure remained stable. SEM image ( Figure 11 (c) and (d) further demonstrate that the nanocapsules maintained their intact spherical structure after 500 thermal cycles, with no obvious shell damage. These results collectively prove that the 6% KH570 modified silicon nitride hybrid phase change nanocapsules can effectively maintain their thermal properties and structural stability during thermal cycling.

[0114] In summary, the 6% modified silicon nitride hybrid phase change nanocapsules exhibit excellent thermal cycling stability. The higher phase change enthalpy retention and more stable phase change temperature compared to the unmodified sample are attributed to the enhanced mechanical strength and thermal stability of the shell after KH570 modification with silicon nitride hybridization, effectively suppressing decomposition and aggregation during thermal cycling. This provides more reliable experimental evidence and theoretical support for their application in fields such as electronic chip heat dissipation and battery thermal management.

[0115] To further investigate the thermal cycling stability of 6% KH570-modified silicon nitride hybrid phase change nanocapsules, this invention conducted 500 thermal cycling experiments and analyzed the phase transition characteristics, crystal structure, and morphological changes before and after cycling. Experimental results showed that the DSC curves of the sample after the 1st and 500th thermal cycles almost overlapped, with very small changes in melting temperature and latent heat, decreasing by only 1.12% and 1.01%, respectively. These results indicate that silicon nitride modification significantly improves the thermal cycling stability of the nanocapsules. XRD patterns and SEM images showed that after 500 thermal cycles, the crystal structure and spherical structure of the sample remained stable, with no obvious damage or agglomeration observed. In summary, 6% KH570-modified silicon nitride hybrid phase change nanocapsules exhibit excellent thermal cycling stability, superior to the unmodified sample, providing reliable theoretical support for their applications in electronic device heat dissipation and battery thermal management.

[0116] Morphological composition analysis: Figure 12 A SEM diagram of U1-U3 provided in an embodiment of the present invention is shown below. Figure 12 As shown, samples U1, U2 and U3 were supplemented with 1% Si3N4, 1% H-Si3N4 and 1% HK Si3N4, respectively. Figure 12 a and Figure 12 b shows that the nanoparticles in sample U1 are relatively uniformly distributed, with particle diameters ranging from 272 nm to 327 nm and an average diameter of approximately 315 nm; the addition of 1% Si3N4 helps maintain the nanocapsule structure well and results in high particle uniformity. Figure 12c shows that the particle diameter in the U2 sample decreased to 123 nm to 159 nm, with an average diameter of about 151 nm. This may be due to H-Si3N4 improving the interfacial compatibility of the nanocapsules, reducing the particle size, and improving the dispersion uniformity. Figure 12 The results show that the particle diameter in the S3 sample further decreased to 104 nm to 112 nm, with an average diameter of approximately 108 nm. This indicates that the functional groups modified with HK Si3N4 form tight chemical bonds or polar interactions with the nanocapsule shell, enhancing the stability and dispersibility of the nanocapsules and thus optimizing the modified nanocapsule structure. In summary, with the gradual introduction and surface modification of Si3N4, H-Si3N4, and HK Si3N4, the nanocapsule particle size significantly decreased and the dispersion uniformity improved. This demonstrates that surface-modified Si3N4 can effectively improve the interfacial compatibility and structural stability of nanocapsules, enabling them to exhibit excellent performance in phase change energy storage materials.

[0117] In this invention, samples U1, U2, and U3 were modified with 1% Si3N4, 1% H-Si3N4, and 1% HK Si3N4, respectively. The results showed that the nanoparticles in sample U1 were uniformly distributed, with an average particle diameter of approximately 315 nm. After adding H-Si3N4, the particle size of sample U2 decreased to approximately 151 nm, indicating that H-Si3N4 improved the interfacial compatibility and dispersibility of the nanocapsules. Further addition of H-KSi3N4 further reduced the particle size of sample U3 to approximately 108 nm, indicating that the surface modification of HK Si3N4 enhanced the stability and dispersibility of the nanocapsules. Overall, surface-modified Si3N4 effectively improved the structural stability and dispersibility of the nanocapsules.

[0118] Figure 13 A SEM diagram of U4-U9 provided in an embodiment of the present invention is shown below. Figure 13 As shown, these are scanning electron microscope (SEM) images of samples (U4, U5, U6, U7, U8, U9) with added 1.5%, 3%, 4.5%, 6%, 7.5%, and 9% HK Si3N4, respectively. Sample U4 ( Figure 13 a) A relatively uniform nanoparticle distribution was observed, with a particle diameter of approximately 104 nm, indicating that the nanocapsule structure remained well-maintained and uniformly dispersed even with a low content of HK Si3N4. As the HK Si3N4 content increased to 3% ( Figure 13 b, Sample U5), with a particle diameter of approximately 105 nm, still maintains good uniformity, indicating that the appropriate amount of added HK Si3N4 can be uniformly distributed in the nanocapsule shell. When the HK Si3N4 content increases to 4.5% ( Figure 13When sample U6 (c), the particle diameter is around 98 nm, maintaining a good dispersion. When the HK Si3N4 content reaches 6% ( Figure 13 When the content of HKSi3N4 (sample U7) was increased to 7.5%, the particle size further decreased, with diameters ranging from 83 nm to 138 nm, and the dispersion uniformity was good. This may be because an appropriate amount of HKSi3N4 can form a denser network structure in the nanocapsule shell, improving the dispersion stability and structural compactness of the particles. However, as the content of HKSi3N4 continued to increase to 7.5%, the particle size decreased further. Figure 13 e, sample U8) and 9% ( Figure 13 When sample U9 was tested, the particle diameter ranged from 77.1 nm to 88 nm and from 67.5 nm to 82.4 nm, respectively. At this point, the particle size decreased, and the high content of HK Si3N4 may have caused local agglomeration. This is because the high content of HK Si3N4 forms agglomerates through mutual contact within the nanocapsule shell, thus affecting its uniform distribution.

[0119] In summary, as the content of HK Si3N4 increases, the size of the nanocapsule particles gradually decreases. An appropriate amount of H-KSi3N4 helps to form a tight network structure, which optimizes the dispersibility and structural compactness of the nanocapsules. However, an excessively high content may lead to local aggregation of the particles.

[0120] In this invention, 1.5%, 3%, 4.5%, 6%, 7.5%, and 9% H-KSi3N4 were added to samples U4 to U9, respectively, and the particle distribution and size changes were analyzed by SEM. The experiments showed that when the H-KSi3N4 content was 1.5% to 6% (samples U4 to U7), the particle distribution was uniform, the size gradually decreased, and the capsule structure was stable; when the content reached 7.5% and above (samples U8 and U9), local particle agglomeration occurred. The results indicate that an appropriate amount of H-KSi3N4 can optimize the dispersibility and structural stability of the capsules, while excessive addition may lead to agglomeration, thus affecting uniform distribution and performance.

[0121] Thermogravimetric analysis: Figure 14 This invention provides a TG and DTG curve diagram of U1-U9 and NEPCM. Figure 14 The TG and DTG curves for samples NEPCM, U1, U3, U5, U7, and U9 are shown. The thermal stability of the samples can be systematically evaluated through analysis of the thermogravimetric data. Figure 14As shown in the TG curves of (a), NEPCM (unmodified nanophase change capsules) exhibits a significant and rapid weight decrease between 200 and 300 °C, indicating a low thermal decomposition initiation temperature and relatively poor thermal stability. U1 (unmodified 1% silicon nitride hybrid phase change nanocapsules) shows some improvement in thermal stability compared to NEPCM, but the effect is not significant. However, with the increase in the amount of modified silicon nitride (U3, U5, U7, and U9) on the KH570 surface, the thermal decomposition initiation temperature of the material significantly increases, and the thermogravimetric process becomes more moderate, indicating that the modified silicon nitride has a particularly prominent effect on enhancing thermal stability.

[0122] from Figure 14 (b) The DTG curves further reveal that NEPCM and U1 exhibit high and concentrated weight loss peaks, indicating a violent decomposition process and weak structural stability. In contrast, the weight loss peaks of U3 to U9 gradually shift towards the high-temperature region, with U7 showing the lowest weight loss rate and a smoother decomposition curve. This suggests that U7 possesses the best thermal stability and balance during decomposition. This performance improvement can be attributed to the uniform dispersion and good interfacial interaction of KH570-modified silicon nitride in the material, significantly enhancing the structural integrity and heat transfer efficiency of the phase change nanocapsules. This demonstrates that the addition of modified silicon nitride significantly enhances the thermal stability of the phase change nanocapsules. Among them, U7 (6% modified silicon nitride hybrid phase change nanocapsules) shows the best performance in balancing thermal stability and thermal conductivity, demonstrating its potential value in thermal management materials, especially in heat dissipation applications for electronic devices.

[0123] like Figure 14 As shown, the TG and DTG curves of samples NEPCM and U1 to U9 demonstrate that modified silicon nitride significantly improves the thermal stability of phase change nanocapsules. NEPCM exhibits a low thermal decomposition onset temperature, a violent decomposition process, and poor structural stability. However, with increasing amounts of KH570 modified silicon nitride (U3 to U9), the thermal decomposition onset temperature gradually increases, and the weight loss curve becomes smoother. Among these, U7 (6% KH570 modified silicon nitride) exhibits the best thermal stability and balance, demonstrating the outstanding role of modified silicon nitride in improving the structural integrity and heat transfer efficiency of the material. This indicates that the addition of 6% modified silicon nitride provides the best balance between thermal stability and thermal conductivity, making it suitable for thermal management materials and heat dissipation applications in electronic devices.

[0124] In summary, the polyurea hybrid phase change nanocapsules (NEPCMs) prepared by the method of the present invention have the following beneficial effects:

[0125] Improving Thermal Conductivity and Thermal Management Efficiency: By introducing KH570 modifier to treat nano-silicon nitride, this invention effectively improves the thermal conductivity of phase change nanocapsules. Experimental results show that the modified nanocapsules exhibit a 54.9% improvement in thermal conductivity compared to ordinary phase change nanocapsule materials, significantly enhancing thermal management efficiency.

[0126] Enhanced thermal stability and durability: The improved bonding between the modified nano-silicon nitride and the polyurea shell enhances the stability of the nanocapsules under high-temperature conditions. After 500 thermal cycle tests, the phase transition temperature of the modified nanocapsules did not change by more than 3°C, demonstrating excellent thermal stability and durability.

[0127] Simplified preparation process and reduced production costs: The preparation method of this invention simplifies the traditional preparation process and avoids the use of expensive modifying reagents and solvents, thereby directly reducing production costs. At the same time, the efficient utilization of the KH570 modifier also reduces raw material consumption, further optimizing cost-effectiveness.

[0128] Enhanced environmental adaptability: The combination of modified nano-silicon nitride and polyurea improves the environmental adaptability of the nanocapsules, enabling them to maintain performance in a variety of environments, including harsh conditions such as humidity and temperature changes.

[0129] Improved safety: The chemical stability and heat resistance of polyurea materials make nanocapsules less prone to decomposition at high temperatures, reducing potential safety risks. They are particularly suitable for use in fields with high thermal safety requirements, such as electronic devices.

[0130] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0131] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0132] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0133] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing polyurea hybrid phase change nanocapsules, characterized in that, The polyurea hybrid phase change nanocapsule comprises: a core material, a shell material, and a thermally conductive filler, wherein the shell material surrounds the periphery of the core material, and the thermally conductive filler is uniformly dispersed in the shell material; The core material is made of paraffin and is used to absorb or release latent heat during the phase change process to achieve temperature regulation and thermal energy storage. The shell is made of polyurea material and is wrapped around the outside of the paraffin wax. The polyurea shell is formed on the surface of the paraffin wax by interfacial polymerization. The thermally conductive filler is uniformly dispersed in the polyurea shell and is composed of nano-silicon nitride modified with KH570. The nano-silicon nitride is uniformly dispersed in the polyurea shell and forms chemical bonds or physical adsorption with the polyurea shell. The preparation method of the polyurea hybrid phase change nanocapsules includes: Preparation of KH570 modified nano-silicon nitride HK-Si3N4; Paraffin wax is heated to a liquid state, and the liquid paraffin wax is mixed and stirred with HK-Si3N4 for a set time to obtain a mixture. The mixture is then mixed with isophorone diisocyanate (IPDI) at 60°C to form a polyurea shell. The polyurea shell coats the surface of the paraffin wax particles to form an oil phase solution. Emulsifier OP-10 is dissolved in deionized water and stirred evenly in a 60°C constant temperature water bath to form an aqueous solution. The aqueous solution and the oil solution are homogenized and emulsified for a set time to form an oil-in-water emulsion. After dissolving diethylenetriamine (DETA) in deionized water, the deionized water was added dropwise to the oil-in-water emulsion through a constant pressure funnel. After stirring and reacting for 6 hours, the mixture was kept at the temperature for another 12 hours to obtain nanocapsules. The nanocapsules were washed with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven for a set time to obtain polyurea hybrid phase change nanocapsules (NEPCMs). The preparation of KH570 modified nano-silicon nitride HK-Si3N4 includes: Six grams of nano-silicon nitride Si3N4 were placed in an appropriate amount of 30% hydrogen peroxide solution and stirred at 500 rpm for 6 hours to achieve hydroxylation treatment of silicon nitride. The hydroxylated nano-silicon nitride was centrifuged twice at 12,000 rpm for 10 minutes each time, washed with deionized water, and then dried in a vacuum oven at 80°C for 12 hours to obtain centrifuged and washed silicon nitride H-Si3N4. H-Si3N4 and KH-570 were mixed in a certain proportion in an ethanol-water solution with an alcohol-to-water ratio of 5:

1. The mixture was ultrasonically treated for 20 minutes, and the pH was adjusted to 4.5-5.5 with glacial acetic acid. The mixture was stirred at 800 rpm for 3 hours at 80°C to complete the surface modification of H-Si3N4 by KH-570, resulting in KH570 modified nano-silicon nitride HK-Si3N4. The contact angle of the KH570-modified nano-silicon nitride material is 106.6°±0.3°. During the modification process, the methoxy groups in KH570 react with the hydroxyl groups on the surface of the nano-silicon nitride to form covalent bonds. The long-chain alkyl groups in KH570 are arranged on the surface of the nanoparticles to form a hydrophobic layer. KH570 forms an organic protective layer by forming organosilicon oxygen bonds on the surface of the nano-silicon nitride. The HK-Si3N4 is dispersed in the paraffin by uniform stirring and mixing. The IPDI acts as a crosslinking agent. The diisocyanate groups of the IPDI will undergo an interfacial polymerization reaction with the diethylenetriamine DETA to generate polyurea chains and form a polyurea shell. The HK-Si3N4 participates in the formation of the polyurea shell, and the HK-Si3N4 forms a thermally conductive bridge between the paraffin and the polyurea shell.

2. The method for preparing polyurea hybrid phase change nanocapsules according to claim 1, characterized in that, The specified ratio includes 1:1, 1:1.5, or 1:

2.

3. The method for preparing polyurea hybrid phase change nanocapsules according to claim 1, characterized in that, The nanocapsule has an overall spherical shape.

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