Polyurea hybridized silicon nitride phase change nanocapsule and preparation method thereof

Abstract

The invention 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 surrounds and wraps 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 and used for absorbing or releasing latent heat in the phase change process, and temperature regulation and control and heat energy storage are achieved. The shell material is made of a polyurea material and wraps the paraffin, and the polyurea shell material is formed on the surface of the paraffin through an interfacial polymerization method; the heat-conducting filler is uniformly dispersed in the polyurea shell material and is composed of nano silicon nitride modified by KH570, and the nano silicon nitride is uniformly dispersed in the polyurea shell material. Nanoscale silicon nitride modified by KH570 is introduced as a heat-conducting filler, so that the heat conductivity and the heat stability of the phase-change material are improved. The method provided by the invention can solve the problems of poor thermal conductivity, insufficient thermal stability and low mechanical strength of the existing phase change material in thermal management application.

Description

Technical Field

[0001] The invention relates to the technical field of nanocapsules, and in particular to a polyurea hybrid phase-change nanocapsule and a preparation method thereof. Background Art

[0002] As modern electronic devices develop towards high performance and high integration, the heat generated by electronic devices has increased significantly, and thermal management of electronic devices has become an important issue that needs to be solved urgently. Effective thermal management materials and technologies play a key role in improving the working stability of electronic devices and extending their service life.

[0003] PCM (Phase Change Material) is widely used in the field of temperature control and thermal management because it can absorb or release a large amount of latent heat during the phase change process. Paraffin, as a commonly used phase change material, has the advantages of adjustable melting point and high latent heat of phase change, so it has good development prospects in energy storage and temperature control applications. However, paraffin itself has problems such as low thermal conductivity and easy leakage during the phase change process, which limits its effectiveness in practical applications.

[0004] In order to solve these problems of paraffin, encapsulating paraffin in microcapsules can improve its thermal stability and prevent leakage. Microcapsule technology forms a layer of shell material on the surface of phase change material, so that the phase change material can maintain good stability during use. However, the existing microcapsule technology still has the following significant deficiencies:

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

[0006] Size effect limitation: The size of microcapsules is usually large, which not only limits their use in high-precision applications, but also makes their bonding with the matrix material poor, reducing the overall thermal conductivity.

[0007] Differences in mechanical properties: The shell material of the microcapsule may decompose or deform in a high temperature environment, resulting in an increased risk of leakage of the phase change material, thus affecting its application under harsh working conditions.

[0008] The above problems show that although microencapsulation technology has improved the performance of phase change materials to a certain extent, its limitations in terms of thermal conductivity enhancement and high thermal stability still exist, making it difficult to meet the high requirements of thermal management of electronic devices. Therefore, developing a phase change material packaging technology with higher thermal stability and thermal conductivity has become a hot topic and difficulty in current research.

[0009] At present, one of the phase change material packaging solutions in the prior art includes: encapsulating the phase change material (such as paraffin) in a polymer shell by physical methods (such as solution impregnation, suspension polymerization, etc.) to improve the thermal stability of the phase change material and prevent leakage. For example, some existing phase change capsules use a single polymer shell (such as polyurethane, polyethylene, etc.). The disadvantages of this solution include: the thermal conductivity of the shell material of the microcapsule is poor, resulting in the inability to efficiently transfer the latent heat during the phase change process, thereby affecting the thermal management efficiency.

[0010] Another phase change material packaging solution in the prior art includes: introducing high thermal conductivity fillers (such as silicon nitride, graphene, etc.) into the polymer shell to enhance thermal conductivity. The disadvantages of this solution include: Insufficient interface bonding: The high thermal conductivity fillers introduced into the polymer shell have the problem of insufficient interface bonding, which affects the long-term stability and performance of the microcapsule. Preparation complexity: The technology of introducing high thermal conductivity fillers faces great preparation complexity, especially in terms of uniform dispersion of fillers and control of particle size. Summary of the invention

[0011] The embodiment of the present invention provides a polyurea hybrid phase change nanocapsule and a preparation method thereof, so as to effectively improve the thermal conductivity, thermal stability and durability of the modified nanocapsule.

[0012] In order to achieve the above object, the present invention adopts the following technical scheme.

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

[0014] The core material is made of paraffin wax and is used to absorb or release latent heat during phase change to achieve temperature control and thermal energy storage;

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

[0016] The thermal conductive filler is uniformly dispersed in the polyurea shell material and is composed of nano silicon nitride modified by KH570. The nano silicon nitride is uniformly dispersed in the polyurea shell material and forms a chemical bond or physical adsorption with the polyurea shell material.

[0017] Preferably, the overall shape of the nanocapsule is spherical.

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

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

[0020] The paraffin is heated to a liquid state, and the liquid paraffin is uniformly mixed with HK-Si3N4 and stirred for a set time to obtain a mixed solution; the mixed solution is mixed with isophorone diisocyanate IPDI at 60° C. to form a polyurea shell, and the polyurea shell is wrapped around the surface of the paraffin particles to form an oil phase solution;

[0021] Dissolve the emulsifier OP-10 in deionized water and stir evenly in a 60° C. constant temperature water bath to form an aqueous phase solution, and homogenize and emulsify the aqueous phase solution and the oil phase solution for a set time to form an oil-in-water emulsion;

[0022] After diethylenetriamine DETA was dissolved in deionized water, the deionized water was added dropwise to the oil-in-water emulsion through a constant pressure funnel, and the mixture was stirred for reaction for 6 hours and then kept warm for 12 hours to obtain nanocapsules.

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

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

[0025] 6 g 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 of silicon nitride;

[0026] The hydroxylated nano-silicon nitride was centrifuged twice at 12000 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 silicon nitride H-Si3N4 after centrifugal washing.

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

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

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

[0030] Preferably, the HK-Si3N4 is dispersed in the paraffin by uniformly stirring and mixing with the paraffin. The IPDI is used as a cross-linking agent. The diisocyanate group of IPDI reacts with diethylenetriamine DETA to generate polyurea chains and form a polyurea shell.

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

[0032] It can be seen from the technical solutions provided by the above embodiments of the present invention that 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-scale silicon nitride modified with KH570 as a thermal conductive filler.

[0033] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

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

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

[0037] Figure 3 A schematic diagram of contact angle and dispersibility analysis of nano silicon nitride modified by KH570 provided in an embodiment of the present invention.

[0038] Figure 4 A schematic diagram of the dispersibility and compatibility analysis of nano silicon nitride in a paraffin core material provided in an embodiment of the present invention.

[0039] Figure 5 A process flow chart of a method for preparing polyurea hybrid phase change nanocapsules provided in an embodiment of the present invention;

[0040] Figure 6 A schematic diagram of 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 A phase change curve of U1-U3 and a diagram of its coverage and coating efficiency are provided in an embodiment of the present invention.

[0042] Figure 8 A phase change curve of U4-U9 and a diagram of its coverage and coating efficiency are provided in an embodiment of the present invention.

[0043] Fig. 9 The structural formula of IPDI and DETA and the schematic diagram of the preparation principle of polyurea hybrid phase change nanocapsules (NEPCMs) provided in the embodiment of the present invention;

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

[0045] Fig.11 A schematic diagram of thermal cycling stability performance analysis of a 6% KH570 modified silicon nitride hybrid phase change nanocapsule provided in an embodiment of the present invention;

[0046] Fig.12 A SEM schematic diagram of U1-U3 provided in an embodiment of the present invention;

[0047] Fig.13 A SEM schematic diagram of U4-U9 provided in an embodiment of the present invention;

[0048] Fig.14 A TG and DTG curve diagram of U1-U9 and NEPCM provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The 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 throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0050] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the 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 refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0051] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0052] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0053] The embodiment of the present invention proposes a phase change material with polyurea as the capsule shell, and introduces high thermal conductivity fillers such as silicon nitride to significantly improve the thermal conductivity and thermal stability of the phase change material. Through this improvement, the technical bottlenecks of low thermal management efficiency, high risk of material leakage, and unstable performance of materials in high temperature environments in the prior art are solved.

[0054] The structure of a polyurea hybrid phase change nanocapsule proposed in an embodiment of the present invention is as follows: Figure 1 As shown, it comprises a core material 1, a shell material 2 and a thermal conductive filler 3, wherein the shell material surrounds and wraps around the core material, and the thermal conductive filler is evenly dispersed in the shell material. The overall shape of the nanocapsule is spherical.

[0055] The core material is the inner part of the nanocapsule, which is composed of paraffin wax and is responsible for absorbing or releasing a large amount of latent heat during the phase change process to achieve temperature control and thermal energy storage.

[0056] The shell material is a layer wrapped around the paraffin wax. It is made of polyurea material and provides mechanical protection and chemical stability, prevents paraffin wax leakage, and enhances the overall strength of the nanocapsule. The paraffin wax core material is directly wrapped by the polyurea shell material, and the polyurea shell material is formed on the paraffin wax surface by interfacial polymerization to achieve a close combination of the core material and the shell material.

[0057] The thermal conductive filler is evenly dispersed in the polyurea shell material, and is composed of nano silicon nitride modified by KH570, which is used to improve the thermal conductivity of the nanocapsule and accelerate the transfer of heat. The modified nano silicon nitride forms a chemical bond or physical adsorption with the polyurea shell material through the functional groups introduced by its surface modification, and is evenly dispersed in the polyurea shell material, thereby enhancing the thermal conductivity of the shell layer.

[0058] The core material (paraffin) is a phase change material. Paraffin absorbs and releases heat during melting and solidification, which is used for temperature regulation and thermal energy storage. The shell material (polyurea) provides physical protection to prevent paraffin leakage, enhance the mechanical strength and chemical stability of the nanocapsule, and also serves as a carrier for thermal conductive fillers. Thermal conductive fillers (modified nano silicon nitride) can improve the thermal conductivity of nanocapsules, promote rapid heat transfer, and improve 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 interface of water-oil emulsion. The main function of polyurea shell material is to coat the paraffin core material, provide mechanical strength and thermal stability, and prevent leakage of phase change materials. During the preparation process, paraffin is dispersed in the oil phase as the core material, and the thermal conductive filler (such as modified silicon nitride) is evenly distributed in 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 to form a hybrid polyurea shell material. It provides protection and improves thermal conductivity. The core material (paraffin) is located in the hybrid polyurea shell material, serving as the core of the phase change material for heat storage and energy release.

[0060] A method for preparing a modified silicon nitride thermally conductive filler provided in an embodiment of the present invention is as follows Figure 2 As shown, the processing includes the following:

[0061] Step 1: Hydroxylation 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 a rotation speed of 500 rpm for 6 hours to achieve hydroxylation of silicon nitride.

[0063] Step 2: Centrifugal washing.

[0064] The hydroxylated nano-silicon nitride was centrifuged at 12000 rpm for two times, each time for 10 minutes, and washed with deionized water, and then dried in a vacuum oven at 80° C. for 12 hours to obtain silicon nitride (H-Si3N4) after centrifugal washing.

[0065] Step 3: KH-570 modification.

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

[0067] A schematic diagram of contact angle and dispersibility analysis of nano silicon nitride modified by KH570 provided in an embodiment of the present invention is shown in FIG. Figure 3 As shown, in order to study the hydrophobic properties of the modified nano silicon nitride, the present invention analyzes the surface wettability changes of the nano silicon nitride particles under different modification conditions by static contact angle measurement. Figure 3 As shown in (a), the untreated nano-silicon nitride particles show a contact angle of 27.5°±0.3°, indicating that they have high hydrophilicity. Figure 3 In (b), it can be seen that it is 24.1°±0.5°. The further decrease 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) is the nano-silicon nitride material modified by silane coupling agent KH570. Its contact angle increases significantly to 106.6°±0.3°, indicating that its surface wettability decreases significantly and it exhibits obvious hydrophobicity. This is because silane coupling agent KH570 is an organic silicon compound containing long-chain alkyl groups, which contains reactive methoxy groups (–OCH3) and long-chain alkyl groups (–(CH2) 16 During the modification process, the methoxy groups in KH570 react with the hydroxyl groups on the surface of nano-silicon nitride to form a strong covalent bond, while the long-chain alkyl groups are arranged on the surface of the nanoparticles to form a hydrophobic layer, which effectively reduces the adsorption of water molecules on the surface of the nanoparticles, thereby significantly improving their hydrophobicity.

[0068] In order to further explore the dispersibility and compatibility of nano-silicon nitride modified by KH570 in paraffin core material, 0.3g Si3N4 and HK-Si3N4 were added to the same mass of paraffin, ultrasonically dispersed for 1h, placed in an oven and photographed at different time periods to observe their dispersion in paraffin. The results are shown in Figure 2. Figure 4 As shown in the figure, it can be seen that the original silicon nitride suspension has obvious stratification at 6 hours, and at 12 hours, the silicon nitride has completely settled, indicating that it has a large dispersibility difference with paraffin. In contrast, the HK-Si3N4 modified by KH570 maintains a good dispersion state throughout the dispersion experiment. Figure 4 It can be seen that the suspension still has significant dispersion stability at 18h.

[0069] The difference in the dispersibility of nano silicon nitride modified by KH570 is mainly due to the fact that KH570 forms an organic protective layer on the surface of nano silicon nitride by forming an organic silicon oxygen bond. This organic protective layer reduces the surface free energy, significantly reduces the surface activity of the particles, and thus reduces the interaction and agglomeration between nano silicon nitride. Because before modification, the surface of nano silicon nitride (Si3N4) usually has a high surface activation energy, which will cause the particles to easily agglomerate and affect its dispersibility. Hydroxyl groups (-OH) are introduced by hydrogen peroxide treatment. These hydroxyl groups increase the reactivity of the surface of nanoparticles, making it easier to react chemically with the methoxy groups (-OCH3) in the KH570 molecules. The methoxy groups in the KH570 molecules are hydrolyzed to form silanols (-Si-OH), and further react with the hydroxyl groups on the surface to form silicon oxygen bonds (Si-O-Si). This process reduces the surface activation energy of nano silicon nitride, making its surface more stable. By comparing the results of the dispersion experiment, it can be seen that the dispersibility and stability of HK-Si3N4 in paraffin have been significantly improved, making it suitable for addition to phase change nanocapsules for experiments.

[0070] The process flow of a method for preparing a polyurea hybrid phase change nanocapsule provided by an embodiment of the present invention is as follows: Figure 5 As shown, the processing steps include the following:

[0071] Step 1, oil phase preparation: heat paraffin to liquid state, and mix and stir evenly with HK-Si3N4 for 1 hour. Paraffin and IPDI, chemical formula is C 12 H 18 N2O2 (Isophorone diisocyanate) was mixed at 60°C to form an oil phase.

[0072] In the oil phase, the nano silicon nitride (HK-Si3N4) modified by KH570 is effectively dispersed in the paraffin by uniformly stirring and mixing with the paraffin. As the interfacial polymerization proceeds, the phase change characteristics of the paraffin are retained, while the nano silicon nitride provides additional thermal conductivity support. Nano silicon nitride (Si3N4), H-Si3N4, and HK-Si3N4 are modified fillers. Their role in the oil phase is mainly to be added as a thermally conductive filler, and through interaction with the paraffin, the thermal conductivity and mechanical strength of the final composite material are improved.

[0073] Mixing of IPDI and paraffin: In the oil phase stage, paraffin is the basic material in the oil phase. Its function is to store and release heat as a phase change material. IPDI is mixed with paraffin at this stage to form a stable polyurea shell. At this time, IPDI acts as a crosslinking agent, and the diisocyanate group of IPDI will undergo interfacial polymerization with ethylenediamine (deta) to generate polyurea chains and form a polyurea shell. The polyurea shell will wrap around the surface of the paraffin particles to form an oil phase solution. This polyurea shell can enhance the stability of paraffin, improve heat storage performance, prevent the leakage of paraffin, and improve the stability of paraffin.

[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 will be 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. Since silicon nitride has high thermal conductivity, it can form a thermal bridge between paraffin and the polyurea shell, enhancing the overall thermal conduction efficiency.

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

[0076] Step 2, water phase preparation and emulsification: dissolve the emulsifier OP-10 in deionized water and stir evenly in a 60°C constant temperature water bath to form a water phase solution. Then homogenize and emulsify the water phase solution and the oil phase solution for 10 minutes to form a stable water-in-oil emulsion. The above step 2 can be performed simultaneously with the above step 1.

[0077] Step 3, polyurea shell material formation: DETA was dissolved in deionized water, and slowly added dropwise to the water-in-oil emulsion through a constant pressure funnel within 30 minutes. After stirring for 6 hours, the mixture was kept warm for 12 hours to obtain nanocapsules.

[0078] Step 4, post-treatment: washing the obtained nanocapsules with deionized water and anhydrous ethanol for three times, and drying them in a vacuum drying oven for 24 hours to obtain the thermally conductive enhanced polyurea hybrid phase change nanocapsules (NEPCMs) of the present invention.

[0079] In order to verify the experimental effect of the method of the present invention, the present invention uses unmodified nitrided silicon nitride and hydroxylated silicon nitride to replace the thermal conductive filler in the above step 1, that is, to replace the nano silicon nitride (HK-Si3N4) modified by KH570, and then, the phase change nanocapsules are prepared according to the above method. The performance comparison of the nanocapsule samples made of three different 1% thermal conductive fillers is shown in the following Table 1:

[0080] Table 1

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

[0082]

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

[0084] Table 2

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

[0086]

[0087] In order to explore the mechanism of action of modified silicon nitride (HK-Si3N4) in phase change nanocapsules and its influence on the chemical structure, Figure 6 A schematic diagram of infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis of modified silicon nitride (HK-Si3N4) provided in an embodiment of the present invention is shown in FIG. Figure 6 As shown, the present invention conducted infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis on the modified silicon nitride (HK-Si3N4). Figure 6 (a) shows 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%). By analyzing the position and intensity of the characteristic absorption peaks, it was found that the Si-N bond (located at 800-1200cm -1 ), CH bond (located at 2850-2950cm -1 ), C=O bond (located at 1700-1750cm -1 ) and NH bonds (located at 3300-3500cm -1 ) remained basically unchanged before and after modification, indicating that the modified silicon nitride hybrid nanocapsules did not significantly change the chemical structure of the composite material. However, the change in the intensity of the characteristic absorption peak may be related to the effect of the increase in the modifier content on the microstructure of the composite material. Figure 6(b) shows the XRD patterns of (U4-U9), which show that the positions of the main diffraction peaks are consistent (20°, 27°, 35° and 45°), further confirming that KH570-modified silicon nitride does not change the crystal structure of the composite. Combined with the SEM results, as the content of modified silicon nitride increases, the particle size of the nanoparticles in the composite decreases from about 100nm to about 70nm, which is manifested in the XRD spectrum as the broadening and intensity reduction of the diffraction peaks. These results show that although KH570-modified silicon nitride has little effect on the chemical structure and crystal structure of the composite, it does improve the microstructure of the material by reducing the particle size, thus providing an experimental basis for optimizing thermal conductivity.

[0088] In order to further explore the effect of modified silicon nitride on the phase change enthalpy and phase change temperature of phase change nanocapsules, the present invention uses differential scanning calorimetry (DSC) to conduct a series of tests on hybrid phase change nanocapsules with different contents of modified silicon nitride. Figure 7 A phase change curve of U1-U3 and a diagram of its coverage and coating efficiency are provided in an embodiment of the present invention.

[0089] Table 3: Phase change characteristic curves of U1-U3

[0090]

[0091] The phase change data obtained from the DSC results are shown in Table 4 above. The phase change enthalpy of the unmodified phase change nanocapsule U1 is 163.1 J / g, while the phase change enthalpy of samples U2 and U3 modified with 1% H-Si3N4 and 1% HK-Si3N4 are 165.3 J / g and 167.0 J / g, respectively. The poor compatibility between the unmodified Si3N4 particles and the nanocapsule shell reduces the compactness of the shell layer and the encapsulation efficiency of the nanocapsule, resulting in a decrease in the phase change 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, making the phase change enthalpy of U2 slightly increased. In contrast, HK-Si3N4 modified with silane coupling agent KH570 has introduced organic silane groups, which can form stronger chemical bonds on the surface of Si3N4 and form a denser bond with the capsule wall, thereby significantly improving the phase change enthalpy of U3 to 167.0 J / g. The data of coating rate and coating efficiency also support this conclusion. The coating rate and coating efficiency of U1 are 69.2% and 69.3%, respectively, while the coating rates and coating efficiencies of U2 and U3 are 70.2%, 70.3%, 70.9%, and 71.0%, respectively. This improvement is also mainly due to the better compatibility and bonding 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 phase change characteristic enthalpy and phase change temperature of phase change nanocapsules

[0093]

[0094] Figure 8 A phase change curve of U4-U9 and its coating rate and coating efficiency diagram provided in an embodiment of the present invention. The above chart results are the phase change characteristic data of samples U4-U9, which are 1.5%, 3%, 4.5%, 6%, 7.5% and 9% H-KSi3N4 modified nanocapsules respectively. With the increase of HK Si3N4 content, the melting enthalpy value (ΔHm) and the solidification enthalpy value (ΔHc) show a trend of increasing first and then decreasing. Specifically, the melting enthalpy of U4 is 171.3 J / g and the solidification enthalpy is 170.6 J / g. As the H-KSi3N4 content increases, the melting enthalpy of U5, U6, and U7 increases to 173.0 J / g, 173.9 J / g, and 178.8 J / g, respectively, and the corresponding solidification enthalpies are 172.6 J / g, 173.3 J / g, and 178.3 J / g, respectively. However, when the HK Si3N4 content further increases to 7.5% (S8) and 9% (S9), the melting enthalpy and solidification enthalpy decrease to 172.8 J / g, 157.7 J / g and 172.6 J / g, 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. When the content is low (1.5% to 6%), the HK Si3N4 content increases. Due to the modification effect of the silane coupling agent KH570, the surface organic silane groups can form chemical bonds with the capsule shell, which enhances the compatibility between nano-silicon nitride and the capsule shell, forming a denser bond, and improving the encapsulation efficiency and phase change performance of the nanocapsule. However, when the HK Si3N4 content is further increased to 7.5% and 9%, the excessive addition of nano-silicon nitride will occupy more capsule volume, resulting in a decrease in the proportion of phase change material, which in turn leads to a decrease in enthalpy. In summary, the phase change performance and encapsulation efficiency of phase change nanocapsules can be significantly improved by reasonably controlling the addition amount of HK Si3N4, among which the 6% HK Si3N4 content enables the nanocapsules to achieve the best performance.

[0095] The structural formula of IPDI and DETA provided in the embodiment of the present invention and the schematic diagram of the preparation principle of polyurea hybrid phase change nanocapsules (NEPCMs) are as follows: Fig. 9In practical applications, as shown in Tables 5-1, 5-2, 5-3, 5-4 and 5-5 below, different mass ratios of PA, OP-10, IPDI and DETA, i.e. different core-shell ratios are selected to prepare polyurea hybrid phase change nanocapsules (NEPCMs) under different reaction conditions. The reaction conditions of the above NEPCMs include homogenization rate and 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 reaction stirring speeds

[0103]

[0104] Table 5-5 Reaction conditions for preparing phase change nanocapsules by orthogonal experiment

[0105]

[0106]

[0107] Thermal performance analysis: Fig.10 A comparison chart of thermal conductivity between U1-U9 and NEPCM provided in an embodiment of the present invention, such as Fig.10As shown. Samples U1, U2, and U3 were added with 1% Si3N4, 1% H-Si3N4, and 1% HK Si3N4, respectively, while samples U4 to U9 were added with 1.5%, 3%, 4.5%, 6%, 7.5%, and 9% HK Si3N4, respectively. The experimental results show that the thermal conductivity variation trends of each sample are as follows: For samples with 1% Si3N4, 1% H-Si3N4, and 1% HK Si3N4 added, the thermal conductivity showed significant differences. The thermal conductivity of the U1 sample was the lowest, at 0.290W / (m·K), because the compatibility between the unmodified Si3N4 and the nanocapsule shell was poor, resulting in a high interfacial thermal resistance. The thermal conductivity of the U2 and U3 samples was significantly improved by adding 1% H-Si3N4 and 1% H-KSi3N4, respectively, reaching 0.308W / (m·K) and 0.321W / (m·K), respectively. This shows that the surface-modified Si3N4 can effectively improve the interfacial compatibility with the nanocapsule shell, reduce the interfacial thermal resistance, and improve the thermal conductivity. For samples (U4 to U9) with different contents of HK Si3N4 added, the thermal conductivity shows a trend of first increasing and then decreasing. The thermal conductivity of samples U4 to U7 (1.5%, 3%, 4.5%, 6% HK Si3N4) gradually increases with the increase of HK Si3N4 content, and the highest value appears in sample U7 (6% HK Si3N4), reaching 0.443W / (m·K). This phenomenon can be attributed to the following points: First, the formation of a heat conduction network. The good dispersion of HK Si3N4 in nanocapsules helps to form an effective heat conduction network and reduce the interfacial thermal resistance; second, 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, and the thermal conductivity of sample U9 was the lowest, at 0.359W / (m·K). This may be due to the agglomeration effect, which causes the excess HK Si3N4 to agglomerate in the nanocapsules and disperse unevenly, thereby increasing the interfacial thermal resistance and reducing the overall thermal conductivity. In addition, excessive nano-silicon nitride content may affect the structural stability of the nanocapsules and the crystal structure of the phase change material, which is not conducive to thermal conductivity. The appropriate addition of HK Si3N4 can significantly improve the thermal conductivity of the phase change nanocapsules, but excessive addition will lead to a decrease in performance. By optimizing the addition amount of HK Si3N4, the best thermal conductivity performance can be achieved in the phase change nanocapsules, which has important application value for thermal management of electronic devices.

[0109] The experimental results of the present invention show that modified silicon nitride (such as H-Si3N4, HK Si3N4) has a significant effect on the thermal conductivity of phase change nanocapsules. The thermal conductivity of sample U1 with 1% unmodified Si3N4 added is the lowest, about 0.290W / (m·K), because of its poor compatibility with the nanocapsule shell and high interface thermal resistance; while the thermal conductivities of samples U2 and U3 with 1% H-Si3N4 and 1% HK Si3N4 are increased to 0.308W / (m·K) and 0.321W / (m·K), respectively, indicating that surface-modified Si3N4 can improve interface compatibility and reduce interface thermal resistance. In samples with different contents of HK Si3N4 (1.5% to 9%), the thermal conductivity first increases and then decreases with the increase of the content of H-KSi3N4. Sample U7 (6% HK Si3N4) reaches the highest thermal conductivity of 0.443W / (m·K), mainly due to good dispersibility and effective thermal conduction network formation. However, when the content of HK Si3N4 exceeds 6%, the thermal conductivity begins to decrease, especially for samples of 7.5% and 9%, due to the agglomeration effect, which leads to uneven dispersion and increases the interfacial thermal resistance, thus affecting the thermal conductivity. The experimental results show that the addition of an appropriate amount of HK Si3N4 can significantly improve the thermal conductivity, but excessive addition will reduce the thermal conductivity. The optimal addition amount helps to optimize the thermal conductivity of the nanocapsules and has potential application value in thermal management of electronic devices.

[0110] Table 6

[0111]

[0112] A schematic diagram of thermal cycling stability performance analysis of a 6% KH570 modified silicon nitride hybrid phase change nanocapsule provided in an embodiment of the present invention is shown in FIG. Fig.11 As shown in Figure 2, 500 hot and cold cycle experiments were conducted on it, and the phase change characteristics, crystal structure and morphology changes before and after the cycle were compared and analyzed). Fig.11 As shown in (a), the DSC curves of the samples after the first and 500th thermal cycles are basically overlapped and have similar strengths. The melting temperatures (Tm) are 41.94°C and 42.26°C, respectively, and the latent heat (ΔHm) is 178.8 J / g and 176.8 J / g, respectively, which only decreased by 1.12%. Similarly, the phase change temperature (Tc) and phase change enthalpy (ΔHc) of the solidification process changed from 42.94°C and 178.3 J / g to 42.76°C and 176.5 J / g, respectively, with a very small change of only 1.01%, and the phase change enthalpy fluctuated only within ±2.0 J / g. These data indicate that the hybrid modification of silicon nitride significantly improves the thermal cycling stability of the nanocapsules, and has better thermal cycling resistance than the unmodified samples.

[0113] Fig.11The XRD pattern in (b) shows that the position and intensity of the crystal characteristic peaks of the sample did not change significantly after 500 thermal cycles, indicating that its crystal structure remained stable. SEM image ( Fig.11 (c) and (d) further show that the nanocapsules still maintain a complete spherical structure after 500 thermal cycles, and no obvious shell damage is observed. The above results together prove that 6% KH570 modified silicon nitride hybrid phase change nanocapsules can well maintain their thermal properties and structural stability during thermal cycling.

[0114] In summary, the 6% modified silicon nitride hybrid phase change nanocapsules showed excellent thermal cycling stability. The higher phase change enthalpy retention rate and more stable phase change temperature compared to the unmodified samples were attributed to the fact that the silicon nitride hybrid after KH570 modification enhanced the mechanical strength and thermal stability of the shell, effectively inhibiting the cracking and agglomeration during the thermal cycle. This provides a more reliable experimental basis and theoretical support for its application in the fields of electronic chip heat dissipation and battery thermal management.

[0115] In order to further study the thermal cycling stability of 6% KH570 modified silicon nitride hybrid phase change nanocapsules, the present invention conducted 500 hot and cold cycle experiments and analyzed the phase change characteristics, crystal structure and morphological changes before and after the cycle. The experimental results show that the DSC curves of the samples after the first and 500th thermal cycles are almost identical, and the melting temperature and latent heat change very little, only decreasing by 1.12% and 1.01% respectively. These results show that modified silicon nitride significantly improves the thermal cycling stability of nanocapsules. XRD spectra and SEM images show that after 500 thermal cycles, the crystal structure and spherical structure of the sample remain stable, with no obvious damage or agglomeration. In summary, 6% KH570 modified silicon nitride hybrid phase change nanocapsules exhibit excellent thermal cycling stability, which is better than unmodified samples, which provides reliable theoretical support for its application in electronic device heat dissipation and battery thermal management.

[0116] Morphological composition analysis: Fig.12 A SEM schematic diagram of U1-U3 provided in an embodiment of the present invention is shown in FIG. Fig.12 As shown, U1, U2 and U3 samples were added with 1% Si3N4, 1% H-Si3N4 and 1% HK Si3N4, respectively. Fig.12 a and Fig.12 b shows that the nanoparticles in the U1 sample are distributed more evenly, with particle diameters ranging from 272nm to 327nm and an average diameter of about 315nm; the addition of 1% Si3N4 keeps the nanocapsule structure well and the particle uniformity is high. Fig.12c shows that the particle diameter in the U2 sample decreases to 123 nm to 159 nm, with an average diameter of about 151 nm, which may be due to the fact that H-Si3N4 improves the interfacial compatibility of the nanocapsules, reduces the particle size and improves the dispersion uniformity. Fig.12 d shows that the particle diameter in the S3 sample is further reduced to 104nm to 112nm, with an average diameter of about 108nm, which indicates that the functional groups modified on the surface of HK Si3N4 form tight chemical bonds or polar interactions with the shell of the nanocapsule, which enhances the stability and dispersibility of the nanocapsules, thereby optimizing the structure of the modified nanocapsules. In summary, with the gradual introduction and surface modification of Si3N4, H-Si3N4 and HK Si3N4, the particle size of the nanocapsules is significantly reduced and the dispersion uniformity is improved, indicating that the surface-modified Si3N4 can effectively improve the interface compatibility and structural stability of the nanocapsules, enabling them to exhibit excellent performance in phase change energy storage materials.

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

[0118] Fig.13 A SEM schematic diagram of U4-U9 provided in an embodiment of the present invention is shown in FIG. Fig.13 As shown, these are the scanning electron microscope (SEM) morphology images of samples (U4, U5, U6, U7, U8, U9) with 1.5%, 3%, 4.5%, 6%, 7.5% and 9% HK Si3N4 added respectively. Sample U4 ( Fig.13 a) shows a relatively uniform distribution of nanoparticles, with a particle diameter of about 104 nm, indicating that when HK Si3N4 is added at a lower content, the nanocapsule structure is well maintained and evenly dispersed. As the HK Si3N4 content increases to 3% ( Fig.13 b, sample U5), the particle diameter is about 105nm, and the particles still maintain good uniformity, indicating that the HK Si3N4 added in an appropriate amount can be evenly distributed in the nanocapsule shell. When the HK Si3N4 content increases to 4.5% ( Fig.13c, sample U6), the particle diameter is about 98nm, maintaining a good dispersion state. When the HK Si3N4 content reaches 6% ( Fig.13 d, sample U7), the particle size further decreased, with diameters ranging from 83nm to 138nm, and the dispersion uniformity was good. This may be because the appropriate amount of HK Si3N4 can form a more compact network structure in the nanocapsule shell, improving the dispersion stability and structural density of the particles. However, as the HK Si3N4 content continued to increase to 7.5% ( Fig.13 e, sample U8) and 9% ( Fig.13 f, sample U9), the particle diameter ranges from 77.1nm to 88nm and from 67.5nm to 82.4nm respectively. At this time, the particle size is reduced, and the higher content of HK Si3N4 may cause local agglomeration, which is due to the high content of HK Si3N4 contacting each other in the nanocapsule shell to form agglomerates, thus affecting its uniform distribution.

[0119] In summary, with the increase of HK Si3N4 content, the size of nanocapsule particles gradually decreases. The appropriate amount of H-KSi3N4 helps to form a tight network structure and optimizes the dispersibility and structural density of the nanocapsules, but too high a content may lead to local agglomeration of particles.

[0120] In the present invention, 1.5%, 3%, 4.5%, 6%, 7.5% and 9% of H-KSi3N4 were added to samples U4 to U9, respectively, and the particle distribution and size change were analyzed by SEM. The experiment shows that when the HK Si3N4 content is 1.5% to 6% (samples U4 to U7), the particles are evenly distributed, the size gradually decreases, and the capsule structure is stable; when the content reaches 7.5% and above (samples U8 and U9), local agglomeration of particles occurs. The results show that an appropriate amount of HK Si3N4 can optimize the dispersibility and structural stability of the capsule, while excessive addition may lead to agglomeration, thereby affecting uniform distribution and performance.

[0121] Thermogravimetric analysis: Fig.14 A TG and DTG curve diagram of U1-U9 and NEPCM provided in an embodiment of the present invention, Fig.14 The TG and DTG curves of samples NEPCM, U1, U3, U5, U7 and U9 are shown in Figure 2. By analyzing the thermogravimetric data, the thermal stability of the samples can be systematically evaluated. Fig.14From the TG curve of (a), it can be seen that NEPCM (unmodified nano phase change capsule) shows a significant rapid weight drop between 200 and 300 °C, indicating that its thermal decomposition starting temperature is low and its thermal stability is relatively poor. U1 (unmodified 1% silicon nitride hybrid phase change nanocapsule) shows a certain improvement in thermal stability compared to NEPCM, but the effect is not good. As the amount of modified silicon nitride added to the surface of KH570 increases (U3, U5, U7 and U9), the thermal decomposition starting temperature of the material increases significantly, and the thermal weight loss process becomes more moderate, indicating that the enhanced effect of modified silicon nitride on thermal stability is particularly prominent.

[0122] from Fig.14 The DTG curve of (b) further shows that the weight loss peaks of NEPCM and U1 are high and concentrated, the decomposition process is violent, and the structural stability is weak. The weight loss peaks of U3 to U9 gradually shift to the high temperature zone, and the weight loss rate of U7 is the smallest, and the decomposition curve is more gentle, which shows that U7 has the best thermal stability and balance during the decomposition process. This performance improvement can be attributed to the uniform dispersion and good interface effect of silicon nitride modified on the surface of KH570 in the material, which significantly enhances the structural integrity and heat transfer efficiency of the phase change nanocapsules. It can be seen 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) performed best in balancing thermal stability and thermal conductivity, demonstrating its potential value in thermal management materials, especially in electronic device heat dissipation applications.

[0123] like Fig.14 As shown, the TG and DTG curves of samples NEPCM and U1 to U9 indicate that modified silicon nitride has a significant effect on improving the thermal stability of phase change nanocapsules. The thermal decomposition starting temperature of NEPCM is low, the decomposition process is violent, and the structural stability is poor; and with the increase in the addition amount of KH570 modified silicon nitride (U3 to U9), the thermal decomposition starting temperature of the material gradually increases, and the weight loss curve is flatter. Among them, U7 (6% KH570 modified silicon nitride) exhibits the best thermal stability and balance, showing the outstanding role of modified silicon nitride in improving the structural integrity and heat transfer efficiency of the material. This shows that the addition of 6% modified silicon nitride has the best effect in balancing thermal stability and thermal conductivity, and is suitable for thermal management materials and electronic device heat dissipation applications.

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

[0125] Improve thermal conductivity and thermal management efficiency: By introducing nano silicon nitride treated with KH570 modifier, the present invention effectively improves the thermal conductivity of phase change nano capsules. Experimental results show that the thermal conductivity of the modified nano capsules is 54.9% higher than that of ordinary phase change nano capsule materials, significantly enhancing the thermal management efficiency.

[0126] Enhanced thermal stability and durability: The bonding between modified nano silicon nitride and polyurea shell material is enhanced, which improves the stability of nanocapsules in high temperature environments. After 500 thermal cycle tests, the phase transition temperature of the modified nanocapsules did not change by more than 3°C, showing excellent thermal stability and durability.

[0127] Simplify the preparation process and reduce production costs: The preparation method of the present invention simplifies the traditional preparation process, avoids the use of expensive modification reagents and solvents, and thus directly reduces production costs. At the same time, the efficient use of KH570 modifier also reduces the consumption of raw materials, further optimizing cost-effectiveness.

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

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

[0130] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily required to implement the present invention.

[0131] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention or certain parts of the embodiments.

[0132] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0133] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A polyurea hybrid phase change nanocapsule, characterized in that: include: A core material, a shell material and a thermally conductive filler, wherein the shell material surrounds and wraps around the periphery of the core material, and the thermally conductive filler is evenly dispersed in the shell material; The core material is made of paraffin wax and is used to absorb or release latent heat during phase change to achieve temperature control and thermal energy storage; The shell material is made of polyurea material, which is wrapped around the outside of the paraffin wax, and the polyurea shell material is formed on the surface of the paraffin wax by interfacial polymerization; The thermal conductive filler is uniformly dispersed in the polyurea shell material and is composed of nano silicon nitride modified by KH570. The nano silicon nitride is uniformly dispersed in the polyurea shell material and forms a chemical bond or physical adsorption with the polyurea shell material.

2. The polyurea hybrid phase change nanocapsule according to claim 1, characterized in that: The overall shape of the nanocapsules is spherical.

3. A method for preparing polyurea hybrid phase change nanocapsules, characterized in that: include: Preparation of nano silicon nitride HK-Si3N4 modified by KH570; The paraffin is heated to a liquid state, and the liquid paraffin is uniformly mixed with HK-Si3N4 and stirred for a set time to obtain a mixed solution; the mixed solution is mixed with isophorone diisocyanate IPDI at 60° C. to form a polyurea shell, and the polyurea shell is wrapped around the surface of the paraffin particles to form an oil phase solution; Dissolve the emulsifier OP-10 in deionized water and stir evenly in a 60° C. constant temperature water bath to form an aqueous phase solution, and homogenize and emulsify the aqueous phase solution and the oil phase solution for a set time to form an oil-in-water emulsion; After diethylenetriamine DETA was dissolved in deionized water, the deionized water was added dropwise to the oil-in-water emulsion through a constant pressure funnel, and the mixture was stirred for reaction for 6 hours and then kept warm for 12 hours to obtain nanocapsules. The nanocapsules were washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven for a set time to obtain polyurea hybrid phase change nanocapsules NEPCMs.

4. The method for preparing polyurea hybrid phase change nanocapsules according to claim 3, characterized in that: The preparation of nano silicon nitride HK-Si3N4 modified by KH570 comprises: 6 g 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 of silicon nitride; The hydroxylated nano-silicon nitride was centrifuged twice at 12000 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 silicon nitride H-Si3N4 after centrifugal washing. H-Si3N4 and KH-570 in a certain proportion were mixed in an ethanol aqueous solution with an alcohol-water ratio of five to one, ultrasonically treated for 20 minutes, the pH was adjusted to 4.5-5.5 with glacial acetic acid, and stirred at 800 rpm for 3 hours at 80°C to complete the surface modification of H-Si3N4 by KH-570 to obtain nano silicon nitride HK-Si3N4 modified by KH570.

5. The method for preparing polyurea hybrid phase change nanocapsules according to claim 4, characterized in that: The contact angle of the nano silicon nitride material modified by KH570 is 106.6°±0.3°. During the modification process, the methoxy group in KH570 reacts with the hydroxyl group on the surface of the nano silicon nitride to form a covalent bond, and the long-chain alkyl group in KH570 is arranged on the surface of the nanoparticles to form a hydrophobic layer. The KH570 is covered on the surface of the nano silicon nitride by forming an organic silicon oxygen bond to form an organic protective layer.

6. The method for preparing polyurea hybrid phase change nanocapsules according to claim 5, characterized in that: The certain ratio includes 1:1 or 1:1.5 or 1:

2.

7. The method for preparing polyurea hybrid phase change nanocapsules according to claim 3, characterized in that: The HK-Si3N4 is uniformly stirred and mixed with paraffin and dispersed in the paraffin. The IPDI is used as a cross-linking agent. The diisocyanate group of IPDI reacts with 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 heat-conducting bridge between the paraffin wax and the polyurea shell.

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