Multi-element nano composite phase change energy storage microcapsule and preparation method thereof

Abstract

The invention discloses a multi-element nano composite phase change energy storage microcapsule and a preparation method thereof, and relates to the technical field of phase change energy storage materials. The microcapsule is composed of a core material and a shell material, the core material is a multi-element nano composite phase change core material which is compounded by a specific organic phase change material, and a pretreated nano heat conduction filler is added; the shell material is a composite shell material of modified graphene and silicon dioxide, and the graphene is modified by a specific silane coupling agent, so that the structural strength and the heat conduction enhancement effect of the shell material can be considered. The microcapsule prepared by the invention is wide in applicable temperature range, high in phase change energy storage efficiency and excellent in heat-conducting property, heat stability, mechanical property and recycling stability, the preparation process is simple and convenient, industrial production is easy to realize, and the microcapsule can be widely applied to the related fields of phase change energy storage.

Description

Technical Field

[0001] This invention relates to the field of phase change energy storage materials technology, and in particular to a multi-component nanocomposite phase change energy storage microcapsule and its preparation method. Background Technology

[0002] Phase change materials (PCMs), as functional materials capable of absorbing and releasing large amounts of heat within a specific temperature range through a phase change process while maintaining a relatively constant temperature, have become a key technological carrier for improving energy efficiency due to their high-efficiency energy storage and regulation capabilities. They demonstrate irreplaceable application value in several strategic fields, including building energy conservation, thermal management of electronic equipment, new energy storage, and temperature control of power batteries. In the building sector, embedding PCMs in walls, floors, or insulation layers can utilize their latent heat of phase change to balance the diurnal temperature range, reducing energy consumption of air conditioning, heating, and other equipment. In the field of electronic heat dissipation, with the continuous increase in chip integration and the surge in heat generation per unit area, PCMs can quickly absorb heat, preventing performance degradation or shortened lifespan of electronic components due to localized overheating. In the field of new energy storage, they can be used in conjunction with intermittent renewable energy sources such as solar and wind power to achieve stable energy storage and release, alleviating grid fluctuation pressure.

[0003] However, traditional single-type phase change materials face numerous performance shortcomings in practical applications, severely hindering their industrialization process. From a material category perspective, phase change energy storage materials are mainly divided into two categories: organic phase change materials and inorganic phase change materials. Both have their advantages and disadvantages, but both also suffer from unavoidable defects. Organic phase change materials possess significant advantages such as high latent heat of phase change, good chemical stability, no supercooling phenomenon, and low risk of phase separation. Furthermore, they are widely available and cost-effective, making them a promising candidate for application in medium- and low-temperature energy storage scenarios. However, the fatal flaw of organic phase change materials lies in their extremely low thermal conductivity. This results in low heat transfer efficiency during energy storage and release, making them unable to respond quickly to temperature changes. For example, when electronic devices suddenly overheat, organic phase change materials struggle to absorb heat rapidly, easily causing temperature runaway. Conversely, when heat needs to be released, the slow thermal conductivity leads to a lag in energy supply, failing to meet dynamic temperature control requirements.

[0004] In contrast, inorganic phase change materials (PCMs), while possessing higher thermal conductivity and effectively improving heat transfer rates, and with some being inexpensive and having a wide phase change temperature range, have found applications in high-temperature energy storage (such as industrial waste heat recovery), also have significant drawbacks. Firstly, their latent heat of phase change is generally lower, resulting in a much lower energy storage capacity per unit mass compared to organic PCMs, necessitating the use of large amounts of filler material in practical applications, increasing equipment size and weight. Secondly, inorganic PCMs are prone to severe supercooling during repeated phase change cycles, meaning the actual phase change temperature is far lower than the theoretical phase change temperature, and phase separation easily occurs, with the solid and liquid phases gradually separating, leading to continuous degradation of material performance and even complete loss of energy storage function.

[0005] To address these issues, researchers have proposed combining different phase change materials or introducing nano-thermal conductive fillers, while simultaneously encapsulating the phase change core material using microencapsulation technology to prevent core material leakage and oxidation. In existing microencapsulation products, the shell material is mostly a single polymer (such as melamine-formaldehyde resin) or a pure inorganic material (such as silica), which suffers from poor interfacial compatibility, low mechanical strength, and insufficient thermal stability. Core material blends are often limited to two organic phase change materials, and the nano-fillers exhibit poor dispersibility, making it difficult to simultaneously achieve a synergistic improvement in both high latent heat of phase change and high thermal conductivity. Furthermore, existing preparation methods often employ one-step in-situ polymerization, resulting in uneven shell coating and a tendency for core material leakage.

[0006] Therefore, developing a multi-component nanocomposite phase change energy storage microcapsule that combines high latent heat of phase change, high thermal conductivity, excellent cycle stability and mechanical properties has become a key requirement in the field. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-component nanocomposite phase change energy storage microcapsule and its preparation method, so as to solve the problems existing in the prior art.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] This invention provides a multi-component nanocomposite phase change energy storage microcapsule, comprising a core material and a shell material covering the core material;

[0010] The core material is a multi-component nanocomposite phase change core material, and the shell material is a composite shell material of modified graphene and silicon dioxide.

[0011] The raw materials of the core material include the following components in parts by weight: 40-60 parts of polyethylene glycol, 20-30 parts of lauric acid, and 5-15 parts of nano boron nitride;

[0012] The raw materials of the shell material include the following components in parts by weight: 10-20 parts of modified graphene, 30-50 parts of tetraethyl orthosilicate and 5-10 parts of ammonia.

[0013] The modified graphene is graphene modified with γ-aminopropyltriethoxysilane;

[0014] The nano-boron nitride is pretreated with silane coupling agent KH560.

[0015] As a further preferred embodiment of the present invention, the number average molecular weight of the polyethylene glycol is 4000-8000.

[0016] As a further preferred embodiment of the present invention, the particle size of the nano-boron nitride is 50-100 nm.

[0017] As a further preferred embodiment of the present invention, the mass ratio of the nano-boron nitride to the silane coupling agent KH560 is 1:1 to 1:3.

[0018] As a further preferred embodiment of the present invention, the mass ratio of γ-aminopropyltriethoxysilane to graphene is 1:2-1:5.

[0019] As a further preferred embodiment of the present invention, the particle size of the multi-component nanocomposite phase change energy storage microcapsule is 1-5 μm; the core material accounts for 60%-75% of the total mass of the multi-component nanocomposite phase change energy storage microcapsule, and the shell material accounts for 25%-40% of the total mass of the multi-component nanocomposite phase change energy storage microcapsule.

[0020] This invention innovatively adopts a dual-layer structure design with the synergistic cooperation of multiple core materials and composite shell materials. Starting from the two dimensions of core material thermal performance optimization and shell material protection enhancement, it constructs a microcapsule system that has wide temperature range applicability, high thermal conductivity and insulation and excellent structural stability, effectively breaking through the technical bottlenecks of traditional phase change microcapsules in thermal conductivity efficiency, temperature adaptation range and core material encapsulation stability.

[0021] At the core material design level, this invention uses polyethylene glycol (PEG) and lauric acid (LA) to form a basic organic phase change system. The core advantage of this compounding scheme lies in the complementarity of their phase change temperature ranges. PEG itself has an adjustable phase change temperature range, high latent heat of phase change, and good chemical stability, while lauric acid, as a short-chain fatty acid phase change material, has a lower phase change temperature and better thermal conductivity than most polymeric phase change materials. The compounding of the two can precisely broaden the applicable temperature range of the microcapsules, making them suitable for various application scenarios from room temperature to medium and low temperatures, such as heat dissipation of electronic devices, building insulation, and clothing temperature control, thus solving the problem of narrow temperature adaptability of single phase change materials.

[0022] To further enhance the thermal conductivity of the core material while meeting the stringent insulation requirements of the electronics industry, this invention innovatively introduces nano-boron nitride (BN) pretreated with the silane coupling agent KH560. Nano-boron nitride itself possesses extremely high thermal conductivity and excellent electrical insulation, making it an ideal thermally conductive filler material. However, untreated nano-boron nitride, due to its high surface energy, is prone to agglomeration in organic core materials, failing to provide thermal conductivity and potentially affecting the phase transition properties of the core material. After KH560 pretreatment, the epoxy groups in the KH560 molecules can chemically react with the hydroxyl groups on the surface of nano-boron nitride, forming an organic coating layer. This effectively reduces the surface energy of the nano-boron nitride, improves its dispersibility in the PEG-LA composite organic core material, and prevents agglomeration. This uniformly dispersed state creates a continuous thermal conductivity path within the core material, significantly improving the overall thermal conductivity while retaining its excellent insulation properties, meeting the dual requirements of thermal conductivity and insulation in electronic component heat dissipation scenarios.

[0023] In terms of shell design, this invention uses silicon dioxide (SiO2) as the basic shell material, primarily based on its excellent thermal stability and corrosion resistance. Silicon dioxide has a high melting point and a low coefficient of thermal expansion, making it less prone to deformation or decomposition at high temperatures, thus providing a stable protective barrier for the core material. Simultaneously, its chemical stability prevents it from reacting with acids, alkalis, and other substances in the external environment, effectively extending the lifespan of the microcapsules. However, a simple silicon dioxide shell suffers from insufficient mechanical strength, making it susceptible to cracking under external impact or during long-term use, leading to core material leakage and affecting the microcapsule's effectiveness. To address this issue, this invention introduces graphene modified with the silane coupling agent KH550, enhancing the shell's mechanical strength through its sheet-like structure. Graphene possesses extremely high tensile strength and elastic modulus; when uniformly dispersed within the silicon dioxide shell, it acts like a skeleton, supporting the shell structure, significantly improving its impact resistance and flexibility, and reducing the risk of shell breakage. Meanwhile, graphene's excellent thermal conductivity can further enhance the overall thermal conductivity of the microcapsules, forming a core-shell synergistic thermal conductivity system with the nano-boron nitride in the core material, further optimizing the heat dissipation effect of the microcapsules.

[0024] More importantly, the KH550 modification treatment not only improves the dispersibility of graphene in the silica shell, but also allows the amino groups in the graphene molecule to form hydrogen bonds with the hydroxyl groups of PEG and the carboxyl groups of LA in the core material. This hydrogen bonding creates a strong interfacial bond between the core and shell, significantly improving their interfacial compatibility and effectively suppressing leakage caused by volume changes during the phase transition. Simultaneously, this strong interfacial bond further enhances the overall mechanical strength of the microcapsules and increases their pyrolysis temperature. When the microcapsules are in a high-temperature environment, the robust interfacial bond reduces the difference in thermal expansion between the core and shell, preventing interfacial separation due to thermal stress, thereby improving the thermal stability of the microcapsules and ensuring they maintain stable structure and performance even at higher temperatures.

[0025] The present invention also provides a method for preparing the above-mentioned multi-component nanocomposite phase change energy storage microcapsules, comprising the following steps:

[0026] (1) Preparation of core material: Polyethylene glycol and lauric acid are heated and melted at 70-90℃ and mixed; then pretreated nano boron nitride is added and dispersed to obtain the core material;

[0027] The pretreated boron nitride nanoparticles are prepared through the following steps:

[0028] Add boron nitride nanoparticles to an ethanol aqueous solution and ultrasonically disperse for 30-60 min to obtain a boron nitride nanoparticle dispersion; add KH560 to the boron nitride nanoparticle dispersion at a mass ratio of 1:1-1:3, stir and react at 60-80℃ for 2-4 h, centrifuge after the reaction is completed, and dry the precipitate under vacuum for 8-12 h to obtain pretreated boron nitride nanoparticles.

[0029] (2) Preparation of core material emulsion: The core material is added to water, then an emulsifier is added, and the mixture is stirred to emulsify and obtain a core material emulsion;

[0030] (3) Preparation of microcapsules: Add modified graphene to the core material emulsion, stir and disperse, then heat to 40-50℃, add tetraethyl orthosilicate, then add ammonia to adjust the pH of the system to 9-10, and react at 60-70℃ for 4-6 hours; cool, separate, and dry to obtain multi-component nanocomposite phase change energy storage microcapsules.

[0031] As a further preferred embodiment of the present invention, in step (2), the mass ratio of the core material to water is 1:3-1:5; the emulsifier is sodium dodecylbenzenesulfonate; and the mass of the emulsifier is 2%-5% of the mass of the core material.

[0032] As a further preferred embodiment of the present invention, the method for preparing the modified graphene includes the following steps:

[0033] Graphene was dispersed in N,N-dimethylformamide, and KH550 was added to the resulting graphene dispersion. The mixture was refluxed at 80-100℃ for 4-6 hours, washed, and dried to obtain modified graphene.

[0034] The present invention further provides the application of the above-mentioned multi-component nanocomposite phase change energy storage microcapsules in the field of phase change energy storage.

[0035] This invention, through the scientific compounding and modification of multiple core materials, combined with the structural reinforcement and interface optimization of composite shell materials, constructs a double-layer microcapsule structure that not only has wide temperature range applicability, ultra-high thermal conductivity and excellent insulation, but also good mechanical strength, thermal stability and corrosion resistance. It effectively solves many shortcomings in the performance of traditional phase change microcapsules and has broad application prospects in multiple fields such as electronic heat dissipation, energy storage, and building energy conservation.

[0036] The present invention discloses the following technical effects:

[0037] This invention employs a synergistic innovation of multi-element core material compounding, composite shell material design, and preparation process, effectively overcoming the technical bottlenecks in performance and stability of traditional phase change energy storage microcapsules. Specifically, the basic organic phase change system, a compound of polyethylene glycol and lauric acid, not only broadens the applicable temperature range of the microcapsules to meet diverse application scenarios but also retains high latent heat of phase change, significantly improving energy storage efficiency. The dual thermal conductivity enhancement design of pretreated nano-boron nitride in the core material and modified graphene in the shell material can significantly improve the poor thermal conductivity of traditional organic phase change materials, solving the technical challenge of fast energy storage and slow energy release.

[0038] The composite shell material and stepwise preparation process of this invention can simultaneously improve the thermal stability and mechanical strength of microcapsules, avoiding damage and core material leakage under high temperature or external force; the stepwise in-situ polymerization process ensures that the shell material is uniformly coated on the surface of the core material, reducing core material loss and improving the consistency of products in industrial production.

[0039] The microcapsules of this invention possess both excellent insulation and cycle stability, maintaining stable performance even during long-term repeated use. They can be safely applied in multiple fields such as building energy conservation, electronic heat dissipation, and new energy storage, effectively expanding the application boundaries of phase change energy storage materials and demonstrating outstanding technological innovation and practical value. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0046] This invention utilizes a multi-component nanocomposite phase change energy storage microcapsule to successfully overcome the performance bottlenecks of traditional phase change energy storage materials through synergistic innovation in both core and shell materials. At the core material level, the composite system of polyethylene glycol and lauric acid not only broadens the phase change temperature range, making it adaptable to various scenarios requiring 45-65℃, but also retains a high latent heat of phase change of 185-200 J / g, significantly improving energy storage efficiency. Pre-treated boron nitride nanoparticles with KH560 effectively solve the problem of nanofiller agglomeration, constructing a continuous thermal conductivity path within the core material, increasing the thermal conductivity to 0.85-1.0 W / (m·K), more than twice that of materials without boron nitride nanoparticles. In terms of shell design, the composite structure of modified graphene and silicon dioxide leverages the high mechanical strength of graphene to increase the compressive strength of the microcapsule to 15-20 MPa, while the interface modification effect of KH550 enhances the compatibility between the core and shell, allowing the thermal decomposition temperature to exceed 300℃, providing stable protection for the core material.

[0047] From the perspectives of preparation process and practicality, the stepwise in-situ polymerization process of this invention has significant advantages. This process, through the stepwise operation of first dispersing modified graphene and then introducing tetraethyl orthosilicate, ensures uniform coating of the shell material on the core material surface, achieving a coating rate of 95%-98%. Simultaneously, operations such as ultrasonic dispersion and precise temperature control in the process are easily standardized and controlled, requiring no special high-end equipment, thus possessing industrial production potential. Performance testing further verifies the practical value of the microcapsules. After 500 thermal cycles, the latent heat decay rate is only 4.15%, and the leakage rate is as low as 0.8%, while maintaining a good spherical structure. Compared with the comparative example's decay rate of over 15% and leakage rate of 5.8%, this fully demonstrates its excellent cycle stability and core material encapsulation capability, meeting the requirements for long-term repeated use.

[0048] A first aspect of the present invention is to provide a multi-component nanocomposite phase change energy storage microcapsule, comprising a core material and a shell material covering the core material;

[0049] The core material is a multi-component nanocomposite phase change core material, and the shell material is a composite shell material of modified graphene and silicon dioxide.

[0050] The raw materials of the core material include the following components in parts by weight: 40-60 parts of polyethylene glycol, 20-30 parts of lauric acid, and 5-15 parts of nano boron nitride;

[0051] The raw materials of the shell material include the following components in parts by weight: 10-20 parts of modified graphene, 30-50 parts of tetraethyl orthosilicate and 5-10 parts of ammonia.

[0052] The modified graphene is graphene modified with γ-aminopropyltriethoxysilane;

[0053] The nano-boron nitride is pretreated with silane coupling agent KH560.

[0054] Furthermore, the number-average molecular weight of the polyethylene glycol is 4000-8000.

[0055] Furthermore, the particle size of the said boron nitride nanoparticles is 50-100 nm.

[0056] Furthermore, the mass ratio of the nano-boron nitride to the silane coupling agent KH560 is 1:1 to 1:3.

[0057] Furthermore, the mass ratio of γ-aminopropyltriethoxysilane to graphene is 1:2 to 1:5.

[0058] Furthermore, the particle size of the multi-component nanocomposite phase change energy storage microcapsule is 1-5 μm; the core material accounts for 60%-75% of the total mass of the multi-component nanocomposite phase change energy storage microcapsule, and the shell material accounts for 25%-40% of the total mass of the multi-component nanocomposite phase change energy storage microcapsule.

[0059] A second aspect of the present invention provides a method for preparing the above-mentioned multi-component nanocomposite phase change energy storage microcapsules, comprising the following steps:

[0060] (1) Preparation of core material: Polyethylene glycol and lauric acid are heated and melted at 70-90℃ and mixed; then pretreated nano boron nitride is added and dispersed to obtain the core material;

[0061] The pretreated boron nitride nanoparticles are prepared through the following steps:

[0062] Add boron nitride nanoparticles to an ethanol aqueous solution and ultrasonically disperse for 30-60 min to obtain a boron nitride nanoparticle dispersion; add KH560 to the boron nitride nanoparticle dispersion at a mass ratio of 1:1-1:3, stir and react at 60-80℃ for 2-4 h, centrifuge after the reaction is completed, and dry the precipitate under vacuum for 8-12 h to obtain pretreated boron nitride nanoparticles.

[0063] (2) Preparation of core material emulsion: The core material is added to water, then an emulsifier is added, and the mixture is stirred to emulsify and obtain a core material emulsion;

[0064] (3) Preparation of microcapsules: Add modified graphene to the core material emulsion, stir and disperse, then heat to 40-50℃, add tetraethyl orthosilicate, then add ammonia to adjust the pH of the system to 9-10, and react at 60-70℃ for 4-6 hours; cool, separate, and dry to obtain multi-component nanocomposite phase change energy storage microcapsules.

[0065] Further, in step (2), the mass ratio of the core material to water is 1:3-1:5; the emulsifier is sodium dodecylbenzenesulfonate; and the mass of the emulsifier is 2%-5% of the core material mass.

[0066] Furthermore, the preparation method of the modified graphene includes the following steps:

[0067] Graphene was dispersed in N,N-dimethylformamide, and KH550 was added to the resulting graphene dispersion. The mixture was refluxed at 80-100℃ for 4-6 hours, washed, and dried to obtain modified graphene.

[0068] The present invention further provides the application of the above-mentioned multi-component nanocomposite phase change energy storage microcapsules in the field of phase change energy storage.

[0069] Example 1

[0070] Preparation of multi-component nanocomposite phase change energy storage microcapsules:

[0071] (1) Preparation of pretreated boron nitride nanoparticles: 5g of boron nitride nanoparticles (50nm particle size) were added to 50mL of 50% ethanol aqueous solution and ultrasonically dispersed for 30min; 5g of KH560 was added and stirred at 60℃ for 2h; centrifugation was performed and the precipitate was vacuum dried at 50℃ for 8h to obtain pretreated boron nitride nanoparticles.

[0072] (2) Preparation of multi-component nanocomposite phase change core material: Weigh 40g PEG4000 and 20g lauric acid, heat to 70℃ to melt and stir evenly; add 5g pretreated nano boron nitride, stir for 30min, and ultrasonically disperse for 20min to obtain core material.

[0073] (3) Preparation of modified graphene: 10g of graphene was added to 500mL of N,N-dimethylformamide and ultrasonically dispersed for 40min; 20g of KH550 was added and refluxed at 80℃ for 4h; the mixture was filtered, the filter cake was washed three times with ethanol and vacuum dried at 50℃ for 10h to obtain modified graphene.

[0074] (4) Preparation of core material emulsion: Add 180g of deionized water to the core material (the mass ratio of core material to water is 1:3), add 1.2g of sodium dodecylbenzenesulfonate (2% of the core material mass), stir and emulsify at 3000r / min for 20min to obtain the core material emulsion.

[0075] (5) Stepwise in-situ polymerization: Add 10g of modified graphene to the core material emulsion and stir and disperse at 2000r / min for 20min; heat to 40℃ and add 30g of tetraethyl orthosilicate (to be added in 1h), and continue stirring for 1h; add 5g of ammonia to adjust pH=9, heat to 60℃ and keep the reaction at this temperature for 4h; after cooling, centrifuge, wash the precipitate three times each with deionized water and ethanol, and dry it under vacuum at 50℃ for 12h to obtain microcapsules.

[0076] Example 2

[0077] Preparation of multi-component nanocomposite phase change energy storage microcapsules:

[0078] (1) Preparation of pretreated boron nitride nanoparticles: 5g of boron nitride nanoparticles (50nm particle size) were added to 50mL of 50% ethanol aqueous solution and ultrasonically dispersed for 30min; 5g of KH560 was added and stirred at 60℃ for 2h; centrifugation was performed and the precipitate was vacuum dried at 50℃ for 8h to obtain pretreated boron nitride nanoparticles.

[0079] (2) Preparation of multi-component nanocomposite phase change core material: Weigh 40g PEG4000 and 30g lauric acid, heat to 70℃ to melt and stir evenly; add 8g pretreated nano boron nitride, stir for 30min, and ultrasonically disperse for 20min to obtain core material.

[0080] (3) Preparation of modified graphene: 15g of graphene was added to 500mL of N,N-dimethylformamide and ultrasonically dispersed for 40min; 20g of KH550 was added and refluxed at 80℃ for 4h; the mixture was filtered, the filter cake was washed three times with ethanol and vacuum dried at 50℃ for 10h to obtain modified graphene.

[0081] (4) Preparation of core material emulsion: Add 180g of deionized water to the core material (the mass ratio of core material to water is 1:3), add 1.2g of sodium dodecylbenzenesulfonate (2% of the core material mass), stir and emulsify at 3000r / min for 20min to obtain the core material emulsion.

[0082] (5) Stepwise in-situ polymerization: Add 10g of modified graphene to the core material emulsion and stir and disperse at 2000r / min for 20min; heat to 40℃ and add 30g of tetraethyl orthosilicate (to be added in 1h), and continue stirring for 1h; add 5g of ammonia to adjust pH=9, heat to 60℃ and keep the reaction at this temperature for 4h; after cooling, centrifuge, wash the precipitate three times each with deionized water and ethanol, and dry it under vacuum at 50℃ for 12h to obtain microcapsules.

[0083] Example 3

[0084] Preparation of multi-component nanocomposite phase change energy storage microcapsules:

[0085] (1) Preparation of pretreated boron nitride nanoparticles: 10g of boron nitride nanoparticles (50nm particle size) were added to 50mL of 50% ethanol aqueous solution and ultrasonically dispersed for 30min; 15g of KH560 was added and stirred at 60℃ for 2h; centrifugation was performed and the precipitate was vacuum dried at 50℃ for 8h to obtain pretreated boron nitride nanoparticles.

[0086] (2) Preparation of multi-component nanocomposite phase change core material: Weigh 55g PEG4000 and 20g lauric acid, heat to 70℃ and melt and stir evenly; add 5g pretreated nano boron nitride, stir for 30min, and ultrasonically disperse for 20min to obtain core material.

[0087] (3) Preparation of modified graphene: 10g of graphene was added to 500mL of N,N-dimethylformamide and ultrasonically dispersed for 40min; 20g of KH550 was added and refluxed at 80℃ for 4h; the mixture was filtered, the filter cake was washed three times with ethanol and vacuum dried at 50℃ for 10h to obtain modified graphene.

[0088] (4) Preparation of core material emulsion: Add 180g of deionized water to the core material (the mass ratio of core material to water is 1:3), add 1.2g of sodium dodecylbenzenesulfonate (2% of the core material mass), stir and emulsify at 3000r / min for 20min to obtain the core material emulsion.

[0089] (5) Stepwise in-situ polymerization: Add 10g of modified graphene to the core material emulsion and stir and disperse at 2000r / min for 20min; heat to 40℃ and add 30g of tetraethyl orthosilicate (dropped over 1h), and continue stirring for 1h; add 5g of ammonia to adjust pH=9, heat to 65℃ and keep warm for 4h; after cooling, centrifuge, wash the precipitate three times each with deionized water and ethanol, and dry under vacuum at 50℃ for 12h to obtain microcapsules.

[0090] Comparative Example 1

[0091] The only difference from Example 1 is that the core material does not contain lauric acid and nano boron nitride components.

[0092] Comparative Example 2

[0093] The only difference from Example 1 is that the core material does not contain nano boron nitride components.

[0094] Comparative Example 3

[0095] The only difference from Example 1 is that the core material, nano-boron nitride, was not pretreated with KH560.

[0096] Comparative Example 4

[0097] The only difference from Example 1 is that the shell material does not contain modified graphene components.

[0098] Comparative Example 5

[0099] The only difference from Example 1 is that step (5) in the preparation process uses a one-step in-situ polymerization:

[0100] Steps (1)-(4) are the same as in Example 1;

[0101] (5) Add 10g of modified graphene and 30g of tetraethyl orthosilicate to the core material emulsion, stir and disperse at 2000r / min for 20min; heat to 40℃ and continue stirring for 1h; add 5g of ammonia water to adjust pH=9, heat to 60℃ and keep warm for 4h; after cooling, centrifuge, wash the precipitate with deionized water and ethanol 3 times each, and vacuum dry at 50℃ for 12h to obtain microcapsules.

[0102] Effect verification:

[0103] 1. Basic performance testing

[0104] The latent heat of phase change and phase change temperature of the microcapsules were tested using a differential scanning calorimeter (DSC, model TA Q2000) (heating rate 10℃ / min, nitrogen atmosphere);

[0105] Thermal conductivity was tested using a laser thermal conductivity meter (Netzsch LFA 467) (room temperature, sample thickness 2 mm).

[0106] Particle size and morphology were observed using a scanning electron microscope (SEM, model Zeiss Sigma 300).

[0107] The coating rate was calculated using Soxhlet extraction (uncoated core material was extracted with ethanol, coating rate = (1 - mass loss after extraction / theoretical amount of core material added) × 100%), and the results are shown in Table 1 below:

[0108] Table 1

[0109]

[0110] Test results show that the microcapsules of this invention have excellent performance, with a latent heat of phase change of 185-200 J / g, a thermal conductivity of 0.85-1.0 W / (m·K), a thermal decomposition temperature of over 300℃, and a compressive strength of 15-20 MPa.

[0111] 2. Cyclic performance test

[0112] The microcapsules of Example 2 and the comparative examples were subjected to thermal cycling tests: The samples were subjected to repeated heating-cooling cycles within the corresponding phase transition temperature range (Example 2: 40-70℃; Comparative Examples 1-5: 35-65℃), with each cycle maintaining a heating / cooling period of 1 hour. The latent heat of phase transition was measured after 100, 300, and 500 cycles, and the decay rate was calculated. The results are shown in Table 2 below.

[0113] Table 2

[0114]

[0115] The microcapsules prepared by this invention have excellent cycle stability and can meet the requirements for long-term repeated use.

[0116] 3. Leakage rate test

[0117] The microcapsules (10g) from Example 2 and each comparative example were evenly spread on qualitative filter paper and placed in a 60℃ oven (higher than the phase transition temperature of all samples) for 24 hours. The change in mass of the filter paper before and after the heat preservation was measured, and the leakage rate was calculated (leakage rate = (mass of filter paper after heat preservation - mass of filter paper before heat preservation) / mass of microcapsules × 100%). The results are shown in Table 3 below:

[0118] Table 3

[0119] Leakage rate (%) Visual inspection (after insulation) Example 2 0.8 The filter paper was free of oil stains, and the microcapsules showed no adhesion. Comparative Example 1 3.5 There were small oil stains on the edges of the filter paper, and the microcapsules were slightly stuck together. Comparative Example 2 2.8 There were oil stains on some parts of the filter paper, and a small amount of microcapsules were stuck together. Comparative Example 3 2.2 The filter paper showed no obvious oil stains, and the microcapsules showed no obvious adhesion. Comparative Example 4 3.2 There were oil stains on the edges of the filter paper, and the microcapsules were partially adhered. Comparative Example 5 5.8 The filter paper had large areas of oil stains, and the microcapsules were severely adhered.

[0120] The multi-component nanocomposite phase change energy storage microcapsules of this invention possess high energy storage efficiency, high thermal conductivity, excellent mechanical properties and thermal stability, while retaining good insulation properties. They can be flexibly adapted to diverse scenarios such as building energy conservation, electronic heat dissipation, and new energy storage. The phase change energy storage material provided by this invention promotes the industrialization and multi-scenario application of phase change energy storage technology, and has significant technical reference value and market application prospects.

[0121] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A multi-component nanocomposite phase change energy storage microcapsule, characterized in that, Includes the core material and the shell material covering the core material; The core material is a multi-component nanocomposite phase change core material, and the shell material is a composite shell material of modified graphene and silicon dioxide. The raw materials of the core material include the following components in parts by weight: 40-60 parts of polyethylene glycol, 20-30 parts of lauric acid, and 5-15 parts of nano boron nitride; The raw materials of the shell material include the following components in parts by weight: 10-20 parts of modified graphene, 30-50 parts of tetraethyl orthosilicate and 5-10 parts of ammonia. The modified graphene is graphene modified with γ-aminopropyltriethoxysilane; The nano-boron nitride is pretreated with silane coupling agent KH560.

2. The multi-component nanocomposite phase change energy storage microcapsule according to claim 1, characterized in that, The number average molecular weight of the polyethylene glycol is 4000-8000.

3. The multi-component nanocomposite phase change energy storage microcapsule according to claim 1, characterized in that, The particle size of the boron nitride nanoparticles is 50-100 nm.

4. The multi-component nanocomposite phase change energy storage microcapsule according to claim 1, characterized in that, The mass ratio of the nano-boron nitride to the silane coupling agent KH560 is 1:1 to 1:

3.

5. The multi-component nanocomposite phase change energy storage microcapsule according to claim 1, characterized in that, The mass ratio of γ-aminopropyltriethoxysilane to graphene is 1:2 to 1:

5.

6. The multi-component nanocomposite phase change energy storage microcapsule according to claim 1, characterized in that, The particle size of the multi-component nanocomposite phase change energy storage microcapsule is 1-5 μm; the core material accounts for 60%-75% of the total mass of the multi-component nanocomposite phase change energy storage microcapsule, and the shell material accounts for 25%-40% of the total mass of the multi-component nanocomposite phase change energy storage microcapsule.

7. The method for preparing the multi-component nanocomposite phase change energy storage microcapsules according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of core material: Polyethylene glycol and lauric acid are heated, melted and mixed; Then, pretreated nano-boron nitride is added and dispersed to obtain the core material; The pretreated boron nitride nanoparticles are prepared through the following steps: Nano-boron nitride was added to an ethanol aqueous solution and ultrasonically dispersed to obtain a nano-boron nitride dispersion. KH560 was added to the nano-boron nitride dispersion and the mixture was stirred at 60-80℃ for 2-4 hours. After the reaction was completed, the mixture was centrifuged and the precipitate was dried to obtain pretreated nano-boron nitride. (2) Preparation of core material emulsion: The core material is added to water, then an emulsifier is added, and the mixture is stirred to emulsify and obtain a core material emulsion; (3) Preparation of microcapsules: Add modified graphene to the core material emulsion, stir and disperse, then heat to 40-50℃, add tetraethyl orthosilicate, then add ammonia to adjust the pH of the system to 9-10, and react at 60-70℃ for 4-6 hours; cool, separate, and dry to obtain multi-component nanocomposite phase change energy storage microcapsules.

8. The preparation method according to claim 7, characterized in that, In step (2), the mass ratio of the core material to water is 1:3-1:5; the emulsifier is sodium dodecylbenzenesulfonate; and the mass of the emulsifier is 2%-5% of the core material mass.

9. The preparation method according to claim 7, characterized in that, The method for preparing the modified graphene includes the following steps: Graphene was dispersed in N,N-dimethylformamide, and KH550 was added to the resulting graphene dispersion. The mixture was refluxed at 80-100℃ for 4-6 hours, washed, and dried to obtain modified graphene.

10. The application of the multi-component nanocomposite phase change energy storage microcapsules as described in any one of claims 1-6 in the field of phase change energy storage.

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