Cold storage phase change core-shell composite material, preparation method and application

Abstract

The invention discloses a cold storage phase change core-shell composite material and a preparation method thereof. The composite material comprises a porous heat-conducting matrix and a three-layer cascade phase-change core-shell structure loaded in pores of the porous heat-conducting matrix. The core-shell structure sequentially comprises an outer shell, an inner shell and a core from outside to inside, and the phase change temperatures of the outer shell, the inner shell and the core are gradually increased in a stepped manner to form a wide-temperature-zone sequential phase change response of 25-33 DEG C. According to the porous heat-conducting matrix, the heat-conducting property of the composite material is remarkably improved through a three-dimensional heat-conducting network constructed by the porous heat-conducting matrix, and meanwhile, the core-shell structure is effectively prevented from physical leakage by utilizing capillary acting force and physical space limitation generated by micro-nano pores of the porous heat-conducting matrix. The overall phase change latent heat of the prepared cold storage phase change core-shell composite material is larger than or equal to 180 J / g, the heat conductivity coefficient is larger than or equal to 1.8 W / (m.K), and the cold storage phase change core-shell composite material has gradient temperature control, rapid thermal response and excellent leakage prevention performance and is particularly suitable for the individual thermal protection field such as high-ground-temperature mine protective clothing.

Description

TECHNICAL FIELD

[0001] The application relates to a cold storage phase change core-shell composite material, a preparation method and application, and belongs to the technical field of functional composite materials. BACKGROUND

[0002] Coal is the main energy source in China. With the exhaustion of shallow resources, the mining depth is extending to the deep part of the earth at a rate of 8-25 meters per year. The increase in mining depth leads to a significant effect of the geothermal gradient, and mine heat damage has become one of the main obstacles to the safe and efficient mining of deep resources. Long-term exposure of miners to high temperature and high humidity in a harsh environment seriously affects the health of miners and the safety of underground operation. Therefore, providing reliable individual cooling protection for front-line miners has become an urgent engineering problem to be solved.

[0003] To address this problem, individual cooling protection technology, especially cooling clothes based on phase change materials (PCMs), has received widespread attention. This kind of technology uses the characteristics of phase change materials that absorb or release a large amount of latent heat when phase change occurs to regulate the temperature of the microenvironment.

[0004] However, the existing phase change cooling materials applied in mines have many limitations: first, most materials only have a single phase change temperature, which cannot cover the wide range of comfortable zone requirements of the human body in a dynamic thermal environment, resulting in inaccurate temperature control. Second, organic phase change materials generally have low thermal conductivity, resulting in slow thermal response speed and the inability to timely absorb the heat generated by the human body. Third, solid-liquid phase change materials are prone to leakage after melting, affecting the service life and safety of the materials. Although microencapsulation technology can solve the leakage problem to some extent, the preparation process is often complex and the phase change latent heat and thermal conductivity of the material are often sacrificed.

[0005] To overcome the limitations of single phase change materials, researchers have tried to develop multi-layer core-shell structures to achieve multifunctional integration. However, multi-layer coating requires multiple self-assembly and separation and drying steps, which is a tedious and lengthy process, and is prone to cause poor interface bonding of the shell layer and peeling, making it difficult to achieve large-scale production and application. Therefore, there is an urgent need for a cold storage phase change composite material that has a gradient phase change temperature zone, high thermal conductivity, excellent leakage prevention performance, and is easy to prepare. SUMMARY

[0006] The application provides a cold storage phase change core-shell composite material, a preparation method and application. Through the design of the core-shell structure, the phase change core-shell composite material has three precise gradient phase change temperature zones, which can accurately match the human body thermal comfort interval, and has high thermal conductivity and excellent leakage prevention performance.

[0007] According to one aspect of this application, a cold storage phase change core-shell composite material is provided, the core-shell composite material comprising a porous thermally conductive matrix and a core-shell structure loaded in the pores of the porous thermally conductive matrix; The core-shell structure is a three-layered stepped phase change core-shell structure with increasing phase change temperature from the outside to the inside. The core-shell structure includes a core, an inner shell, and an outer shell. The core and the inner shell are solid, and the outer shell is solid before a phase change occurs, and becomes molten after absorbing heat and undergoing a phase change. The porous thermally conductive substrate realizes the thermal conductivity of the core-shell structure through its own three-dimensional thermally conductive network. The micro-nano pores of the porous thermally conductive substrate provide strong capillary forces and physical space constraints for the loaded core-shell structure, preventing physical leakage of the core-shell structure.

[0008] Preferably, the overall latent heat of phase change of the core-shell composite material is ≥180 J / g, and the thermal conductivity is ≥1.8 W / (m·K).

[0009] Preferably, the phase transition temperatures of the core, the inner shell, and the outer shell decrease in a stepwise manner; The core, the inner shell, and the outer shell sequentially enclose each other from the inside out, forming a phase transition temperature that increases progressively. Ternary low-temperature eutectic composite.

[0010] Preferably, the deformation temperature of the core is 31℃~33℃; the phase transition temperature of the inner shell is 28℃~30℃; and the phase transition temperature of the outer shell is 25℃~27℃.

[0011] Preferably, the outer shell is a ternary low-temperature eutectic composite of lauric acid, n-octadecane, and hexadecyl alcohol prepared by melt blending. The inner shell is a ternary low-temperature eutectic composite of myristic acid, n-nonadecane, and octadecyl alcohol prepared by melt blending. The core is a ternary low-temperature eutectic composite of palmitic acid, n-eicosane, and octadecyl alcohol prepared by melt blending.

[0012] Preferably, the porosity of the porous thermally conductive matrix is ​​80%~95%, and the mass of the porous thermally conductive matrix accounts for 50%~75% of the total mass of the phase change core-shell composite material; The porous thermally conductive substrate is a graphite-based porous material.

[0013] According to another aspect of this application, a method for preparing a cold-storage phase change core-shell composite material is provided, the method comprising the following steps: S1, Preparation of pore-matched phase change core-shell materials with graphite-based porous materials; S2, the phase change core-shell material prepared in S1 is mixed with activated graphite-based porous material at a mass ratio of 1:2 to 1:3 to obtain a mixture; S3, the mixture is placed in a vacuum environment of 60℃~80℃, so that the core and shell materials melt and penetrate and are uniformly loaded into the macropores of the graphite-based porous carrier; S4. The final product of S3 is cooled to room temperature to obtain the final cold storage phase change core-shell composite material.

[0014] Preferably, the method for preparing the phase change core-shell material includes: S101, respectively prepare outer shell material, inner shell material and core material; S102, the outer shell, inner shell and core materials prepared by S101 are crushed and passed through an 80-100 mesh sieve to obtain corresponding particles so that the particle size after blending matches the pore size of the graphite-based porous material. S103, for the self-assembly of phase change core-shell materials, specifically includes: ① The inner shell material is melted at a temperature T1, wherein the temperature T1 is 5°C to 10°C higher than the phase transformation temperature of the inner shell material; ② Add solid composite phase change core material particles to the molten inner shell material and stir at a speed of 200 r / min to 400 r / min for 0.5 h to 1 h to form a primary core-shell structure consisting of a core and an inner shell. After cooling, pulverize to a particle size of 50 μm to 100 μm. ③ Melt the outer shell material at a temperature T2, wherein the temperature T2 is 5°C to 10°C higher than the phase transition temperature of the outer shell material; ④ Add the primary core-shell structure particles obtained in step ② to the molten outer shell material, and stir at a speed of 200 r / min to 400 r / min for 1 h to 2 h to form a triple core-shell structure consisting of a core material, an inner shell, and an outer shell; after cooling, a phase change core-shell material is obtained.

[0015] Preferably, the shell material is prepared by weighing lauric acid, n-octadecane and hexadecyl alcohol in a mass ratio of 1:(0.5~1.5):(0.2~0.8), melting them at 60℃~65℃ under nitrogen protection, mechanically stirring at a speed of 400r / min~500r / min for 1 hour~1.5 hours, and then cooling and solidifying to obtain the shell material; The inner shell material is prepared as follows: myristic acid, n-nonadecane and octadecyl alcohol are weighed in a mass ratio of 1:(0.8~1.8):(0.3~0.7), melted at 65℃~70℃ under nitrogen protection, and mechanically stirred at a speed of 400r / min~500r / min for 1 hour~1.5 hours, and then cooled and solidified to obtain the inner shell material; The core material is prepared by weighing palmitic acid, n-eicosane and octadecyl alcohol in a mass ratio of 1:(0.6~1.2):(0.1~0.4), melting them at 70℃~75℃ under nitrogen protection, and mechanically stirring them at a speed of 400r / min~500r / min for 1 hour~1.5 hours, followed by cooling and solidification to obtain the core material.

[0016] According to another aspect of this application, an application of a cold-storage phase change core-shell composite material is provided, wherein the phase change core-shell composite material is used in protective clothing materials for high-temperature mines; The phase change core-shell composite material is cut or molded into the required shape and integrated into the interlayer of the mining protective clothing.

[0017] The beneficial effects that this application can produce include: The cold-storing phase-change core-shell composite material described in this application, through molecular design, selected three fatty acids, alkanes, and fatty alcohols with different carbon chain lengths. Utilizing the differences in hydrogen bonds and van der Waals forces formed between them, three ternary cryogenic eutectic composites with precisely progressive phase-change temperatures were prepared, providing the chemical basis for sequential phase transitions. Within a wide temperature range of 25℃ to 33℃, three clear and independent phase-change plateaus were achieved: the outer shell at 25℃ to 27℃, the inner shell at 28℃ to 30℃, and the core at 31℃ to 33℃. When the ambient temperature changes from low to high, the material undergoes phase-change endothermic processes sequentially from the outer shell to the core, thereby stabilizing the microenvironment temperature within a comfortable range and avoiding sudden temperature increases.

[0018] By encapsulating the outer shell from the inside out, the physical structural sequence of the outer shell, inner shell, and core provides a physical guarantee for the phase transition sequence. This three-layered, stepped phase transition core-shell structure achieves an increasing phase transition temperature from the outside in. As the temperature rises, the outermost material reaches its phase transition point first and melts, absorbing heat. Because it is encapsulated outside the inner layers, there is a certain lag in heat transfer to the inner phase transition materials, thus achieving separation of the phase transition reactions in time.

[0019] In this application, a macroscopic graphite-based porous carrier (such as expanded graphite plate or graphene foam) is used as the main framework. Based on the high thermal conductivity of graphite, its interconnected porous structure constructs a continuous, three-dimensional thermal conductivity pathway within the composite material. This is significantly different from simply dispersing graphite powder as a filler in a phase change material, where the high contact resistance between fillers limits the thermal conductivity improvement. The three-dimensional continuous thermal network acts as a highly efficient heat conduction path, allowing heat to be preferentially and rapidly transferred to all corners through this low-thermal-resistance graphite network, and then efficiently transferred from the network to the phase change core-shell structure loaded in its pores, thus greatly shortening the thermal response time. This significantly improves the overall thermal conductivity of the prepared cold-storage phase change core-shell composite material. This enables heat to be rapidly transferred from a heat source (such as the human body) to the interior of the material, activating a larger volume of the phase change material and avoiding the problem of localized overheating while other parts remain unactivated.

[0020] Ultimately, the microscopic core-shell structure is loaded onto a macroscopic graphite matrix, resulting in a composite material that combines flexibility with a certain strength, making it easy to integrate with existing protective clothing manufacturing processes through post-processing methods such as cutting and molding.

[0021] This application achieves a three-layer core-shell microstructure by precisely controlling the composition of each phase change layer in the core-shell structure. By integrating the core-shell structure load into a porous thermally conductive material, it successfully solves three major technical challenges simultaneously within a single material system: a single phase change temperature range, slow thermal response, and easy leakage. Ultimately, this results in a high-performance, long-life individual cooling material suitable for harsh environments such as high-temperature mines.

[0022] The final product is a solid block or sheet composite material with good mechanical strength. It can be directly cut, sewn, or embedded into the interlayer of existing mining protective clothing, and the integration process is simple. In high-temperature mining environments, this material can continuously absorb heat through a stepwise phase change, stabilizing the temperature of the protective clothing's microclimate within a comfortable range of 25℃~31℃ for more than 4 hours. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the cold storage phase change core-shell composite material in an embodiment of the present invention; Figure 2 This is a schematic diagram of the core-shell structure in the cold storage phase change core-shell composite material according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the application of the cold storage phase change core-shell composite material in an embodiment of the present invention; In the diagram: 1. Core; 2. Inner shell; 3. Outer shell; 4. Porous thermally conductive substrate; 5. Core-shell structure. Detailed Implementation

[0024] According to one embodiment of this application, a cold storage phase change core-shell composite material is provided, the core-shell composite material comprising a porous thermally conductive matrix and a core-shell structure loaded in the pores of the porous thermally conductive matrix; The core-shell structure is a three-layered stepped phase change core-shell structure with increasing phase change temperature from the outside to the inside. The core-shell structure includes a core, an inner shell, and an outer shell. The core and the inner shell are solid, and the outer shell is solid before a phase change occurs, and becomes molten after absorbing heat and undergoing a phase change. The porous thermally conductive substrate realizes the thermal conductivity of the core-shell structure through its own three-dimensional thermally conductive network. The micro-nano pores of the porous thermally conductive substrate provide strong capillary forces and physical space constraints for the loaded core-shell structure, preventing physical leakage of the core-shell structure.

[0025] In this application, the overall latent heat of phase change of the core-shell composite material is ≥180 J / g, and the thermal conductivity is ≥1.8 W / (m·K).

[0026] It should be noted that: The existing phase change cooling materials for individual mines have a single phase change temperature that cannot be matched to the human body. The application addresses several technical bottlenecks, including dynamic thermal comfort range, slow thermal response due to low inherent thermal conductivity, poor cycle stability due to easy leakage during solid-liquid phase transitions, and the complexity and difficulty in industrializing traditional multi-layer core-shell structures. It utilizes a porous thermally conductive substrate as a carrier to load a core-shell structure with a core, inner shell, and outer shell within the pores of the substrate. The core-shell structure is a three-layered, stepped phase transition core-shell structure with increasing phase transition temperature from the outside to the inside, achieving a gradient thermal response to adapt to human movement. In the thermal comfort range, a porous thermally conductive substrate is used as a carrier. The three-dimensional thermal conductivity network of the porous substrate facilitates heat conduction, achieving rapid thermal response. Furthermore, the micro-nano pores of the porous substrate provide strong capillary forces and physical spatial confinement for the supported core-shell structure, preventing physical leakage. This simultaneously solves the two major challenges of low thermal conductivity and easy leakage in materials, achieving both rapid thermal response and long-term cycling stability.

[0027] In this application, the phase transition temperatures of the core, the inner shell, and the outer shell decrease in a stepwise manner; The core, the inner shell, and the outer shell sequentially enclose each other from the inside out, forming a phase transition temperature that increases progressively. Ternary low-temperature eutectic composite.

[0028] In this application, the deformation temperature of the core is 31℃~33℃; the phase transition temperature of the inner shell is 28℃~30℃; and the phase transition temperature of the outer shell is 25℃~27℃.

[0029] It should be noted that: The core-shell structure of this application is a three-layer core-shell structure with three precise phase change temperature zones from the outside to the inside: 25℃~27℃, 28℃~30℃, and 31℃~33℃, which realizes full-range, step-by-step, and precise temperature control of the human body's thermal comfort zone in the mining environment.

[0030] In this application, the outer shell is a ternary low-temperature eutectic composite of lauric acid, n-octadecane, and hexadecyl alcohol prepared by melt blending. The inner shell is a ternary low-temperature eutectic composite of myristic acid, n-nonadecane, and octadecyl alcohol prepared by melt blending. The core is a ternary low-temperature eutectic composite of palmitic acid, n-eicosane, and octadecyl alcohol prepared by melt blending.

[0031] It should be noted that: like Figure 1 and Figure 2 As shown, the core 1, inner shell 2, and outer shell 3 in this application are ternary cryogenic eutectic composites with three precisely progressive phase change temperatures. Utilizing the hydrogen bonds and van der Waals force network formed between fatty acids, alkanes, and fatty alcohols, the eutectic temperature is precisely controlled, providing a chemical basis for graded temperature control. Subsequently, through a stepwise self-assembly process from the inside out, these three composites are constructed into a core-shell structure 5, consisting of a core, inner shell, and outer shell, providing a physical guarantee for achieving sequential phase change. Finally, the entire core-shell structure 5 is loaded onto a macroscopic graphite-based porous heat-conducting carrier 4, utilizing the three-dimensional heat-conducting network and capillary constraint effect constructed by the latter to simultaneously overcome the challenges of heat conduction and leakage prevention. These three layers of design are interconnected and indispensable, jointly achieving precise, long-term, and stable control of individual mine thermal management. This achieves a cold-storing phase change core-shell composite material formed through precise control of the materials in each structural layer within the core-shell structure, combined with a multi-layered physical construction method for each structural layer.

[0032] In this application, the porosity of the porous thermally conductive matrix is ​​80%~95%, and the mass of the porous thermally conductive matrix accounts for 50%~75% of the total mass of the phase change core-shell composite material; The porous thermally conductive substrate is a graphite-based porous material.

[0033] According to another embodiment of this application, a method for preparing a cold-storage phase change core-shell composite material is provided, the method comprising the following steps: S1, Preparation of pore-matched phase change core-shell materials with graphite-based porous materials; S2, the phase change core-shell material prepared in S1 is mixed with activated graphite-based porous material at a mass ratio of 1:2 to 1:3 to obtain a mixture; S3, the mixture is placed in a vacuum environment of 60℃~80℃, so that the core and shell materials melt and penetrate and are uniformly loaded into the macropores of the graphite-based porous carrier; S4. The final product of S3 is cooled to room temperature to obtain the final cold storage phase change core-shell composite material.

[0034] In this application, the method for preparing the phase change core-shell material includes: S101, respectively prepare outer shell material, inner shell material and core material; S102, the outer shell, inner shell and core materials prepared by S101 are crushed and passed through an 80-100 mesh sieve to obtain corresponding particles so that the particle size after blending matches the pore size of the graphite-based porous material. S103, for the self-assembly of phase change core-shell materials, specifically includes: ① The inner shell material is melted at a temperature T1, wherein the temperature T1 is 5°C to 10°C higher than the phase transformation temperature of the inner shell material; ② Add solid composite phase change core material particles to the molten inner shell material and stir at a speed of 200 r / min to 400 r / min for 0.5 h to 1 h to form a primary core-shell structure consisting of a core and an inner shell. After cooling, pulverize to a particle size of 50 μm to 100 μm. ③ Melt the outer shell material at a temperature T2, wherein the temperature T2 is 5°C to 10°C higher than the phase transition temperature of the outer shell material; ④ Add the primary core-shell structure particles obtained in step ② to the molten outer shell material, and stir at a speed of 200 r / min to 400 r / min for 1 h to 2 h to form a triple core-shell structure consisting of a core material, an inner shell, and an outer shell; after cooling, a phase change core-shell material is obtained.

[0035] It should be noted that: In this application, a core-shell encapsulation from the inside out encapsulates the solid core and low-melting-point inner shell, providing a physical barrier that restricts the flow of molten material to a certain extent. The porous thermally conductive matrix, serving as the carrier, is filled with micron- and nano-scale pores. When the phase change material melts, these pores generate strong capillary forces, firmly adsorbing the liquid within them. Simultaneously, the pore walls constitute a robust physical spatial constraint, effectively preventing macroscopic migration and leakage of the liquid phase material.

[0036] This dual mechanism together ensures the integrity of the material's morphology during repeated phase transitions, preventing functional degradation caused by the loss of phase change material, thus guaranteeing a long service life.

[0037] Furthermore, the inside-out encapsulation strategy, which involves first forming a primary core-shell structure with a core and an inner shell, and then encapsulating the primary core-shell structure with an outer shell, reduces the complexity of a single reaction, improves the uniformity of each encapsulation and the strength of the interfacial bonding, and makes large-scale production possible.

[0038] The step-by-step self-assembly process described above avoids common problems in the fabrication of complex core-shell structures, such as interface peeling and uneven coating. The final product is a solid block that can be directly cut and integrated into the interlayer of protective clothing, making it easy to apply.

[0039] In this application, the shell material is prepared by weighing lauric acid, n-octadecane and hexadecyl alcohol in a mass ratio of 1:(0.5~1.5):(0.2~0.8), melting them at 60℃~65℃ under nitrogen protection, mechanically stirring at a speed of 400r / min~500r / min for 1 hour~1.5 hours, and then cooling and solidifying to obtain the shell material; The inner shell material is prepared as follows: myristic acid, n-nonadecane and octadecyl alcohol are weighed in a mass ratio of 1:(0.8~1.8):(0.3~0.7), melted at 65℃~70℃ under nitrogen protection, and mechanically stirred at a speed of 400r / min~500r / min for 1 hour~1.5 hours, and then cooled and solidified to obtain the inner shell material; The core material is prepared by weighing palmitic acid, n-eicosane and octadecyl alcohol in a mass ratio of 1:(0.6~1.2):(0.1~0.4), melting them at 70℃~75℃ under nitrogen protection, and mechanically stirring them at a speed of 400r / min~500r / min for 1 hour~1.5 hours, followed by cooling and solidification to obtain the core material.

[0040] According to another embodiment of this application, an application of a cold-storage phase change core-shell composite material is provided, wherein the phase change core-shell composite material is used in protective clothing materials for high-temperature mines; As attached Figure 3 As shown, the phase change core-shell composite material 4 is cut or molded into the required shape and integrated into the interlayer of the mining protective clothing.

[0041] The present invention will be further illustrated by the following examples, but the scope of protection of the present invention is not limited thereto.

[0042] Example 1 1. Preparation of core-shell composite materials for cold storage phase change: S1, respectively prepare the outer shell material, inner shell material, and core material: Preparation of the outer shell material: 10.0 g of lauric acid, 10.0 g of n-octadecane, and 5.0 g of hexadecyl alcohol were weighed and placed in a reaction vessel. Under N2 atmosphere protection, the mixture was melted at 62℃ and mechanically stirred at 450 rpm for 1.2 h. Then, it was removed, cooled to room temperature and solidified. After being pulverized by a pulverizer, it was passed through a 100-mesh sieve to obtain the outer shell material powder.

[0043] Preparation of the inner shell material: Weigh 10.0 g of myristic acid, 12.0 g of n-nonadecane, and 5.0 g of octadecyl alcohol, and place them in a reaction vessel. Melt and stir at 450 rpm for 1.2 h under N2 atmosphere at 68℃. Cool to room temperature to solidify, pulverize and pass through a 100-mesh sieve to obtain the inner shell material powder.

[0044] Preparation of core material: Weigh 10.0 g of palmitic acid, 9.0 g of n-eicosane and 2.5 g of octadecyl alcohol, place them in a reaction vessel, and melt and stir at 450 rpm for 1.2 h under N2 atmosphere protection at 73℃. After cooling to room temperature and solidification, pulverize and pass through a 100-mesh sieve to obtain core material powder.

[0045] 2. Core-shell structure self-assembly: ① Weigh 20.0 g of inner shell material powder and melt it at 35℃; then add 4.0 g of core material powder and stir at 300 r / min for 45 minutes to fully coat the core particles with the inner shell material. After cooling, crush the particles to obtain primary core-shell particles with a particle size of about 80 μm.

[0046] ② Weigh 16.0 g of shell material powder, melt it at 32℃, add all the primary core-shell particles obtained in ①, stir at 300 r / min for 1.5 hours to ensure uniform shell coating, and after cooling, obtain a phase change core-shell material with a total mass of about 40 g with a triple core-shell structure.

[0047] 3. Porous matrix supported composite: 100.0 g of expanded graphite plate with a porosity of 85% was calcined at 120°C in a nitrogen atmosphere for 2.5 hours, then soaked in 1.5 wt% KH-550 ethanol solution for 1.5 hours and dried for activation.

[0048] 40.0 g of phase change core-shell material was thoroughly mixed with 100 g of activated expanded graphite plate to obtain a mixture; The mixture was placed in a vacuum drying oven at 70°C for 5 hours to allow the phase change core-shell material to melt and fully penetrate into the pores of the graphite plate through capillary action.

[0049] The heating was then turned off and the mixture was cooled to room temperature to obtain the final blocky cold storage phase change core-shell composite material.

[0050] 4. Performance Testing and Results: Phase transition characteristics: The phase transition core-shell composite material prepared in this embodiment exhibits three distinct phase transition stages within the temperature range of 25℃ to 33℃, corresponding to the design phase transition temperatures of the outer layer, inner layer, and core material, respectively. The total latent heat of phase transition is 185 J / g. The composite material shows three distinct endothermic peaks within the 25℃ to 33℃ range, with peak temperatures at 26.2℃, 29.1℃, and 32.0℃, respectively, consistent with the design temperature range. The calculated total latent heat of phase transition is 185 J / g.

[0051] Thermal conductivity: The thermal conductivity was measured to be 2.1 W / (m·K) using a laser thermal conductivity meter (LFA 467).

[0052] Leakage resistance: After placing the sample in an 80℃ constant temperature oven for 5 hours, no leakage was observed. Subsequently, 200 accelerated thermal cycling tests were conducted at 25℃ to 50℃, and the latent heat retention rate reached 96.5%.

[0053] The test results above verify that the core-shell structure formed by the stepwise self-assembly process in this application successfully constructed three independent phase transition temperature zones with minimal interference between them. The high thermal conductivity and excellent leak-proof performance further validate the successful application of macroscopic graphite-based porous carriers as an integral thermally conductive framework and physically constrained matrix, with effects far superior to physical mixing.

[0054] Example 2 1. Preparation of core-shell composite materials for cold storage phase change: This embodiment aims to investigate the effect of different raw material ratios on the performance of porous matrices.

[0055] Phase change material preparation: Shell material: Lauric acid, n-octadecane and hexadecyl alcohol are weighed in a mass ratio of 1:0.8:0.6, melt-blended at 61℃ under N2 protection for 1.5 h, cooled, crushed and passed through a 100-mesh sieve.

[0056] Inner shell material: Myristic acid, n-nonadecane and octadecyl alcohol are weighed in a mass ratio of 1:1.5:0.4 and treated at 67°C using the same method as the outer shell material.

[0057] Core material: Palmitic acid, n-eicosane and octadecyl alcohol are weighed in a mass ratio of 1:1:0.2 and treated at 72°C using the same method as the outer shell material.

[0058] 2. Core-shell structure self-assembly: The self-assembly process is the same as in Example 1. The inner shell melting temperature (T1) is 34°C, and the outer shell melting temperature (T2) is 31°C.

[0059] In phase change core-shell materials, the mass ratio of the outer shell, inner shell, and core is 35:55:10.

[0060] 3. Porous matrix supported composite: Graphene foam with a porosity of approximately 90% was used as a porous thermally conductive matrix, and the activation conditions were the same as in Example 1.

[0061] Phase change core-shell material and graphene foam were mixed at a mass ratio of 1:2 and impregnated at 65°C under vacuum for 4 h. After cooling, phase change core-shell composite material was obtained.

[0062] 4. Performance Testing and Results Phase transition characteristics: The phase transition core-shell composite material prepared in this embodiment exhibits three phase transition stages in the range of 25℃~33℃, with a total latent heat of phase transition of 192 J / g, and the phase transition temperature is consistent with the design range.

[0063] Thermal conductivity: The measured thermal conductivity is 1.9 W / (m·K).

[0064] Leakage resistance: Passed the 80℃ leak prevention test, and the latent heat retention rate is >95% after 200 thermal cycles.

[0065] Comparative Example To verify the advantages of the core-shell structure and stepwise self-assembly process of this invention, a comparative example is set up.

[0066] 1. Raw Materials and Preparation The same types and proportions of raw materials as in Example 1 were used.

[0067] The prepared outer shell, inner shell, and core material powders are directly physically mixed without going through the core-shell self-assembly step. Instead, the composite phase change material particles of the outer layer, inner layer, and core material are simply physically mixed with expanded graphite.

[0068] 2. Performance Testing and Results Phase transition characteristics: The DSC curve shows a broad endothermic peak, the phase transition temperature ranges overlap, and it is impossible to distinguish three independent phase transition plateaus, indicating chaotic phase transition behavior.

[0069] Thermal conductivity: The measured thermal conductivity was 1.3 W / (m·K), which was significantly lower than that of Example 1.

[0070] Leakage prevention: After being placed in an 80 ℃ oven for only 2 hours, obvious oily phase change material was observed to seep out from the composite material, indicating that the leakage prevention performance failed.

[0071] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

[0072] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A cold-storage phase change core-shell composite material, characterized in that, The core-shell composite material includes a porous thermally conductive matrix and a core-shell structure loaded in the pores of the porous thermally conductive matrix; The core-shell structure is a three-layered stepped phase change core-shell structure with increasing phase change temperature from the outside to the inside. The core-shell structure includes a core, an inner shell, and an outer shell. The core and the inner shell are solid, and the outer shell is solid before a phase change occurs, and becomes molten after absorbing heat and undergoing a phase change. The porous thermally conductive substrate realizes the thermal conductivity of the core-shell structure through its own three-dimensional thermally conductive network. The micro-nano pores of the porous thermally conductive substrate provide strong capillary forces and physical space constraints for the loaded core-shell structure, preventing physical leakage of the core-shell structure.

2. The cold storage phase change core-shell composite material according to claim 1, characterized in that, The core-shell composite material has an overall latent heat of phase change ≥180 J / g and a thermal conductivity ≥1.8 W / (m·K).

3. The cold storage phase change core-shell composite material according to claim 1, characterized in that, The phase transition temperatures of the core, the inner shell, and the outer shell decrease in a stepwise manner. The core, the inner shell, and the outer shell sequentially enclose each other from the inside out, forming a phase transition temperature that increases progressively. Ternary low-temperature eutectic composite.

4. The cold storage phase change core-shell composite material according to claim 1, characterized in that, The core has a deformation temperature of 31℃~33℃; the inner shell has a phase transition temperature of 28℃~30℃; and the outer shell has a phase transition temperature of 25℃~27℃.

5. The cold storage phase change core-shell composite material according to claim 1, characterized in that, The outer shell is a ternary low-temperature eutectic composite of lauric acid, n-octadecane, and hexadecyl alcohol prepared by melt blending. The inner shell is a ternary low-temperature eutectic composite of myristic acid, n-nonadecane, and octadecyl alcohol prepared by melt blending. The core is a ternary low-temperature eutectic composite of palmitic acid, n-eicosane, and octadecyl alcohol prepared by melt blending.

6. The cold storage phase change core-shell composite material according to claim 1, wherein the porosity of the porous thermally conductive matrix is ​​80%~95%, and the mass of the porous thermally conductive matrix accounts for 50%~75% of the total mass of the phase change core-shell composite material; The porous thermally conductive substrate is a graphite-based porous material.

7. A method for preparing a cold-storage phase change core-shell composite material, characterized in that, The preparation method is used to prepare a cold storage phase change core-shell composite material according to any one of claims 1 to 6, and the preparation method includes the following steps: S1, Preparation of pore-matched phase change core-shell materials with graphite-based porous materials; S2, the phase change core-shell material prepared in S1 is mixed with activated graphite-based porous material at a mass ratio of 1:2 to 1:3 to obtain a mixture; S3, the mixture is placed in a vacuum environment of 60℃~80℃, so that the core and shell materials melt and penetrate and are uniformly loaded into the macropores of the graphite-based porous carrier; S4. The final product of S3 is cooled to room temperature to obtain the final cold storage phase change core-shell composite material.

8. The method for preparing a cold storage phase change core-shell composite material according to claim 7, characterized in that, The preparation method of the phase change core-shell material includes: S101, respectively prepare outer shell material, inner shell material and core material; S102, the outer shell, inner shell and core materials prepared by S101 are crushed and passed through an 80-100 mesh sieve to obtain corresponding particles so that the particle size after blending matches the pore size of the graphite-based porous material. S103, for the self-assembly of phase change core-shell materials, specifically includes: ① The inner shell material is melted at a temperature T1, wherein the temperature T1 is 5°C to 10°C higher than the phase transformation temperature of the inner shell material; ② Add solid composite phase change core material particles to the molten inner shell material and stir at a speed of 200 r / min to 400 r / min for 0.5 h to 1 h to form a primary core-shell structure consisting of a core and an inner shell. After cooling, pulverize to a particle size of 50 μm to 100 μm. ③ Melt the outer shell material at a temperature T2, wherein the temperature T2 is 5°C to 10°C higher than the phase transition temperature of the outer shell material; ④ Add the primary core-shell structure particles obtained in step ② to the molten outer shell material, and stir at a speed of 200 r / min to 400 r / min for 1 h to 2 h to form a triple core-shell structure consisting of a core material, an inner shell, and an outer shell; after cooling, a phase change core-shell material is obtained.

9. The method for preparing a cold-storage phase change core-shell composite material according to claim 7, characterized in that, The outer shell material is prepared by weighing lauric acid, n-octadecane and hexadecyl alcohol in a mass ratio of 1:(0.5~1.5):(0.2~0.8), melting them at 60℃~65℃ under nitrogen protection, and mechanically stirring them at a speed of 400r / min~500r / min for 1 hour~1.5 hours, followed by cooling and solidification to obtain the outer shell material. The inner shell material is prepared as follows: myristic acid, n-nonadecane and octadecyl alcohol are weighed in a mass ratio of 1:(0.8~1.8):(0.3~0.7), melted at 65℃~70℃ under nitrogen protection, and mechanically stirred at a speed of 400r / min~500r / min for 1 hour~1.5 hours, and then cooled and solidified to obtain the inner shell material; The core material is prepared by weighing palmitic acid, n-eicosane and octadecyl alcohol in a mass ratio of 1:(0.6~1.2):(0.1~0.4), melting them at 70℃~75℃ under nitrogen protection, and mechanically stirring them at a speed of 400r / min~500r / min for 1 hour~1.5 hours, followed by cooling and solidification to obtain the core material.

10. An application of a cold storage phase change core-shell composite material, characterized in that, The phase change core-shell composite material prepared by the method for preparing a cold storage phase change composite material according to claim 7 is applied to the protective clothing material in high-temperature mines; The phase change core-shell composite material is cut or molded into the required shape and integrated into the interlayer of the mining protective clothing.

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