Phonon-bridging step heat storage material, preparation method and application

Abstract

The present application relates to the technical field of energy storage material preparation, and particularly relates to a phonon bridging type step heat storage material, a preparation method and application, and provides a phonon bridging type step heat storage material, which comprises, from an outer layer to an inner layer, a phonon bridging network, a high-temperature layer, a medium-temperature layer and a low-temperature layer; the high-temperature layer, the medium-temperature layer and the low-temperature layer are all prepared from phase change materials, and the melting points of the phase change materials are arranged in a stepwise descending manner from the high-temperature layer to the low-temperature layer; the phonon bridging network comprises a biomimetic mineralized skeleton and a network structure of pore connection formed by boron nitride nanosheet-coated silicon carbide whiskers grown in the pores inside the biomimetic mineralized skeleton. The above-mentioned phonon bridging network serves as an outer layer low-scattering heat channel in combination with the construction of a multi-stage heat storage barrier, and solves the problems of low heat energy storage and release efficiency and poor temperature range adaptability in the prior art.

Description

Technical Field

[0001] This invention relates to the field of energy storage material preparation technology, specifically to a phonon-bridged stepped thermal storage material, its preparation method, and its application. Background Technology

[0002] In the context of profound changes in the global energy landscape, the efficient utilization and storage of energy have become key factors driving technological progress and industrial upgrading across various sectors. With the rapid development of technology, various electronic devices are constantly moving towards miniaturization, integration, and intelligence. Wearable devices, as emerging consumer electronics, are rapidly penetrating people's daily lives with their convenience and personalization. From smartwatches and health monitoring bracelets to virtual reality glasses, their functions are becoming increasingly rich, placing more stringent demands on the stability and efficiency of energy supply. At the same time, the booming electric vehicle industry and the widespread application of large-scale energy storage systems have made battery thermal control technology a core element in ensuring safe operation and extending the lifespan of equipment. In the construction sector, with the continuous improvement of people's demands for living comfort and the energy challenges brought about by global warming, the importance of building energy-saving technologies is becoming increasingly prominent. How to achieve efficient storage and rational release of heat energy inside buildings to reduce energy consumption and carbon emissions has become a critical issue that the construction industry urgently needs to address.

[0003] Phase change materials (PCMs) are a class of functional materials capable of absorbing or releasing large amounts of latent heat through phase changes (such as solid-liquid, solid-solid, liquid-gas, etc.) during temperature changes. Their core characteristic lies in maintaining a nearly constant temperature during the phase change process, while simultaneously achieving efficient energy storage and release, earning them the reputation of "intelligent heat managers." For example, Chinese invention patent CN119931239B discloses a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure and its preparation method. This technology provides a confined encapsulation space for alcohol-based phase change materials by constructing a gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier. This unique structural design allows the phase change material to exist more stably in the composite film and effectively achieves heat storage and release during the phase change process, thereby realizing gradient heat transfer and synergistic management, and improving heat utilization efficiency. Although this technology has shown synergistic performance in efficient heat storage and release in wearable devices, battery thermal control, and building energy conservation, there is still considerable room for improvement in terms of heat storage density, thermal conductivity, and cycle stability. Chinese invention patent CN120018396B discloses a method for laminating and preparing a high thermal conductivity circuit board. The method involves dispersing and solidifying a mixture of liquid gallium-indium alloy and fibers in an inert argon atmosphere, then fusing it with a substrate to obtain an adaptive thermally conductive substrate. This substrate is then subjected to gradient deposition and etching to obtain a gradient-spacing template. Finally, the template is electrospun and heat-treated, followed by pre-pressing of the conductive layer to obtain the formed circuit board. While this technology addresses issues such as poor heat flow paths and interfacial bonding, thus improving thermal management to some extent, it does not address the synergistic performance of heat storage and release, and it does not consider the gradient arrangement of phase change materials. This fails to fully leverage the advantages of phase change materials in thermal management, limiting their application across a wider temperature range. Summary of the Invention

[0004] To address the problems of low thermal energy storage and release efficiency and poor temperature range adaptability of existing thermal storage materials, this invention provides a phonon-bridged stepped thermal storage material, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a phonon-bridged stepped thermal storage material, comprising a phonon bridging network, a high-temperature layer, a medium-temperature layer, and a low-temperature layer arranged sequentially from the outer layer to the inner layer; The high-temperature layer, the medium-temperature layer, and the low-temperature layer are all made of phase change materials, and the melting points of the phase change materials are arranged in a stepwise manner from the high-temperature layer to the low-temperature layer. The phonon bridging network comprises a biomimetic mineralized framework and a network structure consisting of silicon carbide whiskers coated with boron nitride nanosheets grown inside the pores of the biomimetic mineralized framework, forming a pore-connected network structure.

[0006] Preferably, the high-temperature layer is made of a metal alloy with a heat storage temperature of 80°C or higher; the medium-temperature layer is made of an organic acid or its salt with a melting point of 40-60°C; and the low-temperature layer is made of an inorganic hydrate, wherein the number of water molecules in the inorganic hydrate is Ten≥4.

[0007] Preferably, the thickness of the phonon bridging network is 30-50 μm, the thickness of the high-temperature layer is 25-30 μm, the thickness of the medium-temperature layer is 30-35 μm, and the thickness of the low-temperature layer is 30-40 μm.

[0008] The present invention also provides a method for preparing the phonon-bridged stepped thermal storage material as described above, comprising: A biomimetic mineralized framework was prepared using fly ash and steel slag; Phonon bridging networks were fabricated using a biomimetic mineralized framework, silicon carbide whiskers, and boron nitride nanosheets. A high-temperature layer, a medium-temperature layer, and a low-temperature layer are sequentially prepared inside the phonon bridging network and then calcined to strengthen them, thereby obtaining a phonon-bridging stepped thermal storage material.

[0009] Preferably, the method for preparing a biomimetic mineralized framework using fly ash and steel slag is as follows: Fly ash and steel slag are mixed and ground to obtain mixed solid waste; Hydrogen peroxide is added to the mixed solid waste, and the mixture is heated to foam and form a through-type skeleton. The through-framework was sintered and strengthened to obtain a biomimetic mineralized framework.

[0010] Preferably, the mass ratio of fly ash to steel slag in the mixed solid waste is (6:4)-(7:3); the amount of hydrogen peroxide added is 8%-12% of the mass of the mixed solid waste; the method of adding hydrogen peroxide to the mixed solid waste, heating and foaming to form a through skeleton is as follows: heating to 600-650℃ at 5℃ / min, holding for 30-45min, then heating to 900-950℃ at 10℃ / min, holding for 1-2h, forming a through skeleton with a porosity of 90%-95% and an average pore size of 200-400μm; the sintering strengthening method is as follows: using laser selective sintering process to sinter and strengthen the through skeleton, with a laser power of 80-120W and a scanning speed of 50-100 mm / s.

[0011] Preferably, the method for preparing a phonon bridging network using a biomimetic mineralized framework, silicon carbide whiskers, and boron nitride nanosheets is as follows: A sol was prepared using sodium triacetate, silicon carbide whiskers, boron nitride nanosheets, and ethanol. After impregnating the biomimetic mineralized framework with sol, it is sintered at high temperature under inert gas conditions to obtain a phonon bridging network.

[0012] Preferably, the concentration of sodium nitrilotriacetate in the sol is 1.5wt%-2.5wt%, the concentration of boron nitride nanosheets is 0.3wt%-0.6wt%, and the mass ratio of boron nitride nanosheets to silicon carbide whiskers is (3:1)-(4:1); the conditions for high-temperature sintering under inert gas conditions are: the inert gas is argon and hydrogen with a volume ratio of 9:1, the inert gas flow rate is 5-10 L / min, the temperature is 1000-1100℃, and the holding time is 2-3 h.

[0013] Preferably, the high-temperature layer, the medium-temperature layer and the low-temperature layer are all assisted in shaping using laser selective melting technology, and the calcination strengthening temperature is 300-520℃.

[0014] The above-mentioned phonon-bridged stepped thermal storage materials are used in electronic equipment, battery thermal control, or building energy conservation.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a phonon-bridged stepped thermal storage material, comprising a phonon bridging network, a high-temperature layer, a medium-temperature layer, and a low-temperature layer arranged sequentially from the outermost layer to the innermost layer. The high-temperature layer, medium-temperature layer, and low-temperature layer are all made of phase change materials, and the melting points of the phase change materials are arranged in a stepped manner from the high-temperature layer to the low-temperature layer. The phonon bridging network, as the outer layer structure, rationally arranges silicon carbide whiskers with high thermal conductivity within the mineralized framework, forming an effective phonon bridging network structure. This significantly shortens the phonon transmission distance and reduces the phonon scattering area, thereby improving the heat storage and release rate and efficiency of the mineralized framework. The frame-like porous network structure greatly improves the internal heat transfer performance while providing more deposition space for the phase change material. It significantly increases the diffusion rate constant of the phase change material by increasing capillary attraction to promote material rearrangement, and the low-scattering thermal channels constructed by the oriented nanomaterials significantly reduce contact thermal resistance. By employing high-temperature, medium-temperature, and low-temperature layers, a multi-level thermal storage barrier is formed. This allows the high-temperature layer to preferentially absorb high-intensity heat flux, with the medium-temperature and low-temperature layers responding sequentially. This avoids performance degradation of a single phase change material due to heat flux overload, fully utilizing the latent heat and thermal conductivity of each phase change material while overcoming the limitations of single phase change materials in intelligently controlling heat release time. Through the complementary performance of the combination of phonon bridging networks and multi-level stepped phase change materials, the overall heat transfer performance and phase change heat release capacity of the thermal storage material are improved, optimizing the overall thermal storage density and cycle stability, thereby enhancing temperature range adaptability. This overcomes the limitations of traditional thermal storage materials in terms of heat transfer efficiency, thermal storage density, cycle stability, and temperature range adaptability, providing a high-performance, high-reliability solution for fields such as electronic heat dissipation, renewable energy, and aerospace, demonstrating significant technical and economic value and broad market prospects.

[0016] This invention also provides a method for preparing the aforementioned phonon-bridged stepped thermal storage material. This method involves preparing a biomimetic mineralized framework using fly ash and steel slag; preparing a phonon bridging network using the biomimetic mineralized framework, silicon carbide whiskers, and boron nitride nanosheets; and sequentially preparing a high-temperature layer, a medium-temperature layer, and a low-temperature layer within the phonon bridging network, followed by calcination for strengthening, thus obtaining the phonon-bridged stepped thermal storage material. The use of fly ash and steel slag to prepare the biomimetic mineralized framework not only improves the heat transfer performance of the structure by creating a porous, interconnected network framework, thus realizing the resource utilization of industrial solid waste, but also leverages the dual constraint effect of the hollow channels in the steel slag and fly ash, increasing the specific surface area and providing space for the fixation of the phase change material and the interchange of positions during the phase change process. This method utilizes the synergistic use of fly ash and steel slag, the composite design of a biomimetic mineralized framework and a phonon bridging network, and the integration of multi-level stepped phase change materials. By combining the phonon bridging network with multi-level stepped phase change materials, it overcomes the limitations of traditional thermal storage materials in terms of heat transfer efficiency, thermal storage density, cycle stability, and temperature range adaptability. The method is simple, reliable, easy to operate, low in cost, and low in energy consumption, making it suitable for large-scale production and application.

[0017] The phonon-bridged stepped thermal storage material of this invention achieves a synergistic breakthrough in efficient heat dissipation, safety assurance, and energy saving in the fields of electronic equipment, battery thermal control, and building energy conservation through multi-level temperature range design, phonon bridging thermal conduction enhancement, and high-value utilization of industrial solid waste. Its technical performance is significantly better than that of traditional materials, and it has advantages such as low cost, environmental compliance, and large scale potential. It can be widely used in strategic emerging industries such as 5G communication, new energy vehicles, and zero-carbon buildings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a phonon-bridged stepped thermal storage material according to the present invention.

[0019] Figure 2 The flowchart S1 shows a method for preparing a phonon-bridged stepped thermal storage material according to the present invention.

[0020] Figure 3 The above is a flowchart of S2, which shows the preparation method of a phonon-bridged stepped thermal storage material according to the present invention.

[0021] Figure 4 The above is a flowchart (S3) of a method for preparing a phonon-bridged stepped thermal storage material according to the present invention.

[0022] Among them, 1-phonon bridging network, 2-high temperature layer, 3-intermediate temperature layer, 4-low temperature layer, 5-biomimetic mineralization framework, 6-silicon carbide whiskers coated with boron nitride nanosheets. Detailed Implementation To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0024] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0025] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0026] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0029] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0030] See Figure 1 The present invention discloses a phonon-bridged stepped thermal storage material, comprising a phonon bridging network 1, a high-temperature layer 2, a medium-temperature layer 3 and a low-temperature layer 4 arranged sequentially from the outer layer to the inner layer; The phonon bridging network 1 is the first layer from the outer layer to the inner layer, with a thickness of 30-50 μm. It includes a biomimetic mineralized framework 5 and a network structure composed of boron nitride nanosheets coated with silicon carbide whiskers 6 grown inside the pores of the biomimetic mineralized framework 5. The biomimetic mineralized framework 5 is an important component of the phonon bridging network and is a porous interconnected framework structure prepared from fly ash and steel slag. The boron nitride nanosheets coated with silicon carbide whiskers 6 grow inside the pores of the biomimetic mineralized framework 5 and constitute the thermally conductive enhancing component of the phonon bridging network. The high-temperature layer 2, the medium-temperature layer 3, and the low-temperature layer 4 are all made of phase change materials, and the melting points of the phase change materials are arranged in a stepwise manner from the high-temperature layer 2 to the low-temperature layer 4. Preferably, the high-temperature layer 2 is the second layer from the outer layer to the inner layer, with a thickness of 25-30 μm, and is made of a metal alloy phase change material with a heat storage temperature of 80°C or higher; The intermediate temperature layer 3 is the third layer from the outer layer to the inner layer, with a thickness of 30-35 μm, and is prepared from organic acid or its salt phase change material with a melting point of 40-60℃; The low-temperature layer 4 is the fourth layer from the outer layer to the inner layer, with a thickness of 30-40 μm. It is made of inorganic hydrate phase change material and has a water of crystallization number Ten≥4.

[0031] See Figures 2 to 4 The present invention also provides a method for preparing the phonon-bridged stepped thermal storage material as described above, comprising: S1: A biomimetic mineralized framework 5 was prepared using fly ash and steel slag. (See [reference]) Figure 2 Specifically: Fly ash and steel slag are mixed and ground to obtain mixed solid waste; fly ash and steel slag are the main raw materials for preparing biomimetic mineralized skeleton 5. The mass ratio of fly ash to steel slag is (6:4)-(7:3). They are placed in a mixer and ground to a fineness of 200-400 mesh. Hydrogen peroxide is added to mixed solid waste, and the mixture is heated to foam and form a through-type skeleton. Hydrogen peroxide is used as a foaming agent, and the amount of hydrogen peroxide added is 8%-12% of the mass of the mixed solid waste. During the programmed heating process, hydrogen peroxide decomposes to generate gas and form a porous structure. Specifically, the temperature is increased to 600-650℃ at 5℃ / min, held for 30-45min, and then increased to 900-950℃ at 10℃ / min, held for 1-2h, to form a through-type skeleton with a porosity of 90%-95% and an average pore size of 200-400μm. The through-framework is sintered and strengthened to obtain a biomimetic mineralized framework 5. The sintering and strengthening method is as follows: the through-framework is sintered and strengthened using a laser selective sintering process with a laser power of 80-120W and a scanning speed of 50-100 mm / s. The porous through-framework 5 obtained after foaming and laser selective sintering has a porosity of 90%-95% and an average pore size of 200-400μm, and serves as the substrate for subsequent processes.

[0032] S2: Phonon bridging network 1 was prepared using a biomimetic mineralized framework 5, silicon carbide whiskers, and boron nitride nanosheets. (See [link to documentation]). Figure 3 Specifically: A sol was prepared using sodium triacetate, silicon carbide whiskers, boron nitride nanosheets, and ethanol. After impregnating the biomimetic mineralized framework 5 with sol, it was sintered at high temperature under inert gas conditions to obtain the phonon bridging network 1. The phonon bridging network 1 is the final structure formed after high-temperature sintering. The silicon carbide whiskers 6 coated with boron nitride nanosheets grow in situ inside the pores of the biomimetic mineralized framework 5 and are interconnected to form a highly thermally conductive pore network with a coverage of ≥95%. The concentration of sodium nitrilotriacetate in the sol is 0.8wt%-2.5wt%, the concentration of boron nitride nanosheets is 0.3wt%-0.6wt%, and the mass ratio of silicon carbide whiskers to boron nitride nanosheets is (3:1)-(4:1). The conditions for high-temperature sintering under inert gas conditions are: the inert gas is argon and hydrogen with a volume ratio of 9:1, the inert gas flow rate is 5-10 L / min, the temperature is 1000-1100℃, and the holding time is 2-3 h, so that the silicon carbide whiskers 6 coated with boron nitride nanosheets grow in situ within the pores of the framework.

[0033] S3: A high-temperature layer 2, a medium-temperature layer 3, and a low-temperature layer 4 are sequentially prepared inside the phonon bridging network 1 and then calcined to strengthen them, resulting in a phonon-bridged stepped thermal storage material. (See [link]). Figure 4 Specifically: The phase change materials corresponding to the high-temperature layer 2, the medium-temperature layer 3, and the low-temperature layer 4 are respectively slurried and coated inside the phonon bridging network 1. Laser selective melting technology is used for laser-assisted shaping, followed by calcination at 300-520℃ to obtain a phonon-bridged stepped thermal storage material. Preferably, the near-infrared laser power of the laser selective melting is 50-80W (higher value for the high-temperature layer 2), the scanning speed is 100-150 mm / s, and the axial gradient thickness after shaping is: 25-30 μm for the high-temperature layer 2, 30-35 μm for the medium-temperature layer 3, and 35-40 μm for the low-temperature layer 4. The calcination strengthening method involves heating to 300℃ at a heating rate of 2℃ / min and holding for 1 hour. After removing residual solvent, the temperature is increased to 480-520℃ at a heating rate of 5℃ / min and held for 4 hours to strengthen the bonding between the framework and the phase change material, thus obtaining the phonon-bridged stepped thermal storage material. Among them, the high-temperature phase change layer coating (high-temperature layer 2 coating) is made by coating the outermost layer of the phonon bridging network 1 with a slurry of metal alloy phase change material with a heat storage temperature of 80℃ or above, with a thickness of 25-30μm.

[0034] The intermediate temperature phase change layer coating (intermediate temperature layer 3 coating) involves preparing an organic acid or its salt phase change material with a melting point of 40-60℃ into a slurry and coating it inside the high temperature layer 2 with a thickness of 30-35μm.

[0035] Low-temperature phase change layer coating (low-temperature layer 4 coating) involves preparing an inorganic hydrate phase change material (with ≥4 crystal water molecules) into a slurry and coating it onto the innermost layer with a thickness of 30-40 μm.

[0036] During laser selective melting and shaping, a near-infrared laser (power 50-80W, scanning speed 100-150mm / s) is used to selectively scan the coated stepped phase change layer to assist in material shaping and initial bonding with the interface.

[0037] Calcination strengthening involves a stepped temperature program of calcination at 300-520℃ to completely remove residual solvents and strengthen the chemical bonding between the phonon bridging network and each layer of phase change material, thereby improving the overall structural stability.

[0038] The composite thermal storage material prepared by the above process has a composite structure of an outer phonon bridging network and an inner stepped phase change layer, achieving synergy between efficient heat conduction and multi-stage thermal storage.

[0039] This method employs an axially gradient distribution of multi-stage phase change materials to prepare composite multifunctional energy storage materials. This fully utilizes the latent heat and thermal conductivity of each phase change material while overcoming the limitations of single phase change materials in intelligently controlling heat release time. A complementary strategy combining a phonon bridging network 1 structure and multi-stage phase change materials improves the heat transfer performance and phase change heat release capacity of the composite material, significantly enhancing its energy storage efficiency. Furthermore, this method rationally arranges highly thermally conductive silicon carbide whiskers within a mineralized framework to form an effective phonon bridging network 1 structure. This greatly shortens the phonon transmission distance and reduces the phonon scattering area, which is beneficial for improving the heat storage and release rate and efficiency of the mineralized framework. The use of solid waste to create a frame-like porous network structure significantly improves internal heat transfer performance. Simultaneously, the dual constraint of steel slag and hollow channels increases the specific surface area, providing space for the fixation of the phase change materials and their repositioning during phase change.

[0040] The aforementioned phonon-bridged stepped thermal storage material has applications in electronic devices, battery thermal control, and building energy conservation. This invention's phonon-bridged stepped thermal storage material, through multi-level temperature range design, phonon bridging thermal conductivity enhancement, and high-value utilization of industrial solid waste, achieves a synergistic breakthrough in efficient heat dissipation, safety assurance, and energy conservation in electronic devices, battery thermal control, and building energy conservation. Its technical performance is significantly superior to traditional materials, and it possesses advantages such as low cost, environmental compliance, and large-scale potential, making it widely applicable to strategic emerging industries such as 5G communications, new energy vehicles, and zero-carbon buildings.

[0041] Example 1 Bionic mineralized framework 5: Fly ash and steel slag (mass ratio 7:3) were ground to 200-400 mesh to obtain mixed solid waste. 10% hydrogen peroxide (by mass of the mixed solid waste) was added as a foaming agent, and the mixture was heated to 600℃ at 5℃ / min and held for 45 min. The temperature was then further increased to 900℃ at 10℃ / min and held for 1.5 h, forming a through-framework with a porosity of 96% and an average pore size of 300 μm. The through-framework was then sintered and strengthened using selective laser sintering (SLS) with a power of 100W, a scanning speed of 80 mm / s, a layer thickness of 40 μm, and argon protection to obtain bionic mineralized framework 5.

[0042] Preparation of phonon bridging network 1: 2.0 g sodium nitrilotriacetate was dissolved in 250 mL of anhydrous ethanol, 1.0 g boron nitride nanosheets and 3.5 g silicon carbide whiskers were added, and the mixture was ultrasonically dispersed at 300 W for 30 min (25 °C water bath) to obtain a homogeneous sol (sodium nitrilotriacetate concentration of approximately 1.00 wt% and boron nitride nanosheet concentration of approximately 0.40 wt%). After impregnating the biomimetic mineralized framework 5 with sol, it was placed in a tube furnace for chemical vapor infiltration. Under Ar / H2 mixed gas (Ar to H2 volume ratio 9:1, total flow rate of mixed gas 8L / min) and a low pressure of 20kPa, the temperature was increased to 800℃ at 5℃ / min, and then increased to 1050℃ at 10℃ / min and held for 2.2h. This allowed the silicon carbide whiskers 6 coated with boron nitride nanosheets to grow in situ on the inner wall of the framework pores, forming a phonon bridging network 1 (coverage ≥95%).

[0043] A high-temperature layer 2, a medium-temperature layer 3, and a low-temperature layer 4 are sequentially prepared inside the phonon bridging network 1, and then calcined to strengthen them, thereby obtaining a phonon-bridged stepped thermal storage material. High-temperature layer 2: Bismuth-indium alloy (mass ratio Bi:In=7:3), thickness 30μm; Intermediate temperature layer 3: Decanoic acid-palmitic acid eutectic (molar ratio 7:3, phase transition temperature 57℃), thickness 35μm; Low-temperature layer 4: Sodium sulfate decahydrate-SiO2 microcapsules (core-to-wall ratio 1:0.5, particle size 20–50 μm), thickness 40 μm; The phase change materials corresponding to the high temperature layer 2, the medium temperature layer 3 and the low temperature layer 4 were respectively prepared into slurries and coated into the inside of the phonon bridging network 1. The viscosity of the slurry was controlled at 500-1000 mPa·s and the coating thickness error was <±5 μm. After drying in air at 25℃ for 24h, the layer was dried in vacuum at 60℃ for 6h to obtain the stepped phase change layer.

[0044] During the process, near-infrared laser selective melting (power 75W, scanning speed 120mm / s) is used to wrap and shape the material layer by layer from the outside to the inside according to the temperature gradient.

[0045] Laser selective melting conditions: near-infrared laser power 50-80 W (higher value for high temperature layer 2), scanning speed 100-150 mm / s; The stepped phase change layer was heated to 300℃ at a heating rate of 2℃ / min and held for 1 h to remove residual solvent. Then, it was heated to 480℃ at a heating rate of 5℃ / min and held for 4 h to strengthen the bonding between the framework and the phase change material, thus obtaining a phonon-bridged stepped thermal storage material.

[0046] Using differential scanning calorimetry (DSC) and testing standards ASTM E793, ASTM E967, and ISO 11357, under nitrogen protection (flow rate 50 mL / min) and a heating rate of 10 °C / min, the latent heat of phase change of the phonon-bridged stepped thermal storage material prepared in this example was measured to be 377 kJ / kg.

[0047] The phonon-bridged stepped thermal storage material prepared in this embodiment at 80℃ was placed in a constant temperature water bath at 25℃. The temperature change at the center of the phonon-bridged stepped thermal storage material prepared in this embodiment was recorded. The latent heat release time of the phase change was measured to be about 5.5 min. Combined with the latent heat value measured by DSC, the heat release rate constant was calculated to be about 68.6 kJ / kg·min.

[0048] Testing showed that the phonon bridging network 1 improved the thermal conductivity to 2.8-3.5 W / (m·K), which is 6 times higher than that of pure phase change materials (0.2–0.5 W / (m·K)). Cyclic stability: After 200 thermal cycles (-40℃) After reaching 80℃, the heat storage capacity retention rate is >95%, and the phase change temperature drift is <±1℃.

[0049] Example 2 Bionic mineralized framework 5: Fly ash and steel slag (mass ratio 6:4) were ground to 200-400 mesh to obtain mixed solid waste. 8% (by weight) of hydrogen peroxide was added to the mixed solid waste as a foaming agent. The temperature was increased to 650℃ at 5℃ / min and held for 45 min. The temperature was then further increased to 950℃ at 10℃ / min and held for 1.5 h to form a through-framework with a porosity of 95% and an average pore size of 200 μm. The through-framework was then sintered and strengthened using selective laser sintering (SLS) with a power of 80W, a scanning speed of 50 mm / s, a layer thickness of 40 μm, and argon protection to obtain bionic mineralized framework 5.

[0050] Preparation of phonon bridging network 1: 4.0 g sodium nitrilotriacetate was dissolved in 250 mL of anhydrous ethanol, 1.0 g boron nitride nanosheets and 3 g silicon carbide whiskers were added, and the mixture was ultrasonically dispersed at 300 W for 30 min (25 °C water bath) to obtain a homogeneous sol (sodium nitrilotriacetate concentration of approximately 2.01 wt% and boron nitride nanosheet concentration of approximately 0.40 wt%). After impregnating the biomimetic mineralized framework 5 with sol, it was placed in a tube furnace for chemical vapor infiltration. Under Ar / H2 mixed gas (Ar to H2 volume ratio 9:1, total flow rate of mixed gas 5L / min) and a low pressure of 20kPa, the temperature was increased to 800℃ at 5℃ / min, and then increased to 1000℃ at 10℃ / min and held for 3h. This allowed the silicon carbide whiskers 6 coated with boron nitride nanosheets to grow in situ on the inner wall of the framework pores, forming a phonon bridging network 1 (coverage ≥95%).

[0051] A high-temperature layer 2, a medium-temperature layer 3, and a low-temperature layer 4 are sequentially prepared inside the phonon bridging network 1, and then calcined to strengthen them, thereby obtaining a phonon-bridged stepped thermal storage material. High-temperature layer 2: Bismuth-indium alloy (mass ratio Bi:In=7:3), thickness 25μm; Intermediate temperature layer 3: Decanoic acid-palmitic acid eutectic (molar ratio 7:3, phase transition temperature 57℃), thickness 35μm; Low-temperature layer 4: Sodium sulfate decahydrate-SiO2 microcapsules (core-to-wall ratio 1:0.5, particle size 20–50 μm), thickness 30 μm; The phase change materials corresponding to the high temperature layer 2, the medium temperature layer 3 and the low temperature layer 4 were respectively prepared into slurries and coated into the inside of the phonon bridging network 1. The viscosity of the slurry was controlled at 500-1000 mPa·s and the coating thickness error was <±5 μm. After drying in air at 25℃ for 24h, the layer was dried in vacuum at 60℃ for 6h to obtain the stepped phase change layer.

[0052] During the process, near-infrared laser selective melting (power 75W, scanning speed 120mm / s) is used to wrap and shape the material layer by layer from the outside to the inside according to the temperature gradient.

[0053] Laser selective melting conditions: near-infrared laser power 50-80 W (higher value for high temperature layer 2), scanning speed 100-150 mm / s; The stepped phase change layer was heated to 300℃ at a heating rate of 2℃ / min and held for 1 h to remove residual solvent. Then, it was heated to 520℃ at a heating rate of 5℃ / min and held for 4 h to strengthen the bonding between the framework and the phase change material, thus obtaining a phonon-bridged stepped thermal storage material.

[0054] Using differential scanning calorimetry (DSC) and testing standards ASTM E793, ASTM E967, and ISO 11357, under nitrogen protection (flow rate 50 mL / min) and a heating rate of 10 °C / min, the latent heat of phase change of the phonon-bridged stepped thermal storage material prepared in this example was measured to be 392 kJ / kg.

[0055] The phonon-bridged stepped thermal storage material prepared in this embodiment at 80℃ was placed in a constant temperature water bath at 25℃. The temperature change at the center of the phonon-bridged stepped thermal storage material prepared in this embodiment was recorded. The latent heat release time of the phase change was measured to be about 5.5 min. Combined with the latent heat value measured by DSC, the heat release rate constant was calculated to be about 72.4 kJ / kg·min.

[0056] Example 3 Bionic mineralized framework 5: Fly ash and steel slag (mass ratio 6:3) were ground to 200-400 mesh to obtain mixed solid waste. 12% (by weight) of hydrogen peroxide was added as a foaming agent to the mixed solid waste, and the temperature was increased to 630℃ at 5℃ / min and held for 35 min. The temperature was then further increased to 930℃ at 10℃ / min and held for 2 h, forming a through-framework with a porosity of 93% and an average pore size of 400 μm. The through-framework was then strengthened by selective laser sintering (scanning speed 100 mm / s, layer thickness 40 μm, argon protection) to obtain bionic mineralized framework 5.

[0057] Preparation of phonon bridging network 1: 5.0 g sodium nitrilotriacetate was dissolved in 250 mL of anhydrous ethanol, 1.0 g boron nitride nanosheets and 4 g silicon carbide whiskers were added, and the mixture was ultrasonically dispersed at 300 W for 30 min (25 °C water bath) to obtain a homogeneous sol (sodium nitrilotriacetate concentration of approximately 2.51 wt% and boron nitride nanosheet concentration of approximately 0.40 wt%). After impregnating the biomimetic mineralized framework 5 with sol, it was placed in a tube furnace for chemical vapor infiltration. Under Ar / H2 mixed gas (Ar to H2 volume ratio 9:1, total flow rate of mixed gas 10L / min) and a low pressure of 20kPa, the temperature was increased to 850℃ at 5℃ / min, and then increased to 1100℃ at 10℃ / min and held for 3h. This allowed the silicon carbide whiskers 6 coated with boron nitride nanosheets to grow in situ on the inner wall of the framework pores, forming a phonon bridging network 1 (coverage ≥95%).

[0058] A high-temperature layer 2, a medium-temperature layer 3, and a low-temperature layer 4 are sequentially prepared inside the phonon bridging network 1, and then calcined to strengthen them, thereby obtaining a phonon-bridged stepped thermal storage material. High-temperature layer 2: Bismuth-indium alloy (mass ratio Bi:In=7:3), thickness 28μm; Intermediate temperature layer 3: Decanoic acid-palmitic acid eutectic (molar ratio 7:3, phase transition temperature 57℃), thickness 32μm; Low-temperature layer 4: Sodium sulfate decahydrate-SiO2 microcapsules (core-to-wall ratio 1:0.5, particle size 20–50 μm), thickness 34 μm; The phase change materials corresponding to the high temperature layer 2, the medium temperature layer 3 and the low temperature layer 4 were respectively prepared into slurries and coated into the inside of the phonon bridging network 1. The viscosity of the slurry was controlled at 500-1000 mPa·s and the coating thickness error was <±5 μm. After drying in air at 25℃ for 24h, the layer was dried in vacuum at 60℃ for 6h to obtain the stepped phase change layer.

[0059] During the process, near-infrared laser selective melting (power 75W, scanning speed 120mm / s) is used to wrap and shape the material layer by layer from the outside to the inside according to the temperature gradient.

[0060] Laser selective melting conditions: near-infrared laser power 50-80 W (higher value for high temperature layer 2), scanning speed 100-150 mm / s; The stepped phase change layer was heated to 300℃ at a heating rate of 2℃ / min and held for 1 h to remove residual solvent. Then, it was heated to 500℃ at a heating rate of 5℃ / min and held for 4 h to strengthen the bonding between the framework and the phase change material, thus obtaining a phonon-bridged stepped thermal storage material.

[0061] Using differential scanning calorimetry (DSC) and testing standards ASTM E793, ASTM E967, and ISO 11357, under nitrogen protection (flow rate 50 mL / min) and a heating rate of 10 °C / min, the latent heat of phase change of the phonon-bridged stepped thermal storage material prepared in this example was measured to be 388 kJ / kg.

[0062] The phonon-bridged stepped thermal storage material prepared in this embodiment at 80℃ was placed in a constant temperature water bath at 25℃. The temperature change at the center of the phonon-bridged stepped thermal storage material prepared in this embodiment was recorded. The latent heat release time of the phase change was measured to be about 5.5 min. Combined with the latent heat value measured by DSC, the heat release rate constant was calculated to be about 70.3 kJ / kg·min.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A phonon-bridged stepped thermal storage material, characterized in that, It includes a phonon bridging network, a high-temperature layer, a medium-temperature layer, and a low-temperature layer arranged sequentially from the outermost layer to the innermost layer; The high-temperature layer, the medium-temperature layer, and the low-temperature layer are all made of phase change materials, and the melting points of the phase change materials are arranged in a stepwise manner from the high-temperature layer to the low-temperature layer. The phonon bridging network comprises a biomimetic mineralized framework and a network structure consisting of silicon carbide whiskers coated with boron nitride nanosheets grown inside the pores of the biomimetic mineralized framework, forming a pore-connected network structure.

2. The phonon-bridged stepped thermal storage material according to claim 1, characterized in that, The high-temperature layer is made of a metal alloy with a heat storage temperature of 80°C or higher; the medium-temperature layer is made of an organic acid or its salt with a melting point of 40-60°C; and the low-temperature layer is made of an inorganic hydrate with a water of crystallization number Ten≥4.

3. The phonon-bridged stepped thermal storage material according to claim 1, characterized in that, The thickness of the phonon bridging network is 30-50 μm, the thickness of the high-temperature layer is 25-30 μm, the thickness of the medium-temperature layer is 30-35 μm, and the thickness of the low-temperature layer is 30-40 μm.

4. A method for preparing a phonon-bridged stepped thermal storage material as described in any one of claims 1-3, characterized in that, include: A biomimetic mineralized framework was prepared using fly ash and steel slag; Phonon bridging networks were fabricated using a biomimetic mineralized framework, silicon carbide whiskers, and boron nitride nanosheets. A high-temperature layer, a medium-temperature layer, and a low-temperature layer are sequentially prepared inside the phonon bridging network and then calcined to strengthen them, thereby obtaining a phonon-bridging stepped thermal storage material.

5. The method for preparing the phonon-bridged stepped thermal storage material according to claim 4, characterized in that, The method for preparing a biomimetic mineralized framework using fly ash and steel slag is as follows: Fly ash and steel slag are mixed and ground to obtain mixed solid waste; Hydrogen peroxide is added to the mixed solid waste, and the mixture is heated to foam and form a through-type skeleton. The through-framework was sintered and strengthened to obtain a biomimetic mineralized framework.

6. The method for preparing the phonon-bridged stepped thermal storage material according to claim 5, characterized in that, The mass ratio of fly ash to steel slag in the mixed solid waste is (6:4)-(7:3); the amount of hydrogen peroxide added is 8%-12% of the mass of the mixed solid waste; the method of adding hydrogen peroxide to the mixed solid waste, heating and foaming to form a through skeleton is as follows: heating to 600-650℃ at 5℃ / min, holding for 30-45min, then heating to 900-950℃ at 10℃ / min, holding for 1-2h, forming a through skeleton with a porosity of 90%-95% and an average pore size of 200-400μm; the sintering strengthening method is as follows: using laser selective sintering process to sinter and strengthen the through skeleton, with a laser power of 80-120W and a scanning speed of 50-100 mm / s.

7. The method for preparing the phonon-bridged stepped thermal storage material according to claim 4, characterized in that, The method for preparing phonon bridging networks using biomimetic mineralized frameworks, silicon carbide whiskers, and boron nitride nanosheets is as follows: A sol was prepared using sodium triacetate, silicon carbide whiskers, boron nitride nanosheets, and ethanol. After impregnating the biomimetic mineralized framework with sol, it is sintered at high temperature under inert gas conditions to obtain a phonon bridging network.

8. The method for preparing the phonon-bridged stepped thermal storage material according to claim 7, characterized in that, The concentration of sodium nitrilotriacetate in the sol is 1.5wt%-2.5wt%, the concentration of boron nitride nanosheets is 0.3wt%-0.6wt%, and the mass ratio of silicon carbide whiskers coated with boron nitride nanosheets is (3:1)-(4:1). The conditions for high-temperature sintering under inert gas conditions are as follows: the inert gas is argon and hydrogen with a volume ratio of 9:1, the inert gas flow rate is 5-10 L / min, the temperature is 1000-1100℃, and the holding time is 2-3 h.

9. The method for preparing the phonon-bridged stepped thermal storage material according to claim 4, characterized in that, The high-temperature layer, medium-temperature layer and low-temperature layer are all shaped using laser selective melting technology, and the calcination strengthening temperature is 300-520℃.

10. The application of the phonon-bridged stepped thermal storage material according to any one of claims 1-3 in electronic devices, battery thermal control, or building energy conservation.

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