Preparation method for and use of polyvinyl alcohol-based double-network aerogel shaped composite phase-change energy-storage material

Abstract

The present invention belongs to the technical field of phase-change energy storage. Disclosed are a polyvinyl alcohol-based double-network aerogel shaped organic-inorganic composite phase-change energy-storage material, and a preparation method therefor and the use thereof. The phase-change energy-storage material is composed of 30-70 wt% of an inorganic solid-liquid phase-change material, 40-60 wt% of an organic solid-liquid phase-change material, 0.1-5 wt% of a nucleating agent and 5-20 wt% of a polyvinyl alcohol-based double-network aerogel supporting material, wherein the inorganic solid-liquid phase-change material is a hydrated inorganic salt phase-change material; the organic solid-liquid phase-change material is an organic nitride, an organic acid ester or a long-chain alkane phase-change material; the nucleating agent is a nano oxide or a salt having a similar crystal form; and the supporting material is a polyvinyl alcohol / double-network aerogel. The three components are assembled under a supramolecular acting force and are uniformly compounded with a porous adsorption material. The prepared composite phase-change material (CPCM) has a relatively high phase-change enthalpy value and good cycling stability. In addition, the CPCM further exhibits excellent architectural heat management performance, and is very suitable for large-scale application in architectural heat management in the future.

Description

Preparation methods and applications of polyvinyl alcohol-based dual-network aerogel-shaped composite phase change energy storage materials Technical Field

[0001] This invention relates to the preparation method and application of polyvinyl alcohol-based dual-network aerogel-shaped organic-inorganic composite phase change energy storage materials, which belongs to the field of phase change energy storage technology. Background Technology

[0002] With the continuous growth of global energy demand, building energy consumption has become a pressing issue worldwide. Statistics show that the construction industry consumes approximately 30% of the world's energy, which not only increases the pressure on energy supply but also exacerbates the risks of environmental pollution and climate change. Therefore, finding effective energy-saving solutions to reduce building energy consumption and improve energy efficiency is urgent. Among numerous energy-saving technologies, thermal energy storage technology has attracted much attention due to its ability to effectively regulate and manage thermal energy. By storing excess thermal energy when needed and releasing it when required, thermal energy storage technology allows buildings to maintain a more stable internal environment amidst temperature fluctuations, thereby reducing the frequency of use of air conditioning and heating equipment and achieving energy savings.

[0003] Among various thermal energy storage technologies, phase change materials (PCMs) exhibit significant advantages due to their unique phase change process, which allows them to absorb and release large amounts of heat. Therefore, researching the application of PCMs in buildings and developing efficient PCM composite structures has become a crucial direction for reducing building energy consumption. Among various PCMs, solid-liquid PCMs have attracted widespread attention due to their small volume change and sensitive temperature response. Solid-liquid PCMs can be classified according to their composition into organic, inorganic, and organic-inorganic composite PCMs. Organic PCMs possess advantages such as non-corrosiveness, low supercooling, and good thermal and chemical stability, but also disadvantages such as flammability and low thermal conductivity. Inorganic PCMs, on the other hand, have advantages such as high thermal conductivity and high phase change enthalpy, but suffer from high supercooling and easy phase separation. Organic-inorganic composite PCMs, combining the advantages of both organic and inorganic PCMs, have become a research hotspot in recent years. However, the application of composite PCMs in building thermal management still faces two major challenges: firstly, the liquid generated during the phase change process is prone to leakage. Secondly, the low phase transition enthalpy leads to poor utilization efficiency. In recent years, aerogels, due to their ultra-high porosity and specific surface area, have been considered ideal support materials for solving the leakage problem of PCMs (Polymerized Conversion Materials). Furthermore, the ultra-high loading rate of aerogels allows phase change materials to maintain a high phase transition enthalpy. This is because phase change materials can achieve efficient adsorption within aerogels, resulting in ultra-high energy storage density. Many researchers have combined aerogels with phase change materials and applied them to various fields such as infrared stealth, seawater desalination, and solar thermal energy capture and storage. Technical issues

[0004] Currently, many researchers have applied phase change materials (PCMs) to building thermal management. However, these studies still have some unresolved issues, such as supercooling, phase separation, or flammability. Although some researchers have attempted to address these issues by adding flame retardants, nucleating agents, and thickeners, this undoubtedly significantly reduces the phase change enthalpy of the composite PCMs. Furthermore, most PCMs used in the building industry are typically encapsulated with porous materials such as diatomaceous earth, perlite, and kaolinite to prevent leakage. However, these encapsulation materials suffer from low porosity and insufficient strength, resulting in lower phase change enthalpy and mechanical strength in the prepared composite PCMs, thus reducing their effectiveness in building thermal management. Technical solutions

[0005] To address the aforementioned issues, we first composited high-enthalpy organic and inorganic phase change materials to form an organic-inorganic composite phase change material. Then, we added a nucleating agent to solve the supercooling problem of the organic-inorganic phase change material. Next, we introduced a second inorganic nanomaterial into the polyvinyl alcohol matrix. This nanomaterial crosslinks with the polyvinyl alcohol through supramolecular forces, forming a stable double-network aerogel used to encapsulate the organic-inorganic composite phase change material. Finally, we used the prepared polyvinyl alcohol-based double-network aerogel to encapsulate the organic-inorganic composite phase change material, successfully preparing a double-network aerogel-based organic-inorganic composite phase change material, which was then applied to building thermal management.

[0006] This work leverages the flame-retardant properties of inorganic phase change materials (PCMs) and the low supercooling and lack of phase separation inherent in organic PCMs. By utilizing nucleating agents to reduce system supercooling, an organic-inorganic composite PCM system with excellent flame-retardant performance, low supercooling, and no phase separation issues was constructed. However, polyvinyl alcohol (PVA) aerogels suffer from poor thermal stability, insufficient mechanical strength, and flammability, making their application in the construction field difficult. We introduced a second inorganic nanomaterial into the PVA aerogel matrix. This nanomaterial cross-links with PVA through supramolecular forces, forming a stable double-network structure to enhance the flame-retardant properties and mechanical strength of PVA. This resulted in an aerogel-based composite PCM with good shape stability and high mechanical strength. The results show that the prepared CPCM has a high phase transition enthalpy and good cycling stability. Furthermore, this CPCM exhibits excellent building thermal management performance, making it highly suitable for large-scale applications in future building thermal management.

[0007] A method for preparing and applying a polyvinyl alcohol-based dual-network aerogel-shaped organic / inorganic composite phase change energy storage material is disclosed. The polyvinyl alcohol-based dual-network aerogel-shaped organic / inorganic phase change energy storage material, by mass percentage, comprises 30-70 wt% inorganic solid-liquid phase change material, 40-60 wt% organic solid-liquid phase change material, 0.1-5 wt% nucleating agent, and 5-20 wt% porous support material. The inorganic solid-liquid phase change material is a hydrated inorganic salt phase change material, the organic solid-liquid phase change material is an organic nitride, organic acid ester, or long-chain alkane phase change material, the nucleating agent is a nano-oxide or a salt with similar crystal structure, and the porous support material is formed by introducing a second inorganic nanomaterial into the polyvinyl alcohol matrix. This nanomaterial cross-links with the polyvinyl alcohol through supramolecular forces to form a stable dual-network structure, thereby increasing the flame retardant properties and mechanical strength of the polyvinyl alcohol.

[0008] Preferably, the organic / inorganic composite solid-liquid phase change material is composed of 40-50 wt% inorganic solid-liquid phase change material, 45.5 wt% organic solid-liquid phase change material, 1.0 wt% nucleating agent, and 5-20 wt% porous support material by mass percentage. The phase change material can maintain a uniform and stable shape, has low undercooling, and meets thermal management requirements.

[0009] More preferably, the organic-inorganic composite solid-liquid phase change material is composed of 45.5 wt% inorganic solid-liquid phase change material, 45.5 wt% organic solid-liquid phase change material, 1.0 wt% nucleating agent, and 8.0 wt% porous support material by mass percentage.

[0010] Preferably, the inorganic solid-liquid phase change material is one to three of the following: sodium acetate trihydrate, calcium sulfate dihydrate, potassium aluminum sulfate dodecahydrate, ammonium aluminum sulfate dodecahydrate, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, calcium nitrate tetrahydrate, zinc chloride hexahydrate, and sodium thiosulfate pentahydrate.

[0011] Preferably, the organic solid-liquid phase change material is one to three of the following: urea, erythritol, xylitol, mannitol, erythritol, polyethylene glycol, neopentyl glycol, decanoic acid, lauric acid, palmitic acid, and stearic acid.

[0012] Preferably, the nucleating agent is one to three of the following: titanium dioxide, aluminum oxide, zinc oxide, sodium chloride, nano silver, nano copper, nano gold, disodium hydrogen phosphate, sodium silicate nonahydrate, silicon dioxide, disodium hydrogen phosphate dodecahydrate, and sodium metasilicate nonahydrate.

[0013] Preferably, we add some ionic cellulose gums such as xanthan gum, polysorbate, or sodium carboxymethyl cellulose to the organic-inorganic composite phase change material as a thickener to solve the phase separation problem of organic-inorganic phase change materials.

[0014] Preferably, the porous support material is primarily polyvinyl alcohol aerogel.

[0015] More preferably, the porous support material, polyvinyl alcohol aerogel, as a novel material, has advantages such as low density and high porosity, but it also has the following disadvantages:

[0016] 1. Poor thermal stability; it is easily decomposed and loses its mechanical strength in high-temperature environments.

[0017] 2. It has limited mechanical strength and is prone to breakage under mechanical impact or tension.

[0018] 3. Flammable: Polyvinyl alcohol itself is a flammable material that is easily combusted in high-temperature and open-flame environments. Therefore, it is not suitable for applications with high fire protection requirements, such as the construction industry.

[0019] Therefore, we introduce one to three inorganic nanomaterials, including silica, alumina, titanium dioxide, zirconium dioxide, montmorillonite, carbon nanotubes, nano-silicates, nickel foam, aluminum foam, copper foam, kaolin, and mesoporous carbon, into polyvinyl alcohol aerogel to form a dual network structure to increase the flame retardant properties and mechanical strength of polyvinyl alcohol.

[0020] More preferably, to address the above problems, we crosslink hydrophilic silica and polyvinyl alcohol to prepare a double-network aerogel, thus solving the aforementioned challenges. Polyvinyl alcohol molecules have numerous hydroxyl groups, which interact with the silanol groups on the silica surface through hydrogen bonds, forming a stable three-dimensional network structure. This network structure enhances the mechanical strength and stability of the aerogel. Simultaneously, the excellent flame-retardant properties and thermal stability of silica significantly improve the thermal stability and flame-retardant properties of the crosslinked double-network aerogel.

[0021] More preferably, the inorganic solid-liquid phase change material is sodium acetate trihydrate, the organic solid-liquid phase change material is urea, the nucleating agent is disodium hydrogen phosphate dodecahydrate, and the porous support material is polyvinyl alcohol-based double network aerogel.

[0022] More preferably, the organic / inorganic composite phase change material is composed of 45.5 wt% organic phase change material urea, 45.5 wt% inorganic phase change material sodium acetate trihydrate, 1.0 wt% nucleating agent disodium hydrogen phosphate dodecahydrate, and 8.0 wt% porous support material polyvinyl alcohol-based double network aerogel by mass percentage.

[0023] Another object of the present invention is to provide a method for preparing the above-mentioned organic / inorganic composite phase change material suitable for building thermal management.

[0024] A method for preparing a polyvinyl alcohol-based dual-network aerogel-shaped organic / inorganic composite phase change energy storage material with thermal insulation function includes the following process steps:

[0025] (1) First, the inorganic hydrated salt phase change material is melted by water bath heating and stirred to obtain a hydrated salt solution for later use.

[0026] (2) The organic phase change material and the above-mentioned inorganic hydrated salt solution are dissolved and mixed under water bath heating to form an organic-inorganic composite phase change material. An appropriate amount of nucleating agent is then added to reduce the supercooling problem of the composite phase change material. After stirring evenly, the organic / inorganic composite phase change material is obtained.

[0027] (3) Dissolve polyvinyl alcohol powder in deionized water for half an hour, stir for 30 minutes, add inorganic nanomaterials and mix evenly, then pour the solution into a mold. After freezing the mold in a -20℃ freezer for 12 hours, place it in a freeze dryer and dry for 24 hours to obtain polyvinyl alcohol-based double network aerogel.

[0028] (4) Prepare shaped organic / inorganic composite phase change material by vacuum impregnation method: Melt the above organic / inorganic composite phase change material; add polyvinyl alcohol-based double network aerogel to encapsulate it, and vacuum impregnate for 2 hours to obtain shaped organic / inorganic composite phase change material.

[0029] Furthermore, the specific steps are as follows:

[0030] Step 1: Preparation of organic / inorganic composite materials:

[0031] First, 4g of urea and 6g of sodium acetate trihydrate were mixed and placed in a 20mL transparent glass bottle, ensuring the total mass of the mixture was 10g. Next, the mixture was placed in a 70℃ water bath for 120 minutes to dissolve, and then stirred magnetically for 30 minutes. Then, 0.1g of disodium hydrogen phosphate dodecahydrate was added to address the supercooling issue of the composite system, and the mixture was stirred magnetically for 30 minutes to obtain the organic-inorganic composite phase change material.

[0032] Step 2: Preparation of polyvinyl alcohol-based double-network aerogel:

[0033] The preparation method of polyvinyl alcohol-based dual-network aerogel is as follows: 2.0 g of polyvinyl alcohol powder is dissolved in deionized water at 85℃ for half an hour, stirred for 30 minutes, and then the solution is poured into a mold. The mold is frozen in a freezer at -20℃ for 12 hours, and then placed in a freeze dryer to dry for 24 hours to obtain polyvinyl alcohol aerogel. The preparation method of polyvinyl alcohol-silica (PVA-SiO2) aerogel is similar to that of polyvinyl alcohol aerogel, except that after the polyvinyl alcohol powder is completely dissolved, 1.5 g of silica is added and stirred for half an hour, while other conditions remain the same. The preparation of PVA / SiO2 / CNTs aerogel is based on PVA / SiO2 aerogel, with the addition of 15 g of carbon nanotube dispersion, while keeping other conditions unchanged.

[0034] Step 3: Preparation of shape-stabilized phase change materials:

[0035] A shaped organic / inorganic composite phase change material was prepared using a vacuum impregnation method. The preparation method is as follows: First, the prepared organic / inorganic composite phase change material was placed in a 100mL beaker and then placed in a vacuum drying oven at 60℃ to melt before use. Next, polyvinyl alcohol-based double-network aerogel was added, and the mixture was placed in a vacuum drying oven for vacuum adsorption for 2 hours to obtain the shaped organic / inorganic composite phase change material.

[0036] Preferably, the phase change temperature of the phase change material used in building thermal management should be within the range of 19 to 40°C.

[0037] More preferably, the phase transition temperature of the organic-inorganic composite phase change material is 29.4℃.

[0038] More preferably, the phase transition temperature of the shaped organic-inorganic composite phase change material is 28.3℃.

[0039] More preferably, the phase transition enthalpy of the shaped organic-inorganic composite phase change material is 194.3 J / g.

[0040] Another objective of this invention is to apply the aforementioned organic / inorganic composite phase change material to the field of building energy conservation. Building energy consumption accounts for one-third of the world's total energy consumption, thus necessitating building thermal management to save energy. Studies have shown that adding appropriate amounts of phase change materials to buildings can significantly improve indoor comfort and reduce the energy demand of HVAC systems. Specifically, in the field of building thermal management, phase change materials are directly integrated into the building structure for thermal management, utilizing the latent heat capacity of the phase change materials to improve the thermal mass and thermal inertia of lightweight buildings. The phase change materials in the building can absorb solar energy, convert it into heat, and store it as latent heat, while reducing external heat dissipation during hot daytime periods. During off-peak periods (nighttime), the stored heat is released, maintaining room temperature at a certain level or reducing indoor temperature fluctuations. Beneficial effects

[0041] To evaluate the performance of the prepared phase change aerogel composite material in hot outdoor conditions, we conducted practical application tests. We constructed a simple building model to test the application effect of a polyvinyl alcohol-based dual-network aerogel-shaped organic / inorganic composite phase change energy storage material with thermal insulation function. As shown in the figure, we filled the interlayer and top with foam and CPCM respectively, and tested the time required for the internal temperature of the model to rise under outdoor sunlight. Then, we moved it to a 0℃ constant temperature and humidity chamber to cool it down (simulating the low outdoor temperature at night), and tested the time required for cooling down.

[0042] The results show that the foam group experienced a significantly faster indoor temperature rise than the experimental group. This is because the shaped organic-inorganic composite phase change material, under solar radiation, first undergoes a phase change heat storage process before transferring heat to the interior, thus maintaining a relatively low indoor temperature for a certain period. The rapid temperature rise in the foam group, however, is due to direct solar radiation. When both models were moved to a 0°C constant temperature and humidity chamber, the foam group experienced an instantaneous temperature drop, while the CPCM group showed a slower temperature change. The CPCM group maintained an indoor temperature above 18°C ​​for 8.7 times longer than the control group. This indicates that the composite phase change material releases heat during this process, maintaining a relatively stable room temperature, reducing indoor air temperature fluctuations, and increasing comfort. In summary, CPCM can significantly delay the temperature rise and fall time inside buildings, demonstrating excellent building thermal management capabilities and significant practical application value.

[0043] This invention discloses a high-enthalpy organic / inorganic composite phase change material suitable for building exterior insulation thermal management. We selected SAT (Synthetic Acid-Altered Acrylic Acid) with a phase change temperature of 57.5℃ and a phase change enthalpy of 257.6 J / g as the main phase change material, but its phase change temperature is still higher than the ideal building temperature requirement. Therefore, we used a composite method to adjust the phase change temperature of SAT. Ultimately, we chose UREA (Ultra-Ultra-Altered Acrylic Acid) to form a composite mixture with SAT to lower the phase change temperature of SAT, thereby meeting the application requirements of building thermal management.

[0044] To determine the optimal ratio of UREA / SAT composite phase change materials, we prepared UREA / SAT composite mixtures with different mass ratios (1:9 to 9:1) and used DSC characterization to test the thermal properties of the organic-inorganic composite phase change materials at different ratios. When the ratio of SAT to UREA in the system was between 1:9 and 6:4, the prepared CPCM enthalpy was higher.

[0045] To further screen for the optimal composite ratio, we conducted undercooling tests on SAT, UEA, and the UEA / SAT-DHPD composite phase change material. UEA, the raw material, exhibits no undercooling, while SAT has extremely high undercooling (approximately 52.0°C). The most common method to reduce the undercooling of SAT is to add a nucleating agent. We added DHPD (1% DHPD content) as a nucleating agent to the UEA / SAT composite system and tested the undercooling at different composite ratios. When SAT and UEA each accounted for 50% of the system, the prepared composite system showed lower undercooling. Therefore, considering both the phase transition enthalpy and the undercooling results, a 5:5 UEA / SAT (US) composite ratio was ultimately selected as the optimal composite ratio.

[0046] Because solid-liquid phase change materials (PLCs) generate a liquid phase during phase transition, leakage is highly likely when they fully transform into a liquid state, which is detrimental to their application in building thermal management. Aerogels, as porous adsorbent materials, possess advantages such as low thermal conductivity, large adsorption capacity, and highly developed nanopores, making them suitable as a supporting framework for PLCs to prevent leakage. Therefore, we innovatively prepared a PVA / SiO2 / CNTs composite aerogel. In short, firstly, PVA powder was dissolved in water to form a PVA physical cross-linked network. Secondly, SiO2 aerogel particles and carbon nanotube dispersions were added to form a pre-gel. Finally, the PVA / SiO2 / CNTs composite aerogel was prepared using freeze-drying technology. Due to its excellent mechanical properties, PVA was selected as the main network material, with PVA chains cross-linking through hydrogen bonding to form a primary network. Simultaneously, SiO2 particles and PVA chains also form a secondary network through hydrogen bonding, improving the mechanical properties of the PVA aerogel. Attached Figure Description

[0047] Figure 1a shows the infrared spectra of UREA, SAT, and US in Example 1; b shows the XRD spectra of UREA, SAT, and US in Example 1; c shows a comparison of the melting enthalpy and melting temperature of UREA, SAT, and US in Example 1.

[0048] Figure 2a shows the infrared spectra of PVA powder and PVA aerogel in Example 1; b shows the infrared spectra of PVA aerogel, SiO2 aerogel, and PVA / SiO2 in Example 1; c shows the infrared spectra of carbon nanotube solution and PVA / SiO2 / CNTs in Example 1; d shows the comparison of compressive strength of PVA aerogel, PVA / SiO2 aerogel, and PVA / SiO2 / CNTs in Example 1; e shows the pore size distribution corresponding to the nitrogen adsorption-desorption curve of PVA / SiO2 / CNTs composite aerogel in Example 1; and f shows the pore size distribution corresponding to the cumulative mercury intrusion plot of PVA / SiO2 / CNTs composite aerogel in Example 1.

[0049] Figure 3a shows the morphology of USD as a function of heating time in Implementation Case 1; b shows the morphology of USD@PVA / SiO2 / CNTs as a function of heating time.

[0050] Figure 4a shows digital photographs of sodium acetate trihydrate solutions with and without urea in Implementation Case 1; b shows combustion test results of USD@PVA / SiO2 / CNTs at different times; and c shows a comparison of USD@PVA / SiO2 / CNTs before and after combustion.

[0051] In Figure 5, a is the cooling curve of SAT in Implementation Case 1; b is the cooling curve of UREA in Implementation Case 1; c is the cooling curve of US in Implementation Case 1; d is the cooling curve of USD in Implementation Case 1; and e is the cooling curve of USD@PVA / SiO2 / CNTs in Implementation Case 1.

[0052] Figure 6a shows the DSC endothermic curves of USD and USD@PVA / SiO2 / CNTs in Example 1; b shows the DSC endothermic curves of USD@PVA / SiO2 / CNTs in Example 1 after 20, 40, 60, 80, and 100 cycles; c shows the phase transition temperature and latent heat statistics of USD@PVA / SiO2 / CNTs in Example 1 after different number of cycles; d and e are the FT-IR and XRD curves of USD, PVA / SiO2 / CNTs aerogel and USD@PVA / SiO2 / CNTs in Example 1, respectively.

[0053] In Figure 7, a is the temperature rise curve of foam and phase change material filled into the simulated building interlayer; b is the temperature drop curve of foam and phase change material filled into the simulated building interlayer. The best embodiment of the present invention

[0054] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0055] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0056] One of the specific implementation methods:

[0057] A method for preparing and applying a polyvinyl alcohol-based dual-network aerogel-shaped organic / inorganic composite phase change energy storage material, wherein the organic / inorganic composite phase change material is composed of the following components by mass percentage:

[0058] Inorganic solid-liquid phase change materials: 30~70wt%

[0059] Organic solid-liquid phase change materials: 40~60wt%

[0060] Nucleating agent: 0.1~5wt%;

[0061] Porous support material: 5~20wt%.

[0062] Preferably, the high thermal conductivity flexible phase change material of this invention is composed of the following components by mass percentage:

[0063] Inorganic solid-liquid phase change material: 45.5 wt%;

[0064] Organic solid-liquid phase change material: 45.5 wt%;

[0065] Nucleating agent: 1.0 wt%

[0066] Porous support material: 8.0 wt%.

[0067] The inorganic phase change materials of this invention are preferably 1 to 3 of the following: sodium acetate trihydrate, calcium sulfate dihydrate, potassium aluminum sulfate dodecahydrate, ammonium aluminum sulfate dodecahydrate, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, calcium nitrate tetrahydrate, zinc chloride hexahydrate, and sodium thiosulfate pentahydrate.

[0068] The preferred organic phase change material in all organic / inorganic solid-liquid phase change materials of this invention is one to three of the following: urea, erythritol, xylitol, mannitol, erythritol, polyethylene glycol, neopentyl glycol, decanoic acid, lauric acid, palmitic acid, and stearic acid.

[0069] The preferred nucleating agent for all inorganic / inorganic solid-liquid phase change materials of this invention is one to three of the following: titanium dioxide, aluminum oxide, zinc oxide, sodium chloride, nano silver, nano copper, nano gold, disodium hydrogen phosphate, sodium silicate nonahydrate, silicon dioxide, disodium hydrogen phosphate dodecahydrate, and sodium metasilicate nonahydrate.

[0070] In this invention, the porous support material of all organic / inorganic solid-liquid phase change materials is preferably polyvinyl alcohol aerogel. Secondly, inorganic nanomaterials such as silica, alumina, titanium dioxide, zirconium dioxide, montmorillonite, carbon nanotubes, nano-silicates, nickel foam, aluminum foam, copper foam, kaolin, and mesoporous carbon are added to the polyvinyl alcohol aerogel to form a double network structure to increase the flame retardant properties and mechanical strength of polyvinyl alcohol.

[0071] A method for preparing a high-enthalpy organic / inorganic composite phase change material includes the following steps: 4g of urea and 6g of sodium acetate trihydrate are mixed and placed in a 20mL transparent glass bottle, controlling the total mass of the mixture to be 10g. Next, the mixture is placed in a 70℃ water bath for 120 minutes to dissolve, and then stirred magnetically for 30 minutes. Then, 0.1g of disodium hydrogen phosphate dodecahydrate is added to address the supercooling issue of the composite system, and the mixture is stirred magnetically for 30 minutes to obtain the organic-inorganic composite phase change material.

[0072] 2.0g of polyvinyl alcohol powder was dissolved in deionized water at 85℃ for half an hour and stirred for 30 minutes until the polyvinyl alcohol powder was completely dissolved. Then, 1.5g of silica was added and stirred for half an hour. Finally, 15g of carbon nanotube dispersion was added to obtain PVA / SiO2 / CNTs aerogel.

[0073] Finally, the prepared organic-inorganic composite phase change material was placed in a 100 mL beaker and then melted in a vacuum drying oven at 60 °C. Next, polyvinyl alcohol-based double-network aerogel was added, and the mixture was placed in a vacuum drying oven for vacuum adsorption for 2 hours to obtain a shaped organic / inorganic composite phase change material.

[0074] A polyvinyl alcohol-based dual-network aerogel-shaped organic / inorganic composite phase change energy storage material with thermal insulation function can be filled into the building interlayer to effectively reduce building energy consumption and achieve energy saving. Example 1

[0075] (1) First, mix 6g of sodium acetate trihydrate (SAT) and 4g of urea (UREA) in a 20mL transparent glass bottle, place it in a 50℃ water bath for 90min to dissolve, and then stir it under magnetic stirring for 30min to obtain the composite phase change material (US). Compared with single organic or inorganic phase change materials, the enthalpy of the composite phase change material remains basically unchanged, but the phase change temperature decreases to 29.4℃, making it more suitable for some low-temperature environmental protection and energy-saving fields, such as buildings.

[0076] (2) 0.1g of disodium hydrogen phosphate dodecahydrate was added to the prepared composite phase change material to solve the problem of supercooling of the composite system. The mixture was stirred under magnetic stirring for 30 minutes to obtain the organic-inorganic composite phase change material.

[0077] (3) Dissolve 2.0g of polyvinyl alcohol powder in deionized water at 85℃ for half an hour, stir for 30 minutes, and then pour the solution into a mold. Freeze the mold in a -20℃ refrigerator for 12 hours, and then dry it in a freeze dryer for 24 hours to obtain polyvinyl alcohol aerogel. The preparation method of polyvinyl alcohol-silica (PVA-SiO2) aerogel is similar to that of polyvinyl alcohol aerogel, except that after the polyvinyl alcohol powder is completely dissolved, 1.5g of silica is added and stirred for half an hour, while other conditions remain the same. The preparation of PVA / SiO2 / CNTs aerogel is based on PVA / SiO2 aerogel, with the addition of 15g of carbon nanotube dispersion, while keeping other conditions unchanged to obtain polyvinyl alcohol-based double network aerogel.

[0078] (4) A shaped organic / inorganic composite phase change material was prepared by vacuum impregnation. The preparation method is as follows: First, the prepared organic / inorganic composite phase change material was placed in a 100 mL beaker and then placed in a vacuum drying oven at 60 °C to melt it for later use. Next, polyvinyl alcohol-based double network aerogel was added to it, and the mixture was placed in a vacuum drying oven for vacuum adsorption for 2 h to obtain the shaped organic / inorganic composite phase change material.

[0079] (5) A self-built architectural model was used to conduct building thermal management tests on the CPCM. The architectural model consisted of a 100*100*60mm hexahedron as the outer model and an 80*80*58mm smaller hexahedron as the inner model nested together. The thickness of the interlayer between the two models was 10mm. Foam and the shape-stabilized phase change material prepared in step four were added to the interlayer to test their respective thermal management performance. The specific test procedure is as follows: We filled the interlayer and the top of the model with foam and CPCM respectively, and tested the time required for the internal temperature of the model to rise under outdoor sunlight. Then we moved it to a 0℃ constant temperature and humidity chamber (YH-H, Hangzhou Wujia Machinery Co., Ltd., China) to cool it down (simulating the low temperature of the outdoor environment at night) and tested the time required for cooling down to determine the building thermal management performance of the material. Example 2

[0080] Urea: 1g; Sodium acetate trihydrate: 9g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 3

[0081] Urea: 2g; Sodium acetate trihydrate: 8g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 4

[0082] Urea: 3g; Sodium acetate trihydrate: 7g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 5

[0083] Urea: 5g; Sodium acetate trihydrate: 5g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 6

[0084] Urea: 6g; Sodium acetate trihydrate: 4g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 7

[0085] Urea: 7g; Sodium acetate trihydrate: 3g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 8

[0086] Urea: 8g; Sodium acetate trihydrate: 2g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 9

[0087] Urea: 9g; Sodium acetate trihydrate: 1g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 10

[0088] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.05g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 11

[0089] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.2g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 12

[0090] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.3g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 13

[0091] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.4g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 14

[0092] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.5g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 15

[0093] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 1g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 16

[0094] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 1.5g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 17

[0095] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2.5g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 18

[0096] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 3g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 19

[0097] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 3.5g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 20

[0098] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 4g; Silica: 1.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 21

[0099] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 0.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 22

[0100] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 23

[0101] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 2g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 24

[0102] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 2.5g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 25

[0103] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 3g; Carbon nanotube dispersion: 15g. Other conditions were the same as in Example 1. Example 26

[0104] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 0g. Other conditions were the same as in Example 1. Example 27

[0105] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 5g. Other conditions were the same as in Example 1. Example 28

[0106] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 10g. Other conditions were the same as in Example 1. Example 29

[0107] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 20g. Other conditions were the same as in Example 1. Example 30

[0108] Urea: 4g; Sodium acetate trihydrate: 6g; Disodium hydrogen phosphate dodecahydrate: 0.1g; Polyvinyl alcohol: 2g; Silica: 1.5g; Carbon nanotube dispersion: 30g. Other conditions were the same as in Example 1.

[0109] As can be seen from the infrared spectrum of the material (Figure 1a), all the diffraction peaks of UREA and SAT appeared in the US infrared spectrum, and no new diffraction peaks appeared. This indicates that UREA and SAT are only combined through physical interaction and no chemical reaction has occurred.

[0110] XRD characterization of the material (Figure 1b) shows that the diffraction peaks of the obtained US retain all the characteristic diffraction peaks of UREA and SAT, and no new characteristic peaks appear; only the peak intensities have changed. This indicates that US has formed a eutectic structure.

[0111] As can be seen from the DSC comparison chart of the materials (Figure 1c), the phase transition temperature of the eutectic phase change material is 29.4℃, which is lower than that of the raw materials SAT (57.5℃) and UREA (130.4℃), making it more suitable for the construction field.

[0112] As can be seen from the infrared spectrum of the material (Figure 2a), PVA powder and PVA aerogel exhibit a typical broad hydroxyl absorption peak at 3200~3600 cm⁻¹, which is caused by the extensive intermolecular and intramolecular hydrogen bond interactions of PVA.

[0113] As can be seen from the infrared spectrum of the material (Figure 2b), compared with PVA aerogel, the absorption vibration peak of the hydroxyl group in the PVA / SiO2 composite aerogel showed a red shift. This indicates that hydrogen bonding forces were formed between the hydroxyl groups in PVA and the Si-OH groups in silica, thus causing the shift. Finally, the infrared spectra of the CNT dispersion and PVA / SiO2 / CNTs were tested, and the results are shown in Figure 2c. It can be seen from the figure that the addition of the CNT dispersion did not form new characteristic peaks, indicating that the two are only bonded through physical interactions and no new chemical forces were formed.

[0114] Figure 2 (d) shows a comparison of the compressive strength of PVA aerogel, PVA / SiO2 aerogel, and PVA / SiO2 / CNTs. The figure shows that the compressive strength of PVA / SiO2 and PVA / SiO2 / CNTs aerogels is twice that of PVA aerogel. This is attributed to the double cross-linking network formed between PVA particles and between PVA and SiO2 particles, which significantly enhances the mechanical properties of the composite aerogel materials.

[0115] To analyze the pore structure of the PVA / SiO2 / CNTs composite aerogel, we performed full-pore size analysis using nitrogen physical adsorption and an automated mercury porosimetry system, as shown in Figure 2e. The results show that the PVA / SiO2 / CNTs aerogel has a small number of mesopores, distributed between 20 and 50 nm. Figure 2f shows that the pore size of the PVA / SiO2 / CNTs aerogel is mainly distributed between 100 and 4000 nm and between 5000 and 20000 nm, indicating that the PVA / SiO2 / CNTs composite aerogel is primarily composed of macropores. This well-developed pore structure is beneficial for adsorbing a large amount of phase change materials, thus enabling the preparation of phase change aerogel composite materials.

[0116] Figure 3 shows that a represents USD and b represents the changes in USD@PVA / SiO2 / CNTs with heating time. The figures show that USD begins to leak after about 20 minutes of heating and completely leaks after 90 minutes. In contrast, USD@PVA / SiO2 / CNTs phase change aerogel did not leak even after being heated on a 50°C heating plate for 120 minutes, demonstrating its excellent shape stability.

[0117] Figure 4a shows the results of adding and not adding urea to sodium acetate trihydrate solution. It can be seen that SAT exhibits phase separation. However, the composite system effectively solves this phase separation problem. Figures 4bc show that USD@PVA / SiO2 / CNTs remained unburned after being burned with an alcohol lamp for one minute, and no molten material dripping was observed after combustion, demonstrating the good flame-retardant properties of USD@PVA / SiO2 / CNTs.

[0118] Figure 5 shows the cooling curves of SAT in Implementation Case 1; UEA in Implementation Case 1; US ​​in Implementation Case 1; USD in Implementation Case 1; and USD@PVA / SiO2 / CNTs in Implementation Case 1. As can be seen from Figure 5, when the two form a composite system, the supercooling decreases from 52.0℃ to 11.3℃. To further reduce the supercooling, a DHPD nucleating agent was added, reducing the supercooling to 7.3℃. Finally, PVA / SiO2 / CNTs aerogel was used for shaping and encapsulation, further reducing the supercooling of USD@PVA / SiO2 / CNTs to 5.1℃.

[0119] Figure 6a shows the DSC endothermic curves of USD and USD@PVA / SiO2 / CNTs. It can be seen that the enthalpy of USD@PVA / SiO2 / CNTs is as high as 194.3 J / g, which is higher than previously reported composite phase change materials used in building thermal management, indicating its great potential in this field. Figures 6b and 6c show the results of 100 thermal cycles of USD@PVA / SiO2 / CNTs. The figures show that after 100 thermal cycles, the latent heat and phase change temperature of USD@PVA / SiO2 / CNTs during melting and solidification remained almost unchanged, indicating that the prepared CPCM has good cycling stability.

[0120] Figure 6 shows the FT-IR and XRD characterization results of USD, PVA / SiO2 / CNTs, and USD@PVA / SiO2 / CNTs. The results indicate that the two components are only physically combined, without any chemical reaction.

[0121] Considering the excellent cycling stability, low subcooling, and high enthalpy of USD@PVA / SiO2 / CNTs, we chose to conduct practical application tests, the results of which are shown in Figure 7ab. The results show that the foam group's indoor temperature rise rate is much faster than the experimental group. When both models were moved to a constant temperature and humidity chamber at 0℃ (simulating low outdoor temperatures at night), the foam group experienced an instantaneous temperature drop, while the CPCM group's temperature changed slowly. The CPCM group maintained an indoor temperature above 18℃ for 8.7 times longer than the control group. This indicates that the composite phase change material releases heat during this process, maintaining a relatively stable room temperature, reducing indoor air temperature fluctuations, and increasing surface comfort. In summary, CPCM can significantly delay the heating and cooling time inside buildings, demonstrating excellent building thermal management capabilities and significant practical application value.

[0122] To determine the optimal ratio of UREA / SAT composite phase change materials, we prepared UREA / SAT composite mixtures with different mass ratios (1:9 to 9:1) and used DSC characterization technology to test the thermal properties of the organic-inorganic composite phase change materials at different ratios. As shown in Table 1, the CPCM enthalpy values ​​were higher when the ratio of SAT to UREA in the system was between 1:9 and 6:4.

[0123] To further screen for the optimal composite ratio, we conducted undercooling tests on SAT, UEA, and the UEA / SAT-DHPD composite phase change material. UEA, the raw material, exhibits no undercooling, while SAT has extremely high undercooling (approximately 52.0℃). The most common method to reduce the undercooling of SAT is to add a nucleating agent. We added DHPD as a nucleating agent (DHPD content 1%) to the UEA / SAT composite system and tested the undercooling at different composite ratios. As shown in Table 1, when SAT and UEA each account for 50% of the system, the prepared composite system exhibits lower undercooling. Therefore, considering both the phase transition enthalpy and the undercooling results, a UEA / SAT (US) composite ratio of 5:5 was ultimately selected as the optimal composite ratio.

[0124] Embodiments of the present invention

[0125] The preparation method of this phase change material also includes: Examples 31-60

[0126] By using barium hydroxide octahydrate instead of sodium acetate trihydrate as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 61-90

[0127] Magnesium chloride hexahydrate was used instead of sodium acetate trihydrate as the phase change material to obtain a corresponding high enthalpy organic / inorganic composite phase change material, with other conditions consistent with those in Examples 1-30. Examples 91-102

[0128] By using calcium chloride hexahydrate instead of sodium acetate trihydrate as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 121-150

[0129] Magnesium sulfate heptahydrate was used instead of sodium acetate trihydrate as the phase change material to obtain a corresponding high enthalpy organic / inorganic composite phase change material, with other conditions consistent with those in Examples 1-30. Examples 151-180

[0130] By using sodium carbonate decahydrate instead of sodium acetate trihydrate as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 181-210

[0131] By using disodium hydrogen phosphate dodecahydrate instead of sodium acetate trihydrate as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 211-240

[0132] By using sodium sulfate decahydrate instead of sodium acetate trihydrate as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 241-270

[0133] By using sodium thiosulfate pentahydrate instead of sodium acetate trihydrate as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 271-300

[0134] By using erythritol instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 301-330

[0135] By using xylitol instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 331-360

[0136] By using mannitol instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 361-390

[0137] By using erythritol instead of urea as a phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 391-420

[0138] By using polyethylene glycol instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 421-450

[0139] By using neopentyl glycol instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 451-480

[0140] By using decanoic acid instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 481-510

[0141] By using lauric acid instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 511-540

[0142] Palmitic acid was used instead of urea as a phase change material to obtain a corresponding high enthalpy organic / inorganic composite phase change material, with other conditions consistent with those in Examples 1-30. Examples 541-570

[0143] By using stearic acid instead of urea as the phase change material, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 571-600

[0144] By using titanium dioxide instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 601-630

[0145] By using alumina instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 631-660

[0146] By using zinc oxide instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 661-690

[0147] By using sodium chloride instead of disodium hydrogen phosphate dodecahydrate as the nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 691-720

[0148] By using nano-silver instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 721-750

[0149] By using nano-copper instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 751-780

[0150] By using gold nanoparticles instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 781-810

[0151] By using disodium hydrogen phosphate instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 811-840

[0152] By using sodium silicate nonahydrate instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 841-870

[0153] By using silica instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 871-900

[0154] By using sodium metasilicate nonahydrate instead of disodium hydrogen phosphate dodecahydrate as a nucleating agent, a corresponding high enthalpy organic / inorganic composite phase change material was obtained, with other conditions consistent with those in Examples 1-30. Examples 901-930

[0155] Alumina was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 931-960

[0156] Titanium dioxide was used instead of silicon dioxide as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 961-990

[0157] Zirconia was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 991-1020

[0158] Montmorillonite was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 1021-1050

[0159] Nano-silicates were used instead of silica as polyvinyl alcohol-based double-network aerogels. They cross-linked with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which was used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions were the same as in Examples 1-30. Examples 1051-1080

[0160] Nickel foam was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 1081-1110

[0161] Aluminum foam was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 1111-1140

[0162] Copper foam was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 1141-1170

[0163] Kaolin was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30. Examples 1171-1200

[0164] Mesoporous carbon was used instead of silica as a polyvinyl alcohol-based double-network aerogel. It cross-links with polyvinyl alcohol through supramolecular forces to form a stable double-network structure, which is used to increase the flame retardant properties and mechanical strength of polyvinyl alcohol. Other conditions are the same as in Examples 1-30.

[0165] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Industrial applicability

[0166] Because solid-liquid phase change materials (PLCs) generate a liquid phase during phase transition, leakage is highly likely when they fully transform into a liquid state, which is detrimental to their application in building thermal management. Aerogels, as porous adsorbent materials, possess advantages such as low thermal conductivity, large adsorption capacity, and highly developed nanopores, making them suitable as a supporting framework for PLCs to prevent leakage. Therefore, we innovatively prepared a PVA / SiO2 / CNTs composite aerogel. In short, firstly, PVA powder was dissolved in water to form a PVA physical cross-linked network. Secondly, SiO2 aerogel particles and carbon nanotube dispersions were added to form a pre-gel. Finally, the PVA / SiO2 / CNTs composite aerogel was prepared using freeze-drying technology. Due to its excellent mechanical properties, PVA was selected as the main network material, with PVA chains cross-linking through hydrogen bonding to form a primary network. Simultaneously, SiO2 particles and PVA chains also form a secondary network through hydrogen bonding, improving the mechanical properties of the PVA aerogel. Sequence List Free Content

[0167] none

Claims

1. A polyvinyl alcohol-based dual-network aerogel-shaped composite phase change energy storage material, characterized in that: The material comprises inorganic solid-liquid phase change materials, organic solid-liquid phase change materials, nucleating agents, and polyvinyl alcohol-based dual-network aerogel support materials; by mass percentage: Inorganic solid-liquid phase change materials 30~70wt% Organic solid-liquid phase change materials 40~60wt% Nucleating agent 0.1~5wt%; 5-20 wt% polyvinyl alcohol-based double-network aerogel The polyvinyl alcohol-based dual-network aerogel is made by adding inorganic nanomaterials to polyvinyl alcohol aerogel. The inorganic nanomaterials cross-link with polyvinyl alcohol through supramolecular forces to form a stable dual-network structure.

2. The phase change energy storage material according to claim 1, characterized in that: The inorganic solid-liquid phase change material is one to three of the following: sodium acetate trihydrate, calcium sulfate dihydrate, potassium aluminum sulfate dodecahydrate, ammonium aluminum sulfate dodecahydrate, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, calcium nitrate tetrahydrate, zinc chloride hexahydrate, and sodium thiosulfate pentahydrate.

3. The phase change energy storage material according to claim 1, characterized in that: The organic solid-liquid phase change material is one to three of the following: urea, erythritol, xylitol, mannitol, erythritol, polyethylene glycol, neopentyl glycol, decanoic acid, lauric acid, palmitic acid, and stearic acid.

4. The phase change energy storage material according to claim 1, characterized in that: The nucleating agent is one to three of the following: titanium dioxide, aluminum oxide, zinc oxide, sodium chloride, nano silver, nano copper, nano gold, disodium hydrogen phosphate, sodium silicate nonahydrate, silicon dioxide, disodium hydrogen phosphate dodecahydrate, and sodium metasilicate nonahydrate.

5. The phase change energy storage material according to claim 1, characterized in that, The inorganic nanomaterials are 1 to 3 of the following: silicon dioxide, aluminum oxide, titanium dioxide, zirconium dioxide, montmorillonite, carbon nanotubes, nano-silicates, nickel foam, aluminum foam, copper foam, kaolin, and mesoporous carbon.

6. The method for preparing the phase change energy storage material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) First, the inorganic hydrated salt phase change material is melted by water bath heating and stirred to obtain a hydrated salt solution; (2) Dissolve and mix the organic phase change material and the above hydrated salt solution under water bath heating to form an organic-inorganic composite phase change material; then add a nucleating agent to reduce the supercooling problem of the composite phase change material, and stir evenly to obtain the organic / inorganic composite phase change material; (3) Dissolve polyvinyl alcohol powder in deionized water, stir and add inorganic nanomaterials or mix inorganic nanomaterials evenly, pour the solution into a mold; freeze the mold in a refrigerator and then put it into a freeze dryer to dry it, and polyvinyl alcohol-based double network aerogel can be obtained. (4) Prepare shaped organic / inorganic composite phase change material by vacuum impregnation: Melt the above organic / inorganic composite phase change material; add polyvinyl alcohol-based double network aerogel to encapsulate it, and obtain shaped organic / inorganic composite phase change material after vacuum impregnation.

7. The application of the phase change energy storage material according to any one of claims 1-6, characterized in that: The phase change energy storage material is used in building insulation and thermal management.

8. The application of the phase change energy storage material according to claim 6, characterized in that: The phase change energy storage material is used in a temperature range of 19~40℃.

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