Composite aerogel, recyclable heat storage phase change composite material with photothermal conversion function, and preparation method and application thereof

Abstract

The present invention relates to the field of phase change materials, specifically to a composite aerogel, which is a recyclable heat-storage phase-change composite material with photothermal conversion function, as well as a preparation method and application thereof. The composite aerogel contains a polymer and graphene, where the polymer contains a maleic anhydride group-containing structural unit and a maleimide group-containing structural unit. The composite aerogel can be used as a carrier for a phase-change material, allowing for the preparation of a recyclable heat-storage phase-change composite material with photothermal conversion function in a simple and environmentally friendly manner. The recyclable heat-storage phase-change composite material includes a composite aerogel and a phase-change material supported on the composite aerogel. The recyclable heat-storage phase-change composite material with photothermal conversion function of the present invention not only has photothermal conversion function, but also has low leakage of the phase-change material and is recyclable, thereby truly realizing environmentally friendly utilization and effective storage of solar energy. The recyclable heat-storage phase-change composite material has high utility value in terms of utilizing energy in an environmentally friendly and clean manner.

Description

Detailed Description of the Invention

[0001] [Technical Field] The present invention relates to the field of phase change materials, and in particular to a composite aerogel, a recyclable heat storage phase change composite material with photothermal conversion function, and its preparation method and use.

[0002] [Background technology] With the rapid increase in energy consumption and greenhouse gas emissions, there has been great interest in utilizing renewable energy sources such as solar energy and waste heat in an environmentally friendly manner. Because solar energy varies temporally and spatially, the mismatch between energy supply and demand poses a significant challenge in efficiently storing these energy sources. Latent heat storage systems based on organic phase change materials (PCMs) offer large storage capacities, nearly constant phase change temperatures, and reversible storage and release of thermal energy. Phase change materials can bridge the significant gap between rapidly growing energy demand and limited fossil fuel reserves. Therefore, PCMs are currently widely used in air conditioning systems, building materials, solar energy storage, waste heat recycling, and various electronic products. Organic PCMs are the most widely studied PCMs, boasting advantages such as stable performance, low supercooling, and no phase separation. They primarily contain paraffins, fatty acids, fatty alcohols, and other organic compounds. However, when used directly as energy storage materials, they are susceptible to leakage, making encapsulation essential to prevent leakage problems. In addition, the reprocessability and recyclability of organic phase change materials must also be considered to avoid environmental pollution and resource waste caused by organic phase change materials.

[0003] Therefore, if a material with photothermal conversion performance can be provided and combined with a phase change material to obtain a recyclable cold storage phase change composite material with good photothermal conversion performance, little leakage of phase change material, and high recyclability, a major breakthrough in this field can be achieved.

[0004] [Contents of the invention] In view of the technical problems existing in the prior art, the present invention aims to provide a composite aerogel, a recyclable heat-storage phase-change composite material with photothermal conversion function, a preparation method thereof, and its use. The composite aerogel of the present invention can be used as a carrier for a phase-change material to obtain a recyclable heat-storage phase-change composite material with photothermal conversion function. At the same time, the composite aerogel of the present invention can be recovered in a simple and environmentally friendly manner. The recyclable heat-storage phase-change composite material with photothermal conversion function not only has photothermal conversion function, but also has low leakage and is recyclable, truly realizing the environmentally friendly utilization and effective storage of solar energy.

[0005] The inventors of the present invention discovered that maleimide-based copolymers (polymers containing maleic anhydride and maleimide groups) can be prepared using low-cost copolymers and recovered using aqueous ammonia. In light of the prior art, the applicants of the present invention conducted research and found that composite aerogels of maleimide-based copolymers and reduced graphene oxide can be prepared by mixing such copolymers with graphene oxide and a reducing agent. Preferably, water-resistant maleimide-based copolymer-graphene composite aerogels can be obtained by quickly and efficiently reducing the aerogel under microwave irradiation. The composite aerogels can be used as carriers for phase-change materials, preventing leakage of the phase-change material. They can be recycled under the action of aqueous ammonia to obtain graphene, phase-change material, and polymer, respectively. Based on the above, the present invention aims to provide composite aerogels that can be used as carriers for phase-change materials and prevent leakage and enable recycling of photothermal conversion phase-change materials, as well as recyclable heat-storage phase-change composite materials with photothermal conversion functions, as well as methods for preparing and using the same.

[0006] A first aspect of the present invention provides a composite aerogel comprising a polymer and graphene, where the polymer contains a maleic anhydride group-containing structural unit and a maleimide group-containing structural unit. The composite aerogel can be used as a carrier for obtaining a recyclable heat storage phase change material with a phase change material and a photothermal conversion function, and can also be recycled in a simple and environmentally friendly manner.

[0007] In a preferred embodiment of the present invention, I in the Raman spectrum of the surface of the composite aerogel D / I G The average value of is 1.2 or less, preferably 0.9 or less, and more preferably 0.85 or less.

[0008] According to the present invention, the mass ratio of graphene to polymer can be selected within a wide range, and in a preferred embodiment of the present invention, the mass ratio of graphene to polymer is (1:20) to (10:1), preferably (1:10) to (6:1), more preferably (1:5) to (1:1), i.e., 1:(1 to 5). For example, the ratio may be 1:1, 2:3, 4:5, or any two numbers or any interval between any two numbers.

[0009] According to the present invention, the polymer in the composite aerogel can be dissolved in ammonia water at 0°C to 150°C to form an aqueous polymer solution.

[0010] In a preferred embodiment of the present invention, graphene in the raw material for preparing the composite aerogel of the present invention is derived from the reduction of graphene oxide, which must first be pre-reduced with a reducing agent and then reduced under microwaves. That is, graphene can be obtained by reducing graphene oxide, preferably by pre-reducing graphene oxide with a reducing agent and then reducing it under microwaves.

[0011] According to the present invention, the reducing agent can be selected from a wide range, and in a preferred embodiment of the present invention, the reducing agent is selected from at least one of ascorbic acid, gallic acid, sodium borohydride, and amino acids.

[0012] According to the present invention, the maleic anhydride group is [ka] The maleimide group refers to [ka] Refers to...

[0013] According to the present invention, the polymer is a carbon chain polymer in which heteroatoms O and N are present in pendant groups.

[0014] In a preferred embodiment of the present invention, the molar proportion of the maleimide group-containing structural units in the polymer is 5% to 70%, preferably 10% to 60%, and more preferably 20% to 50%, relative to the total molar amount of the maleic anhydride group-containing structural units and the maleimide group-containing structural units, which is 100%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and any two numerical values ​​or any interval between any two numerical values.

[0015] According to the present invention, the polymer can be selected from a wide range of options. In a preferred embodiment of the present invention, the polymer is derived from a polymer raw material containing one or more of a maleic anhydride group-containing structural unit, a maleimide group-containing structural unit, a structural unit containing maleic acid and its ammonium salt group, and a structural unit containing maleamic acid and its ammonium salt group; that is, the maleic anhydride groups and maleimide groups in the polymer aerogel are derived from at least one of the maleic anhydride groups, maleimide groups, maleic acid and its ammonium salt groups, and maleamic acid and its ammonium salt groups in the polymer raw material.

[0016] The maleic anhydride group is [ka] The maleimide group refers to [ka] Maleic acid and its ammonium base, maleamic acid and its ammonium base are [ka] where M is the same or different and is hydroxyl or amino or ammonium (O-NH4), respectively.

[0017] According to the present invention, the polymer is a carbon chain polymer in which heteroatoms O and N are present in pendant groups.

[0018] In the present invention, the polymer raw material includes, but is not limited to, a copolymer of a polymerizable monomer containing one or more of maleic anhydride, maleimide, maleic acid and its ammonium salt, and maleamic acid and its ammonium salt with an olefin monomer. For example, the present invention can be achieved when the polymer raw material is a styrene-maleic anhydride-vinyl silicone oil copolymer. The copolymer of a polymerizable monomer containing one or more of maleic anhydride, maleimide, maleic acid and its ammonium salt, and maleamic acid and its ammonium salt with an olefin monomer has lower raw material costs.

[0019] Preferably, the polymeric material is a copolymer of a polymerizable monomer comprising one or more of maleic anhydride, maleimide, maleic acid and its ammonium salt, and maleamic acid and its ammonium salt, and an olefinic monomer; more preferably, the olefinic monomer is at least one of α-methylstyrene, styrene, and isobutylene; more preferably, the polymeric material is an alternating copolymer of a polymerizable monomer comprising one or more of maleic anhydride, maleimide, maleic acid and its ammonium salt, and maleamic acid and its ammonium salt, and one of α-methylstyrene, styrene, and isobutylene.

[0020] As an example, the polymer raw material in the present invention may include, but is not limited to, at least one of a styrene-maleic anhydride copolymer and a maleic anhydride-isobutylene copolymer. Preferably, the polymer raw material is a styrene-maleic anhydride copolymer.

[0021] In a preferred embodiment of the present invention, the composite aerogel can be dissolved in ammonia water at 0°C to 150°C to form an aqueous polymer solution. Based on this, the polymer aerogel of the present invention can be conveniently recycled in an environmentally friendly manner.

[0022] According to the present invention, the polymer in the composite aerogel has good heat resistance, and maintains good heat resistance even after recycling, making it very suitable as a photothermal conversion heat storage carrier.

[0023] In a preferred embodiment of the present invention, the composite aerogel is prepared by reacting a polymer raw material containing one or more of a maleic anhydride group-containing structural unit, a maleimide group-containing structural unit, a structural unit containing maleic acid and its ammonium salt group, or a structural unit containing maleamic acid and its ammonium salt group with aqueous ammonia under sealed conditions, followed by mixing with graphene oxide and a reducing agent, pre-freezing, freeze-drying, dehydration and deamination, and reduction.

[0024] A second aspect of the present invention provides a method for preparing the composite aerogel according to the first aspect, the method comprising: reacting a polymer raw material containing one or more of a maleic anhydride group-containing structural unit, a maleimide group-containing structural unit, a structural unit containing a maleic acid and its ammonium salt group, and a structural unit containing a maleamic acid and its ammonium salt group with ammonia hydrate under sealed conditions; mixing the resulting polymer raw material with graphene oxide and a reducing agent; pre-freezing the resulting polymer; freeze-drying the resulting polymer; dehydrating and deaminating the resulting polymer; and reducing the resulting polymer raw material to obtain a composite aerogel.

[0025] In the method for preparing the composite aerogel of the present invention, no crosslinking agent is added.

[0026] In a preferred embodiment of the present invention, the preparation method comprises the following steps: (1) a step of reacting a polymer raw material with aqueous ammonia under a sealed condition to obtain an aqueous polymer solution; (2) mixing the polymer aqueous solution obtained in step (1) with graphene oxide and a reducing agent to obtain a mixed solution, and then pre-freezing and freeze-drying the mixed solution to obtain a composite polymer; (3) A step in which the composite polymer obtained in step (2) is dehydrated and deaminated by heat treatment, and then reduced under microwave irradiation to obtain a maleimide copolymer-graphene composite aerogel.

[0027] According to the present invention, the blending amounts of the polymer raw material, aqueous ammonia, etc. in step (1) can be selected from a wide range, and in a preferred embodiment of the present invention, the mass fraction of the polymer raw material is 0.1% to 30%, preferably 0.5% to 10%, and more preferably 1% to 5%, of the total mass of the reaction system being 100%; the mass fraction of ammonia in the raw material is 0.001% to 30%, preferably 0.01% to 10%, and more preferably 0.1% to 1%, relative to the mass of ammonia in the aqueous ammonia, with the remainder being water.

[0028] According to the present invention, the reaction conditions in step (1) can be selected from a wide range, and in a preferred embodiment of the present invention, the reaction conditions include a reaction temperature of 0°C to 200°C, preferably 50°C to 150°C, and more preferably 80°C to 100°C, and / or a reaction time of 0.01 hours to 100 hours, preferably 0.5 hours to 10 hours, and more preferably 1 hour to 5 hours. The reaction pressure is not particularly limited, and it is preferable to carry out the reaction under normal pressure.

[0029] According to the present invention, the conditions for step (2) can be selected from a wide range. In a preferred embodiment of the present invention, in step (2): graphene oxide is derived from a dispersion containing graphene oxide, and the concentration of graphene oxide in the dispersion (i.e., the mass ratio of graphene oxide to water) is 1 mg / mL to 100 mg / mL, preferably 3 mg / mL to 30 mg / mL, and more preferably 5 mg / mL to 20 mg / mL.

[0030] According to the present invention, the reducing agent can be selected from a wide range, and in a preferred embodiment of the present invention, the reducing agent is selected from at least one of ascorbic acid, gallic acid, sodium borohydride, and amino acids.

[0031] According to the present invention, the mass ratio of reducing agent to graphene oxide can be selected within a wide range, and in a preferred embodiment of the present invention, the mass ratio of reducing agent to graphene oxide is 1:(0.1-20), preferably 1:(1-3), for example, a ratio of 1:1, 1.5, 2, 2.5, 3, as well as any two numbers or any interval between any two numbers.

[0032] According to the present invention, the polymer aerogel in the present invention may be an anisotropic aerogel or an isotropic aerogel.

[0033] The difference between anisotropic and isotropic aerogels is their pore structure. The pore structure of anisotropic aerogels exhibits long-range order, which is primarily due to the directional growth of ice crystals during the pre-freezing stage of the aerogel. During the growth process, impurities are expelled and accumulate, forming pore walls. Therefore, anisotropic aerogels can be obtained by using a different cold source temperature in one direction during pre-freezing. There are many options for the unidirectional cold source temperature, including, but not limited to, liquid nitrogen as the low-temperature cold source. A mold containing a mixture of an aqueous polymer solution, graphene oxide, and a reducing agent is placed on a copper pillar immersed in liquid nitrogen, causing ice crystals to grow upward from the bottom of the mold.

[0034] Anisotropic aerogels are characterized by different pore structures, different axial and radial thermal conductivities, and different mass and acoustic conductivities. Anisotropic aerogels / isotropic aerogels can be selected according to different application conditions. For example, the inventors of the present invention have found that the use of a preferred anisotropic aerogel during the encapsulation of a phase-change material can significantly reduce leakage, and there is no requirement for the direction of the anisotropic aerogel.

[0035] According to the present invention, the cold source temperatures in various directions of the mixed solution during pre-freezing may be the same or different, and in a preferred embodiment of the present invention, the cold source temperatures in various directions of the mixed solution during pre-freezing are different, and preferably, the cold source temperatures in a single direction of the mixed solution (i.e., the mixed aqueous solution of the copolymer, graphene, and reducing agent obtained after the amination reaction) during pre-freezing are different. In this preferred embodiment, leakage of the phase change material is reduced.

[0036] Preferably, the unidirectional cold source temperature during pre-freezing is different to obtain anisotropic aerogel. There are many options for the unidirectional cold source temperature, but pre-freezing uses liquid nitrogen as a low-temperature cold source, and ice crystals grow upward from the bottom of the mold by placing the mold on a copper pillar immersed in liquid nitrogen.

[0037] Specifically, the conditions for pre-freezing may be conventional temperature conditions in the art, and in the present invention, are not particularly limited as long as the mixed solution of the aqueous polymer solution, graphene oxide, and reducing agent obtained in step (2) is frozen.

[0038] According to the present invention, the freeze-drying conditions can be selected from a wide range and are not particularly limited in the present invention. In a preferred embodiment of the present invention, the freeze-drying conditions include: a temperature of −10° C. or lower, for example, −20° C. or lower or −30° C. or lower, and / or a vacuum of 1000 Pa or lower, for example, 100 Pa or lower or 10 Pa or lower.

[0039] The freeze-drying process can be carried out using a variety of freeze-drying devices in the prior art, such as freeze dryers, freeze spray dryers and industrial freeze dryers.

[0040] According to the present invention, the conditions for step (3) can be selected from a wide range, and in a preferred embodiment of the present invention, the conditions for the heat treatment in step (3) include: a temperature of 100°C to 300°C, preferably 120°C to 220°C, and more preferably 160°C to 200°C; and / or a heat treatment time of 0.1 hours to 10 hours, preferably 0.5 hours to 3 hours, and more preferably 1 hour to 2 hours.

[0041] According to the present invention, the microwave irradiation conditions can be selected from a wide range. In a preferred embodiment of the present invention, the microwave irradiation output is 500 W to 2000 W; the microwave irradiation time is 1 second to 10 seconds, preferably 2 seconds to 7 seconds, and more preferably 3 seconds to 5 seconds.

[0042] According to the present invention, the polymeric raw material can be selected from a wide range, and in a preferred embodiment of the present invention, the polymeric raw material can be reacted with aqueous ammonia to obtain a water-soluble polymer.

[0043] In a preferred embodiment of the present invention, the polymer raw material is a polymer containing one or more of structural units containing groups of maleic anhydride, maleimide, maleic acid and its ammonium salt, and structural units containing groups of maleamic acid and its ammonium salt; preferably, the polymer raw material is a copolymer of a polymerizable monomer containing one or more of maleic anhydride, maleimide, maleic acid and its ammonium salt, and maleamic acid and its ammonium salt with an olefin monomer; more preferably, the olefin monomer includes at least one of α-methylstyrene, styrene, and isobutylene; by way of example, the polymer raw material may be at least one of a styrene-maleic anhydride copolymer and a maleic anhydride-isobutylene copolymer, but is not limited to these.

[0044] The above polymeric raw materials are all polymers disclosed in the prior art and can be commercially obtained from the prior art or prepared according to methods disclosed in the prior art.

[0045] In the present invention, the material of the sealed container is not particularly limited, and the sealed container may be made of metal, non-metal, polymer, or other material.

[0046] As used herein, the term "and / or" means that the two conditions before and after "and / or" can be selected alternately or in combination.

[0047] A third aspect of the present invention provides a recyclable heat storage phase change composite material, the heat storage phase change composite material comprising a composite aerogel and a phase change material supported on the composite aerogel; the composite aerogel is the composite aerogel described in the first aspect or a composite aerogel prepared by the preparation method described in the second aspect.

[0048] According to the present invention, the mass ratio of the composite aerogel to the phase change material can be selected within a wide range, and in a preferred embodiment of the present invention, the mass ratio of the composite aerogel to the phase change material is 1:(0.05-50), for example, a ratio of 1 to 0.05, 0.1, 0.5, 1, 5, 10, 20, 30, 40, 50, as well as any two numbers or any interval between any two numbers.

[0049] According to the present invention, the phase change material can be selected from a wide range, preferably an organic phase change material, preferably a heat storage phase change material, including but not limited to a water-soluble phase change material and / or a water-insoluble phase change material, more preferably at least one of polyethylene glycol, lauric acid, stearyl alcohol, and paraffin.

[0050] In a preferred embodiment of the present invention, the leakage rate of the phase change material in the recyclable heat storage phase change composite material is less than 10 wt%, preferably less than 5 wt%, more preferably less than 2 wt% under temperature conditions in which the phase change material is in a liquid state.

[0051] The present invention also provides a method for recycling composite aerogel or recyclable heat-storage phase-change composite material. The method includes the steps of: mixing and reacting the composite aerogel and / or recyclable heat-storage phase-change composite material with aqueous ammonia under sealed conditions until an aqueous solution containing the recycled polymer is obtained; and removing insoluble substances (graphene, phase-change material) to obtain an aqueous solution of the recycled polymer. This aerogel recycling method does not require the introduction of organic solvents or high-temperature, high-pressure stirring treatment; it only requires a certain concentration of aqueous ammonia (preferably maintained at 100°C or below), making it possible to achieve rapid and efficient recycling. The method is characterized by low energy consumption, low pollution, and high efficiency. The recycled polymer solution can be reused to prepare polymer aerogel.

[0052] According to the present invention, the conditions for the mixing reaction in the recycling method can be selected from a wide range, and in a preferred embodiment of the present invention, the temperature for the mixing reaction is 0°C to 200°C, preferably 50°C to 150°C, and more preferably 80°C to 100°C, and / or the time for the mixing reaction is 0.01 hours to 100 hours, preferably 0.5 hours to 10 hours, and more preferably 1 hour to 5 hours. The reaction pressure is not particularly limited, and the reaction is preferably carried out under normal pressure.

[0053] In a preferred embodiment of the present invention, the recycling method further comprises reusing the recycled aqueous polymer solution, for example, by continuing with step (2) and subsequent steps of the preparation method described in the second aspect of the present invention to prepare a composite aerogel again.

[0054] A fourth aspect of the present invention provides a method for preparing the recyclable heat storage phase change composite material according to the third aspect, the method comprising loading a phase change material onto a composite aerogel.

[0055] According to the present invention, a method for preparing a recyclable heat storage phase change composite material includes: obtaining a composite aerogel using the preparation method described in the second embodiment; and loading a phase change material onto the composite aerogel. The loading method can be any of the various loading methods known in the prior art. Specifically, the molten phase change material can be adsorbed (encapsulated) and / or impregnated into the composite aerogel.

[0056] According to the present invention, the type and ratio of the phase change material can be selected from a wide range, and preferably the type and ratio of the phase change material described in the third aspect of the present invention.

[0057] A fifth aspect of the present invention provides the use of the recyclable heat storage phase change composite material according to the fourth aspect in the fields of building energy conservation, air conditioning systems, waste heat utilization and solar energy storage.

[0058] According to the above technical solution, the present invention provides a composite aerogel, a recyclable heat storage phase change composite material with photothermal conversion function, and its preparation method and use. Compared with the prior art, the present invention has the following advantages: In the present invention, a composite aerogel is used as a carrier, and graphene imparts photothermal conversion functionality to the phase-change material. Therefore, the graphene-containing aerogel phase-change composite can be heated to 70°C or higher within 30 minutes under sunlight irradiation and maintain a temperature of 50°C or higher for a long period of time, demonstrating excellent photothermal conversion and heat storage performance. By combining this with the heat storage performance of the phase-change material, the recyclable heat-storing phase-change composite with photothermal conversion functionality of the present invention can achieve highly efficient utilization of solar energy.

[0059] The composite aerogel and recyclable heat storage phase change composite material with photothermal conversion function of the present invention can be recycled in an environmentally friendly manner; Both the polymer and recycled polymer in the composite aerogel have excellent heat resistance, and at the same time, the porous structure of the composite aerogel reduces leakage of the phase change material, all of which ensures the stability of photothermal conversion and heat storage.

[0060] In conclusion, the recyclable heat storage phase change composite material with photothermal conversion function of the present invention not only has photothermal conversion function but also has good heat storage performance. Furthermore, there is little leakage of the phase change material, and the entire material can be recycled, truly realizing the environmentally friendly utilization and effective storage of solar energy. The heat storage phase change composite material has extremely high utility value in the utilization of environmentally friendly clean energy.

[0061] DESCRIPTION OF THE DRAWINGS Figure 1 shows the DSC curves and glass transition temperatures Tg of the maleimide-based aerogel of Comparative Example 1 and the recycled polymer aerogel of Example 4; Figure 2 shows the thermogravimetric curves of the maleimide-based aerogel of Comparative Example 1 and the recycled polymer aerogel of Example 4; The test results in Figures 1 and 2 show that maleimide-based aerogel has good heat resistance, with a glass transition temperature of around 250°C and a decomposition temperature of around 300°C, and that the heat resistance of the aerogel prepared using recycled polymers is higher than that of the aerogel before recycling. This proves that both the polymers before and after recycling the aerogel have good heat resistance and that the recycling process is green and environmentally friendly.

[0062] FIG. 3 shows the temperature curves of the phase change materials of Examples 2 and 5 under one solar illumination intensity and after removal of illumination. The test results in Figure 3 show that graphene imparts photothermal conversion functionality to the phase-change material. Therefore, the graphene-containing aerogel phase-change composite can be heated to above 70°C within 30 minutes under simulated solar irradiation and can maintain a temperature above 50°C for a long time, demonstrating excellent photothermal conversion and heat storage performance and enabling highly efficient utilization of solar energy.

[0063] 4 shows the recycling of the maleimide copolymer-graphene aerogel phase change composite (a) obtained in Example 2, and the graphene phase change composite (b) and polymer aerogel (c) obtained by the recycling, as described in Example 4. Each of the materials in the recyclable heat storage phase change composite with photothermal conversion function of the present invention can obviously be recycled and reused.

[0064] Detailed Description of Specific Embodiments The present invention will be specifically described below in conjunction with specific examples. It should be noted that the following examples are only used to further explain the present invention and should not be understood as limiting the protection scope of the present invention. Some insubstantial improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0065] The present invention will be further described with reference to the following examples; however, the present invention is not limited to these examples.

[0066] The experimental data in the examples was determined using the following equipment and methods: 1. Raman Spectra of Aerogels D / I G Test method: The test was performed using a Horiba Jobin Yvon Lab RAM HR800 Raman spectrometer, with the curves processed using the instrument's built-in software. D Value and I G got the value.

[0067] 2. Aerogel thermal stability test method The thermal stability of 5 mg of aerogel samples was tested by thermogravimetric analysis (TGA, Mettler Toledo, Switzerland) under nitrogen flow at a heating rate of 20 °C / min in the temperature range of 50 °C to 550 °C.

[0068] 3. Test method for glass transition temperature of aerogel: The glass transition temperatures of the samples were measured using a Perkin-Elmer pyris spectrometer calibrated with indium and zinc standards. -1 Tests were performed using a differential scanning calorimeter (DSC). 5-6 mg samples from the injection rod were heated from 150 to 300 °C under nitrogen flow and held at 300 °C for 3 minutes. The samples were then cooled to 150 °C, held for 1 minute, and then heated again to 300 °C. The program rate for all heating and cooling steps was 10 °C / min. The glass transition temperature (Tg) was determined from the relevant peak in the DSC curve.

[0069] 4. Test method for simulated solar lighting temperature change curve of phase change materials: The phase change material was cut into a 3cm x 3cm x 0.3cm sheet to be used as a test sample. Solar irradiation was simulated at 20°C using a solar simulator, Sirius-SS300A-D, manufactured by Zolix Instruments. The sample was placed in a polystyrene foam box without a cap, and the temperature change of the phase change composite was monitored throughout the process with a thermocouple. First, the sample was irradiated with 100mW / cm 2 After irradiation for approximately 34 minutes at an illumination intensity of 1 sun, the simulated light source was turned off.

[0070] 5. Leakage test method for phase change materials: 15 g of the sample obtained in the examples was taken, and filter paper was placed on a heating table at 120°C. After the sample was left on the filter paper for 10 minutes, the sample was removed and its weight was recorded as m (g). The leakage rate was calculated as m / 15 x 100 wt%; if the sample was completely melted and could not be removed, the leakage rate was recorded as 100 wt%.

[0071] 6. Phase transition temperature test method: Thermal properties of aerogels and phase change materials were measured using Perkin-Elmer Pyris™, calibrated with indium and zinc standards. -1 Tests were performed using a differential scanning calorimeter (DSC). For the aerogels, samples were heated from 20°C to 150°C under nitrogen flow and held at 20°C and 150°C for 5 minutes. For the phase-change materials, samples were heated from 50°C to 300°C under nitrogen flow and held at 50°C and 300°C for 5 minutes. The program rate for all heating and cooling steps was 20°C / min. The latent heats of fusion (ΔHm) and solidification (ΔHf), as well as the melting temperature (Tm) and solidification temperature (Tf), were determined from the relevant peaks in the DSC curves.

[0072] The raw materials used in the examples are shown in Table I. [Table 1]

[0073] Preparation Example 1 Preparation of polymer in the present invention: 500 ml of isoamyl acetate was placed in a 1000 ml three-neck flask and flushed with nitrogen for 30 minutes to remove oxygen. 24.5 g of maleic anhydride and 26 g of styrene were added to the flask. After complete dissolution, 0.4 g of azodiisobutyronitrile was added, and the water bath temperature was raised to 70°C and the reaction was carried out for 7 hours. After the reaction, the reaction solution was centrifuged at 10,000 rpm for 10 minutes. The supernatant was removed, and then 500 ml of methanol was added. The mixture was stirred for 0.5 hours, centrifuged, and the supernatant was removed. This process was repeated twice. The reaction product was then dried under reduced pressure at 140°C for 24 hours to obtain a styrene-maleic anhydride copolymer.

[0074] Example 1 After adding 93.2 g of water to a capped glass bottle, 2.8 g of ammonia water (25% by mass) and 4 g of maleic anhydride-styrene copolymer were added. After tightly tightening the cap, the glass bottle was placed in an oven and kept at 95°C for 4 hours. After that, a homogeneous polymer solution (4% by mass) was obtained.

[0075] 100 g of a 20 mg / ml graphene oxide aqueous solution was added to a glass bottle, followed by 4 g of ascorbic acid, followed by magnetic stirring at 1,000 rpm for 5 minutes. After uniform mixing, the mixture was quickly poured into a cylindrical mold with a copper base and polytetrafluoroethylene walls. The mold was then placed on a copper column in a liquid nitrogen bath. After pre-freezing (i.e., the mixture was frozen in ice), the mixture was placed in a freeze dryer and freeze-dried for 72 hours (at a temperature of -30 °C or below and a pressure of 10 Pa or below) to obtain anisotropic water-soluble GO / SMI composite aerogels.

[0076] The aerogel was then placed in a nitrogen-filled polytetrafluoroethylene inner tank, which was then placed in a thermostatic chamber at 180°C for 2 hours for heat treatment. The sample was then removed, placed in a nitrogen-filled sealed quartz tank, and microwave-treated (irradiation power 800 W) for 3 seconds to obtain a maleimide-styrene copolymer-graphene composite aerogel (i.e., the composite aerogel of the present invention).

[0077] Example 2 Maleimide-graphene composite aerogel was prepared according to the method described in Example 1. 0.2 g of maleimide-graphene composite aerogel was added to a polytetrafluoroethylene beaker containing 20 g of sliced ​​paraffin. The beaker was placed in a vacuum oven and maintained at 100°C for 2 hours. The molten paraffin penetrated the maleimide-graphene composite aerogel, resulting in an aerogel phase-change composite. The aerogel phase-change composite was removed from the beaker and wiped to remove excess phase-change material from the surface of the aerogel phase-change composite. The aerogel phase-change composite was then left at room temperature for 2 hours and weighed to obtain a maleimide copolymer-graphene aerogel phase-change composite (approximately 10 g of paraffin adsorbed).

[0078] Example 3 The same experiment as in Example 2 was carried out, except that the phase change material in Example 2 was changed from paraffin to stearyl alcohol (purchased from Aladdin).

[0079] The recycling effect of the obtained phase change composite material was similar to that of Example 2.

[0080] Example 4 The phase-change composite material sample obtained in Example 2 was crushed to powder. 5 g of this powder was placed in a glass bottle with a cap, and 0.2 g of 25% ammonia water and 30 ml of water were added. The mixture was heated to 95°C and held for 1 hour under magnetic stirring at 1000 rpm. The mixture was then filtered while still hot (Figure 4a). The filtrate was then heated and concentrated to approximately 5 ml. The concentrated filtrate was poured into a mold, pre-frozen in a refrigerator, and then freeze-dried in a freeze dryer (temperature below -30°C and pressure below 10 Pa) to obtain a recycled polymer aerogel (Figure 4c). The filter cake was then air-dried, placed in a small beaker, heated to 100°C to melt it, and held for 1 hour before cooling to obtain a high-value-added graphene phase-change composite material, which was then cut and shaped as needed (Figure 4b). Clearly, the recyclable heat-storage phase-change composite material with photothermal conversion function of the present invention can be recycled and reused.

[0081] Example 5 After adding 91.5 g of water to a capped glass bottle, 3.5 g of ammonia water (25% by mass) and 5 g of maleic anhydride-styrene copolymer were added. After tightly tightening the cap, the glass bottle was placed in an oven and kept at 95°C for 4 hours. After removal, a homogeneous polymer solution with a mass fraction of 5% was obtained.

[0082] 15 ml of the polymer solution was poured into each of six molds and then frozen in a refrigerator at -30°C for 2 hours. The frozen sample was transferred to a freeze dryer and freeze-dried for 72 hours (below -30°C and below 10 Pa) to obtain a water-soluble polymer aerogel. This water-soluble polymer aerogel was then placed in an incubator at 180°C for heat treatment, dehydration, and deamidation to obtain a maleimide-based aerogel.

[0083] 0.5 g of maleimide-based polymer aerogel was added to a 30 ml polytetrafluoroethylene beaker containing 20 g of sliced ​​paraffin. The beaker was placed in a vacuum oven and heated to 100°C for 2 hours to obtain an aerogel phase-change composite. After removing the aerogel phase-change composite from the beaker, it was wiped to remove excess phase-change material from the surface of the aerogel phase-change composite. It was then left to stand at room temperature for 2 hours and weighed to obtain a maleimide-based copolymer aerogel phase-change composite (approximately 7 g of paraffin adsorbed).

[0084] Example 6 The preparation procedure was the same as that of Example 1, except that the microwave treatment time in Example 1 was changed to 1 second.

[0085] Example 7 After adding 93.2 g of water to a capped glass bottle, 2.8 g of ammonia water (25% by mass) and 4 g of maleic anhydride-styrene copolymer were added. After tightly tightening the cap, the glass bottle was placed in an oven and kept at 95°C for 4 hours. After that, a homogeneous polymer solution with a mass fraction of 4% was obtained.

[0086] 100 g of a 20 mg / ml graphene oxide aqueous solution was added to a glass bottle, followed by 4 g of ascorbic acid, followed by magnetic stirring at 1,000 rpm for 5 minutes. After uniform mixing, the mixture was quickly poured into a cylindrical mold with a copper base and polytetrafluoroethylene walls. The mold was then placed on a copper column in a liquid nitrogen bath. After pre-freezing, the frozen mixture was placed in a freeze dryer and freeze-dried for 72 hours (below -30 °C and below 10 Pa) to obtain anisotropic water-soluble GO / SMI composite aerogels.

[0087] The aerogel was then placed in a nitrogen-filled polytetrafluoroethylene inner tank, which was then placed in a thermostatic chamber at 180°C for 2 hours for heat treatment. The sample was then removed, placed in a nitrogen-filled sealed quartz tank, and microwave-treated (irradiation power 800 W) for 5 seconds to obtain a maleimide-styrene copolymer-graphene composite aerogel.

[0088] Example 8 93.2 g of water was added to a capped glass bottle, followed by 2.8 g of ammonia water (25% by mass) and 4 g of maleic anhydride-styrene copolymer. After the cap was tightly fastened, the glass bottle was placed in an oven and kept at 95°C for 4 hours. After that, a homogeneous polymer solution (4% by mass) was obtained.

[0089] 100 g of a 20 mg / ml graphene oxide aqueous solution was added to a glass bottle, followed by 4 g of ascorbic acid, followed by magnetic stirring at 1,000 rpm for 5 minutes. After uniform mixing, the mixture was quickly poured into a cylindrical mold with a copper base and polytetrafluoroethylene walls. The mold was then placed on a copper column in a liquid nitrogen bath. After pre-freezing, the frozen mixture was placed in a freeze dryer and freeze-dried for 72 hours (below -30 °C and below 10 Pa) to obtain anisotropic water-soluble GO / SMI composite aerogels.

[0090] The aerogel was then placed in a nitrogen-filled polytetrafluoroethylene inner tank, which was then placed in a thermostatic chamber at 180°C for 2 hours for heat treatment. The sample was then removed, placed in a nitrogen-filled sealed quartz tank, and microwave-treated (irradiation power 800 W) for 7 seconds to obtain a maleimide-styrene copolymer-graphene composite aerogel.

[0091] Example 9 20.5 g of water was added to a polytetrafluoroethylene reactor with an inner vessel, followed by 4 g of 25% mass fraction ammonia water and 0.5 g of maleic anhydride-styrene copolymer. The reactor was placed in an oven and maintained at 150°C for 10 hours, after which it was removed to obtain a homogeneous polymer solution.

[0092] 75 g of a 40 mg / ml graphene oxide aqueous solution was added to a reactor, followed by 3 g of ascorbic acid, followed by magnetic stirring at 1,000 rpm for 5 minutes. After uniform mixing, the mixture was quickly poured into a cylindrical mold with a copper base and polytetrafluoroethylene walls. The mold was then placed on a copper column in a liquid nitrogen bath. After pre-freezing, the frozen mixture was placed in a freeze dryer and freeze-dried for 72 hours (below -30 °C and below 10 Pa) to obtain anisotropic water-soluble GO / SMI composite aerogels.

[0093] The aerogel was then placed in a nitrogen-filled polytetrafluoroethylene inner tank, which was then placed in a thermostatic chamber at 200°C for 2 hours for heat treatment. The sample was then removed, placed in a nitrogen-filled sealed quartz tank, and microwave-treated (irradiation power 500 W) for 3 seconds to obtain a maleimide-styrene copolymer-graphene composite aerogel.

[0094] 0.2 g of maleimide-based polymer aerogel was added to a 30 ml polytetrafluoroethylene beaker containing 20 g of sliced ​​paraffin. The beaker was placed in a vacuum oven and heated to 100 °C for 2 hours to obtain an aerogel phase-change composite. The aerogel phase-change composite was removed from the beaker and wiped to remove excess phase-change material from the surface of the aerogel phase-change composite. The composite was then left at room temperature for 2 hours and weighed to obtain a copolymer-graphene aerogel phase-change composite (approximately 4 g of paraffin adsorbed).

[0095] Example 10 91.5 g of water was added to a capped glass bottle, followed by 3.5 g of 25% mass fraction ammonia water and 5 g of maleic anhydride-styrene copolymer. After tightly tightening the cap, the glass bottle was placed in an oven and kept at 95°C for 4 hours. After removal, a homogeneous polymer solution with a mass fraction of 5% was obtained. This polymer solution was dried at room temperature to obtain a polymer containing maleamic acid groups and ammonium maleate groups.

[0096] The resulting polymer was added to a capped glass bottle, followed by 41.5 g of water and 0.04 g of 25% ammonia water. After tightly fastening the cap, the glass bottle was placed in an oven and kept at 20°C for 0.5 hours, after which it was removed to obtain a homogeneous polymer solution.

[0097] 50 g of a 6 mg / ml graphene oxide aqueous solution was added to a glass bottle, followed by 0.9 g of ascorbic acid, followed by magnetic stirring at 1,000 rpm for 5 minutes. After uniform mixing, the mixture was quickly poured into a cylindrical mold with a copper base and polytetrafluoroethylene walls. The mold was then placed on a copper column in a liquid nitrogen bath. After pre-freezing, the frozen mixture was placed in a freeze dryer and freeze-dried for 72 hours (below -30 °C and below 10 Pa) to obtain anisotropic water-soluble GO / SMI composite aerogels.

[0098] The aerogel was then placed in a nitrogen-filled polytetrafluoroethylene inner tank, which was then placed in a thermostatic chamber at 130°C for 2 hours for heat treatment. The sample was then removed, placed in a nitrogen-filled sealed quartz tank, and microwave-treated (irradiation power 2000 W) for 3 seconds to obtain a maleimide-styrene copolymer-graphene composite aerogel.

[0099] 0.2 g of maleimide-based polymer aerogel was added to a 30 ml polytetrafluoroethylene beaker containing 20 g of sliced ​​paraffin. The beaker was placed in a vacuum oven and heated to 100 °C for 2 hours to obtain an aerogel phase-change composite. After removing the aerogel phase-change composite from the beaker, it was wiped to remove excess phase-change material from the surface of the aerogel phase-change composite. It was then left at room temperature for 2 hours and weighed to obtain a copolymer-graphene aerogel phase-change composite (approximately 6 g of paraffin adsorbed).

[0100] The phase transition temperature and latent heat of phase transition are the same as those in Example 2.

[0101] Comparative Example 1 91.5 g of water was added to a capped glass bottle, followed by 3.5 g of 25% aqueous ammonia and 5 g of maleic anhydride-styrene copolymer. After the cap was tightly fastened, the glass bottle was placed in an oven and kept at 95°C for 4 hours. After that, a homogeneous polymer solution with a mass fraction of 5% was obtained.

[0102] After pouring 15 ml of the polymer solution into each of six molds, the samples were frozen in a refrigerator at -30°C for two hours. The frozen samples were transferred to a freeze dryer and freeze-dried for 72 hours (temperature below -30°C and pressure below 10 Pa) to obtain a water-soluble polymer aerogel. This water-soluble polymer aerogel was then placed in an incubator at 180°C and heat-treated for two hours to dehydrate and deamidate the maleimide-based aerogel.

[0103] Comparative Example 2 A 30 ml polytetrafluoroethylene beaker containing 20 g of sliced ​​paraffin was placed in a vacuum oven and kept at 100° C. for 2 hours. After removing the material, it was kept at room temperature for 2 hours to obtain a paraffin phase change material (i.e., a pure phase change material).

[0104] Test Example I of the aerogels prepared in Examples 1 and 6 to 8 D / I G The test results are shown in Table 1, and the leakage status of the phase change materials prepared in Example 2, Comparative Example 2, and Example 5 is shown in Table 2; the DSC curves and glass transition temperatures Tg of Comparative Example 1 and Example 4 are shown in Figure 1; the thermogravimetric curves of Comparative Example 1 and Example 4 are shown in Figure 2; and the temperature curves of the phase change materials of Example 2 and Example 5 under 1 solar illumination intensity and after removal of illumination are shown in Figure 3.

[0105] The test results in Figure 3 show that graphene imparts photothermal conversion functionality to the phase-change material, and the graphene-containing aerogel phase-change composite can be heated to above 70°C within 30 minutes and maintain a temperature above 50°C for a long period of time, demonstrating excellent photothermal conversion performance and enabling highly efficient utilization of solar energy. The phase-change composite of Example 6 was also tested in the same manner. A comparison of Example 2 and Example 6 reveals that the photothermal conversion performance of the phase-change composite of Example 2 is superior to that of the phase-change composite of Example 6.

[0106] [Table 2] The test results in Table 1 show that the composite aerogel prepared in the present invention has high reduction efficiency and can reach a high reduction degree within 3 seconds, which is beneficial for rapid large-scale industrial preparation.

[0107] [Table 3] The test results in Table 2 show that the aerogel has a good effect on preventing leakage of the phase change material, and has good prospects for use.

[0108] [Table 4] The data in Table 3 show that porous aerogels cause little loss of latent heat in the phase change material, that different organic phase change materials can be used to prepare phase change composites with high latent heat values, and that the addition of aerogels can slightly decrease the melting and solidification temperatures of the phase change material.

[0109] It should be noted that the above-described examples are merely used to illustrate the present invention and do not constitute any limitation of the present invention. While the present invention has been described with reference to exemplary embodiments, it should be understood that the terms used herein are descriptive and exemplary, rather than limiting. Changes may be made to the present invention within the scope of the claims, and modifications may be made to the present invention without departing from the scope and spirit of the present invention. While the present invention described herein relates to specific methods, materials, and examples, it is not intended that the present invention be limited to the specific examples disclosed herein. On the contrary, the present invention extends to all other methods and uses having the same functions.

[0110] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference in their entirety.Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art.In the event of any discrepancy, the definitions in this specification shall prevail.

[0111] When materials, substances, methods, processes, devices, components, and the like are referred to in this specification using prefixes such as "known to those skilled in the art" or "prior art," the subject matter so referred to encompasses not only those commonly used in the art at the time of the filing of this application, but also those that are not currently in common use but would be recognized in the art as being suitable for a similar purpose.

[0112] The range endpoints and any values ​​disclosed in this application document are not limited to exact ranges or values, and these ranges or values ​​should be understood to encompass values ​​close to these ranges or values.For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these should be considered as specifically disclosed herein.In the following text, in principle, various technical solutions can be combined with each other to obtain new technical solutions, and these should also be considered as specifically disclosed herein.

[0113] In the context of this specification, for matters or issues not mentioned, what is known in the art shall apply unchanged, unless expressly stated otherwise.

[0114] Furthermore, any embodiment described in this specification can be freely combined with one or more other embodiments described in this specification, and any resulting technical solutions or technical concepts shall be deemed to be part of the original disclosure or original description of the present invention, and shall not be deemed to be new content not disclosed or contemplated in this specification, unless a person skilled in the art would consider the combination to be obviously unreasonable. [Brief explanation of the drawings]

[0115] [Figure 1]1 shows the DSC curves and glass transition temperatures Tg of the maleimide-based aerogel of Comparative Example 1 and the recycled polymer aerogel of Example 4. [Figure 2] 1 shows the thermogravimetric curves of the maleimide-based aerogel of Comparative Example 1 and the recycled polymer aerogel of Example 4. [Figure 3] 1 shows the temperature curves of the phase change materials of Examples 2 and 5 under one solar illumination intensity and after illumination is removed. [Figure 4] FIG. 1 shows the recycling of the maleimide copolymer-graphene aerogel phase change composite (a) obtained in Example 2, and the graphene phase change composite (b) and polymer aerogel (c) obtained by the recycling, as described in Example 4.

Claims

1. A composite aerogel comprising a polymer and graphene, wherein the polymer contains a maleic anhydride group-containing structural unit and a maleimide group-containing structural unit, and the maleic anhydride group is 【Chemical 1】 wherein the maleimide group is 【Chemistry 2】 This refers to composite aerogel.

2. I in the Raman spectrum of the surface of the composite aerogel Ｄ / I Ｇ is 1.2 or less, preferably 0.9 or less, more preferably 0.85 or less; and / or 2. The composite aerogel of claim 1, wherein the mass ratio of the graphene to the polymer is from 1:20 to 10:1, preferably from 1:10 to 6:1, and more preferably from 1:5 to 1:

1.

3. The polymer in the composite aerogel can be dissolved in ammonia water at 0°C to 150°C to form an aqueous polymer solution; and / or The graphene is obtained by reducing graphene oxide, preferably by first pre-reducing the graphene oxide with a reducing agent and then reducing it under microwaves; more preferably 2. The composite aerogel according to claim 1, wherein the reducing agent is selected from at least one of ascorbic acid, gallic acid, sodium borohydride, and amino acids.

4. 2. The composite aerogel according to claim 1, wherein a molar ratio of the maleimide group-containing structural unit in the polymer is 5% to 70%, preferably 10% to 60%, and more preferably 20% to 50%, relative to the total molar amount of the maleic anhydride group-containing structural unit and the maleimide group-containing structural unit, which is 100%.

5. 2. The composite aerogel of claim 1, wherein the polymer is derived from a polymer raw material containing one or more of a maleic anhydride group-containing structural unit, a maleimide group-containing structural unit, a structural unit containing a group of maleic acid and its ammonium salt, and a structural unit containing a group of maleamic acid and its ammonium salt; preferably, the polymer raw material is a copolymer of a polymerizable monomer containing one or more of maleic anhydride, maleimide, maleic acid and its ammonium salt, and maleamic acid and its ammonium salt, with an olefin monomer; more preferably, the olefin monomer is at least one of α-methylstyrene, styrene, and isobutylene.

6. 6. The composite aerogel according to claim 1, wherein the composite aerogel is prepared by reacting a polymer raw material containing one or more of a maleic anhydride group-containing structural unit, a maleimide group-containing structural unit, a structural unit containing a maleic acid and its ammonium salt group, and a structural unit containing a maleamic acid and its ammonium salt group with aqueous ammonia under sealed conditions, followed by mixing with graphene oxide and a reducing agent, pre-freezing, freeze-drying, dehydration and deamination, and reduction.

7. 7. A method for preparing the composite aerogel according to claim 1, comprising reacting a polymer raw material containing one or more of a maleic anhydride group-containing structural unit, a maleimide group-containing structural unit, a structural unit containing a maleic acid and its ammonium salt group, and a structural unit containing a maleamic acid and its ammonium salt group with aqueous ammonia under sealed conditions, mixing the resulting polymer with graphene oxide and a reducing agent, and then pre-freezing, freeze-drying, dehydrating and deaminating the resulting polymer, and reducing the resulting polymer to obtain a composite aerogel.

8. The following steps: (1) reacting the polymer raw material with aqueous ammonia under a sealed condition to obtain an aqueous polymer solution; (2) mixing the aqueous polymer solution obtained in step (1) with graphene oxide and a reducing agent to obtain a mixed solution, and then pre-freezing and freeze-drying the mixed solution to obtain a composite polymer; 8. The method according to claim 7, further comprising: (3) heat-treating the composite polymer obtained in step (2) and then irradiating it with microwaves to obtain a composite aerogel.

9. In step (1): With the total mass of the reaction system being 100%, the mass fraction of the polymer raw material is 0.1% to 30%, preferably 0.5% to 10%, more preferably 1% to 5%, and the mass fraction of ammonia relative to the mass of ammonia in the ammonia water is 0.001% to 30%, preferably 0.01% to 10%, more preferably 0.1% to 1%, with the remainder being water; and / or The reaction conditions are:

9. The preparation method according to claim 8, characterized in that the reaction temperature is 0°C to 200°C, preferably 50°C to 150°C, more preferably 80°C to 100°C, and / or the reaction time is 0.01 hours to 100 hours, preferably 0.5 hours to 10 hours, more preferably 1 hour to 5 hours.

10. In step (2): the graphene oxide is derived from a dispersion containing the graphene oxide, and the concentration of the graphene oxide in the dispersion is from 1 mg / mL to 100 mg / mL, preferably from 3 mg / mL to 30 mg / mL, more preferably from 5 mg / mL to 20 mg / mL; and / or the reducing agent is selected from at least one of ascorbic acid, gallic acid, sodium borohydride, and an amino acid; and / or The mass ratio of the reducing agent to the graphene oxide is 1:(0.1-20), preferably 1:(1-3); and / or The cold source temperatures in various directions of the mixture during pre-freezing are the same or different, preferably the cold source temperatures in various directions of the mixture during pre-freezing are different; more preferably the cold source temperatures in a single direction of the mixture during pre-freezing are different; and / or The preparation method according to claim 8, wherein the freeze-drying conditions include: a temperature of -10°C or lower and / or a vacuum of 1000 Pa or lower.

11. In step (3): The heat treatment conditions include: a temperature of 100°C to 300°C, preferably 120°C to 220°C, more preferably 160°C to 200°C; and a heat treatment time of 0.1 hours to 10 hours, preferably 0.5 hours to 3 hours, more preferably 1 hour to 2 hours; and / or The preparation method according to claim 8, characterized in that the power of the microwave irradiation is 500 W to 2000 W; and the time of the microwave irradiation is 1 second to 10 seconds, preferably 2 seconds to 7 seconds, more preferably 3 seconds to 5 seconds.

12. The polymer raw material may be reacted with aqueous ammonia to obtain a water-soluble polymer; and / or The polymer raw material is a copolymer of a polymerizable monomer including one or more of maleic anhydride, maleimide, maleic acid and its ammonium salt, and maleamic acid and its ammonium salt, and an olefin monomer; more preferably, the olefin monomer includes at least one of α-methylstyrene, styrene, and isobutylene; The preparation method according to any one of claims 7 to 11, characterized in that the polymer raw material is preferably at least one of styrene-maleic anhydride copolymer, maleic anhydride-isobutylene copolymer.

13. a composite aerogel and a phase change material supported on the composite aerogel; A recyclable heat storage phase change composite material, wherein the composite aerogel is the composite aerogel according to any one of claims 1 to 6, or a composite aerogel prepared by the preparation method according to any one of claims 7 to 12.

14. The mass ratio of the composite aerogel to the phase change material is 1:(0.05-50); and / or the phase change material is an organic phase change material, preferably a water-soluble and / or water-insoluble phase change material, more preferably at least one of polyethylene glycol, lauric acid, stearyl alcohol, and paraffin; and / or The recyclable heat storage phase change composite material of claim 13, characterized in that under temperature conditions in which the phase change material is in a liquid state, the leakage rate of the phase change material in the recyclable heat storage phase change composite material is less than 10 wt%, preferably less than 5 wt%, and more preferably less than 2 wt%.

15. 15. A method for preparing the recyclable heat storage phase change composite material according to claim 13 or 14, comprising: loading the phase change material onto the composite aerogel; Preferably, the method for preparing the recyclable heat storage phase change composite material includes: obtaining a composite aerogel using the method according to any one of claims 7 to 12; and supporting the phase change material on the composite aerogel.

16. 15. Use of the recyclable heat storage phase change composite material according to claim 13 or 14 in the fields of building energy saving, air conditioning systems, waste heat utilization and solar energy storage.

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