High-stability photo-thermal phase change energy storage material as well as preparation method and application thereof
By introducing nitrate into graphene-PEG aerogel, a porous structure is formed and the pore channels are closed at high temperatures, the leakage problem of GA/PEG materials is solved, high stability and excellent thermal management effects are achieved, and the overall performance and safety of the composite material are improved.
Patent Information
- Application Number
- CN202510523685.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-29
AI Technical Summary
Existing GA/PEG-based photothermal phase change materials are prone to leak after melting at high temperatures, resulting in low usage stability and poor thermal management effect.
Nitrate is introduced into graphene-PEG aerogel, and porous structure is formed through rapid freezing and lyophilization treatment. Nitrate is used to form eutectic salt to seal the pores at high temperature to prevent PEG leakage and absorb heat, and improve material stability.
It significantly improves the stability and thermal management effect of photothermal phase change energy storage materials, prevents PEG leakage, realizes heat regulation under high temperature conditions, and enhances the overall performance and safety of composite materials.
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Figure CN120383918A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of photothermal phase change energy storage materials, and particularly relates to a highly stable photothermal phase change energy storage material, its preparation method and application. Background Art
[0002] In heavy industrial fields such as steel, cement, and glass manufacturing, a large amount of thermal energy generated by high-temperature processes is often not fully utilized, resulting in huge energy waste. Phase change energy storage materials absorb high-temperature waste heat during industrial production processes and release the heat in a controllable manner when needed, which can be used in production processes or converted into electrical energy. Through the recycling of thermal energy by phase change materials, not only can the energy utilization efficiency be improved, but it also helps to reduce the carbon emissions of industrial production and support the sustainable development goals.
[0003] With the rapid development of energy storage technologies, phase change energy storage materials have received extensive attention due to their application potential in medium and high-temperature thermal energy storage fields. Researchers such as Wang developed a new type of phase change energy storage material by combining porous silica with PEG. The main component of this material is PEG-4000. By filling PEG-4000 into porous silica, not only the thermal conductivity and heat transfer characteristics of the material are improved, but also the heat storage density is significantly increased due to its open structure with high porosity. This material is widely used in low-temperature thermal energy storage due to its suitable melting point, high energy storage density, low cost, and excellent thermal stability. Researchers such as Li prepared an efficient phase change energy storage material by combining porous aluminum oxide with PEG. Its main component is PEG-6000. By infiltrating PEG-6000 into porous aluminum oxide, the material has been significantly improved in terms of thermal conductivity and heat transfer characteristics, and its heat storage capacity has been enhanced through the open porous structure. This polymer has received attention due to its moderate melting point and high energy storage density.
[0004] Although traditional GA / PEG composite materials have excellent performance as photothermal phase change materials and have good heat storage and heat release capabilities, however, such materials have some defects, that is, they are prone to leakage after PEG melts, seriously affecting their use stability and thermal management effect. Summary of the Invention
[0005] This application provides a highly stable photothermal phase change energy storage material, its preparation method and application, aiming to solve the technical problems of low use stability and poor thermal management effect of existing GA / PEG-based photothermal phase change materials due to easy leakage after high-temperature melting.
[0006] To achieve the above objectives, this application adopts the following technical solutions to be realized.
[0007] In the first aspect of the present application, a preparation method of a highly stable photothermal phase change energy storage material is provided, including:
[0008] S1, adding few-layer graphene oxide, PEG, sodium ascorbate and nitrate into water, stirring evenly to obtain a slurry;
[0009] S2, quickly freezing the slurry and performing freeze-drying treatment to obtain a hardened body;
[0010] S3, performing heat treatment on the hardened body to obtain a highly stable photothermal phase change energy storage material.
[0011] Preferably, in the slurry, the content of few-layer graphene oxide is 40 - 60 mg / mL; the concentration of PEG-4000 is 150 - 300 mg / mL; the concentration of sodium ascorbate is 0.4 - 0.6 mg / mL; the concentration of nitrate is 250 mg / mL.
[0012] Preferably, the nitrate is a mixture of sodium nitrate and potassium nitrate with a mass ratio of 3:2.
[0013] Preferably, the PEG is PEG4000.
[0014] Preferably, the quick freezing includes: injecting the slurry into a mold, and performing orientation freezing on the mold from bottom to top with liquid nitrogen, and the freezing time is 10 - 15 min.
[0015] Preferably, the temperature of the freeze-drying treatment is -70 - -80 °C, the vacuum degree < 15 Pa, and the freeze-drying time is 24 - 48 h.
[0016] Preferably, the temperature of the heat treatment is 90 - 150 °C, and the heat treatment time is 2 - 4 h.
[0017] Preferably, the few-layer graphene oxide is prepared by the following method:
[0018] Mixing graphite and sulfuric acid evenly, adding sodium nitrate and phosphorus pentoxide, stirring at 80 - 100 °C for 12 - 24 h, separating and collecting the solid phase, washing and air-drying to obtain a precursor;
[0019] Dispersing the precursor in excessive concentrated sulfuric acid, and slowly adding potassium permanganate thereto, stirring at -10 - 0 °C, then adding water for dilution, then heating to 90 °C, and adding hydrogen peroxide until the solution turns bright yellow to obtain a dispersion;
[0020] Diluting the dispersion with water, centrifuging at a speed of 5000 - 7000 r / min to remove multi-layer graphene oxide, and then centrifuging at a speed of 10000 - 12000 r / min to remove impurities, and freeze-drying the centrifuged concentrated solution to obtain few-layer graphene oxide.
[0021] In the second aspect of the present application, there is provided a highly stable photothermal phase change energy storage material prepared by the above preparation method.
[0022] In the third aspect of the present application, there is provided the application of the above highly stable photothermal phase change energy storage material in phase change energy storage.
[0023] Compared with the prior art, the beneficial effects of the present application are as follows:
[0024] The present application prepares a highly stable photothermal phase change energy storage material by introducing nitrates (60% sodium nitrate and 40% potassium nitrate) into graphene-PEG aerogel. On the one hand, when PEG melts, the nitrates can effectively seal the porous structure inside the graphene aerogel to prevent the molten PEG from leaking; secondly, the eutectic salt formed by the nitrates when the material temperature exceeds 210°C will melt and is not easy to seep out due to the large contact angle with graphene. At the same time, it absorbs heat to slow down the temperature rise, thereby preventing PEG from decomposing due to excessive temperature. The highly stable photothermal phase change energy storage material of the present application not only makes up for the shortcoming of leakage of traditional GA / PEG materials, but also realizes effective regulation of heat under high-temperature conditions, achieving two goals at once, significantly improving the overall performance and safety of the composite material, and having high stability and excellent thermal management effect. Description of the Drawings
[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0026] Figure 1 It is the DSC test chart of the GA / PEG / MS composite photothermal phase change energy storage material of the present application;
[0027] Figure 2 It is the SEM chart of the GA / PEG / MS composite photothermal phase change energy storage material of the present application;
[0028] Figure 3 It is the cyclic stability test result chart of the GA / PEG / MS composite photothermal phase change energy storage material of the present application;
[0029] Figure 4 It is the physical diagram of the stability test of the composite photothermal phase change energy storage material of the present application and the comparative example. Detailed Embodiments
[0030] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.
[0031] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, that is, they are intended to include but not limited to.
[0032] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and both A and B exist simultaneously. Where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are an "or" relationship.
[0033] In the following description of this embodiment, the term "at least one" means one or more, and "a plurality" means two or more. "At least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single items (pieces) or plural items (pieces). For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both mean: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.
[0034] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.
[0035] Those skilled in the art should understand that in the following description of the embodiments of the present application, the sequence numbers do not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.
[0036] Those skilled in the art should understand that the numerical ranges in the embodiments of the present application should be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present application. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.
[0037] Unless otherwise specified, the technical / scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.
[0038] In a first aspect, this application provides a method for preparing a high-stability photothermal phase change energy storage material, comprising:
[0039] S1. Add few-layer graphene oxide, PEG, sodium ascorbate, and nitrate into water, and stir evenly to obtain a slurry; wherein, preferably, the stirring temperature is 80 - 90 °C, and the stirring time is 24 - 72 h.
[0040] The slurry of this application uses polyethylene glycol as the main solvent. The relatively high melting point and faster solidification rate of polyethylene glycol help prevent organic phase separation during the freezing process, ensuring the uniformity and stability of the material; sodium ascorbate is used to adjust the self-assembly degree of graphene oxide; the PEG is preferably PEG4000; the nitrate is preferably a mixture of sodium nitrate and potassium nitrate with a mass ratio of 3:2.
[0041] In the slurry of this application, the content of few-layer graphene oxide is 40 - 60 mg / mL; the concentration of PEG-4000 is 150 - 300 mg / mL; the concentration of sodium ascorbate is 0.4 - 0.6 mg / mL; the concentration of nitrate is 250 mg / mL.
[0042] S2. Rapidly freeze the slurry and perform freeze-drying treatment to obtain a hardened body;
[0043] In this application, inject the slurry into a mold, and perform orientation freezing on the mold from bottom to top with liquid nitrogen. Among them, the freezing time is 10 - 15 min, and the diameter of the mold is preferably 3 - 10 cm. Rapidly freeze the slurry with liquid nitrogen to make it arranged directionally from bottom to top.
[0044] After rapid freezing with liquid nitrogen, perform freeze-drying treatment to form a hardened body with a uniform porous structure. Among them, the temperature of the freeze-drying treatment is -70 - -80 °C, the vacuum degree < 15 Pa, and the freeze-drying time is 24 - 48 h.
[0045] S3. Perform heat treatment on the hardened body to obtain a high-stability photothermal phase change energy storage material.
[0046] In this application, the temperature of the heat treatment is 90 - 150 °C, and the time of the heat treatment is 2 - 4 h. By performing heat treatment on the hardened body, PEG is fully melted and uniformly dispersed throughout the hardened body. During the heat treatment process, sodium nitrate and potassium nitrate act synergistically on the pores inside the hardened body to block the pore channels and prevent the leakage of PEG, thereby obtaining a GA / PEG / MS composite material with excellent stability, that is, a high-stability photothermal phase change energy storage material.
[0047] In this application, according to the specific concentrations of graphene oxide and PEG, the heating temperature and time can be appropriately adjusted to achieve the best composite material performance.
[0048] This application prepares a high-stability photothermal phase change energy storage material by introducing nitrates (60% sodium nitrate and 40% potassium nitrate) into the graphene-PEG aerogel. On the one hand, the nitrates can effectively block the porous structure inside the graphene aerogel when PEG melts, preventing the leakage of molten PEG; on the other hand, the eutectic salt formed by the nitrates when the material temperature exceeds 210 °C will melt, and it is not easy to seep out due to the large contact angle with graphene. At the same time, it absorbs heat to slow down the temperature rise, thereby preventing the decomposition of PEG due to excessive temperature.
[0049] In this application, the few-layer graphene oxide is prepared by the improved Hummers method, specifically as follows:
[0050] Mix graphite and sulfuric acid evenly, add sodium nitrate and phosphorus pentoxide, stir at 80 - 100 °C for 12 - 24 h, separate and collect the solid phase by suction filtration, and air-dry to obtain the precursor; among them, graphite is preferably flake graphite;
[0051] Specifically, it is preferred that the mass ratio of the graphite, sulfuric acid, sodium nitrate, and phosphorus pentoxide is (1 - 2):(18 - 20):(1.5 - 2):(1.5 - 2).
[0052] Disperse the precursor in excessive concentrated sulfuric acid, and slowly add potassium permanganate thereto, stir at -10 - 0 °C for 4 - 5 h, then raise the temperature to 30 - 40 °C, add water for dilution, then raise the temperature to 90 °C, add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion;
[0053] Among them, the mass ratio of the potassium permanganate to the graphite is 5:1.
[0054] Dilute the dispersion with water, centrifuge to remove multi-layer graphene oxide at a speed of 5000 - 7000 r / min, and then centrifuge to remove impurities at a speed of 10000 - 12000 r / min. Freeze-dry the centrifuged concentrated solution to obtain few-layer graphene oxide.
[0055] The highly stable photothermal phase change energy storage material prepared in this application not only makes up for the shortcoming of leakage of traditional GA / PEG materials, but also realizes effective regulation of heat under high-temperature conditions, significantly improving the overall performance and safety of the composite material, and having high stability and excellent heat management effects.
[0056] The highly stable photothermal phase change energy storage material prepared in this application can be used as a phase change energy storage material or for preparing a phase change energy storage material for energy storage, such as phase change energy storage in heavy industrial fields such as steel, cement, and glass manufacturing, as well as in fields such as power generation, solar power generation, and waste heat recovery systems, and has broad market potential.
[0057] The following further illustrates this application through examples.
[0058] Example 1
[0059] This example provides a preparation method for a highly stable photothermal phase change energy storage material, including:
[0060] 1) Preparation of few-layer graphene oxide:
[0061] Mix 2 g of flake graphite with 10 ml of sulfuric acid, stir at 80 °C, then sequentially add 1.7 g of sodium nitrate and 1.7 phosphorus pentoxide, and continuously stir for 12 hours; filter the mixture twice and air-dry it at room temperature for 3 hours to obtain a precursor.
[0062] Add 80 ml of sulfuric acid to a beaker, add the precursor, slowly add 10 g of potassium permanganate to the beaker at -10 °C, stir for 4.5 hours, then treat it in a 35 °C water bath for 4 hours, dilute it in 1000 ml of water, and stir for 15 minutes; raise the temperature to 90 °C and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at a speed of 6000 r / min for 5 min to remove multi-layer graphene oxide, and then centrifuge it at a speed of 11000 r / min for 15 min to remove impurities to obtain a concentrated solution. Freeze-dry the concentrated solution for 48 hours to obtain few-layer graphene oxide.
[0063] 2) Preparation of highly stable photothermal phase change energy storage material:
[0064] Mix few-layer graphene oxide, PEG, and sodium ascorbate in water, add 3 g of sodium nitrate and 2 g of potassium nitrate, and mix well; among them, the concentration of graphene oxide is 40 mg / mL, the concentration of PEG is 150 mg / mL, the concentration of sodium ascorbate is 0.4 mg / mL, the concentration of sodium nitrate is 150 mg / mL, and the concentration of potassium nitrate is 100 mg / mL. Continuously stir it at 80 °C for 48 hours until a uniform slurry is formed.
[0065] Pour the slurry into a mold with a diameter of 3 cm, and quickly freeze the slurry with liquid nitrogen to make the slurry arranged directionally from bottom to top. After freezing, place the mold in a freeze dryer, set the temperature to -70 °C, the vacuum degree < 15 Pa, and perform freeze-drying treatment for 48 h to obtain a hardened body with a uniform porous structure.
[0066] Place the hardened body in a heating device and heat it at 90 °C for 2 hours to ensure that PEG-4000 is fully melted and uniformly dispersed in the hardened body, obtaining the GA / PEG / MS composite photothermal phase change energy storage material.
[0067] Example 2
[0068] 1) Prepare few-layer graphene oxide:
[0069] Mix 2 g of flake graphite with 10 ml of sulfuric acid, stir at 80 °C, and then add 1.7 g of sodium nitrate and 1.7 phosphorus pentoxide in sequence, and continue stirring for 12 hours; filter the mixture by suction twice and air-dry it at room temperature for 3 hours to obtain a precursor.
[0070] Add 80 ml of sulfuric acid to a beaker, add the precursor, slowly add 10 g of potassium permanganate to the beaker at -10 °C, stir for 4.5 hours, then treat it in a water bath at 35 °C for 4 hours, dilute it in 1000 ml of water, and stir for 15 minutes; raise the temperature to 90 °C and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at a speed of 5000 r / min for 5 min to remove multi-layer graphene oxide, and then centrifuge it at a speed of 11000 r / min for 15 min to remove impurities to obtain a concentrated solution. Freeze-dry the concentrated solution for 48 hours to obtain few-layer graphene oxide.
[0071] 2) Prepare a highly stable photothermal phase change energy storage material:
[0072] Mix few-layer graphene oxide, PEG, and sodium ascorbate in water, add 3 g of sodium nitrate and 2 g of potassium nitrate, and mix them evenly; among them, the concentration of graphene oxide is 40 mg / mL, the concentration of PEG is 200 mg / mL, the concentration of sodium ascorbate is 0.6 mg / mL, the concentration of sodium nitrate is 150 mg / mL, and the concentration of potassium nitrate is 100 mg / mL. Stir it continuously at 80 °C for 48 hours until a uniform slurry is formed.
[0073] Pour the slurry into a mold with a diameter of 5 cm, and quickly freeze the slurry with liquid nitrogen to make the slurry arranged directionally from bottom to top. After freezing, place the mold in a freeze dryer, set the temperature to -70 °C, the vacuum degree < 15 Pa, and perform freeze-drying treatment for 48 h to obtain a hardened body with a uniform porous structure.
[0074] Place the hardened body in a heating device and heat it at 120 °C for 2 hours to ensure that PEG-4000 is fully melted and uniformly dispersed in the hardened body, obtaining the GA / PEG / MS composite photothermal phase change energy storage material.
[0075] Example 3
[0076] 1) Prepare few-layer graphene oxide:
[0077] Mix 2 g of flake graphite with 10 ml of sulfuric acid, stir at 80 °C, and then sequentially add 1.7 g of sodium nitrate and 1.7 phosphorus pentoxide, and continuously stir for 12 hours; filter the mixture by suction twice and air-dry it at room temperature for 3 hours to obtain the precursor.
[0078] Add 80 ml of sulfuric acid to a beaker, add the precursor, and slowly add 10 g of potassium permanganate to the beaker at -10 °C, stir for 4.5 hours, then treat it in a water bath at 35 °C for 4 hours, dilute it in 1000 ml of water, and stir for 15 minutes; raise the temperature to 90 °C and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at a speed of 4500 r / min for 5 min to remove multi-layer graphene oxide, and then centrifuge it at a speed of 11000 r / min for 15 min to remove impurities to obtain a concentrated solution. Freeze-dry the concentrated solution for 48 hours to obtain few-layer graphene oxide.
[0079] 2) Prepare a highly stable photothermal phase change energy storage material:
[0080] Mix few-layer graphene oxide, PEG, and sodium ascorbate in water, add 3 g of sodium nitrate and 2 g of potassium nitrate, and mix well; among them, the concentration of graphene oxide is 60 mg / mL, the concentration of PEG is 250 mg / mL, the concentration of sodium ascorbate is 0.5 mg / mL, the concentration of sodium nitrate is 150 mg / mL, and the concentration of potassium nitrate is 100 mg / mL. Continuously stir it at 80 °C for 48 hours until a uniform slurry is formed.
[0081] Pour the slurry into a mold with a diameter of 8 cm, quickly freeze the slurry with liquid nitrogen to make the slurry arrange directionally from bottom to top. After freezing, place the mold in a freeze dryer, set the temperature to -70 °C, the vacuum degree < 15 Pa, and perform freeze-drying treatment for 48 h to obtain a hardened body with a uniform porous structure.
[0082] Place the hardened body in a heating device and heat it at 150 °C for 2 hours to ensure that PEG-4000 is fully melted and uniformly dispersed in the hardened body, obtaining the GA / PEG / MS composite photothermal phase change energy storage material.
[0083] Comparative Example 1
[0084] The difference between Comparative Example 1 and Example 1 is that in step 2) for preparing the highly stable photothermal phase change energy storage material, sodium nitrate and potassium nitrate are absent, and the rest are the same as in Example 1.
[0085] The GA / PEG / MS composite photothermal phase change energy storage material prepared in Example 1 was subjected to morphology testing and performance evaluation, and the DSC test results are as Figure 1 shown. It can be clearly observed from Figure 1 that there are two heat absorption peaks, corresponding to the phase change behaviors of PEG and molten nitrate, respectively. Among them, an obvious endothermic peak appears at about 57.2 °C, and the melting enthalpy is 111.3 J / g. This peak belongs to the melting process of polyethylene glycol (PEG), indicating that PEG still maintains good crystallinity and reversible phase change performance in this composite material. And a second endothermic peak is observed in the higher temperature region (about 221.9 °C), with a corresponding melting enthalpy of 47.7 J / g. This peak comes from the melting behavior of the NaNO3-KNO3 eutectic salt in the composite material. This bimodal structure clearly shows that the GA / PEG / MS composite photothermal phase change energy storage material realizes the synergistic heat storage mechanism of organic (PEG) and inorganic (nitrate) phase change components, has multi-stage energy storage ability, and while maintaining the low-temperature heat storage ability of PEG, uses nitrate for heat storage protection in the high-temperature region.
[0086] The SEM image of the GA / PEG / MS composite photothermal phase change energy storage material prepared in Example 1 is as Figure 2 shown. It can be observed from Figure 2 that the overall material presents a porous three-dimensional network structure, and rich pores are formed between the graphene sheets, which is beneficial to the effective loading of the phase change material (PEG) and inorganic salts. It can be seen from Figure 2 that there are agglomerated or covered particles in some pores, presumably NaNO3-KNO3 salt particles distributed in the pores or on the surface. The presence of these salts not only enhances the structural stability of the composite material, but also plugs the pores to a certain extent, effectively inhibiting the leakage of PEG in the molten state, thus significantly improving the shape stability of the phase change material. In addition, at high temperatures, the inorganic salts have good thermal stability and can protect PEG, further improving the thermal cycling durability and high-temperature performance retention ability of the composite material.
[0087] The cycle stability of the GA / PEG / MS composite photothermal phase change energy storage material prepared in Example 1 was evaluated by conducting multiple heating-cooling cycle tests and recording the changes in the phase change enthalpy values. The test results are as Figure 3As shown. The initial melting enthalpy is 159 J / g. As the number of cycles increases, the enthalpy value shows a gradually decreasing trend. By the 50th cycle, the enthalpy value remains at 141 J / g, and the retention rate is approximately 88.7%. Among them, the decrease is relatively large in the early stage. After the first 10 cycles, the melting enthalpy drops to 155 J / g, and then the decrease slows down. The difference between the 40th and 50th cycles is small, indicating that after the initial structural adaptation, the thermal cycling process tends to be stable.
[0088] The test results show that this photothermal phase change energy storage material has good phase change thermal stability and structural integrity, and can still maintain a high heat storage capacity during repeated phase changes. This is mainly due to the three-dimensional network structure constructed by the graphene aerogel providing a stable skeleton support. At the same time, the introduction of inorganic salts effectively seals the pores, inhibits the leakage of PEG, and enhances the overall thermal cycling durability.
[0089] To test the stability of the GA / PEG / MS composite photothermal phase change energy storage material in Test Example 1, the specific method is as follows: The sample is repeatedly subjected to 20 heating-cooling cycles (heating from room temperature to 100 °C and then naturally cooling to room temperature), and its macroscopic morphological changes are observed. The comparative sample is the photothermal phase change energy storage material in Comparative Example 1 that only adds PEG. The results are as Figure 4 shown. Among them, Figure 4 On the left in the figure is the physical picture of the sample in Example 1, and on the right is the physical picture of the sample in Comparative Example 1.
[0090] From Figure 4 it can be seen that the composite material in Example 1 with added nitrate still maintains a good overall morphology after 20 thermal cycles. The surface is relatively flat, without obvious cracks or deformations, showing excellent thermal cycling stability. While the material in Comparative Example 1 that only adds PEG has serious deformations, collapses and even fractures, and the overall structure is basically damaged and it is difficult to maintain its shape. This result shows that nitrate plays a significant supporting and sealing role in the material structure. On the one hand, it effectively prevents the leakage of PEG at high temperatures, and on the other hand, it improves the structural integrity and shape retention ability of the material during thermal cycling, verifying its good stability in actual heat storage applications.
[0091] Although this specification has described the present application in detail with general descriptions and specific embodiments, based on the present application, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope protected by the present application.
Claims
1. A preparation method of a high-stability photothermal phase change energy storage material, characterized in that Comprising: S1, adding few-layer graphene oxide, PEG, sodium ascorbate and nitrate into water, and stirring evenly to obtain a slurry; S2, rapidly freezing the slurry and performing freeze-drying treatment to obtain a hardened body; S3, performing heat treatment on the hardened body to obtain a highly stable photothermal phase change energy storage material.
2. The preparation method according to claim 1, characterized in that, In the slurry, the content of few-layer graphene oxide is 40-60 mg / mL; the concentration of PEG-4000 is 150-300 mg / mL; the concentration of sodium ascorbate is 0.4-0.6 mg / mL; the concentration of nitrate is 250 mg / mL.
3. The preparation method according to claim 1, characterized in that, The nitrate is a mixture of sodium nitrate and potassium nitrate with a mass ratio of 3:
2.
4. The preparation method according to claim 1, characterized in that, The PEG is PEG4000.
5. The preparation method according to claim 1, wherein The rapid freezing includes: Injecting the slurry into a mold, and performing orientation freezing on the mold from bottom to top with liquid nitrogen for 10-15 min.
6. The preparation method according to claim 1, characterized in that, The temperature of the freeze-drying treatment is -70 to -80 °C, the vacuum degree is <15 Pa, and the freeze-drying time is 24-48 h.
7. The preparation method according to claim 1, wherein The temperature of the heat treatment is 90-150 °C; the heat treatment time is 2-4 h.
8. The preparation method of the nitrogen-doped ceramicized graphene aerogel according to claim 1, characterized in that, The few-layer graphene oxide is prepared by the following method: Mixing graphite and sulfuric acid evenly, adding sodium nitrate and phosphorus pentoxide, stirring at 80-100 °C for 12-24 h, separating and collecting the solid phase, washing and air-drying to obtain a precursor; Dispersing the precursor in excessive concentrated sulfuric acid, slowly adding potassium permanganate thereto, stirring at -10-0 °C, then diluting with water, then heating to 90 °C, and adding hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; Diluting the dispersion with water, centrifuging at a speed of 5000-7000 r / min to remove multi-layer graphene oxide, and then centrifuging at a speed of 10000-12000 r / min to remove impurities, and freeze-drying the centrifuged concentrated solution to obtain few-layer graphene oxide.
9. A highly stable photothermal phase change energy storage material prepared by the preparation method according to any one of claims 1-8.
10. Application of the highly stable photothermal phase change energy storage material according to claim 9 in phase change energy storage.