A molten salt phase change energy storage material and its preparation method and application

Abstract

The present application relates to the technical field of molten salt phase change materials, and discloses a molten salt phase change energy storage material, its preparation method and application. The preparation method of the molten salt phase change energy storage material comprises: mixing NaNO3 and KNO3 in a mass ratio of 6:4, grinding and heating to 400°C to melt, cooling and grinding again to obtain a eutectic salt; dispersing a few-layer graphene oxide and sodium ascorbate in water, mixing evenly to obtain a slurry; the slurry is hydrothermally treated and freeze-dried to obtain a graphene aerogel; dissolving the eutectic salt in water to prepare a saturated solution, and impregnating the graphene aerogel in the saturated solution under vacuum; the impregnated product is freeze-dried to obtain a molten salt phase change energy storage material. The present application adopts a vacuum impregnation method to make the molten salt evenly penetrate the pores of the graphene aerogel, and the wetting angle between the graphene and the molten salt is large, which ensures that the molten salt is not easy to leak, further improves the thermal conductivity, and significantly improves the thermal conductivity efficiency and phase change stability.

Description

Technical Field

[0001] The present application relates to the technical field of molten salt phase change materials, and in particular to a molten salt phase change energy storage material and a preparation method and application thereof. Background Art

[0002] In heavy industries like steel, cement, and glass manufacturing, the vast amounts of heat generated by high-temperature processes are often underutilized, resulting in significant energy waste. Recovering and reusing the vast amounts of waste heat generated by industry is becoming a key strategy for energy conservation, emission reduction, and improving energy efficiency.

[0003] In recent years, with the rapid development of energy storage technology, molten salt phase change energy storage materials have received widespread attention due to their application potential in the field of medium and high temperature thermal energy storage. Molten salt phase change energy storage materials provide an effective thermal energy storage and management solution for the above industries due to their ability to work stably in high temperature environments. Molten salt phase change energy storage materials can absorb high-temperature waste heat during industrial production processes and release this heat in a controlled manner when needed, which can be used in the production process or converted into electrical energy. This not only improves energy efficiency, but also helps reduce carbon emissions from industrial production and supports sustainable development goals. In addition to traditional industries, molten salt phase change energy storage technology has also gradually been applied to fields such as power generation, solar power generation, and waste heat recovery systems, showing broad market potential.

[0004] Zhang et al. developed a novel composite phase change material by combining porous ceramics with molten salts. The molten salt is primarily composed of 60% sodium nitrate (NaNO3) and 40% potassium nitrate (KNO3). This mixture is known as "solar salt." Solar salts are widely used in medium- and high-temperature thermal energy storage materials due to their suitable melting point, high energy storage density, low cost, and excellent thermal stability. By infiltrating solar salts into porous silicon carbide (SiC) ceramics, this material not only improves the thermal conductivity and heat transfer properties of the molten salt, but also enhances the heat storage density through its highly porous, open-cell structure. However, porous carbide is not airtight, and the material still suffers from low thermal conductivity and leakage. Xiao et al. developed a novel molten salt / metal foam / graphene nanoparticle phase change composite material. The molten salts used by the research team were primarily HITEC salts and solar salts. The HITEC salt is composed of 40% sodium nitrate (NaNO2), 7% potassium nitrate (KNO3), and 53% potassium nitrate (KNO3). This material combines the high latent heat properties of molten salt and the excellent thermal conductivity of graphene, but it still has problems such as low thermal conductivity and easy leakage. Summary of the Invention

[0005] The present application provides a molten salt phase change energy storage material and its preparation method and application, aiming to solve the technical problems of low thermal conductivity and easy leakage of existing molten salt phase change materials.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions.

[0007] In a first aspect of the present application, a method for preparing a molten salt phase change energy storage material is provided, comprising:

[0008] S1, mixing NaNO3 and KNO3 in a mass ratio of 6:4, grinding, heating to 400℃ to melt, cooling, and grinding again to obtain a eutectic salt;

[0009] S2, dispersing the few-layer graphene oxide and sodium ascorbate in water and mixing them uniformly to obtain a slurry; the slurry is subjected to hydrothermal treatment and then freeze-dried to obtain a graphene aerogel;

[0010] S3, dissolving the eutectic salt in water to prepare a saturated solution, and immersing the graphene aerogel in the saturated solution under vacuum;

[0011] S4, freeze-drying the impregnated product to obtain a molten salt phase change energy storage material.

[0012] In some embodiments, the few-layer graphene oxide is prepared by the following method:

[0013] Mix graphite and sulfuric acid evenly, add sodium nitrate and phosphorus pentoxide, stir at 80-100°C for 12-24 hours, separate and collect the solid phase, wash and air-dry to obtain the precursor;

[0014] The precursor is dispersed in excess concentrated sulfuric acid, and potassium permanganate is slowly added thereto, stirred at -10 to 0°C, and then diluted with water. After that, the temperature is raised to 90°C, and hydrogen peroxide is added until the solution turns bright yellow to obtain a dispersion.

[0015] The dispersion is diluted with water, centrifuged at a speed of 5000-7000 r / min to remove multilayer graphene oxide, and then centrifuged at a speed of 10000-12000 r / min to remove impurities, and the concentrated liquid obtained by centrifugation is freeze-dried to obtain few-layer graphene oxide.

[0016] In some embodiments, the mass ratio of the graphite, sulfuric acid, sodium nitrate and phosphorus pentoxide is (1-2):(18-20):(1.5-2):(1.5-2);

[0017] The mass ratio of the potassium permanganate to the graphite is 5:1.

[0018] In some embodiments, the content of graphene oxide in the slurry is 7-10 mg / mL, and the concentration of sodium ascorbate is 0.2-0.3 mg / mL.

[0019] In some embodiments, the temperature of the hydrothermal treatment is 120-130°C.

[0020] In some embodiments, the freeze-drying in step S2 comprises:

[0021] The slurry after hydrothermal treatment is injected into the mold, and the mold is oriented and frozen from bottom to top using liquid nitrogen for 10 to 15 minutes.

[0022] Then dry it at a temperature of -70 to -80°C and a vacuum degree of <15 Pa for 24 to 48 hours.

[0023] In some embodiments, the temperature of the immersion treatment is 60-80° C., and the pressure is less than 100 Pa.

[0024] In some embodiments, the freeze-drying in step S4 comprises:

[0025] The vacuum impregnation product is frozen by liquid nitrogen for 10 to 15 minutes;

[0026] Then dry it at a temperature of -70 to -80°C and a vacuum degree of <15 Pa for 24 to 48 hours.

[0027] In a second aspect of the present application, a molten salt phase change energy storage material prepared by the above preparation method is provided.

[0028] The third aspect of the present application provides the use of the molten salt phase change energy storage material prepared by the above preparation method in solar thermal power station photothermal storage.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] This application uses graphene aerogel and solar salt as raw materials, and adopts a vacuum impregnation method to prepare graphene-based molten salt phase change energy storage material, so that the molten salt can evenly penetrate the pores of the graphene aerogel. It combines the high porosity of graphene with the phase change energy storage characteristics of molten salt, significantly improving the thermal conductivity and phase change stability. The wetting angle between graphene and molten salt in the molten salt phase change energy storage material is very large, ensuring that the molten salt is not easy to leak, further improving the thermal conductivity, and is particularly suitable for energy storage in electronic equipment and photothermal conversion devices and systems with strict requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some of the embodiments described in this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0032] Figure 1 This is a physical picture of the graphene aerogel prepared in Example 1;

[0033] Figure 2 This is a physical picture of the graphene aerogel after impregnation treatment in Example 1;

[0034] Figure 3 This is a scanning electron microscope image of the molten salt phase change energy storage material of Example 1;

[0035] Figure 4 This is a DSC (differential scanning calorimetry) test result diagram of the molten salt phase change energy storage material of Example 1;

[0036] Figure 5 This is a graph showing the thermal conductivity test results of the graphene aerogel, eutectic salt, and molten salt phase change energy storage material prepared in Example 1. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0038] In the following description of this embodiment, the terms "include", "comprising", "having" and "containing" are open-ended terms, meaning including but not limited to.

[0039] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, B exists alone, and both A and B exist. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0040] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0041] 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", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0042] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0043] It will be understood by those skilled in the art that the numerical ranges in the examples of the present application are to be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. Each smaller range between any intermediate value within a stated value or stated range and 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 may independently be included or excluded in the range.

[0044] Unless otherwise indicated, the technical / scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application belongs. Although this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may 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 documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

[0045] In a first aspect, the present application provides a method for preparing a molten salt phase change energy storage material, comprising:

[0046] S1, mixing NaNO3 and KNO3 in a mass ratio of 6:4, grinding, heating to 400℃ to melt, cooling, and grinding again to obtain a eutectic salt;

[0047] The grinding is performed using a ball mill with a rotation speed of 300 to 500 rpm and a grinding time of 30 to 60 minutes. The cooling rate is 5°C / min.

[0048] S2, dispersing the few-layer graphene oxide and sodium ascorbate in water and mixing them uniformly to obtain a slurry; the slurry is subjected to hydrothermal treatment and then freeze-dried to obtain a graphene aerogel;

[0049] The content of the few-layer graphene oxide in the slurry is 7-10 mg / mL, the concentration of sodium ascorbate is 0.2-0.3 mg / mL, the hydrothermal treatment temperature is 120-130° C., and the hydrothermal treatment time is preferably 12-24 hours. The hydrothermal treatment promotes the reduction and structural reorganization of the few-layer graphene oxide by sodium ascorbate.

[0050] In this step, the hydrothermally treated slurry is poured into a mold and frozen from bottom to top using liquid nitrogen for 10-15 minutes. The mold is then dried at -70-80°C and a vacuum of <15 Pa for 24-48 hours. In this application, the mold is a cylinder with a diameter and height of 1-2 cm. Freeze-drying removes all moisture, resulting in a porous graphene aerogel.

[0051] S3, dissolving the eutectic salt in water to prepare a saturated solution, and immersing the graphene aerogel in the saturated solution under vacuum;

[0052] Specifically, the eutectic salt prepared in step S1 is dissolved in distilled water heated to near boiling point, and stirring is continued until the eutectic salt is fully dissolved and salt particles begin to become insoluble, thereby obtaining a saturated solution. The graphene aerogel is immersed in the saturated solution, allowing the eutectic salt solution to fully penetrate the pore structure of the graphene aerogel.

[0053] To ensure uniform and complete penetration of the graphene aerogel and molten salt composite, a higher vacuum level helps remove air and other gases from the material's pores, allowing the molten salt to more effectively fill these spaces. A higher vacuum level lowers the boiling point of water. To ensure effective impregnation, the impregnation temperature is controlled between 60 and 80°C, the pressure is less than 100 Pa, and the impregnation time is 2 to 3 hours.

[0054] S4, freeze-drying the impregnated product to obtain a molten salt phase change energy storage material.

[0055] Specifically, the vacuum impregnation product is frozen in liquid nitrogen for 10 to 15 minutes and then dried for 24 to 48 hours at a temperature of -70 to -80°C and a vacuum of less than 15 Pa. Freeze-drying removes moisture from the graphene-molten salt composite material, yielding a graphene-based molten salt phase change energy storage material.

[0056] In this application, the few-layer graphene oxide is prepared by the following method:

[0057] Mix graphite and sulfuric acid evenly, add sodium nitrate and phosphorus pentoxide, stir at 80-100°C for 12-24 hours, separate and collect the solid phase, wash and air-dry to obtain the precursor;

[0058] The precursor is dispersed in excess concentrated sulfuric acid, and potassium permanganate is slowly added thereto, stirred at -10 to 0°C, and then diluted with water. The temperature is then raised to 90°C, and hydrogen peroxide is added until the solution turns bright yellow to obtain a dispersion. The dispersion is diluted with water, centrifuged at a speed of 5000 to 7000 r / min to remove multilayer graphene oxide, and then centrifuged at a speed of 10000 to 12000 r / min to remove impurities. The concentrated solution obtained by centrifugation is freeze-dried to obtain few-layer graphene oxide.

[0059] In the present application, the mass ratio of the graphite, sulfuric acid, sodium nitrate and phosphorus pentoxide is preferably (1-2):(18-20):(1.5-2):(1.5-2); the mass ratio of potassium permanganate to graphite is preferably 5:1.

[0060] This application uses graphene aerogel and solar salt as raw materials, and adopts the vacuum impregnation method to prepare molten salt phase change energy storage material, so that the molten salt can evenly penetrate the pores of the graphene aerogel; it combines the high porosity of graphene with the phase change energy storage characteristics of molten salt, significantly improving the thermal conductivity and phase change stability.

[0061] Secondly, this application provides a molten salt phase-change energy storage material prepared by the aforementioned preparation method. This molten salt phase-change energy storage material combines the high porosity of graphene with the phase-change energy storage properties of molten salt, significantly improving thermal conductivity and phase-change stability. The large wetting angle between graphene and the molten salt prevents leakage of the molten salt, further enhancing thermal conductivity.

[0062] The molten salt phase change energy storage material prepared in this application is particularly suitable for energy storage in electronic equipment and photothermal conversion devices and systems with strict requirements. It can be applied to photothermal storage in solar thermal power stations, as well as thermal energy storage and utilization in the steel, cement, and glass industries.

[0063] The present application is further described below through examples.

[0064] Example 1

[0065] This embodiment provides a method for preparing a molten salt phase change energy storage material, comprising:

[0066] S1. Mix NaNO3 and KNO3 in a mass ratio of 6:4 and grind in a ball mill at 500 rpm for 60 min to obtain a mixed salt powder. Heat the mixed salt powder to 400°C to melt, then cool at a cooling rate of 5°C / min and grind again to obtain a eutectic salt.

[0067] S2, mix 2g of flake graphite with 10ml of sulfuric acid, stir at 80℃, then add 1.7g of sodium nitrate and 1.7g of phosphorus pentoxide in sequence, and continue stirring for 12 hours; filter the mixture twice and dry it in the shade at room temperature for 3 hours to obtain a precursor; add 80ml of sulfuric acid to a beaker, add the precursor, slowly add 10g of potassium permanganate to the beaker at -10℃, stir for 4.5 hours, then treat it in a 35℃ water bath for 4 hours, dilute it in 1000ml of water, and stir for 15 minutes; heat it to 90℃ and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at 11000r / min for 7min, then centrifuge it at 6000r / min for 5min to remove impurities, and centrifuge it again at 11000r / min for 15min to obtain a concentrate. Freeze-dry the concentrate for 48 hours to obtain few-layer graphene oxide;

[0068] 200mg of few-layer graphene oxide was mixed with 5mg of sodium ascorbate and 20ml of water, shaken and mixed for 5 minutes. The mixture was then hydrothermally treated at 130°C for 12 hours. The resulting mixture was then poured into a cylindrical polyethylene mold with a diameter of 2cm and a height of 2cm. The mold was directionally frozen from bottom to top using liquid nitrogen for 15 minutes. After freezing, the mold was placed in a freeze dryer set to -70°C and a vacuum of <15Pa. It was then dried for 48 hours to obtain a porous graphene aerogel.

[0069] S3. Slowly add the eutectic salt to distilled water heated to near boiling point, stirring continuously until the salt is completely dissolved and salt particles begin to become insoluble, indicating that the solution has reached a supersaturated state. The graphene aerogel is placed in the supersaturated solution and transferred to a vacuum oven. Heat to 60°C at a pressure of less than 100 Pa and maintain this temperature for 2 hours, ensuring that the saturated solution fully penetrates the pore structure of the graphene aerogel.

[0070] S4, freezing the impregnated product with liquid nitrogen for 10-15 minutes, and then drying it at a temperature of -80°C and a vacuum degree of <15 Pa for 48 hours to obtain a molten salt phase change energy storage material.

[0071] Example 2

[0072] This embodiment provides a method for preparing a molten salt phase change energy storage material, comprising:

[0073] S1. Mix NaNO3 and KNO3 in a mass ratio of 6:4 and grind in a ball mill at 500 rpm for 60 min to obtain a mixed salt powder. Heat the mixed salt powder to 400°C to melt, then cool at a cooling rate of 5°C / min and grind again to obtain a eutectic salt.

[0074] S2, mix 2g of flake graphite with 10ml of sulfuric acid, stir at 80℃, then add 1.7g of sodium nitrate and 1.7g of phosphorus pentoxide in sequence, and continue stirring for 12 hours; filter the mixture twice and dry it in the shade at room temperature for 3 hours to obtain a precursor; add 80ml of sulfuric acid to a beaker, add the precursor, slowly add 10g of potassium permanganate to the beaker at -10℃, stir for 4.5 hours, then treat it in a 35℃ water bath for 4 hours, dilute it in 1000ml of water, and stir for 15 minutes; heat it to 90℃ and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at 11000r / min for 7min, then centrifuge it at 6000r / min for 5min to remove impurities, and centrifuge it again at 11000r / min for 15min to obtain a concentrate. Freeze-dry the concentrate for 48 hours to obtain few-layer graphene oxide;

[0075] 150mg of few-layer graphene oxide was mixed with 5mg of sodium ascorbate and 20ml of water, shaken and mixed for 5 minutes. The mixture was then hydrothermally treated at 120°C for 12 hours. The resulting mixture was then poured into a cylindrical polyethylene mold with a diameter of 2cm and a height of 2cm. The mold was directionally frozen from bottom to top using liquid nitrogen for 15 minutes. After freezing, the mold was placed in a freeze dryer set to -70°C and a vacuum of <15Pa. It was then dried for 48 hours to obtain a porous graphene aerogel.

[0076] S3. Slowly add the eutectic salt to distilled water heated to near boiling point, stirring continuously until the salt is completely dissolved and salt particles begin to become insoluble, indicating that the solution has reached a supersaturated state. The graphene aerogel is placed in the supersaturated solution and transferred to a vacuum oven. Heat to 70°C at a pressure of less than 100 Pa and maintain this temperature for 2 hours to ensure that the SS fully penetrates the pore structure of the graphene aerogel.

[0077] S4, freezing the impregnated product with liquid nitrogen for 10-15 minutes, and then drying it at a temperature of -80°C and a vacuum degree of <15 Pa for 48 hours to obtain a molten salt phase change energy storage material.

[0078] Example 3

[0079] This embodiment provides a method for preparing a molten salt phase change energy storage material, comprising:

[0080] S1. Mix NaNO3 and KNO3 in a mass ratio of 6:4 and grind in a ball mill at 500 rpm for 60 min to obtain a mixed salt powder. Heat the mixed salt powder to 400°C to melt, then cool at a cooling rate of 5°C / min and grind again to obtain a eutectic salt.

[0081] S2, mix 2g of flake graphite with 10ml of sulfuric acid, stir at 80℃, then add 1.7g of sodium nitrate and 1.7g of phosphorus pentoxide in sequence, and continue stirring for 12 hours; filter the mixture twice and dry it in the shade at room temperature for 3 hours to obtain a precursor; add 80ml of sulfuric acid to a beaker, add the precursor, slowly add 10g of potassium permanganate to the beaker at -10℃, stir for 4.5 hours, then treat it in a 35℃ water bath for 4 hours, dilute it in 1000ml of water, and stir for 15 minutes; heat it to 90℃ and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at 11000r / min for 7min, then centrifuge it at 6000r / min for 5min to remove impurities, and centrifuge it again at 11000r / min for 15min to obtain a concentrate. Freeze-dry the concentrate for 48 hours to obtain few-layer graphene oxide;

[0082] 200mg of few-layer graphene oxide was mixed with 5mg of sodium ascorbate and 20ml of water, shaken and mixed for 5 minutes. The mixture was then hydrothermally treated at 130°C for 12 hours. The resulting mixture was then poured into a cylindrical polyethylene mold with a diameter of 2cm and a height of 2cm. The mold was directionally frozen from bottom to top using liquid nitrogen for 15 minutes. After freezing, the mold was placed in a freeze dryer set to -70°C and a vacuum of <15Pa. It was then dried for 48 hours to obtain a porous graphene aerogel.

[0083] S3. Slowly add the eutectic salt to distilled water heated to near boiling point, stirring continuously until the salt is completely dissolved and salt particles begin to become insoluble, indicating that the solution has reached a supersaturated state. The graphene aerogel is placed in the supersaturated solution and transferred to a vacuum oven. Heat to 75°C at a pressure of less than 100 Pa and maintain this temperature for 2 hours to ensure that the SS fully penetrates the pore structure of the graphene aerogel.

[0084] S4, freezing the impregnated product with liquid nitrogen for 10-15 minutes, and then drying it at a temperature of -80°C and a vacuum degree of <15 Pa for 48 hours to obtain a molten salt phase change energy storage material.

[0085] The performance of the graphene aerogel and molten salt phase change energy storage material prepared in Example 1 was evaluated. Figure 1 This is a photo of the graphene aerogel prepared in Example 1. Its regular shape and intact structure indicate successful preparation. The aerogel exhibits good uniformity, with no obvious defects or uneven areas.

[0086] Figure 2 This is a physical picture of the graphene aerogel after impregnation in Example 1. Figure 2 It can be seen that the graphene aerogel has been fully infiltrated by the saturated salt solution, and the surface is uniformly wet, indicating that the solution has successfully penetrated into the internal structure of the aerogel and the impregnation effect is good. The graphene aerogel has a good ability to be infiltrated by the saturated salt solution.

[0087] Figure 3 The scanning electron microscope image of the graphene aerogel after impregnation. Figure 3 The results show that the solar salt crystals were successfully loaded into the graphene aerogel, with uniform distribution and high loading rate. The regular crystal morphology and good crystallinity indicate that during the impregnation process, the solar salt was able to effectively enter the aerogel's pore structure and form high-quality crystals, further demonstrating the excellent performance of the graphene aerogel as a carrier in the adsorption and crystallization processes.

[0088] Figure 4 This is a DSC (differential scanning calorimetry) test result diagram of the molten salt phase change energy storage material of Example 1. Figure 4 It can be seen that the composite material exhibits excellent phase change heat storage capacity and can effectively absorb and release heat within a specific temperature range, indicating that it has good thermal stability and energy storage performance.

[0089] The thermal conductivity of the graphene aerogel, eutectic salt, and molten salt phase change energy storage material prepared in Example 1 was tested using a laser flash method, specifically including:

[0090] 1. Prepare samples: Cut and prepare samples in the shape of square slices.

[0091] 2. Install the sample: Fix the sample in the test equipment, ensuring that the sample surface is flat and in good contact with the equipment.

[0092] 3. Laser irradiation: Use short pulse laser to irradiate one side of the sample.

[0093] 4. Temperature measurement: Record the temperature response on the other side of the sample, usually using an infrared sensor.

[0094] 5. Data analysis: Calculate the thermal diffusivity from the sample's temperature response curve, and then calculate the thermal conductivity based on the sample's density and specific heat capacity.

[0095] The test results are as follows Figure 5 As shown. Figure 5 The thermal conductivity of the molten salt phase change energy storage material is 0.712 W / m·K, significantly higher than that of graphene aerogel alone (0.124 W / m·K) and close to that of solar salt (0.763 W / m·K). This indicates that the thermal conductivity of the composite material has been significantly improved, making it suitable for phase change energy storage applications.

[0096] Although this specification has been used to fully describe the present application using general descriptions and specific embodiments, it is obvious to those skilled in the art that modifications or improvements may be made based on the present application. Therefore, such modifications or improvements made without departing from the spirit of the present application are within the scope of protection claimed in this application.

Claims

1. A method for preparing a molten salt phase change energy storage material, characterized in that: include: S1, mixing NaNO3 and KNO3 in a mass ratio of 6:4, grinding, heating to 400℃ to melt, cooling, and grinding again to obtain a eutectic salt; S2, dispersing the few-layer graphene oxide and sodium ascorbate in water and mixing them uniformly to obtain a slurry; the slurry is subjected to hydrothermal treatment and then freeze-dried to obtain a graphene aerogel; S3, dissolving the eutectic salt in water to prepare a saturated solution, and immersing the graphene aerogel in the saturated solution under vacuum; S4, freeze-drying the impregnated product to obtain a molten salt phase change energy storage material.

2. The preparation method according to claim 1, characterized in that The few-layer graphene oxide is prepared by the following method: Mix graphite and sulfuric acid evenly, add sodium nitrate and phosphorus pentoxide, stir at 80-100°C for 12-24 hours, separate and collect the solid phase, wash and air-dry to obtain the precursor; The precursor is dispersed in excess concentrated sulfuric acid, and potassium permanganate is slowly added thereto, stirred at -10 to 0°C, and then diluted with water. After that, the temperature is raised to 90°C, and hydrogen peroxide is added until the solution turns bright yellow to obtain a dispersion. The dispersion is diluted with water, centrifuged at a speed of 5000-7000 r / min to remove multilayer graphene oxide, and then centrifuged at a speed of 10000-12000 r / min to remove impurities, and the concentrated liquid obtained by centrifugation is freeze-dried to obtain few-layer graphene oxide.

3. The preparation method according to claim 2, wherein: The mass ratio of the graphite, sulfuric acid, sodium nitrate and phosphorus pentoxide is (1-2):(18-20):(1.5-2):(1.5-2); The mass ratio of the potassium permanganate to the graphite is 5:

1.

4. The preparation method according to claim 1, characterized in that The content of graphene oxide in the slurry is 7-10 mg / mL, and the concentration of sodium ascorbate is 0.2-0.3 mg / mL.

5. The preparation method according to claim 1, characterized in that In step S2, the temperature of the hydrothermal treatment is 120-130°C.

6. The preparation method according to claim 1, characterized in that In step S2, the freeze-drying comprises: The slurry after hydrothermal treatment is injected into the mold, and the mold is oriented and frozen from bottom to top using liquid nitrogen for 10 to 15 minutes. Then dry it at a temperature of -70 to -80°C and a vacuum degree of <15 Pa for 24 to 48 hours.

7. The preparation method according to claim 1, characterized in that The temperature of the immersion treatment is 60-80° C., and the pressure is less than 100 Pa.

8. The preparation method according to claim 1, characterized in that The freeze drying in step S4 comprises: The vacuum impregnation product is frozen by liquid nitrogen for 10 to 15 minutes; Then dry it at a temperature of -70 to -80°C and a vacuum degree of <15 Pa for 24 to 48 hours.

9. The molten salt phase change energy storage material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the molten salt phase change energy storage material prepared by the preparation method according to any one of claims 1 to 8 in solar thermal storage in a solar thermal power station.

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