Nanometer inorganic composite heat storage material and preparation method thereof

Abstract

The application relates to a nano inorganic composite heat storage material and a preparation method thereof, and belongs to the technical field of heat storage materials. In the application, the nano inorganic composite heat storage material can be prepared by fully stirring and uniformly dispersing 32-60 parts of modified diatomite, 33-47 parts of modified nano metal oxide and 4-7 parts of a binder, and then performing pressing and sintering treatment and grinding through a ball mill. The modified diatomite is modified by perovskite, epoxy resin and graphene oxide, and the modified nano metal oxide is obtained by heat treatment of magnesium oxide treated by zirconium silicide and zirconium nitrate. The nano inorganic composite heat storage material prepared by the application has good heat conductivity and excellent heat storage performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat storage materials, and relates to a nano inorganic composite heat storage material and a preparation method thereof. BACKGROUND

[0002] Heat storage technology is currently the most effective way to solve the mismatch between heat supply and demand in time, space and intensity, and is a new energy technology that can improve energy utilization efficiency. Heat storage technology is characterized in that unused or excess heat can be stored by a specific medium and released for use when needed. The technology is widely used in solar energy, power peak shaving and industrial waste heat, and other non-continuous energy systems.

[0003] Due to the shortage of fossil fuels and the increasingly serious environmental problems caused by them, sustainable and recyclable energy (such as geothermal energy and solar energy) has attracted widespread attention, and energy conversion and conservation have become a worldwide topic. Heat storage technology is a technology that stores energy in the form of heat, which can effectively avoid the problems of low energy flow density, day and night alternation, seasonal conversion and other constraints on the use of some energy. It has been proven to be an effective method to improve energy efficiency and reduce environmental pollution.

[0004] In order to solve these problems, a porous carrier is generally used as a support material for heat storage materials, of which the most common are porous ceramics, porous carbon materials, metal foams and porous minerals. Diatomite has a rich pore structure, a porosity of up to 90%, a large specific surface area, is non-toxic, wear-resistant and heat-resistant, and is an ideal support material for phase change energy storage materials. However, there are still some defects when using porous carbon materials or diatomite directly as heat storage materials, such as low thermal conductivity and obvious supercooling phenomenon caused by low thermal conductivity.

[0005] Therefore, it is necessary to develop a diatomite heat storage material with good thermal conductivity and heat storage performance. SUMMARY

[0006] The purpose of the present application is to provide a nano inorganic composite heat storage material and a preparation method thereof, which has good thermal conductivity and excellent heat storage performance.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A nano inorganic composite heat storage material, which uses modified diatomite as a carrier and modified nano metal oxide as a loading material, and is bonded by a binder, wherein the preparation process of the modified diatomite is as follows:

[0009] S11, after the perovskite is crushed in a pulverizer, the perovskite is sieved through a 200-mesh sieve, and then annealing treatment is performed on the perovskite at 150 DEG C under a nitrogen atmosphere for 4-5 h to obtain perovskite powder;

[0010] S12, diatomite is calcined in a muffle furnace at 700-730 DEG C for 1 h, and then the diatomite is cooled to room temperature, crushed in a pulverizer, and sieved through a 200-mesh sieve; 5-8 parts of the perovskite powder and 20-30 parts of an epoxy resin acetone solution are thoroughly stirred and mixed uniformly, 25-35 parts of diatomite powder is added and soaked for 2-3 h, vacuum distillation is performed for 2 h, and then the diatomite is dried in a vacuum drying oven at 80 DEG C for 8 h to obtain pretreated diatomite powder;

[0011] S13, graphene oxide is ultrasonically treated in deionized water for 3-5 h to obtain a graphene oxide aqueous solution with a concentration of 0.5-1 mg / mL; the pretreated diatomite powder is added to the graphene oxide aqueous solution, and ultrasonic mixing is performed at 60-75 DEG C for 2 h; the mixture is dried in a vacuum drying oven at 60 DEG C for 18-22 h to obtain secondary treated diatomite powder; 50 parts of a 45% mass fraction hydriodic acid solution is mixed with 10-13 parts of the secondary treated diatomite powder, and heating is performed at 100 DEG C for 2 h; after filtration, the solid powder is placed in an oven and treated at 100 DEG C for 24 h to obtain the modified diatomite.

[0012] As a preferred technical solution of the present application, the binder is aluminum phosphate or borax.

[0013] As a preferred technical solution of the present application, in step S12, the mass fraction of the epoxy resin acetone solution is 10-15%.

[0014] As a preferred technical solution of the present application, the preparation process of the modified nanometer metal oxide is as follows:

[0015] S41, magnesium chloride and carbonic acid molten salt with a mass ratio of 1:7 are mixed and calcined at 500-600 DEG C for 5-7 h; after cooling to room temperature, the calcined product is dispersed in water, centrifuged, dried to obtain a solid, and 3-5 parts of zirconium silicide is added to 15-20 parts of the solid, and the mixture is uniformly mixed and ground by a ball mill at a speed of 400 r / min for 4 h to obtain modified magnesium oxide nanoparticles;

[0016] S42, 30-40 parts of the modified magnesium oxide nanoparticles and 20-30 parts of zirconium nitrate are added to 30-50 parts of ethanol to obtain a precursor mixture, and the precursor mixture is prepared into magnesium oxide-zirconia composite powder by a flame spray pyrolysis method;

[0017] S43, calcining again under the condition of 550-600 DEG C, keeping for 7-9h, washing the calcined product with water, centrifuging and drying, the modified nano metal oxide is obtained.

[0018] As a preferred technical scheme of the present application, in step S41, the carbonic acid molten salt is a mixture of potassium carbonate and sodium carbonate with a mass ratio of 3:4.

[0019] As a preferred technical scheme of the present application, in step S42, in the flame spray pyrolysis method, methane is used as the combustion-supporting gas, the precursor mixture is atomized and ignited, and the effective sintering height of the flame is 20-30cm.

[0020] A preparation method of a nano inorganic composite heat storage material, comprising the following preparation process:

[0021] Under the condition of 40-60 DEG C, 32-60 parts of modified diatomite, 33-47 parts of modified nano metal oxide and 4-7 parts of binder are fully stirred and dispersed uniformly, then ultrasonic treatment is carried out under the condition of 0.03-0.05MPa for 3-8min, the mixture is pre-pressed under the condition of 10-20MPa, then sintered under the condition of 130-150 DEG C, cooled to room temperature, then secondarily pressed under the condition of 19-30MPa, then ground by a ball mill at a rotating speed of 400r / min for 5h, and the nano inorganic composite heat storage material is obtained.

[0022] The present application has the following beneficial effects:

[0023] The perovskite can reduce the number of crystal defects in the structure by annealing treatment, further perfect the perovskite crystal structure, and can remove part of the oxidation impurities, improve the crystal quality, and further improve the stability of the material, prevent it from decomposing in the use process, the perovskite has high thermal stability and thermal conductivity, can maintain high efficient heat conduction under high temperature conditions.

[0024] Diatomaceous earth is calcined at 700–730℃. The main chemical component of diatomaceous earth is SiO2. During high-temperature calcination, some amorphous SiO2 transforms into crystalline form, which helps improve its stability and durability. The calcination process also causes the organic matter in the diatomaceous earth to burn or decompose, and the removal of organic matter helps improve the purity and adsorption performance of the diatomaceous earth. Diatomaceous earth itself has a large number of micropores and a high specific surface area, making it an ideal carrier and encapsulation material. In perovskite-modified diatomaceous earth, a good protective and dispersion environment for perovskite is provided. Furthermore, the addition of perovskite can further increase the specific surface area of ​​diatomaceous earth, thus providing more thermal energy storage sites and improving thermal storage efficiency. Perovskite also helps reduce oxidation reactions in diatomaceous earth, reducing heat loss. Simultaneously, epoxy resin encapsulation and curing help perovskite to be more uniformly composited on the diatomaceous earth surface. The micropores on the diatomaceous earth surface improved by perovskite can adsorb monomers from the epoxy resin, thereby enhancing heat resistance. Furthermore, it can directly contact fluid media and withstand the impact of fluid media. The high specific surface area and abundant functional groups of graphene oxide can form more stable chemical bonds with the epoxy groups on the surface of epoxy resin, helping graphene oxide to be more fully loaded on the structure of diatomaceous earth. Then, through hydroiodic acid treatment, the surface graphene oxide is reduced to graphene, improving the surface activity of the material.

[0025] Magnesium oxide is chemically stable and can be used for a long time without being damaged by heat, thus maintaining its excellent heat storage performance. Magnesium oxide has a high specific heat capacity, allowing it to absorb and store a large amount of heat when heated. Its high thermal conductivity enables rapid heat transfer, increasing heat storage efficiency. This efficient thermal conductivity facilitates the rapid storage and release of heat. Magnesium oxide maintains stable properties at high temperatures and is not easily decomposed or altered.

[0026] In the process of preparing magnesium oxide by calcining magnesium chloride, molten carbonate is added. Under high temperature conditions, the molten carbonate can react with chloride ions in magnesium chloride to generate corresponding chlorides and carbon dioxide, thereby reducing the thermal stability of magnesium chloride and promoting its decomposition during calcination. This can effectively improve the thermal conductivity of the entire system, which helps to distribute heat more evenly, making the magnesium oxide formation process more uniform and efficient. Furthermore, zirconium silicide is fully compounded with magnesium oxide through grinding. The addition of zirconium silicide can further improve its thermal stability. The addition of zirconium silicide can further improve its thermal conductivity by changing its crystal structure or increasing interfacial thermal conductivity. Since zirconium silicide has good corrosion resistance, it can enhance the chemical resistance and corrosion resistance of magnesium oxide, thereby maintaining a long service life and stability.

[0027] Although magnesium oxide itself has high fireproof and insulating properties, it has a high thermal expansion coefficient, resulting in poor heat shock resistance, while zirconium oxide has a melting point as high as 2700 DEG C, strong thermal shock resistance, and high load softening temperature. Therefore, the composite material formed by combining modified zirconium oxide and magnesium oxide can significantly improve the thermal stability of the heat storage material, so that the heat storage material is more stable when facing temperature fluctuations; the addition of zirconium oxide can promote the sintering of magnesium oxide, reduce the apparent porosity, and improve the relative density of the material, thereby optimizing the heat storage property, and the thermal expansion coefficient of zirconium oxide is coordinated with zirconium silicide and zirconium oxide, which helps to optimize the thermal expansion performance of the composite material and reduce thermal stress.

[0028] In the present application, through the above processing mode, the prepared nano-inorganic composite heat storage material has a large specific surface area, effectively loads modified nano-metal oxide by modified diatomite, improves the heat transfer performance of traditional nano-inorganic composite materials, and the prepared material has good thermal conductivity and excellent heat storage performance. DETAILED DESCRIPTION

[0029] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with examples.

[0030] In the following examples and comparative examples:

[0031] Carbonate molten salt is a mixture of potassium carbonate and sodium carbonate with a mass ratio of 3:4;

[0032] Diatomite: purchased from Shandong Zhengxing New Material Co., Ltd., product number: CG8;

[0033] Perovskite: purchased from Henan Alpha Chemical Co., Ltd.;

[0034] Epoxy resin: purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., product number: R832312;

[0035] Graphene oxide: purchased from Wuhan Penglei Biotechnology Co., Ltd.;

[0036] Hydroiodic acid: purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., product number: H810917;

[0037] Magnesium chloride: purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., product number: M813765;

[0038] Potassium carbonate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number: P111556;

[0039] Sodium carbonate: purchased from Shandong Yukang Chemical Co., Ltd., product number: 188;

[0040] Zirconium silicide: purchased from Shanghai Maile Biotech Co., Ltd., product number: M90290;

[0041] Aluminum phosphate: purchased from Jinan Dehou Chemical Co., Ltd., item number: 002;

[0042] Zirconium nitrate: purchased from Tesco Chemical (Hubei) Co., Ltd., brand: Canos.

[0043] Example 1

[0044] Preparation of modified diatomite:

[0045] S11, after the perovskite is crushed in a crusher, it is sieved through a 200-mesh sieve, and then annealed at 150°C for 4h under a nitrogen environment to obtain perovskite powder;

[0046] S12, diatomite is calcined in a muffle furnace at 700°C for 1h, cooled to room temperature after taking out, crushed by a crusher, and sieved through a 200-mesh sieve; 5-8 parts of perovskite powder and 20 parts of 10% epoxy resin acetone solution are mixed uniformly by stirring, 25 parts of diatomite powder is soaked for 2h, vacuum distilled for 2h, and then vacuum dried at 80°C for 8h to obtain pretreated diatomite powder;

[0047] S13, after the graphene oxide is ultrasonically treated in deionized water for 3h, a 0.5mg / mL graphene oxide aqueous solution is obtained, the pretreated diatomite powder is added to the graphene oxide aqueous solution, and ultrasonic mixing is performed at 60°C for 2h, and then vacuum drying is performed at 60°C for 18h to obtain secondary treated diatomite powder, 50 parts of 45% hydriodic acid solution and 10 parts of secondary treated diatomite powder are mixed, heated at 100°C for 2h, and then the solid powder is placed in an oven and treated at 100°C for 24h after filtration to prepare the modified diatomite.

[0048] Preparation of modified nanometer metal oxide:

[0049] S41, magnesium chloride and carbonic acid molten salt with a mass ratio of 1:7 are mixed and calcined at 500°C for 5h, the calcined product is dispersed with water after cooling to room temperature, and then centrifuged and dried to obtain a solid, 3 parts of zirconium silicide are added to 15 parts of the solid, mixed uniformly, and then ground by a ball mill at a speed of 400r / min for 4h to obtain modified magnesium oxide nanoparticles;

[0050] S42, by mass parts, 30 parts of modified magnesium oxide nanoparticles, 20 parts of zirconium nitrate are added to 30 parts of ethanol to prepare a precursor mixture, and the precursor mixture is prepared by a flame spray pyrolysis method to obtain a magnesium oxide-zirconia composite powder, wherein in the flame spray pyrolysis method, methane is used as a combustion gas, the precursor mixture is atomized and ignited, and the effective sintering height of the flame is 20 cm;

[0051] S43, calcining again at 550℃ for 7h, washing the calcined product with water, centrifuging and drying, to obtain the modified nano metal oxide.

[0052] Preparation of nano-inorganic composite heat storage material:

[0053] By mass parts, 32 parts of modified diatomite, 33 parts of modified nano metal oxide and 4-6 parts of aluminum phosphate are fully stirred and dispersed uniformly at 40℃, then ultrasonic treatment is carried out under the condition of 0.03MPa for 3min, the mixture is pre-pressed under the condition of 10MPa, then sintered at 130℃, cooled to room temperature, then secondarily pressed at 19MPa, then ground by a ball mill at a speed of 400r / min for 5h to obtain the nano-inorganic composite heat storage material.

[0054] Example 2

[0055] Preparation of modified diatomite:

[0056] S11, after the perovskite is crushed by a crusher, it is sieved through a 200-mesh sieve, then annealed at 150℃ for 4.5h in a nitrogen environment to obtain perovskite powder;

[0057] S12, diatomite is calcined in a muffle furnace at 710℃ for 1h, then cooled to room temperature, crushed by a crusher, and sieved through a 200-mesh sieve; by mass parts, 6 parts of perovskite powder and 24 parts of epoxy resin acetone solution with a mass fraction of 13% are fully stirred and mixed uniformly, then 29 parts of diatomite powder are added and soaked for 2.5h, vacuum distilled for 2h, then taken out and vacuum dried at 80℃ for 8h to obtain pretreated diatomite powder;

[0058] S13, after the graphene oxide is ultrasonically treated in deionized water for 4h, a graphene oxide aqueous solution with a concentration of 0.7mg / mL is obtained, the pretreated diatomite powder is added to the graphene oxide aqueous solution, ultrasonically mixed at 68℃ for 2h, dried in a vacuum drying oven at 60℃ for 19h to obtain secondarily treated diatomite powder, 50 parts of hydroiodic acid solution with a mass fraction of 45% and 12 parts of secondarily treated diatomite powder are mixed, heated at 100℃ for 2h, filtered, and the solid powder is placed in an oven and treated at 100℃ for 24h, then cooled to room temperature to prepare the modified diatomite.

[0059] Preparation of modified nanometer metal oxide:

[0060] S41, magnesium chloride and carbonic acid molten salt with a mass ratio of 1:7 were mixed, calcined at 560℃ for 6h, and the calcined product was dispersed with water after cooling to room temperature, and then centrifuged, dried to obtain a solid, 4 parts of zirconium silicide were added to 17 parts of the solid, and then uniformly mixed and ground by a ball mill at a speed of 400r / min for 4h to obtain modified magnesium oxide nanoparticles;

[0061] S42, 35 parts of modified magnesium oxide nanoparticles and 27 parts of zirconium nitrate were added to 40 parts of ethanol to prepare a precursor mixture, and the precursor mixture was prepared into magnesium oxide-zirconium oxide composite powder by a flame spray pyrolysis method, wherein methane was used as a combustion gas, the precursor mixture was atomized and ignited, and the effective sintering height of the flame was 26cm;

[0062] S43, calcination was further carried out at 570℃ for 8h, and the calcined product was washed with water, centrifuged, and dried to obtain the modified nanometer metal oxide.

[0063] Preparation of nanometer inorganic composite heat storage material:

[0064] According to the mass fraction, 40 parts of modified diatomite, 41 parts of modified nanometer metal oxide and 5 parts of aluminum phosphate were fully stirred and dispersed uniformly at 50℃, and then ultrasonic treatment was carried out under the condition of 0.04MPa for 6min, and the mixture was pre-pressed under the condition of 15MPa and sintered at 140℃, and then cooled to room temperature and secondarily pressed at 22MPa, and then ground by a ball mill at a speed of 400r / min for 5h to obtain the nanometer inorganic composite heat storage material.

[0065] Example 3

[0066] Preparation of modified diatomite:

[0067] S11, the perovskite was crushed by a crusher, and then sieved through a 200 mesh sieve, and then annealed at 150℃ for 5h in a nitrogen environment to obtain perovskite powder;

[0068] S12, the diatomite was calcined in a muffle furnace at 730℃ for 1h, and then cooled to room temperature, crushed by a crusher, and then sieved through a 200 mesh sieve; 8 parts of perovskite powder and 30 parts of epoxy resin acetone solution with a mass fraction of 15% were fully stirred and mixed uniformly, 35 parts of diatomite powder was added and soaked for 3h, and then vacuum distillation was carried out for 2h, and then the product was taken out and vacuum dried at 80℃ for 8h to obtain pretreated diatomite powder;

[0069] S13, ultrasonic treatment of graphene oxide in deionized water for 5h to obtain a concentration of 1mg / mL of graphene oxide aqueous solution, adding pretreated diatomite powder in the graphene oxide aqueous solution, ultrasonic mixing at 75℃ for 2h, drying in a vacuum drying oven at 60℃ for 22h, obtaining the secondary treated diatomite powder, mixing 50 parts of mass fraction of 45% hydroiodic acid solution with 13 parts of secondary treated diatomite powder, heating at 100℃ for 2h, after filtration, the solid powder is placed in an oven and treated at 100℃ for 24h, and the modified diatomite is prepared after cooling to room temperature.

[0070] Preparation of modified nanometer metal oxide:

[0071] S41, mixing magnesium chloride and carbonic acid molten salt with a mass ratio of 1:7, calcining at 600℃, keeping for 7h, cooling to room temperature, then dispersing the calcined product in water, centrifuging, drying to obtain a solid, adding 5 parts of zirconium silicide to 20 parts of the solid, mixing uniformly, and then grinding by a ball mill at a speed of 400r / min for 4h to obtain modified magnesium oxide nanoparticles;

[0072] S42, 40 parts of modified magnesium oxide nanoparticles and 30 parts of zirconium nitrate are added to 50 parts of ethanol to prepare a precursor mixture, and the magnesium oxide-zirconium oxide composite powder is prepared by flame spray pyrolysis of the precursor mixture, wherein methane is used as the combustion gas in the flame spray pyrolysis, the precursor mixture is atomized and ignited, and the effective sintering height of the flame is 30cm;

[0073] S43, calcining again at 600℃ for 9h, washing the calcined product with water, centrifuging and drying to obtain the modified nanometer metal oxide.

[0074] Preparation of nanometer inorganic composite heat storage material:

[0075] According to the mass fraction, 60 parts of modified diatomite, 47 parts of modified nanometer metal oxide and 7 parts of aluminum phosphate are fully stirred and dispersed uniformly at 60℃, then ultrasonic treatment is carried out under the condition of 0.05MPa for 8min, the mixture is pre-pressed under the condition of 20MPa, then sintered at 150℃, cooled to room temperature, then secondarily pressed at 30MPa, and finally ground by a ball mill at a speed of 400r / min for 5h to obtain the nanometer inorganic composite heat storage material.

[0076] Comparative example 1

[0077] The difference between comparative example 1 and example 1 is that no epoxy resin acetone solution is added when preparing the modified diatomite in comparative example 1, and the rest of the operations are consistent.

[0078] Comparative example 2

[0079] The difference between Comparative Example 2 and Example 1 is that no perovskite is added when preparing the modified diatomite in Comparative Example 2, and the rest of the operations are consistent.

[0080] Comparative Example 3

[0081] The difference between Comparative Example 3 and Example 1 is that no graphene oxide is added when preparing the modified diatomite in Comparative Example 3, and the rest of the operations are consistent.

[0082] Comparative Example 4

[0083] The difference between Comparative Example 4 and Example 1 is that no modification is performed on the diatomite in Comparative Example 4, and the rest of the operations are consistent.

[0084] Comparative Example 5

[0085] The difference between Comparative Example 5 and Example 1 is that no zirconium silicate is added when preparing the modified magnesium oxide nanoparticles in Comparative Example 5, and the rest of the operations are consistent.

[0086] Comparative Example 6

[0087] The difference between Comparative Example 6 and Example 1 is that no zirconium nitrate is added when preparing the modified nano metal oxide in Comparative Example 6, and the rest of the operations are consistent.

[0088] Comparative Example 7

[0089] The difference between Comparative Example 7 and Example 1 is that no carbonic acid molten salt is added when preparing the modified magnesium oxide nanoparticles in Comparative Example 7, and the rest of the operations are consistent.

[0090] Performance test:

[0091] The thermal conductivity is measured by a thermal conductivity instrument, and the data is as follows:

[0092]

[0093] From the above results, it can be seen that compared with Comparative Examples 1-4, the method in the present application can improve the heat storage and thermal stability of the material.

[0094] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any equivalent embodiments with equivalent changes and modifications are still within the scope of the technical solution of the present application.

Claims

1. A nano-inorganic composite thermal storage material, characterized in that: The nano-inorganic composite thermal storage material uses modified diatomaceous earth as a carrier and modified nano-metal oxides as a loading material, bonded together with a binder. The preparation process of the modified diatomaceous earth is as follows: S11. After crushing the perovskite in a pulverizer, pass it through a 200-mesh sieve, and then anneal it at 150°C for 4-5 hours under nitrogen atmosphere to obtain perovskite powder. S12. Calcine diatomaceous earth in a muffle furnace at 700-730℃ for 1 hour. After cooling to room temperature, pulverize it and pass it through a 200-mesh sieve. Mix 5-8 parts of perovskite powder with 20-30 parts of epoxy resin acetone solution by mass, then add 25-35 parts of diatomaceous earth powder and soak for 2-3 hours. Distill under reduced pressure for 2 hours, then remove and vacuum dry at 80℃ for 8 hours to obtain pretreated diatomaceous earth powder. S13. Graphene oxide is ultrasonically treated in deionized water for 3-5 hours to obtain an aqueous solution of graphene oxide with a concentration of 0.5-1 mg / mL. Pretreated diatomaceous earth powder is added to the aqueous solution of graphene oxide and ultrasonically mixed at 60-75°C for 2 hours. The mixture is then dried in a vacuum drying oven at 60°C for 18-22 hours to obtain secondary treated diatomaceous earth powder. 50 parts of a 45% hydroiodic acid solution are mixed with 10-13 parts of the secondary treated diatomaceous earth powder and heated at 100°C for 2 hours. After filtration, the solid powder is placed in an oven and treated at 100°C for 24 hours. After cooling to room temperature, the modified diatomaceous earth is obtained. The preparation process of the modified nano-metal oxide is as follows: S41. Magnesium chloride and molten carbonate in a mass ratio of 1:7 are mixed and calcined at 500-600℃ for 5-7 hours. After cooling to room temperature, the calcined product is dispersed in water, centrifuged, and dried to obtain a solid. 3-5 parts of zirconium silicide are added to 15-20 parts of the solid, mixed evenly, and then ground in a ball mill at 400 r / min for 4 hours to obtain modified magnesium oxide nanoparticles. The molten carbonate is a mixture of potassium carbonate and sodium carbonate in a mass ratio of 3:

4. S42. By mass, 30-40 parts of modified magnesium oxide nanoparticles and 20-30 parts of zirconium nitrate are added to 30-50 parts of ethanol to prepare a precursor mixture. The precursor mixture is then used to prepare magnesium oxide-zirconia multiphase powder by flame spray pyrolysis. S43. Then calcine at 550~600℃ for 7~9h. Wash the calcined product with water, centrifuge and dry it to obtain the modified nano metal oxide. The binder is aluminum phosphate.

2. The nano-inorganic composite thermal storage material according to claim 1, characterized in that: In step S12, the mass fraction of the epoxy resin acetone solution is 10-15%.

3. The nano-inorganic composite thermal storage material according to claim 1, characterized in that: In step S42, methane is used as the combustion-supporting gas in the flame spray pyrolysis method to atomize and ignite the precursor mixture, and the effective sintering height of the flame is 20~30cm.

4. A method for preparing a nano-inorganic composite thermal storage material as described in any one of claims 1-3, characterized in that, The preparation process includes the following: By weight, 32-60 parts of modified diatomaceous earth, 33-47 parts of modified nano-metal oxides and 4-7 parts of binder are thoroughly stirred and dispersed at 40-60℃. Then, the mixture is ultrasonically treated at a pressure of 0.03-0.05MPa for 3-8 minutes. The mixture is pre-pressed at 10-20MPa and sintered at 130-150℃. After cooling to room temperature, it is pressed again at 19-30MPa. Finally, it is ground in a ball mill at 400r / min for 5 hours to obtain the nano-inorganic composite thermal storage material.

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