Nano inorganic composite heat storage material and preparation method thereof

Abstract

The invention relates to a nano inorganic composite heat storage material and a preparation method thereof, and belongs to the technical field of heat storage materials. 32-60 parts of modified diatomite, 33-47 parts of modified nano metal oxide and 4-7 parts of binder are fully stirred and uniformly dispersed, and the nano inorganic composite heat storage material can be prepared through pressing and sintering treatment and grinding through a ball mill. Wherein the modified diatomite is subjected to modification treatment through perovskite, epoxy resin and graphene oxide, and the modified nano metal oxide is obtained through heat treatment of zirconium silicide treated magnesium oxide and zirconium nitrate. The prepared nano inorganic composite heat storage material is good in thermal conductivity and excellent in heat storage performance.

Description

Technical Field

[0001] The invention 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 Art

[0002] Thermal storage technology is currently the most effective way to solve the mismatch between thermal energy supply and demand in terms of time, space and intensity. It is a new energy technology that can improve energy efficiency. The characteristic of thermal storage technology is that it can store unused or excess thermal energy in a specific medium and release it for use when needed. This technology is widely used in non-continuous energy systems such as solar energy, power peak regulation and industrial waste heat.

[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 global topic. Thermal storage technology is a technology that directly stores energy in the form of heat. It can effectively avoid the problems that restrict the utilization of some energy sources due to low energy flow density, day and night alternation, and seasonal changes. It has now been proven to be an effective way to improve energy efficiency and reduce environmental pollution.

[0004] In order to solve these problems, porous carriers are generally used as supporting materials for heat storage materials, among which the most common ones are porous ceramics, porous carbon materials, metal foams and porous minerals. Diatomaceous earth has rich pore structure, porosity up to 90%, large specific surface area, non-toxicity, wear resistance, heat resistance and other characteristics, and is an ideal supporting material for phase change energy storage materials. However, there are still some defects in directly using porous carbon materials or diatomaceous earth as heat storage materials: such as low thermal conductivity, and the obvious supercooling phenomenon of heat storage materials caused by low thermal conductivity.

[0005] Therefore, it is necessary to develop a diatomaceous earth heat storage material with good thermal conductivity and heat storage properties. Summary of the invention

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

[0007] The purpose of the present invention can be achieved through the following technical solutions:

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

[0009] S11, crushing the perovskite in a crusher, passing through a 200-mesh sieve, and then annealing at 150° C. for 4 to 5 hours in a nitrogen environment to obtain a perovskite powder;

[0010] S12, calcining diatomaceous earth in a muffle furnace at 700-730°C for 1h, cooling to room temperature after taking out, crushing with a pulverizer, and passing through a 200-mesh sieve; mixing 5-8 parts of perovskite powder and 20-30 parts of epoxy resin acetone solution by mass, adding 25-35 parts of diatomaceous earth powder and soaking for 2-3h, distilling under reduced pressure for 2h, taking out and vacuum drying at 80°C for 8h to obtain pretreated diatomaceous earth powder;

[0011] S13. Ultrasonicate graphene oxide in deionized water for 3 to 5 hours to obtain a graphene oxide aqueous solution with a concentration of 0.5 to 1 mg / mL, add pretreated diatomaceous earth powder to the graphene oxide aqueous solution, ultrasonically mix at 60 to 75° C. for 2 hours, and dry in a vacuum drying oven at 60° C. for 18 to 22 hours to obtain a secondary treated diatomaceous earth powder, mix 50 parts of a 45% by mass hydroiodic acid solution with 10 to 13 parts of the secondary treated diatomaceous earth powder, heat at 100° C. for 2 hours, filter, place the solid powder in an oven, treat at 100° C. for 24 hours, and cool to room temperature to obtain the modified diatomaceous earth.

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

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

[0014] As a preferred technical solution of the present invention, the preparation process of the modified nano metal oxide is:

[0015] S41, mixing magnesium chloride and molten carbonate in a mass ratio of 1:7, calcining at 500-600° C., keeping the temperature for 5-7 hours, cooling to room temperature, dispersing the calcined product with water, centrifuging and drying to obtain a solid, adding 3-5 parts of zirconium silicide to 15-20 parts of the solid, mixing evenly, and grinding the mixture in a ball mill at a speed of 400 r / min for 4 hours to obtain modified magnesium oxide nanoparticles;

[0016] S42, adding 30 to 40 parts of modified magnesium oxide nanoparticles and 20 to 30 parts of zirconium nitrate to 30 to 50 parts of ethanol by weight to prepare a precursor mixture, and preparing magnesium oxide-zirconium oxide composite powder by flame spray pyrolysis of the precursor mixture;

[0017] S43, calcining at 550-600° C. for 7-9 hours, washing the calcined product with water, centrifuging and drying to obtain the modified nano metal oxide.

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

[0019] As a preferred technical solution of the present invention, in step S42, methane is used as a 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 to 30 cm.

[0020] A method for preparing a nano inorganic composite heat storage material includes the following preparation processes:

[0021] By mass, 32 to 60 parts of modified diatomaceous earth, 33 to 47 parts of modified nano metal oxide and 4 to 7 parts of binder are fully stirred and dispersed at 40 to 60° C., and then ultrasonically treated at a pressure of 0.03 to 0.05 MPa for 3 to 8 minutes. The mixture is pre-pressed at 10 to 20 MPa and sintered at 130 to 150° C. After cooling to room temperature, it is secondary pressed at 19 to 30 MPa, and then ground by a ball mill at a speed of 400 r / min for 5 hours to obtain the nano inorganic composite heat storage material.

[0022] Beneficial effects of the present invention:

[0023] Through annealing treatment, the number of crystal defects in the structure of perovskite can be reduced, the perovskite crystal structure can be further improved, and some oxidized impurities can be removed to improve the crystal quality, thereby improving the stability of the material and preventing it from decomposing during use. Perovskite has high thermal stability and thermal conductivity and can maintain efficient heat conduction under high temperature conditions.

[0024] Diatomite is calcined at 700-730℃. The main chemical component of diatomite is SiO 2 During the high temperature calcination process, part of the amorphous SiO 2Converted into a crystalline form, which helps to improve its stability and durability. The roasting process can also cause the organic matter in the diatomite to burn or decompose. The removal of organic matter helps to improve the purity and adsorption performance of the diatomite. Diatomite itself has a large number of micropores and a high specific surface area. These characteristics make diatomite an ideal carrier and encapsulation material. In perovskite-modified diatomite, a good protection and dispersion environment can be provided for perovskite, and the addition of perovskite can further increase the specific surface area of ​​diatomite, thereby providing more heat energy storage locations, which can improve the heat storage efficiency, and perovskite can help diatomite reduce oxidation reactions and reduce heat energy loss. At the same time, through epoxy resin wrapping and curing, it can help perovskite to be more evenly compounded on the surface of diatomite, and the microscopic pores on the surface of diatomite improved by perovskite can adsorb monomers in epoxy resin, thereby enhancing heat resistance. It can also be in direct contact with the fluid medium and withstand the impact of the fluid medium. The high specific surface area and rich surface functional groups of graphene oxide can form more stable chemical bonds with the epoxy groups on the surface of epoxy resin, helping the graphene oxide to be more fully loaded on the structure of diatomaceous earth. Through hydroiodic acid treatment, the surface graphene oxide can be reduced to graphene, thereby improving the surface activity of the material.

[0025] The chemical properties of magnesium oxide are stable and can be used for a long time without being damaged by heat, thus maintaining its good heat storage performance. Magnesium oxide has a large specific heat capacity and can absorb a large amount of heat when heated and store it. Magnesium oxide has a high thermal conductivity and can quickly transfer heat, thereby increasing the efficiency of heat storage. This efficient thermal conductivity helps to achieve rapid storage and release of heat. Magnesium oxide can still maintain stable performance at high temperatures and is not easy to decompose or change.

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

[0027] Although magnesium oxide itself has high fire-resistant insulation properties, its thermal expansion coefficient is high, resulting in poor thermal shock resistance, while zirconium oxide has a melting point of up to 2700°C, strong thermal shock resistance, and high load softening temperature. Therefore, the composite material formed by combining modified zirconium oxide with magnesium oxide can significantly improve its thermal stability, making the heat storage material more stable when facing temperature fluctuations; the addition of zirconium oxide can promote the sintering of magnesium oxide, reduce the apparent porosity, and increase the relative density of the material, thereby optimizing the heat storage. 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] The nano-inorganic composite heat storage material prepared by the above treatment method in the present invention has a large specific surface area. The heat transfer performance of the traditional nano-inorganic composite material is improved by effectively loading the modified nano-metal oxide on the modified diatomite. 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 invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0030] In the following examples and comparative examples:

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

[0032] Diatomaceous earth: purchased from Shandong Zhengxing New Materials Co., Ltd., product number: CG8;

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

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

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

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

[0037] Magnesium chloride: purchased from Shanghai MacLean 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 Myrel Biochemical Technology Co., Ltd., product number: M90290;

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

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

[0043] Example 1

[0044] Preparation of modified diatomaceous earth:

[0045] S11, crushing the perovskite in a crusher, passing through a 200-mesh sieve, and then annealing for 4 hours at 150° C. in a nitrogen environment to obtain a perovskite powder;

[0046] S12, calcining diatomite in a muffle furnace at 700°C for 1 hour, cooling to room temperature after taking out, crushing with a pulverizer, and passing through a 200-mesh sieve; mixing 5 to 8 parts of perovskite powder with 20 parts of 10% epoxy resin acetone solution by mass, adding 25 parts of diatomite powder and soaking for 2 hours, distilling under reduced pressure for 2 hours, taking out and vacuum drying at 80°C for 8 hours to obtain pretreated diatomite powder;

[0047] S13. After ultrasonic treatment of graphene oxide in deionized water for 3 hours, a graphene oxide aqueous solution with a concentration of 0.5 mg / mL is obtained, and pretreated diatomaceous earth powder is added to the graphene oxide aqueous solution, and ultrasonic mixing is performed at 60° C. for 2 hours, and the mixture is dried in a vacuum drying oven at 60° C. for 18 hours to obtain a secondary treated diatomaceous earth powder, and 50 parts of a hydroiodic acid solution with a mass fraction of 45% are mixed with 10 parts of the secondary treated diatomaceous earth powder, and the mixture is heated at 100° C. for 2 hours. After filtering, the solid powder is placed in an oven, treated at 100° C. for 24 hours, and cooled to room temperature to obtain the modified diatomaceous earth.

[0048] Preparation of modified nano metal oxides:

[0049] S41, mixing magnesium chloride and molten carbonate in a mass ratio of 1:7, calcining at 500°C, keeping the temperature for 5 hours, cooling to room temperature, dispersing the calcined product with water, centrifuging and drying to obtain a solid, adding 3 parts of zirconium silicide to 15 parts of the solid, mixing evenly, and grinding the mixture in a ball mill at a speed of 400 r / min for 4 hours to obtain modified magnesium oxide nanoparticles;

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

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

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

[0053] By mass, at 40°C, 32 parts of modified diatomaceous earth, 33 parts of modified nano-metal oxide and 4 to 4 parts of aluminum phosphate were fully stirred and dispersed uniformly, and then ultrasonically treated at a pressure of 0.03 MPa for 3 minutes. The mixture was pre-pressed at 10 MPa and sintered at 130°C. After cooling to room temperature, it was secondary pressed at 19 MPa, and then ground by a ball mill at a speed of 400 r / min for 5 hours to obtain a nano-inorganic composite heat storage material.

[0054] Example 2

[0055] Preparation of modified diatomaceous earth:

[0056] S11, crushing the perovskite in a crusher, passing through a 200-mesh sieve, and then annealing at 150° C. for 4.5 h in a nitrogen environment to obtain a perovskite powder;

[0057] S12, calcining diatomite in a muffle furnace at 710°C for 1 hour, cooling to room temperature after taking out, crushing with a pulverizer, and passing through a 200-mesh sieve; by weight, fully stirring and mixing 6 parts of perovskite powder with 24 parts of 13% epoxy resin acetone solution, adding 29 parts of diatomite powder and soaking for 2.5 hours, distilling under reduced pressure for 2 hours, taking out and vacuum drying at 80°C for 8 hours to obtain pretreated diatomite powder;

[0058] S13. After ultrasonic treatment of graphene oxide in deionized water for 4 hours, a graphene oxide aqueous solution with a concentration of 0.7 mg / mL is obtained, and pretreated diatomaceous earth powder is added to the graphene oxide aqueous solution, and ultrasonic mixing is performed at 68° C. for 2 hours, and the mixture is dried in a vacuum drying oven at 60° C. for 19 hours to obtain a secondary treated diatomaceous earth powder, and 50 parts of a hydroiodic acid solution with a mass fraction of 45% are mixed with 12 parts of the secondary treated diatomaceous earth powder, and the mixture is heated at 100° C. for 2 hours. After filtering, the solid powder is placed in an oven, treated at 100° C. for 24 hours, and cooled to room temperature to obtain the modified diatomaceous earth.

[0059] Preparation of modified nano metal oxides:

[0060] S41, mixing magnesium chloride and molten carbonate in a mass ratio of 1:7, calcining at 560°C, keeping the temperature for 6 hours, cooling to room temperature, dispersing the calcined product with water, centrifuging and drying to obtain a solid, adding 4 parts of zirconium silicide to 17 parts of the solid, mixing evenly, and grinding the mixture in a ball mill at a speed of 400 r / min for 4 hours to obtain modified magnesium oxide nanoparticles;

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

[0062] S43, calcining at 570°C for 8 hours, washing the calcined product with water, centrifuging and drying to obtain the modified nano metal oxide.

[0063] Preparation of nano-inorganic composite heat storage materials:

[0064] By mass, at 50°C, 40 parts of modified diatomaceous earth, 41 parts of modified nano-metal oxide and 5 parts of aluminum phosphate were fully stirred and dispersed uniformly, and then ultrasonically treated at a pressure of 0.04 MPa for 6 minutes. The mixture was pre-pressed at 15 MPa and sintered at 140°C. After cooling to room temperature, it was secondary pressed at 22 MPa and ground by a ball mill at a speed of 400 r / min for 5 hours to obtain a nano-inorganic composite heat storage material.

[0065] Example 3

[0066] Preparation of modified diatomaceous earth:

[0067] S11, crushing the perovskite in a crusher, passing through a 200-mesh sieve, and then annealing for 5 hours at 150° C. in a nitrogen environment to obtain a perovskite powder;

[0068] S12, calcining diatomite in a muffle furnace at 730°C for 1 hour, cooling to room temperature after taking out, crushing with a pulverizer, and passing through a 200-mesh sieve; by weight, thoroughly stirring and mixing 8 parts of perovskite powder with 30 parts of 15% epoxy resin acetone solution, adding 35 parts of diatomite powder and soaking for 3 hours, distilling under reduced pressure for 2 hours, taking out and vacuum drying at 80°C for 8 hours to obtain pretreated diatomite powder;

[0069] S13. After ultrasonic treatment of graphene oxide in deionized water for 5 hours, a graphene oxide aqueous solution with a concentration of 1 mg / mL is obtained, and pretreated diatomaceous earth powder is added to the graphene oxide aqueous solution, and ultrasonic mixing is performed at 75°C for 2 hours, and the mixture is dried in a vacuum drying oven at 60°C for 22 hours to obtain a secondary treated diatomaceous earth powder, and 50 parts of a hydroiodic acid solution with a mass fraction of 45% are mixed with 13 parts of the secondary treated diatomaceous earth powder, and the mixture is heated at 100°C for 2 hours. After filtering, the solid powder is placed in an oven, treated at 100°C for 24 hours, and cooled to room temperature to obtain the modified diatomaceous earth.

[0070] Preparation of modified nano metal oxides:

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

[0072] S42, according to the mass fraction, 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 precursor mixture is prepared by flame spray pyrolysis to obtain magnesium oxide-zirconium oxide composite powder, wherein methane is used as a combustion-supporting gas in the flame spray pyrolysis method, the precursor mixture is atomized and ignited, and the effective sintering height of the flame is 30 cm;

[0073] S43, calcining at 600°C for 9 hours, washing the calcined product with water, centrifuging and drying to obtain the modified nano metal oxide.

[0074] Preparation of nano-inorganic composite heat storage materials:

[0075] By mass, at 60°C, 60 parts of modified diatomaceous earth, 47 parts of modified nano-metal oxide and 7 parts of aluminum phosphate were fully stirred and dispersed uniformly, and then ultrasonically treated at a pressure of 0.05 MPa for 8 minutes. The mixture was pre-pressed at 20 MPa and sintered at 150°C. After cooling to room temperature, it was secondary pressed at 30 MPa and ground by a ball mill at a speed of 400 r / min for 5 hours to obtain a nano-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 other operations are the same.

[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 other operations are the same.

[0080] Comparative Example 3

[0081] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, graphene oxide is not added when preparing the modified diatomite, and the other operations are the same.

[0082] Comparative Example 4

[0083] The difference between Comparative Example 4 and Example 1 is that the diatomaceous earth in Comparative Example 4 is not subjected to any modification treatment, and the other operations are the same.

[0084] Comparative Example 5

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

[0086] Comparative Example 6

[0087] The difference between Comparative Example 6 and Example 1 is that zirconium nitrate is not added during the preparation of the modified nano-metal oxide in Comparative Example 6, and the other operations are the same.

[0088] Comparative Example 7

[0089] The difference between Comparative Example 7 and Example 1 is that in Comparative Example 7, no molten carbonate is added when preparing the modified magnesium oxide nanoparticles, and the other operations are the same.

[0090] Performance Test:

[0091] The thermal conductivity was measured by a thermal conductivity meter, and the data are as follows:

[0092]

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

[0094] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A nano inorganic composite heat storage material, characterized in that: The nano inorganic composite heat storage material uses modified diatomite as a carrier and modified nano metal oxide as a load material, which are bonded by a binder, wherein the preparation process of the modified diatomite is as follows: S11, crushing the perovskite in a crusher, passing through a 200-mesh sieve, and then annealing at 150° C. for 4 to 5 hours in a nitrogen environment to obtain a perovskite powder; S12, calcining diatomaceous earth in a muffle furnace at 700-730°C for 1h, cooling to room temperature after taking out, crushing with a pulverizer, and passing through a 200-mesh sieve; mixing 5-8 parts of perovskite powder and 20-30 parts of epoxy resin acetone solution by mass, adding 25-35 parts of diatomaceous earth powder and soaking for 2-3h, distilling under reduced pressure for 2h, taking out and vacuum drying at 80°C for 8h to obtain pretreated diatomaceous earth powder; S13. Ultrasonicate graphene oxide in deionized water for 3 to 5 hours to obtain a graphene oxide aqueous solution with a concentration of 0.5 to 1 mg / mL, add pretreated diatomaceous earth powder to the graphene oxide aqueous solution, ultrasonically mix at 60 to 75° C. for 2 hours, and dry in a vacuum drying oven at 60° C. for 18 to 22 hours to obtain a secondary treated diatomaceous earth powder, mix 50 parts of a 45% by mass hydroiodic acid solution with 10 to 13 parts of the secondary treated diatomaceous earth powder, heat at 100° C. for 2 hours, filter, place the solid powder in an oven, treat at 100° C. for 24 hours, and cool to room temperature to obtain the modified diatomaceous earth.

2. The nano-inorganic composite heat storage material according to claim 1, characterized in that: The binder is aluminum phosphate or borax.

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

4. The nano-inorganic composite heat storage material according to claim 1, characterized in that: The preparation process of the modified nano metal oxide is as follows: S41, mixing magnesium chloride and molten carbonate in a mass ratio of 1:7, calcining at 500-600° C., keeping the temperature for 5-7 hours, cooling to room temperature, dispersing the calcined product with water, centrifuging and drying to obtain a solid, adding 3-5 parts of zirconium silicide to 15-20 parts of the solid, mixing evenly, and grinding the mixture in a ball mill at a speed of 400 r / min for 4 hours to obtain modified magnesium oxide nanoparticles; S42, adding 30 to 40 parts of modified magnesium oxide nanoparticles and 20 to 30 parts of zirconium nitrate to 30 to 50 parts of ethanol by weight to prepare a precursor mixture, and preparing magnesium oxide-zirconium oxide composite powder by flame spray pyrolysis of the precursor mixture; S43, calcining at 550-600°C for 7-9 hours, washing the calcined product with water, centrifuging and drying to obtain the modified nano metal oxide.

5. The nano-inorganic composite heat storage material according to claim 1, characterized in that: In step S41, the molten carbonate salt is a mixture of potassium carbonate and sodium carbonate in a mass ratio of 3:

4.

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

7. A method for preparing the nano inorganic composite heat storage material according to any one of claims 1 to 6, characterized in that: The preparation process includes the following: By mass, 32 to 60 parts of modified diatomaceous earth, 33 to 47 parts of modified nano metal oxide and 4 to 7 parts of binder are fully stirred and dispersed at 40 to 60° C., and then ultrasonically treated at a pressure of 0.03 to 0.05 MPa for 3 to 8 minutes. The mixture is pre-pressed at 10 to 20 MPa and sintered at 130 to 150° C. After cooling to room temperature, it is secondary pressed at 19 to 30 MPa, and then ground by a ball mill at a speed of 400 r / min for 5 hours to obtain the nano inorganic composite heat storage material.

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