A superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material and its preparation method and application

Abstract

The present invention discloses a super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage material and a preparation method and application thereof, which belongs to the field of solid waste-based phase change energy storage materials. Raw materials are weighed according to mass parts, and carbon self-growth modified fly ash-based porous materials, spectrum adjustment materials and phase change materials are mixed by vacuum impregnation or normal pressure heating to obtain carbon self-growth modified fly ash-based photothermal conversion composite phase change heat storage materials. The carbon self-growth modified fly ash-based photothermal conversion composite phase change heat storage materials and hydrophobic materials are mixed, stirred and dried to obtain super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage materials. The present invention makes up for the defects of high preparation cost of composite phase change heat storage support materials, difficulty in preparing fly ash-based porous materials, and low thermal conductivity of fly ash-based composite phase change heat storage materials.

Description

Technical Field

[0001] The present invention belongs to the field of solid waste-based phase change energy storage materials, and particularly relates to a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material, a preparation method thereof, and an application thereof. Background Art

[0002] The icing disaster of high-voltage transmission lines seriously affects the safe and stable transportation of electric power, and is an important cause of accidents such as wire breakage, tower collapse, and power grid disconnection. At present, the commonly used mechanical de-icing method has a large workload, low efficiency, and mechanical vibration is likely to cause the transmission line to break, resulting in damage to the power system. Therefore, in order to improve the ice disaster resistance ability of the power grid, it is urgent to develop an efficient, convenient, and economical means to prevent icing disasters of transmission lines. Research shows that hydrophobic coatings can prevent icing of lines by promoting the rapid rolling of water droplets, delaying ice nucleation, and reducing ice adhesion force. However, relying solely on the hydrophobicity of the coating cannot completely prevent the formation and growth of ice layers, and effective measures cannot be taken for the cables after icing.

[0003] Phase change heat storage materials, as a kind of material that can store environmental heat and release heat when needed, have been applied in aspects such as anti-icing and anti-freezing. For photothermal conversion phase change heat storage materials, they can absorb solar energy and convert it into latent heat for storage; when the environmental temperature is low, heat is released through a reversible phase change process to ensure that the object temperature is maintained at an appropriate level. Therefore, developing a composite phase change material with both hydrophobicity and photothermal conversion heat storage functions for power grid transmission lines to replace traditional mechanical de-icing means can effectively solve the problem of icing of transmission lines and help the safe and stable operation of the power system.

[0004] CN116278277A discloses a photothermal conversion bionic anti- / de-icing functional surface, which is mainly formed by stacking an intelligent deformation layer, a photothermal conversion layer, and a heat storage layer. Its main principle is that the photothermal conversion layer absorbs solar heat to cause temperature changes, thereby causing the intelligent deformation layer to deform and achieving the effect of ice removal. However, the minimum thickness of this material still reaches 2.52 mm, and the maximum thickness reaches 6.1 mm. Limited by factors such as the large volume and weight of this material, it cannot meet the requirements of lightweight transmission lines to reduce the load on transmission towers.

[0005] CN113462363A discloses a photothermal phase change energy storage superhydrophobic anti-freezing particle, which mainly improves the thermal conductivity of the phase change material and the anti-freezing effect by adding silver particles to the energy storage material. However, silver particles are expensive, and the cost of anti-freezing particles is relatively high, which is not conducive to large-scale promotion and implementation of power grid lines.

[0006] CN116333519A discloses a fly ash-based hydrophobic coating prepared by mixing polyethylene wax and fly ash. It mainly requires fly ash with a particle size of 7-9 μm and polyethylene wax particles with a particle size below 60 mesh. After preparing the hydrophobic coating by mixing fly ash, polyethylene wax and water in proportion, a superhydrophobic coating is prepared through steps such as mixing, drying, heat curing, and polishing. This preparation method has numerous steps and is difficult to control during the operation process. In addition, this coating is only applicable to the ice-covering prevention stage and cannot achieve the ice-melting process after ice formation.

[0007] As a composite phase change material applicable to transmission lines for preventing ice-covering disasters with both hydrophobicity and photothermal conversion and heat storage functions, comprehensive factors such as low-cost and easily available raw materials, simple preparation, and suitability for large-scale promotion and use in power grid lines must be considered on the premise of ensuring strong hydrophobicity, high photothermal conversion efficiency, and energy storage density. Summary of the Invention

[0008] The purpose of the present invention is to provide a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material, its preparation method and application to solve the problems existing in the above-mentioned prior art. The present invention uses fly ash alkali leaching solution and calcium-based oxygen-containing compounds as raw materials, and adopts an alkali hydrothermal method to prepare the support framework of the composite phase change heat storage material, and adds a carbon source during the hydrothermal process to improve the thermal conductivity and photothermal conversion efficiency of the composite material. By vacuum impregnation method or atmospheric pressure heating mixing, the spectral adjustment material and the phase change substance are filled into the carbon self-grown fly ash-based porous framework, and blended with the hydrophobic material to prepare a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material with high-efficiency spectral selectivity, photothermal conversion performance, and hydrophobic performance.

[0009] One of the technical solutions provided by the present invention:

[0010] A superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material, comprising the following raw materials in parts by mass: 65-80 parts of phase change substance, 10-32 parts of carbon self-grown modified fly ash-based porous material, 2-5 parts of spectral adjustment material, and 10-15 parts of hydrophobic material.

[0011] Preferably, the phase change substance is one or more of polyethylene glycol, tetradecane, pentadecane, n-octanoic acid, lauric acid, stearic acid, n-decanoic acid, myristic acid, and methyl laurate; the spectral adjustment material is one or more of zinc oxide nanoparticles, titanium nitride nanoparticles, titanium dioxide nanoparticles, vanadium dioxide, tungsten dioxide, and indium tin oxide; the hydrophobic material is one or more of polydimethylsiloxane, hexamethyldisilazane, dodecyltriethoxysilane, and methylhydrogen silicone oil.

[0012] Another technical solution provided by the present invention:

[0013] A preparation method of a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material, which weighs raw materials according to parts by mass, and mixes a carbon self-grown modified fly ash-based porous material, a spectral regulation material and a phase change substance through a vacuum impregnation method or an atmospheric pressure heating method to obtain a carbon self-grown modified fly ash-based photothermal conversion composite phase change heat storage material. Then, the carbon self-grown modified fly ash-based photothermal conversion composite phase change heat storage material and a hydrophobic material are mixed, stirred and dried to obtain a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material.

[0014] Preferably, the mixing temperature of the vacuum impregnation method is 60-100°C, the vacuum degree is -0.1 MPa, and the holding time is 0.5-2 h; the temperature of the atmospheric pressure heating mixing method is 60-100°C, and the holding time is 0.5-2 h.

[0015] Preferably, the preparation method of the carbon self-grown modified fly ash-based porous material is as follows: adding a calcium-based oxygen-containing compound and a carbon source into the fly ash alkali leaching solution, mixing evenly to obtain a hydrothermal ligand solution, performing hydrothermal treatment, centrifuging and filtering to obtain a carbon self-grown modified fly ash-based precursor solid product, and performing carbonization treatment to obtain a carbon self-grown modified fly ash-based porous material.

[0016] More preferably, the calcium-based oxygen-containing compound is one or more of calcium oxide, calcium hydroxide, calcium nitrate, calcium carbonate, calcium sulfate, calcium acetate, calcium phosphate and calcium dihydrogen phosphate; the carbon source is one or more of furfural, glucose, cellulose, polyacrylonitrile, lignin and hemicellulose.

[0017] Even more preferably, the mass ratio of the fly ash to the calcium-based oxygen-containing compound is (15:1)-(30:1).

[0018] When too much calcium-based oxygen-containing compound is added, the calcium-based oxygen-containing compound cannot react completely, resulting in blocked pores and affecting the porosity. When too little calcium-based oxygen-containing compound is added, the yield will be relatively low.

[0019] Even more preferably, the mass ratio of the calcium-based oxygen-containing compound to the carbon source is (1:10)-(1:20).

[0020] Even more preferably, the temperature of the hydrothermal treatment is 150-250°C, and the time is 8-20 h.

[0021] Even more preferably, the carbonization treatment is as follows: in an inert mixed atmosphere, at 600-800°C, perform carbonization treatment for 10-60 min.

[0022] The inert mixed atmosphere is a mixture of nitrogen and argon in a ratio of (1:1)-(3:1), and the gas flow rate is 70-100 mL / min.

[0023] More preferably, the fly ash alkali leaching solution is prepared by adding fly ash to a pre-prepared alkali composite solution, mixing and stirring, alkali washing, centrifugal filtration, and obtaining a supernatant liquid, which is the fly ash alkali leaching solution.

[0024] The prior art still stays at modifying the surface of the fly ash microstructure to improve the pore structure of its surface, and then adsorbing the phase change material, but this method has a poor effect on improving the pores, resulting in a low adsorption amount of the phase change material, and the content of the components with high thermal conductivity in the fly ash is low, so the thermal conductivity of the composite material formed is poor. The present invention forms silicate ions by reacting the alkali composite solution with the silicon-containing components in the fly ash, and the silicate ions further react with the calcium-based oxygen-containing compound under hydrothermal conditions, and the products continue to accumulate and grow in different directions, and finally form a porous material with a three-dimensional interconnected network structure, which provides sufficient space for the filling of the phase change material, and the carbon precursor provided by the carbon source grows on the surface and inside of the porous structure during the hydrothermal process. After carbonization treatment, a carbon self-growing modified fly ash-based porous material is formed, which can enhance the thermal conductivity of the composite material. In addition, the present invention also affects its porosity by controlling the hydrothermal time and hydrothermal temperature.

[0025] The specific preparation method of the carbon self-growth modified fly ash-based porous material is as follows: placing fly ash in a pre-prepared alkali composite solution, mixing and stirring it thoroughly, washing it with alkali, and centrifuging and filtering it to obtain the upper clear liquid, which is the fly ash alkali leaching solution; adding calcium-based oxygen-containing compounds and carbon sources to the fly ash alkali leaching solution, stirring, and mixing them thoroughly to obtain a hydrothermal ligand solution; charging the hydrothermal ligand solution into a hydrothermal reactor, performing hydrothermal treatment, and after the hydrothermal treatment is completed, centrifuging and filtering it to obtain a carbon self-growth modified fly ash-based precursor solid product; and carbonizing the solid product under an inert mixed atmosphere to obtain a carbon self-growth modified fly ash-based porous material.

[0026] More preferably, the alkaline composite solution is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate solution; the concentration of the alkaline composite solution is 1-5 mol / L, the temperature of alkaline washing is 60-150°C, and the time is 30-120 min.

[0027] The third technical solution provided by the present invention is:

[0028] An application of the above-mentioned super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage material in preventing power transmission lines from icing disasters.

[0029] Technical principle of the present invention:

[0030] In the present invention, the structure of fly ash is reconstructed by an alkaline hydrothermal method, and the obtained porous fly ash has a high porosity. A carbon source is added during the hydrothermal process, so that hydrothermal carbon with high thermal conductivity adheres to the surface of the porous material generated by hydrothermal treatment, thereby improving the energy storage efficiency of the composite phase change heat storage material. The added spectral adjustment material has a high absorption rate in the solar spectrum range, further improving the photothermal conversion efficiency of the composite phase change heat storage material; the phase change substance in the composition of the composite phase change heat storage material has a high mass fraction and an adjustable enthalpy value.

[0031] Advantages of the present invention:

[0032] The superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material provided by the present invention has the advantages of high thermal conductivity, high visible light absorption rate, high stability, etc. The high pore volume, high thermal conductivity, etc. of the carbon self-grown modified fly ash porous material enable the latent heat of phase change of the composite phase change heat storage material to reach 65-80% of the theoretical latent heat of the phase change substance, and the thermal conductivity of the obtained composite phase change heat storage material is increased to 2-5 times that of the phase change substance; the composite phase change heat storage material has excellent thermal stability and cycle stability, and no leakage occurs after 1000 cycles, and it still maintains shape stability under the condition of long-term heating or even overheating of the phase change substance. The surface contact angle of the coating formed by the composite phase change heat storage material is greater than 150°, and the rolling angle is less than 10°, having excellent superhydrophobic performance.

[0033] The fly ash raw material used in the superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material disclosed by the present invention has the advantages of environmental friendliness, rich raw materials, low price, suitability for mass production, etc. The carbon self-grown modified fly ash-based porous material prepared by the present invention benefits from the addition of hydrothermal carbon and has the advantage of high thermal conductivity, overcoming the problem of low thermal conductivity of the phase change substance and ordinary fly ash.

[0034] The present invention makes up for the defects of high preparation cost of the composite phase change heat storage support material, difficult preparation of fly ash-based porous materials, low thermal conductivity of fly ash-based composite phase change heat storage materials, etc. Moreover, the composite phase change heat storage material has the advantages of low cost, not easy to leak, high thermal conductivity, and good photothermal conversion performance. It provides an effective method for the high-value utilization of fly ash solid waste in the fields of thermal energy storage and efficient solar energy conversion. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0036] Figure 1 SEM image of the carbon self - grown modified fly ash - based porous material prepared in Example 1;

[0037] Figure 2 SEM image of the super - hydrophobic fly ash - based photothermal conversion composite phase - change heat storage material prepared in Example 1. Detailed implementation manners

[0038] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be regarded as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0039] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0041] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the description of the present invention, which are obvious to those skilled in the art. Other implementation manners obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of this application are only exemplary.

[0042] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open - ended terms, meaning including but not limited to.

[0043] The room temperature in the present invention refers to 25 ± 2 °C, and the normal pressure refers to 0.1013 MPa.

[0044] In the embodiments of the present invention, "parts" refers to "parts by mass" unless otherwise specified.

[0045] An embodiment of the present invention provides a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material, which comprises the following raw materials in parts by mass: 65-80 parts of a phase change substance, 10-32 parts of a carbon self-grown modified fly ash-based porous material, 2-5 parts of a spectral regulation material, and 10-15 parts of a hydrophobic material.

[0046] The embodiment of the present invention also provides a preparation method of a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material: The carbon self-grown modified fly ash-based porous material uses fly ash alkali leaching solution as the raw material. The porous material prepared by alkali hydrothermal chemical synthesis and high-temperature carbonization processes has a high porosity and participates in the preparation as a support framework. The vacuum impregnation method or atmospheric pressure heating mixing method is used to uniformly fill the phase change substance and the spectral regulation material into the pores of the carbon self-grown modified fly ash-based porous material, and the hydrophobic material is uniformly dispersed on the surface of the composite material by a blending method. The carbon self-grown modified fly ash-based porous material, as the support framework, provides a large number of pores for the phase change substance to stably adhere. The high thermal conductivity of hydrothermal carbon and the light absorption characteristics of the spectral regulation material provide good thermal conductivity and photothermal conversion efficiency for the composite phase change heat storage material. The selective spectral absorption function of the spectral regulation material enhances the absorption capacity of the target wavelength, and the hydrophobic material improves the overall hydrophobic performance of the composite phase change heat storage material.

[0047] Example 1

[0048] A preparation method of a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material

[0049] 1) Add 20 g of fly ash into 100 mL of sodium hydroxide solution (3 mol / L), heat and stir at 80 °C for 0.5 h, filter the obtained mixed solution, take the filtrate part as the fly ash alkali leaching solution, add 0.8 g of calcium oxide and 13 g of furfural, stir and mix, and carry out hydrothermal reaction at 180 °C for 12 h; Centrifuge and filter the solution after the hydrothermal reaction to obtain a carbon self-grown modified fly ash-based precursor solid product; Heat the obtained solid product from room temperature to 600 °C and keep it warm for 0.5 h in an atmosphere of nitrogen and argon with a mixing volume ratio of 1:1 to prepare a carbon self-grown modified fly ash-based porous material. The specific surface area of the prepared porous material is 68.5 m 2 / g, much higher than 2.7 m 2 / g of ordinary fly ash, Figure 1 is the SEM image of the carbon self-grown modified fly ash-based porous material prepared in this example. It can be seen from Figure 1 that the obtained porous material has relatively developed pores, providing sufficient space for the adsorption of a large amount of phase change substances.

[0050] 2) Mix 0.15 g of the porous material prepared in step 1), 0.04 g of vanadium dioxide, and 0.7 g of polyethylene glycol by grinding, place them in a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa, wait for the temperature of the vacuum container to reach 80 °C and then keep it warm for 0.5 h, cool the vacuum container, take out the carbon self-grown modified fly ash-based composite phase change heat storage material, mix the obtained composite phase change heat storage material with 0.11 g of polydimethylsiloxane, stir and disperse evenly and then dry (70 °C, 12 h) to obtain a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material. Figure 2 SEM image of the composite phase change heat storage material prepared in this example. From Figure 2 it can be seen that the pores of the porous material can be completely filled, and the composite effect is good.

[0051] The latent heat of phase change of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 68% of that of pure polyethylene glycol, and the thermal conductivity is 0.8 W / m·K, which is 4 times that of pure polyethylene glycol (0.2 W / m·K). The photothermal conversion efficiency of the composite phase change heat storage material prepared in this example in the solar spectrum range reaches 80.3%.

[0052] Example 2

[0053] Preparation method of a superhydrophobic fly ash-based photothermal conversion phase change heat storage composite phase change material

[0054] 1) Add 20 g of fly ash to 100 mL of sodium hydroxide solution (4 mol / L), heat and stir at 90 °C for 0.5 h, filter the obtained mixture, take the filtrate part as the fly ash alkali leaching solution, add 0.7 g of calcium hydroxide and 10 g of glucose and then stir and mix, carry out hydrothermal reaction at 180 °C for 12 h; centrifuge and filter the solution after hydrothermal reaction to obtain a carbon self-grown modified fly ash-based precursor solid product; heat the obtained solid product from room temperature to 700 °C and keep it warm for 0.5 h under an atmosphere of nitrogen and argon with a mixing ratio of 2:1 to obtain a carbon self-grown modified fly ash-based porous material. The specific surface area of the prepared porous material is 65.3 m 2 / g;

[0055] 2) Mix 0.1 g of the porous material prepared in step 1), 0.05 g of tungsten dioxide, and 0.75 g of stearic acid by grinding, place them in a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa, wait for the temperature of the vacuum container to reach 90 °C and then keep it warm for 0.5 h, cool the vacuum container, take out the carbon self-grown modified fly ash-based composite phase change heat storage material; mix the obtained composite phase change heat storage material with 0.1 g of hexamethyldisilazane, stir and disperse evenly and then dry (60 °C, 15 h) to obtain a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material.

[0056] The latent heat of phase change of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 73% of that of pure stearic acid, and the thermal conductivity is 0.7 W / m·K, which is 2.3 times that of pure stearic acid (0.3 W / m·K). The photothermal conversion efficiency of the composite phase change heat storage material prepared in this example within the solar spectrum range reaches 82.6%.

[0057] Example 3

[0058] Preparation method of a superhydrophobic fly ash-based photothermal conversion phase change heat storage composite phase change material

[0059] 1) Add 20 g of fly ash to 200 mL of potassium hydroxide solution (1 mol / L), heat and stir at 120 °C for 1.5 h, filter the obtained mixture, take the filtrate part as the fly ash alkali leaching solution, add 1 g of calcium oxide powder and 12 g of furfural, stir and mix, and carry out hydrothermal reaction at 165 °C for 10 h; centrifuge and filter the solution after the hydrothermal reaction to obtain a carbon self-grown modified fly ash-based precursor solid product; heat the obtained solid product from room temperature to 700 °C and keep it warm for 1 h in an atmosphere of nitrogen and argon with a mixing ratio of 3:1 to prepare a carbon self-grown modified fly ash-based porous material. The specific surface area of the prepared porous material is 64.7 m 2 / g;

[0060] 2) Grind and mix 0.15 g of the porous material prepared in step 1), 0.05 g of nano-zinc oxide and 0.7 g of lauric acid, put them into a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa, wait for the temperature of the vacuum container to reach 70 °C and keep it warm for 0.5 h; cool the vacuum container, take out the carbon self-grown modified fly ash-based composite phase change heat storage material, mix the obtained composite phase change heat storage material with 0.1 g of dodecyltriethoxysilane, stir and disperse evenly and then dry to obtain a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material.

[0061] The latent heat of phase change of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 67% of that of pure lauric acid, and the thermal conductivity is 0.8 W / m·K, which is 4 times that of pure lauric acid (0.2 W / m·K). The photothermal conversion efficiency of the composite phase change heat storage material prepared in this example within the solar spectrum range reaches 85.1%.

[0062] Example 4

[0063] Preparation method of a superhydrophobic fly ash-based photothermal conversion phase change heat storage composite phase change material

[0064] 1) Add 20 g of fly ash to 100 mL of potassium hydroxide solution (2 mol / L), heat and stir at 90 °C for 1 h. Filter the resulting mixture, and take part of the filtrate as the alkali leaching solution of fly ash. Add 1.2 g of calcium oxide powder and 15 g of polyacrylonitrile, stir and mix, and carry out hydrothermal reaction at 220 °C for 12 h. Centrifuge and filter the solution after hydrothermal reaction to obtain the carbon self-grown modified fly ash-based precursor solid product. Heat the obtained solid product from room temperature to 800 °C and keep it at this temperature for 1 h under an atmosphere of nitrogen and argon with a mixing ratio of 1:1 to prepare the carbon self-grown modified fly ash-based porous material. The specific surface area of the prepared porous material is 65.8 m 2 / g;

[0065] 2) Grind and mix 0.18 g of the porous material prepared in step 1), 0.03 g of tungsten dioxide and 0.67 g of lauric acid, put them into a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa, and wait for the temperature of the vacuum container to reach 70 °C and then keep it at this temperature for 0.5 h. Cool the vacuum container, take out the carbon self-grown modified fly ash-based composite phase change heat storage material, mix the obtained composite phase change heat storage material with 0.12 g of methyl hydrogen silicone oil, stir and disperse evenly, and then dry (80 °C, 10 h) to obtain the superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material.

[0066] The phase change latent heat of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 66% of that of pure lauric acid, and the thermal conductivity is 0.8 W / m·K, which is 4 times that of pure lauric acid (0.2 W / m·K). The photothermal conversion efficiency of the composite phase change heat storage material prepared in this example in the solar spectrum range reaches 79.2%.

[0067] Example 5

[0068] A preparation method of a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material

[0069] 1) Add 20 g of fly ash to 100 mL of lithium hydroxide solution (5 mol / L), heat and stir at 60 °C for 0.5 h. Filter the resulting mixture, and take part of the filtrate as the alkali leaching solution of fly ash. Add 0.9 g of calcium nitrate powder and 10 g of cellulose, stir and mix, and carry out hydrothermal reaction at 220 °C for 12 h. Centrifuge and filter the solution after hydrothermal reaction to obtain the carbon self-grown modified fly ash-based precursor solid product. Heat the obtained solid product from room temperature to 600 °C and keep it at this temperature for 1 h under an atmosphere of nitrogen and argon with a mixing ratio of 3:1 to prepare the carbon self-grown modified fly ash-based porous material. The specific surface area of the prepared porous material is 66.7 m 2 / g;

[0070] 2) Grind and mix 0.12 g of the porous material prepared in step 1), 0.02 g of nano-titanium dioxide, and 0.75 g of polyethylene glycol, put them into a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa, wait for the temperature of the vacuum container to reach 90 °C and then keep it warm for 0.5 h, cool the vacuum container, take out the carbon self-growth modified fly ash-based composite phase change heat storage material, mix the obtained composite phase change heat storage material with 0.11 g of polydimethylsiloxane, stir and disperse evenly and then dry (70 °C, 12 h) to obtain a superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material.

[0071] The phase change latent heat of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 75% of that of pure polyethylene glycol, and the thermal conductivity is 0.7 W / m·K, which is 3.5 times that of pure polyethylene glycol (0.2 W / m·K). The photothermal conversion efficiency of the composite phase change heat storage material prepared in this example within the solar spectrum range reaches 75.9%.

[0072] Comparative Example 1

[0073] 1) Add 20 g of fly ash to 100 mL of sodium hydroxide solution (2 mol / L), heat and stir at 60 °C for 0.5 h, filter the obtained mixture, take the filtrate part as the fly ash alkali leaching solution, add 0.7 g of calcium oxide powder, stir and mix, carry out hydrothermal reaction at 180 °C for 12 h, filter and separate the solid and liquid from the hydrothermal reaction solution, dry the solid part at 85 °C for 15 h, and the dried solid powder is the modified fly ash porous material;

[0074] 2) Grind and mix 0.3 g of the porous material prepared in step 1) with 0.65 g of polyethylene glycol, put them into a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa, wait for the temperature of the vacuum container to reach 80 °C and then keep it warm for 0.5 h, cool the vacuum container, take out the modified fly ash-based composite phase change material, mix the obtained composite phase change material with 0.05 g of polydimethylsiloxane, stir and disperse evenly and then dry (100 °C, 5 h) to obtain a hydrophobic fly ash-based composite phase change heat storage material.

[0075] The phase change latent heat of the obtained hydrophobic fly ash-based composite phase change heat storage material is 61% of that of pure polyethylene glycol. The thermal conductivity is 1.1 times that of pure polyethylene glycol. The photothermal conversion efficiency of the composite phase change material prepared in this comparative example within the solar spectrum range is 35.6%.

[0076] Comparative Example 2

[0077] 1) Add 10 g of fly ash into 100 mL of potassium hydroxide solution (3 mol / L), heat and stir at 30 °C for 0.5 h. Filter the obtained mixture, take a part of the filtrate as the alkali leaching solution of fly ash, add 0.5 g of calcium hydroxide powder, stir and mix. Carry out hydrothermal reaction at 130 °C for 5 h. Filter the solution after hydrothermal reaction to separate the solid and the liquid. Dry the solid part at 80 °C for 15 h. The dried solid powder is the modified fly ash porous material;

[0078] 2) Grind and mix 0.35 g of the porous material prepared in step 1) with 0.59 g of stearic acid, put it into a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa. Wait until the temperature of the vacuum container reaches 50 °C and keep it warm for 0.5 h. Cool the vacuum container, take out the modified fly ash-based composite phase change material. Mix the obtained composite phase change material with 0.06 g of dodecyltriethoxysilane, stir and disperse evenly and then dry (70 °C, 12 h) to obtain the hydrophobic fly ash-based composite phase change heat storage material.

[0079] The latent heat of phase change of the obtained hydrophobic fly ash-based composite phase change heat storage material is 57% of that of pure stearic acid. The thermal conductivity is 1.3 times that of pure stearic acid. The photothermal conversion efficiency of the composite phase change material prepared in this comparative example within the solar spectrum range is 33.5%.

[0080] Comparative Example 3

[0081] 1) Slowly add 10 g of fly ash into 100 mL of potassium hydroxide solution (4 mol / L), heat and stir at 50 °C for 0.5 h. Filter the obtained mixture, take a part of the filtrate as the alkali leaching solution of fly ash, add 0.6 g of calcium hydroxide powder, stir and mix. React at 90 °C for 6 h. Filter the reaction product to separate the solid and the liquid. Dry the solid part at 60 °C for 24 h. The dried solid powder is the modified fly ash porous material.

[0082] 2) Grind and mix 0.23 g of the porous material prepared in step 1) with 0.7 g of lauric acid, put it into a vacuum heating container, use a vacuum pump to evacuate to -0.1 MPa. Wait until the temperature of the vacuum container reaches 30 °C, cool the vacuum container, take out the modified fly ash-based composite phase change material. Mix the obtained composite phase change material with 0.07 g of hexamethyldisilazane, stir and disperse evenly and then dry (80 °C, 12 h) to obtain the hydrophobic fly ash-based composite phase change heat storage material.

[0083] The latent heat of phase change of the obtained hydrophobic fly ash-based composite phase change heat storage material is 57% of that of pure lauric acid. The thermal conductivity is 1.3 times that of pure lauric acid. The photothermal conversion efficiency of the composite phase change material prepared in this comparative example within the solar spectrum range is 36.1%.

[0084] Comparative Example 4

[0085] Same as Example 1, except that furfural was not added in step 1).

[0086] The latent heat of phase change of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 63% of that of pure polyethylene glycol, and the thermal conductivity is 1.3 times that of pure polyethylene glycol. The photothermal conversion efficiency of the composite phase change material prepared in this comparative example within the solar spectrum range is 70.6%.

[0087] Comparative Example 5

[0088] Same as Example 1, except that vanadium dioxide was not added in step 2).

[0089] The latent heat of phase change of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 67% of that of pure polyethylene glycol, and the thermal conductivity is 0.7 W / m·K, which is 3.5 times that of pure polyethylene glycol (0.2 W / m·K). The photothermal conversion efficiency of the composite phase change material prepared in this comparative example within the solar spectrum range is 51.3%.

[0090] Comparative Example 6

[0091] 1) Add 20 g of fly ash to 100 mL of sodium hydroxide solution (3 mol / L), heat and stir at 80 °C for 0.5 h, filter the obtained mixture, take the filtrate part as the fly ash alkali leaching solution, add 1.5 g of calcium oxide and 15 g of furfural, stir and mix, and carry out hydrothermal reaction at 180 °C for 12 h; centrifuge and filter the solution after hydrothermal reaction to obtain a carbon self-grown modified fly ash-based precursor solid product; heat the obtained solid product from room temperature to 600 °C and keep it warm for 0.5 h in an atmosphere of nitrogen and argon with a mixing ratio of 1:1 to prepare a carbon self-grown modified fly ash-based porous material, and the specific surface area of the prepared porous material is 39.7 m 2 / g;

[0092] Step 2) is the same as Example 1.

[0093] The latent heat of phase change of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 37% of that of pure polyethylene glycol, and the thermal conductivity is 0.8 W / m·K, which is 4 times that of pure polyethylene glycol (0.2 W / m·K). The photothermal conversion efficiency of the composite phase change material prepared in this comparative example within the solar spectrum range is 76%.

[0094] Comparative Example 7

[0095] 1) Add 20 g of fly ash into 100 mL of sodium hydroxide solution (3 mol / L), heat and stir at 80 °C for 0.5 h. Filter the obtained mixture, take part of the filtrate as the alkali leaching solution of fly ash, add 0.4 g of calcium oxide and 8 g of furfural, stir and mix, and carry out hydrothermal reaction at 180 °C for 12 h; Centrifuge and filter the solution after the hydrothermal reaction to obtain a carbon self-grown modified fly ash-based precursor solid product; Heat the obtained solid product from room temperature to 600 °C and keep it warm for 0.5 h in an atmosphere of nitrogen and argon with a mixing ratio of 1:1 to prepare a carbon self-grown modified fly ash-based porous material. The specific surface area of the prepared porous material is 60.7 m 2 / g, and the yield of the porous material decreases by about 50%;

[0096] Step 2) is the same as Example 1.

[0097] The phase change latent heat of the obtained superhydrophobic fly ash-based photothermal conversion composite phase change heat storage material is 63% of that of pure polyethylene glycol, and the thermal conductivity is 0.7 W / m·K, which is 3.5 times that of pure polyethylene glycol (0.2 W / m·K). The photothermal conversion efficiency of the composite phase change material prepared in this comparative example within the solar spectrum range is 79.6%.

[0098] Application Example 1

[0099] Prepare composite coatings from the composite phase change materials prepared in Examples 1-5 and Comparative Examples 1-7 respectively, and verify the hydrophobic performance of the coatings through simulation experiments.

[0100] The specific measurement method is as follows: Take 1 g of the composite phase change materials prepared in Examples 1-5 and Comparative Examples 1-7 respectively, disperse them in 20 mL of ethyl acetate solvent, stir at room temperature to form a mixed solution, and spray the mixed solution onto the surface of a copper sheet with a spray gun. After drying, a composite coating is formed. Test the surface contact angle and rolling angle of the obtained composite coating. The experimental results are shown in Tables 1 and 2.

[0101] Table 1

[0102]

[0103] Table 2

[0104]

[0105] It can be seen from Tables 1 and 2 that the composite coatings formed by the composite phase change heat storage materials prepared in Examples 1-5 have a relatively high surface contact angle and a relatively low rolling angle, indicating that the superhydrophobic fly ash-based photothermal conversion phase change heat storage composite phase change material prepared by the alkali hydrothermal method of the present invention has great potential in suppressing icing disasters and other aspects. While in Comparative Examples 1, 2, and 3, the amount of hydrophobic material is less, so the hydrophobic effect is poor.

[0106] Cyclic stability determination test: The cyclic stabilities of Examples 1-5 and Comparative Examples 1-7 were verified through simulation experiments respectively. The specific determination method was as follows: 5 g of each of the composite phase change materials prepared in Examples 1-5 and Comparative Examples 1-7 was taken, and using a circular mold with a diameter of 50 mm, under a pressure of 14 MPa for 3 minutes, they were respectively pressed into thin sheets. The thin sheets were placed in a high and low temperature test chamber and heated from -10°C to 80°C at a rate of 5°C per minute, and then cooled from 80°C to -10°C at a rate of 5°C per minute. The temperature was raised and lowered 1000 times respectively, and the leakage situation of the samples during the cycle was tested. The experimental results are shown in Tables 3 and 4.

[0107] Table 3

[0108]

[0109] Table 4

[0110]

[0111] Thermal stability determination test: The thermal stabilities of Examples 1-5 and Comparative Examples 1-7 were verified through simulation experiments respectively. The specific determination method was as follows: 5 g of each of the composite phase change materials prepared in Examples 1-5 and Comparative Examples 1-7 was taken, and using a circular mold with a diameter of 50 mm, under a pressure of 14 MPa for 3 minutes, they were respectively pressed into thin sheets. The thin sheets were placed in a high temperature environment of 150°C for 6 h, and the stability of the samples under high temperature conditions was tested. The experimental results are shown in Tables 5 and 6.

[0112] Table 5

[0113]

[0114] Table 6

[0115]

[0116] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage material, characterized in that: The raw materials include, by weight: 65-80 parts of phase change material, 10-32 parts of fly ash-based porous material modified by carbon self-growth, 2-5 parts of spectrum adjustment material and 10-15 parts of hydrophobic material; The preparation method of the super-hydrophobic fly ash-based photothermal conversion composite phase-change thermal storage material comprises: weighing raw materials by mass, mixing a carbon self-growth modified fly ash-based porous material, a spectrum adjustment material and a phase change material by a vacuum impregnation method or a normal pressure heating method to obtain a carbon self-growth modified fly ash-based photothermal conversion composite phase-change thermal storage material, and mixing, stirring and drying the carbon self-growth modified fly ash-based photothermal conversion composite phase-change thermal storage material and a hydrophobic material to obtain a super-hydrophobic fly ash-based photothermal conversion composite phase-change thermal storage material; The preparation method of the carbon self-growth modified fly ash-based porous material comprises: adding a calcium-based oxygen-containing compound and a carbon source to a fly ash alkaline leaching solution, mixing to obtain a hydrothermal ligand solution, hydrothermally treating, centrifuging, filtering to obtain a carbon self-growth modified fly ash-based precursor solid product, and carbonizing to obtain a carbon self-growth modified fly ash-based porous material; The mass ratio of the fly ash to the calcium-based oxygen-containing compound is (15:1)-(30:1); The mass ratio of the calcium-based oxygen-containing compound to the carbon source is (1:10)-(1:20).

2. The super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage material according to claim 1, characterized in that: The temperature of the hydrothermal treatment is 150-250° C. and the time is 8-20 hours.

3. The super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage material according to claim 1, characterized in that: The carbonization treatment is: in an inert mixed atmosphere, at 600-800° C., for 10-60 minutes.

4. The super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage material according to claim 1, characterized in that: The preparation method of the fly ash alkali leaching solution is as follows: adding fly ash into a pre-prepared alkali composite solution, mixing and stirring, centrifuging and filtering to obtain a supernatant liquid, which is the fly ash alkali leaching solution.

5. An application of the super-hydrophobic fly ash-based photothermal conversion composite phase change heat storage material according to any one of claims 1 to 4 in preventing icing disasters on power transmission lines.

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