A photothermal conversion enhanced CaCO3 shell phase change microcapsule and a preparation method thereof

Abstract

The application discloses a kind of photo-thermal conversion enhanced CaCO3 shell phase change microcapsules and preparation method thereof.The core material of phase change microcapsule is organic "solid-liquid" phase change material, and the wall material is polydopamine composite CaCO3 material.It is prepared by "one-pot method", and the process is as follows:1) phase change material is emulsified in aqueous phase to form micellar emulsion;2) calcium salt solution and carbonate solution are added to the emulsion to react, to form CaCO3 shell;3) continue to add dopamine monomer solution, and the generated polydopamine adheres to the surface of microcapsule.The phase change microcapsule prepared by the application has high energy storage density and thermal responsiveness, and the introduction of polydopamine significantly improves its thermal cycle stability and photo-thermal conversion effect.The "one-pot method" preparation method provided by the application has simple operation process, easy-to-control reaction conditions and high product synthesis efficiency, which helps to realize large-scale application of organic phase change microcapsule in the field of solar photo-thermal conversion and thermal energy storage.

Description

Technical Field

[0001] This invention belongs to the field of latent heat energy storage technology of phase change, and more specifically, relates to a photothermal conversion enhanced CaCO3 shell phase change microcapsule and its preparation method. Background Technology

[0002] Solar energy, with its wide distribution, abundant absolute reserves, and easy access, has become an ideal renewable energy source with great potential for large-scale development. However, the utilization of solar energy is easily affected by many natural factors such as altitude, climate, and season, resulting in spatiotemporal and spatial discontinuities and intensity fluctuations in energy output, which is seriously mismatched with the energy consumption patterns of human society's production and daily life. Therefore, how to achieve high-efficiency and stable utilization of renewable solar energy remains a key problem that urgently needs to be solved.

[0003] Latent heat storage technology is a widely studied thermal storage technology that uses phase change materials (PCMs) as the heat storage medium. It boasts advantages such as high energy density, high heat absorption and release efficiency, stable reusability, and low system equipment cost. It can effectively alleviate the imbalance and mismatch between energy supply and demand and their distribution, while also significantly improving energy utilization and reducing carbon emissions. As a heat storage carrier, PCMs absorb or release a large amount of latent heat during phase change, and their temperature remains within a relatively constant range with minimal fluctuations. This enables efficient storage and controlled release of thermal energy, and it has been widely applied in fields such as building energy conservation and environmental protection, intelligent temperature-regulating textiles, industrial waste heat recovery, thermal management of electronic devices, and solar thermal systems. Among the many phase change thermal energy storage materials, organic solid-liquid phase change materials have gradually become a research hotspot in the field of latent heat energy storage due to their advantages such as large thermal storage capacity, suitable phase change temperature, small supercooling, almost no phase separation, non-toxicity and low corrosivity, good chemical stability, and low price. These materials mainly include higher aliphatic hydrocarbons (n-hexadecane, n-octadecane, paraffin, etc.), higher fatty alcohols (n-dodecanol, n-hexadecylol, etc.), higher fatty acid esters (stearic acid, palmitic acid, lauric acid, butyl stearate, etc.), and high molecular polymers (polyethylene glycol and its derivatives, etc.). However, these organic phase change materials still generally suffer from problems such as easy leakage during solid-liquid phase transition, poor thermal responsiveness, and significant decay of thermal storage capacity during direct use.

[0004] To further enhance the reliability of organic phase change thermal storage technology, an increasing number of researchers are employing microencapsulation technology. This involves encapsulating organic solid-liquid phase change materials with shapeable, dense materials as wall materials, forming organic phase change microcapsules with a core-shell structure. Microencapsulation effectively reduces the fluidity and leakage / contamination risks of organic phase change materials during the heat absorption process from solid to liquid. It also controls volume changes during the phase change, reduces direct contact with the external environment, and significantly increases the heat transfer surface area, thereby significantly improving the thermal stability and cyclic thermal storage performance of organic phase change materials. Furthermore, various inorganic materials such as SiO2, TiO2, CaCO3, Al(OH)3, and ZnO are frequently used as wall materials for organic phase change microcapsules due to their excellent mechanical strength, high thermal conductivity, good flame retardancy, and stable physicochemical properties. Therefore, the obtained inorganic shell phase change microcapsules possess excellent thermal storage and thermal response performance, enabling rapid and efficient storage and release of latent heat of phase change. Furthermore, their safety and thermal cycling stability are significantly improved, better meeting the requirements of practical life and industrial applications. Compared to other inorganic materials, CaCO3 exhibits superior mechanical strength, thermal conductivity, and thermal stability. More importantly, its preparation involves low raw material costs, simple operation methods, mild reaction conditions, and good environmental friendliness, making it highly suitable as the wall material for organic phase change microcapsules. However, organic phase change core materials and CaCO3 wall materials are typically colorless or white, exhibiting weak light absorption and conversion capabilities, thus failing to effectively absorb and utilize solar energy and convert it into heat energy. This severely restricts the application and development of CaCO3 shell phase change microcapsules in the field of solar thermal storage. Therefore, further enhancing the light absorption efficiency and photothermal conversion capability of organic phase change microcapsules, while achieving high overall thermal storage performance, is essential and of significant research importance. Summary of the Invention

[0005] To improve the practicality of organic solid-liquid phase change materials in the field of solar thermal storage, this invention discloses a photothermal conversion-enhanced CaCO3 shell phase change microcapsule and its preparation method. The organic solid-liquid phase change material is first encapsulated with an inorganic CaCO3 wall material to form a core-shell structure microcapsule. Then, the shell surface is further modified with polydopamine, resulting in an organic phase change microcapsule with polydopamine composite CaCO3 as the wall material. Polydopamine (PDA) is an organic polymer material with photothermal conversion properties, exhibiting excellent absorption across the entire spectrum of solar radiation. Furthermore, it contains abundant catechol and amino groups, which are highly adhesive structural groups, enabling it to be deposited on the surface of almost all solid materials through spontaneous oxidative polymerization under weakly alkaline conditions. Therefore, polydopamine can uniformly adhere to the CaCO3 shell surface of organic phase change microcapsules, endowing them with significant light absorption and photothermal conversion functions, which helps to improve their direct solar energy storage and conversion efficiency. It also further enhances the compactness of the microcapsule shell, effectively ensuring its thermal cycling stability for long-term repeated use. This greatly broadens the application range of organic phase change microcapsules, and is expected to improve energy utilization efficiency and play a greater role in solar energy conversion and storage. The technical solution adopted in this invention is as follows.

[0006] A method for preparing photothermal conversion enhanced CaCO3 shell phase change microcapsules employs a highly operable and efficient "one-pot method," comprising the following steps:

[0007] S1. Organic solid-liquid phase change materials are added to an aqueous solution of anionic surfactants to form a stable and dispersed oil-in-water micelle emulsion under mechanical stirring.

[0008] S2. Adjust the temperature and stirring speed of the emulsion system, and add calcium salt solution and carbonate solution dropwise to the emulsion in sequence. After self-assembly precipitation reaction, CaCO3 shell is formed to obtain microcapsule suspension;

[0009] S3. The hydrochloric acid dopamine solution was adjusted to pH 6.5-8.0 with an alkaline solution and then rapidly transferred to the microcapsule suspension to carry out an oxidative self-polymerization reaction. The generated polydopamine adhered to the surface of the microcapsules. The microcapsules were repeatedly washed with deionized water and petroleum ether to obtain photothermal conversion enhanced CaCO3 shell phase change microcapsules.

[0010] Preferably, in step S1 of the "one-pot method", the organic "solid-liquid" phase change material mainly includes higher aliphatic alkanes and higher aliphatic alcohols with high latent heat of phase change and suitable phase change temperature.

[0011] More preferably, the organic solid-liquid phase change material includes one or more of n-tetradecane, n-hexadecane, n-octadecane, n-eicosane, n-dodecyl alcohol, and n-tetradecyl alcohol.

[0012] Preferably, in step S1 of the "one-pot method", the anionic surfactant has good water solubility, so that the micromicelles of the phase change material formed by emulsification are in a negatively charged state.

[0013] More preferably, the anionic surfactant includes one or more of the following: sodium salt of styrene-maleic anhydride copolymer, sodium dodecyl sulfate, sodium hexadecyl sulfate, sodium dodecylbenzene sulfonate, and sodium dioctyl succinate sulfonate.

[0014] Preferably, in step S1 of the "one-pot method", the mass ratio of the organic "solid-liquid" phase change material to the aqueous solution is controlled within the range of 1.0:(6.0-15) to promote the formation of an oil-in-water micelle emulsion with good stability and fluidity.

[0015] Preferably, in step S1 of the "one-pot method", the mechanical stirring speed is 600-1800 r / min, the constant mixing system temperature is 30-55℃, and the emulsification process lasts for 0.5-2.5 h.

[0016] Preferably, in step S2 of the "one-pot method", the calcium salt solution includes one or more of calcium chloride solution, calcium bromide solution, calcium nitrate solution, calcium acetate solution, calcium dihydrogen phosphate solution, and calcium hydrogen sulfate solution, and its concentration is 0.5-2.5 mol / L.

[0017] Preferably, in step S2 of the "one-pot method", the carbonate solution includes one or more of sodium carbonate solution and potassium carbonate solution, and its concentration is 0.3-1.5 mol / L.

[0018] More preferably, in step S2 of the "one-pot method", the dropping rate of the calcium salt solution is 3-10 s per drop, and the self-assembly process lasts for 3.0-8.0 h; the dropping rate of the carbonate solution is 6-15 s per drop, and the precipitation reaction lasts for 3.0-8.0 h.

[0019] Preferably, in step S2 of the "one-pot method", the mechanical stirring speed of the core material emulsion system needs to be adjusted to 400-800 r / min, while the temperature is maintained in the range of 20-45℃.

[0020] Preferably, in step S3 of the "one-pot method", the hydrochloric acid dopamine solution is acidic, which will dissolve and destroy the CaCO3 shell to a certain extent. The pH needs to be adjusted with an alkaline solution before the microcapsule suspension is added.

[0021] More preferably, the concentration of the dopamine hydrochloride solution is 0.04-0.18 mol / L, and the alkaline solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, tris(hydroxymethyl)aminomethane solution, and triethanolamine solution.

[0022] Preferably, in step S3 of the "one-pot method", the temperature of the microcapsule suspension system needs to be adjusted to 18-30℃, the stirring speed is maintained at 300-600r / min, and the oxidative self-polymerization reaction lasts for 12-36h.

[0023] The photothermal conversion enhanced CaCO3 shell phase change microcapsule prepared by any of the above methods has an organic solid-liquid phase change material as its core material and a polydopamine composite CaCO3 material as its wall material, forming a double-layer synergistic protective structure. The inner shell layer is a CaCO3 encapsulation layer, and the outer shell layer is a polydopamine coating layer. The mass ratio of the core material to the wall material is in the range of (2.0-5.0):1.0.

[0024] The photothermal conversion enhanced CaCO3 shell phase change microcapsules prepared by this invention have high heat storage density and significant photothermal energy conversion characteristics, and can be applied to the fields of solar photothermal conversion and thermal energy storage.

[0025] This invention constructs an organic phase change microcapsule with polydopamine composite CaCO3 as the wall material and provides a one-pot preparation method. The core material of this phase change microcapsule is a high latent heat organic solid-liquid phase change material, while the wall material is a polydopamine composite CaCO3 material with both high thermal conductivity and excellent light absorption. Under sufficient light, the polydopamine coating layer efficiently absorbs and converts solar energy into heat energy. Then, the CaCO3 encapsulation layer quickly transfers the heat energy to the phase change core material. Upon reaching the melting temperature, the organic phase change material undergoes a solid-liquid phase transition, thereby achieving high-efficiency thermal storage of solar energy. When light is insufficient or the temperature decreases, the phase change core material of the microcapsule changes from a liquid to a solid state, and the stored solar energy is rapidly released in the form of latent heat, meeting the energy supply needs of daily production and life. Therefore, CaCO3 shell phase change microcapsules modified with polydopamine can be used as heat storage and heat transfer medium for latent heat functional fluids in solar thermal systems, which helps to improve energy utilization efficiency.

[0026] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0027] This invention employs a highly operable and efficient "one-pot method" to prepare a photothermal conversion-enhanced CaCO3 shell phase change microcapsule, aiming to promote the widespread application of phase change energy storage technology in the field of solar thermal storage. In the synthesis strategy disclosed in this invention, a dopamine hydrochloride monomer solution, after pH adjustment with an alkaline solution, is added to a weakly alkaline CaCO3 shell microcapsule suspension system to continue the oxidative self-polymerization reaction. The resulting highly adhesive polydopamine is uniformly deposited on the surface of the CaCO3 shell of the microcapsule. This invention fully combines the excellent thermal conductivity of inorganic CaCO3 with the full-spectrum photothermal conversion effect of organic polydopamine, obtaining an organic phase change microcapsule with significant photothermal conversion effect and high thermal storage efficiency. Furthermore, under the synergistic protection of a high-mechanical-strength CaCO3 encapsulation layer and a dense polydopamine coating layer, the organic phase change microcapsule prepared by this invention also exhibits excellent thermal stability and thermal cycling life. This photothermal conversion enhanced CaCO3 shell phase change microcapsule is prepared by a "one-pot method" that integrates self-assembly precipitation reaction and oxidative self-polymerization reaction. The operation process is simple, the reaction conditions are easy to control, the product synthesis efficiency is high, and the requirements for equipment are low, making it suitable for large-scale industrial production applications. Attached Figure Description

[0028] Figure 1 The image shows the microstructure of the polydopamine composite CaCO3 shell n-octadecane phase change microcapsules provided in Example 1, as shown in the scanning electron microscope (SEM) image.

[0029] Figure 2 Differential scanning calorimetry (DSC) curves of the polydopamine composite CaCO3 shell n-octadecane phase change microcapsules provided in Example 1 after 200 consecutive thermal cycles.

[0030] Figure 3 The temperature change curve of the polydopamine composite CaCO3 shell n-octadecane phase change microcapsule provided in Example 1 under simulated sunlight irradiation.

[0031] Figure 4 Scanning electron microscope (SEM) images of the microstructure of polydopamine-composite CaCO3 shell n-octadecane phase change microcapsules provided for comparative purposes. Detailed Implementation

[0032] To overcome the key challenges faced by organic phase change materials in the application of solar thermal storage, this invention introduces a photothermal conversion material, polydopamine, onto the shell surface of CaCO3 organic phase change microcapsules using a simple "one-pot" preparation method. This discloses a photothermal conversion-enhanced CaCO3 shell phase change microcapsule and its preparation method. The technical solution and beneficial effects of this invention will be described in detail below with reference to specific embodiments and comparative examples. It should be understood that these described embodiments are only for illustrating the design concept of this invention and are not intended to limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art through simple combinations, modifications, substitutions, improvements, etc., without departing from the spirit and principle of this invention, also fall within the scope defined by the appended claims. Furthermore, unless otherwise specified, the reagents, testing methods, and equipment used in these embodiments and comparative examples are all conventional reagents, testing methods, and equipment in this technical field.

[0033] Example 1

[0034] S1. Weigh 8.4 g of n-octadecane into a 500 mL three-necked flask and heat it to 45 °C in an oil bath. Simultaneously, dissolve 2.4 g of sodium dodecylbenzenesulfonate (SDBS) completely in 80 mL of deionized water, and then add this solution to the molten n-octadecane organic phase. Adjust the mechanical stirring speed to 1000 rpm and continue emulsifying for 1.5 h to form a stable oil-in-water micelle emulsion.

[0035] S2. Reduce the stirring speed of the emulsion system to 600 rpm and the temperature to 35°C. Add CaCl2 solution (3.12 g anhydrous CaCl2 and 30 mL deionized water) at a dropping rate of 6 s, and allow it to stabilize for self-assembly for 6.0 h. Then add Na2CO3 solution (2.97 g anhydrous Na2CO3 and 50 mL deionized water) at a dropping rate of 10 s, and allow it to precipitate at a constant temperature for 6.0 h to obtain a microcapsule suspension.

[0036] S3. Continue to reduce the stirring speed to 400 rpm and the temperature to 20℃. Quickly transfer the hydrochloric acid dopamine solution (1.0 g dopamine hydrochloride and 50 mL deionized water) that has been neutralized to pH 7.0 with sodium hydroxide solution to the microcapsule suspension. After 24 h of oxidative self-polymerization reaction, vacuum filter the mixture and wash it repeatedly with deionized water and petroleum ether to obtain polydopamine composite CaCO3 shell n-octadecane phase change microcapsules.

[0037] The prepared n-octadecane phase change microcapsules were loose, dark brown powders that, under SEM observation, exhibited a regular spherical morphology. Figure 1 As shown, it has a clear core-shell structure and a particle size of about 3 μm. Figure 2DSC results showed that the phase change enthalpy of the microcapsules was 141.5 J / g, and remained almost stable during 200 thermal cycles. The thermal conductivity of the microcapsules, measured by a Hot-Disk analyzer, was 0.4420 W / (m·K). Under simulated sunlight irradiation, the polydopamine-modified phase change microcapsules exhibited a more significant heating rate. Figure 3 As shown, this indicates that its photothermal conversion performance has been greatly improved. It is evident that the n-octadecane phase change microcapsules with polydopamine composite CaCO3 as the wall material still possess high heat storage density and thermal conductivity, while also exhibiting excellent thermal cycling stability, and their photothermal conversion capability has been significantly enhanced.

[0038] Example 2

[0039] S1. Dissolve 2.0 g of sodium dodecyl sulfate (SDS) completely in 80 mL of deionized water, then add it to a 500 mL three-necked flask containing 9.0 g of n-tetradecane. Emulsify vigorously for 1.0 h at a mechanical stirring speed of 800 rpm and an oil bath temperature of 35 °C to obtain a stable oil-in-water micelle emulsion.

[0040] S2. Weigh 4.92g of anhydrous Ca(NO3)2 and completely dissolve it in 25mL of deionized water to prepare a Ca(NO3)2 solution. Then weigh 3.18g of anhydrous Na2CO3 and completely dissolve it in 60mL of deionized water to prepare a Na2CO3 solution. Adjust the stirring speed of the emulsion to 550rpm and the temperature to 30℃. Add the Ca(NO3)2 solution to the emulsion at a dropping interval of 5s, and stir steadily for 4.0h. Then, continue to slowly add the Na2CO3 solution at a dropping interval of 8s, and allow the precipitation reaction to proceed for 6.0h to form a microcapsule suspension.

[0041] S3. Weigh 0.8g of dopamine hydrochloride and dissolve it completely in 60mL of deionized water. Adjust the pH to 7.5 with sodium carbonate solution and then quickly transfer it to the microcapsule suspension. Continue the reaction at a stirring speed of 350rpm and a temperature of 20℃ for 18h. Filter under vacuum and wash three times with deionized water and petroleum ether respectively to obtain polydopamine composite CaCO3 shell n-tetradecane phase change microcapsules.

[0042] DSC analysis showed that the prepared n-tetradecane phase change microcapsules had a phase change enthalpy of 135.8 J / g, with an encapsulation efficiency as high as 60.73%. Furthermore, under the synergistic protection of the CaCO3 encapsulation layer and the polydopamine coating layer, the initial weight loss temperature of the n-tetradecane core material increased by 12 °C. Meanwhile, the thermal conductivity of the phase change microcapsules was measured to be 0.4557 W / (m·K) using a Hot-Disk analyzer. In addition, the phase change microcapsules exhibited broad and strong light absorption characteristics in UV-Vis spectroscopy, and subsequently demonstrated excellent photothermal conversion performance under sunlight irradiation. They can be dispersed in most polar media to form a latent heat functional fluid, making them suitable for application in solar thermal collection systems.

[0043] Example 3

[0044] Weigh 3.0 g of styrene-maleic anhydride copolymer sodium salt and dissolve it in 100 mL of deionized water to prepare an emulsifier solution of suitable concentration. Simultaneously, weigh 6.32 g of anhydrous Ca(CH3COO)2 and completely dissolve it in 40 mL of deionized water to prepare a Ca(CH3COO)2 solution for later use. Then, weigh 4.24 g of anhydrous Na2CO3 and completely dissolve it in 40 mL of deionized water to prepare a Na2CO3 solution for later use.

[0045] S1. Mix 10g of n-dodecyl alcohol and 100mL of emulsifier solution in a 500mL three-necked flask, adjust the mechanical stirring speed to 1500rpm and the temperature to 45℃, and disperse and emulsify for 1.5h to obtain a stable water-in-oil micelle emulsion.

[0046] S2. Under the conditions of stirring speed of 650 rpm and system temperature of 32℃, Ca(CH3COO)2 solution was added to the emulsion at a dropping rate of 5 s, and the self-assembly was stabilized for 4.0 h. Then, Na2CO3 solution was added to the mixture at a dropping rate of 10 s, and the precipitation reaction was carried out for 4.0 h to form a microcapsule suspension.

[0047] S3. Reduce the stirring speed of the suspension to 450 rpm and the temperature to 25℃. Simultaneously, weigh 1.2 g of dopamine hydrochloride and dissolve it in 50 mL of deionized water. After adjusting the pH to 7.0 with tris(hydroxymethyl)aminomethane solution, quickly add the solution to the microcapsule suspension and continue the reaction for 18 h. Vacuum filter the microcapsules and wash them multiple times with deionized water and petroleum ether to obtain polydopamine composite CaCO3 shell n-dodecyl alcohol phase change microcapsules.

[0048] The prepared n-dodecyl alcohol phase change microcapsules also exhibit a core-shell spherical morphology, with particle sizes mainly distributed in the range of 2-6 μm. DSC testing results show that the phase change enthalpy of these microcapsules is 131.6 J / g, and their phase change temperature and enthalpy remained almost unchanged during 200 thermal cycles, maintaining a stable phase change heat storage capacity. Hot-Disk analysis reveals that the thermal conductivity of these microcapsules is 0.4338 W / (m·K), significantly higher than the 0.08-0.30 W / (m·K) of most polymer-shell phase change microcapsules, contributing to rapid thermal response and heat transfer. Furthermore, the surface modification with polydopamine greatly enhances the light absorption effect of the microcapsules, exhibiting high levels of photothermal conversion and storage capacity under continuous illumination.

[0049] Comparative Example

[0050] S1. Mix 10g of n-octadecane and 80mL of octylphenol polyoxyethylene ether-10 (2.0g) solution in a 500mL three-necked flask, heat the oil bath to 45℃, and emulsify for 1.5h with mechanical stirring at 1200rpm to obtain a stable and dispersed oil-in-water micelle emulsion.

[0051] S2. Reduce the stirring speed of the emulsion system to 600 rpm and the temperature to 35°C. Add 40 mL of clear CaCl2 (3.33 g) solution dropwise at 6 s intervals, allowing the micromicelles to self-assemble for 6.0 h. Then, slowly add 60 mL of clear Na2CO3 (3.18 g) solution dropwise at 12 s intervals, and maintain stable stirring for 6.0 h to obtain a microcapsule suspension.

[0052] S3. 50 mL of dopamine hydrochloride (1.0 g) solution that has not been neutralized with alkaline solution was directly transferred to the microcapsule suspension. Oxidative self-polymerization reaction was carried out at a stirring speed of 450 rpm and a constant temperature of 20 °C for 24 h. After vacuum filtration, the polymer was repeatedly washed with deionized water and petroleum ether to obtain polydopamine composite CaCO3 shell n-octadecane phase change microcapsules.

[0053] Similarly, brownish-yellow powdery n-octadecane phase change microcapsules were prepared. Under SEM observation, as shown... Figure 4As shown, its outline reveals a core-shell spherical structure, but severe shell damage and loss of most of the phase change core material are also evident. DSC analysis showed that the phase change enthalpy of this microcapsule was only 56.81 J / g, and TGA results indicated that its initial thermal weight loss behavior was basically similar to that of pure octadecane, reflecting that its thermal stability was not significantly improved. Furthermore, this microcapsule did not exhibit good photothermal storage capacity in solar irradiation tests. This is because the octylphenol polyoxyethylene ether-10 emulsifier used in its preparation is non-ionic, which is unfavorable for Ca... 2+ The CaCO3 molecules self-assembled around the micromicelles, resulting in a significant amount of CaCO3 not participating in the core material encapsulation process. Furthermore, the unneutralized dopamine hydrochloride solution was acidic and dissolved the CaCO3 wall material, leading to thinner and more easily damaged walls in the phase change microcapsules, thus failing to achieve effective encapsulation of the phase change material.

Claims

1. A method for preparing a photothermal conversion enhanced CaCO3 shell layer phase change microcapsule, characterized in that, A "one-pot method" comprising the following steps: S1. Organic "solid-liquid" phase change material is added to the aqueous solution of anionic surfactant, and under the action of mechanical stirring, a stable dispersed oil-in-water microemulsion is formed; the mass ratio of the organic "solid-liquid" phase change material to the aqueous solution is 1.0:(6.0-15), the stirring speed is 600-1800 r / min, the constant temperature is 30-55℃, and the emulsification process lasts for 0.5-2.5 h; S2. The temperature of the emulsion system is adjusted to 20-45℃, the stirring speed is 400-800 r / min, a calcium salt solution is added dropwise into the emulsion at an interval of 3-10 s per drop, and a self-assembly reaction is carried out for 3.0-8.0 h; then a carbonate salt solution is added dropwise at an interval of 6-15 s per drop, and a precipitation reaction is carried out for 3.0-8.0 h to form a CaCO3 shell layer, thereby obtaining a microcapsule suspension; S3. A dopamine hydrochloride solution is adjusted to pH = 6.5-8.0 by a basic solution, and then quickly transferred into the microcapsule suspension; the temperature of the microcapsule suspension system is maintained at 18-30℃, and the stirring speed is 300-600 r / min; an oxidative self-polymerization reaction is carried out for 12-36 h, and the generated polydopamine is adhered to the surface of the microcapsule; the microcapsule is repeatedly washed with deionized water and petroleum ether to obtain a light-heat conversion enhanced CaCO3 shell layer phase change microcapsule.

2. The preparation method of the photothermal conversion enhanced CaC03 shell phase change microcapsules according to claim 1, characterized in that, In step S1 of the "one-pot method", the organic "solid-liquid" phase change material includes one or more of n-tetradecane, n-hexadecane, n-octadecane, n-eicosane, n-dodecanol, and n-tetradecanol.

3. The method of claim 1, wherein the method is characterized by: In step S1 of the "one-pot method", the anionic surfactant includes one or more of sodium salt of styrene-maleic anhydride copolymer, sodium dodecyl sulfate, sodium hexadecyl sulfate, sodium dodecyl benzene sulfonate, and sodium dioctyl sulfosuccinate.

4. The method of claim 1, wherein the method is characterized by: In step S2 of the "one-pot method", the calcium salt solution includes one or more of calcium chloride solution, calcium bromide solution, calcium nitrate solution, calcium acetate solution, calcium dihydrogen phosphate solution, and calcium bisulfate solution; and the carbonate salt solution includes one or more of sodium carbonate solution and potassium carbonate solution.

5. The method of claim 1, wherein the method is characterized by: In step S3 of the "one-pot method", the basic solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, tris-hydroxymethyl aminomethane solution, and triethanolamine solution.

6. The photothermal conversion enhanced CaC03 shell phase change microcapsules prepared by the preparation method of any one of claims 1-5, characterized in that, The light-heat conversion enhanced CaCO3 shell layer phase change microcapsule has an organic "solid-liquid" phase change material as a core material and a polydopamine composite CaCO3 material as a wall material, and the mass ratio of the core material to the wall material is (2.0-5.0):1.

0.

7. The light-heat conversion enhanced CaCO3 shell layer phase change microcapsule of claim 6 can be applied in the field of solar light-heat conversion and heat energy storage.

Images