Bamboo-based photo-thermal super-hydrophobic phase change composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photo-thermal phase-change materials, in particular to a bamboo-based photo-thermal super-hydrophobic phase-change composite material and a preparation method and application thereof. The preparation method comprises the following steps that S1, bamboo wood is pretreated; s2, delignification bamboo wood is prepared; s3, photo-thermal modification: S301, loading of a tannin-iron compound; s302, treatment with a photo-thermal modifier; s4, hydrophobic modification: S401, loading of silver nanoparticles; s402, dipping with a super-hydrophobic modifier; and S5, preparing the bamboo-based photo-thermal super-hydrophobic phase change composite material. According to the bamboo-based photo-thermal super-hydrophobic phase change composite material and the preparation method and application thereof, the problems that in the related technology, leakage is likely to happen in the solid-liquid phase change process of a phase change material, and photo-thermal-heat storage synergy is poor are solved.

Description

Technical Field

[0001] This application relates to the field of photothermal phase change materials technology, and in particular to a bamboo-based photothermal superhydrophobic phase change composite material, its preparation method and application. Background Technology

[0002] Against the backdrop of escalating global energy supply and demand imbalances, phase change materials (PCMs) have become core materials in fields such as solar thermal utilization and building energy conservation due to their ability to absorb / release large amounts of latent heat during phase change. However, PCMs are prone to leakage during solid-liquid phase changes, and traditional encapsulation technologies (such as metal shells and polymer capsules) generally suffer from poor compatibility between the carrier and PCMs, high preparation costs, and complex processes, which severely limit their large-scale application.

[0003] Biomass materials, due to their renewable nature, wide availability, and naturally porous structure, offer a green solution for PCMs encapsulation. Bamboo, in particular, grows rapidly and is abundant; its fibrous microstructure can reduce PCM leakage through physical confinement while simultaneously supporting the loading of functional components. However, current solar-driven energy systems place multifunctional demands on materials, requiring "photothermal conversion, self-cleaning, and long-term stability": efficient photothermal conversion necessitates materials to fully capture solar energy and convert it into heat; superhydrophobic properties are required to suppress dust and moisture adhesion to maintain optical / thermal performance; and stability under extreme environments (such as high temperatures and acid / alkali conditions) determines the material's service life.

[0004] Existing research has significant shortcomings: although single-function optimization of photothermal materials (such as graphene and TiO2) or superhydrophobic surfaces has been achieved, there is a lack of systematic design that organically integrates "photothermal conversion, phase change heat storage, and superhydrophobic stress resistance" into biomass carriers; at the same time, the lack of functional integration design of biomass-based carriers leads to insufficient stability of materials under extreme environments, difficulty in synergistic optimization of photothermal conversion efficiency and phase change enthalpy, and poor thermal conductivity.

[0005] The natural adaptations of desert cacti in nature offer inspiration for solving this problem: the porous structure of their fleshy stems allows for water storage, their epidermal pigments efficiently capture light energy, and their surface micro- and nano-protrusions form a hydrophobic and anti-fouling structure with a waxy layer. This structure-function fit of their natural design aligns perfectly with the functional requirements of bamboo-based PCMs, providing a new direction for the development of biomass-based multifunctional composite phase change materials. Therefore, there is an urgent need to develop a bamboo-based composite phase change material based on biomimetic design to overcome existing technological bottlenecks. Summary of the Invention

[0006] This application provides a bamboo-based photothermal superhydrophobic phase change composite material, its preparation method, and its application, in order to solve the problems of easy leakage and poor photothermal-thermal storage synergy in the solid-liquid phase change process of phase change materials in related technologies.

[0007] In a first aspect, a method for preparing a bamboo-based photothermal superhydrophobic phase change composite material is provided, which includes the following steps: S1. Bamboo pretreatment: Bamboo is processed into 10mm×10mm×10mm samples, repeatedly washed with deionized water to remove surface impurities, and then dried in an oven at 100~105℃ until completely dry to obtain pretreated bamboo. S2. Preparation of delignified bamboo: After the pretreated bamboo is saturated with water, it is transferred to a 5-10 wt% sodium chlorite solution, and the pH of the solution is adjusted to 4.5-4.8 with 2-5 wt% glacial acetic acid. After the system is kept at 75~80℃ for 7.5~8h, it is washed with deionized water and dried in a freeze dryer for 40~50h to obtain delignified bamboo with high porosity. S3, Photothermal Modification: S301, Tannin-Iron Complex Loading: Delignified bamboo was immersed in a tannic acid aqueous solution with a concentration of 10 g / L until the bamboo was saturated, and then freeze-dried for 45-48 hours. Continue immersing in a ferric chloride solution with a concentration of 2 g / L and a pH of 7.5-8 for 5-6 hours at room temperature. Remove the sample, wash it with water, and freeze-dry it for 45-48 hours to obtain delignified bamboo loaded with tannin-iron complex. S302, photothermal modifier treatment: The delignified bamboo material supported by the tannin-iron composite was immersed in a photothermal modifier and kept at a constant temperature of 65-70°C for 2 hours with stirring. Carrageenan was then added, and the reaction was continued for 0.5-1 hours. After being removed, it is rinsed with deionized water and dried under vacuum at 60℃ for 3-4 hours to obtain photothermal modified bamboo. S4, hydrophobic modification: S401, silver nanoparticle loading: The photothermal modified bamboo was immersed in a silver nitrate solution with a concentration of 2 g / L and irradiated under ultraviolet light with a wavelength of 365 nm for 0.5 to 1.5 h. The sample was then taken out and freeze-dried to obtain silver-loaded photothermal modified bamboo. S402, superhydrophobic modifier impregnation: Silver-loaded photothermal modified bamboo was immersed in a superhydrophobic modifier and soaked at a constant temperature of 50°C for 1-2 hours under stirring. After adding thioctic acid, the temperature was raised to 55-60°C and reacted for 1 hour. After removal and drying, hydrophobic-photothermal modified bamboo was obtained. The amount of thioctic acid added was 1-2% of the weight of the silver-loaded photothermal modified bamboo. S5. Preparation of bamboo-based photothermal superhydrophobic phase change composite materials: The hydrophobic-photothermal modified bamboo was placed in molten myristic acid, and after adding a crosslinking agent, it was transferred to a vacuum oven with a vacuum degree of 0.08 MPa and a temperature of 70~75℃ for 5~6 hours, with a balancing operation performed every 30 minutes during the process; the mass ratio of the crosslinking agent to myristic acid was 1:10. After the treatment, the sample was wrapped with filter paper and placed on a heating table at 65~70℃. The filter paper was replaced every 5 minutes until there was no liquid residue on the filter paper, thus obtaining the bamboo-based photothermal superhydrophobic phase change composite material.

[0008] Preferably, in step S1, after processing the bamboo material into a 10mm×10mm×10mm sample and before repeatedly washing it with deionized water, the following steps are also included: The sample was placed in a 5wt% hydroxyethyl cellulose aqueous solution and soaked at a constant temperature of 60℃ for 1.5~2h, and then ultrasonically dispersed for 25~30min.

[0009] Preferably, in step S1, the bamboo material is selected from either moso bamboo or dwarf bamboo.

[0010] Preferably, in step S302, the preparation method of the photothermal modifier includes the following steps: Polypyrrole and sodium alginate were dispersed in deionized water at a mass ratio of 5:2, wherein the mass ratio of polypyrrole to deionized water was 1:80.

[0011] Preferably, in step S302, the amount of carrageenan added is 0.5% of the weight of the delignified bamboo material loaded with tannin-iron composite.

[0012] Preferably, in step S402, the method for preparing the superhydrophobic modifier includes the following steps: The constructing material and octadecylamine were dispersed in an aqueous ethanol solution and ultrasonically dispersed for 20-25 min to obtain a superhydrophobic modifier. The mass ratio of the constructing material to octadecylamine is (4~5):3, the mass-volume ratio of octadecylamine to ethanol aqueous solution is 3g:100mL, and the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 3:(1.5~2).

[0013] Preferably, in the superhydrophobic modifier, the building material is selected from a composition of polyimide and vermiculite, and the mass ratio of polyimide to vermiculite is 5:2; Alternatively, the building material can be selected from lanolin.

[0014] Preferably, in step S5, the temperature of the molten myristic acid is 52~55°C; The crosslinking agent comprises microcrystalline cellulose and gellan gum in a mass ratio of 3:(1~2):40.

[0015] Secondly, a bamboo-based photothermal superhydrophobic phase change composite material is provided, which is prepared by any of the above-described methods for preparing bamboo-based photothermal superhydrophobic phase change composite materials.

[0016] Thirdly, an application of bamboo-based photothermal superhydrophobic phase change composite material in photothermal-thermal storage is provided.

[0017] The beneficial effects of the technical solution provided in this application include: This application provides a bamboo-based photothermal superhydrophobic phase change composite material, its preparation method, and its application. The delignified porous bamboo forms a biomimetic cactus skeleton. A tannin-iron composite and polypyrrole synergistically form a dense pore wall support layer and construct a basic photothermal absorption layer (tannin-iron captures visible light, and polypyrrole enhances near-infrared light absorption). Silver nanoparticles not only enhance light absorption secondaryally through localized surface plasmon resonance but also form nano-protrusions that synergistically with lanolin and octadecylamine to construct a low surface energy superhydrophobic layer, meeting superhydrophobic standards. Combined with a three-dimensional network formed in the phase change material by a crosslinking agent composed of microcrystalline cellulose and gellan gum, it synergistically encapsulates myristic acid with the porous bamboo. Furthermore, the core raw material of this application is renewable bamboo. While optimizing the material's photothermal conversion efficiency, phase change enthalpy retention rate, and thermal conductivity, it achieves synergistic enhancement of photothermal and thermal storage, meeting superhydrophobic standards and exhibiting excellent leak-proof performance. It can be widely applied in the thermal storage stage of solar thermal utilization. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating the preparation method of the bamboo-based photothermal superhydrophobic phase change composite material provided in this application; Figure 2 Electron micrograph of the bamboo-based photothermal superhydrophobic phase change composite material prepared in Example 1 of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] See Figures 1-2 As shown, this application provides a bamboo-based photothermal superhydrophobic phase change composite material, its preparation method, and its application.

[0022] It should be noted that the water retention treatment involves recording the weight of the sample, placing the specimen in a container filled with water (or the corresponding solution), ensuring the water (or the corresponding solution) completely covers the specimen, boiling the water (or the corresponding solution), and maintaining it at a boil for 5 hours. During the boiling process, the water level should be observed regularly, and any water lost due to evaporation should be replenished promptly to ensure the specimen is always completely submerged in the water (or the corresponding solution). After boiling, stop heating and allow the container and specimen to cool naturally to room temperature in the water (or corresponding solution). After removing the specimen, wipe the surface moisture with a damp towel and immediately measure its weight to check if it has reached the water saturation requirement (usually, a weight difference of no more than 0.1% between two weighings is considered to be water saturation; if not, water saturation treatment needs to be continued).

[0023] In addition, unless otherwise specified in this application, the operation of impregnation or immersion refers to the complete immersion of a solid in a liquid.

[0024] Example 1 The method for preparing bamboo-based photothermal superhydrophobic phase change composite material provided in this embodiment includes the following steps: S1. Bamboo pretreatment: The bamboo was processed into small samples of 10mm×10mm×10mm. The samples were placed in a 5wt% hydroxyethyl cellulose aqueous solution and soaked at a constant temperature of 60℃ for 1.5h, and then ultrasonically dispersed for 25min. The surface impurities are removed by repeatedly washing with deionized water, and then placed in an oven at 103°C to dry completely ("dry" means that the material is in a state that is free of moisture inside and outside during the drying process, which will not be described in detail in the following examples) to obtain pretreated bamboo material; S2. Preparation of delignified bamboo: After saturating 100g of pretreated bamboo with water, transfer it to a 10wt% sodium chlorite solution (complete immersion is sufficient), and adjust the pH of the solution to 4.6 with 5wt% glacial acetic acid. The system was subjected to constant temperature treatment at 80℃ for 8 hours (during which sodium chlorite produces chlorine dioxide in an acidic environment, which oxidizes and breaks the lignin structure). After cleaning with deionized water to remove residual agents, it was placed in a freeze dryer and dried for 48 hours to obtain delignified bamboo with high porosity, which simulates the porous water storage structure of the fleshy stem of a cactus. S3, Photothermal Modification: S301, Tannin-Iron Complex Loading: Delignified bamboo was immersed in a tannic acid aqueous solution with a concentration of 10 g / L (the solution should cover the solid) until the bamboo was saturated with water, and then freeze-dried for 48 hours. The sample was further immersed in a ferric chloride solution with a concentration of 2 g / L and pH=8 for 6 hours at room temperature. The sample was then removed, washed with water, and freeze-dried for 48 hours to obtain delignified bamboo loaded with tannin-iron complex.

[0025] The ortho-phenolic hydroxyl group (lone pair electron donor) in the tannic acid molecule reacts with Fe 3+ (empty valence electron orbitals) undergo complexation reactions to form stable five- or six-membered chelate rings; delignified bamboo loaded with tannin-iron complexes achieves broad-spectrum light absorption based on ligand-metal charge transfer, simulating the light-harvesting characteristics of cactus pigments.

[0026] S302, photothermal modifier treatment: Take 90g of delignified bamboo loaded with tannin-iron composite and immerse it in photothermal modifier. Keep the temperature at 65℃ for 2h under stirring conditions (300r / min). Add 0.45g of carrageenan and continue the reaction for 1h. After being removed, the bamboo was rinsed with deionized water and then vacuum dried at 60°C for 3 hours to obtain photothermal modified bamboo. The photothermal modifier is a mixture of 1.5g polypyrrole, 0.6g sodium alginate, and 120g deionized water.

[0027] S4, hydrophobic modification: S401, silver nanoparticle loading: Photothermally modified bamboo was immersed in a 2 g / L silver nitrate solution and irradiated under 365 nm ultraviolet light for 1 hour. The sample was then removed and freeze-dried to obtain silver-loaded photothermally modified bamboo. The phenolic hydroxyl oxygen atom in tannic acid served as an electron donor, transferring Ag... + It is reduced to elemental silver, forming uniformly dispersed AgNPs (based on surface plasmon resonance-enhanced photothermal effect).

[0028] S402, superhydrophobic modifier impregnation: 85g of silver-loaded photothermal modified bamboo was immersed in a superhydrophobic modifier and soaked at 50℃ for 1.5h under stirring at 400r / min. After adding 1g of thioctic acid, the temperature was raised to 60℃ and reacted for 1h. After drying, hydrophobic-photothermal modified bamboo was obtained. The superhydrophobic modifier is a mixture of 4g lanolin, 3g octadecylamine, and 100mL ethanol solution, wherein the ethanol solution is a mixture of anhydrous ethanol and deionized water in a volume ratio of 3:2. The amino group of octadecylamine undergoes a Schiff base reaction with the carbonyl group of oxidized tannic acid (forming a C=N bond), and simultaneously undergoes a Michael addition reaction, which firmly grafts octadecylamine onto the material surface; the long-chain alkyl group of octadecylamine reduces the surface energy, and combined with the micro-nano rough structure, it simulates the waxy hydrophobic layer of cactus epidermis.

[0029] S5. Preparation of bamboo-based photothermal superhydrophobic phase change composite materials: 80g of hydrophobic-photothermal modified bamboo was placed in myristic acid (MA) in a molten state at 54℃. The MA was enough to cover the hydrophobic-photothermal modified bamboo. In this example, 70g of MA was used. After mixing with 7g of crosslinking agent, the mixture was transferred to a vacuum oven with a vacuum degree of 0.08MPa and a temperature of 70℃ for 5h. During this period, a balancing operation was performed every 30min. After treatment, the sample was wrapped in filter paper and placed on a heating platform at 70°C. The filter paper was replaced every 5 minutes until no liquid residue remained on the filter paper, thus obtaining a bamboo-based photothermal superhydrophobic phase change composite material. The phase change material is physically encapsulated through capillary forces and surface tension, achieving thermal energy storage.

[0030] The crosslinking agent is a mixture of 6g microcrystalline cellulose and 2g gellan gum; the crosslinking agent is added in the order of microcrystalline cellulose, gellan gum, and the mixture is stirred immediately after adding microcrystalline cellulose, and then gellan gum is added.

[0031] Example 2 The difference between this embodiment and Embodiment 1 is that step S1 includes the following steps: S1. Bamboo pretreatment: The bamboo was processed into small samples of 10mm×10mm×10mm, repeatedly washed with deionized water to remove surface impurities, and then dried in an oven at 103℃ until completely dry to obtain pretreated bamboo.

[0032] Furthermore, the superhydrophobic modifier in S402 is a mixture of 2.86g polyimide, 1.14g vermiculite, 3g octadecylamine, and 100mL ethanol solution, wherein the ethanol solution is a mixture of anhydrous ethanol and deionized water in a volume ratio of 2:1.

[0033] Example 3 The method for preparing bamboo-based photothermal superhydrophobic phase change composite material provided in this embodiment includes the following steps: S1. Bamboo pretreatment: The bamboo was processed into small samples of 10mm×10mm×10mm. The samples were placed in a 5wt% hydroxyethyl cellulose aqueous solution, soaked at 60℃ for 2 hours, and then ultrasonically dispersed for 30 minutes. The surface impurities are removed by repeatedly washing with deionized water, and then dried in a 100℃ oven until completely dry to obtain pretreated bamboo. S2. Preparation of delignified bamboo: After saturating 100g of pretreated bamboo with water, transfer it to a 5wt% sodium chlorite solution (complete immersion is sufficient), and adjust the pH of the solution to 4.8 with 2wt% glacial acetic acid. After the system was kept at 75℃ for 7.5 hours, it was washed with deionized water to remove residual agents and then dried in a freeze dryer for 40 hours to obtain delignified bamboo with high porosity, which simulates the porous water storage structure of the fleshy stem of a cactus. S3, Photothermal Modification: S301, Tannin-Iron Complex Loading: Delignified bamboo was immersed in a tannic acid aqueous solution with a concentration of 10 g / L (the solution should cover the solid) until the bamboo was saturated with water, and then freeze-dried for 45 hours. The sample was further immersed in a ferric chloride solution with a concentration of 2 g / L and pH=7.5 for 5 hours at room temperature. The sample was then removed, washed with water, and freeze-dried for 45 hours to obtain delignified bamboo loaded with tannin-iron complex. S302, photothermal modifier treatment: Take 90g of delignified bamboo loaded with tannin-iron composite and immerse it in photothermal modifier. Keep the temperature at 70℃ for 2h under stirring conditions (300r / min). Add 0.45g of carrageenan and continue the reaction for 1h. After being removed, the bamboo was rinsed with deionized water and then vacuum dried at 60°C for 3 hours to obtain photothermal modified bamboo. The photothermal modifier is a mixture of 1.5g polypyrrole, 0.6g sodium alginate, and 120g deionized water.

[0034] S4, hydrophobic modification: S401, silver nanoparticle loading: Photothermal modified bamboo was immersed in a silver nitrate solution with a concentration of 2 g / L and irradiated under ultraviolet light with a wavelength of 365 nm for 0.5 h. The sample was then taken out and freeze-dried to obtain silver-loaded photothermal modified bamboo. S402, superhydrophobic modifier impregnation: 85g of silver-loaded photothermal modified bamboo was immersed in a superhydrophobic modifier and soaked at 50℃ for 1h under stirring at 400r / min. After adding 0.85g of thioctic acid, the temperature was raised to 55℃ and reacted for 1h. After drying, hydrophobic-photothermal modified bamboo was obtained. The superhydrophobic modifier is a mixture of 5g lanolin, 3g octadecylamine and 100mL ethanol solution, wherein the ethanol solution is a mixture of anhydrous ethanol and deionized water in a volume ratio of 3:2.

[0035] S5. Preparation of bamboo-based photothermal superhydrophobic phase change composite materials: 80g of hydrophobic-photothermal modified bamboo was placed in myristic acid (MA) in molten state at 52℃, and the MA was enough to cover the hydrophobic-photothermal modified bamboo. In this example, 70g of MA was used. After adding 7g of crosslinking agent and mixing, the mixture was transferred to a vacuum oven with a vacuum degree of 0.08MPa and a temperature of 75℃ for 5h treatment. During this period, a balancing operation was performed every 30min. After treatment, the sample was wrapped in filter paper and placed on a heating platform at 70°C. The filter paper was replaced every 5 minutes until no liquid residue remained on the filter paper, thus obtaining a bamboo-based photothermal superhydrophobic phase change composite material. The phase change material is physically encapsulated through capillary forces and surface tension, achieving thermal energy storage.

[0036] The crosslinking agent is a mixture of 6g microcrystalline cellulose and 4g gellan gum; the crosslinking agent is added in the order of microcrystalline cellulose, gellan gum, and the mixture is stirred immediately after adding microcrystalline cellulose, and then gellan gum is added.

[0037] Example 4 The method for preparing bamboo-based photothermal superhydrophobic phase change composite material provided in this embodiment includes the following steps: S1. Bamboo pretreatment: The bamboo was processed into small samples of 10mm×10mm×10mm. The samples were placed in a 5wt% hydroxyethyl cellulose aqueous solution and soaked at a constant temperature of 60℃ for 1.5h, and then ultrasonically dispersed for 30min. The surface impurities are removed by repeatedly washing with deionized water, and the bamboo is dried in an oven at 105℃ until completely dry to obtain pretreated bamboo. S2. Preparation of delignified bamboo: After saturating 100g of pretreated bamboo with water, transfer it to an 8wt% sodium chlorite solution (complete immersion is sufficient), and adjust the pH of the solution to 4.5 with 5wt% glacial acetic acid. After the system was kept at 80℃ for 7.5 hours, it was washed with deionized water to remove residual agents and then dried in a freeze dryer for 50 hours to obtain delignified bamboo with high porosity, which simulates the porous water storage structure of the fleshy stem of a cactus. S3, Photothermal Modification: S301, Tannin-Iron Complex Loading: Delignified bamboo was immersed in a tannic acid aqueous solution with a concentration of 10 g / L (the solution should cover the solid) until the bamboo was saturated with water, and then freeze-dried for 46 hours. The sample was further immersed in a ferric chloride solution with a concentration of 2 g / L and pH=8 for 6 hours at room temperature. The sample was then removed, washed with water, and freeze-dried for 45 hours to obtain delignified bamboo loaded with tannin-iron complex. S302, photothermal modifier treatment: Take 90g of delignified bamboo loaded with tannin-iron composite and immerse it in photothermal modifier. Keep the temperature at 65℃ for 2h under stirring conditions (300r / min). Add 0.45g of carrageenan and continue the reaction for 0.5h. After being removed, the bamboo was rinsed with deionized water and then vacuum dried at 60°C for 3 hours to obtain photothermal modified bamboo. The photothermal modifier is a mixture of 1.5g polypyrrole, 0.6g sodium alginate, and 120g deionized water.

[0038] S4, hydrophobic modification: S401, silver nanoparticle loading: Photothermal modified bamboo was immersed in a silver nitrate solution with a concentration of 2 g / L and irradiated under ultraviolet light with a wavelength of 365 nm for 1.5 h. The sample was then taken out and freeze-dried to obtain silver-loaded photothermal modified bamboo. S402, superhydrophobic modifier impregnation: 85g of silver-loaded photothermal modified bamboo was immersed in a superhydrophobic modifier and soaked at 50℃ for 2 hours under stirring at 400r / min. After adding 1.7g of thioctic acid, the temperature was raised to 60℃ and reacted for 1 hour. After drying, hydrophobic-photothermal modified bamboo was obtained. The superhydrophobic modifier is a mixture of 3.57g polyimide, 1.43g vermiculite, 3g octadecylamine and 100mL ethanol solution, wherein the ethanol solution is a mixture of anhydrous ethanol and deionized water in a volume ratio of 2:1.

[0039] S5. Preparation of bamboo-based photothermal superhydrophobic phase change composite materials: 80g of hydrophobic-photothermal modified bamboo was placed in myristic acid (MA) in a molten state at 55℃. The MA was enough to cover the hydrophobic-photothermal modified bamboo. In this example, 70g of MA was used. After mixing with 7g of crosslinking agent, the mixture was transferred to a vacuum oven with a vacuum degree of 0.08MPa and a temperature of 70℃ for 5h. During this period, a balancing operation was performed every 30min. After treatment, the sample was wrapped in filter paper and placed on a heating platform at 65°C. The filter paper was replaced every 5 minutes until no liquid residue remained on the filter paper, thus obtaining a bamboo-based photothermal superhydrophobic phase change composite material. The phase change material is physically encapsulated through capillary forces and surface tension, achieving thermal energy storage.

[0040] The crosslinking agent is a mixture of 6g microcrystalline cellulose and 2g gellan gum; the crosslinking agent is added in the order of microcrystalline cellulose, gellan gum, and the mixture is stirred immediately after adding microcrystalline cellulose, and then gellan gum is added.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that only the S301 process is performed in step S3, and no crosslinking agent is added in step S5.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that only the S302 process is performed in step S3, and no crosslinking agent is added in step S5.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that step S4 only performs the S402 process.

[0044] Comparative Example 4 The difference between this comparative example and Example 1 is that step S3 only performs the processing of S301, and step S4 only performs the processing of S402.

[0045] Comparative Example 5 The difference between this comparative example and Example 1 is that step S3 only performs the processing of S302, and step S4 only performs the processing of S401.

[0046] The performance of the bamboo-based photothermal superhydrophobic phase change composite materials (hereinafter referred to as "composite materials") prepared in the examples and comparative examples was tested.

[0047] Leakage prevention performance test: Take 10g of the composite material to be tested and place it in a 70℃ constant temperature oven. Cover the surface with qualitative filter paper. After keeping it at this temperature for 3h and 5h, take it out and weigh the weight gain of the filter paper. Calculate the leakage rate. Table 1. High-temperature leakage rate of composite materials in the examples and comparative examples. It should be noted that "no leakage" in Table 1 means a leakage rate of ≤0.1%.

[0048] Example 1 exhibits the best leak-proof performance, with almost no leakage after 3 hours at 70°C, demonstrating strong encapsulation stability. The hydroxyethyl cellulose pretreatment optimizes the pore structure of bamboo, and the tannin-iron complex and polypyrrole synergistically construct a dense pore wall support layer. Furthermore, the crosslinking agents (microcrystalline cellulose and gellan gum) form a three-dimensional network, achieving dual locking of myristic acid through "physical encapsulation + chemical crosslinking," significantly reducing the leakage rate.

[0049] Compared to Example 1, Example 2 did not involve hydroxyethyl cellulose pretreatment, resulting in agglomeration of bamboo pores. The superhydrophobic modifier was a mixture of polyimide and vermiculite, which had weaker interfacial compatibility with bamboo than lanolin, and the leakage rate was slightly higher than in Example 1.

[0050] The comparative sample lacked photothermal modification / silver nanoparticle loading / crosslinking agent, thus failing to form a complete encapsulation system. As a result, a large amount of phase change material was lost during cycling, and the high-temperature leakage rate increased significantly.

[0051] Photothermal-storage synergistic performance test: Photothermal conversion efficiency of the composite material under test (simulated light intensity of xenon lamp 1000 W / m²) 2 The surface temperature of the sample was recorded over time using an infrared thermal imager. The photothermal conversion efficiency at thermal equilibrium and the phase transition enthalpy (heating rate 10℃ / min, 20~80℃) were calculated and tested. The results are shown in Table 2.

[0052] Table 2. Photothermal conversion efficiency and phase transition enthalpy of the composite materials in the examples and comparative examples. Example 1 shows the highest photothermal conversion efficiency. The core of this is the formation of a multi-level light absorption structure by tannin-iron complex + polypyrrole + silver nanoparticles: tannin-iron complex absorbs visible light, polypyrrole absorbs near-infrared light, and silver nanoparticles generate a localized surface plasmon resonance effect, which synergistically enhances the light-harvesting ability; at the same time, hydroxyethyl cellulose pretreatment makes the bamboo pores more uniform, the photothermal layer load is more dense, and heat loss is reduced.

[0053] In Example 2, the superhydrophobic layer was made of polyimide-vermiculite, with a slightly higher light reflectivity than the lanolin layer, resulting in a lower photothermal efficiency than in Example 1. In Example 3, the irradiation time of the silver nanoparticles was shortened, and the particle size distribution was uneven, leading to a slight decrease in photothermal efficiency, but still higher than in Example 2. Comparative Examples 1 and 4 lacked polypyrrole photothermal modification and relied solely on the tannin-iron composite to absorb light energy, resulting in a significant decrease in efficiency. Comparative Examples 3 and 4 also had low efficiency due to the lack of silver nanoparticle loading and the absence of enhanced plasmon resonance effect. In Comparative Example 5, the lack of tannin-iron composite loading weakened the light-harvesting performance and reduced the photothermal conversion efficiency.

[0054] As can be seen, the initial phase change enthalpy values ​​of all groups are relatively similar, indicating that the phase change material loading is similar; the difference in enthalpy values ​​after cycling is due to the packaging stability, which is consistent with the leak prevention performance results.

[0055] Hydrophobicity test: A contact angle meter was used to drop 5 μL of deionized water onto the surface of the composite material and measure the contact angle at five different locations. The average value was then taken. The results are shown in Table 3.

[0056] Table 3 Surface contact angles of composite materials in the examples and comparative examples Thermal conductivity tests were also conducted, and the thermal conductivity coefficients are shown in Table 4.

[0057] Table 4 Thermal conductivity of composite materials in the examples and comparative examples Example 1 exhibits superior hydrophobicity because silver nanoparticles, lanolin, and octadecylamine synergistically construct a cactus micro-nano rough structure: silver nanoparticles form nano-protrusions, while lanolin and octadecylamine provide low surface energy, thereby increasing the surface contact angle; in Example 2, although polyimide-vermiculite can construct a rough structure, its low surface energy characteristics are weaker than those of lanolin, resulting in a slightly lower surface contact angle.

[0058] See Figure 2 As shown, it is an electron microscope image of the composite material prepared in Example 1. Its surface has a certain roughness. Combined with lanolin and octadecylamine, it provides a structural basis for constructing a low surface energy superhydrophobic layer. At the same time, the larger surface area formed by the rough surface structure also provides a sufficient light absorption area for excellent photothermal conversion performance.

[0059] Example 1 has the highest thermal conductivity because the silver nanoparticles are high thermal conductivity fillers, which are uniformly dispersed in the pores of bamboo to form thermal conduction pathways and accelerate the transfer of heat from the photothermal layer to the phase change material. At the same time, the synergistic effect of the tannin-iron composite and polypyrrole optimizes the interfacial heat conduction efficiency and improves the overall thermal conductivity.

[0060] Furthermore, the composite material prepared in Example 1 was further tested and found to be stable in a strong acid / base environment with a pH of 2-12, with a removal rate of >95% for simulated pollutants, and able to maintain long-term optical / thermal properties.

[0061] In practical applications, this composite material can capture and convert solar energy, achieving efficient heat storage through the solid-liquid phase change of the internal phase change material. When heat is needed, the phase change material undergoes a reverse phase change to release heat, meeting the needs of scenarios such as heating, hot water supply, and industrial waste heat recovery. Its superhydrophobic self-cleaning properties can prevent outdoor dust and rainwater from affecting light absorption efficiency, and the green and renewable properties of the bamboo-based carrier also align with the low-carbon and environmentally friendly development trend, providing a new solution for the low-cost and high-stability operation of solar thermal energy storage systems.

[0062] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a bamboo-based photothermal superhydrophobic phase change composite material, characterized in that, It comprises the following steps: S1, bamboo pretreatment: The bamboo is processed into 10mmx10mmx10mm samples, washed repeatedly with deionized water to remove surface impurities, and dried in an oven at 100-105℃ until dry, to obtain pretreated bamboo; S2, preparation of delignified bamboo: After the pretreated bamboo is saturated with water, it is transferred to a 5-10wt% sodium chlorite solution, and the solution pH is adjusted to 4.5-4.8 with 2-5wt% glacial acetic acid; After the system is treated at a constant temperature of 75-80℃ for 7.5-8h, it is washed with deionized water and dried in a freeze dryer for 40-50h to obtain delignified bamboo with high porosity; S3, photo-thermal modification: S301, tannin-iron complex loading: The delignified bamboo is immersed in a 10g / L tannic acid aqueous solution until the bamboo is saturated with water, and then freeze-dried for 45-48h; The sample is then immersed in a 2g / L ferric chloride solution with pH=7.5-8, and soaked at room temperature for 5-6h, then washed with water and freeze-dried for 45-48h to obtain delignified bamboo loaded with tannin-iron complex; S302, photo-thermal modifier treatment: The delignified bamboo loaded with tannin-iron complex is immersed in a photo-thermal modifier, and stirred at a constant temperature of 65-70℃ for 2h, then carrageenan is added and the reaction is continued for 0.5-1h; After removal, the sample is washed with deionized water and vacuum dried at 60℃ for 3-4h to obtain photo-thermal modified bamboo; S4, hydrophobic modification: S401, silver nanoparticle loading: The photo-thermal modified bamboo is immersed in a 2g / L silver nitrate solution, and irradiated under ultraviolet light with a wavelength of 365nm for 0.5-1.5h, then removed and freeze-dried to obtain silver-loaded photo-thermal modified bamboo; S402, superhydrophobic modifier impregnation: The silver-loaded photo-thermal modified bamboo is immersed in a superhydrophobic modifier, and soaked at a constant temperature of 50℃ for 1-2h under stirring, then heated to 55-60℃ after adding lipoic acid and reacted for 1h, then removed and dried to obtain hydrophobic-photo-thermal modified bamboo; The amount of lipoic acid added is 1-2% of the mass of the silver-loaded photo-thermal modified bamboo; S5, preparation of bamboo-based photo-thermal superhydrophobic phase change composite material: The hydrophobic-photo-thermal modified bamboo is placed in a molten myristic acid, and a crosslinking agent is added and transferred to a vacuum oven with a vacuum degree of 0.08MPa and a temperature of 70-75℃ for 5-6h, with a balance operation every 30min; The mass ratio of the crosslinking agent to myristic acid is 1:10; After the treatment is completed, the sample is wrapped with filter paper and placed on a heating table at 65-70℃, and the filter paper is replaced every 5min until no liquid remains on the filter paper, to obtain a bamboo-based photo-thermal superhydrophobic phase change composite material.

2. The preparation method of the bamboo-based photo-thermal superhydrophobic phase change composite material according to claim 1, characterized in that: In S1, after the bamboo is processed into 10mmx10mmx10mm samples and before it is washed repeatedly with deionized water, the following steps are included: Put the small sample in 5wt% hydroxyethyl cellulose aqueous solution, constant temperature soak at 60℃ for 1.5~2h, and then ultrasonic dispersion for 25~30min. 3.The preparation method of the bamboo-based photothermal super-hydrophobic phase change composite material according to claim 1, characterized in that: In S1, the bamboo material is selected from one of Phyllostachys pubescens and Phyllostachys edulis. 4.The preparation method of the bamboo-based photothermal super-hydrophobic phase change composite material according to claim 1, characterized in that: In S302, the preparation method of the photothermal modifier comprises the following steps: Disperse polypyrrole and sodium alginate in deionized water according to the mass ratio of 5:2, and the mass ratio of polypyrrole to deionized water is 1:

80. 5.The preparation method of the bamboo-based photothermal super-hydrophobic phase change composite material according to claim 1, characterized in that: In S302, the amount of carrageenan added is 0.5% of the mass of tannin-iron compound loaded delignified bamboo material. 6.The preparation method of the bamboo-based photothermal super-hydrophobic phase change composite material according to claim 1, characterized in that: In S402, the preparation method of the super-hydrophobic modifier comprises the following steps: Disperse the construction material and octadecylamine in an ethanol aqueous solution, and ultrasonic dispersion for 20~25min to obtain a super-hydrophobic modifier; The mass ratio of the construction material to octadecylamine is (4~5):3, the mass-volume ratio of octadecylamine to the ethanol aqueous solution is 3g:100mL, and the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 3:(1.5~2). 7.The preparation method of the bamboo-based photothermal super-hydrophobic phase change composite material according to claim 1, characterized in that: In the super-hydrophobic modifier, the construction material is selected from a combination of polyimide and vermiculite, and the mass ratio of polyimide to vermiculite is 5:2; Alternatively, the construction material is selected from lanolin. 8.The preparation method of the bamboo-based photothermal super-hydrophobic phase change composite material according to claim 1, characterized in that: In S5, the temperature of the myristic acid in the molten state is 52~55℃; The cross-linking agent comprises microcrystalline cellulose and gellan gum with a mass ratio of 3:(1~2):

40.

9. A bamboo-based photo-thermal super-hydrophobic phase change composite material, characterized in that, It is prepared by the preparation method of the bamboo-based photothermal super-hydrophobic phase change composite material according to any one of claims 1~8. 10.The application of the bamboo-based photothermal super-hydrophobic phase change composite material according to claim 9 in photothermal-heat storage.

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