A hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material, a preparation method and application thereof

Abstract

The application relates to the technical field of phase change heat storage materials, in particular to a hydrothermal modification wood-based photothermal super-hydrophobic composite phase change heat storage material and a preparation method and application thereof, and the preparation method comprises the following steps: S1, substrate pretreatment; S2, porous wood base preparation; S3, photothermal modification: S301, the porous wood substrate is immersed in a 10g / L tannic acid aqueous solution until saturated with water, and after drying, the wood substrate is continuously immersed in a 2g / L ferric sulfate solution, and stirring is performed to fully mix; S302, the wood substrate is continuously immersed in a photothermal modifier, and vacuum impregnation is performed, the wood substrate is taken out and dried, and the impregnation and drying operation is repeated twice to obtain a photothermal modified substrate; S4, thermal conductivity modification; S5, hydrophobic modification; and S6, composite phase change heat storage material preparation. The application provides a hydrothermal modification wood-based photothermal super-hydrophobic composite phase change heat storage material and a preparation method and application thereof, so as to solve the problems of easy leakage of phase change materials, poor thermal conductivity and low packaging efficiency of traditional phase change heat storage materials in the prior art.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of phase change heat storage materials, in particular to a hydrothermal modification wood-based light-heat super-hydrophobic composite phase change heat storage material and a preparation method and application thereof. BACKGROUND

[0002] Phase change materials (PCMs) have become the core energy storage materials in the fields of solar energy utilization and building energy saving due to the characteristics of high efficient latent heat absorption and release in the phase change process. However, the solid-liquid phase change materials have inherent defects of easy leakage and poor thermal conductivity, and the traditional phase change materials can only passively absorb heat energy, which limits their practical application.

[0003] The porous carrier compounding method is the mainstream solution to the leakage of phase change materials. Wood, as a natural renewable biomass material, provides a green carrier for phase change material encapsulation due to its three-dimensional porous structure. However, the existing wood encapsulation technology has obvious shortcomings: first, the natural pore structure of wood is limited, the encapsulation efficiency of phase change materials is low, and the traditional delignification process needs to use chemical reagents, which pollutes the environment and has high cost; second, the wood composite material has single function, and it is difficult to simultaneously realize active heat absorption, efficient heat conduction and surface stain resistance; third, the existing light-heat material production process is complex and toxic, and the heat conduction enhancing filler has poor compatibility with wood, which cannot realize multifunctional synergy. SUMMARY

[0004] The application provides a hydrothermal modification wood-based light-heat super-hydrophobic composite phase change heat storage material and a preparation method and application thereof, so as to solve the problems of easy leakage of phase change materials, poor thermal conductivity and low encapsulation efficiency of traditional phase change heat storage materials in the related art.

[0005] In a first aspect, a preparation method of a hydrothermal modification wood-based light-heat super-hydrophobic composite phase change heat storage material is provided, which comprises the following steps:

[0006] S1, substrate pretreatment:

[0007] The wood is processed into a small sample with a size of 20mmx20mmx6mm, the surface impurities are washed with deionized water, and the pretreated substrate is obtained by drying the wood in a drying box to a constant weight;

[0008] S2, porous wood-based body preparation:

[0009] After the pretreated substrate is immersed in a hydrothermal reaction agent, it is placed in a hydrothermal reaction kettle, the treatment temperature is set to 135-145℃, and the constant temperature treatment is performed for 3-4h. After washing and drying, the porous wood-based substrate is obtained;

[0010] S3, light-heat modification:

[0011] S301, immerse the porous wood substrate in a 10 g / L aqueous solution of tannic acid until saturated, and after drying, continue to immerse in a 2 g / L ferric sulfate solution, stir to mix thoroughly;

[0012] S302, continue to immerse in the photothermal modifier, and immerse in a vacuum for 1-2 h, then place in a 55-60°C drying oven for 2-3 h, repeat the immersion and drying operation 2 times to obtain a photothermal modified substrate;

[0013] S4, thermal modification:

[0014] Place the photothermal modified substrate in a 0.1 mol / L copper sulfate solution, immerse for 3-4 h, then continue to immerse in a 3-5 wt% ascorbic acid solution, and reduce at 55-65°C for 5-6 h, then wash and dry to obtain a photothermal-thermal modified substrate;

[0015] S5, hydrophobic modification:

[0016] Immerse the photothermal-thermal modified substrate in a hydrophobic agent, react at 60-70°C for 5-8 h, then place in a 75-80°C drying oven for 3-4 h to obtain a photothermal-thermal-hydrophobic substrate;

[0017] The hydrophobic agent includes octadecylamine, sophorolipid, maleic anhydride, and an ethanol aqueous solution in a mass ratio of 3:(0-1):2:100, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is (0.8-1):2;

[0018] S6, preparation of composite phase change heat storage material:

[0019] After placing the photothermal-thermal-hydrophobic substrate in a molten myristic acid, add a crosslinking agent, stir uniformly, then transfer to a vacuum drying oven for 4-5 h, remove the excess myristic acid on the surface to obtain a hydrothermal modified wood-based photothermal superhydrophobic composite phase change heat storage material;

[0020] The vacuum degree of the vacuum drying oven is set to -0.1 to -0.09 MPa, and an air charging-vacuuming cycle is performed every 1 h during the process.

[0021] Preferably, before washing the surface impurities with deionized water in S1, the following steps are included:

[0022] Place a small sample in a 5 wt% sophorolipid aqueous solution, and stir at a constant temperature of 55-60°C for 1.5-2 h.

[0023] Preferably, the wood is selected from one of redwood, poplar, and pine.

[0024] Preferably, in S2, the hydrothermal reagent is selected from distilled water;

[0025] Alternatively, the hydrothermal reagent is selected from an acid-modified liquid comprising citric acid, pyroligneous acid and deionized water in a mass ratio of 5:3:92.

[0026] Preferably, in the S301, the rotation speed of the stirring for sufficient mixing is 400-500 r / min.

[0027] Preferably, in the S302, the photo-thermal modifier comprises tannic acid, indium trichloride and deionized water in a mass ratio of 5:(0-2):100, and the preparation method comprises: dissolving tannic acid in deionized water and stirring until dissolved, adding indium trichloride, and stirring at 50-55℃ for 0.5-1h to obtain the photo-thermal modifier.

[0028] Preferably, in the S5, the hydrophobic agent comprises octadecylamine, sophorolipid, maleic anhydride and an ethanol aqueous solution in a mass ratio of 3:1:2:100, and in the ethanol aqueous solution, the mass ratio of anhydrous ethanol to deionized water is 3:7.

[0029] Preferably, in the S6, the addition amount of the crosslinking agent is 0.5-2% of the mass of myristic acid.

[0030] The crosslinking agent is selected from itaconic acid.

[0031] In a second aspect, a hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material is provided, which is prepared by the preparation method of the hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material as described above.

[0032] In a third aspect, the application provides a use of the hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material as described above in solar energy utilization.

[0033] The technical scheme provided by the application has the following beneficial effects:

[0034] The application provides a hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material, a preparation method and a use thereof. In the pretreatment stage, sophorolipid aqueous solution is used for degreasing and dewaxing to remove impurities on the surface of wood, providing a clean and active substrate for subsequent modification. Further, hydrothermal cleaning modification is used to remove lignin, forming a porous structure with good connectivity and uniform pore size distribution, increasing the phase change material loading space, improving the wood encapsulation efficiency and solving the phase change material leakage problem.

[0035] The complexation / reduction reaction of natural tannic acid and metal ions is utilized in the photothermal modification step to simultaneously endow the material with photothermal conversion and heat conduction functions, avoiding the use of toxic reagents. The photothermal modifier further forms a high-efficiency photothermal conversion layer on the inner wall of the wood pores. The complexation of the catechol group of tannic acid and indium ions enhances the broad-spectrum absorption capacity of sunlight, thereby improving the photothermal conversion efficiency. Subsequent in-situ generation of copper nanoparticles for heat conduction modification constructs a continuous heat conduction network in the pores, accelerating the transfer of heat from photothermal conversion to phase change materials. In the hydrophobic modification, octadecylamine is used as a low-surface-energy group donor, sophorolipid is used as a compatibility regulator, and maleic anhydride is used as a crosslinking agent. A dense and crosslinked superhydrophobic layer is formed on the surface of the wood through Schiff base reaction, which on one hand makes it difficult for pollutants to adhere, achieving self-cleaning and improving the durability of the material in complex environments, and on the other hand, the crosslinked hydrophobic layer further blocks the small gaps of the wood pores, combined with the slight crosslinking effect of itaconic acid during the impregnation of phase change materials, to reduce the leakage rate. Therefore, the problems of traditional phase change heat storage materials, such as easy leakage of phase change materials, poor heat conduction performance, and low packaging efficiency, can be solved. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 The preparation method flowchart of the hydrothermal modification wood-based photothermal superhydrophobic composite phase change heat storage material provided by the present application is shown in the following figure.

[0038] Figure 2 The electron microscope image of the hydrothermal modification wood-based photothermal superhydrophobic composite phase change heat storage material provided by the present application is shown in the following figure. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0040] Referring to Figures 1-2 As shown in the following figure, the present application provides a hydrothermal modification wood-based photothermal superhydrophobic composite phase change heat storage material and its preparation method and application.

[0041] It should be noted that the water retention treatment is to place the test piece in a container filled with water (or corresponding solution) after recording the weight of the test sample, and make the water (or corresponding solution) overflow the test piece. Boil the water (or corresponding solution) and keep it boiling for 5h. During the boiling process, the water level should be observed in time and the water loss due to evaporation should be supplemented in time to ensure that the test piece is always fully immersed in water (or corresponding solution);

[0042] After boiling is completed, stop heating and let the container and test piece cool naturally in water (or corresponding solution) to room temperature. After removing the test piece, wipe off the surface moisture with a wet towel and immediately measure its weight to check if the water saturation requirement is met (usually, if the weight difference between two measurements is not more than 0.1%, it is considered to meet the water saturation state. If not, continue the water saturation treatment).

[0043] In addition, in this application, unless otherwise specified, the operation of immersion or immersion means that the solid is completely immersed in the liquid.

[0044] Example 1

[0045] The preparation method of the hydrothermal modified wood-based photothermal super-hydrophobic composite phase change heat storage material provided in this embodiment includes the following steps:

[0046] S1, substrate pretreatment:

[0047] The red cone wood is processed into a small sample of 20mm×20mm×6mm, and the small sample is placed in a 5wt% sophorose lipid aqueous solution. Stir at 55℃ for 2h, wash the surface impurities with deionized water, and dry in a 103℃ drying oven until the weight is constant to obtain a pretreated substrate;

[0048] S2, porous wood matrix preparation:

[0049] After immersing 100g of pretreated substrate in distilled water, place it in a hydrothermal reaction kettle, set the treatment temperature to 140℃, and treat it at a constant temperature for 3h. Through hydrothermal action, part of the hemicellulose is degraded, the pore structure of the wood is enriched, and after cleaning and drying, a porous wood substrate is obtained;

[0050] S3, photothermal modification:

[0051] S301, immerse the porous wood substrate in a 10g / L tannin acid aqueous solution until it is saturated. After drying at 103℃ for 2h, continue to immerse it in a 2g / L ferric sulfate solution, and stir at a speed of 400r / min to mix thoroughly. Complexation reaction occurs between tannin acid and Fe 3+ to form a black complex;

[0052] S302, continue to immerse in the photothermal modifier and immerse in vacuum (-0.08MPa) for 1.5h. After taking out, place it in a 60℃ drying oven for 3h. Repeat the immersion and drying operation of S302 for 2 times to obtain a photothermal modified substrate.

[0053] wherein the photothermal modifier is a mixture of 5 g tannic acid, 1 g indium trichloride and 100 g deionized water; the preparation method is as follows:

[0054] After dissolving tannic acid in deionized water, stirring to dissolve, adding indium trichloride, stirring at 55°C for 1 h, and then obtaining the photothermal modifier.

[0055] S4, thermal modification:

[0056] The photothermal modified substrate is placed in a 0.1 mol / L copper sulfate solution, immersed for 3 h, then immersed in a 3 wt% ascorbic acid solution, and reduced at 60°C for 6 h, then washed and dried to obtain a photothermal-thermal modified substrate. Ascorbic acid reduces Cu 2+ nanoparticles and loads them inside the wood;

[0057] S5, hydrophobic modification:

[0058] The photothermal-thermal modified substrate is immersed in a hydrophobic agent at 65°C for 6 h, then taken out and placed in a 75°C drying oven for 4 h to obtain a photothermal-thermal-hydrophobic substrate.

[0059] The hydrophobic agent is a mixture of 3 g octadecylamine, 1 g sophorolipid, 2 g maleic anhydride and 100 g ethanol aqueous solution, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 3:7.

[0060] S6, preparation of composite phase change heat storage material:

[0061] Take 70 g of the photothermal-thermal-hydrophobic substrate and place it in 100 g of molten myristic acid (MA), then add 0.5 g of itaconic acid, stir evenly, and then transfer to a vacuum drying oven at -0.1 MPa for 4.5 h (during which the temperature is raised to 65°C to completely melt the myristic acid), and during which the gas- vacuum cycle is performed every 1 h to ensure that the MA is fully penetrated; after impregnation, remove the excess myristic acid on the surface by washing to obtain a hydrothermal modified wood-based photothermal superhydrophobic composite phase change heat storage material.

[0062] Example 2

[0063] The difference between this example and Example 1 is that in this example, the hydrothermal reaction agent of S2 step is an acid modification liquid, wherein the acid modification liquid is a mixture of 5 g citric acid, 3 g pyroligneous acid and 92 g deionized water.

[0064] Example 3

[0065] The difference between this example and Example 1 is that in this example, S1 includes the following steps:

[0066] S1, substrate pretreatment:

[0067] The red cone wood was processed into 20mm x 20mm x 6mm samples, washed with deionized water to remove surface impurities, and then placed in a 103°C drying oven until constant weight was obtained to obtain the pretreated substrate.

[0068] In S302, the photothermal modifier is a mixture of 5g tannic acid and 100g deionized water.

[0069] Example 4

[0070] The preparation method of the hydrothermal modified wood-based photothermal super-hydrophobic composite phase change heat storage material provided in this embodiment includes the following steps:

[0071] S1, substrate pretreatment:

[0072] The poplar wood was processed into 20mm x 20mm x 6mm samples, the samples were placed in a 5wt% sophorose lipid aqueous solution, stirred at 60°C for 1.5h, washed with deionized water to remove surface impurities, and then placed in a 100°C drying oven until constant weight was obtained to obtain the pretreated substrate;

[0073] S2, porous wood matrix preparation:

[0074] After immersing 100g of the pretreated substrate in distilled water, it was placed in a hydrothermal reaction kettle, the treatment temperature was set to 135°C, and it was treated at constant temperature for 4h. After cleaning and drying, the porous wood substrate was obtained;

[0075] S3, photothermal modification:

[0076] S301, immerse the porous wood substrate in a 10g / L tannic acid aqueous solution until saturated, dry at 100°C for 2h, then immerse in a 2g / L ferric sulfate solution, and stir at a speed of 500r / min to ensure thorough mixing;

[0077] S302, continue to immerse in the photothermal modifier, and immerse in a vacuum (-0.08MPa) for 1h, then place it in a 55°C drying oven for 3h. Repeat the immersion and drying operations of S302 twice to obtain the photothermal modified substrate;

[0078] The photothermal modifier is a mixture of 5g tannic acid, 2g indium trichloride, and 100g deionized water; and the preparation method is as follows:

[0079] After dissolving the tannic acid in deionized water and stirring until dissolved, add indium trichloride, and stir at 50°C for 1h to obtain the photothermal modifier.

[0080] S4, thermal modification:

[0081] The photo-thermal modified substrate is placed in a 0.1 mol / L copper sulfate solution, soaked for 4 h, then continuously soaked in a 5 wt% ascorbic acid solution, and reduced at 55°C for 6 h, then washed and dried to obtain a photo-thermal-thermal modified substrate;

[0082] S5, hydrophobic modification:

[0083] The photo-thermal-thermal modified substrate is soaked in a hydrophobic agent at 60°C for 8 h, then taken out and placed in a 80°C drying oven for 3 h to obtain a photo-thermal-thermal-hydrophobic substrate.

[0084] The hydrophobic agent is a mixture of 3 g of octadecylamine, 2 g of maleic anhydride, and 100 g of an ethanol aqueous solution, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 1:2.

[0085] S6, preparation of composite phase change heat storage material:

[0086] 70 g of the photo-thermal-thermal-hydrophobic substrate is placed in 100 g of molten myristic acid (MA), 1 g of itaconic acid is added, stirred uniformly, and then transferred to a vacuum drying oven at -0.1 MPa for 4 h (during which the temperature is raised to 60°C to completely melt the myristic acid), and the gas charging-vacuum pumping cycle is performed every 1 h to ensure that the MA is fully penetrated; after the impregnation is completed, the excess myristic acid on the surface is removed by washing to obtain a hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material.

[0087] Example 5

[0088] The preparation method of the hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material provided in this embodiment comprises the following steps:

[0089] S1, substrate pretreatment:

[0090] The pine wood is processed into small samples of 20 mm x 20 mm x 6 mm, the small samples are placed in a 5 wt% sophorose aqueous solution, stirred at 55°C for 1.5 h, the surface impurities are washed with deionized water, and the samples are dried in a 105°C drying oven to constant weight to obtain a pretreated substrate.

[0091] S2, preparation of porous wood matrix:

[0092] 100 g of the pretreated substrate is immersed in an acid modification solution, then placed in a hydrothermal reaction kettle, the treatment temperature is set to 145°C, and the temperature is kept constant for 3 h, then washed and dried to obtain a porous wood substrate.

[0093] The acid modification solution is a mixture of 5 g of citric acid, 3 g of pyroligneous acid, and 92 g of deionized water.

[0094] S3, photo-thermal modification:

[0095] S301, immerse the porous wood substrate in a 10 g / L aqueous solution of tannic acid until saturated, continue to immerse in a 2 g / L ferric sulfate solution after drying at 105°C for 2 h, and stir at a speed of 450 r / min to ensure thorough mixing;

[0096] S302, continue to immerse in the photothermal modifier and immerse in a vacuum (-0.08 MPa) for 2 h, then place in a 60°C drying oven for 2 h, repeat the immersion and drying operation of S302 for 2 times to obtain the photothermal modified substrate;

[0097] The photothermal modifier is a mixture of 5 g tannic acid, 1 g indium trichloride, and 100 g deionized water; the preparation method is as follows:

[0098] After dissolving the tannic acid in deionized water and stirring to dissolve, add indium trichloride, and stir at 55°C for 0.5 h to obtain the photothermal modifier.

[0099] S4, thermal modification:

[0100] Place the photothermal modified substrate in a 0.1 mol / L copper sulfate solution, immerse for 3 h, then continue to immerse in a 3 wt% ascorbic acid solution, and reduce at 65°C for 5 h, then wash and dry to obtain the photothermal-thermal modified substrate;

[0101] S5, hydrophobic modification:

[0102] Immerse the photothermal-thermal modified substrate in the hydrophobic agent, react at 60°C for 8 h, then place in an 80°C drying oven for 3 h to obtain the photothermal-thermal-hydrophobic substrate;

[0103] The hydrophobic agent is a mixture of 3 g octadecylamine, 0.5 g sophorolipid, 2 g maleic anhydride, and 100 g aqueous ethanol solution, and the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 2:5.

[0104] S6, preparation of composite phase change heat storage material:

[0105] Take 70 g of the photothermal-thermal-hydrophobic substrate and immerse it in 100 g of molten myristic acid (MA), then add 0.3 g of itaconic acid, stir uniformly, and then transfer to a vacuum drying oven at -0.09 MPa for 4 h (during which the temperature is raised to 65°C to completely melt the myristic acid), and during which the gas- vacuum cycle is performed every 1 h to ensure that the MA is fully penetrated; after the immersion is completed, remove the excess myristic acid on the surface by washing to obtain the hydrothermal modified wood-based photothermal superhydrophobic composite phase change heat storage material.

[0106] Comparative Example 1

[0107] The difference between this comparative example and Example 1 is that in this comparative example, step S1 does not immerse sophorolipid, and step S302 is not performed.

[0108] Comparative Example 2

[0109] The difference between this comparative example and Example 1 is that, in this comparative example, step S302 is not performed, and step S4 is not performed.

[0110] Comparative Example 3

[0111] The difference between this comparative example and Example 1 is that, in this comparative example, step S302 is not performed, and the hydrophobic agent is not impregnated in step S5.

[0112] Comparative Example 4

[0113] The difference between this comparative example and Example 1 is that, in this comparative example, step S4 is not performed, and the hydrophobic agent is not impregnated in step S5.

[0114] The hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material (hereinafter referred to as “composite material”) prepared in the examples and comparative examples was subjected to performance testing.

[0115] Leakage prevention performance test:

[0116] 10 g of the composite material to be tested was placed in a 70°C constant temperature oven, and filter paper was laid on the surface. After 3 h and 5 h of heat preservation, the filter paper was taken out, weighed, and the leakage rate was calculated.

[0117]

[0118] Packaging efficiency test:

[0119] The latent heat of phase change of myristic acid is a constant value. The actual latent heat of phase change of the composite material was tested by differential scanning calorimetry (DSC), and the proportion of effective phase change material loaded was calculated.

[0120]

[0121] The results are shown in Table 1.

[0122] Table 1 Leakage rate and packaging efficiency of the composite material of the examples and comparative examples

[0123]

[0124] It should be noted that “no leakage” in Table 1 means that the leakage rate is ≤0.1%.

[0125] Compared with Example 1 in which distilled water is used as the hydrothermal reagent, the etching effect on the wood cell wall is more moderate and uniform, the formed pore connectivity is good, and the pore size distribution is reasonable, which can greatly improve the packaging efficiency and reduce the leakage rate; Example 3 does not add indium trichloride, and there is no sophorolipid pretreatment, so the wood surface active site is less, resulting in low packaging efficiency and increased leakage.

[0126] In step S4, the filling effect of copper nanoparticles further blocks the gap between the pores. Comparative Example 2 and Comparative Example 4 do not perform this step, and the anti-leakage performance is poor.

[0127] Photo-thermal conversion efficiency test:

[0128] The photo-thermal conversion efficiency (xenon lamp simulated light intensity 1000 W / m 2 The surface temperature of the sample was recorded by an infrared thermal imager, and the photo-thermal conversion efficiency when the heat balance was reached was calculated.

[0129] Table 2 Photo-thermal conversion efficiency and thermal conductivity of examples and comparative examples

[0130]

[0131] In step S4, the ascorbic acid reduction generates copper nanoparticles that form a continuous thermal conduction network in the wood pores, significantly improving heat transfer efficiency. Comparative Example 2 and Comparative Example 4, which lack step S4, have the lowest thermal conductivity; the reduction temperature of Example 5 is increased to 65°C, and the crystallinity of the copper nanoparticles is higher, resulting in the best thermal conductivity.

[0132] As can be seen from Table 2, the indium ions introduced by the photo-thermal modifier in step S302 can enhance the absorption of near-infrared light. In Example 3, no indium trichloride is added, and the photo-thermal conversion efficiency is greatly reduced. In Example 5, the vacuum impregnation time is extended to 2h, and the modification layer is more fully loaded, resulting in the highest photo-thermal conversion efficiency.

[0133] Hydrophobic and self-cleaning ability test:

[0134] A contact angle measuring instrument was used to drop 5 μL of deionized water droplets on the surface of the composite material, and the contact angles at 5 different positions were tested. The average value was taken as the surface contact angle.

[0135] An artificial pollutant solution (carbon black suspension, 1 g / L) was uniformly sprayed on the surface of the sample, and then washed with deionized water for 30 s. The color difference ΔE of the sample before and after washing was measured by a color difference meter, and the pollutant removal rate was calculated.

[0136]

[0137] The results are shown in Table 3.

[0138] Table 3 Surface contact angle and contaminant removal rate of the composite material of the examples and comparative examples

[0139]

[0140] The self-cleaning and anti-pollution capabilities of the composite material provided in the present application are realized by the low surface energy and rough structure of the super-hydrophobic surface. The greater the contact angle, the better the self-cleaning capability. Step S5 provides a low surface energy group through octadecylamine, and maleic anhydride is cross-linked and fixed on the wood surface through Schiff base reaction. Sophorolipid as a biosurfactant further improves the uniformity and adhesion of the hydrophobic layer. Example 4 does not add sophorolipid, and the contact angle and stability are slightly lower. Comparative example 3 and comparative example 4 have significantly decreased super-hydrophobic performance due to the absence of hydrophobic agent impregnation.

[0141] Referring to Figure 2 The composite material prepared in Example 1 is shown in the electron microscope image, and it can be known that the composite material prepared in Example 1 shows moderate surface roughness under the synergistic effect of photo-thermal-thermal-conductive-hydrophobic layer, which lays a structural foundation for constructing a low-surface-energy super-hydrophobic layer with octadecylamine. At the same time, the larger specific surface area brought by the rough surface structure also provides sufficient light absorption sites for its excellent photo-thermal conversion performance.

[0142] Further, the composite material prepared in Example 1 is further tested. The latent heat of fusion is 87.1 J / g, the latent heat of solidification is 86.1 J / g, and the phase change temperature is suitable for low-temperature heat storage scenes (48-53℃); and the reaction conditions of each step are mild (room temperature-145℃), without the need for complex equipment, and convenient for industrial production.

[0143] The composite material provided in the present application can be used as a core component of heat collection and storage integration in the field of solar photo-thermal utilization, realizing efficient capture, storage and release of solar energy. During the light period, the tannic acid-indium trichloride photo-thermal conversion layer of the material can efficiently absorb sunlight (especially in the near-infrared band) and convert it into heat energy, which is quickly transferred to the internal phase change material through the copper nanoparticle thermal conduction network, prompting it to melt and store a large amount of latent heat. During the period without light (such as at night or on rainy days), the phase change material solidifies and releases heat, providing a stable heat source for building heating, hot water supply or industrial low-temperature heating.

[0144] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A method for preparing a hydrothermally modified wood-based photothermal superhydrophobic composite phase change heat storage material, characterized in that, It comprises the following steps: S1, substrate pretreatment: The wood is processed into a small sample of 20mmx20mmx6mm, and the small sample is placed in a 5wt% sophorose lipid aqueous solution. After constant temperature stirring at 55~60℃ for 1.5~2h, the surface impurities are washed with deionized water, and the pretreated substrate is dried to constant weight in a drying box. S2, porous wood matrix preparation: After the pretreated substrate is immersed in a hydrothermal reaction agent, it is placed in a hydrothermal reaction kettle, the treatment temperature is set to 135~145℃, and constant temperature treatment is carried out for 3~4h. After washing and drying, a porous wood substrate is obtained. The hydrothermal reaction agent is selected from distilled water. Alternatively, the hydrothermal reaction agent is selected from an acid-modified liquid, which includes citric acid, wood vinegar and deionized water in a mass ratio of 5:3:

92. S3, photo-thermal modification: S301, immerse the porous wood substrate in a 10g / L tannin acid aqueous solution until it is saturated with water, and then immerse it in a 2g / L ferric sulfate solution after drying. Stir to mix thoroughly. S302, continue to immerse in the photo-thermal modifier, and vacuum impregnate for 1~2h. After taking out, place it in a 55~60℃ drying box for 2~3h. Repeat the immersion and drying operation 2 times to obtain a photo-thermal modified substrate. The photo-thermal modifier includes tannic acid, indium trichloride and deionized water in a mass ratio of 5:(1~2):

100. Its preparation method comprises: dissolving tannic acid in deionized water and stirring until dissolved. Add indium trichloride, and stir at 50~55℃ for 0.5~1h to obtain the photo-thermal modifier. S4, thermal conductivity modification: Place the photo-thermal modified substrate in a 0.1mol / L copper sulfate solution, immerse for 3~4h, then continue to immerse in a 3~5wt% ascorbic acid solution, and reduce for 5~6h at 55~65℃. After washing and drying, a photo-thermal-thermal modified substrate is obtained. S5, hydrophobic modification: Immerse the photo-thermal-thermal modified substrate in a hydrophobic agent, and react at 60~70℃ for 5~8h. After taking out, place it in a 75~80℃ drying box for 3~4h to solidify, and obtain a photo-thermal-thermal-hydrophobic substrate. The hydrophobic agent includes octadecylamine, sophorose lipid, maleic anhydride and ethanol aqueous solution in a mass ratio of 3:(0.5~1):2:

100. In the ethanol aqueous solution, the mass ratio of anhydrous ethanol to deionized water is (0.8~1):

2. S6, preparation of composite phase change heat storage material: After placing the photo-thermal-thermal-hydrophobic substrate in a molten myristic acid, add a crosslinking agent, stir uniformly, and then transfer to a vacuum drying box for 4~5h. After removing the excess myristic acid on the surface, a hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material is obtained. The addition amount of the crosslinking agent is 0.5~2% of the mass of myristic acid. The crosslinking agent is selected from itaconic acid. The vacuum degree of the vacuum drying box is set to -0.1~-0.09MPa, and the cycle of inflation and vacuumization is carried out every 1h during the period.

2. The preparation method of the hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material according to claim 1, wherein: The wood is selected from one of red cone wood, poplar wood and pine wood. 3.The method of claim 1, wherein the wood-based photothermal super-hydrophobic composite phase change heat storage material is prepared by the method. In the S301, the stirring speed for the sufficient mixing is 400-500 r / min. 4.The method of claim 1, wherein the wood-based photothermal super-hydrophobic composite phase change heat storage material is prepared by the method. In the S5, the hydrophobic agent comprises octadecylamine, sophorolipid, maleic anhydride and an ethanol aqueous solution at a mass ratio of 3:1:2:100, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 3:

7.

5. A hydrothermally modified wood-based photo-thermal super-hydrophobic composite phase change heat storage material, characterized in that, The wood-based photothermal super-hydrophobic composite phase change heat storage material is prepared by the method of any one of claims 1-4. 6.The wood-based photothermal super-hydrophobic composite phase change heat storage material of claim 5 is applied in solar energy utilization.

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