CN114316922A - Composite phase change material for encapsulating lauric acid and preparation method thereof - Google Patents
Composite phase change material for encapsulating lauric acid and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of phase change materials, and discloses a composite phase change material for encapsulating lauric acid and a preparation method thereof, wherein the composite phase change material comprises aerogel which is formed by cross-linking and has a three-dimensional porous structure and the lauric acid encapsulated in the aerogel which has the three-dimensional porous structure; the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking poplar catkin carbon sheets under the action of a crosslinking agent; the cross-linking agent is polyvinyl alcohol aqueous solution. The poplar catkin carbon sheet is a polydopamine modified poplar catkin carbon sheet. According to the invention, the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating lauric acid is prepared by using poplar catkin, the materials involved in the preparation process are cheap and easily available, and are harmless to the environment, the problems of high preparation cost and complex preparation process of the traditional graphene aerogel can be effectively solved, the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material has the capacity of industrial production and practical application, and a new thought is provided for application of biomass.
Description
Technical Field
The invention relates to the technical field of phase-change materials, and discloses a composite phase-change material for encapsulating lauric acid and a preparation method thereof.
Background
With the rapid development of economy and the continuous improvement of people's life, the demand for energy is gradually increased, and the energy shortage is aggravated by the increase of the number of the world population. At present, the energy source mainly depends on fossil fuels such as coal and petroleum, but the fossil fuels belong to non-renewable energy sources, and the environment is inevitably polluted by the fossil fuels, so that the development of clean and renewable energy sources is an effective method for solving the problem.
Solar energy has the advantages of no regional limitation, large energy, no pollution and the like as renewable clean energy, but the intermittence and randomness of the solar energy often cause imbalance of supply and demand and low utilization efficiency, so that the key point of effectively utilizing the solar energy is to capture the solar energy and store the solar energy as heat energy. The phase change material stores a large amount of solar energy in the form of latent heat and releases the solar energy again at a constant phase change temperature, and is a promising energy storage medium. Among the phase change materials that have been studied, solid-liquid phase change materials have received much attention because of their large latent heat capacity, constant phase change temperature, small volume change, and repeatable storage/release characteristics. However, the solid-liquid phase change material inevitably leaks in the phase change process, thereby affecting the heat storage performance of the phase change material and shortening the service life of the phase change material.
In order to solve these problems, the aerogel with ultra-low density, ultra-high porosity and large specific surface area has been widely used for the synthesis of shape-stable phase-change materials, wherein the graphene aerogel is paid attention by researchers due to its good thermal conductivity and good absorption of visible light in the range of 400-760 nm, but its high manufacturing cost and complicated manufacturing process limit its industrial mass production and application. Based on the above, it is very necessary to prepare a phase change material which is low in price and environment-friendly.
Disclosure of Invention
The invention aims to overcome the defects and provide a composite phase-change material for encapsulating lauric acid and a preparation method thereof.
In order to achieve the purpose, the invention is implemented according to the following technical scheme:
a composite phase change material for encapsulating lauric acid, wherein the composite phase change material comprises aerogel formed by crosslinking and having an interconnected three-dimensional porous structure, and lauric acid encapsulated in the aerogel having an interconnected three-dimensional porous structure;
the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking poplar catkin carbon sheets under the action of a crosslinking agent;
the cross-linking agent is polyvinyl alcohol aqueous solution.
The pores of the aerogel having a three-dimensional cellular structure interconnected with each other are interconnected. The macroscopic shape of the aerogel having a three-dimensional cellular structure interconnected can be controlled by the mold.
Preferably, the poplar catkin carbon sheet is a polydopamine modified poplar catkin carbon sheet.
Preferably, the concentration of the polyvinyl alcohol aqueous solution is 5g/L to 20 g/L.
Preferably, the mass ratio of the polydopamine-modified poplar catkin carbon sheet to the polyvinyl alcohol is 5-9: 1-5.
Preferably, the lauric acid is automatically encapsulated in the aerogel having a three-dimensional pore structure interconnected with each other.
The invention also discloses a preparation method of the lauric acid encapsulated composite phase-change material, which comprises the following steps:
s1, repeatedly cleaning the poplar catkins by using deionized water and absolute ethyl alcohol, and drying in an oven at 70 ℃ for 18h to obtain dried poplar catkins;
s2, annealing the dried poplar catkins for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed poplar catkins carbon tube; the temperature rise rate in the annealing process is 5 ℃/min;
s3, carrying out ultrasonic crushing treatment on the annealed poplar carbon tube in absolute ethyl alcohol, and drying after the treatment to obtain a poplar carbon sheet;
s4, dispersing the poplar catkin carbon sheets in tris-HCl buffer solution, adding dopamine hydrochloride, opening, stirring, centrifuging and drying to obtain polydopamine modified poplar catkin carbon sheets;
s5, adding the poly-dopamine modified poplar catkin carbon sheet into a polyvinyl alcohol aqueous solution, stirring at room temperature, pouring into a mold, freezing for 2 hours in a refrigerator, and then freeze-drying to obtain aerogel with mutually communicated three-dimensional porous structures; stirring at room temperature for 24h, and freeze-drying for 18h by using a freeze dryer;
s6, placing lauric acid in a beaker, heating and melting the lauric acid in water bath at 50 ℃, then placing the aerogel with the three-dimensional porous structures which are mutually communicated, and automatically completing encapsulation of the lauric acid by the aerogel with the three-dimensional porous structures which are mutually communicated due to capillary force and surface tension to obtain the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating the lauric acid.
Preferably, in step S4, the pH of the tris-HCl buffer solution is 8.5, and the volume ratio of the mass of the poplar carbon flake to the tris-HCl buffer solution is 1g:200mL to 400 mL; the mass ratio of the poplar catkin carbon sheets to the dopamine hydrochloride is 1: 4; the stirring time was 24 h.
Preferably, in the step S5, the concentration of the polyvinyl alcohol aqueous solution is 5g/L to 20 g/L; the mass ratio of the poly-dopamine modified poplar catkin carbon sheets to the polyvinyl alcohol is 5-9: 1-5.
The invention has the following function principle:
the polydopamine-modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating lauric acid prepared by the invention is prepared by using polydopamine-modified poplar catkin carbon sheet/polyvinyl alcohol (aerogel with mutually communicated three-dimensional porous structures) as a supporting material and encapsulating the composite phase change material of lauric acid. The method comprises the steps of firstly, modifying a poplar catkin carbon sheet by dopamine hydrochloride to obtain a polydopamine modified poplar catkin carbon sheet with rich oxygen-containing functional groups (hydroxyl groups) on the surface; and then, mixing and stirring the polydopamine modified poplar catkin carbon sheets and the polydopamine modified poplar catkin carbon sheets for 24 hours at normal temperature by using a polyvinyl alcohol aqueous solution as a cross-linking agent, enabling the polydopamine modified poplar catkin carbon sheets to be subjected to self-assembly through the action of hydrogen bonding force in the stirring process to form a microscopic three-dimensional network structure, and finally, freezing and drying the stirred suspension liquid to obtain the macroscopic shape-adjustable interconnected three-dimensional porous structure aerogel. Because the aerogel has a unique three-dimensional porous structure which is communicated with each other, the aerogel has the characteristics of low density, high porosity, large specific surface area and the like, and the aerogel also has higher lauric acid encapsulation rate.
Compared with the prior art, the invention has the beneficial effects that:
the invention utilizes poplar seed to prepare the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material for encapsulating lauric acid, the aerogel with the mutually communicated three-dimensional porous structure prepared by the invention has larger encapsulating amount of lauric acid, about 3g of lauric acid can be encapsulated by about 0.27g of aerogel, the encapsulating rate can reach 88.1 percent at most, and the phase change material can still keep good mechanical and chemical stability after multiple heat absorbing and releasing cycles. The materials involved in the preparation process are cheap and easy to obtain, and the preparation method is harmless to the environment, can effectively solve the problems of high preparation cost and complex preparation process of the traditional graphene aerogel, has the capacity of industrial production and practical application, and provides a new idea for application of biomass.
Drawings
FIG. 1 is a diagram of the aerogel having interconnected three-dimensional cellular structures obtained in step 7 in example 1 of the present invention;
FIG. 2 is a Scanning Electron Microscope (SEM) image of an aerogel having interconnected three-dimensional cellular structures obtained in step 7 in example 1 of the present invention;
fig. 3 is a graph showing the change in mass of aerogels having three-dimensional interconnected pore structures obtained in examples 1 and 2 of the present invention before and after encapsulating lauric acid;
fig. 4 is a graph comparing thermal stability of pure lauric acid, the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 1, and the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 2;
fig. 5 is a graph showing heat absorption and release properties of pure lauric acid, the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 1, and the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 2;
fig. 6 is a graph of Differential Scanning Calorimetry (DSC) performance of pure lauric acid, polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid of example 1, and polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid of example 2;
fig. 7 is an XRD spectrum of pure lauric acid, polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid of example 1;
fig. 8 is a thermal conductivity graph of pure lauric acid, the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 1, and the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 2.
Detailed Description
The present invention will be further described with reference to specific examples, which are illustrative of the invention and are not to be construed as limiting the invention.
Example 1
A composite phase change material for encapsulating lauric acid, wherein the composite phase change material comprises aerogel formed by crosslinking and having an interconnected three-dimensional porous structure, and lauric acid encapsulated in the aerogel having an interconnected three-dimensional porous structure; the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking poplar catkin carbon sheets under the action of a polyvinyl alcohol aqueous solution; the poplar catkin carbon sheet is a polydopamine modified poplar catkin carbon sheet.
The preparation method of the composite phase-change material for encapsulating lauric acid comprises the following steps:
1) cleaning the collected poplar catkins with deionized water and absolute ethyl alcohol for multiple times, and drying the poplar catkins in a drying oven at 70 ℃ for 18 hours to obtain dried poplar catkins;
2) putting the dried poplar catkins into a tubular furnace, and annealing for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed poplar catkins carbon tube; the heating rate is 5 ℃/min;
3) carrying out ultrasonic crushing treatment on the annealed poplar carbon tubes in absolute ethyl alcohol for 6 hours, and drying to obtain poplar carbon sheets;
4) weighing 1.22114g of tris (hydroxymethyl) aminomethane reagent, dissolving in 980mL of deionized water, adjusting the pH value to 8.5 by using 1mol/L hydrochloric acid prepared in advance (real-time measurement by using a pH meter), transferring to a 1000mL volumetric flask, and fixing the volume by using deionized water to obtain tris-HCl buffer solution with the pH value of 8.5;
5) taking 0.5g of poplar catkin carbon sheet obtained in the step 3), putting the poplar catkin carbon sheet into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse the poplar catkin carbon sheet, then adding 2g of dopamine hydrochloride into the poplar catkin carbon sheet, and violently stirring for 24h in an open mode, centrifuging and drying to obtain a polydopamine modified poplar catkin carbon sheet;
6) adding 0.06g of polyvinyl alcohol solid into 4mL of water, heating the mixture in an oil bath at 95 ℃ until the mixture is molten, and then cooling the mixture to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) adding 0.24g of the polydopamine modified poplar catkin carbon sheet obtained in the step 5) into the polyvinyl alcohol aqueous solution (15g/L) obtained in the step 6), stirring at room temperature for 24 hours, pouring into a mold, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting the lauric acid in water bath at 50 ℃, then putting the aerogel with the mutually communicated three-dimensional porous structures, and automatically completing encapsulation of the lauric acid in a few minutes due to capillary force and surface tension to obtain the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating the lauric acid, wherein the notation is LA @ PCP 8: 2.
As shown in fig. 1, a product diagram of the aerogel having the interconnected three-dimensional pore-like structure obtained in step 7 in example 1 of the present invention is shown. The figure shows that the aerogel with the interconnected three-dimensional pore-shaped structure obtained in example 1 can be stably placed on the setaria viridis, so that the aerogel prepared by the invention has light weight and low density.
As shown in fig. 2, it is a Scanning Electron Microscope (SEM) image of the aerogel having the interconnected three-dimensional pore-like structure obtained in step 7 in example 1 of the present invention. As can be seen from the figure, the poly-dopamine modified poplar catkin carbon sheets are assembled under the action of the cross-linking agent polyvinyl alcohol to form a mutually communicated three-dimensional porous structure, and the aperture is about 1-6 μm.
As shown in FIG. 3, FIG. 3a is a graph showing the mass of the aerogel having interconnected three-dimensional pore-like structures prepared in example 1, which is 0.2740 g; FIG. 3b shows the mass of encapsulated lauric acid of the aerogel having a three-dimensional pore structure interconnected as prepared in example 1, which is 3.2406 g.
In example 1, the aerogel having an interconnected three-dimensional cellular structure obtained in step 7 had a mass of 0.2740g and a volume of 8.36cm3The bulk density was calculated to be 0.03277g/cm3(ii) a After the step 8, the mass of the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material (LA @ PCP 8:2) for encapsulating lauric acid obtained in the embodiment is 3.2406g, which indicates that the encapsulating mass of lauric acid in the embodiment is 2.9666 g.
As shown in FIG. 4, FIG. 4a shows pure solid lauric acid (denoted as LA) in the form of a cylinder having a mass of 3.2104g at 25 ℃; 0s at 65 ℃; 30s at 65 ℃; 60s at 65 ℃; 50 ℃ for 10 min; five temperature time conditions.
FIG. 4b shows that the polydopamine modified Populus catkin carbon sheet/polyvinyl alcohol composite phase change material (LA @ PCP 8:2) with mass of 3.2406g and encapsulated lauric acid, which is obtained in example 1, is in a cylinder shape at 25 ℃; 0s at 65 ℃; 30s at 65 ℃; 60s at 65 ℃; 50 ℃ for 10 min; five temperature time conditions.
Pure lauric acid and the polydopamine-modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid obtained in example 1 can maintain the shape stability at room temperature (25 ℃). When the temperature is raised to 65 ℃ which is higher than the phase transition temperature of lauric acid, the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid obtained in example 1 is not obviously leaked when heated for 60s under the condition of 65 ℃ (fig. 3b), but pure lauric acid begins to melt when heated for 30s under the condition of 65 ℃ (fig. 3a) and is converted into liquid from solid. Pure lauric acid and the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating the lauric acid obtained in example 1 were heated at 50 ℃ for 10min, and the mass of the remaining solid was weighed respectively. Pure lauric acid melted seriously and the mass of the solid changed from 3.2104g to 1.032 g. The mass of the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating lauric acid obtained in example 1 is almost unchanged, and is changed from 3.2406g to 3.108 g.
As shown in fig. 7, the XRD spectrum of the polydopamine modified populus carbon sheet/polyvinyl alcohol composite phase change material which is pure lauric acid and encapsulates lauric acid in example 1. Example 1 a polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material (LA @ PCP 8:2) encapsulating lauric acid exhibited diffraction signature peaks similar to pure Lauric Acid (LA), indicating that lauric acid has better chemical compatibility with the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol aerogel. Moreover, the degree of crystallization of lauric acid in the pores of the aerogel was not affected.
Example 2
The preparation method of the composite phase-change material for encapsulating lauric acid comprises the following steps:
1) cleaning the collected poplar catkins with deionized water and absolute ethyl alcohol for multiple times, and drying the poplar catkins in a drying oven at 70 ℃ for 18 hours to obtain dried poplar catkins;
2) putting the dried poplar catkins into a tubular furnace, and annealing for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed poplar catkins carbon tube; the heating rate is 5 ℃/min;
3) carrying out ultrasonic crushing treatment on the annealed poplar carbon tubes in absolute ethyl alcohol for 6 hours, and drying to obtain poplar carbon sheets;
4) weighing 1.22114g of tris (hydroxymethyl) aminomethane reagent, dissolving in 980mL of deionized water, adjusting the pH value to 8.5 by using 1mol/L hydrochloric acid prepared in advance (real-time measurement by using a pH meter), transferring to a 1000mL volumetric flask, and fixing the volume by using deionized water to obtain tris-HCl buffer solution with the pH value of 8.5;
5) taking 0.5g of poplar catkin carbon sheet obtained in the step 3), putting the poplar catkin carbon sheet into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse the poplar catkin carbon sheet, then adding 2g of dopamine hydrochloride into the poplar catkin carbon sheet, and violently stirring for 24h in an open mode, centrifuging and drying to obtain a polydopamine modified poplar catkin carbon sheet;
6) adding 0.03g of polyvinyl alcohol solid into 3.75mL of water, heating the mixture in an oil bath at 95 ℃ until the mixture is molten, and then cooling the mixture to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) adding 0.27g of the polydopamine modified poplar catkin carbon sheet obtained in the step 5) into the polyvinyl alcohol aqueous solution (8g/L) obtained in the step 6), stirring at room temperature for 24 hours, pouring into a mold, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting the lauric acid in water bath at 50 ℃, then putting the aerogel with the mutually communicated three-dimensional porous structure, and automatically completing encapsulation of the lauric acid in a few minutes by the aerogel with the mutually communicated three-dimensional porous structure to obtain the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating the lauric acid, which is recorded as @ LA PCP 9: 1.
As shown in FIG. 3, FIG. 3c is a graph showing the mass of the aerogel having interconnected three-dimensional pore-like structures prepared in example 2, which is 0.2645 g; FIG. 3d is a mass of 3.1600g of encapsulated lauric acid of aerogel having a three-dimensional pore structure interconnected as prepared in example 2.
In example 2, the mass of the aerogel having an interconnected three-dimensional cellular structure obtained in step 7 was 0.2645 g; after the step 8, the mass of the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material (LA @ PCP 9:1) for encapsulating lauric acid obtained in the embodiment is 3.1600g, which indicates that the encapsulating mass of lauric acid in the embodiment is 2.8955 g.
As shown in fig. 4, fig. 4c shows the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material (LA @ PCP 9:1) encapsulating lauric acid of example 2 at 25 ℃; 0s at 65 ℃; 30s at 65 ℃; 60s at 65 ℃; 50 ℃ for 10 min; five temperature time conditions.
At 25 ℃; the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating lauric acid in the embodiment 2 can maintain shape stability and has no obvious leakage under the conditions of 65 ℃, 30 seconds and 65 ℃ and 60 seconds. When the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 2 is heated at 50 ℃ for 10min, no obvious leakage exists, and the mass is only reduced by 0.0687g compared with that before heating.
The absorption and release thermal performance test of the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material with encapsulated lauric acid of examples 1 and 2 was carried out by using a 60 ℃ water bath as a heat source, as shown in fig. 5, fig. 5a shows that the temperature rise rate of the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material (LA @ PCP 9:1) with encapsulated lauric acid of example 2 is greater than that of the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material (LA @ PCP 8:2) with encapsulated lauric acid of example 1 is greater than that of pure Lauric Acid (LA), and thus, compared with pure lauric acid, the thermal conductivity of the composite phase change material with encapsulated lauric acid is improved.
Fig. 5a is a graph of heat absorption performance and fig. 5b is a graph of heat release performance.
As shown in fig. 6, a graph of the Differential Scanning Calorimetry (DSC) performance of pure Lauric Acid (LA), the polydopamine modified populus catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 1 (LA @ PCP 8:2), and the polydopamine modified populus catkin carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 2 (LA @ PCP 9: 1).
As shown in table 1, the Differential Scanning Calorimetry (DSC) performance diagram data of pure lauric acid, the polydopamine modified populus carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid in example 1, and the polydopamine modified populus carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid in example 2 are analyzed.
TABLE 1
As shown in Table 1, the melting phase transition enthalpy of pure Lauric Acid (LA) is 195.6J/g, while the melting phase transition enthalpy of the composite phase change material (LA @ PCP 8:2) in example 1, in which the mass ratio of polydopamine-modified Populus catkin carbon sheet to polyvinyl alcohol is 8:2, is 172.5J/g, and the encapsulation rate can be calculated to be 88.1% through a formula, which has a higher encapsulation rate than that of the existing phase change material.
As shown in fig. 8, the thermal conductivity of the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid is obviously improved, the thermal conductivity of the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 1 (LA @ PCP 8:2) and the polydopamine modified poplar seed carbon sheet/polyvinyl alcohol composite phase change material encapsulating lauric acid in example 2 (LA @ PCP 9:1) are respectively 0.325W/m.k and 0.373W/m.k, and compared with pure lauric acid (0.246W/m.k), the thermal conductivity is respectively improved by 32.1% and 51.6%.
Example 3
The preparation method of the composite phase-change material for encapsulating lauric acid comprises the following steps:
1) cleaning the collected poplar catkins with deionized water and absolute ethyl alcohol for multiple times, and drying the poplar catkins in a drying oven at 70 ℃ for 18 hours to obtain dried poplar catkins;
2) putting the dried poplar catkins into a tubular furnace, and annealing for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed poplar catkins carbon tube; the heating rate is 5 ℃/min;
3) carrying out ultrasonic crushing treatment on the annealed poplar carbon tubes in absolute ethyl alcohol for 6 hours, and drying to obtain poplar carbon sheets;
4) weighing 1.22114g of tris (hydroxymethyl) aminomethane reagent, dissolving in 980mL of deionized water, adjusting the pH value to 8.5 by using 1mol/L hydrochloric acid prepared in advance (real-time measurement by using a pH meter), transferring to a 1000mL volumetric flask, and fixing the volume by using deionized water to obtain tris-HCl buffer solution with the pH value of 8.5;
5) taking 0.5g of poplar catkin carbon sheet obtained in the step 3), putting the poplar catkin carbon sheet into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse the poplar catkin carbon sheet, then adding 2g of dopamine hydrochloride into the poplar catkin carbon sheet, and violently stirring for 24h in an open mode, centrifuging and drying to obtain a polydopamine modified poplar catkin carbon sheet;
6) adding 0.06g of polyvinyl alcohol solid into 6mL of water, heating the mixture in an oil bath at 95 ℃ until the mixture is molten, and then cooling the mixture to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) adding 0.24g of the polydopamine modified poplar catkin carbon sheet obtained in the step 5) into the polyvinyl alcohol aqueous solution (10g/L) obtained in the step 6), stirring at room temperature for 24 hours, pouring into a mold, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting the lauric acid in water bath at 50 ℃, then placing the aerogel with the mutually communicated three-dimensional porous structure, and automatically completing encapsulation of the lauric acid in a few minutes by the aerogel with the mutually communicated three-dimensional porous structure to obtain the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating the lauric acid.
Example 4
The preparation method of the composite phase-change material for encapsulating lauric acid comprises the following steps:
1) cleaning the collected poplar catkins with deionized water and absolute ethyl alcohol for multiple times, and drying the poplar catkins in a drying oven at 70 ℃ for 18 hours to obtain dried poplar catkins;
2) putting the dried poplar catkins into a tubular furnace, and annealing for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed poplar catkins carbon tube; the heating rate is 5 ℃/min;
3) carrying out ultrasonic crushing treatment on the annealed poplar carbon tubes in absolute ethyl alcohol for 6 hours, and drying to obtain poplar carbon sheets;
4) weighing 1.22114g of tris (hydroxymethyl) aminomethane reagent, dissolving in 980mL of deionized water, adjusting the pH value to 8.5 by using 1mol/L hydrochloric acid prepared in advance (real-time measurement by using a pH meter), transferring to a 1000mL volumetric flask, and fixing the volume by using deionized water to obtain tris-HCl buffer solution with the pH value of 8.5;
5) taking 0.5g of poplar catkin carbon sheet obtained in the step 3), putting the poplar catkin carbon sheet into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse the poplar catkin carbon sheet, then adding 2g of dopamine hydrochloride into the poplar catkin carbon sheet, and violently stirring for 24h in an open mode, centrifuging and drying to obtain a polydopamine modified poplar catkin carbon sheet;
6) adding 0.045g of polyvinyl alcohol solid into 4.5mL of water, heating the mixture in an oil bath at 95 ℃ until the mixture is molten, and then cooling the mixture to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) adding 0.255g of the polydopamine modified poplar catkin carbon sheet obtained in the step 5) into the polyvinyl alcohol aqueous solution (10g/L) obtained in the step 6), stirring at room temperature for 24 hours, pouring into a mold, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting the lauric acid in water bath at 50 ℃, then placing the aerogel with the mutually communicated three-dimensional porous structure, and automatically completing encapsulation of the lauric acid in a few minutes by the aerogel with the mutually communicated three-dimensional porous structure to obtain the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating the lauric acid.
The technical solution of the present invention is not limited to the limitations of the above specific embodiments, and all technical modifications made according to the technical solution of the present invention fall within the protection scope of the present invention.
Claims (8)
1. A composite phase change material for encapsulating lauric acid is characterized in that: the composite phase change material comprises aerogel which is formed by crosslinking and has a three-dimensional porous structure which is communicated with each other, and lauric acid which is packaged in the aerogel which has the three-dimensional porous structure which is communicated with each other;
the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking poplar catkin carbon sheets under the action of a crosslinking agent;
the cross-linking agent is polyvinyl alcohol aqueous solution.
2. The composite phase change material for encapsulating lauric acid according to claim 1, wherein: the poplar catkin carbon sheet is a polydopamine modified poplar catkin carbon sheet.
3. The composite phase change material for encapsulating lauric acid according to claim 2, wherein: the concentration of the polyvinyl alcohol aqueous solution is 5 g/L-20 g/L.
4. The composite phase change material for encapsulating lauric acid according to claim 3, wherein: the mass ratio of the polydopamine modified poplar catkin carbon sheets to the polyvinyl alcohol is 5-9: 1-5.
5. The composite phase change material for encapsulating lauric acid according to claim 4, wherein: the lauric acid is automatically encapsulated in the aerogel having three-dimensional pore-like structures which are communicated with each other.
6. The method for preparing a composite phase change material encapsulating lauric acid according to any one of claims 1 to 5, wherein: the method comprises the following steps:
s1, cleaning and drying the poplar catkins to obtain dried poplar catkins;
s2, annealing the dried poplar catkins for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed poplar catkins carbon tube;
s3, carrying out ultrasonic crushing treatment on the annealed poplar carbon tube in absolute ethyl alcohol, and drying after the treatment to obtain a poplar carbon sheet;
s4, dispersing the poplar catkin carbon sheets in tris-HCl buffer solution, adding dopamine hydrochloride, carrying out open stirring, centrifuging and drying to obtain polydopamine modified poplar catkin carbon sheets;
s5, adding the poly-dopamine modified poplar catkin carbon sheet into a polyvinyl alcohol aqueous solution, stirring at room temperature, pouring into a mold, freezing for 2 hours in a refrigerator, and then freeze-drying to obtain aerogel with mutually communicated three-dimensional porous structures;
s6, placing lauric acid in a beaker, heating and melting in water bath at 50 ℃, then placing the aerogel with the three-dimensional porous structures which are communicated with each other, and automatically encapsulating the lauric acid by the aerogel with the three-dimensional porous structures which are communicated with each other to obtain the polydopamine modified poplar catkin carbon sheet/polyvinyl alcohol composite phase change material for encapsulating the lauric acid.
7. The method for preparing the composite phase-change material for encapsulating lauric acid according to claim 6, wherein:
in the step S4, the pH value of the tris-HCl buffer solution is 8.5, and the volume ratio of the mass of the poplar catkin carbon tablets to the tris-HCl buffer solution is 1g:200 mL-400 mL; the mass ratio of the poplar catkin carbon sheets to the dopamine hydrochloride is 1: 4; the stirring time was 24 h.
8. The method for preparing the composite phase-change material for encapsulating lauric acid according to claim 7, wherein:
in the step S5, the concentration of the polyvinyl alcohol aqueous solution is 5 g/L-20 g/L; the mass ratio of the poly-dopamine modified poplar catkin carbon sheets to the polyvinyl alcohol is 5-9: 1-5.
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