CN116376520B - Preparation method of carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase change material - Google Patents
Preparation method of carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase change material Download PDFInfo
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- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 239000012782 phase change material Substances 0.000 title claims abstract description 66
- 239000002131 composite material Substances 0.000 title claims abstract description 48
- 229920001661 Chitosan Polymers 0.000 title claims abstract description 42
- 125000002057 carboxymethyl group Chemical group [H]OC(=O)C([H])([H])[*] 0.000 title claims abstract description 42
- 239000004964 aerogel Substances 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 36
- 229910052582 BN Inorganic materials 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 20
- 239000002135 nanosheet Substances 0.000 claims description 42
- 229920001223 polyethylene glycol Polymers 0.000 claims description 36
- 229920001690 polydopamine Polymers 0.000 claims description 31
- 239000002202 Polyethylene glycol Substances 0.000 claims description 25
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 24
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 claims description 22
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- 239000007864 aqueous solution Substances 0.000 claims description 15
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 12
- JQWHASGSAFIOCM-UHFFFAOYSA-M sodium periodate Chemical compound [Na+].[O-]I(=O)(=O)=O JQWHASGSAFIOCM-UHFFFAOYSA-M 0.000 claims description 12
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000004108 freeze drying Methods 0.000 claims description 7
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- CTENFNNZBMHDDG-UHFFFAOYSA-N Dopamine hydrochloride Chemical compound Cl.NCCC1=CC=C(O)C(O)=C1 CTENFNNZBMHDDG-UHFFFAOYSA-N 0.000 claims description 5
- 239000007983 Tris buffer Substances 0.000 claims description 5
- 229960001149 dopamine hydrochloride Drugs 0.000 claims description 5
- 230000001590 oxidative effect Effects 0.000 claims description 5
- LENZDBCJOHFCAS-UHFFFAOYSA-N tris Chemical compound OCC(N)(CO)CO LENZDBCJOHFCAS-UHFFFAOYSA-N 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 4
- 229910021641 deionized water Inorganic materials 0.000 claims description 4
- 230000001376 precipitating effect Effects 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 4
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- 238000005406 washing Methods 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 10
- 230000000052 comparative effect Effects 0.000 description 14
- 239000000047 product Substances 0.000 description 11
- 239000000463 material Substances 0.000 description 9
- 239000011148 porous material Substances 0.000 description 8
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
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- C09K5/06—Materials undergoing a change of physical state when used the change of state being from liquid to solid or vice versa
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Abstract
The invention discloses a preparation method of a carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material, which is used for solving the problems of low thermal conductivity of the phase-change material and leakage in the phase-change process.
Description
Technical Field
The invention belongs to the technical field of phase change materials, and relates to a preparation method of a carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase change material.
Background
The heat energy still plays a very important role in human life, the utilization of renewable energy is still quite limited at present, a large amount of heat is dissipated into the environment in the conversion process and is wasted, and the energy storage technology can solve the imbalance of energy in time and space and improve the utilization efficiency. Heat storage technologies are largely divided into sensible heat storage, latent heat storage, thermochemical reactions, etc., with phase change material storage (latent heat storage) being considered as the most promising technological route. The phase change material may undergo a transition from a solid to a liquid or other state at a temperature, and absorbs or emits a certain amount of heat during the transition. The organic solid-liquid phase change material, such as polyethylene glycol and the like, has stable chemical properties, good circularity, proper phase change temperature, no phase separation behavior and the like, and has wide application prospect. In recent years, organic solid-liquid phase change materials become a research focus of people, and the problems of low heat conductivity and leakage in the phase change process are solved.
A phase change material is a functional material capable of reversibly achieving latent heat storage and release during isothermal phase change. Compared with the pure phase change material, the composite phase change material has the remarkable characteristics of higher heat storage performance, heat transport performance, physical and chemical stability, chemical compatibility, energy conversion performance, advancement and the like. To date, several strategies for preparing composite phase change materials have been proposed. These preparation strategies mainly involve infiltration of the phase change material into the cavities of the porous material, or encapsulation thereof in microcapsules. Infiltration of phase change materials into the cavities of porous materials to produce shape stable composite phase change materials is currently the most widely used method. Compared with a micro/nano capsule method, the porous carrier adsorption method for preparing the composite phase-change material has the advantages of simple process, high energy storage density and excellent comprehensive performance, and can solve the problems of low heat conductivity and leakage in the phase-change process of the traditional phase-change material.
The boron nitride nano-sheet has a structure similar to graphite, has excellent thermal conductivity, oxidation resistance and corrosion resistance, and remarkable dielectric property, and has great application potential in improving thermal conductivity. How to take advantage of and modify the advantages of the phase change material to prepare the phase change material is a hot spot subject of research by extensive researchers.
Disclosure of Invention
The invention aims to provide a preparation method of a carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material, which aims to solve the problems of low thermal conductivity of the phase-change material and leakage in the phase-change process.
The technical scheme of the invention is as follows:
the preparation method of the carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material is characterized by sequentially carrying out the following steps:
s1, preparation of polydopamine modified boron nitride nanosheets
Dispersing the boron nitride nano-sheets into a mixed solution of Tris buffer solution and ethanol to form a boron nitride nano-sheet dispersion liquid, adding dopamine hydrochloride into the dispersion liquid according to the mass ratio of the boron nitride nano-sheets to the dopamine hydrochloride of 1.4-1.2, stirring for 10 hours at normal temperature, centrifuging, washing and drying to obtain polydopamine modified boron nitride nano-sheets;
s2, preparation of oxidized sodium alginate
Preparing sodium alginate into an aqueous solution with the mass concentration of 2.5 and wt percent, adding sodium periodate, oxidizing for 24 hours in a dark place, adding glycol and sodium chloride powder into the solution to terminate the reaction, precipitating with ethanol, filtering, dissolving the precipitate with deionized water, precipitating with ethanol again, filtering, repeating the steps for 3 times, and vacuum drying at 40 ℃ to obtain oxidized sodium alginate;
s3, preparation of composite phase change material
Preparing carboxymethyl chitosan into an aqueous solution with the mass concentration of 4wt%, adding polydopamine modified boron nitride nanosheets into the aqueous solution, uniformly mixing, adding the aqueous solution prepared by oxidizing sodium alginate obtained in the step S2, stirring for 0.5h, obtaining a high heat conduction porous skeleton through a sol-gel and freeze drying method, and vacuum impregnating polyethylene glycol melt to obtain the composite phase change material.
As a limitation of the present invention:
in step S1, the volume ratio of the Tris buffer solution to the ethanol in the mixed solution is 3:1.
And (II) in the step S1, the concentration of the boron nitride nano-sheet dispersion liquid is 5g/L.
In the step S2, the mass ratio of the sodium alginate to the sodium periodate to the ethylene glycol to the sodium chloride is 2:3:4:1.
in the invention, the proportions of sodium alginate, sodium periodate, ethylene glycol and sodium chloride are important, which influence the oxidation degree of oxidized sodium alginate, and further influence the crosslinking degree of carboxymethyl chitosan and the mechanical strength of aerogel.
In the fourth step S3, the mass ratio of the carboxymethyl chitosan, the oxidized sodium alginate and the polydopamine modified boron nitride nanosheets is 4:3:10.
in the invention, the proportion of carboxymethyl chitosan, oxidized sodium alginate and polydopamine modified boron nitride nanosheets is important, and influences the cross-linked structure, pore morphology and structure of the aerogel framework, and further influences the mechanical property, heat conducting property and loading rate of the phase change material of the aerogel.
And (fifth) in the step S3, the temperature of the freeze drying is-40 ℃ and the time is 24-72h.
During freeze-drying, migration and volatilization of water molecules occurs, which is the process of pore structure formation of the aerogel, which affects the mechanical strength, permeability and loading capacity of the phase change material of the aerogel.
In step S3, the vacuum impregnation temperature is 100 ℃ and the vacuum degree is 0.001MPa.
According to the invention, the loading amount of the phase-change material polyethylene glycol in the aerogel is affected by the vacuum impregnation temperature, when the temperature is higher than 100 ℃, the phase-change material polyethylene glycol has good fluidity, the phase-change material polyethylene glycol can fully infiltrate the pore canal of the aerogel, when the temperature is lower than 100 ℃, the fluidity of polyethylene glycol melt is poor, the aerogel pore canal cannot be fully infiltrated, and more cavities and bubbles are formed in the composite phase-change material.
The invention is also limited in that in step S3, the thermal conductivity of the composite phase change material is 0.5-1.2W/mK.
The above method of the present invention as a whole is closely related to each other, and affects the performance of the final product. According to the invention, polydopamine modified boron nitride nanosheets are used as a matrix, soluble carboxymethyl chitosan is used as a reinforcing material, and oxidized sodium alginate is used as a cross-linking agent, so that the strength and flexibility of the boron nitride aerogel can be improved after reaction; the polydopamine is adhered to the surface of the boron nitride nanosheets, so that interaction between the boron nitride nanosheets is improved, a heat conducting network is formed, in addition, the polydopamine can also serve as an interface layer to reduce thermal resistance between the filler and the epoxy matrix, and meanwhile, the carboxymethyl chitosan contains a large amount of amino groups and hydroxyl groups, so that hydrogen bonds can be formed with the polydopamine modified boron nitride nanosheets, and the polydopamine can be strongly bonded together. In the process, a small amount of carboxymethyl chitosan is used for dispersing the boron nitride nano-sheets, and the boron nitride nano-sheets are bonded to stabilize the structure. According to the invention, the microstructure of aerogel can be regulated by changing the content of the boron nitride nanosheets, a sol-gel method and a freeze drying technology are adopted to prepare the nano boron nitride composite high-heat-conductivity skeleton, and finally polyethylene glycol is encapsulated in the skeleton by a vacuum impregnation method to obtain the composite phase change material, so that the leakage problem in the phase change process is solved.
By adopting the technical scheme, the invention has the following advantages:
1. the invention has the advantages of wide sources of raw materials, good biocompatibility, no toxicity, degradability and low cost, and is suitable for industrialized popularization and application.
2. The preparation method is simple and mild, the process is easy to control, the environment is friendly, the loading rate of the phase change material in the prepared product is high, and the heat storage and shaping effects and the mechanical strength are good.
3. The thermal conductivity coefficient of the finally obtained composite phase-change material is 0.5-1.2W/mK, and compared with the existing phase-change material, the thermal conductivity is obviously improved.
The preparation method is suitable for preparing the carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase change material.
The following detailed description of the invention refers to the accompanying drawings.
Drawings
Fig. 1 is a scanning electron microscope image of a boron nitride nanosheet before and after polydopamine modification in example 1, wherein: (a) -boron nitride nanoplatelets, (b) -polydopamine modified boron nitride nanoplatelets;
FIG. 2 is a graph of the polyethylene glycol filled aerogel of example 1 before and after filling, wherein (a) -COBP, (b) -COBP/PEG;
FIG. 3 is COBP-B 3 、COBP-B 5 、COBP-B 7 Pure polyethylene glycol infrared spectrogram;
FIG. 4 is a pure polyethylene glycol and COBP-B 5 、COBP-B 3 、COBP-B 7 A thermogravimetric analysis graph of (a);
FIG. 5 is a diagram of pure polyethylene glycol and COBP-B 5 、COBP-B 3 、COBP-B 7 A differential scanning calorimeter graph of temperature reduction and temperature increase, wherein: (a) cooling and (b) heating;
FIG. 6 is COBP-B 5 、COBP-B 3 、COBP-B 7 A differential scanning calorimeter graph before and after 50 times of cold and hot cycles of 0 ℃ to 80 ℃;
FIG. 7 is a graph showing the compressive stress values of carboxymethyl chitosan reinforced nano boron nitride aerogel at a compressive strain of 80%.
Detailed Description
In the following examples, the reagents described were all commercially available unless otherwise specified, and the following experimental methods and detection methods were all employed according to the conventional experimental methods and detection methods unless otherwise specified.
Example 1 preparation method of carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material
The preparation method of the carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material comprises the following steps of:
s1, dispersing 1 g boron nitride nano-sheets into a mixed solution formed by 150 mL of Tris buffer (10 mM, pH=8.5) and 50 mL ethanol, adding 0.8 g dopamine hydrochloride into the mixed solution, stirring at room temperature for reaction for 10h, washing with ethanol and deionized water after the reaction is finished, and vacuum drying at 40 ℃ to obtain dark gray polydopamine modified boron nitride nano-sheets;
s2, preparing 1 g sodium alginate into an aqueous solution with the mass concentration of 2.5wt%, adding 1.5 g sodium periodate into the aqueous solution, oxidizing the aqueous solution in a dark place to obtain 24. 24h, adding 2g of ethylene glycol and 0.5g of sodium chloride powder to terminate the reaction 1 h after the reaction is finished, adding 40 mL ethanol to precipitate, filtering, dissolving the precipitate with deionized water, separating out with ethanol again, filtering, repeating the steps for 3 times, and vacuum drying at 40 ℃ to obtain a light yellow product which is oxidized sodium alginate;
s3, preparing carboxymethyl chitosan into a 4wt% aqueous solution, preparing oxidized sodium alginate prepared in the step S2 into a 6 wt% aqueous solution, uniformly dispersing polydopamine modified boron nitride nano-sheets into the carboxymethyl chitosan aqueous solution, wherein the mass ratio of the carboxymethyl chitosan to the polydopamine modified boron nitride nano-sheets is 2:5, a step of; under the condition of room temperature, adding the oxidized sodium alginate aqueous solution into the mixed solution of carboxymethyl chitosan and polydopamine modified boron nitride nanosheets, and stirring and reacting for 0.5h, wherein the mass ratio of carboxymethyl chitosan to oxidized sodium alginate is 4:3, freeze-drying at-40 ℃ for 24 hours by a sol-gel method to obtain a porous skeleton with high heat conductivity, and vacuum impregnating polyethylene glycol melt at 100 ℃ and a vacuum degree of 0.001MPa to obtain the composite phase change material.
The nanometer boron nitride aerogel composite material obtained by the invention is gray block and is marked as COBP-B 5 And performing subsequent performance comparison tests, wherein the mass fraction of polyethylene glycol is 86%, the heat conductivity coefficient is 1.0W/mK, and the heat conductivity is improved.
Fig. 1 is a scanning electron microscope image of boron nitride nanosheets before and after polydopamine modification in this embodiment, from which it can be derived: the surface of the boron nitride nano sheet after the polydopamine is modified becomes coarser, the aggregation condition of sheet layers is reduced, and the polydopamine is successfully attached to the surface of the boron nitride nano sheet, so that polydopamine is combined with the hexagonal structure of BNNS (boron oxide nano sheet) through pi-pi bonds and Van der Waals force, and the polydopamine and the BNNS (boron oxide nano sheet) have stronger interaction, so that the polydopamine modified boron nitride nano sheet has good stability and is not easy to fall off.
FIG. 2 is a diagram showing the structure before and after filling the aerogel with polyethylene glycol according to the present example, wherein (a) is the product before filling with polyethylene glycol, denoted as COBP; (b) The figure shows the product after polyethylene glycol filling, designated COBP/PEG. From the figures it can be derived that: the aerogel is a porous structure formed by connecting thin walls with each other before polyethylene glycol is filled, the pore structure of the framework is uniformly filled with phase change materials, gaps and cracks are fewer, and the filling of the polyethylene glycol is proved to be more sufficient, no obvious phase separation phenomenon exists between the PEG and the heat conduction framework, and the PEG and the heat conduction framework have good compatibility.
The material prepared in this example was tested to have a compressive stress of 8.55MPa at a compressive strain of 80%, as shown in fig. 7 (example 1 in the drawing represents the material of this example 1).
Examples 2-4 preparation method of carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material
Examples 2-4 are respectively a preparation method of carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material, and the preparation process is similar to example 1, except that: the technical parameters in the preparation process are different, and the specific table is shown below.
Comparative example one
In order to explore the influence of the mass ratio of carboxymethyl chitosan and polydopamine modified boron nitride nanosheets on the final product and its properties, the following experiments were performed.
Group a: the preparation process of the composite phase change material is the same as in example 1, except that: the mass ratio of the carboxymethyl chitosan to the polydopamine modified boron nitride nanosheets is 2:3, and the prepared product is named as COBP-B 3 。
Group b: the preparation process of the composite phase change material is the same as in example 1, except that: the mass ratio of the carboxymethyl chitosan to the polydopamine modified boron nitride nanosheets is 2:7, and the prepared product is named as COBP-B 7 。
The products prepared in the group a and the group b are subjected to performance test, and specific test results are as follows.
Fig. 3 shows the infrared spectra of the materials prepared in the example 1 and the comparative examples a and b and pure polyethylene glycol, and the infrared spectra can be obtained from the figures: the characteristic peak of the composite phase change material contains the characteristic peak of pure PEG, the position and the intensity of the peak are not obviously changed, and no new absorption peak is generated. This suggests that the thermally conductive backbone is impregnated with PEG, and that there is only a physical interaction between the backbone and PEG, and no chemical interaction, and no cleavage and formation of chemical bonds during impregnation.
FIG. 4 is a thermogravimetric analysis of the material prepared in example 1, comparative examples, groups a and b, and pure polyethylene glycol, from which it can be derived: the thermal decomposition of the pure polyethylene glycol chain segment starts at about 350 ℃, when the temperature reaches about 450 ℃, the thermal weight loss of PEG is almost close to 100%, the composite phase-change material has almost no thermal weight loss below 200 ℃, the composite phase-change material can be used within the phase-change temperature, and the filling rate can be seen to reach more than 80%.
FIG. 5 shows differential scanning calorimetric curves of the materials prepared in example 1, comparative examples a and b, and pure polyethylene glycol, from which: the pure polyethylene glycol and the composite phase-change material are both a peak, and after vacuum impregnation, the phase-change characteristic of the PEG is well reserved in a 3D cross-linked network of the heat-conducting framework, so that the novel composite phase-change material is endowed with excellent phase-change behavior.
FIG. 6 is a graph showing the differential scanning calorimetric curves of the material prepared in the comparative examples a and b and the pure polyethylene glycol cycled 1 time and 50 times, from which it can be derived: the position of the contrast peak is not changed greatly after 1 time and 50 times of circulation, and the area change after integration is not changed greatly, because PEG is adsorbed in the pores of the heat conducting framework, the flow of the melted PEG is limited, and the stability of the composite phase change material in cold and hot circulation is improved.
Comparative example two
Comparative example A preparation method of carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material
The comparative example is a preparation method of a carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material, and the preparation process is similar to that of example 1, and the difference is that: when the aerogel is prepared, the boron nitride nanosheets or polydopamine modified boron nitride nanosheets are not added. The resulting product was tested and, as is evident from FIG. 7, the compressive stress at 80% compressive strain was only 2.29MPa.
Comparative example B preparation method of carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material
The comparative example is a preparation method of a carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material, and the preparation process is similar to that of example 1, and the difference is that: no carboxymethyl chitosan was added to prepare the aerogel. When the obtained product is tested, as shown in fig. 7, it is obvious that the compressive stress is only 3.74MPa when the compressive strain is 80%.
Comparative example C preparation method of carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material
The comparative example is a preparation method of a carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material, and the preparation process is similar to that of example 1, and the difference is that: no modification of nano boron nitride with polydopamine was performed. The prepared product is tested, and the result is shown in fig. 7, and it can be obviously seen that the compressive stress is only 6.53MPa when the compressive strain is 80%, and meanwhile, the thermal conductivity of the composite phase change material is only 0.273w/mK due to poor dispersibility of the nano boron nitride.
Comparative example D preparation method of carboxymethyl chitosan reinforced nanometer boron nitride aerogel composite phase-change material
The comparative example is a preparation method of a carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material, and the preparation process is similar to that of example 1, and the difference is that: oxidized sodium alginate was not used as a cross-linking agent. The resulting product was tested and, as is evident from FIG. 7, the compressive stress at 80% compressive strain was only 3.47MPa.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (4)
1. The preparation method of the carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material is characterized by sequentially carrying out the following steps:
s1, preparation of polydopamine modified boron nitride nanosheets
Dispersing the boron nitride nano-sheets into a mixed solution of Tris buffer solution and ethanol to form a boron nitride nano-sheet dispersion liquid, adding dopamine hydrochloride into the dispersion liquid according to the mass ratio of the boron nitride nano-sheets to the dopamine hydrochloride of 1.4-1.2, stirring for 10 hours at normal temperature, centrifuging, washing and drying to obtain polydopamine modified boron nitride nano-sheets;
the volume ratio of Tris buffer solution to ethanol in the mixed solution is 3:1;
the concentration of the boron nitride nano-sheet dispersion liquid is 5g/L;
s2, preparation of oxidized sodium alginate
Preparing sodium alginate into an aqueous solution with the mass concentration of 2.5wt%, adding sodium periodate, oxidizing for 24 hours in a dark place, adding glycol and sodium chloride powder into the solution to terminate the reaction, precipitating with ethanol, filtering, dissolving the precipitate with deionized water, precipitating with ethanol again, filtering, repeating the steps for 3 times, and vacuum drying at 40 ℃ to obtain oxidized sodium alginate;
the mass ratio of the sodium alginate to the sodium periodate to the ethylene glycol to the sodium chloride is 2:3:4:1, a step of;
s3, preparation of composite phase change material
Preparing carboxymethyl chitosan into an aqueous solution with the mass concentration of 4wt%, adding polydopamine modified boron nitride nanosheets into the aqueous solution, uniformly mixing, adding the aqueous solution prepared by oxidizing sodium alginate obtained in the step S2, stirring for 0.5h, obtaining a high heat conduction porous skeleton through a sol-gel and freeze drying method, and vacuum impregnating polyethylene glycol melt to obtain a composite phase change material;
the mass ratio of the carboxymethyl chitosan, oxidized sodium alginate and polydopamine modified boron nitride nanosheets is 4:3:10.
2. the method for preparing the carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material according to claim 1, wherein in the step S3, the freeze-drying temperature is-40 ℃ and the time is 24-72h.
3. The method for preparing the carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase-change material according to claim 1, wherein in the step S3, the vacuum impregnation temperature is 100 ℃, and the vacuum degree is 0.001MPa.
4. The method for preparing a carboxymethyl chitosan reinforced nano boron nitride aerogel composite phase change material according to any one of claims 1 to 3, wherein in step S3, the thermal conductivity of the composite phase change material is 0.5 to 1.2W/mK.
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