CN110655910A - A kind of preparation method of graphene aerogel phase change energy storage material - Google Patents

Abstract

The invention belongs to the field of nanoporous materials, and relates to a preparation method of a graphene aerogel phase-change energy storage material. By mixing graphene oxide powder with a solvent, then adding phase change material, hydrothermal reduction method is used to obtain wet gel, and finally washing, drying and other processes are carried out to finally prepare graphene aerogel as the structural skeleton, and the phase change material is evenly distributed phase change energy storage materials. The invention has the advantages of simple preparation process, good anti-leakage, high latent heat and high thermal conductivity, etc., and is easy to realize large-scale production.

Description

A kind of preparation method of graphene aerogel phase change energy storage material

technical field

The invention relates to a preparation method of a novel graphene aerogel phase change energy storage material, in particular to a preparation method of a graphene aerogel phase change energy storage material, and belongs to the technical field of nanoporous materials and phase change energy storage.

Background technique

With the rapid development of society and economy, people's demand for heat energy in heating and thermal insulation, food drying, domestic hot water and other fields is increasing. However, the excess heat in the life and production process is often regarded as waste heat. external environment. As one of the basic national policies of my country, energy conservation and environmental protection play an important role in social development and progress, and it is particularly important to improve the utilization rate of thermal energy.

Phase-change energy storage is currently the most popular energy storage method, that is, phase-change materials still have extremely high latent heat of phase-change and a wide range of phase-change temperature selection even with small temperature changes. When the temperature rises to the vicinity of the melting point of the phase change material, the phase change material can absorb heat and undergo a solid-liquid phase transition to achieve the effect of energy storage and reduce the surrounding temperature. Phase change energy storage materials can be used in aerospace, construction, clothing, refrigeration equipment, military, communications, electricity and other fields, and can realize energy storage, building energy conservation and temperature regulation. However, there are three main problems in the use of phase change materials: the degradation of thermophysical properties during the cycle, the easy leakage of the phase change material from the matrix, and the effect of the phase change material on the matrix material. Therefore, it is urgent to find a porous matrix that does not react with the phase change material and can well wrap the phase change material and stabilize its phase change enthalpy.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a graphene aerogel phase change energy storage material in order to improve the deficiencies of the prior art, to improve the current low utilization rate of thermal energy and overcome some technical problems.

The technical solution adopted in the present invention is: a preparation method of a graphene aerogel phase-change energy storage material, the specific steps of which are as follows:

(1) stirring the graphene oxide powder and the solvent to form a uniform graphene oxide solution;

(2) adding a phase change material to the graphene oxide solution formed in step (1), and stirring for 1 to 10 min;

(3) pouring the mixed system formed in step (2) into a polytetrafluoroethylene hydrothermal reactor, and reacting at a temperature of 90 to 240 ° C for 5 to 20 hours to obtain a graphene phase change energy storage wet gel;

(4) replacing the wet gel obtained in step (3) with a solvent;

(5) drying the wet gel obtained in step (4) to finally obtain a graphene aerogel phase change energy storage material.

Wherein, the mass ratio of graphene oxide to the solvent in step (1) is (1-20):1000, and the mass ratio of the phase change material added in step (2) to graphene oxide is (10-100):1.

Preferably, the solvent described in step (1) and step (4) is one of deionized water, ethanol, acetone, isopropanol or sec-butanol or a mixture thereof.

Preferably, the phase change material described in step (2) is any one or a combination of two or more of paraffin, polyethylene glycol, fatty acid, aromatic hydrocarbon, polyolefin, polyamide or polyol.

Preferably, in the step (4), the replacement times are 3 to 9 times, and the standing time is 8 to 24 hours each time.

Preferably, the drying treatment described in the step (5) is carbon dioxide supercritical drying and freeze drying; carbon dioxide supercritical drying uses carbon dioxide as the drying medium, the reaction temperature is 50-70 ° C, the pressure in the autoclave is 8-12 MPa, and the gas is released. The rate is 5~20L/min, and the drying time is 8~20h; for freeze drying, the pre-freezing temperature is -20~-80°C, and the freezing time is 5~48h, and then it is vacuumized and dried for 12~36h.

The prepared graphene aerogel phase change energy storage material includes graphene aerogel and phase change material, and the graphene aerogel is hydrothermally reduced by graphene oxide (GO) sheet to rGO sheet , and then assembled into a three-dimensional spatial network structure by two-dimensional rGO, and the phase change material is uniformly distributed in the three-dimensional spatial network structure.

The above-mentioned graphene aerogel phase change energy storage material can be used in aerospace, construction, clothing, refrigeration equipment, military, communication, electric power and other fields, and can realize energy storage, building energy saving and temperature regulation.

Beneficial effects:

The method of the present invention and the graphene aerogel phase change energy storage material prepared by the method have the following characteristics:

(1) High latent heat and high thermal conductivity. As a stable carbon material, graphene does not have any chemical interaction with the phase change material, and only relies on the capillary force of graphene aerogel for phase change coating, so the phase change material can maintain its high enthalpy change characteristics, At the same time, the high thermal conductivity of graphene greatly improves the phase transition response rate.

(2) Good leakproofness. Mainly because the pore size of the graphene aerogel in the graphene aerogel phase change energy storage material is composed of micropore-mesopore-macropore hierarchical pores, which has excellent adsorption performance and can effectively prevent phase change materials. of melting leaks.

Description of drawings

Fig. 1 is the photo in kind of the graphene aerogel polyethylene glycol phase change energy storage material obtained by example 1;

Fig. 2 is the SEM image under different multiples of the graphene aerogel paraffin phase change energy storage material obtained by example 3;

Fig. 3 is the DSC curve before and after the cycle of the graphene aerogel palmitic acid phase change energy storage material obtained in Example 4.

Detailed ways

Example 1

The graphene oxide and deionized water are evenly mixed and stirred according to the mass ratio of 1:1000, then polyethylene glycol with a mass ratio of 10:1 to the graphene oxide is added, stirred for 1 min, and poured into the hydrothermal solution of polytetrafluoroethylene. The reaction kettle was kept at 90 °C for 20 hours, and the samples were taken out and replaced with deionized water for 3 times, each time for 24 hours, and then placed in the environment of -20 °C for 5 hours, and then vacuumized and dried for 12 hours to obtain The final graphene aerogel polyethylene glycol phase change energy storage material. The sample diagram is shown in Figure 1. It can be seen from the figure that the surface of the sample is relatively smooth, the overall color is displayed as the black of graphene aerogel, and the white polyethylene glycol phase change material is well filled in the graphene aerogel. The density of this sample is 0.16 g/cm ³ and the enthalpy of fusion is 127.6 J/g.

Example 2

Graphene oxide and ethanol are uniformly mixed and stirred according to the mass ratio of 20:1000, then add the stearic acid that is 100:1 with the mass ratio of graphene oxide, stir for 10min, pour into the hydrothermal reactor of polytetrafluoroethylene, Incubate at 240 °C for 5 hours, take out the sample and replace it with deionized water for 9 times, let stand for 8 hours each time, freeze at -80 °C for 48 hours, and vacuum dry for 36 hours to obtain the final graphene aerogel Stearic acid phase change energy storage material. The density of this sample was 0.36 g/cm ³ and the enthalpy of fusion was 346.7 J/g.

Example 3

Graphene oxide and acetone are uniformly mixed and stirred according to the mass ratio of 16:1000, then add the paraffin with a mass ratio of 50:1 to graphene oxide, stir for 10min, pour into the hydrothermal reaction kettle of polytetrafluoroethylene, at 240 Incubate at ℃ for 9 hours, take out the sample and replace it with ethanol 9 times, and let it stand for 8 hours each time. Then it was placed in a CO2 supercritical reactor, and dried for 8 hours in a high-pressure reactor with a reaction temperature of 70 °C, a pressure of 8 MPa, and a degassing rate of 5 L/min to obtain the final graphene aerogel paraffin phase transition. energy storage material. The density of the sample is 0.26g/cm ³ , and the SEM image is shown in Figure 2. The sheet-like network structure of the graphene aerogel can be clearly seen from the left image, and the paraffin phase change material can be seen from the right image. Filled into the framework of graphene aerogel; its melting enthalpy is 236.7J/g.

Example 4

Graphene oxide and isopropanol are evenly mixed and stirred according to the mass ratio of 7:1000, then palmitic acid with a mass ratio of 40:1 to graphene oxide is added, stirred for 10min, and poured into the hydrothermal reaction of polytetrafluoroethylene The kettle was kept at 90 °C for 13 hours, and the samples were taken out and replaced with ethanol for 3 times, each time standing for 12 hours. Then it was placed in a CO ₂ supercritical reactor, and dried for 20h in a high-pressure reactor with a reaction temperature of 50°C, a pressure of 12MPa, and a degassing rate of 20L/min, thereby obtaining the final graphene aerogel soft grease Acid phase change energy storage materials. The density of the sample is 0.21g/cm ³ , and the cyclic DSC curve of the melting and solidification process is shown in Figure 3. It can be seen from the figure that the melting enthalpy before the cycle test is 139.4J/g, and the solidification enthalpy is 175.7J/g; The melting enthalpy remained unchanged after the test at 139.4 J/g, while the solidification enthalpy decreased to 149.0 J/g.

Claims (5)

1. a preparation method of graphene aerogel phase change energy storage material, its concrete steps are as follows: (1) stirring the graphene oxide powder and the solvent to form a uniform graphene oxide solution; (2) adding a phase change material to the graphene oxide solution formed in step (1), and stirring for 1 to 10 min; (3) pouring the mixed system formed in step (2) into a polytetrafluoroethylene hydrothermal reactor, and reacting at a temperature of 90 to 240 ° C for 5 to 20 hours to obtain a graphene phase change energy storage wet gel; (4) replacing the wet gel obtained in step (3) with a solvent; (5) drying the wet gel obtained in step (4) to finally obtain a graphene aerogel phase change energy storage material. Wherein, the mass ratio of graphene oxide to the solvent in step (1) is (1-20):1000, and the mass ratio of the phase change material added in step (2) to graphene oxide is (10-100):1. 2. preparation method according to claim 1 is characterized in that the solvent described in step (1) and step (4) is a kind of in deionized water, ethanol, acetone, isopropanol or sec-butanol or a mixture thereof. 3. preparation method according to claim 1 is characterized in that the phase change material described in step (2) is in paraffin, polyethylene glycol, fatty acid, aromatic hydrocarbon, polyolefin, polyamide or polyhydric alcohol Any one or a combination of two or more. 4 . The preparation method according to claim 1 , wherein the replacement times in step (4) are 3 to 9 times, and the standing time is 8 to 24 hours each time. 5 . 5. preparation method according to claim 1 is characterized in that the drying process described in step (5) is carbon dioxide supercritical drying and freeze-drying; carbon dioxide supercritical drying takes carbon dioxide as drying medium, and the reaction temperature is 50～70 ℃ ℃, the pressure in the autoclave is 8～12MPa, the gas release rate is 5～20L/min, and the drying time is 8～20h; for freeze drying, the pre-freezing temperature is -20～-80℃, and the freezing time is 5～48h, Then it was vacuum-dried for 12-36 h.

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