CN107686719B - High-thermal-conductivity hydrated salt phase-change material and preparation method thereof - Google Patents
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Abstract
The invention relates to the technical field of phase-change materials, in particular to a high-heat-conductivity hydrated salt phase-change material and a preparation method thereof. The preparation method comprises the following steps: preparing a reduced graphene aqueous dispersion; and stirring and ultrasonically treating the reduced graphene aqueous dispersion and inorganic salt to obtain the high-thermal-conductivity hydrated salt phase-change material. The hydrous salt phase-change material has higher thermal conductivity and has smaller influence on properties such as enthalpy value and the like of the phase-change material. In addition, the preparation method has wide application range, and all inorganic hydrated salt phase change energy storage materials can prepare the phase change material with high heat conduction and less phase change enthalpy value reduction by reducing the graphene aqueous dispersion and the corresponding salts thereof.
Description
Technical Field
The invention relates to the technical field of phase-change materials, in particular to a high-heat-conductivity hydrated salt phase-change material and a preparation method thereof.
Background
Phase change materials refer to substances that change state of a substance with a change in temperature and provide latent heat. The process of the phase-change material for converting the physical property is called a phase-change process, the process is accompanied with the storage and the release of energy, the utilization rate of energy can be effectively improved, and the characteristic of the phase-change material gains higher attention for the phase-change material in the current society with more prominent energy problems.
The phase change material can be divided into an organic phase change material and an inorganic phase change material, and can also be divided into a hydrated salt phase change material and a waxy phase change material. The inorganic hydrous salt phase-change material is widely applied to multiple fields due to the advantages of large phase-change latent heat, low price, nonflammability, safety, no toxicity and the like, but the phase-change material has the defects of poor heat-conducting property, supercooling, poor system stability and the like in the phase-change process.
Chinese patent CN 101805591A discloses an inorganic hydrated salt expanded graphite composite phase change heat storage material and a preparation method thereof, the material takes 85-89 parts by mass of inorganic hydrated salt sodium acetate trihydrate as a heat storage matrix, 5.5-6.5 parts by mass of disodium hydrogen phosphate dodecahydrate as a nucleating agent, 2.5-3.5 parts by mass of carboxymethyl cellulose as a thickening agent, and 3-4.5 parts by mass of expanded graphite as a material with high heat conductivity coefficient to be mixed in an inorganic hydrated salt mixture. The material can solve the problems of supercooling, phase delamination and low heat conductivity coefficient in the heat storage process.
Chinese patent CN 105131909A discloses an inorganic composite high-heat-conductivity phase-change heat storage material and a preparation method thereof, wherein the heat storage material is prepared by compounding crystalline hydrated salt, high-molecular water-absorbing resin (SPA) and porous foamy copper, wherein the mass fraction of the crystalline hydrated salt accounts for 88.1%, the mass fraction of the high-molecular water-absorbing resin (SPA) accounts for 0.9%, the mass fraction of the porous foamy copper accounts for 11%, and the porosity of the porous foamy copper selected in the material is more than 98%. The material has the advantages of high heat absorption and release speed, large heat storage capacity and unchanged shape after phase change.
For phase change materials, thermal conductivity is one of the very important parameters, and determines how fast the material transfers heat. Slow thermal conductivity increases the temperature gradient in different parts of the material, increasing the time constant for heat transfer, and slowing the rate of heat transfer. Therefore, in order to overcome the disadvantages of poor thermal conductivity of inorganic hydrated salt phase change materials, the prior art (such as the above-mentioned patent publications) adds a large amount of additives, such as expanded graphite, graphite powder, etc., into the phase change material to improve the thermal conductivity. However, this method introduces a new problem that the addition of a large amount of such additives can increase the heat transfer and simultaneously cause a large decrease in other properties of the phase change material (such as enthalpy value of the phase change material), thereby reducing the heat storage performance of the phase change material. Therefore, there is a need for a hydrous salt phase change material to improve its thermal conductivity and reduce the influence on other properties of the phase change material.
Disclosure of Invention
In order to overcome the defects of the prior art, the inventor conducts diligent research, and finishes the invention after paying a great deal of creative labor and carrying out deep experimental exploration.
In a first aspect, the invention provides a preparation method of a high thermal conductivity hydrous salt phase change material, which comprises the following steps:
preparing a reduced graphene aqueous dispersion;
and stirring and ultrasonically treating the reduced graphene aqueous dispersion and inorganic salt to obtain the high-thermal-conductivity hydrated salt phase-change material.
Further, the reduced graphene aqueous dispersion is obtained by reducing a graphene oxide aqueous dispersion with a reducing agent.
Further, the step of preparing the reduced graphene aqueous dispersion is: preparing the graphene oxide aqueous dispersion by a hummers method; and stirring and dispersing the reducing agent and the graphene oxide aqueous dispersion, reacting at a constant temperature, and performing ultrasonic dispersion to obtain the reduced graphene aqueous dispersion.
The reduced graphene aqueous dispersion is prepared by the steps of preparing 2mg/m L-4 mg/m L of the graphene oxide aqueous dispersion, magnetically stirring the reducing agent and the graphene oxide aqueous dispersion at a mass ratio of 1-3.5:100 at 200-500 rpm for 10-60 min to uniformly disperse, reacting at 80-120 ℃ for 1-3 h, and ultrasonically dispersing for 10-60 min to obtain the reduced graphene aqueous dispersion.
Wherein the graphene oxide aqueous dispersion of 2mg/m L-4 mg/m L includes any value within this numerical range, for example, the graphene oxide aqueous dispersion is 2mg/m L, 2.2mg/m L, 2.5mg/m L, 2.8mg/m L, or 3mg/m L.
The mass ratio of the reducing agent to the graphene oxide aqueous dispersion is 1-3.5:100 inclusive, for example, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, or 3.5: 100.
Magnetically stirring at 200-500 rpm for 10-60 min for dispersion stirring, wherein the rotation speed is 200-500 rpm inclusive of any point value within the range of values, such as 200, 250, 300, 350, 400, 450, or 500 rpm; the stirring time of 10min-60min includes any point in the time range, for example, the stirring time is 10min, 20min, 25min, 30min, 40min, 50min or 60 min.
Carrying out reaction for 1-3 h at constant temperature of 80-120 ℃, and then carrying out ultrasonic dispersion for 10-60 min, wherein the constant temperature of 80-120 ℃ comprises any point value in the temperature range, such as constant temperature of 80 ℃, 85 ℃, 90 ℃, 100 ℃, 105 ℃, 110 ℃ or 120 ℃; reactions 1h to 3h include any point within the reaction time range, e.g., reactions 1h, 1.2h, 1.5h, 2h, 2.5h, or 3 h; the ultrasonic dispersion for 10min to 60min includes any point value in the time range, such as ultrasonic dispersion for 10min, 20min, 30min, 40min, 50min or 60 min.
Optionally, the reducing agent is selected from hydrazine hydrate, vitamin C, ethylenediamine, or sodium bisulfate.
Further, in the step of preparing the reduced graphene aqueous dispersion, a surfactant is added into a reaction system of the graphene oxide aqueous dispersion and the reducing agent, and the mass ratio of the surfactant to the graphene oxide aqueous dispersion is 10-25: 100.
Wherein the mass ratio of the surfactant to the aqueous graphene oxide dispersion is 10-25:100 inclusive, for example, 10:100, 15:100, 18:100, 20:100, 22:100, or 25: 100.
Optionally, the surfactant is selected from polyvinylpyrrolidone or sodium dodecylbenzenesulfonate.
Further, the preparation method comprises the steps of dispersing and diluting the reduced graphene aqueous dispersion by 1-6 times by using water after preparing the reduced graphene aqueous dispersion, carrying out ultrasonic dispersion for 10-60 min, and then stirring and carrying out ultrasonic treatment on the reduced graphene aqueous dispersion and the inorganic salt.
Further, the inorganic salt is one of calcium salt, potassium salt, sodium salt, magnesium salt, iron salt, zinc salt or aluminum salt.
Preferably, the inorganic salt is calcium chloride dihydrate.
Further, in the step of stirring and ultrasonically treating the reduced graphene aqueous dispersion and calcium chloride dihydrate, the mass ratio of the calcium chloride dihydrate to the diluted water in the reduced graphene aqueous dispersion is less than or equal to 2.044: 1; magnetically stirring at 200-500 rpm for 5-30 min, and ultrasonically dispersing for 10-60 min to obtain the reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase change material. The calcium chloride hexahydrate hydrated salt phase-change material with the stably dispersed reduced graphene is the high-thermal-conductivity hydrated salt phase-change material.
Wherein the mass ratio of the calcium chloride dihydrate to the water in the diluted reduced graphene aqueous dispersion is less than or equal to 2.044:1, including any value within the range of the ratio, for example, the mass ratio of the calcium chloride dihydrate to the diluted reduced graphene aqueous dispersion is 2.044:1, 2:1, 1.8:1, 1.5:1, 1.2:1, 1: 1.
Magnetically stirring at 200-500 rpm for 5-30 min, and ultrasonically dispersing for 10-60 min, wherein the rotation speed of 200-500 rpm includes any point value in the numerical range, such as 200, 250, 300, 350, 400, 450 or 500 rpm; the stirring time is 5min-30min including any point value in the time range, such as 5min, 10min, 15min, 20min, 25min, 30 min; the ultrasonic dispersion for 10min-60min includes any point value in the time range, such as ultrasonic dispersion for 10min, 20min, 25min, 30min, 40min, 50min or 60 min.
Further, the thermal conductivity of the reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase change material is 0.8W (m.K)-1-1.2W·(m·K)-1。
In a second aspect, the invention provides a high thermal conductivity hydrous salt phase change material, which is obtained by the preparation method.
Further, the reduced graphene aqueous dispersion is obtained by reducing a graphene oxide aqueous dispersion with a reducing agent.
Further, the step of preparing the reduced graphene aqueous dispersion is: preparing the graphene oxide aqueous dispersion by a hummers method; and stirring and dispersing the reducing agent and the graphene oxide aqueous dispersion, reacting at a constant temperature, and performing ultrasonic dispersion to obtain the reduced graphene aqueous dispersion.
The reduced graphene aqueous dispersion is prepared by the steps of preparing 2mg/m L-4 mg/m L of the graphene oxide aqueous dispersion, magnetically stirring the reducing agent and the graphene oxide aqueous dispersion at a mass ratio of 1-3.5:100 at 200-500 rpm for 10-60 min to uniformly disperse, reacting at 80-120 ℃ for 1-3 h, and ultrasonically dispersing for 10-60 min to obtain the reduced graphene aqueous dispersion.
Wherein the graphene oxide aqueous dispersion of 2mg/m L-4 mg/m L includes any value within this numerical range, for example, the graphene oxide aqueous dispersion is 2mg/m L, 2.2mg/m L, 2.5mg/m L, 2.8mg/m L, or 3mg/m L.
The mass ratio of the reducing agent to the graphene oxide aqueous dispersion is 1-3.5:100 inclusive, for example, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, or 3.5: 100.
Magnetically stirring at 200-500 rpm for 10-60 min for dispersion stirring, wherein the rotation speed is 200-500 rpm inclusive of any point value within the range of values, such as 200, 250, 300, 350, 400, 450, or 500 rpm; the stirring time of 10min-60min includes any point in the time range, for example, the stirring time is 10min, 20min, 25min, 30min, 40min, 50min or 60 min.
Carrying out reaction for 1-3 h at constant temperature of 80-120 ℃, and then carrying out ultrasonic dispersion for 10-60 min, wherein the constant temperature of 80-120 ℃ comprises any point value in the temperature range, such as constant temperature of 80 ℃, 85 ℃, 90 ℃, 100 ℃, 105 ℃, 110 ℃ or 120 ℃; reactions 1h to 3h include any point within the reaction time range, e.g., reactions 1h, 1.2h, 1.5h, 2h, 2.5h, or 3 h; the ultrasonic dispersion for 10min to 60min includes any point value in the time range, such as ultrasonic dispersion for 10min, 20min, 30min, 40min, 50min or 60 min.
Optionally, the reducing agent is selected from hydrazine hydrate, vitamin C, ethylenediamine, or sodium bisulfate.
Further, in the step of preparing the reduced graphene aqueous dispersion, a surfactant is added into a reaction system of the graphene oxide aqueous dispersion and the reducing agent, and the mass ratio of the surfactant to the graphene oxide aqueous dispersion is 10-25: 100.
Wherein the mass ratio of the surfactant to the aqueous graphene oxide dispersion is 10-25:100 inclusive, for example, 10:100, 15:100, 18:100, 20:100, 22:100, or 25: 100.
Optionally, the surfactant is selected from polyvinylpyrrolidone or sodium dodecylbenzenesulfonate.
Further, the preparation method comprises the steps of dispersing and diluting the reduced graphene aqueous dispersion by 1-6 times by using water after preparing the reduced graphene aqueous dispersion, carrying out ultrasonic dispersion for 10-60 min, and then stirring and carrying out ultrasonic treatment on the reduced graphene aqueous dispersion and the inorganic salt.
Further, the inorganic salt is one of calcium salt, potassium salt, sodium salt, magnesium salt, iron salt, zinc salt or aluminum salt.
Preferably, the inorganic salt is calcium chloride dihydrate.
Further, in the step of stirring and ultrasonically treating the reduced graphene aqueous dispersion and calcium chloride dihydrate, the mass ratio of the calcium chloride dihydrate to the diluted water in the reduced graphene aqueous dispersion is less than or equal to 2.044: 1; magnetically stirring at 200-500 rpm for 5-30 min, and ultrasonically dispersing for 10-60 min to obtain the reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase change material.
Wherein the mass ratio of the calcium chloride dihydrate to the water in the diluted reduced graphene aqueous dispersion is less than or equal to 2.044:1, including any value within the range of the ratio, for example, the mass ratio of the calcium chloride dihydrate to the diluted reduced graphene aqueous dispersion is 2.044:1, 2:1, 1.8:1, 1.5:1, 1.2:1, 1: 1.
Magnetically stirring at 200-500 rpm for 5-30 min, and ultrasonically dispersing for 10-60 min, wherein the rotation speed of 200-500 rpm includes any point value in the numerical range, such as 200, 250, 300, 350, 400, 450 or 500 rpm; the stirring time is 5min-30min including any point value in the time range, such as 5min, 10min, 15min, 20min, 25min, 30 min; the ultrasonic dispersion for 10min-60min includes any point value in the time range, such as ultrasonic dispersion for 10min, 20min, 25min, 30min, 40min, 50min or 60 min.
Further, the thermal conductivity of the reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase change material is 0.8W (m.K)-1-1.2W·(m·K)-1。
The invention has the following beneficial effects:
1. the hydrated salt phase-change material obtained by the invention has higher thermal conductivity and has less influence on other properties (such as enthalpy) of the phase-change material. The graphene has extraordinary specific surface area and excellent heat-conducting property (5000W (m.K))-1) However, van der waals force between graphene layers and hydrophobicity thereof cause that it is difficult to be directly dispersed in an aqueous solution, and high thermal conductivity thereof cannot be directly utilized in a phase change energy storage material. Although graphene oxide can easily prepare a graphene oxide aqueous dispersion with stable dispersion due to a large amount of hydrophilic functional groups on the surface thereof, it has a structural defect due to oxidation, resulting in poor thermal conductivity. However, the thermal conductivity of the reduced graphene oxide is recovered, and the reduced graphene oxide has good dispersibility after a certain amount of surfactant is added into water, so that the reduced graphene oxide is reduced to obtain the reduced graphene which can be stably dispersed, and then the reduced graphene oxide and corresponding salts are used for preparing the high-thermal-conductivity hydrated salt phase-change energy storage material. Therefore, the purpose that the thermal conductivity of the phase-change material can be greatly improved by adding a small amount of reduced graphene into inorganic salt is achieved, and the heat transfer performance of the phase-change material is improved. Meanwhile, the enthalpy value of the phase-change material is reduced less.
2. The preparation method has wide application range, and all inorganic hydrated salt phase change energy storage materials can prepare the phase change material with high heat conduction and less phase change enthalpy value reduction by reducing the graphene aqueous dispersion and the corresponding salts thereof.
3. The performance of the hydrous salt phase-change material obtained by the invention is superior to that of other additives. Firstly, compared with the means of directly adding carbon materials such as graphite powder and the like, the method firstly prepares the reduced graphene aqueous dispersion with stable dispersion performance, and then directly prepares the hydrated salt phase-change material by using the reduced graphene aqueous dispersion, so that the carbon materials have better dispersion performance and thermal conductivity. Therefore, the thermal conductivity of the phase change material can be greatly increased and the reduction of the phase change enthalpy value of the phase change energy storage material can be reduced by adding a small amount of well-dispersed reduced graphene. And secondly, the performance of the additive is superior to that of other heat transfer performance improving additives such as alumina nano particles, nano metal and the like.
Drawings
Fig. 1 is a schematic diagram of a stability test result of a reduced graphene aqueous dispersion in an embodiment of the invention;
fig. 2 is a schematic structural diagram of a stability test of an aqueous reduced graphene dispersion in a stably-dispersed calcium chloride hexahydrate hydrated salt phase-change material of reduced graphene according to an embodiment of the present invention;
fig. 3 is a DSC curve of a reduced graphene stably dispersed calcium chloride hexahydrate hydrated salt phase change material and calcium chloride hexahydrate.
Detailed Description
Example one
The embodiment provides a high-thermal-conductivity hydrous salt phase change material, and a preparation method thereof comprises the following steps:
preparing a reduced graphene aqueous dispersion, namely preparing a 2mg/m L graphene oxide aqueous dispersion by using a hummers method, magnetically stirring hydrazine hydrate, polyvinylpyrrolidone and the graphene oxide aqueous dispersion at 400rpm for 30min to disperse uniformly, reacting in a 90 ℃ thermostat for 2h, and then ultrasonically dispersing for 30min to obtain the reduced graphene aqueous dispersion, wherein the mass ratio of the hydrazine hydrate to the graphene oxide aqueous dispersion is 2.3:100, and the mass ratio of the polyvinylpyrrolidone to the graphene oxide aqueous dispersion is 18.2: 100.
And diluting the prepared reduced graphene aqueous dispersion by 3.5 times by using deionized water, and performing ultrasonic dispersion for 30min to obtain the diluted reduced graphene aqueous dispersion. It is understood that, in the present invention, the prepared aqueous reduced graphene dispersion may not be subjected to dispersion dilution, and in the case of omitting this step, a hydrous salt phase change material having high thermal conductivity may be obtained by adding a smaller mass of the aqueous reduced graphene dispersion to calcium chloride dihydrate.
And magnetically stirring the calcium chloride dihydrate and the diluted reduced graphene aqueous dispersion for 5min at 400rpm according to the mass ratio of the calcium chloride dihydrate to water in the diluted reduced graphene aqueous dispersion of 2.044:1, and then ultrasonically dispersing for 10min-60min to obtain the reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase change material.
In this embodiment, the mass ratio of the calcium chloride dihydrate to the water in the diluted reduced graphene aqueous dispersion conforms to the mass ratio of the calcium chloride dihydrate to the tetramolecular water in the calcium chloride hexahydrate, so that the calcium chloride hexahydrate and the phase-change material stably dispersed by the reduced graphene can be finally obtained. It can be understood that other inorganic salts and the reduced graphene aqueous dispersion can be stirred and subjected to ultrasonic treatment to obtain the high-thermal-conductivity hydrated salt phase-change material.
As shown in fig. 1, the reduced graphene aqueous dispersion obtained in this example was allowed to stand for three months and nine months in this order to observe the state. The result shows that the reduced graphene aqueous dispersion liquid of the embodiment has high stability and does not agglomerate after standing for a long time.
As shown in fig. 2, after the calcium chloride hexahydrate hydrated salt phase change material is finally prepared in this example, the phase change material is sequentially left to stand for one month and two months, and the dispersion stability of the reduced graphene is observed. The result shows that the reduced graphene is stably dispersed in the calcium chloride hexahydrate solution.
As shown in fig. 3, DSC curves of the reduced graphene stably dispersed calcium chloride hexahydrate hydrated salt phase change material and calcium chloride hexahydrate are shown. As can be seen from the figure, the reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase-change material prepared by the invention only reduces the enthalpy value by about 2.9%. In addition, the thermal conductivity of calcium chloride hexahydrate is about 0.56W (m.K) at 30 ℃-1The reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase change material prepared by the inventionThe thermal conductivity of the material is about 1.01W (m.K)-1The thermal conductivity of the calcium chloride hexahydrate is improved by about 1 time.
Example two
The embodiment provides a high-thermal-conductivity hydrous salt phase change material, and a preparation method thereof comprises the following steps:
preparing a reduced graphene aqueous dispersion, namely preparing a 4mg/m L graphene oxide aqueous dispersion by using a hummers method, magnetically stirring hydrazine hydrate, polyvinylpyrrolidone and the graphene oxide aqueous dispersion at 200rpm for 50min to disperse uniformly, reacting in a thermostat at 110 ℃ for 3h, and then ultrasonically dispersing for 50min to obtain the reduced graphene aqueous dispersion, wherein the mass ratio of the hydrazine hydrate to the graphene oxide aqueous dispersion is 3:100, and the mass ratio of the polyvinylpyrrolidone to the graphene oxide aqueous dispersion is 25: 100.
And diluting the prepared reduced graphene aqueous dispersion by 6 times by using deionized water, and performing ultrasonic dispersion for 50min to obtain the diluted reduced graphene aqueous dispersion.
And magnetically stirring the calcium chloride dihydrate and the diluted reduced graphene aqueous dispersion for 30min at 200rpm according to the mass ratio of the calcium chloride dihydrate to water in the diluted reduced graphene aqueous dispersion of 2.044:1, and then ultrasonically dispersing for 60min to obtain the calcium chloride hexahydrate hydrated salt phase change material with the stably dispersed reduced graphene.
EXAMPLE III
The embodiment provides a high-thermal-conductivity hydrous salt phase change material, and a preparation method thereof comprises the following steps:
preparing a reduced graphene aqueous dispersion, namely preparing a 2.5mg/m L oxidized graphene aqueous dispersion by using a hummers method, uniformly dispersing hydrazine hydrate, polyvinylpyrrolidone and the oxidized graphene aqueous dispersion by magnetic stirring at 500rpm for 10min, then reacting in an incubator at 80 ℃ for 1h, and then ultrasonically dispersing for 10min to obtain the reduced graphene aqueous dispersion, wherein the mass ratio of ethylenediamine to the oxidized graphene aqueous dispersion is 1:100, and the mass ratio of the polyvinylpyrrolidone to the oxidized graphene aqueous dispersion is 10: 100.
And diluting the prepared reduced graphene aqueous dispersion by 1 time by using deionized water, and performing ultrasonic dispersion for 10min to obtain the diluted reduced graphene aqueous dispersion.
And magnetically stirring the calcium chloride dihydrate and the diluted reduced graphene aqueous dispersion for 30min at 200rpm according to the mass ratio of the calcium chloride dihydrate to water in the diluted reduced graphene aqueous dispersion of 2.044:1, and then ultrasonically dispersing for 10min to obtain the calcium chloride hexahydrate hydrated salt phase change material with the stably dispersed reduced graphene.
It should be understood that the above examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. It should also be understood that after reading the technical content of the present invention, those skilled in the art can make appropriate changes to the conditions and steps in the technical solution of the invention to realize the final technical solution without departing from the principle of the present invention, and all the equivalent forms are also within the protection scope defined by the appended claims of the present application.
Claims (7)
1. The preparation method of the high-thermal-conductivity hydrated salt phase-change material is characterized by comprising the following steps of:
preparing a reduced graphene aqueous dispersion solution containing a surfactant;
magnetically stirring the reduced graphene aqueous dispersion and calcium chloride dihydrate at 200-500 rpm for 5-30 min, and ultrasonically dispersing for 10-60 min to obtain a reduced graphene stably-dispersed calcium chloride hexahydrate hydrated salt phase-change material; wherein the mass ratio of the calcium chloride dihydrate to the water in the diluted reduced graphene water dispersion is less than or equal to 2.044: 1.
2. The method of claim 1, wherein: the reduced graphene aqueous dispersion is obtained by reducing a graphene oxide aqueous dispersion with a reducing agent.
3. The method of claim 2, wherein: the preparation method of the reduced graphene aqueous dispersion comprises the following steps: preparing the graphene oxide aqueous dispersion by a hummers method; and stirring and dispersing the reducing agent and the graphene oxide aqueous dispersion, reacting at a constant temperature, and performing ultrasonic dispersion to obtain the reduced graphene aqueous dispersion.
4. The preparation method of the reduced graphene aqueous dispersion liquid as claimed in claim 3, wherein the step of preparing the reduced graphene aqueous dispersion liquid is to prepare 2mg/m L-4 mg/m L of the graphene oxide aqueous dispersion liquid, magnetically stir the reducing agent and the graphene oxide aqueous dispersion liquid in a mass ratio of 1-3.5:100 at 200-500 rpm for 10-60 min to disperse uniformly, react at 80-120 ℃ for 1-3 h, and then perform ultrasonic dispersion for 10-60 min to obtain the reduced graphene aqueous dispersion liquid, wherein the reducing agent is selected from hydrazine hydrate, vitamin C, ethylenediamine or sodium bisulfate.
5. The production method according to any one of claims 2 to 4, characterized in that: in the step of preparing the reduced graphene aqueous dispersion, a surfactant is added into a reaction system of the graphene oxide aqueous dispersion and the reducing agent, and the mass ratio of the surfactant to the graphene oxide aqueous dispersion is 10-25: 100; the surfactant is selected from polyvinylpyrrolidone or sodium dodecyl benzene sulfonate.
6. The method of claim 1, wherein: the preparation method further comprises the steps of dispersing and diluting the reduced graphene aqueous dispersion by 1-6 times by using water after preparing the reduced graphene aqueous dispersion, carrying out ultrasonic dispersion for 10-60 min, and then stirring and carrying out ultrasonic treatment on the reduced graphene aqueous dispersion and the calcium chloride dihydrate.
7. The method of claim 1, wherein: the thermal conductivity of the reduced graphene stably dispersed calcium chloride hexahydrate hydrated salt phase change material is 0.8W (m.K)-1-1.2W·(m·K)-1。
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