Composite Phase Change Material and Its Preparation Method

Abstract

The present invention provides a composite phase change material and a preparation method thereof. By mass percentage, the composite phase change material comprises: 94-96% of erythritol and 4-6% of graphene oxide. The liquid containing graphene oxide increases the interfacial area and acts as a nucleating agent, thereby inducing heterogeneous nucleation of the liquid containing erythritol and inducing the formation of "seed crystals" similar to the solid structure of erythritol on the surface of graphene oxide. At the same time, graphene oxide reduces the degree of freedom of erythritol, thereby reducing the supercooling degree of the composite phase change material. In addition, if the content of the graphene oxide thermal conductive material is too low, it is easy to cause the state of the composite phase change material to be unstable before shaping, and if the content of the graphene oxide thermal conductive material is too high, it is easy to cause the composite phase change material to crack. Therefore, the above composite phase change material of the present application can solve the problems of high supercooling degree and poor thermal conductivity of the erythritol-based phase change material.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change materials, and in particular, to a composite phase change material and a preparation method thereof. Background Art

[0002] Energy is the basis for human survival and development. With the rapid development of science and technology, people's demand for energy is increasing day by day. However, the resources of traditional fossil fuels are limited, and many environmental problems are brought about while consuming fossil energy. Therefore, exploring and researching new energy materials has become an important global research topic.

[0003] In recent years, as a new type of environmentally friendly heat storage material, phase change materials are in a very active research field in energy utilization research, and have broad application prospects in fields such as solar thermal utilization, power grid peak shaving and valley filling, waste heat recovery, aerospace, and battery thermal management. Erythritol (ET) is a medium-temperature organic phase change material, which has the advantages of non-toxic, non-flammable, extremely high melting enthalpy (about 340.0 J·g -1 ) and good thermal stability, etc. It is a phase change heat storage material with great application prospects and can be used in fields such as solar thermal utilization and waste (waste) heat recovery. However, although erythritol has many advantages, it is not perfect. Through research, it is found that the two most prominent defects of erythritol phase change materials are serious supercooling phenomenon and low thermal conductivity, and its supercooling degree reaches more than 100 °C. On the one hand, supercooling will cause the phase change material to be unable to store and release heat at the expected temperature, resulting in the problem of temperature control failure of the system. Therefore, the supercooling problem of erythritol phase change materials should be eliminated as much as possible. On the other hand, low thermal conductivity will lead to a slow heat transfer rate and fail to reach the ideal heat storage and heat release state. Therefore, researching an erythritol-based phase change material with a low supercooling degree and maintaining its large phase change latent heat has great application prospects. Summary of the Invention

[0004] The main object of the present invention is to provide a composite phase change material and a preparation method thereof to solve the problems of high supercooling degree and poor thermal conductivity of erythritol-based phase change materials in the prior art.

[0005] To achieve the above object, according to one aspect of the present invention, a composite phase change material is provided. Calculated by mass percentage, the composite phase change material includes: 94-96% of erythritol and 4-6% of graphene oxide.

[0006] Furthermore, the mass ratio of the above graphene oxide to erythritol is 1:16-1:20.

[0007] Furthermore, the particle size of the above composite phase change material is 100-400 nm.

[0008] According to another aspect of the present invention, there is provided a method for preparing the aforementioned composite phase change material, the preparation method comprising: Step S1, mixing materials including erythritol, graphene oxide and a solvent to obtain a mixture; Step S2, drying and homogenizing the mixture to obtain the composite phase change material.

[0009] Further, the above-mentioned Step S1 includes stirring or ultrasonic treatment of the materials to obtain a mixture. Preferably, the ultrasonic frequency is 50 - 200 Hz, the ultrasonic time is preferably 4 - 6 h, the stirring speed is preferably 800 - 1200 r / min, and the stirring time is preferably 5 - 10 h.

[0010] Further, the particle size of the above-mentioned graphene oxide is 300 - 600 nm, preferably 300 - 400 nm.

[0011] Further, the above-mentioned solvent is selected from any one or a combination of water, methanol, ethanol, acetone.

[0012] Further, the above-mentioned solvent is a mixed solution of ethanol and water. Preferably, the volume ratio of ethanol to water in the mixed solution is 2 - 6:1 - 3, and more preferably 3 - 6:1.

[0013] Further, the above-mentioned homogenization is grinding.

[0014] Further, the temperature of the above-mentioned drying is 50 - 100 °C.

[0015] Applying the technical solution of the present invention, graphene oxide has a layered structure and contains a large number of oxygen-containing functional groups on the basal plane and edges of the layered structure, such as hydroxyl groups, carboxyl groups, and epoxy groups. The presence of these oxygen-containing functional groups makes graphene oxide negatively charged, while erythritol contains a large number of alcohol hydroxyl groups. During the formation of the composite phase change material, the liquid containing graphene oxide increases the interfacial area and acts as a nucleating agent, thereby inducing heterogeneous nucleation of the liquid containing erythritol, that is, the hydroxyl groups in graphene oxide form hydrogen bonds with the hydroxyl groups in erythritol, and induce the formation of "seeds" similar to the solid structure of erythritol on the surface of graphene oxide. At the same time, graphene oxide reduces the degree of freedom of erythritol, thereby reducing the supercooling degree of the composite phase change material. In addition, if the content of graphene oxide thermal conductive material is too low, it is easy to cause the state of the composite phase change material before shaping to be unstable, and if the content of graphene oxide thermal conductive material is too high, it is easy to cause cracking of the composite phase change material. Therefore, the above-mentioned composite phase change material of the present application can solve the problems of high supercooling degree and poor thermal conductivity of erythritol-based phase change materials. And graphene oxide is a material with excellent electrical conductivity, making the composite phase change material have excellent electrical conductivity. Description of the Drawings

[0016] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 Shows the DSC curve graph of the thermal performance test of the ET / GO composite phase change material 1 and the ET phase change material provided in Embodiment 1 of the present application;

[0018] Figure 2 Shows the thermal conductivity graphs of the phase change materials obtained in Embodiment 1, Comparative Examples 1 to 3 of the present application; and

[0019] Figure 3 Shows the shaping test graphs of the phase change materials obtained in Embodiment 1, Comparative Examples 1 to 3 of the present application. Detailed implementation manners

[0020] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0021] As analyzed in the background art, there are problems of high supercooling degree and poor thermal conductivity of erythritol-based phase change materials in the prior art. To solve this technical problem, the present invention provides a composite phase change material and a preparation method thereof.

[0022] In a typical implementation manner of the present application, a composite phase change material is provided. Calculated by mass percentage, the composite phase change material includes: 94-96% of erythritol and 4-6% of graphene oxide.

[0023] Graphene oxide has a layered structure and contains a large number of oxygen-containing functional groups on the basal plane and edges of the layered structure, such as hydroxyl groups, carboxyl groups, and epoxy groups. The presence of these oxygen-containing functional groups makes graphene oxide negatively charged, while erythritol contains a large number of alcohol hydroxyl groups. During the formation of the composite phase change material, the liquid containing graphene oxide increases the interfacial area and acts as a nucleating agent, thereby inducing heterogeneous nucleation of the liquid containing erythritol. That is, the hydroxyl groups in graphene oxide form hydrogen bonds with the hydroxyl groups in erythritol, and induce the formation of "seed crystals" similar to the solid structure of erythritol on the surface of graphene oxide. At the same time, graphene oxide reduces the degree of freedom of erythritol, thereby reducing the supercooling degree of the composite phase change material. In addition, too low content of graphene oxide thermal conductive material is likely to lead to instability of the state of the composite phase change material before shaping, and too high content of graphene oxide thermal conductive material is likely to cause cracking of the composite phase change material. Therefore, the above composite phase change material of the present application can solve the problems of high supercooling degree and poor thermal conductivity of erythritol-based phase change materials. And graphene oxide is a material with excellent electrical conductivity, making the composite phase change material have excellent electrical conductivity.

[0024] To further improve the above synergistic effect of erythritol and graphene oxide, it is preferred that the mass ratio of graphene oxide to erythritol is 1:16 to 1:20.

[0025] To give full play to the temperature control and heat storage performance of the composite phase change material, so that the composite phase change material can be more widely used, it is preferred that the particle size of the above composite phase change material is 100 to 400 nm.

[0026] In another typical embodiment of the present application, a preparation method of the foregoing composite phase change material is provided. The preparation method includes: Step S1, mixing a material including erythritol, graphene oxide and a solvent to obtain a mixture; Step S2, drying and homogenizing the mixture to obtain the composite phase change material.

[0027] Graphene oxide has a layered structure and contains a large number of oxygen-containing functional groups on the basal plane and edges of the layered structure, such as hydroxyl groups, carboxyl groups, and epoxy groups. The presence of these oxygen-containing functional groups makes graphene oxide negatively charged, while erythritol contains a large number of alcohol hydroxyl groups. In the formation process of the above composite phase change material, solid erythritol, graphene oxide, and a solvent are first mixed to form a uniformly dispersed mixture, so that erythritol and graphene oxide can be mixed more evenly, enabling the functional groups of the two to act better. Then, through a simple drying and homogenization process, a composite phase change material with excellent performance is obtained. Specifically, the liquid containing graphene oxide increases the interfacial area and acts as a nucleating agent, thereby inducing heterogeneous nucleation of the liquid containing erythritol. That is, the hydroxyl groups in graphene oxide form hydrogen bonds with the hydroxyl groups in erythritol, and induce erythritol to form "seed crystals" similar to the solid structure of erythritol on the surface of graphene oxide. At the same time, graphene oxide reduces the degree of freedom of erythritol, thereby reducing the supercooling degree of the composite phase change material. In addition, if the content of the graphene oxide thermal conductive material is too low, it is easy to cause the state of the composite phase change material to be unstable before shaping. If the content of the graphene oxide thermal conductive material is too high, it is easy to cause cracking of the composite phase change material. Therefore, the composite phase change material obtained by the above preparation method of the present application can solve the problems of high supercooling degree and poor thermal conductivity of the erythritol-based phase change material.

[0028] To make erythritol and graphene oxide mix more evenly, thereby improving the modification effect of graphene oxide on erythritol, it is preferred that the above step S1 includes stirring or ultrasonic treatment of the materials to obtain a mixture. The ultrasonic frequency is preferably 50 - 200 Hz, the ultrasonic time is preferably 4 - 6 h, the stirring speed is preferably 800 - 1200 r / min, and the stirring time is preferably 5 - 10 h.

[0029] To improve the dispersion effect of graphene oxide in erythritol, make erythritol and graphene oxide mix more evenly, so that the two can more fully carry out the synergy between functional groups, and then obtain a composite phase change material with better performance, it is preferred that the particle size of the above graphene oxide is 300 - 600 nm, preferably 300 - 400 nm.

[0030] In an embodiment of the present application, the above solvent is selected from any one or a combination of water, methanol, ethanol, and acetone.

[0031] The graphene oxide of the present application is an amphiphilic substance, and erythritol is a water-soluble substance. To improve the compatibility of the two in the solvent and thus mix the two more fully, it is preferred to use the above solvent.

[0032] To further improve the solubility of graphene oxide and erythritol in the solvent, so that the two are more evenly mixed, it is preferred that the above solvent is a mixed solution of ethanol and water, and the volume ratio of ethanol and water in the mixed solution is preferably 2-6:1-3, and more preferably 3-6:1.

[0033] A more suitable particle size of the composite phase change material is obtained by homogenization. To balance the efficiency and cost of homogenization in this application, it is preferred that the above homogenization is grinding. Of course, those skilled in the art can also adopt other commonly used homogenization methods according to actual needs and the homogenization equipment they have, which will not be elaborated here.

[0034] To improve the drying efficiency of the mixture without affecting the performance of erythritol and graphene oxide, it is preferred that the drying temperature is 50-100 °C, and the drying time is preferably 5-12 h.

[0035] The beneficial effects of this application will be described below in combination with specific examples and comparative examples.

[0036] The raw materials used in the following examples and comparative examples:

[0037] Erythritol (analytical pure, Hefei Bomei Biotechnology Co., Ltd.); graphene oxide (analytical pure, Angxing New Carbon Materials Changzhou Co., Ltd.); ethanol, methanol and acetone (analytical pure, Shandong Deyan Chemical Co., Ltd.).

[0038] Example 1

[0039] Weigh about 4 g of erythritol (ET) and 0.2 g of graphene oxide (GO, particle size of 300 nm) and place them in a beaker (the mass ratio of graphene oxide to erythritol is 1:20). Use a mixed solvent of ethanol and water (100 mL) to dissolve erythritol and graphene oxide. Among them, the volume ratio of ethanol to water is 6:1, and the ultrasonic time is 6 h at an ultrasonic frequency of 200 Hz to obtain a mixture. The mixture is dried in a constant temperature oven at 80 °C for 8 h to obtain a dried mixture, and the dried mixture is ground to obtain an ET / GO composite phase change material 1 with a particle size of 400 nm.

[0040] The DSC curve of the thermal performance test of the ET / GO composite phase change material 1 is as Figure 1 shown. When it is from Figure 1 the relevant thermodynamic parameters of the ET / GO composite phase change material 1 can be obtained as shown in Table 1. The thermal conductivity of the ET / GO composite phase change material 1 is as Figure 2 shown. The shaping test diagram of the ET / GO composite phase change material 1 is as Figure 3 C and c in (where C represents before heating and c represents after heating). From Figure 3It can be seen that the appearance of the ET / GO composite phase change material 1 remains intact after heating, without collapse and leakage, indicating that the erythritol phase change material is coated with graphene oxide under this condition and has good shape-stabilized performance.

[0041] Table 1

[0042]

[0043] Example 2

[0044] The difference between Example 2 and Example 1 is that the mass of erythritol is changed so that the mass ratio of graphene oxide to erythritol is 1:16, and finally the ET / GO composite phase change material 2 is obtained.

[0045] Example 3

[0046] The difference between Example 3 and Example 1 is that the mass of erythritol is changed so that the mass ratio of graphene oxide to erythritol is 1:18, and finally the ET / GO composite phase change material 3 is obtained.

[0047] Example 4

[0048] The difference between Example 4 and Example 1 is that the mass of erythritol is changed so that the mass ratio of graphene oxide to erythritol is 1:24, and finally the ET / GO composite phase change material 4 is obtained.

[0049] Example 5

[0050] The difference between Example 5 and Example 1 is that the mass of erythritol is changed so that the mass ratio of graphene oxide to erythritol is 1:15.7, and finally the ET / GO composite phase change material 5 is obtained.

[0051] Example 6

[0052] The difference between Example 6 and Example 1 is that the ultrasonic frequency is 50 Hz, and finally the ET / GO composite phase change material 6 is obtained.

[0053] Example 7

[0054] The difference between Example 7 and Example 1 is that the ultrasonic frequency is 150 Hz, and finally the ET / GO composite phase change material 7 is obtained.

[0055] Example 8

[0056] The difference between Example 8 and Example 1 is that the ultrasonic frequency is 40 Hz, and finally the ET / GO composite phase change material 8 is obtained.

[0057] Example 9

[0058] Example 9 is different from Example 1 in that the time of ultrasound is 4 h, and finally the ET / GO composite phase change material 9 is obtained.

[0059] Example 10

[0060] Example 10 is different from Example 1 in that mixing is carried out by stirring, the rotation speed of stirring is 800 r / min, the time of stirring is 10 h, and finally the ET / GO composite phase change material 10 is obtained.

[0061] Example 11

[0062] Example 11 is different from Example 1 in that mixing is carried out by stirring, the rotation speed of stirring is 1200 r / min, the time of stirring is 5 h, and finally the ET / GO composite phase change material 11 is obtained.

[0063] Example 12

[0064] Example 12 is different from Example 1 in that mixing is carried out by stirring, the rotation speed of stirring is 1000 r / min, the time of stirring is 8 h, and finally the ET / GO composite phase change material 12 is obtained.

[0065] Example 13

[0066] Example 13 is different from Example 10 in that mixing is carried out by stirring, the rotation speed of stirring is 500 r / min, and finally the ET / GO composite phase change material 13 is obtained.

[0067] Example 14

[0068] Example 14 is different from Example 1 in that the particle size of graphene oxide is 400 nm, and finally the ET / GO composite phase change material 14 is obtained.

[0069] Example 15

[0070] Example 15 is different from Example 1 in that the particle size of graphene oxide is 600 nm, and finally the ET / GO composite phase change material 15 is obtained.

[0071] Example 16

[0072] Example 16 is different from Example 1 in that the particle size of graphene oxide is 700 nm, and finally the ET / GO composite phase change material 16 is obtained.

[0073] Example 17

[0074] Example 17 is different from Example 1 in that the solvent is ethanol, and finally the ET / GO composite phase change material 17 is obtained.

[0075] Example 18

[0076] Example 18 is different from Example 1 in that the volume ratio of ethanol to water is 3:1, and finally ET / GO composite phase change material 18 is obtained.

[0077] Example 19

[0078] Example 19 is different from Example 1 in that the volume ratio of ethanol to water is 5:1, and finally ET / GO composite phase change material 19 is obtained.

[0079] Example 20

[0080] Example 20 is different from Example 1 in that the volume ratio of ethanol to water is 2:3, and finally ET / GO composite phase change material 20 is obtained.

[0081] Example 21

[0082] Example 21 is different from Example 1 in that the drying temperature is 50 °C, and finally ET / GO composite phase change material 21 is obtained.

[0083] Example 22

[0084] Example 22 is different from Example 1 in that the drying temperature is 100 °C, and finally ET / GO composite phase change material 22 is obtained.

[0085] Example 23

[0086] Example 23 is different from Example 1 in that the particle size of the finally obtained ET / GO composite phase change material 23 is 100 nm.

[0087] Example 24

[0088] Example 24 is different from Example 1 in that the particle size of the finally obtained ET / GO composite phase change material 24 is 200 nm.

[0089] Comparative Example 1

[0090] The difference between Comparative Example 1 and Example 1 is that

[0091] Weigh 4.2 g of erythritol and place it in a beaker. Dissolve the erythritol with a mixed solvent of ethanol and water. Among them, the volume ratio of ethanol to water is 6:1. After ultrasonic treatment at a frequency of 200 Hz for 6 h, it is dried in a constant temperature oven at 80 °C for 8 h and then ground to obtain ET phase change material 25. The DSC curve of the thermal performance test of this ET phase change material 25 is as Figure 1 shown. From Figure 1 the relevant thermodynamic parameters of ET phase change material 25 can be obtained, as shown in Table 1. The thermal conductivity of this ET phase change material 25 is as Figure 2 shown. The shaping test diagram of this ET phase change material 25 is asFigure 3 as shown by A and a in (where A represents before heating and a represents after heating), from Figure 3 it can be seen that the ET phase change material 25 before heating is in a solid state with a good shape, and after heating, the ET phase change material 25 melts and its volume significantly decreases.

[0092] Comparative Example 2

[0093] The difference between Comparative Example 2 and Example 1 is that

[0094] Weigh about 4 g of erythritol and 0.1 g of graphene oxide and place them in a beaker. Use a mixed solvent of ethanol and water to dissolve the erythritol and graphene oxide. Finally, obtain the ET / GO composite phase change material 26. The thermal conductivity of the ET / GO composite phase change material 26 is as Figure 2 shown. The thermal conductivity of the ET / GO composite phase change material 26 is as Figure 2 shown. The shaping test diagram of the ET / GO composite phase change material 26 is as Figure 3 shown by B and b in (where B represents before heating and b represents after heating). From Figure 3 it can be seen that after heating, the ET / GO composite phase change material 26 does not significantly show collapse and leakage phenomena, but the shaping state before heating is unstable and there are gaps, which is caused by too low content of graphene oxide thermal conductive material.

[0095] Comparative Example 3

[0096] The difference between Comparative Example 3 and Example 1 is that

[0097] Weigh about 4 g of erythritol and 0.3 g of graphene oxide and place them in a beaker. Use a mixed solvent of ethanol and water to dissolve the erythritol and graphene oxide. Finally, obtain the ET / GO composite phase change material 27. The thermal conductivity of the ET / GO composite phase change material 27 is as Figure 2 shown. The thermal conductivity of the ET / GO composite phase change material 27 is as Figure 2 shown. The shaping test diagram of the ET / GO composite phase change material 27 is as Figure 3 shown by D and d in (where D represents before heating and d represents after heating). From Figure 3 it can be seen that the shaping effect of the ET / GO composite phase change material 27 before heating is good, but after heating, the composite phase change material cracks, which is caused by too high content of graphene oxide thermal conductive material.

[0098] The process of the above thermal performance test is as follows: Using a Q2000 differential scanning calorimeter (DSC) produced by TA Instruments, USA, the heat storage performance of ET / GO composite phase change materials 1 to 24, ET phase change material 25, and ET / GO composite phase change materials 26 and 27 was tested respectively as follows: 4-8 mg of the phase change material was placed in the crucible of the sample to be tested, and the test was carried out under a nitrogen flow rate of 50 mL·min -1 atmosphere, the measurement temperature range was -20.0 to 140.0 °C, and the measurement program was set to scan at a heating rate of 5 °C / min. Among them, the DSC curves of Example 1 and Comparative Example 1 are as Figure 1 shown. Analyzing the DSC curve to obtain the initial phase change temperature and phase change latent heat of the phase change material. From Figure 1 it can be seen that the ET / GO composite phase change material can effectively suppress the supercooling degree, and the supercooling degree value is reduced to 36.11 °C (the calculation method of supercooling degree is the difference between the melting temperature and the crystallization temperature). Compared with the supercooling degree of pure erythritol (100.98 °C), it is reduced by 64.24%, and it has a relatively high melting enthalpy (227.20 J·g -1 ) and solidification enthalpy (209.60 J·g -1 ). Its solidification enthalpy is 0.26% higher than that of the pure phase change material, greatly improving its phase change latent heat, thus solving the problems of large supercooling degree and low thermal conductivity of the single pure erythritol phase change material.

[0099] The process of the above thermal conductivity test is as follows: The ET / GO composite phase change materials 1 to 24, ET phase change material 25, and ET / GO composite phase change materials 26 and 27 were tested respectively by a thermal conductivity meter. Among them, the thermal conductivity of the phase change material samples of Example 1 and Comparative Examples 1 to 3 is as Figure 2 shown. The thermal conductivity (λ) of ET / GO composite phase change material 1 is 5.752 W·m -1 ·K -1 , which is 16.59 times higher than that of pure erythritol (λ = 0.327 W·m -1 ·K -1 ). Therefore, ET / GO composite phase change material 1 significantly accelerates the heat absorption and release rates of the pure erythritol phase change material.

[0100] The process of the shaping performance test is as follows: The morphological changes of the phase change materials of Example 1 and Comparative Examples 1 to 3 before and after heating were observed by the shaping performance test: The phase change materials were respectively pressed into sample tablets with a thickness of 2 mm by a tablet press, and then placed in an electrothermal vacuum drying oven with a temperature set at 140.0 °C for constant temperature heating for 2 h to obtain the shaping test diagram as Figure 3 shown.

[0101] The contents of erythritol, graphene oxide, the particle sizes, supercooling degrees and thermal conductivities of the above-mentioned ET / GO composite phase change materials 1 to 24, ET phase change material 25, and ET / GO composite phase change materials 26 and 27 are listed in Table 2.

[0102] Table 2

[0103]

[0104]

[0105] In summary, the ET / GO composite phase change material is a composite phase change material with low supercooling degree, high phase change enthalpy and high thermal conductivity. This composite phase change material has excellent heat storage and release performance, strong stability and thermal conductivity, and can be used in fields such as solar thermal utilization and waste heat recovery.

[0106] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0107] Graphene oxide has a layered structure, and a large number of oxygen-containing functional groups such as hydroxyl groups, carboxyl groups, and epoxy groups are contained on the basal plane and edges of the layered structure. The presence of these oxygen-containing functional groups makes graphene oxide negatively charged, while erythritol contains a large number of alcohol hydroxyl groups. During the formation of the composite phase change material, the liquid containing graphene oxide increases the interfacial area and acts as a nucleating agent, thereby inducing heterogeneous nucleation of the liquid containing erythritol, that is, the hydroxyl groups in graphene oxide form hydrogen bonds with the hydroxyl groups in erythritol, and induce erythritol to form "seed crystals" similar to the solid structure of erythritol on the surface of graphene oxide. At the same time, graphene oxide reduces the degree of freedom of erythritol, thereby reducing the supercooling degree of the composite phase change material. In addition, if the content of the graphene oxide thermal conductive material is too low, it is easy to cause the state of the composite phase change material before shaping to be unstable, and if the content of the graphene oxide thermal conductive material is too high, it is easy to cause cracking of the composite phase change material. Therefore, the above-mentioned composite phase change material of the present application can solve the problems of high supercooling degree and poor thermal conductivity of the erythritol-based phase change material. And graphene oxide is a material with excellent electrical conductivity, making the composite phase change material have excellent electrical conductivity.

[0108] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite phase change material, characterized in that, The composite phase change material consists of 94 - 96% erythritol and 4 - 6% graphene oxide by mass percentage; The particle size of the composite phase change material is 100 - 400 nm.

2. The composite phase change material according to claim 1, wherein The mass ratio of the graphene oxide to the erythritol is 1:16 - 1:

20.

3. A preparation method of the composite phase change material according to claim 1 or 2, characterized in that, The preparation method includes: Step S1, mixing erythritol, graphene oxide and a solvent to obtain a mixture; Step S2, drying and homogenizing the mixture to obtain the composite phase change material.

4. The preparation method according to claim 3, characterized in that, Step S1 includes stirring or ultrasonicating the erythritol, the graphene oxide and the solvent to obtain the mixture.

5. The preparation method according to claim 4, wherein, The frequency of the ultrasonicating is 50 - 200 Hz.

6. The preparation method according to claim 4, characterized in that, The time of the ultrasonicating is 4 - 6 h.

7. The preparation method according to claim 4, characterized in that, The rotation speed of the stirring is 800 - 1200 r / min.

8. The preparation method according to claim 4, characterized in that, The time of the stirring is 5 - 10 h.

9. The preparation method according to claim 3, characterized in that, The particle size of the graphene oxide is 300 - 600 nm.

10. The preparation method according to claim 9, wherein, The particle size of the graphene oxide is 300 - 400 nm.

11. The preparation method according to claim 3, characterized in that, The solvent is selected from any one or a combination of water, methanol, ethanol, and acetone.

12. The preparation method according to claim 11, characterized in that, The solvent is a mixed solution of ethanol and water.

13. The preparation method according to claim 12, characterized in that, The volume ratio of the ethanol to the water in the mixed solution is 2 - 6:1 - 3.

14. The preparation method according to claim 13, characterized in that, The volume ratio of the ethanol to the water in the mixed solution is 3 - 6:

1.

15. The preparation method according to claim 3, characterized in that, The homogenizing is grinding.

16. The preparation method according to claim 3, characterized in that, The temperature of the drying is 50 - 100 °C.

Images