A preparation method of graphene-enhanced low-melting-point metal phase-change composite material

Abstract

The present invention belongs to the technical field of phase change materials. It relates to a method for preparing a graphene-enhanced low-melting-point metal phase change composite material, comprising the following steps: 1) preparing a honeycomb graphene aerogel; 2) cutting the graphene aerogel into a desired shape and placing it into a customized graphite mold, placing the filled mold into a graphite sleeve, and placing a low-melting-point metal block on top of the mold to form a complete mold; 3) placing the mold prepared in step 2) in the induction heating area of ​​a pressure infiltration furnace, evacuating the furnace body, and heating and insulating the mold under vacuum conditions; 4) injecting high-purity argon gas to pressurize and inflate the furnace; 5) stopping heating, cooling the furnace to room temperature, removing the mold and demolding it to obtain a graphene-enhanced low-melting-point metal phase change composite material. This method achieves high reliability, high thermal conductivity, and high energy storage density of low-melting-point metal phase change materials, and has broad application prospects in the fields of thermal management and energy storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change materials, and in particular relates to a method for preparing a graphene-enhanced low-melting-point metal phase change composite material. Background Art

[0002] Solid-liquid phase change materials (SLCMs) can achieve significant energy absorption or release through the transition between their solid-liquid states, and have significant application prospects in areas such as electronic device thermal management, solar energy utilization, and waste heat recovery. SLCMs can be categorized as organic and inorganic. Organic PCMs primarily include organic compounds such as hydrocarbons and alcohols. They have low density and high phase change enthalpy per unit mass, but their low intrinsic thermal conductivity (0.1-0.2 W / mK) limits their application. Low-melting-point PCMs within inorganic PCMs refer to metals such as gallium, indium, bismuth, and tin, and their alloys with elements such as lead, cadmium, and zinc in varying proportions, with melting points below 300°C. These materials possess high thermal conductivity (10-61 W / mK) and high energy storage density, making them ideal passive thermal management materials, thermal interface materials, and phase change energy storage materials.

[0003] However, low-melting-point phase change metals have good fluidity in the liquid phase and are prone to leakage, leading to metal corrosion and electrical short circuits. They cannot be used alone as thermal management materials and heat storage materials. There are currently two main approaches to solve the leakage problem: one is to use encapsulation technology to wrap low-melting-point phase change metal particles in a shell to form phase change microcapsules, and then use the microcapsules as fillers and mix them with an organic matrix to form a composite material. However, this process requires heating and melting the metal in water or an organic solvent, so it is only suitable for metals with lower melting points. In addition, this method will introduce additional interfaces while solving the liquid metal leakage problem, and the proportion of microcapsules added to the composite material is limited, resulting in low thermal conductivity and energy storage density of the composite material. The thermal conductivity is only 0.45~3.23W / mK, and the energy storage density is only 71.73~126.72J / cm 3 , such as the literature Deng C, Zhang X, Peng J, et al.In 51 Bi 32.5 Sn 16.5@SiO2 microcapsules-based composite phase change materials with high thermal conductivity and heat storage density for electronics thermal management[J].Journal of Energy Storage,2024,86:111432 and the literature Wang S,Zhao X,Wang Z,et al.Micro-encapsulation of a low-melting-point alloy phase change material and its application in electronic thermal management[J].Journal of Cleaner Production,2023,417:138058; The second method is to composite porous materials with low-melting-point metals through a vacuum infiltration process, using the capillary force of the pores to restrict the flow of liquid metal after phase change, providing it with shaping ability. Currently used porous materials include metal foams and flexible organic foams, but metal foams react with liquid metals to form intermetallic compounds, and flexible organic foams have low thermal conductivity and are easily deformed. Therefore, the performance of phase change composites prepared from both types of foams has significant room for improvement. Therefore, there is an urgent need to find new processes to obtain low-melting-point metal-based phase change composite materials with high reliability, high thermal conductivity and high energy storage density. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a graphene-reinforced low-melting-point metal phase change composite material. By using a rigid graphene aerogel with through honeycomb pores as a reinforcing phase and utilizing a gas pressure infiltration process to prepare a graphene / metal composite material, a graphene-reinforced low-melting-point metal phase change composite material with high reliability, high thermal conductivity and high energy storage density is obtained.

[0005] The technical solution of the present invention is:

[0006] A method for preparing a graphene-reinforced low-melting-point metal phase-change composite material comprises the following steps:

[0007] 1) adding graphene powder and a dispersant to deionized water, mixing them evenly and then dispersing them by ultrasonication, then adding sodium alginate and dissolving it completely to obtain a sodium alginate sol in which the graphene powder is stably dispersed; transferring the sol to a mold, spraying a gelling agent evenly on the upper surface of the sol, standing the sol until gelation is complete, and demolding the sol to obtain a hydrogel; freeze-drying the hydrogel to remove water, and then removing organic matter by high-temperature debinding to obtain a honeycomb graphene aerogel;

[0008] 2) cutting the graphene aerogel into the desired shape and placing it in a customized graphite mold, placing the filled mold in a graphite sleeve and placing a low-melting-point metal block on top of the mold to make a complete mold;

[0009] 3) placing the mold prepared in step 2) in the induction heating area of ​​a pressure impregnation furnace, evacuating the furnace body, and heating and keeping the mold warm under vacuum conditions;

[0010] 4) Injecting high-purity argon gas to pressurize the furnace, so that the liquid metal penetrates into the pores of the graphene aerogel in the mold under the action of the high-pressure gas;

[0011] 5) Stop heating, cool to room temperature in the furnace, remove the mold and demould to obtain a graphene-enhanced low-melting-point metal phase change composite material.

[0012] Furthermore, in step 1), the mass of the graphene powder is 0.5-3% of the mass of water, and the concentration of sodium alginate is 0.5-2%.

[0013] Furthermore, the dispersant in step 1) is one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol and polyethylene oxide-polypropylene oxide copolymer, and the mass of the dispersant is 5-10% of the mass of the graphene powder.

[0014] Furthermore, the gelling agent in step 1) is one or more of calcium chloride, copper chloride, copper sulfate, nickel chloride, nickel nitrate, cobalt chloride or ferrous chloride solution, the solution concentration is 1-4 mol / L, and the gelling reaction time is 4-10 h.

[0015] Furthermore, the freeze drying in step 1) is to freeze dry the hydrogel at -60°C and 1 Pa for 30 h to 72 h, preferably 36 h to 48 h.

[0016] Furthermore, step 1) performs high-temperature debinding in a tubular furnace or a vacuum heat treatment furnace, the debinding atmosphere is an inert gas or a vacuum environment, the debinding temperature is 600-650° C., and the debinding time is 3-5 hours.

[0017] Furthermore, the graphene aerogel used in step 2) is composed of oriented graphene nanosheets and highly interconnected honeycomb pores, with a pore size of 20 to 200 μm, a graphene volume fraction of 2 to 10%, and a porosity of 90 to 98%.

[0018] Further, the low melting point metal used in step 2) includes one or more of gallium, indium, bismuth, tin, gallium-aluminum alloy, gallium-indium alloy, gallium-bismuth alloy, gallium-tin alloy, gallium-indium-tin alloy, indium-bismuth alloy, indium-tin alloy, indium-cadmium alloy, indium-bismuth-tin alloy, indium-bismuth-cadmium alloy, bismuth-tin alloy, bismuth-cadmium alloy, bismuth-tin-cadmium alloy, bismuth-lead-cadmium alloy, bismuth-tin-lead alloy, bismuth-tin-zinc alloy, tin-lead alloy, tin-zinc alloy, tin-cadmium-lead alloy, indium-bismuth-tin-lead alloy, bismuth-tin-lead-cadmium alloy, and lead-antimony alloy.

[0019] Furthermore, in step 3), the vacuum degree is lower than 0.1 Pa.

[0020] Furthermore, in step 3), the heating temperature of the mold is 100-350° C., and the holding time is 5-30 minutes.

[0021] Furthermore, in step 4), the gas pressure in the furnace is 0.5-2.0 MPa.

[0022] The present invention relates to a graphene-enhanced low-melting-point metal phase-change composite material obtained by the preparation method, wherein the volume fraction of graphene in the graphene-enhanced low-melting-point metal phase-change composite material is 2-10%.

[0023] Compared with other technologies, the outstanding advantages of the present invention are:

[0024] The graphene-enhanced low-melting-point metal phase-change composite material prepared by the present invention has high reliability. The micron-scale pores of the graphene aerogel limit the leakage of liquid metal through capillary force. In addition, the bionic honeycomb graphene aerogel has high compressive strength and compression modulus, which enables the composite material to have a certain resistance to compression deformation after the metal is melted, thereby further improving the reliability of the composite material.

[0025] The graphene-enhanced low-melting-point metal phase-change composite material prepared by the present invention has excellent thermal and electrical conductivity. The graphene aerogel and the low-melting-point metal form a dual-continuous thermal and electrical conductive path, eliminating the adverse effects of the interface on carrier scattering. In addition, the directionally arranged graphene nanosheets can further improve the out-of-plane thermal and electrical conductivity of the composite material.

[0026] The graphene-enhanced low-melting-point metal phase-change composite material prepared by the present invention has a high energy storage density. The porosity of the graphene aerogel used is 90-98%, and the pores are all through holes. Combined with the air pressure infiltration process, the phase-change metal can be densely filled inside the aerogel, ensuring that the phase-change metal has the highest possible volume fraction and reducing the loss of the composite material's energy storage density.

[0027] Compared with the microencapsulation process, the process used in the present invention has the following advantages: a wide range of applications, and composite materials can be prepared using low-melting-point metals of any composition; product performance is adjustable, and the mechanical properties, thermal conductivity, and phase change properties of the composite material can be regulated by changing the volume fraction of graphene to meet the needs of different scenarios; no additional interfaces and organic matter need to be introduced, and the thermal conductivity and energy storage density are high.

[0028] Compared with the existing porous material packaging process, the present invention uses honeycomb graphene aerogel as the packaging material, which has the following advantages:

[0029] Compared with the metal foam encapsulation process, graphene aerogel has small pore size, strong capillary force and low liquid metal leakage rate; graphene does not react with liquid metal, and the long-term performance stability of the composite material is better.

[0030] Compared with the flexible organic foam packaging process, rigid graphene aerogel has higher specific strength and specific modulus, is not easy to deform, and the composite material is more reliable after the metal melts; the thermal conductivity and electrical conductivity of graphene aerogel are much higher than those of organic foam, and the composite material has better thermal and electrical conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings used in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a scanning electron microscope surface image of the graphene aerogel prepared in Example 1 of the present invention;

[0033] Figure 2 This is a scanning electron microscope cross-sectional image of the graphene aerogel prepared in Example 1 of the present invention;

[0034] Figure 3 This is a scanning electron microscope surface image of the graphene aerogel / Wood's metal composite material prepared in Example 1 of the present invention;

[0035] Figure 4 This is a scanning electron microscope cross-sectional image of the graphene aerogel / Wood's metal composite material prepared in Example 1 of the present invention;

[0036] Figure 5 Graph comparing the macroscopic morphologies of the graphene aerogel / Wood's alloy composite material and Wood's alloy prepared in Example 1 of the present invention before (A) the phase transition at 25°C and after (B) the phase transition at 100°C. DETAILED DESCRIPTION

[0037] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated, and they can be combined with each other to achieve better technical effects.

[0038] The present invention relates to a method for preparing a graphene-reinforced low-melting-point metal phase-change composite material. A rigid graphene aerogel having through honeycomb pores is used as a reinforcement. The method is prepared by a gas pressure infiltration method. The method comprises the following steps:

[0039] 1) adding graphene powder and a dispersant to deionized water, mixing them uniformly by magnetic stirring, and then ultrasonically dispersing them in an ice bath, then adding sodium alginate, and completely dissolving the sodium alginate by magnetic stirring at room temperature to obtain a sodium alginate sol in which the graphene powder is stably dispersed; transferring the sol to a mold, spraying a gelling agent evenly on the upper surface of the sol, standing the sol until gelation is complete, and demolding the sol to obtain a hydrogel; freeze-drying the hydrogel to remove water, and then removing organic matter by high-temperature debinding to obtain a honeycomb graphene aerogel with good pore penetration and excellent compressive performance;

[0040] 2) Cutting the graphene aerogel into the desired shape and placing it in a custom graphite mold, placing the filled mold in a graphite sleeve and placing a low-melting-point metal block on top of the mold to make a complete mold;

[0041] 3) placing the obtained mold in the induction heating area of ​​a pressure impregnation furnace, evacuating the furnace body, and heating and keeping the mold obtained in step 2) warm under vacuum conditions;

[0042] 4) Injecting high-purity argon gas to pressurize the furnace, so that the liquid metal penetrates into the pores of the graphene aerogel in the mold under the action of the high-pressure gas;

[0043] 5) Stop heating, cool to room temperature in the furnace, remove the mold and demould to obtain a graphene-enhanced low-melting-point metal phase change composite material.

[0044] In this process, debinding refers to keeping the material warm for a period of time under certain temperature and atmosphere conditions to allow the organic matter to volatilize and be discharged (the organic matter here refers to alginate, polyvinyl pyrrolidone, etc.).

[0045] The low melting point metal used in step 2) includes one or more of gallium, indium, bismuth, tin, gallium-aluminum alloy, gallium-indium alloy, gallium-bismuth alloy, gallium-tin alloy, gallium-indium-tin alloy, indium-bismuth alloy, indium-tin alloy, indium-cadmium alloy, indium-bismuth-tin alloy, indium-bismuth-cadmium alloy, bismuth-tin alloy, bismuth-cadmium alloy, bismuth-tin-cadmium alloy, bismuth-lead-cadmium alloy, bismuth-tin-lead alloy, bismuth-tin-zinc alloy, tin-lead alloy, tin-zinc alloy, tin-cadmium-lead alloy, indium-bismuth-tin-lead alloy, bismuth-tin-lead-cadmium alloy, and lead-antimony alloy.

[0046] Example 1

[0047] To prepare graphene aerogel, first disperse 0.2g of graphene powder and 0.02g of polyvinyl pyrrolidone in 20mL of deionized water by magnetic stirring, and then ultrasonically disperse them in an ice bath for 3h to further improve the dispersibility of graphene. Add 0.1g of sodium alginate to the dispersion and stir magnetically for 2h to completely dissolve the sodium alginate. Transfer the sol to a mold, spray 10mL of 2mol / L calcium chloride solution on the upper surface of the sol, let it stand for 6h, and demold after the sol gelation is completed to obtain a hydrogel. Freeze-dry the hydrogel at -60℃ and 1Pa for 36h, and then debind at 620℃ under argon protection for 3h to obtain a rigid graphene aerogel with through honeycomb pores. The micromorphology of the sample was characterized by scanning electron microscopy, and its surface image and cross-sectional image are shown as follows. Figure 1 and Figure 2 As shown, the prepared graphene aerogel has hexagonal honeycomb pores, and the pores have good vertical penetration.

[0048] The graphene aerogel is cut and loaded into the mold, and then the loaded mold is placed in the graphite sleeve, and the melting point of the graphene aerogel is 70℃ and the composition is Bi 50 Pb 26.7 Sn 13.3 Cd 10 , a Wood's alloy block with a thermal conductivity of 20.3W / mK is placed on the upper part of the mold, and the entire filled mold is placed in the induction heating zone of the air pressure impregnation furnace, and the vacuum system and the pressurized inflation system are connected. Turn on the vacuum system and evacuate the furnace body until the vacuum degree is less than 0.1Pa. Turn on the circulating water, start the induction heater, heat the mold to 130°C and keep it warm for 30 minutes. Turn on the pressurized inflation system to inject high-purity argon into the furnace. When the gas pressure in the furnace reaches 1.0MPa, turn off the pressurized inflation system. Stop heating, turn off the circulating water when the furnace temperature drops to room temperature, take out the mold and demold it, and obtain a circular sheet of graphene aerogel / Wood's alloy composite material product with a diameter of 20mm and a thickness of 4mm. The micromorphology of the sample was characterized by a scanning electron microscope, and its surface image and cross-sectional image are shown as follows. Figure 3 and Figure 4As shown in the figure, the honeycomb skeleton structure of the graphene aerogel in the composite material is intact, the alloy phase is densely filled inside the aerogel, and the interface between the two is well bonded. The thermal conductivity of the prepared graphene aerogel / Wood's alloy composite material is 33.5W / mK, the graphene volume fraction is 4.0%, and the density is 9.2g / cm 3 , the energy storage density is 374.6J / cm 3 .

[0049] Figure 5 The macroscopic morphologies of the prepared graphene aerogel / Wood's alloy composite material and Wood's alloy at 25°C and 100°C are compared. It can be seen that at 100°C, the appearance of Wood's alloy changes significantly due to the melting of the alloy, while the appearance of the composite material does not change significantly at 100°C, indicating that graphene aerogel can provide excellent shaping effects for low-melting-point metals at temperatures above their melting points.

[0050] Example 2

[0051] To prepare graphene aerogel, 0.6g of graphene powder and 0.06g of polyethylene glycol were first dispersed in 30mL of deionized water by magnetic stirring, and then ultrasonically dispersed in an ice bath for 3h to further improve the dispersibility of graphene. 0.3g of sodium alginate was added to the dispersion and magnetically stirred for 3h to completely dissolve the sodium alginate. The sol was transferred to a mold, and 20mL of a 3mol / L calcium chloride solution was sprayed on the upper surface of the sol. The sol was allowed to stand for 5h. After the sol gelation was completed, it was demolded to obtain a hydrogel. The hydrogel was freeze-dried at -60℃ and 1Pa for 48h, and then debonded at 600℃ in a vacuum environment for 3h to obtain a rigid graphene aerogel with through honeycomb pores.

[0052] The graphene aerogel is cut and loaded into the mold, and then the loaded mold is placed in the graphite sleeve, and the melting point of the graphene aerogel is 138 ° C and the composition is Bi 58 Sn 42A bismuth-tin alloy block with a thermal conductivity of 18.7W / mK is placed on top of the mold, and the entire filled mold is placed in the induction heating zone of the furnace. The vacuum system and the pressurized gas system are connected. Turn on the vacuum system and evacuate the furnace until the vacuum degree is less than 0.1Pa. Turn on the circulating water, start the induction heater, heat the mold to 200℃ and keep it warm for 20 minutes. Turn on the pressurized gas system to inject high-purity argon gas into the furnace. When the gas pressure in the furnace reaches 1.0MPa, turn off the pressurized gas system. Stop heating, turn off the circulating water when the furnace temperature drops to room temperature, take out the mold and demold it, and obtain a circular graphene aerogel / bismuth-tin alloy composite product with a diameter of 20mm and a thickness of 4mm. The honeycomb skeleton structure of the graphene aerogel in this composite material is intact, the alloy phase is densely filled inside the aerogel, and the interface between the two is well bonded. The thermal conductivity of the prepared graphene aerogel / bismuth-tin alloy composite material is 39.0 W / mK, the graphene volume fraction is 7.9%, and the density is 8.1 g / cm 3 , the energy storage density is 356.6J / cm 3 .

[0053] Example 3

[0054] To prepare graphene aerogel, 0.1g of graphene powder and 0.01g of polyvinyl alcohol were first dispersed in 20mL of deionized water by magnetic stirring, and then ultrasonically dispersed in an ice bath for 3h to further improve the dispersibility of graphene. 0.1g of sodium alginate was added to the dispersion and magnetically stirred for 2h to completely dissolve the sodium alginate. The sol was transferred to a mold, and 5mL of 4mol / L calcium chloride solution was sprayed on the upper surface of the sol. The sol was allowed to stand for 4h. After the sol gelation was completed, it was demolded to obtain a hydrogel. The hydrogel was freeze-dried at -60℃ and 1Pa for 36h, and then debonded at 640℃ under argon protection for 3h to obtain a rigid graphene aerogel with through honeycomb pores.

[0055] The graphene aerogel is cut and loaded into the mold, and then the loaded mold is placed in the graphite sleeve, and Sn with a melting point of 190 ° C and a composition of 86 Bi 14A bismuth-tin alloy block with a thermal conductivity of 33.4W / mK is placed on the top of the mold, and the entire filled mold is placed in the induction heating zone of the furnace, and the vacuum system and the pressurized gas system are connected. Turn on the vacuum system and evacuate the furnace until the vacuum degree is less than 0.1Pa. Turn on the circulating water, start the induction heater, heat the mold to 250℃ and keep it warm for 25 minutes. Turn on the pressurized gas system to inject high-purity argon into the furnace. When the gas pressure in the furnace reaches 1.2MPa, turn off the pressurized gas system. Stop heating, turn off the circulating water when the furnace temperature drops to room temperature, take out the mold and demold it, and obtain a circular graphene aerogel / bismuth-tin alloy composite product with a diameter of 20mm and a thickness of 4mm. The honeycomb skeleton structure of the graphene aerogel in this composite material is intact, the alloy phase is densely filled inside the aerogel, and the interface between the two is well bonded. The thermal conductivity of the prepared graphene aerogel / bismuth-tin alloy composite material is 38.5 W / mK, the graphene volume fraction is 2.1%, and the density is 7.5 g / cm 3 , the energy storage density is 276.1J / cm 3 .

[0056] Although several embodiments of the present invention have been described herein, those skilled in the art will appreciate that modifications may be made to the embodiments herein without departing from the spirit of the present invention. The above embodiments are merely exemplary and should not be used as limitations on the scope of the present invention.

Claims

1. A method for preparing a graphene-reinforced low-melting-point metal phase change composite material, comprising the following steps: 1) adding graphene powder and a dispersant to deionized water, mixing them evenly and then ultrasonically dispersing them, then adding sodium alginate and dissolving it completely to obtain a sodium alginate sol in which the graphene powder is stably dispersed; transferring the sol to a mold, spraying a gelling agent evenly on the upper surface of the sol, standing the sol until gelation is complete, and demolding the sol to obtain a hydrogel; freeze-drying the hydrogel to remove water, and then removing organic matter by high-temperature debinding to obtain a honeycomb graphene aerogel; wherein the mass of the graphene powder is 0.5-3% of the mass of the water, and the concentration of the sodium alginate is 0.5-2%; the dispersant is one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide-polypropylene oxide copolymer, and the mass of the dispersant is 5-10% of the mass of the graphene powder; the gelling agent is one or more of calcium chloride, copper chloride, copper sulfate, nickel chloride, nickel nitrate, cobalt chloride, or ferrous chloride solution, and the solution concentration is 1-4 mol / L; 2) cutting the graphene aerogel into the desired shape and placing it in a customized graphite mold, placing the filled mold in a graphite sleeve and placing a low-melting-point metal block on top of the mold to make a complete mold; 3) placing the mold prepared in step 2) in the induction heating area of ​​a pressure impregnation furnace, evacuating the furnace body, and heating and keeping the mold warm under vacuum conditions; 4) injecting high-purity argon gas to pressurize and inflate the furnace, so that the liquid metal penetrates into the pores of the graphene aerogel in the mold under the action of the high-pressure gas; 5) stopping heating, cooling the furnace to room temperature, and then removing the mold to obtain a graphene-enhanced low-melting-point metal phase change composite material.

2. The preparation method according to claim 1, wherein The gel reaction time in step 1) is 4 to 10 hours.

3. The preparation method according to claim 1, wherein In step 1), high-temperature debinding is performed in a tubular furnace or a vacuum heat treatment furnace. The debinding atmosphere is an inert gas or a vacuum environment. The debinding temperature is 600-650° C. and the debinding time is 3-5 hours.

4. The preparation method according to claim 1, wherein The graphene aerogel used in step 2) is composed of oriented graphene nanosheets and highly interconnected honeycomb pores, with a pore size of 20 to 200 μm, a graphene volume fraction of 2 to 10%, and a porosity of 90 to 98%.

5. The preparation method according to claim 1, wherein The low melting point metal used in step 2) includes one or more of gallium, indium, bismuth, tin, gallium-aluminum alloy, gallium-indium alloy, gallium-bismuth alloy, gallium-tin alloy, gallium-indium-tin alloy, indium-bismuth alloy, indium-tin alloy, indium-cadmium alloy, indium-bismuth-tin alloy, indium-bismuth-cadmium alloy, bismuth-tin alloy, bismuth-cadmium alloy, bismuth-tin-cadmium alloy, bismuth-lead-cadmium alloy, bismuth-tin-lead alloy, bismuth-tin-zinc alloy, tin-lead alloy, tin-zinc alloy, tin-cadmium-lead alloy, indium-bismuth-tin-lead alloy, bismuth-tin-lead-cadmium alloy, and lead-antimony alloy.

6. The preparation method according to claim 1, wherein The vacuum degree in step 3) is lower than 0.1 Pa, the heating temperature in step 3) is 100-350° C., and the holding time is 5-30 min.

7. The preparation method according to claim 1, wherein The gas pressure in the furnace in step 4) is 0.5-2.0 MPa.

8. The graphene-reinforced low-melting-point metal phase-change composite material obtained by the preparation method according to any one of claims 1 to 7, wherein: The volume fraction of graphene in the graphene-enhanced low-melting-point metal phase-change composite material is 2-10%.

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