Gallium-based alloy composite working medium and preparation method thereof

Abstract

The invention relates to the technical field of heat exchange, and particularly discloses a gallium-based alloy composite working medium and a preparation method thereof.The gallium-based alloy composite working medium comprises a main heat transfer fluid and nano particles dispersed in the main heat transfer fluid, and the main heat transfer fluid is liquid gallium-based alloy; the nano particle comprises a metal core, a non-metal shell layer coated outside the metal core and a carbon nano material layer coated outside the non-metal shell layer. The carbon nanomaterial is modified on the surface of the non-metal shell layer, the dispersion condition of nanoparticles in liquid metal is effectively improved, and meanwhile, the carbon nanomaterial can effectively mask silicon hydroxyl on the surface of the non-metal shell layer and prevent self-polymerization tendency between the non-metal shell layers by modifying the surface of the non-metal shell layer.

Description

Technical Field

[0001] This invention relates to the field of heat exchange technology, and in particular to a gallium-based alloy composite working fluid and its preparation method. Background Technology

[0002] With the rapid advancement of electronic technology, miniaturization and integration are increasingly becoming the development direction of microelectronic devices such as chips. However, this also means a sharp increase in their heat generation and power. Therefore, improving the overall heat dissipation capacity of chips has attracted increasing attention from researchers. Among them, heat pipes, as a highly efficient heat transfer element, have excellent performance in the field of heat transfer and heat dissipation technology and are now widely used in chip thermal management. However, in traditional heat pipe heat dissipation applications, the selected working medium is often a single working medium, such as pure water or methanol. These working media operate within a specific temperature range, which not only has certain limitations but also becomes increasingly inadequate to meet the ever-increasing heat dissipation demands. In order to further improve the heat dissipation efficiency and adaptability of thermal management, researchers have begun to explore the use of composite working media as a new type of working medium for thermal management.

[0003] Limited by the low thermal conductivity of traditional base fluids such as pure water, even when high-thermal-conductivity nanoparticles are loaded onto pure water as a composite working fluid, the overall thermal conductivity of the fluid remains low. Furthermore, the aggregation and sedimentation of nanoparticles in low-surface-tension base fluids also restricts their application. Liquid metals, typically alloyed with metals such as gallium, bismuth, indium, tin, and zinc, possess significant low melting points and exhibit both fluid and metallic properties at room temperature. Compared to fluids like pure water, they offer advantages such as a wider liquid temperature range and higher thermal conductivity. Therefore, using liquid metals as the base fluid for composite working fluids can significantly improve the overall thermal conductivity of thermal management. Incorporating specific nanoparticles into liquid metals can further enhance the thermal conductivity of the composite working fluid. Thus, the incorporation of nanoparticles into liquid metals as a composite working fluid for thermal management has attracted considerable attention from researchers.

[0004] Generally, due to the high cost of gallium and indium, copper and silver nanoparticles are typically chosen as fillers to reduce the overall cost of the composite working fluid while further improving thermal conductivity. However, gallium, the main component of liquid metal, has a significant corrosive effect on most metals. Directly adding metal nanoparticles to liquid metal causes severe corrosion of the nanoparticles by gallium, and the corrosion rate increases significantly with the temperature of the working fluid. This corrosion causes the composition of the liquid metal to deviate from the eutectic alloy point, resulting in alloy solidification, severely affecting its fluidity, and causing a decrease in thermal conductivity.

[0005] To address this issue, some researchers have opted to coat metal nanoparticles with a core-shell structure to isolate them from corrosion. For example, CN104124031A discloses a magnetic nano-metal fluid and its preparation method, which involves coating magnetic nanoparticles with a nano-silica shell to prevent oxidation and corrosion of the magnetic nanoparticles by the liquid metal, thus improving the stability of the magnetic nano-metal fluid. However, the surface tension of liquid metal is much greater than that of pure water, meaning that the nano-silica shell structure results in poor wettability between the nanoparticles and the liquid metal, making it difficult for them to penetrate the liquid metal. While some researchers have chosen to introduce oxygen to partially oxidize the liquid metal, forming oxides to reduce surface tension and improve wettability with the nanoparticles, the high viscosity of the metal oxides inevitably leads to poor flowability and decreased thermal conductivity in this composite working fluid.

[0006] Some technicians have also improved compatibility by modifying liquid metals to directly connect them to a non-metallic shell. For example, CN111383812 A discloses a novel liquid metal magnetic fluid and its preparation method. It uses polydopamine as the shell for magnetic nanoparticles and cleverly employs thiol surfactants to modify the liquid metal, aiming to directly connect the core-shell structured nanoparticles with the liquid metal. This avoids corrosion of the magnetic nanoparticles by the liquid metal in the non-metallic shell structure while enhancing the wettability between the nanoparticles and the liquid metal. However, liquid metals are essentially atomic fluids, and the modification effect of organic surfactants is significantly reduced, and the modification rate is difficult to control. Summary of the Invention

[0007] Based on this, the purpose of this invention is to provide a gallium-based alloy composite working medium and its preparation method, which modifies the surface of a non-metallic shell layer with carbon nanomaterials, effectively improving the dispersion of nanoparticles in liquid metal. At the same time, by modifying the surface of the non-metallic shell layer, the carbon nanomaterials can effectively mask the silanol groups on its surface and prevent the self-aggregation tendency between the non-metallic shell layers.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The present invention first provides a gallium-based alloy composite working fluid, which includes a main heat transfer fluid and nanoparticles dispersed in the main heat transfer fluid. The main heat transfer fluid is a liquid gallium-based alloy, and the nanoparticles include a metal core, a non-metallic shell layer covering the metal core, and a carbon nanomaterial layer covering the non-metallic shell layer.

[0009] This invention modifies the surface of a non-metallic shell layer with carbon nanomaterials, which effectively improves the dispersion of nanoparticles in liquid metal. At the same time, by modifying the surface of the non-metallic shell layer, the carbon nanomaterials can effectively mask the silanol groups on the surface and prevent the self-aggregation tendency between the non-metallic shell layers.

[0010] As a further improvement to the above-mentioned solution of the present invention, the liquid gallium-based alloy is an alloy prepared by gallium with at least one of indium, tin, bismuth, lead, and zinc.

[0011] As a further improvement to the above-described solution of the present invention, the metal core is one of copper nanoparticles, aluminum nanoparticles, iron nanoparticles, silver nanoparticles, and gold nanoparticles. Considering thermal conductivity and cost, copper nanoparticles are preferably used as the metal core. To achieve good flowability of the composite working fluid and a good outer shell coating effect, the size of the copper nanoparticles is 20-500 nm.

[0012] As a further improvement to the above-described scheme of the present invention, the thickness of the non-metallic outer shell layer is 2-20 nm, and the non-metallic outer shell layer is prepared from one of silicon dioxide, metal-organic framework (MOF), carbon nitride, and polymer materials. Based on considerations of simplicity and cost, the non-metallic outer shell layer is preferably prepared using silicon dioxide.

[0013] As a further improvement to the above-described scheme of the present invention, the thickness of the carbon nanomaterial layer is 1-100 nm, and the carbon nanomaterial layer is prepared from one of graphene, carbon nanotubes, and graphite. Considering ease of surface treatment and modification, the carbon nanomaterial layer is preferably prepared using carbon nanotubes.

[0014] As a further improvement to the above-described solution of the present invention, the carbon nanotubes are modified carbon nanotubes, and the preparation method of the modified carbon nanotubes includes the following steps: S11. Disperse carbon nanotubes in an acid solution, heat, filter, wash, dry, and then disperse in deionized water to obtain a dispersion. S12. Add a solution containing a metal precursor to the dispersion, heat to react, wash and dry to obtain modified carbon nanotubes.

[0015] As a further improvement to the above-described scheme of the present invention, in step S12, the metal precursor is one of a metal carbonate precursor, a metal hydroxide precursor, or a metal carboxylate complex. Considering reaction efficiency, the metal precursor is preferably a metal carboxylate complex, and the metal is copper.

[0016] This invention also provides a method for preparing the gallium-based alloy composite working medium as described above, which includes the following steps: S21. A non-metallic outer shell layer is prepared on the outside of metal particles by sol-gel method to obtain a metal core coated with a non-metallic outer shell layer; S22. Disperse carbon nanomaterials in ethanol, then add silane coupling agent and the metal core coated by the non-metallic shell layer, mix evenly, heat and stir, and then perform post-treatment to obtain nanoparticles; S23. The nanoparticles are added to a liquid gallium-based alloy and heated and stirred to obtain a gallium-based alloy composite working medium.

[0017] As a further improvement to the above-mentioned scheme of the present invention, in step S22, the silane coupling agent is at least one of 3-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane, or is a hydrolysis-condensation oligomer of at least two of 3-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0018] As a further improvement to the above-mentioned solution of the present invention, in step S22, the heating and stirring is carried out at 60-100°C for 0.51 h; and / or, in step S23, the heating and stirring is carried out at 180-200°C for 2-2.5 h.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention modifies the surface of a non-metallic shell layer with carbon nanomaterials, effectively improving the dispersion of nanoparticles in liquid metal. At the same time, by modifying the surface of the non-metallic shell layer, the carbon nanomaterials can effectively mask the silanol groups on the surface of the non-metallic shell layer, preventing the self-aggregation tendency between the non-metallic shell layers. Meanwhile, the non-metallic shell layer is used to isolate the liquid metal from the corrosive effect on the metal core.

[0020] This invention first loads a metal onto carbon nanotubes, then grafts modified carbon nanotubes onto the surface of a non-metallic shell using a silane coupling agent modified on their surface. The corrosion of the liquid metal on the metal forms an intermetallic compound, meaning the carbon nanotubes act as an intermediary to directly connect the nanoparticles to the liquid metal. This significantly improves the wettability between the carbon nanotubes / nanoparticles and the liquid metal, allowing them to mix well into the liquid metal and enhance thermal conductivity. A significant increase in thermal conductivity is achieved without altering the fluid properties of the composite working fluid. Furthermore, the modification of the silica-metal nanoparticle surface with carbon nanotubes effectively prevents nanoparticle aggregation caused by the self-polymerization of silanol groups. Applying the nanoparticles of this invention to anhydrous liquid metal also effectively prevents the decrease in nanoparticle dispersibility caused by the hydrolysis of the silane coupling agent. Attached Figure Description

[0021] Figure 1This is a flowchart illustrating a method for preparing a gallium-based alloy composite working medium according to an embodiment of the present invention. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] Example Reference Figure 1 The method for preparing a gallium-based alloy composite working medium proposed in this embodiment includes the following steps: S1. Preparation of silica-coated copper nanoparticles Preparation of microemulsion: Dissolve 0.05 mol of polyoxyethylene hexadecyl (4) ether in 100 mL of cyclohexane and stir to form a uniform water-in-oil microemulsion; Preparation of copper nanoparticle microemulsion: Add 4 mL of 0.6 mol / L copper sulfate aqueous solution to the water-in-oil microemulsion and stir until homogeneous; then add 4 mL of 2.7 mol / L ammonia solution and continue stirring and aging for 10-30 min to obtain a uniformly dispersed copper nanoparticle microemulsion. Preparation of silica-coated shell: 20 mL of pure tetraethyl orthosilicate (TEOS) was added dropwise to the copper nanoparticle microemulsion as a silicon source and stirred until homogeneous. Then, 15 mL of ammonia water with a molar concentration of 2.7 mol / L was added to the resulting mixture to hydrolyze TEOS to generate silica, thus obtaining silica-coated copper nanoparticles.

[0025] S2. Preparation of modified carbon nanotubes Carbon nanotubes were acidified by reacting them with a mixture of sulfuric acid and nitric acid (volume ratio of sulfuric acid to nitric acid 3:1) at 70 °C for 2 hours. The reaction was followed by cooling, filtration, washing, and drying to obtain acidified carbon nanotubes with a sufficient number of oxygen-containing functional groups on their surface. Subsequently, a metal precursor solution was prepared by mixing copper chloride and sodium acetate at a molar ratio of 1:2. The acidified carbon nanotubes were then mixed with the metal precursor solution at a mass ratio of 1:1 and stirred and heated at 200 °C for 2 hours. The mixture was then cooled, filtered, washed, and dried to obtain copper-modified carbon nanotubes.

[0026] S3. Preparation of Nanoparticles The modified carbon nanotubes obtained in S2 were added to ethanol and shaken to disperse them fully. Then, 3-aminopropyltriethoxysilane and the silicon dioxide-coated copper nanoparticles from step S1 were added. The mixture was heated to 85°C and stirred for 1 hour. After cooling, filtration, washing and drying, nanoparticles were obtained.

[0027] S4. Preparation of gallium-based alloys According to the mass fraction ratio: 62.5% gallium, 21.5% indium, and 16% tin are placed in a glove box and heated to melt under the protection of an inert atmosphere to fully mix them, thus obtaining a gallium-based alloy.

[0028] S5. Preparation of composite working fluid The nanoparticles obtained in step S3 are added to liquid gallium-based metal, heated to 200°C and stirred for 2 hours, and then cooled to obtain the desired gallium-based alloy composite working medium.

[0029] Comparative Example 1 The difference between this comparative example and the embodiment is that step S3 is not performed in this comparative example. In the preparation of the composite working fluid, the silicon dioxide-coated copper nanoparticles obtained in step S1 and the modified carbon nanotubes prepared in step S2 are added together to the molten gallium-based metal for preparation.

[0030] Comparative Example 2 The difference between this comparative example and the embodiment is that the preparation method of the modified carbon nanotubes in step S2 of this comparative example is as follows: Carbon nanotubes are acidified with mixed acid, then cooled, filtered, washed and dried to generate a sufficient number of oxygen-containing functional groups on the surface of the carbon nanotubes, thus obtaining modified carbon nanotubes.

[0031] Comparative Example 3 The difference between this comparative example and the embodiment is that steps S2 and S3 are not performed in this comparative example. In the preparation of the composite working fluid, the silicon dioxide-coated copper nanoparticles obtained in step S1 are added to molten gallium-based metal for preparation.

[0032] The thermal conductivity of the gallium-based alloy composite working fluids prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the test results are shown in Table 1.

[0033] Table 1 Thermal conductivity test results

[0034] The results in Table 1 show that: Compared with Comparative Example 3 (where the nanoparticles did not form a modified carbon nanotube layer), the example modified the surface of the silica particles with acidified carbon nanotubes before adding them to the liquid metal, which can effectively improve the thermal conductivity.

[0035] Meanwhile, the thermal conductivity values ​​of Comparative Example 1 and Comparative Example 2 demonstrate that introducing copper onto the surface of carbon nanotubes to form an intermetallic compound with gallium can effectively improve the wettability between carbon nanotubes and the liquid metal matrix and improve the dispersion of nanoparticles therein, resulting in a significant increase in thermal conductivity.

[0036] The difference in thermal conductivity between the examples and the comparative examples shows that when modified carbon nanotubes are applied to the surface of nano-silica particles, gallium corrodes the metal on the surface of the carbon nanotubes, forming an intermetallic compound. The formation of the intermetallic compound can greatly enhance the wettability between the nanoparticles and the liquid metal, and the formation of the carbon nanotube-nano-silica hybrid filler system also has a positive effect on improving the thermal conductivity of the composite working fluid.

[0037] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A gallium-based alloy composite working substance, characterized in that, The nanofluid comprises a main heat transfer fluid and nanoparticles dispersed in the main heat transfer fluid, the main heat transfer fluid is a liquid gallium-based alloy, and the nanoparticles comprise a metal inner core, a nonmetallic outer shell layer coated outside the metal inner core, and a carbon nanomaterial layer coated outside the nonmetallic outer shell layer.

2. The gallium-based alloy composite working substance according to claim 1, characterized in that, The liquid gallium-based alloy is an alloy prepared from gallium and at least one of indium, tin, bismuth, lead, and zinc.

3. The gallium-based alloy composite working substance of claim 1, wherein, The metal inner core is one of a copper nanoparticle, an aluminum nanoparticle, an iron nanoparticle, a silver nanoparticle, and a gold nanoparticle.

4. The gallium-based alloy composite working substance of claim 1, wherein, The nonmetallic outer shell layer has a thickness of 2-20 nm and is prepared from one of silicon dioxide, a metal-organic framework, carbon nitride, and a polymer material.

5. The gallium-based alloy composite working fluid of claim 1, wherein, The carbon nanomaterial layer has a thickness of 1-100 nm and is prepared from one of graphene, a carbon nanotube, and graphite.

6. The gallium-based alloy composite working fluid of claim 5, wherein, The carbon nanotube is a modified carbon nanotube, and a preparation method of the modified carbon nanotube comprises the following steps: S11. dispersing the carbon nanotube in an acid solution, heating, filtering and washing, drying, and then dispersing in deionized water to obtain a dispersion liquid; S12. adding a solution containing a metal precursor to the dispersion liquid, heating and reacting, washing and drying to obtain the modified carbon nanotube.

7. The gallium-based alloy composite working fluid of claim 6, wherein, In step S12, the metal precursor is one of a metal carbonate precursor, a metal hydroxide precursor, and a metal carboxylate complex.

8. A method of producing a gallium-based alloy composite working medium as claimed in any one of claims 1 to 7, characterized in that, The method comprises the following steps: S21. preparing a nonmetallic outer shell layer outside a metal particle by a sol-gel method to obtain a metal inner core coated with a nonmetallic outer shell layer; S22. dispersing a carbon nanomaterial in ethanol, then adding a silane coupling agent and the metal inner core coated with the nonmetallic outer shell layer, uniformly mixing, heating and stirring, and post-treatment to obtain nanoparticles; S23. adding the nanoparticles to a liquid gallium-based alloy, heating and stirring to obtain a gallium-based alloy composite working medium.

9. The method of claim 8, wherein the gallium-based alloy composite working fluid is prepared by the steps of: preparing a gallium-based alloy composite working fluid by mixing gallium, indium, and germanium; and adding a small amount of silver to the gallium-based alloy composite working fluid. In step S22, the silane coupling agent is at least one of 3-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane, or a hydrolysis-condensation oligomer of at least two of 3-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

10. The method of claim 8, wherein the gallium-based alloy composite working fluid is prepared by the steps of: preparing a gallium-based alloy composite working fluid by mixing gallium, indium, and germanium; and adding a small amount of silver to the gallium-based alloy composite working fluid. In step S22, the heating and stirring is at 60-100 ℃ for 0.5-1 h; and / or, in step S23, the heating and stirring is at 180-200 ℃ for 2-2.5 h.

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