Gallium-based liquid metal composite material and preparation method and application thereof

Abstract

The invention discloses a gallium-based liquid metal composite material, which is prepared from the following components in parts by weight: 10 to 30 parts of elastomer, 65 to 95 parts of oxidized gallium-based liquid metal and 1 to 5 parts of Ti < 3 > C < 2 > T < x > MXene. By controlling the oxidation rate of the gallium-based liquid metal, the mobility of the gallium-based liquid metal can be effectively reduced, the gallium-based liquid metal is prevented from leaking in the composite material, and the flexibility is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of modified polymer materials, and particularly to a gallium-based liquid metal composite material, a preparation method thereof, and an application thereof. Background Art

[0002] With the high integration and miniaturization of electronic components, the power consumption of electronic devices is getting higher and higher, and a large amount of heat is released during operation. If the heat cannot be conducted out in time, it will cause the working temperature of the components to be high, directly damaging their lifespan and working stability. Thermal interface materials are used to improve the heat conduction between electronic components and heat sinks, mainly including two types: thermal grease and heat sink pads. Thermal grease is usually composed of silicone oil and heat-conducting fillers (such as alumina, boron nitride), filling tiny gaps and reducing thermal resistance, but traditional silicone oil interface materials are prone to the risk of overflow. Heat sink pads are preformed solid materials containing a silicone or rubber matrix and heat-conducting fillers, which are easy to install and suitable for irregular surfaces, but their thermal conductivity far from meets the current usage requirements.

[0003] Liquid metals have become a new choice for developing high-performance thermal interface materials due to their high thermal conductivity, resistance to aging, and easy processing characteristics. However, liquid metals have liquid fluidity, and liquid metals have metal corrosion and high electrical conductivity, making them at risk of leakage and causing damage and short circuits to electronic components during use, which severely limits the application of liquid metals. Developing leak-proof high-performance liquid metal-based thermal interface materials is a major issue nowadays. An ideal thermal interface material is required to have not only excellent thermal conductivity and stability but also good mechanical properties to maintain good contact between the heater and the heat sink. Polymer materials are widely used as the base materials of thermal interface materials due to their excellent mechanical properties and processability. Liquid metal-polymer composites, especially liquid metal-elastomer composites, thus have great application potential. However, although the existing liquid metal high thermal conductivity gaskets have excellent thermal conductivity, the gasket stability is poor, and many problems caused by liquid metal leakage seriously affect the development of high thermal conductivity gaskets.

[0004] Moreover, with the diversification of the application scenarios of heat sink pads, new heat sink pads with multiple functions have attracted wide attention. Among them, new liquid metal-elastomer composite heat sink pads with both thermal management and electromagnetic interference (EMI) shielding functions are widely used in fields such as consumer electronics, communication equipment, automotive electronics, and aerospace.

[0005] Although the existing liquid metal-polymer composite heat sink pads meet the application requirements to a certain extent, they still have the following deficiencies: Poor heat conduction: Liquid metals are dispersed in the polymer matrix. Due to the barrier effect of the polymer, heat sink pads often exhibit low thermal conductivity and are difficult to meet the heat conduction requirements of current high heat-generating electronic components.

[0006] Liquid metal leakage: Liquid metal composed of atoms has high surface energy, surface tension and fluidity of the liquid. This results in poor interaction and wetting behavior between liquid metal and substrate materials, and between liquid metal and thermal conductive fillers, making it difficult to limit the leakage of liquid metal. Moreover, the phenomenon of liquid metal leakage is more significant under external stimuli, such as thermal expansion, stress stimulation, etc. Therefore, threats such as metal corrosion and circuit short - circuit caused by liquid metal leakage severely limit the research and application of liquid metal - polymer composite thermal pads.

[0007] Insufficient flexibility: Gaskets with insufficient flexibility have poor conformability and cannot fully fill the tiny gaps between electronic components and heat sinks, resulting in a reduced interfacial contact area, an increased thermal resistance, and a decreased heat dissipation efficiency.

[0008] Lack of multifunctionality: As electronic devices develop towards high - power, high - integration, and miniaturization, single - function thermal conductive materials are difficult to meet the requirements of complex application scenarios. The necessity of developing multifunctional thermal pads stems from the comprehensive requirements of modern electronic devices for thermal management and material properties. Multifunctional thermal pads can significantly improve device performance and reliability by integrating properties such as thermal conductivity, electromagnetic shielding, insulation, and flexibility. Summary of the Invention

[0009] The purpose of the present invention is to overcome the above - mentioned technical defects and provide a gallium - based liquid metal composite material with good thermal conductivity, good electromagnetic shielding, flexibility, and no liquid metal leakage, as well as its preparation method and application.

[0010] The present invention is achieved through the following technical solutions: A gallium - based liquid metal composite material, by weight, comprises the following components: 10 - 30 parts of elastomer; 65 - 95 parts of oxidized gallium - based liquid metal; Ti3C2T x 1 - 5 parts of MXene.

[0011] Preferably, in the oxidized gallium - based liquid metal, the oxidation rate of the gallium - based liquid metal is 3 - 34%.

[0012] In the gallium-based liquid metal composite material of the present invention, the relative oxidation rate of the oxidized gallium-based liquid metal can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, etc. The content of the elastomer can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc.; the content of the oxidized gallium-based liquid metal can be 65 parts, 66 parts, 67 parts, 68 parts, 69 parts, 70 parts, 71 parts, 72 parts, 73 parts, 74 parts, 75 parts, 76 parts, 77 parts, 78 parts, 79 parts, 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, etc. Ti3C2T x The content of Ti3C2Tx MXene can be 1.0 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2.0 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, 3.0 parts, 3.1 parts, 3.2 parts, 3.3 parts, 3.4 parts, 3.5 parts, 3.6 parts, 3.7 parts, 3.8 parts, 3.9 parts, 4.0 parts, 4.1 parts, 4.2 parts, 4.3 parts, 4.4 parts, 4.5 parts, 4.6 parts, 4.7 parts, 4.8 parts, 4.9 parts, 5.0 parts, etc.

[0013] The described elastomer is selected from one or more of block polyamide resin (Pebax), polyurethane elastomer (PU, TPU), aminated natural rubber, fluororubber, and polyurea elastomer. By selecting the above-mentioned polar elastomers in the present invention, the bonding property between the gallium-based liquid metal and the elastomer can be improved, and the leakage risk can be reduced.

[0014] The described gallium-based liquid metal is selected from gallium, or an alloy of gallium and one or more of indium, tin, zinc, bismuth, and aluminum. Specifically, it can be elemental gallium, gallium-indium alloy, gallium-tin alloy, gallium-indium-tin alloy, gallium-zinc alloy, gallium-aluminum alloy, and other gallium-based multi-element alloys.

[0015] Those skilled in the art can modify the gallium-based liquid metal composite material of the present invention without affecting the thermal conductivity and electromagnetic shielding performance. By weight, 0 - 1 part of a surfactant, such as stearic acid, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, etc., can be added to reduce the surface tension of the liquid metal and promote the dispersion of liquid metal droplets.

[0016] The preparation method of the gallium-based liquid metal composite material of the present invention includes the following steps: Step A: Preparation of Ti3C2T x MXene powder: According to the ratio, lithium fluoride (LiF) and concentrated hydrochloric acid are stirred and mixed to obtain an etching solution, and then Ti3AlC2 powder is added to the etching solution and etched at 40 - 50 °C to obtain a dispersion; then the dispersion is centrifugally precipitated (the rotation speed range of the centrifuge can be 3000 - 4000 revolutions per minute), and then the supernatant is removed, and deionized water is added for dispersion and washing; the above centrifugation - washing process is repeated until the pH of the supernatant is between 5.5 and 6.0, and then the supernatant is separated; deionized water is added again to obtain a dispersion, and ultrasonic peeling and dispersion are carried out under the protection of an inert gas (such as nitrogen, argon, helium, etc.) to obtain Ti3C2T x MXene suspension; finally, through centrifugal stratification (the rotation speed range of the centrifuge can be 3000 - 4000 revolutions per minute), the upper liquid is taken and freeze-dried (the temperature range is -50~-80 °C) to obtain Ti3C2T x MXene powder; Step B: In an oxygen-containing atmosphere (oxygen, air, nitrogen / oxygen mixture, etc.), the temperature range is 0 - 60 °C, and the relative humidity range is 20 - 60%, stir the gallium-based liquid metal for 20 - 50 min to obtain a liquid metal - metal oxide premix; Step C: According to the ratio, add 6 - 10 times the weight of water to the Ti3C2T x MXene powder to obtain a MXene colloidal dispersion after dispersion; mix the MXene colloidal dispersion with the liquid metal - metal oxide premix and stir for 2 - 10 hours (the stirring speed > 500 revolutions per minute), under the condition of an oxygen-containing atmosphere (oxygen, air, nitrogen / oxygen mixture, etc.), the temperature range is 0 - 60 °C, and the relative humidity range is 20 - 60%, to obtain an oxidized liquid metal filler (i.e., a mixture of oxidized gallium-based liquid metal and Ti3C2T x MXene); Step D: Dissolve the elastomer in a solvent, and according to the ratio, add the oxidized liquid metal filler for homogeneous dispersion emulsification (the rotation speed is greater than 5000 revolutions per minute, and the time is 200 - 500 seconds) to obtain a homogeneous composite, and then pour it into a mold and let it stand to volatilize the solvent until it is shaped; Step E: Form by a hot press, the temperature is 170 - 220 °C (selected according to the melting point of the elastomer), and the pressure is 5 - 20 MPa to obtain the gallium-based liquid metal composite material.

[0017] In step A, the mass ratio of LiF / concentrated hydrochloric acid / Ti3AlC2 is (1 - 3):(16 - 26):1, and the concentration range of concentrated hydrochloric acid is 9 - 12 mol / L.

[0018] In step D, the solvent is selected from one or more of hexafluoroisopropanol, formic acid, chloroform, dichloromethane, and methanol. The choice and addition amount of the solvent are to dissolve the elastomer, and the boiling point is lower than 100 °C, which is easy to volatilize or evaporate.

[0019] Step D can also be a twin-screw extruder extrusion granulation method, and the barrel temperature range is 170-220 °C.

[0020] In step C, in Ti3C2T x The main purpose of adding 6-10 times the weight of water to the MXene powder is to fully disperse the Ti3C2T x MXene powder. Another purpose is that the presence of water will accelerate the oxidation of the gallium-based liquid metal. Through several hours of stirring, heat will be generated by friction between the liquid metals. During this period, water will participate in oxidation or evaporation, so most of the water will participate in metal oxidation and be consumed. At this time, compared with Ti3C2T x The total weight increase of the MXene powder and the initial gallium-based liquid metal is the oxygen content, so it is called the relative oxidation rate of the oxidized gallium-based liquid metal. The calculation method is: (weight of the oxidized gallium-based liquid metal - initial weight of the gallium-based liquid metal) ÷ initial weight of the gallium-based liquid metal × 100%. The physical shape of the oxidized gallium-based liquid metal is a decrease in fluidity. When applied to the elastomer, it will significantly improve the risk of gallium-based liquid metal leakage and will not affect the thermal conductivity and electromagnetic shielding performance.

[0021] After vacuum rotary distillation, the total weight of the Ti3C2T x MXene powder and the oxidized gallium-based liquid metal is almost unchanged, which indicates that there is almost no water in the product of this step.

[0022] The application of the gallium-based liquid metal composite material is used to prepare heat-conducting sheets and electromagnetic shielding materials.

[0023] The present invention has the following beneficial effects: 1. After pre-oxidation, the viscosity of the liquid metal increases significantly, and the fluidity becomes poor, restricting the fluidity of free-state metal droplets.

[0024] 2. The polar elastomer contains various polar groups such as hydroxyl, amino, and ester groups that can interact with liquid metal oxides, increasing the compatibility between the polymer matrix and the liquid metal filler; 3. MXene interacts with the liquid metal and metal oxides, restricting the fluidity of free-state metal droplets.

[0025] 4. While the gallium-based liquid metal composite material of the present invention has good electromagnetic shielding performance and thermal conductivity, it significantly improves the risk of liquid metal leakage. Brief Description of the Drawings

[0026] Figure 1 : Cross-sectional photograph of the gallium-based liquid metal composite material of Comparative Example 1. There is obvious silver-white liquid metal leakage on the shear cross-section.

[0027] Figure 2 : Cross-sectional photograph of the gallium-based liquid metal composite material of Example 2. There is no liquid metal leakage on the shear cross-section.

[0028] Figure 3 : Scanning electron microscope photograph of the gallium-based liquid metal composite material of Comparative Example 1. There are droplet-shaped liquid metals on the cross-section quenched by liquid nitrogen.

[0029] Figure 4 : Scanning electron microscope photograph of the gallium-based liquid metal composite material of Example 2. There are no droplet-shaped liquid metals on the cross-section quenched by liquid nitrogen.

[0030] Figure 5 : Photograph of the gallium-based liquid metal composite material of Comparative Example 2. A large amount of leakage will occur during the hot pressing and shaping process. Detailed Description of the Invention

[0031] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0032] The raw materials used in the present invention are as follows: Block polyamide resin: PEBAX, Arkema, France; Polyurethane elastomer: TPU, Basf, Germany; Ti3AlC2: Titanium aluminum carbide, 400 mesh, ≥ 98%, Jilin Yiyi Technology Co., Ltd.; LiF: Lithium fluoride, ≥ 99%, Shanghai Macklin Biochemical Co., Ltd.; Hexafluoroisopropanol: ≥ 99%, Shanghai Macklin Biochemical Co., Ltd.; Gallium-based liquid metal B: Gallium-indium alloy (Ga 0.75 In 0.25 ), ≥ 99.99%, Hunan Changsha Kunyong New Materials Co., Ltd.; Gallium-based liquid metal A: Gallium (Ga), ≥ 99.99%, Hunan Changsha Kunyong New Materials Co., Ltd.; Gallium-based liquid metal C: Gallium-indium-tin alloy (Ga 68.5 In 21.5 Sn10 ), ≥ 99.99%, Kunyong New Materials Co., Ltd., Changsha, Hunan Concentrated hydrochloric acid: 36.0 - 38.0%, approximately 12 mol / L, Guangzhou Chemical Reagent Factory.

[0033] Preparation method of gallium - based liquid metal composite materials in Examples and Comparative Example 1, including the following steps: Step A: Preparation of Ti3C2T x MXene powder. Mix lithium fluoride (LiF) and concentrated hydrochloric acid by stirring to obtain an etching solution, and then add Ti3AlC2 powder to the etching solution (weight ratio of lithium fluoride: concentrated hydrochloric acid: Ti3AlC2 powder = 3.2:40:2), and carry out etching at 45 °C to obtain a dispersion; then centrifuge and precipitate the dispersion at a speed of 3500 rpm, then remove the supernatant, and add deionized water for dispersion and washing; repeat the above centrifugation - washing process until the pH of the supernatant is between 5.5 and 6.0, then separate the supernatant; add deionized water again to obtain a dispersion, and carry out ultrasonic stripping and dispersion under argon protection to obtain Ti3C2T x MXene suspension; finally, centrifuge and layer at a speed of 3500 rpm, take the upper liquid and freeze - dry it at - 80 °C to obtain Ti3C2T x MXene powder. Step B: In air (temperature 25 °C, relative humidity 50%), stir the gallium - based liquid metal (the addition amount is shown in the table) at a speed of 500 rpm for 30 min to obtain a liquid metal - metal oxide premix. Step C: According to the ratio, add 8 times the weight of water to Ti3C2T x MXene powder (the addition amount is shown in the table) to obtain a MXene colloidal dispersion after dispersion; mix the MXene colloidal dispersion with all the liquid metal - metal oxide premixes obtained in Step B, and rapidly stir at 600 rpm for n hours (the specific time is shown in the table), under the condition of being exposed to air (temperature 25 °C, relative humidity 50%) to obtain an oxidized liquid metal filler. Step D: Dissolve the elastomer in a solvent, according to the ratio (shown in the table), and then add all the oxidized liquid metal fillers obtained in Step C, and carry out homogeneous dispersion and emulsification at 5500 rpm for 300 seconds to obtain a homogeneous composite, and then pour it into a mold and let it stand to volatilize the solvent until it is shaped. Step E: Form by a hot press, with a temperature of 190 °C and a pressure of 10 MPa to obtain a gallium - based liquid metal composite material.

[0034] Testing methods for each item: (1) Thermal conductivity: Refer to ASTM D5470, and use a Hotdisk TPS 2500S thermal constant analyzer to measure the thermal conductivity (heat transfer coefficient) of the heat - conducting sheets prepared in Examples 1 - 7 and Comparative Example 1.

[0035] (2) Electromagnetic shielding property: Referring to the ASTM D4935 standard, a Keysight N5224B vector network analyzer was used to test the electromagnetic shielding effects of Examples 1 to 7 and Comparative Example 1.

[0036] (3) Liquid metal leakage characterization: The gallium-based liquid metal composite material was hot-pressed into a sheet material with a specification of 20 mm × 10 mm × 1 mm, cut, and placed for 2 hours at 25 °C and a relative humidity of 50%, and then observed for liquid metal leakage.

[0037] Table 1: Parameters and test results of the gallium-based liquid metal composite materials in Examples 1-5

[0038] As can be seen from Examples 1-3, when the relative oxidation rate of the gallium-based liquid metal exceeds 16%, the thermal conductivity and electromagnetic shielding performance are better.

[0039] Table 2: Parameters and test results of the gallium-based liquid metal composite materials in Examples 7-8 and Comparative Example 1

[0040] As can be seen from Comparative Example 1, when the oxidation rate of the gallium-based liquid metal is low, it is easy to cause liquid leakage, and the thermal conductivity and electromagnetic shielding properties are insufficient.

[0041] Comparative Example 2: Ti3C2T x The preparation of the MXene powder was the same as that of the example, except that the gallium-based liquid metal was not oxidized. Specifically: 3Ti3C2T x MXene powder and 75 gallium-based liquid metal A were added to hexafluoroisopropanol. After ultrasonic dispersion for 40-70 minutes, a dispersion was obtained. Then, 15 parts of Pebax were added. After the Pebax was dissolved, a homogenizing emulsifier was used at a rotation speed of 5000 rpm and mixed for 300 seconds to obtain a casting liquid. After casting into a mold and waiting for the solvent to volatilize and solidify, it was hot-pressed into a heat-conducting sheet. After testing, the thermal conductivity of Comparative Example 2 was 1.24 W / m·K, and the electromagnetic shielding effect was SE T = 22.6 dB, and a large amount of liquid leakage occurred during hot-pressing and shaping into a heat-conducting sheet.

Claims

1. A gallium-based liquid metal composite material, characterized in that: By weight, it includes the following components: Elastomer 10-30 parts; 65-95 parts of oxidized gallium-based liquid metal; Ti3C2T x MXene 1-5 parts.

2. The gallium-based liquid metal composite material according to claim 1, characterized in that: In the oxidized gallium-based liquid metal, the oxidation rate of the gallium-based liquid metal is 3-34%.

3. The gallium-based liquid metal composite material according to claim 1, characterized in that: The elastomer is selected from one or more of block polyamide resin, polyurethane elastomer, aminated natural rubber, fluororubber, and polyurea elastomer.

4. The gallium-based liquid metal composite material according to claim 1, characterized in that: The gallium-based liquid metal is selected from gallium, or an alloy of gallium and one or more of indium, tin, zinc, bismuth and aluminum.

5. The method for preparing the gallium-based liquid metal composite material according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step A: Ti3C2T x The preparation of MXene powder includes: mixing lithium fluoride and concentrated hydrochloric acid according to the ratio to obtain an etching solution, adding Ti3AlC2 powder to the etching solution, etching at 40-50°C to obtain a dispersion; then centrifuging the dispersion, removing the supernatant, adding deionized water to disperse and wash; repeating the above centrifugation-washing process until the pH of the supernatant is between 5.5 and 6.0, separating the supernatant; adding deionized water to obtain a dispersion, and performing ultrasonic stripping and dispersion under inert gas protection to obtain Ti3C2T x MXene suspension; finally, the upper layer of liquid was freeze-dried by centrifugation to obtain Ti3C2T x MXene powder; Step B: In an atmosphere containing oxygen, the temperature range is 0-60° C., and the relative humidity range is 20-60%, stirring the gallium-based liquid metal for 20-60 minutes to obtain a liquid metal-metal oxide premixture; Step C: According to the ratio, in Ti3C2T x 6-10 times the weight of water is added to the MXene powder, and a MXene colloidal dispersion is obtained after dispersion; the MXene colloidal dispersion is mixed with a liquid metal-metal oxide premixture, and stirred for 2-10 hours in an atmosphere containing oxygen, at a temperature range of 0-60°C, and at a relative humidity range of 20-60%, to obtain an oxidized liquid metal filler; Step D: dissolving the elastomer in a solvent, adding an oxidized liquid metal filler according to a ratio to homogenize, disperse and emulsify the elastomer to obtain a homogeneous composite, and then pouring the composite into a mold and letting it stand to evaporate the solvent until it is fixed; Step E: forming by a hot press and hot pressing to obtain a gallium-based liquid metal composite material.

6. The method for preparing the gallium-based liquid metal composite material according to claim 5, characterized in that: In step A, the mass ratio of LiF / concentrated hydrochloric acid / Ti3AlC2 is (1-3):(16-26):1, and the concentration range of concentrated hydrochloric acid is 9-12 mol / L.

7. The method for preparing the gallium-based liquid metal composite material according to claim 5, characterized in that: The oxygen-containing atmosphere is selected from at least one of oxygen, air, and nitrogen / oxygen mixed gas.

8. The method for preparing the gallium-based liquid metal composite material according to claim 5, characterized in that: The solvent is selected from one or more of hexafluoroisopropanol, formic acid, chloroform, dichloromethane and methanol.

9. The use of the gallium-based liquid metal composite material according to any one of claims 1 to 4, characterized in that: Used to prepare thermal conductive sheets and electromagnetic shielding materials.

Images