Liquid metal powder and preparation method thereof

Abstract

The present invention discloses a liquid metal powder, comprising a liquid metal and a carbide formed on its surface, wherein the raw material of the carbide is anhydrous ethanol, and the mass ratio of the anhydrous ethanol to the liquid metal is 10:90-98:2. The powder has good dispersion stability and can effectively prevent the oxidation of the liquid metal. The present invention also provides a method for preparing a magnetic liquid metal powder, comprising adding anhydrous ethanol and a liquid metal to containers A and B respectively, and continuously introducing an inert gas; adding the anhydrous ethanol in container A to container B, wherein the mass ratio of the anhydrous ethanol to the liquid metal is 10:90-98:2, adjusting the pressure of container B to 0.1-0.2MPa, and heating and stirring container B to obtain a magnetic liquid metal powder. The preparation method is simple and efficient.

Description

Technical Field

[0001] The invention belongs to the field of flexible electronics, and in particular relates to liquid metal powder and a preparation method and application thereof. Background Art

[0002] Gallium and one or more metals with low melting points such as indium, tin and zinc can form eutectic alloys such as gallium-indium or gallium-indium or gallium-indium-tin-zinc, which are liquid in the temperature range near room temperature and are also called gallium-based liquid alloys. Gallium-based liquid alloys have high electrical conductivity (106S / m) and good fluidity and deformation properties at room temperature, so they are of great significance in the fields of self-healing circuits, flexible or integrated electronics.

[0003] The melting point of gallium indium tin alloy ranges from 5 to 30 degrees Celsius. The melting point of gallium indium tin alloy can be adjusted according to customer requirements to achieve different melting points and characteristics. Due to the low toxicity and low reactivity of the raw material metal of gallium indium tin alloy, gallium indium tin alloy can replace toxic liquid mercury and many other potential applications.

[0004] Flexible electronics is an emerging electronic technology that makes electronic devices on flexible substrates. It has the advantages of bendability, stretchability, and lightweight, and has developed rapidly in recent years. However, the existing flexible electronic manufacturing technology is relatively complicated, from the preparation of conductive functional materials to the production process of flexible electronics, as well as the subsequent processing of products, with high time costs, equipment costs, and raw material costs. Liquid metals such as gallium-indium alloys are liquid at room temperature, have good fluidity, high conductivity, and low cost, and are ideal functional materials for flexible electronic manufacturing technology. The direct writing liquid metal method is used to manufacture flexible electronic products, which is convenient and efficient, has low equipment requirements, is highly flexible, and has broad application prospects.

[0005] The main methods for preparing liquid metal-based circuits include screen printing, direct writing, transfer printing, inkjet and laser printing technology. Laser printers can be used to quickly and in large quantities to prepare micron-scale circuits with complex patterns. This requires first preparing liquid metal powders with controllable particle size, stable structure and good dispersibility.

[0006] Liquid metal has a large surface tension and is easy to agglomerate and form large particles during storage. There are generally two strategies to obtain magnetic liquid metal powder materials. One is to prepare liquid metal particles first, then place the liquid metal particles in micro-nano particles and roll them or use electroplating to coat a layer of metal film on the surface of the liquid metal, and then wash and dry them. Another strategy is to use surfactants to modify the surface of liquid metal particles to improve the dispersion stability of the particles. The liquid metal particles prepared by the first strategy have a larger particle size, generally in the millimeter level, and low yield; the liquid metal particles prepared by the second strategy can have a particle size as low as nanometers, but can only be stored in a solution. When the surfactant is dried, it can no longer maintain the shape of the liquid metal particles, so they merge and grow into large particles. Therefore, the liquid metal particles prepared by these two strategies have problems such as low yield, agglomeration after drying, merging and growth, and structural stability. Summary of the invention

[0007] The invention provides a liquid metal powder, which has good dispersion stability and can effectively prevent the oxidation of the liquid metal.

[0008] A liquid metal powder comprises liquid metal and carbide formed on the surface thereof. The raw materials of the liquid metal powder are carbon-containing organic solvent and liquid metal. The mass ratio of the carbon-containing organic solvent to the liquid metal is 10:90-98:2.

[0009] If the amount of carbon-containing organic solvent is too small, the carbides formed in the liquid metal are small and cannot completely cover the liquid metal droplets; or the formed carbide layer is too thin to stabilize the larger liquid metal droplets, which collide and merge to form large particles during the stirring process. When an excessive amount of carbon-containing organic solvent is added, the carbon-containing organic solvent forms a large amount of carbides in the liquid metal, thereby reducing the relative content of liquid metal in the liquid metal powder and affecting its thermal and electrical conductivity.

[0010] The liquid metal is one or more of mercury (Hg), gallium (Ga), gallium-indium (GaIn) alloy, gallium-indium-tin (GaInSn), or gallium-indium-tin-zinc (GaInSnZn).

[0011] The transition metal oxide has good chemical stability and oxidation resistance and does not chemically react with liquid metal, thus having good chemical stability.

[0012] The carbon-containing organic solvent is ethanol, n-hexane or isopropanol.

[0013] The particle size of the liquid metal powder particles is 2um-220um.

[0014] The liquid metal powder is a kind of soft particle. Through mechanical sintering, pressure and other processes, the liquid metal inside the soft particle flows out to connect the surrounding particles together to form a conductive path, which can be used for the self-repairing circuit of flexible electronic devices.

[0015] The present invention also provides a method for preparing liquid metal powder, comprising:

[0016] (1) Adding a carbon-containing organic solvent and a liquid metal into containers A and B respectively, and continuously introducing an inert gas;

[0017] (2) Adding the carbon-containing organic solvent in container A into container B, wherein the mass ratio of the carbon-containing organic solvent to the liquid metal is 10:90-98:2, adjusting the pressure of container B to 0.1-0.2 MPa, and heating and stirring container B to obtain magnetic liquid metal powder.

[0018] Inert gas is introduced to remove air and moisture from the reaction system, as well as dissolved oxygen and water molecules in the carbon-containing organic solvent. During the heating and stirring process, the carbon-containing organic solvent undergoes a chemical reaction to form carbides that are adsorbed on the surface of the liquid metal. The carbides adsorbed on the surface of the liquid metal separate the liquid metal into small droplets, and finally form liquid metal powder particles. Compared with surface-coated polymers, the carbides formed by in-situ chemical reactions using anhydrous ethanol stabilize the liquid metal droplets, which has less pollution and impact on the liquid metal, and the liquid metal powder has a strong dispersion.

[0019] In step (1):

[0020] The container B is a multi-interface device, which is provided with a gas filling port, a gas exhaust port and a stirring port.

[0021] Furthermore, the multi-interface device is a three-necked bottle, a four-necked bottle or a glove box.

[0022] The inert gas is one or more of nitrogen, argon or helium.

[0023] In step (2):

[0024] The heating temperature is 0-100°C.

[0025] The stirring parameters are: stirring time is 0-24h, stirring rate is 0-1000rpm, and stirring mode is one or both of mechanical stirring and magnetic stirring.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) Since the carbide has excellent antioxidant and corrosion resistance, can avoid reaction with liquid metal to cause liquid metal denaturation, and can be adsorbed in the grooves on the surface of liquid metal particles, the liquid metal powder provided by the present invention has high chemical stability and dispersibility. After being placed for two months, there is still no agglomeration and it has good dispersibility.

[0028] (2) Due to the high boiling point and low saturated vapor pressure of liquid metal, liquid metal powder can be used in higher temperature environments.

[0029] (3) The preparation method of the liquid metal powder provided by the present invention is prepared under an inert gas atmosphere, which can effectively prevent the oxidation of the liquid metal, and the liquid metal powder with good dispersion stability and adjustable particle size can be obtained through a simple stirring process. The preparation method is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a method for preparing liquid metal powder according to a specific embodiment, wherein 1 is a magnetic heating stirrer, 2 is a nitrogen bottle, 3 is a nitrogen inlet pipe, 4 is a three-necked flask, 5 is liquid metal, 6 is a glass heating dish, and 7 is generated liquid metal particles;

[0031] Figure 2 This is a physical photo of the liquid metal powder obtained in Example 1;

[0032] Figure 3 This is a SEM image of the liquid metal powder obtained in Example 1;

[0033] Figure 4 is the XRD spectrum of the liquid metal powder prepared in Example 1;

[0034] Figure 5 is the Raman spectrum of the liquid metal powder obtained in Example 1;

[0035] Figure 6 This is a physical photo of the liquid metal powder obtained in Example 2;

[0036] Figure 7 This is a SEM image of the liquid metal powder obtained in Example 2;

[0037] Figure 8 is the XRD spectrum of the liquid metal powder obtained in Example 2;

[0038] Fig. 9 is the Raman spectrum of the liquid metal powder obtained in Example 2;

[0039] Fig.10 This is a real photo of the liquid metal powder obtained in Example 3;

[0040] Fig.11 This is a SEM image of the liquid metal powder obtained in Example 3;

[0041] Fig.12 The XRD spectrum of the liquid metal powder prepared in Example 3;

[0042] Fig.13 This is the Raman spectrum of the liquid metal powder prepared in Example 3. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments described below are part of the embodiments of the present invention, rather than all of the embodiments. Given the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] In this embodiment, the liquid metal used is a gallium-indium eutectic alloy, and the ethanol is anhydrous ethanol of analytical grade, wherein the mass ratio of ethanol to the gallium-indium eutectic alloy 5 is 1.5:1.

[0046] according to Figure 1 As shown, gallium-indium eutectic alloy 5 is added to the container according to the mass ratio, and nitrogen is introduced to remove air and moisture in the reaction system. The air and oxygen dissolved in ethanol are removed in advance, ethanol is injected into the reaction container, the outlet valve is closed, and the reaction container is heated to 60°C and stirred. The reaction container is cooled to room temperature to obtain liquid metal powder;

[0047] The specific method is as follows:

[0048] Step 1: Accurately weigh 2 g of gallium-indium alloy 5 and add it into a three-necked flask 4;

[0049] Step 2: Connect the middle opening of the three-necked bottle 4 to the stirring device, the right opening to the air inlet pipe 3, and the left opening to the air outlet pipe. Seal and check the air tightness. Open the air inlet and outlet valves, and introduce nitrogen to remove air and moisture in the system. Nitrogen is provided by nitrogen bottle 2;

[0050] Step 3: Add anhydrous ethanol into a three-necked flask to remove dissolved oxygen and water in the anhydrous ethanol (the device is the same as step 2);

[0051] Step 4: Accurately measure 3 g of deoxygenated anhydrous ethanol and inject it into the three-necked flask in step 2.

[0052] Step 5: Heat the mixed system to 60° C. using a water bath, start stirring using a magnetic heating stirrer 1, and stir for 24 hours until all the liquid metal reacts to form black particles;

[0053] Step 6: Remove the glass heating dish 6 and cool to room temperature to obtain gallium-indium alloy powder 7.

[0054] like Figure 2 As shown, the gallium-indium alloy powder provided in this embodiment is black powder, and no droplets of liquid metal are observed to precipitate;

[0055] like Figure 3 As shown, the gallium-indium alloy powder provided in this embodiment is uniform in size, the average size of the powder particles is 5-7 μm, no agglomeration occurs, and the dispersion is good;

[0056] like Figure 4 As shown, the gallium-indium eutectic alloy phase can be observed from the XRD pattern;

[0057] like Figure 5 As shown, the absorption peak of carbon was observed from the Raman spectrum, and the absorption peak of ethanol did not appear, indicating that ethanol reacted with the gallium-indium alloy to form carbides and coated on the surface of the gallium-indium alloy while maintaining the stability of the particle shape;

[0058] The gallium-indium alloy powder provided in this embodiment did not agglomerate after being placed for 2 months and had good dispersibility.

[0059] Example 2

[0060] In this embodiment, isopropanol is of analytical grade, and the liquid metal is gallium-indium eutectic alloy 5. The mass ratio of isopropanol to gallium-indium eutectic alloy 5 is 1.5:1. Accurately weigh 3.0g of isopropanol and 2.0g of gallium-indium alloy, add them into a three-necked flask 4 respectively, and pass nitrogen to remove the air in the system. Add isopropanol to gallium-indium alloy 5, heat to 30°C, stir for 24 hours, and cool to room temperature;

[0061] The liquid metal powder 7 contains unreacted gallium-indium alloy droplets and gallium-indium particles, and the size of the gallium-indium particles is in the range of 220-5 μm.

[0062] like Figure 6 As shown, the gallium-indium alloy powder provided in this embodiment is black powder, and no droplets of liquid metal are observed to precipitate;

[0063] like Figure 7 As shown, the gallium-indium alloy powder provided in this embodiment is uniform in size, the average size of the powder particles is 220-5 μm, no agglomeration occurs, and the dispersion is good;

[0064] like Figure 8 As shown, the gallium-indium eutectic alloy phase can be observed from the XRD pattern;

[0065] like Fig. 9As shown, the absorption peak of carbon was observed from the Raman spectrum, and the absorption peak of isopropanol did not appear, indicating that isopropanol reacted with the gallium-indium alloy to form carbides and coated on the surface of the gallium-indium alloy while maintaining the stability of the particle shape;

[0066] Example 3

[0067] In this embodiment, n-hexane is of analytical grade, and the liquid metal is gallium-indium eutectic alloy 5. The mass ratio of n-hexane to gallium-indium eutectic alloy 5 is 15:1. Accurately weigh 30.0 g of n-hexane and 2.0 g of gallium-indium alloy 5, add them into a three-necked flask 4 respectively, and pass nitrogen to remove the air in the system. Add n-hexane to gallium-indium alloy 5, heat to 80°C, stir for 24 hours, and cool to room temperature;

[0068] The gallium-indium alloy in the liquid metal powder 7 is completely reacted to form particles, and the particle size range is 200-2 μm.

[0069] like Fig.10 As shown, the gallium-indium alloy powder provided in this embodiment is black powder, and no droplets of liquid metal are observed to precipitate;

[0070] like Fig.11 As shown, the gallium-indium alloy powder provided in this embodiment is uniform in size, the average size of the powder particles is 200-2 μm, no agglomeration occurs, and the dispersion is good;

[0071] like Fig.12 As shown, the gallium-indium eutectic alloy phase can be observed from the XRD pattern;

[0072] like Fig.13 As shown, the absorption peak of carbon was observed from the Raman spectrum, and the absorption peak of n-hexane did not appear, indicating that n-hexane reacted with the gallium-indium alloy to form carbide and coated the surface of the gallium-indium alloy while maintaining the stability of the particle shape.

Claims

1. A liquid metal powder, characterized in that: It includes liquid metal and carbide formed on its surface, wherein the raw materials of the liquid metal powder are carbon-containing organic solvent and liquid metal, and the mass ratio of the carbon-containing organic solvent to the liquid metal is 10:90-98:2; The carbon-containing organic solvent is ethanol, n-hexane or isopropanol; The method for preparing the liquid metal powder comprises: (1) Add the carbon-containing organic solvent and liquid metal into containers A and B respectively, and continuously introduce inert gas; (2) adding the carbon-containing organic solvent in container A to container B, wherein the mass ratio of the carbon-containing organic solvent to the liquid metal is 10:90-98:2, adjusting the pressure of container B to 0.1-0.2 MPa, and heating and stirring container B to obtain magnetic liquid metal powder; In step (2), the heating temperature is 30-80°C; In step (2), the stirring parameters are: stirring time is 24 h, stirring rate is 0-1000 rpm, and stirring method is one or both of mechanical stirring and magnetic stirring.

2. The liquid metal powder according to claim 1, characterized in that: The liquid metal is one or more of mercury, gallium, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy.

3. The liquid metal powder according to claim 1, characterized in that: The particle size of the liquid metal powder particles is 2 um - 220 um.

4. The method for preparing liquid metal powder according to claim 1, characterized in that: In step (1), the container B is a multi-interface device, and the multi-interface device is provided with a gas filling port, a gas exhaust port and a stirring port.

5. The method for preparing liquid metal powder according to claim 4, characterized in that: The multi-interface device is a three-necked bottle, a four-necked bottle or a glove box.

6. The method for preparing liquid metal powder according to claim 1, characterized in that: In step (1), the inert gas is one or both of argon and helium.

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