Liquid gallium-based alloy and preparation method and application thereof

Abstract

The invention provides a liquid gallium-based alloy and a preparation method and application thereof. The liquid gallium-based alloy is composed of a plurality of liquid drops, and each liquid drop comprises a liquid gallium-based alloy core and a modified coating layer arranged on the surface of the liquid gallium-based alloy core; the liquid gallium-based alloy core comprises the following components in percentage by atom: 75 to 83 at% of Ga, 13 to 17 at% of In, 0.1 to 7 at% of Sn, 0.1 to 3 at% of Zn and / or Cd, and 0.1 to 2 at% of Pb and / or Bi; the material of the modified coating layer is selected from one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, chitosan and hexadecyl trimethyl ammonium bromide; the average particle size of the liquid drops is 1-5 [mu] m, and the conductivity is greater than or equal to 3.6 * 10 < 6 > S / m. The liquid drops in the liquid gallium-based alloy are high in size uniformity and good in dispersity, agglomeration is not prone to occurring when a flexible conductive material or a flexible electronic device is prepared, and the electrical performance of the flexible conductive material or the flexible electronic device can be improved.

Description

Technical Field

[0001] This invention relates to the field of alloy preparation technology, and more specifically, to a liquid gallium-based alloy, its preparation method, and its application. Background Technology

[0002] In recent years, the rapid iteration of electronic science and technology has provided a powerful impetus for the rapid development of the wearable electronics field, and the demand for flexible electronic devices with high elasticity, stretchability, and conductivity has also been increasing. In flexible electronic devices, conductive materials are a core component, and their performance directly determines the overall performance of the device and has a crucial impact on the expansion of its application scenarios.

[0003] Currently, traditional conductive materials such as metals and graphene struggle to simultaneously meet the requirements of excellent conductivity, good flexibility, and reliable mechanical stability. In contrast, liquid metals, as an emerging material, have become the optimal choice for conductive materials—a core component of flexible electronic devices—due to their low melting point, high fluidity, high conductivity, low toxicity, and environmental friendliness. However, liquid metals still face some challenges in practical applications, such as high surface tension making it difficult to wet most surfaces, easy agglomeration, and reduced conductivity after oxidation. These factors restrict their widespread adoption in flexible electronic devices. Therefore, developing a method for preparing micron-sized liquid metal droplets for conductive stretchable materials that can effectively address these issues is of great significance for promoting the development of flexible electronics technology.

[0004] Existing literature (publication number CN119287203A) discloses a method for preparing a semi-solid metallic elastomer. This invention involves adding liquid metal to water and ultrasonically mixing it to obtain an aqueous solution of liquid metal droplet suspension particles. Then, solid metal particles are added to the aqueous solution and ultrasonically mixed to obtain a mixed suspension of the solid metal and liquid metal droplets. Finally, an acidic solution is added to the mixture to obtain semi-solid metal particles. These particles can subsequently be used to fabricate flexible conductive composite materials with both high tensile strength and high electrical conductivity. However, the liquid metal droplets produced by this method still exhibit poor size uniformity and dispersion stability.

[0005] Based on this, researching and developing a method for preparing liquid gallium-based alloys that can improve their fluidity and conductivity, as well as their dimensional uniformity and dispersion stability, is of great significance for improving the performance of flexible electronic devices. Summary of the Invention

[0006] The main objective of this invention is to provide a liquid gallium-based alloy, its preparation method, and its application, in order to solve the problems of poor fluidity and conductivity, poor size uniformity, and poor dispersion stability of liquid gallium-based alloys in the prior art.

[0007] To achieve the above objectives, the present invention provides a liquid gallium-based alloy, which comprises multiple droplets. Each droplet includes a liquid gallium-based alloy core and a modified coating layer disposed on its surface. The liquid gallium-based alloy core, by atomic percentage, comprises: 75–83 at% Ga, 13–17 at% In, 0.1–7 at% Sn, 0.1–3 at% Zn and / or Cd, and 0.1–2 at% Pb and / or Bi. The modified coating layer is selected from one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, chitosan, and hexadecyltrimethylammonium bromide. The average droplet size is 1–5 μm, and the electrical conductivity is ≥3.6 × 10⁻⁶. 6 S / m.

[0008] Furthermore, the melting point of the liquid gallium-based alloy is ≤15℃; preferably -5~15℃.

[0009] Furthermore, the weight-average molecular weight of polyvinylpyrrolidone is 10,000–58,000; the weight-average molecular weight of polyvinyl alcohol is 10,000–80,000; the weight-average molecular weight of polyethylene glycol is 2,000–20,000; and the weight-average molecular weight of chitosan is 50,000–300,000.

[0010] Furthermore, the modified coating layer comprises 5 to 20 wt% of the total weight of the liquid gallium-based alloy.

[0011] Further, based on atomic percentage, the liquid gallium-based alloy core comprises: 77–80 at% Ga, 14–16 at% In, 5–7 at% Sn, 2–3 at% Zn, and 0.5–1.5 at% Pb; or, the liquid gallium-based alloy core comprises: 77–80 at% Ga, 14–16 at% In, 5–7 at% Sn, 1–2 at% Cd, and 0.5–1.5 at% Bi; or, the liquid gallium-based alloy core comprises: 77–80 at% Ga, 14–16 at% In, 5–7 at% Sn, 1–2 at% Zn, 1–2 at% Cd, 0.5–1 at% Pb, and 0.5–1 at% Bi.

[0012] Furthermore, the liquid gallium-based alloy core includes Ga, In, Sn, Zn, Cd, Pb, and Bi, and the atomic ratio of Zn to Cd is 1:(1-3); the atomic ratio of Pb to Bi is 1:(1-2).

[0013] To achieve the above objectives, another aspect of the present invention provides a method for preparing the liquid gallium-based alloy provided in this application. The method includes: step S1, mixing elemental gallium, elemental indium, elemental tin, elemental zinc and / or elemental cadmium, and elemental lead and / or elemental bismuth to obtain a mixed metal raw material; wherein the molar ratio of elemental gallium, elemental indium, elemental tin, elemental zinc and / or elemental cadmium, to elemental lead and / or elemental bismuth is (75-83):(13-17):(0.1-7):(0.1-3):(0.1-83). 2) Step S2: Melt the mixed metal raw materials in an inert atmosphere to obtain molten material; Step S3: Cool the molten material to obtain liquid material; Step S4: Mix the liquid material, solvent and modified coating agent and sonicate to obtain suspension; The modified coating agent is selected from one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, chitosan and hexadecyltrimethylammonium bromide; Step S5: Allow the suspension to settle and centrifuge in sequence, and then dry it to obtain liquid gallium-based alloy.

[0014] Furthermore, in step S2, the inert atmosphere is selected from argon and / or nitrogen.

[0015] Furthermore, in step S2, the melting temperature is 300–500°C.

[0016] Further, step S3 includes: cooling the molten material to 20-30°C to obtain a liquid material.

[0017] Furthermore, the cooling rate is 1–3 °C / min.

[0018] Furthermore, in step S4, the modified coating agent accounts for 0.1 to 1 wt% of the weight of the suspension.

[0019] Furthermore, the weight ratio of the liquid material to the solvent is 1:(20-40).

[0020] Furthermore, the solvent is selected from one or more of water, ethanol, propylene glycol, glycerol, formic acid, and acetic acid.

[0021] Furthermore, in step S4, the ultrasonic treatment power is 400–1000W, and the time is 5–30 minutes.

[0022] Furthermore, the ultrasonic treatment is ultrasonic pulse treatment, and the ultrasonic pulse has an on time of 8s and an off time of 2s in each cycle; or, an on time of 10s and an off time of 5s; or, an on time of 20s and an off time of 10s.

[0023] Furthermore, in step S5, the settling time is 1 to 4 hours.

[0024] Furthermore, the centrifugation speed is 100–1000 rpm, and the time is 5–60 min.

[0025] Furthermore, the drying process is carried out at a temperature of 50–80°C for 2–6 hours.

[0026] Another aspect of the present invention provides an application of the liquid gallium-based alloy provided in this application in the preparation of flexible conductive materials or flexible electronic devices.

[0027] By applying the technical solution of this invention, when the five elements gallium (Ga), indium (In), tin (Sn), zinc and / or cadmium (Zn and / or Cd), and lead and / or bismuth (Pb and / or Bi) in the core of the liquid gallium-based alloy meet the aforementioned specific atomic percentage content, the electron transport enhancement properties of the heavy metal elements Pb and Bi can be utilized, resulting in a significant improvement in the electrical conductivity of the liquid gallium-based alloy compared to traditional gallium-indium alloys or gallium-indium-tin alloys. Furthermore, this liquid gallium-based alloy is liquid at room temperature and consists of multiple droplets, each droplet comprising a liquid gallium-based alloy core and a modified coating layer disposed on its surface. The modified coating layer, on the one hand, improves its dispersibility, suppressing its agglomeration and sedimentation during subsequent applications; on the other hand, it also provides passivation, enhancing the interfacial bonding force between the subsequently prepared liquid gallium-based alloy and matrix materials such as elastomers and polymers, preventing interfacial separation during the composite process of the liquid gallium-based alloy, thereby improving the success rate of conductive stretching material preparation and its mechanical-electrical synergistic properties.

[0028] The droplets in the liquid gallium-based alloy provided in this application are micron-sized droplets with high size uniformity and good dispersion. They are not prone to agglomeration during the preparation of flexible conductive materials or flexible electronic devices, and can improve their comprehensive properties such as electrical performance. Attached Figure Description

[0029] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 The diagram shows the gallium-indium-tin-zinc-lead pentagonal phase diagram corresponding to different Pb doping contents in a liquid gallium-based alloy core consisting of 76 at% Ga, 14.49 at% In, 6.51 at% Sn, and 3 at% Zn, based on atomic percentage.

[0031] Figure 2 The metallographic microstructure of the liquid gallium-based alloy prepared in Example 1 of this application is shown (magnification of 20x).

[0032] Figure 3The metallographic microstructure of the liquid gallium-based alloy prepared in Example 1 of this application is shown (magnification of 50x). Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0034] As described in the background section, existing liquid gallium-based alloys suffer from poor fluidity and conductivity, as well as poor size uniformity and dispersion stability. To address these technical problems, this application provides a liquid gallium-based alloy composed of multiple droplets. Each droplet includes a liquid gallium-based alloy core and a modified coating layer disposed on its surface. The liquid gallium-based alloy core, by atomic percentage, comprises: 75–83 at% Ga, 13–17 at% In, 0.1–7 at% Sn, 0.1–3 at% Zn and / or Cd, and 0.1–2 at% Pb and / or Bi. The modified coating layer is selected from one or more of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), chitosan (CS), and hexadecyltrimethylammonium bromide (CTAB). The average droplet size is 1–5 μm, and the conductivity is ≥3.6 × 10⁻⁶. 6 S / m.

[0035] Through theoretical calculations and extensive experimental research, the inventors creatively discovered that when the five elements gallium (Ga), indium (In), tin (Sn), zinc and / or cadmium (Zn and / or Cd), and lead and / or bismuth (Pb and / or Bi) in the core of a liquid gallium-based alloy meet the aforementioned specific atomic percentage requirements, the electron transport enhancement properties of the heavy metal elements Pb and Bi can be utilized, resulting in a significant improvement in the electrical conductivity of the liquid gallium-based alloy compared to traditional gallium-indium alloys or gallium-indium-tin alloys. Figure 1 As shown in the gallium-indium-tin-zinc-lead pentagonal phase diagram, it can be seen that as the mass fraction of Pb increases, the liquid phase range of the alloy is widened, and the temperature threshold of the multiphase coexistence region (such as the coexistence temperature of the liquid and solid phases) shows a gradual downward trend. This means that the introduction of an appropriate amount of Pb can not only effectively reduce the melting point of the liquid gallium-based alloy, but also enhance the liquid phase stability of the alloy in a low-temperature environment.

[0036] Moreover, the liquid gallium-based alloy is liquid at room temperature and consists of multiple droplets. Each droplet includes a liquid gallium-based alloy core and a modified coating layer on its surface. The modified coating layer can improve its dispersibility and suppress its agglomeration and sedimentation in subsequent applications. On the other hand, it can also play a passivation role, which can enhance the interfacial bonding force between the subsequently prepared liquid gallium-based alloy and matrix materials such as elastomers and polymers, and avoid interfacial separation during the composite process of liquid gallium-based alloy. This can improve the success rate of preparation of conductive stretching materials and the mechanical-electrical synergistic properties.

[0037] The droplets in the liquid gallium-based alloy provided in this application are micron-sized droplets with high size uniformity and good dispersion. They are not prone to agglomeration during the preparation of flexible conductive materials or flexible electronic devices, and can improve their comprehensive properties such as electrical performance.

[0038] In a preferred embodiment, the melting point of the liquid gallium-based alloy is ≤15°C. The melting point of the liquid gallium-based alloy includes, but is not limited to, the above range. Limiting it to the above range is beneficial to improving its fluidity, maintaining a stable liquid state at room temperature, avoiding droplet aggregation or dispersion failure due to solidification, and thus facilitating the uniform coating of subsequent modifying agents and the long-term storage and functional applications of the liquid gallium-based alloy (such as flexible electronics).

[0039] To further improve the fluidity of the liquid gallium-based alloy, preferably, the melting point of the liquid gallium-based alloy is -5 to 15°C.

[0040] In a preferred embodiment, the weight-average molecular weight of polyvinylpyrrolidone (PVP) is 10,000 to 58,000; the weight-average molecular weight of polyvinyl alcohol is 10,000 to 80,000; the weight-average molecular weight of polyethylene glycol is 2,000 to 20,000; and the weight-average molecular weight of chitosan is 50,000 to 300,000. Compared to other ranges, limiting the weight-average molecular weight of the modified coating material to the above range is beneficial to improving the dispersibility of the liquid gallium-based alloy and exerting the passivation effect of the modified coating.

[0041] To further improve the dispersibility of the liquid gallium-based alloy and further enhance the passivation effect of the modified coating, preferably, the weight percentage of the modified coating is 5 to 20 wt% based on the total weight of the liquid gallium-based alloy.

[0042] To further improve the electrical conductivity of the liquid gallium-based alloy, preferably, the liquid gallium-based alloy core comprises, by atomic percentage: 77–80 at% Ga, 14–16 at% In, 5–7 at% Sn, 2–3 at% Zn, and 0.5–1.5 at% Pb; or, the liquid gallium-based alloy core comprises: 77–80 at% Ga, 14–16 at% In, 5–7 at% Sn, 2–3 at% Cd, and 0.5–1.5 at% Bi; or, the liquid gallium-based alloy core comprises: 77–80 at% Ga, 14–16 at% In, 5–7 at% Sn, 1–2 at% Zn, 1–2 at% Cd, 0.5–1 at% Pb, and 0.5–1 at% Bi.

[0043] To further improve the conductivity of the liquid gallium-based alloy, more preferably, the core of the liquid gallium-based alloy includes Ga, In, Sn, Zn, Cd, Pb and Bi, and the atomic ratio of Zn to Cd is 1:(1 to 3); the atomic ratio of Pb to Bi is 1:(1 to 2).

[0044] In a preferred embodiment, the liquid gallium-based alloy core comprises, by atomic percentage: 75.24 at% Ga, 14.34 at% In, 6.46 at% Sn, 2.97 at% Zn, and 0.99 at% Pb. Compared to other types, the liquid gallium-based alloy core with the above-described specific composition and ratio is beneficial for improving the conductivity of the liquid gallium-based alloy.

[0045] The second aspect of this application also provides a method for preparing the above-mentioned liquid gallium-based alloy provided in this application. The method includes: step S1, mixing elemental gallium, elemental indium, elemental tin, elemental zinc and / or elemental cadmium, and elemental lead and / or elemental bismuth to obtain a mixed metal raw material; wherein the molar ratio of elemental gallium, elemental indium, elemental tin, elemental zinc and / or elemental cadmium, to elemental lead and / or elemental bismuth is (75-83):(13-17):(0.1-7):(0.1-3):(0.1-2); step... S2, in an inert atmosphere, the mixed metal raw materials are melted to obtain a molten material; S3, the molten material is cooled to obtain a liquid material; S4, the liquid material, solvent and modified coating agent are mixed and ultrasonically treated to obtain a suspension; the modified coating agent is selected from one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, chitosan and hexadecyltrimethylammonium bromide; S5, the suspension is subjected to static sedimentation and centrifugation treatment in sequence, and then dried to obtain a liquid gallium-based alloy.

[0046] Step S1 first involves mixing the five elemental raw materials in a specific molar ratio to obtain a mixed metal raw material, which provides gallium (Ga), indium (In), tin (Sn), zinc and / or cadmium (Zn and / or Cd), and lead and / or bismuth (Pb and / or Bi) elements for the core of the liquid gallium-based alloy. Then, the mixed metal raw material is melted in an inert atmosphere to transform the solid raw material into a molten state. After cooling, a liquid material is obtained. In step S4, the liquid material, solvent, and the aforementioned specific type of modifying coating agent are mixed, allowing the modifying coating agent to coat the surface of the liquid material and disperse in the solvent. A suspension is obtained through ultrasonic treatment. Finally, the suspension is subjected to static sedimentation and centrifugation, followed by drying to obtain the liquid gallium-based alloy.

[0047] Traditional methods for preparing liquid metal droplets involve directly mixing the cooled droplets with a solvent. However, in step S4 of this application, a specific type of modified coating agent is introduced. During the mixing process, this modified coating agent coats the surface of the liquid material and forms a protective film. This allows for precise control of the dispersion process, enabling on-demand control of droplet size and highly uniform size distribution, thus improving its dispersibility and inhibiting its aggregation and sedimentation in the suspension. Furthermore, the protective film provides passivation, enhancing the interfacial bonding between the subsequently prepared liquid gallium-based alloy and matrix materials such as elastomers and polymers. This prevents interfacial separation during the composite process of the liquid gallium-based alloy, thereby improving the success rate of conductive stretching material preparation and its mechanical-electrical synergistic properties.

[0048] Compared to other ranges, limiting the molar ratio of elemental gallium, indium, tin, zinc, and lead to the aforementioned specific range can leverage the enhanced electron transport properties of heavy metal elements Pb and Bi, resulting in a significant improvement in the conductivity of liquid gallium-based alloys compared to traditional gallium-indium alloys or gallium-indium-tin alloys. Furthermore, the liquid gallium-based alloy prepared using the method provided in this application is liquid at room temperature and consists of multiple micron-sized droplets with high size uniformity and good dispersibility. This makes it less prone to agglomeration during the fabrication of flexible conductive materials or flexible electronic devices, and also improves their overall electrical performance.

[0049] Furthermore, the above preparation method combines ultrasonic treatment, static sedimentation, and centrifugation to prepare droplet-shaped liquid gallium-based alloys. In actual operation, only general-purpose equipment such as ultrasonic breakers and centrifuges are needed. The operation is simple and controllable, easy to scale up production, and also reduces production costs, thus meeting the actual demand of "low cost and high output" for the large-scale production of conductive stretching materials.

[0050] It should be noted that in the preparation method provided in this application, step S1 includes five types of metal raw materials: the first type is "gallium element," the second type is "indium element," the third type is "tin element," the fourth type is "zinc element and / or cadmium element," and the fifth type is "lead element and / or bismuth element," totaling five types of raw materials. Specifically, "zinc element and / or cadmium element" in step S1 means that this type of raw material in the mixed metal raw material can be zinc element, cadmium element, or a mixture of zinc and cadmium element; similarly, "lead element and / or bismuth element" in step S1 means that this type of raw material in the mixed metal raw material can be lead element, bismuth element, or a mixture of lead and bismuth element. The molar ratio or atomic percentage content mentioned above in this application refers to the molar ratio or atomic percentage content of these five types of metal raw materials.

[0051] In a preferred embodiment, in step S2, the inert atmosphere includes, but is not limited to, argon and / or nitrogen. Using the aforementioned inert atmosphere for melting treatment helps to prevent the mixed metal raw materials from being oxidized and to avoid the introduction of other impurity elements.

[0052] In a preferred embodiment, in step S2, the melting temperature is 300–500°C. The melting temperature and time include, but are not limited to, the above range. Limiting them within this range helps to reach the melting point of the mixed metal raw materials, thereby achieving more efficient melting and increasing the yield of the molten material.

[0053] In a preferred embodiment, step S3 includes cooling the molten material to 20–30°C to obtain a liquid material. Compared to other temperatures, cooling the molten material to the above temperature range is beneficial for maintaining the product in a liquid state while facilitating subsequent dispersion in a solvent, thereby forming a suspension.

[0054] In order to improve the crystal structure of liquid materials and to control the grain size and reduce lattice defects and phase separation caused by rapid cooling, the cooling rate is preferably 1 to 3 °C / min.

[0055] In a preferred embodiment, in step S4, the modified coating agent accounts for 0.1 to 1 wt% of the weight of the suspension. The weight percentage of the modified coating agent in the suspension includes, but is not limited to, the above range. Limiting it to the above range is beneficial to improving the dispersibility of the liquid material in the suspension and inhibiting its aggregation and sedimentation. At the same time, it is also beneficial to exert a passivation effect, so that the subsequently prepared liquid gallium-based alloy includes a modified coating layer, thereby enhancing the interfacial bonding force between the subsequently prepared liquid gallium-based alloy and matrix materials such as elastomers and polymers.

[0056] In a preferred embodiment, in step S4, the weight ratio of the liquid material to the solvent is 1:(20-40). The weight ratio of the liquid material to the solvent includes, but is not limited to, the above range. Limiting it to the above range is beneficial to improving the dispersibility of the liquid material and inhibiting its agglomeration and sedimentation; it is also beneficial to control its size.

[0057] In order to improve the dispersibility of liquid materials and suppress their aggregation and sedimentation, in a preferred embodiment, in step S4, the solvent includes, but is not limited to, one or more of water, ethanol, propylene glycol, glycerol, formic acid and acetic acid.

[0058] In a preferred embodiment, in step S4, the ultrasonic treatment power is 400–1000 W, and the time is 5–30 min. The ultrasonic treatment power and time include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial for allowing the liquid material in the suspension to come into more sufficient contact with the modified coating agent, thereby improving the coating rate of the modified coating agent.

[0059] To further improve the coating rate of the modified coating agent, preferably, the ultrasonic treatment is ultrasonic pulse treatment, and the ultrasonic pulse is turned on for 8s and turned off for 2s in each cycle; or, the turn-on time is 10s and the turn-off time is 5s; or, the turn-on time is 20s and the turn-off time is 10s.

[0060] In a preferred embodiment, in step S5, the settling time is 1 to 4 hours. The settling time includes, but is not limited to, the above range. Limiting it to the above range is beneficial to improving the solid-liquid separation efficiency, facilitating the separation of precipitate from supernatant, and facilitating the collection of the target product.

[0061] In a preferred embodiment, in step S5, the centrifugation speed is 100–1000 rpm, and the time is 5–60 min. The centrifugation speed and time include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the separation efficiency of precipitate and residual solvent.

[0062] In a preferred embodiment, in step S5, the drying temperature is 50–80°C and the time is 2–6 hours. Compared to other ranges, limiting the drying temperature and time to the above range is beneficial to improving the removal rate of residual solvent and obtaining a liquid gallium-based alloy with higher purity.

[0063] A third aspect of this application also provides an application of the liquid gallium-based alloy provided herein in the fabrication of flexible conductive materials or flexible electronic devices. The electrical conductivity of the liquid gallium-based alloy provided herein is significantly improved compared to traditional gallium-indium alloys or gallium-indium-tin alloys. Furthermore, the liquid gallium-based alloy provided herein is liquid at room temperature and is in droplet form with an average particle size on the micrometer scale. It exhibits high size uniformity and good dispersibility, making it less prone to agglomeration during the fabrication of flexible conductive materials or flexible electronic devices, and thus improving their overall electrical performance and other properties.

[0064] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0065] (I) Preparation Examples

[0066] Preparation Example 1

[0067] A method for preparing a liquid gallium-based alloy includes the following steps:

[0068] (1) Preheat the glove box after argon purging to room temperature. The oxygen content in the glove box is ≤10ppm and the water content is ≤10ppm. Weigh 195.29g (2.801mol) gallium, 61.29g (0.534mol) indium, 28.55g (0.240mol) tin, 7.23g (0.111mol) zinc and 7.62g (0.037mol) lead into the glove box. Add the weighed gallium, indium, tin, zinc and lead into a high-temperature alloy crucible and stir with a clean stirring rod to obtain mixed metal raw materials.

[0069] (2) Transfer the crucible containing the mixed metal raw material obtained in step (1) to a tube furnace that has been pre-protected by nitrogen gas, and continuously purge nitrogen gas for 30 minutes at a flow rate of 75 mL / min to completely remove the air from the furnace; start the tube furnace and raise the temperature inside the furnace to 400°C for melting treatment to obtain molten material.

[0070] (3) Allow the molten material obtained in step (2) to cool naturally to room temperature in a tube furnace (cooling rate is 1℃ / min) to obtain liquid material, and seal it in a sealed container to prevent oxidation when exposed to air;

[0071] (4) Mix 20 mL of anhydrous ethanol with 0.1 g of modified coating agent PVP (weight average molecular weight of 32000) to obtain a mixture. Then add 0.5 g of the liquid material obtained in step (3) to the mixture and sonicate it at an ultrasonic power of 400 W for 15 min. The ultrasonic treatment is ultrasonic pulse treatment, with an on time of 8 s and an off time of 2 s in each cycle, to obtain a suspension. The PVP accounts for 0.6 wt% of the weight of the suspension.

[0072] (5) Let the suspension obtained in step (4) stand for 2 hours, remove the upper impurities and agglomerates with a dropper; centrifuge the remaining suspension at 500 rpm for 30 minutes; discard the supernatant and collect the precipitate; vacuum dry the precipitate at 70°C for 4 hours to obtain liquid gallium-based alloy.

[0073] Depend on Figure 2 As can be seen, the liquid gallium-based alloy consists of multiple droplets with an average droplet size of 5 μm. Each droplet includes a liquid gallium-based alloy core and a modified coating layer disposed on its surface. ICP-MS analysis shows that, by atomic percentage, the liquid gallium-based alloy core comprises: 75.24 at% Ga, 14.34 at% In, 6.46 at% Sn, 2.97 at% Zn, and 0.99 at% Pb.

[0074] Preparation Example 2

[0075] The difference from Preparation Example 1 is that the molar ratio of gallium, indium, tin, zinc and lead in step (1) is 75:17:7:0.5:0.5. The remaining steps are the same as in Preparation Example 1.

[0076] Preparation Example 3

[0077] The difference from Preparation Example 1 is that the molar ratio of gallium, indium, tin, zinc and lead in step (1) is 83:13:0.1:3:0.9. The remaining steps are the same as in Preparation Example 1.

[0078] Preparation Example 4

[0079] The difference from Preparation Example 1 is that the molar ratio of gallium, indium, tin, zinc and lead in step (1) is 75.9:15:7:0.1:2. The remaining steps are the same as in Preparation Example 1.

[0080] Preparation Example 5

[0081] The difference from Preparation Example 1 is that in step (4), an equal amount of PVP with a weight-average molecular weight of 10,000 is used as the modifying coating agent. The remaining steps are the same as in Preparation Example 1.

[0082] Preparation Example 6

[0083] The difference from Preparation Example 1 is that in step (4), an equal amount of PVP with a weight-average molecular weight of 58,000 is used as the modifying coating agent. The remaining steps are the same as in Preparation Example 1.

[0084] Preparation Example 7

[0085] The difference from Preparation Example 1 is that in step (4), an equal amount of polyvinyl alcohol with a weight average molecular weight of 10,000 is used as the modifying coating agent. The remaining steps are the same as in Preparation Example 1.

[0086] Preparation Example 8

[0087] The difference from Preparation Example 1 is that in step (4), an equal amount of polyvinyl alcohol with a weight average molecular weight of 80,000 is used as the modifying coating agent. The remaining steps are the same as in Preparation Example 1.

[0088] Preparation Example 9

[0089] The difference from Preparation Example 1 is that in step (4), an equal amount of polyethylene glycol with a weight-average molecular weight of 2000 is used as the modifying coating agent. The remaining steps are the same as in Preparation Example 1.

[0090] Preparation Example 10

[0091] The difference from Preparation Example 1 is that in step (4), an equal amount of polyethylene glycol with a weight-average molecular weight of 20,000 is used as the modifying coating agent. The remaining steps are the same as in Preparation Example 1.

[0092] Preparation Example 11

[0093] The difference from Preparation Example 1 is that the amount of modified coating agent PVP used in step (4) is 0.0163g, and the weight percentage of PVP in the suspension is 0.1wt%. The remaining steps are the same as in Preparation Example 1.

[0094] Preparation Example 12

[0095] The difference from Preparation Example 1 is that the amount of modified coating agent PVP used in step (4) is 0.164g, and the weight percentage of PVP in the suspension is 1wt%. The remaining steps are the same as in Preparation Example 1.

[0096] Preparation Example 13

[0097] The difference from Preparation Example 1 is that the amount of modified coating agent PVP used in step (4) is 0.198g, and the weight percentage of PVP in the suspension is 1.2wt%. The remaining steps are the same as in Preparation Example 1.

[0098] Preparation Example 14

[0099] The difference from Preparation Example 1 is that in step (4), the ultrasonic treatment is performed at an ultrasonic power of 1000W for 5 minutes, and the ultrasonic treatment is ultrasonic pulse treatment. The ultrasonic pulse is turned on for 20 seconds and turned off for 10 seconds in each cycle to obtain a suspension. The remaining steps are the same as those in Preparation Example 1.

[0100] Preparation Example 15

[0101] The difference from Preparation Example 1 is that in step (4), the ultrasonic treatment is performed at an ultrasonic power of 400W for 30 minutes, and the ultrasonic treatment is ultrasonic pulse treatment. The ultrasonic pulse is turned on for 10 seconds and turned off for 5 seconds in each cycle to obtain a suspension. The remaining steps are the same as those in Preparation Example 1.

[0102] Preparation Example 16

[0103] The difference from Preparation Example 1 is that step (5) includes: letting the suspension obtained in step (4) stand for 1 hour, removing the upper impurities and agglomerates with a dropper; centrifuging the remaining suspension at 1000 rpm for 5 minutes; discarding the supernatant and collecting the precipitate; and vacuum drying the precipitate at 50°C for 6 hours to obtain a liquid gallium-based alloy. The remaining steps are the same as in Preparation Example 1.

[0104] Preparation Example 17

[0105] The difference from Preparation Example 1 is that step (5) includes: letting the suspension obtained in step (4) stand for 4 hours, removing the upper impurities and agglomerates with a dropper; centrifuging the remaining suspension at 100 rpm for 60 minutes; discarding the supernatant and collecting the precipitate; and vacuum drying the precipitate at 80°C for 2 hours to obtain the liquid gallium-based alloy. The remaining steps are the same as in Preparation Example 1.

[0106] Preparation Example 18

[0107] The difference from Preparation Example 1 is that step (5) includes: letting the suspension obtained in step (4) stand for 5 hours, removing the upper impurities and agglomerates with a dropper; centrifuging the remaining suspension at 1200 rpm for 70 minutes; discarding the supernatant and collecting the precipitate; and vacuum drying the precipitate at 90°C for 2 hours to obtain the liquid gallium-based alloy. The remaining steps are the same as in Preparation Example 1.

[0108] Preparation Example 19

[0109] The difference from the preparation example 1 is that in step (1), the same amount of Cd elemental is used to replace Zn, and the same amount of Bi elemental is used to replace Pb.

[0110] Preparation of Comparative Example 1

[0111] The difference from Preparation Example 1 is that in step (1), tin, zinc and lead were not weighed, only gallium and indium were weighed, and the weights of gallium and indium were the same as in Preparation Example 1.

[0112] Preparation of Comparative Example 2

[0113] The difference from Preparation Example 1 is that zinc and lead were not weighed in step (1), only gallium, indium and tin were weighed, and the weights of gallium, indium and tin were the same as in Preparation Example 1.

[0114] Preparation of Comparative Example 3

[0115] The difference from preparation example 1 is that the molar ratio of gallium, indium, tin, zinc and lead in step (1) is 73:18:4:4:1.

[0116] Preparation of Comparative Example 4

[0117] The difference from Preparation Example 1 is that the molar ratio of gallium, indium, tin, zinc and lead in step (1) is 75:24.7:0.1:0.1:0.1. The remaining steps are the same as in Preparation Example 1.

[0118] Preparation of Comparative Example 5

[0119] The difference from Preparation Example 1 is that the modified coating agent PVP was not added in step (4). The remaining steps are the same as those in Preparation Example 1.

[0120] Table 1

[0121]

[0122] (II) Application Examples

[0123] Application Example 1

[0124] A method for preparing a liquid gallium-based alloy / polyurethane flexible composite conductive material includes:

[0125] (1) Preheat the glove box after argon replacement to room temperature. The oxygen content in the glove box is ≤10ppm and the water content is ≤10ppm. Take 4.0g of the liquid gallium-based alloy prepared in Example 1 in the glove box, add 0.04g of titanate coupling agent NDZ-101, and then add 4mL of anhydrous ethanol. Stir and mix for 10min at a rate of 150r / min with a clean stirring rod to ensure that the coupling agent is uniformly adsorbed on the surface of the droplets to obtain a modified liquid gallium-based alloy droplet mixture.

[0126] (2) Transfer the beaker containing the modified liquid gallium-based alloy droplet mixture obtained in step (1) to a fume hood, add 15g of water-based polyurethane emulsion (solid content of 30wt%), and stir in a magnetic stirrer at a speed of 250r / min for 15min. During the stirring process, add 0.5g of crosslinking agent ethylenediamine droplets to make the liquid gallium-based alloy droplets uniformly dispersed in the polyurethane matrix to obtain a composite slurry.

[0127] (3) Add 0.2g of triethylenediamine catalyst to the composite slurry obtained in step (2), continue stirring for 6 minutes, then pour the composite slurry into a polytetrafluoroethylene mold of a preset size, scrape it smooth with a scraper, control the thickness of the film to be 400μm, place it in a ventilated place and let it stand for 30 minutes to allow the solvent to evaporate initially.

[0128] (4) Place the pre-dried composite slurry and mold into a constant temperature oven, pre-cur at 50°C for 1.5 hours, then raise the temperature to 90°C and cure at a constant temperature for 4 hours to complete the cross-linking curing and molding, ensuring the material structure is dense.

[0129] (5) After curing, the composite film is removed from the mold, and the surface is wiped with anhydrous ethanol to remove the unreacted reagents and impurities. Then it is placed in a vacuum drying oven and dried for 3 hours at 75°C and -0.1MPa vacuum to remove residual solvents and moisture, thus obtaining liquid gallium-based alloy / polyurethane flexible composite conductive material.

[0130] Application Examples 2 to 19

[0131] The difference from Application Example 1 is that an equal amount of the liquid gallium-based alloy prepared in Preparation Examples 2 to 19 is used to replace the liquid gallium-based alloy in step (1).

[0132] Application Comparative Examples 1 to 5

[0133] The difference from Application Example 1 is that an equal amount of the liquid gallium-based alloy prepared in Comparative Examples 1 to 5 is used to replace the liquid gallium-based alloy in step (1).

[0134] The mechanical-electrical synergistic properties of the liquid gallium-based alloy / polyurethane flexible composite conductive materials prepared in all the above-described application embodiments and comparative examples of this application were tested. The test method is as follows: The two ends of the tensile specimen were fixed with copper tape and connected to the test electrodes of the digital source meter (Keithley 2450), ensuring good contact between the electrodes and the specimen and negligible contact resistance; then the specimen was clamped on the tensile fixture of the electronic universal testing machine, and the fixture position was adjusted so that the gauge length of the specimen was in a naturally straight state and coaxial with the tensile direction; the digital source meter was connected to the computer, the data acquisition frequency was set to 1Hz, and the resistance value of the specimen was recorded in real time. Then, the tensile rate of the electronic universal testing machine was set to 20 mm / min, and the machine was started to perform a uniaxial tensile test until the specimen broke. During the test, the electronic universal testing machine collected the tensile displacement (tensile rate) of the specimen in real time. At the same time, the digital source meter collected the resistance value of the specimen. The conductivity of the material can be calculated according to the formula σ=ρL / S (where σ is conductivity, ρ is resistivity, L is specimen length, and S is specimen cross-sectional area). The test results are shown in Table 2.

[0135] Table 2

[0136]

[0137] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0138] When the five metal elements gallium (Ga), indium (In), tin (Sn), zinc and / or cadmium (Zn and / or Cd), and lead and / or bismuth (Pb and / or Bi) in the core of a liquid gallium-based alloy meet the above-mentioned specific atomic percentages, the electron transport enhancement properties of heavy metal elements Pb and Bi can be utilized, resulting in a significant improvement in the electrical conductivity of the liquid gallium-based alloy compared to traditional gallium-indium alloys or gallium-indium-tin alloys.

[0139] Moreover, the liquid gallium-based alloy is liquid at room temperature and consists of multiple droplets. Each droplet includes a liquid gallium-based alloy core and a modified coating layer on its surface. The modified coating layer can improve its dispersibility and suppress its agglomeration and sedimentation in subsequent applications. On the other hand, it can also play a passivation role, which can enhance the interfacial bonding force between the subsequently prepared liquid gallium-based alloy and matrix materials such as elastomers and polymers, and avoid interfacial separation during the composite process of liquid gallium-based alloy. This can improve the success rate of preparation of conductive stretching materials and the mechanical-electrical synergistic properties.

[0140] The droplets in the liquid gallium-based alloy provided in this application are micron-sized droplets with high size uniformity and good dispersion. They are not prone to agglomeration during the preparation of flexible conductive materials or flexible electronic devices, and can improve their comprehensive properties such as electrical performance.

[0141] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0142] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A liquid gallium-based alloy, characterized in that, The liquid gallium-based alloy is composed of multiple droplets, each droplet comprising a liquid gallium-based alloy core and a modified coating layer disposed on its surface; The liquid gallium-based alloy core, based on atomic percentage, comprises: 75–83 at% Ga, 13–17 at% In, 0.1–7 at% Sn, 0.1–3 at% Zn and / or Cd, and 0.1–2 at% Pb and / or Bi; the modified coating layer is selected from one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, chitosan, and hexadecyltrimethylammonium bromide; the droplets have an average particle size of 1–5 μm and an electrical conductivity ≥3.6 × 10⁻⁶. 6 S / m.

2. The liquid gallium-based alloy according to claim 1, characterized in that, The melting point of the liquid gallium-based alloy is ≤15℃; preferably -5~15℃. Preferably, the weight-average molecular weight of the polyvinylpyrrolidone is 10,000 to 58,000; the weight-average molecular weight of the polyvinyl alcohol is 10,000 to 80,000; the weight-average molecular weight of the polyethylene glycol is 2,000 to 20,000; and the weight-average molecular weight of the chitosan is 50,000 to 300,000. Preferably, the modified coating layer comprises 5-20 wt% of the total weight of the liquid gallium-based alloy. Preferably, based on atomic percentage, the liquid gallium-based alloy core comprises: 77-80 at% Ga, 14-16 at% In, 5-7 at% Sn, 2-3 at% Zn, and 0.5-1.5 at% Pb; or, the liquid gallium-based alloy core comprises: 77-80 at% Ga, 14-16 at% In, 5-7 at% Sn, 2-3 at% Cd, and 0.5-1.5 at% Bi; or, the liquid gallium-based alloy core comprises: 77-80 at% Ga, 14-16 at% In, 5-7 at% Sn, 1-2 at% Zn, 1-2 at% Cd, 0.5-1 at% Pb, and 0.5-1 at% Bi. More preferably, the liquid gallium-based alloy core comprises Ga, In, Sn, Zn, Cd, Pb, and Bi, wherein the atomic ratio of Zn to Cd is 1:(1-3); and the atomic ratio of Pb to Bi is 1:(1-2).

3. A method for preparing the liquid gallium-based alloy according to claim 1 or 2, characterized in that, The preparation method includes: Step S1: Mix elemental gallium, elemental indium, elemental tin, elemental zinc and / or elemental cadmium, and elemental lead and / or elemental bismuth to obtain a mixed metal raw material; wherein the molar ratio of elemental gallium, elemental indium, elemental tin, elemental zinc and / or elemental cadmium to elemental lead and / or elemental bismuth is (75-83):(13-17):(0.1-7):(0.1-3):(0.1-2); Step S2: The mixed metal raw material is melted in an inert atmosphere to obtain a molten material; Step S3: Cool the molten material to obtain a liquid material; Step S4: The liquid material, solvent and modified coating agent are mixed and ultrasonically treated to obtain a suspension; the modified coating agent is selected from one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, chitosan and hexadecyltrimethylammonium bromide; Step S5: The suspension is subjected to static sedimentation and centrifugation in sequence, and then dried to obtain liquid gallium-based alloy.

4. The method for preparing liquid gallium-based alloy according to claim 3, characterized in that, In step S2, the inert atmosphere is selected from argon and / or nitrogen.

5. The method for preparing liquid gallium-based alloy according to claim 3, characterized in that, In step S2, the temperature of the melting treatment is 300–500°C.

6. The method for preparing liquid gallium-based alloy according to claim 3, characterized in that, Step S3 includes: cooling the molten material to 20-30°C to obtain the liquid material; Preferably, the cooling rate is 1 to 3 °C / min.

7. The method for preparing liquid gallium-based alloys according to any one of claims 3 to 6, characterized in that, In step S4, the modified coating agent accounts for 0.1–1 wt% of the weight of the suspension; and / or, The weight ratio of the liquid material to the solvent is 1:(20-40); and / or, The solvent is selected from one or more of water, ethanol, propylene glycol, glycerol, formic acid, and acetic acid.

8. The method for preparing liquid gallium-based alloy according to claim 3, characterized in that, In step S4, the power of the ultrasonic treatment is 400–1000 W, and the time is 5–30 min; and / or, The ultrasonic processing is ultrasonic pulse processing, and the ultrasonic pulse has an on time of 8s and an off time of 2s in each cycle; or, an on time of 10s and an off time of 5s; or, an on time of 20s and an off time of 10s.

9. The method for preparing liquid gallium-based alloy according to claim 3, characterized in that, In step S5, the settling time is 1–4 hours; and / or, The centrifugation process is carried out at a speed of 100–1000 rpm for a time of 5–60 min; and / or, The drying process is carried out at a temperature of 50–80°C for 2–6 hours.

10. The application of the liquid gallium-based alloy according to claim 1 or 2 in the preparation of flexible conductive materials or flexible electronic devices.

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