Method for constructing functional interface on metal surface at low temperature through ultrasonic-assisted liquid gallium

Abstract

The invention discloses a method for constructing a functional interface on a metal surface at a low temperature through ultrasonic-assisted liquid gallium, and belongs to the field of material surface modification. The method comprises the following steps: pretreating metal substrates such as copper, silver, nickel and the like, immersing the metal substrates in liquid gallium, applying low-power-density ultrasonic waves at a low temperature of less than or equal to 50 DEG C, treating for several minutes, overcoming a solid atomic diffusion barrier by utilizing an ultrasonic cavitation effect, and rapidly driving an interface alloying reaction to form an intermetallic compound functional layer; and then residual gallium is removed through centrifugation and acid pickling. According to the invention, low-temperature, rapid and controllable construction of metal surface functions is realized.

Description

Technical Field

[0001] This invention belongs to the field of surface modification of metal materials and preparation of functional materials. Specifically, it relates to a method for rapidly and controllably constructing functional intermetallic compound interfaces on the surfaces of metals such as copper (Cu), silver (Ag), and nickel (Ni) at low temperature (≤50℃) using low-power ultrasound-assisted liquid gallium (Ga) as an active solvent. Background Technology

[0002] Liquid metals, especially gallium (Ga) and its alloys, are highly liquid due to their excellent fluidity and high thermal conductivity (20-30 W / m²) at room temperature. -1 K -1 Ga's ability to form intermetallic compounds with various metals has made it an emerging platform for materials synthesis and surface modification. Utilizing the interfacial reaction between liquid Ga and solid metals, functional alloy layers or intermetallic compound layers can be directly generated on metal substrates at relatively low temperatures. This is of great significance for the development of high-performance thermal interface materials and functional coatings.

[0003] However, traditional reactions between solid metals and liquid Ga primarily rely on static thermal diffusion, a process hampered by the oxide layer on the solid metal surface and the extremely high energy barrier for solid-state atomic diffusion. To achieve significant reactions and alloy layer growth, existing techniques typically require high temperatures (>100°C) or extremely long processing times (hours to days). This is not only energy-intensive and inefficient but can also cause thermal damage to heat-sensitive substrates or precision electronic components, limiting the widespread application of this technology. For example, although nickel (Ni) can thermodynamically form stable compounds with Ga (such as NiGa4), its extremely high melting point (1455°C) and extremely low solid-state diffusion coefficient make static reactions with liquid Ga at room temperature or near room temperature virtually impossible. Furthermore, the reaction products are often difficult to control, making it impossible to achieve controllable preparation of specific morphologies and structures to meet the specific requirements of different applications (such as high thermal conductivity, high specific surface area catalysis, SERS enhancement, etc.).

[0004] To overcome these kinetic limitations, researchers have attempted to introduce external fields such as mechanical stirring, electric fields, or magnetic fields. However, mechanical stirring is difficult to effectively activate the solid-liquid interface at the microscale, while electric or magnetic fields have specific requirements for equipment and material systems, limiting their versatility. Ultrasound, as a highly efficient means of energy transfer and mass transport, has been widely applied in welding, cleaning, and nanomaterial synthesis. The cavitation effect it generates (microjets, shock waves) can effectively strip the passivation layer from solid surfaces and produce intense micro-stirring and localized high temperature and pressure near the solid-liquid interface, potentially greatly promoting interfacial atomic exchange and overcoming thermal diffusion limitations.

[0005] However, how to apply low-power ultrasound precisely and efficiently to liquid metal / solid metal interface reaction systems to achieve rapid and controllable surface functionalization of various metals at low temperatures, and to elucidate the synergistic regulation of the ultrasonic external field and the intrinsic physical properties of metals (melting point, enthalpy of formation, solubility) on the final interface structure morphology, remains one of the technical problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, to address the technical bottlenecks of high temperature, slow reaction rate, and poor controllability in the interfacial reaction between liquid Ga and solid metals in existing technologies, this invention provides a method for constructing functional interfaces on metal surfaces at low temperatures using liquid gallium with low-power ultrasound assistance. This method utilizes the instantaneous high energy provided by the ultrasonic cavitation effect to overcome the kinetic barrier of solid-state atomic diffusion, rapidly activating and driving various metals (such as Cu, Ag, Ni) to undergo interfacial reactions with liquid Ga within minutes at low temperatures (e.g., 40°C), forming functional intermetallic compound layers with specific microstructures (e.g., irregular hexahedral-lamellar composite structures, needle-like crystals, porous sponge structures). This invention offers advantages such as universality, high efficiency, mild low-temperature operation, and controllable morphology.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention relates to a method for constructing functional interfaces on metal surfaces at low temperatures using ultrasound-assisted liquid gallium, comprising the following steps: (1) Metal substrate pretreatment: The metal substrate is subjected to surface pretreatment to remove the oxide layer and clean the surface. The metal substrate is selected from one or more of Cu, Ag and Ni. (2) Ultrasonic-assisted interface reaction: The pretreated metal substrate is immersed in liquid gallium and placed in an ultrasonic treatment device; under the condition of controlling the reaction temperature ≤50℃, ultrasonic treatment of 50-150 W / L is applied for 5-30 min to make the interface between liquid gallium and metal substrate undergo rapid alloying reaction. (3) Post-processing: After the reaction is complete, the sample is removed, and the unreacted liquid gallium remaining on the surface is removed by centrifugation and / or selective acid washing. Then, it is rinsed with deionized water to obtain a modified metal substrate with an intermetallic compound functional layer on the surface. In the method, the role of ultrasound is to destroy the passivation layer on the surface of the metal substrate through the microjets and shock waves generated by the cavitation effect, and to provide extremely high instantaneous energy and mass transfer rate at the solid-liquid interface, thereby overcoming the kinetic limitations of solid-state diffusion and realizing rapid interfacial reaction at low temperature.

[0008] In a preferred embodiment of the present invention, step (1) includes the following steps: surface polishing of the target metal substrate, followed by immersion in acid to remove the surface oxide layer, ultrasonic cleaning with deionized water and anhydrous ethanol, and drying.

[0009] In a preferred embodiment of the present invention, the reaction temperature in step (2) is 40±2℃.

[0010] In a preferred embodiment of the present invention, the ultrasonic treatment time in step (2) is 5-12 min.

[0011] In a preferred embodiment of the present invention, the liquid gallium in step (2) also contains 5-15 v / v% acetone, and the ultrasonic treatment time is 5-7 min.

[0012] Another aspect of the present invention relates to surface-functionalized metallic materials prepared by the above method: When the metal substrate is Cu, a composite morphology consisting of irregular hexahedral particles and plate-like structures is formed on the surface, and the main phase is CuGa2. When the metal substrate is Ag, a regularly growing needle-like crystal morphology is formed on the surface, and the main phase is Ag2Ga; When the metal substrate is Ni, a unique micro-nano porous sponge-like morphology is formed on the surface, with NiGa4 as the main phase.

[0013] This functional layer significantly alters the physicochemical properties of the substrate surface, such as light absorption / reflection characteristics, surface roughness, specific surface area, and thermal and electrical conductivity interface properties.

[0014] An application of a surface-functionalized metallic material prepared by the method described above, the material can be used in at least one of the following fields: as a component of a high-performance thermal interface material, utilizing its good interfacial bonding with liquid Ga and the high thermal conductivity of the intermetallic compound layer; as a surface-enhanced Raman scattering (SERS) substrate, particularly Ag-Ga systems with needle-like structures, exhibiting a significant Raman signal enhancement effect; and as a special wettable surface, catalyst support, or corrosion-resistant coating.

[0015] The present invention has achieved the following beneficial technical effects: (1) Low temperature and high efficiency: For the first time, under mild conditions of ≤50℃ (as low as 40℃), the rapid activation of the interface reaction between Cu, Ag, Ni and liquid Ga was achieved, and the reaction time was shortened to the minute level, overcoming the high temperature and long time requirements of traditional thermal diffusion methods; especially with the participation of acetone, the reaction time was further shortened.

[0016] (2) Strong universality: The method of the present invention is effective for a variety of metals, including Ni with high melting point and high inertness, demonstrating good universality.

[0017] (3) Controllable morphology: By selecting different metal substrates, functional layers with different micromorphologies such as irregular composite structure, regular needle-like crystal, and porous sponge structure can be prepared in a directional manner to meet diverse application needs.

[0018] (4) Clear mechanism: It reveals the phased synergistic effect of ultrasonic external field (overcoming diffusion barrier) and intrinsic thermodynamic properties of metal (enthalpy of formation, solubility) in determining reaction path and final morphology, providing guidance for rational design.

[0019] (5) Broad application prospects: The prepared functionalized surfaces show direct application potential in fields such as thermal management, photoelectric sensing, and catalysis. For example, the Ag-Ga needle structure system shows excellent SERS performance.

[0020] This method is particularly suitable for surface functionalization of metal substrates in fields such as thermal interface materials, surface-enhanced Raman scattering (SERS) substrates, corrosion-resistant coatings, and catalyst supports. Attached Figure Description

[0021] Figure 1 : Schematic diagram of the ultrasonic-assisted reaction process between liquid Ga and metal interface in Example 1 of this invention, and comparison of macroscopic photos and microscopic morphology before and after different metal treatments; Figure 2 Multi-scale SEM images of the Cu, Ag, and Ni metal substrate surfaces after ultrasonic treatment in Example 1 of this invention; Figure 3 The XRD patterns and DSC curves of the reaction products in Example 1 of this invention confirmed the formation of intermetallic compounds (CuGa2, Ag2Ga, NiGa4). Figure 4 EDS surface scan analysis of residual metal elements in liquid Ga after reaction in Example 1 of this invention; Figure 5 Based on the normalized ternary phase diagram of metal melting point, enthalpy of formation, and solubility, the formation mechanism of the final morphology of different metals is elucidated. Figure 6 The surface-enhanced Raman scattering (SERS) performance test results based on the Ag-Ga needle-like structure substrate in Embodiment 2 of this invention. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0023] Example 1: Ultrasonic-assisted interface construction of liquid Ga on Cu, Ag, and Ni surfaces (1) Material pretreatment: High-purity Cu plates, Ag plates, and Ni plates (purity > 99.9%) were taken and mechanically polished until the surface was smooth. Then they were immersed in 1 M HCl solution for 30 seconds to completely remove the surface oxide layer. They were then ultrasonically cleaned with deionized water and anhydrous ethanol in sequence, and dried with nitrogen gas for later use.

[0024] (2) Ultrasonic-assisted reaction: Take about 10 mL of liquid Ga (purity >99.99%) and place it in a 50 mL beaker. Vertically fix the pretreated metal substrate and immerse it completely in the liquid Ga. Place the beaker in a commercial ultrasonic cleaner (with temperature control, model YM-040PLUS) with a frequency of 40 kHz and a maximum power of 100 W. Set the ultrasonic power density to 100 W / L, the reaction temperature to (40±2)℃, and the treatment time to 10 minutes. During the process, maintain a constant temperature by circulating cooling water.

[0025] (3) Post-treatment: After the reaction was completed, the sample was taken out and immediately centrifuged at 6000 rpm for 5 minutes to remove most of the liquid Ga remaining on the surface. Then the sample was immersed in 1 M HCl solution for 10 minutes to dissolve and remove the residual Ga. Finally, it was washed with ethanol and vacuum dried to obtain surface-functionalized Cu, Ag and Ni materials.

[0026] Characterization results: Morphological observation (corresponding) Figure 1 (f)-(h), Figure 2 Multi-scale SEM characterization of (a)-(c) copper, (d)-(f) silver, and (g)-(i) nickel substrates after ultrasonic-assisted liquid gallium activation: SEM images show that the Cu surface forms a composite structure of irregular hexahedrons and lamellae; the Ag surface grows regular, sharp needle-like crystals; and the Ni surface exhibits a unique micro-nano porous sponge-like structure. Macroscopically, the light reflectivity of all metal surfaces decreases significantly, becoming dull and rough.

[0027] Phase analysis (corresponding) Figure 3 XRD analysis confirmed the formation of CuGa2 phase on the Cu surface, Ag2Ga phase on the Ag surface, and NiGa4 phase on the Ni surface. DSC curves showed significant endothermic peaks near the melting points of the corresponding alloys (CuGa2: ~253.3℃, ​​NiGa4: ~358.8℃, Ag2Ga: ~438.3℃), further confirming the formation of intermetallic compounds.

[0028] Interface process analysis (corresponding) Figure 4The morphology of residual metal elements in liquid Ga after ultrasonic fragmentation and EDS surface scan analysis are shown in (a)-(c) for copper, (d)-(f) for silver and (g)-(i) for nickel substrates. Multi-scale SEM characterization of the substrate surfaces is magnified step by step: EDS analysis of the residues in liquid Ga after reaction revealed that Ag and Ni signals were enriched in a point-like or layered manner on the Ga droplet surface, confirming that solid metal atoms can undergo a non-equilibrium process of "reverse" dissolution and migration to the liquid phase under ultrasonic action.

[0029] Example 2: SERS application performance test of Ag-Ga needle-like functional layer (1) Material pretreatment: High-purity Cu plates, Ag plates, and Ni plates (purity > 99.9%) were taken and mechanically polished until the surface was smooth. Then they were immersed in 1 M HCl solution for 30 seconds to completely remove the surface oxide layer. They were then ultrasonically cleaned with deionized water and anhydrous ethanol in sequence, and dried with nitrogen gas for later use.

[0030] (2) Ultrasonic-assisted reaction: Take about 10 mL of liquid Ga (purity >99.99%) and place it in a 50 mL beaker. Add 1 mL of acetone. Vertically fix the pretreated metal substrate and immerse it completely in the liquid Ga. Place the beaker in a commercial ultrasonic cleaner (with temperature control, model YM-040PLUS) with a frequency of 40 kHz and a maximum power of 100 W. Set the ultrasonic power density to 100 W / L, the reaction temperature to (40±2)℃, and the treatment time to 6 minutes. During this period, the temperature is kept constant by circulating cooling water.

[0031] (3) Post-treatment: After the reaction was completed, the sample was removed and immediately centrifuged at 6000 rpm for 5 minutes to remove most of the liquid Ga and acetone remaining on the surface. Then the sample was immersed in 1 M HCl solution for 10 minutes to dissolve and remove the residual Ga. Finally, it was washed with ethanol and vacuum dried to obtain the surface-functionalized Ag material.

[0032] (4) SERS test: Using crystal violet (CV) as the probe molecule, prepare different concentrations (e.g., 10) -6 A CV aqueous solution of M) was added dropwise to the surface of an Ag-Ga substrate. After drying at room temperature, the signal was acquired using a Raman spectrometer equipped with a microscopic system.

[0033] (5) Results Analysis (corresponding) Figure 6 The test results show that, compared to a smooth Ag surface, the Ag-Ga substrate with a needle-like structure exhibits better adhesion to low concentrations of CV molecules (such as 10⁻⁶). -6The M) exhibits clear and significantly enhanced Raman characteristic peaks (approximately 3-fold increase), demonstrating its excellent SERS performance, which is attributed to the localized field enhancement effect generated by the needle-like crystal clusters. In particular, the processing time can be significantly shortened by adding a small amount of acetone to the liquid Ga. It is speculated that this is because the addition of acetone further reduces the interfacial tension between the metal substrate and the liquid Ga, thereby accelerating alloy formation. It should be noted that this phenomenon is not pronounced when using other organic solvents (e.g., ethanol, cyclohexanone).

[0034] Example 3: Analysis of the morphology formation mechanism of different metal systems Combining the key metal parameter table with Figure 5 (Analysis based on the ternary mechanism diagram): The Ni system's high melting point (1455℃) results in an extremely high solid-state diffusion barrier, and the cavitation energy of ultrasound is key to overcoming this initial kinetic limitation. Once the reaction begins, its extremely strong negative enthalpy of formation (-32 to -45 kJ / mol) provides a tremendous chemical driving force, triggering violent interfacial reactions and explosive nucleation. Simultaneously, its extremely low solubility in liquid Ga (<0.01 at.% @50℃) restricts long-range atomic transport, confining the reaction and product accumulation to the vicinity of the interface, ultimately "freezing" to form a micro / nanoporous non-equilibrium structure.

[0035] Ag system: With a low melting point (961℃), the reaction is easily initiated. Its weak enthalpy of formation (-3 to -6 kJ / mol) and mild thermodynamic driving force favor growth towards equilibrium. Simultaneously, its high solubility in liquid Ga (~5.5 at.% @50℃) allows for long-range diffusion of the reactants, supporting anisotropic epitaxial growth along its intrinsic crystal habit, forming regular needle-like crystals. Ultrasound primarily accelerates its growth kinetics but may introduce defects.

[0036] The Cu system has a melting point (1084℃), enthalpy of formation (-8 to -13 kJ / mol), and solubility (~0.5-1.0 at.% @50℃) that are all at intermediate levels. Therefore, its behavior is a transition between the two extreme cases of Ni and Ag, and it eventually forms a composite structure of irregular hexahedrons and lamellar structures.

[0037] The above embodiments demonstrate that the ultrasound-assisted method provided by the present invention is a universal, efficient, and low-temperature metal surface functionalization technology that can rapidly and controllably construct intermetallic compound interfaces with specific morphologies and functions on various metal surfaces, and has important application value in fields such as thermal management, sensing, and catalysis.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for constructing functional interfaces on metal surfaces at low temperatures using ultrasound-assisted liquid gallium, characterized in that, Includes the following steps: (1) Metal substrate pretreatment: The metal substrate is subjected to surface pretreatment to remove the oxide layer and clean the surface. The metal substrate is selected from one or more of Cu, Ag and Ni. (2) Ultrasonic-assisted interface reaction: The pretreated metal substrate is immersed in liquid gallium and placed in an ultrasonic treatment device; under the condition of controlling the reaction temperature ≤50℃, ultrasonic treatment of 50-150 W / L is applied for 5-30 min to make the interface between liquid gallium and metal substrate undergo rapid alloying reaction. (3) Post-processing: After the reaction is completed, the sample is taken out and the unreacted liquid gallium remaining on the surface is removed by centrifugation and / or selective acid washing. Then it is rinsed with deionized water to obtain a modified metal substrate with an intermetallic compound functional layer on the surface.

2. The method according to claim 1, characterized in that, Step (1) includes the following steps: polishing the target metal substrate, immersing it in acid to remove the surface oxide layer, ultrasonically cleaning it with deionized water and anhydrous ethanol, and then drying it.

3. The method according to claim 1, characterized in that, The reaction temperature in step (2) is 40±2℃.

4. The method according to claim 1, characterized in that, The ultrasonic treatment time in step (2) is 5-12 minutes.

5. The method according to claim 1, characterized in that, In step (2), the liquid gallium also contains 5-15 v / v% acetone, and the ultrasonic treatment time is 5-7 min.

6. A surface-functionalized metallic material prepared by the method according to any one of claims 1-5, characterized in that, When the metal substrate is Cu, the functional layer has a composite morphology of irregular hexahedrons and sheets, and the main phase is CuGa2; when the metal substrate is Ag, the functional layer has a regular needle-like crystal morphology, and the main phase is Ag2Ga; when the metal substrate is Ni, the functional layer has a micro-nano porous sponge morphology, and the main phase is NiGa4.

7. An application of the surface-functionalized metallic material as described in claim 6, characterized in that, The material is used to prepare thermal interface materials, surface-enhanced Raman scattering substrates, catalyst supports, or functional coatings.

Images