A method for preparing asymmetric wetting Janus materials using diffusion welding

Abstract

The application relates to a method for preparing an asymmetric wetting Janus material by diffusion welding, and relates to a method for preparing an asymmetric wetting Janus material.The application aims to solve the technical problems of the existing Janus material preparation process, such as complexity, small application range and poor mechanical stability.In step one of the application, a porous matrix is connected with a Ti net through diffusion, Ti has high activity at high temperature, can react with and diffuse in different metals or non-metals, and realizes stable connection;in step two of the application, nano structures can be selectively grown on the surface of the porous matrix and the Ti net through a hydrothermal method, so that the micro-roughness of the material is increased; on the other hand, the Ti net is affected by Na + During the hydrothermal process, the Ti net is still hydrophilic after being soaked in an ethyl alcohol stearic acid solution, while the porous matrix side is modified to be hydrophobic, so that the Janus material with asymmetric wetting can be obtained.

Description

Technical Field

[0001] This invention relates to a method for preparing asymmetric wettability Janus materials. Background Technology

[0002] Janus materials typically exhibit different wettability on both sides, with one side being hydrophilic and the other hydrophobic. Thin films or meshes containing Janus materials enable unidirectional transport of droplets and gases; for example, water droplets can enter from the hydrophobic side to the hydrophilic side, but cannot be transported from the hydrophilic side to the hydrophobic side. Therefore, they hold broad application prospects in microfluidics, biomedicine, and other fields of daily life and industry. Currently, there are two main strategies for preparing Janus materials: one is to combine materials with both hydrophilic and hydrophobic properties, and the other is to modify the two sides of a material with a rough microstructure to achieve different wettability. However, the method of combining hydrophilic and hydrophobic materials usually requires complex operations, and the two sides rely on additional mechanical forces or the material's own adhesive forces for bonding, resulting in relatively insufficient mechanical stability. Furthermore, modifying the two sides to have different wettability is relatively difficult, complex, and has limited applicability. Therefore, there is still a need to develop methods that are easy to operate and facilitate large-scale preparation of Janus materials to promote their practical application. Summary of the Invention

[0003] The present invention aims to solve the technical problems of complex preparation process, limited applicability and poor mechanical stability of existing Janus materials, and provides a method for preparing asymmetric wettability Janus materials using diffusion welding.

[0004] The method of preparing asymmetric wettable Janus material using diffusion welding according to the present invention is carried out according to the following steps:

[0005] 1. Diffusion Welding: The porous substrate and Ti mesh are ultrasonically cleaned with anhydrous ethanol for 5-15 minutes and then air-dried. The porous substrate and Ti mesh are then stacked parallel to each other (either can be on top, and one of them can be rotated freely in the plane) and placed between two graphite blocks. A pressure of 0.2-0.5 MPa is applied, and then diffusion welding is performed by heating from room temperature to 750-850°C at a heating rate of 5-15°C / min under vacuum or inert gas protection and holding at that temperature for 2-10 minutes. The substrate is then cooled to room temperature at a cooling rate of 5-15°C / min to obtain the heterogeneous connection structure of the porous substrate / Ti mesh.

[0006] The porous matrix is ​​a metallic or non-metallic material that is stable under vacuum, high temperature, and alkaline solution conditions.

[0007] II. Hydrothermal Treatment: Place the sample prepared in step one into a hydrothermal reactor, add a NaOH aqueous solution with a concentration of 0.5 mol / L to 3 mol / L to completely immerse the sample, and fill the reactor with NaOH aqueous solution at a volume ratio of 40% to 60%. Raise the temperature from room temperature to 200℃ to 280℃ at a heating rate of 5℃ / min to 15℃ / min and hold for 60min to 120min. Cool the sample to room temperature with the furnace, remove the sample, rinse it with deionized water, and then air dry it naturally.

[0008] 3. Modification: Place the sample dried in step 2 into a stearic acid-ethanol solution with a concentration of 0.005 mol / L to 0.02 mol / L (only stearic acid and anhydrous ethanol), let it stand for 5 h to 30 h, then take it out and let it air dry naturally to obtain Janus material with asymmetric wettability. The porous matrix side is hydrophobic and the Ti mesh side is hydrophilic.

[0009] The modifier in step three of this invention is not limited to stearic acid ethanol solution; other modifiers may also be used.

[0010] The design principle of the invention:

[0011] Janus materials require one side to be hydrophilic and the other hydrophobic, with different compositions and properties on both sides. Diffusion welding is often used to join two dissimilar materials, including metals and non-metals, enabling them to form a stable bond with high mechanical properties without affecting the composition and morphology of the two materials themselves. Therefore, diffusion welding has the ability to prepare dissimilar structures.

[0012] In step one of this invention, a porous matrix and a Ti mesh are diffusely bonded. Ti has high reactivity at high temperatures and can react and diffuse with different metals or non-metals, achieving a stable bond. In step two, a hydrothermal method is used to selectively grow nanostructures on the surfaces of the porous matrix and the Ti mesh, increasing the micro-roughness of the material. On the other hand, the Ti mesh is subjected to Na during the hydrothermal process. + Due to the influence of the stearic acid ethanol solution, it remains hydrophilic after immersion treatment, but becomes hydrophobic after modification on one side of the porous matrix. Therefore, Janus materials with asymmetric wettability can be obtained.

[0013] The Ti mesh was originally hydrophilic, and it remains hydrophilic after three steps of treatment; the porous matrix on the other side was also originally hydrophilic, but it becomes hydrophobic after three steps of treatment.

[0014] Furthermore, since diffusion welding can achieve the connection of large-area samples, the method of the present invention is suitable for the preparation of large-size Janus materials and has excellent mechanical stability.

[0015] The present invention has the following beneficial effects:

[0016] 1. The present invention is simple and effective. After stacking the porous matrix and Ti mesh in parallel, pressurizing and heating them under vacuum or protective atmosphere, a heterogeneous structure combining the porous matrix and Ti mesh can be achieved.

[0017] 2. This invention uses hydrothermal treatment and modification to treat both sides of the porous matrix and Ti mesh simultaneously, which can make the two sides have different wettability, and the operation is simple and convenient.

[0018] 3. Diffusion welding, through interfacial reaction and atomic diffusion, results in high dimensional accuracy of sample connections, minimal overall deformation, and high connection strength.

[0019] 4. Ti can form diffusion bonds with a variety of metals and non-metals, thus offering a wide range of porous matrices and broad applications.

[0020] 5. This invention uses diffusion welding to achieve the connection of large-sized heterogeneous materials, and is therefore suitable for preparing large-sized Janus materials with asymmetric wettability;

[0021] This invention proposes a method for preparing asymmetric wettability Janus material using diffusion welding. The method is simple and effective, and the obtained Janus material has excellent properties, including unidirectional water droplet transport capability and good mechanical stability, making it suitable for large-scale application. Attached Figure Description

[0022] Figure 1 An optical micrograph of one side of the Cu mesh after diffusion welding in step one of Experiment 1;

[0023] Figure 2 An optical micrograph of one side of the Ti mesh after diffusion bonding in step one of Experiment 1;

[0024] Figure 3 The image shows a cross-sectional SEM image of the microstructure interface between the Cu mesh and the Ti mesh after diffusion welding in step one of Experiment 1.

[0025] Figure 4 SEM images of the Cu mesh surface morphology of the sample after hydrothermal treatment in step two of Experiment 1.

[0026] Figure 5 SEM images of the Ti mesh surface morphology of the sample after hydrothermal treatment, used in step two of Experiment 1;

[0027] Figure 6 The image shows the static contact angle (WCA) of water droplets on the Cu mesh surface of the sample after modification in step three of Experiment 1.

[0028] Figure 7 The image shows the static contact angle (WCA) of water droplets on the Ti mesh surface of the sample after modification in step three of Experiment 1.

[0029] Figure 8 This is a test photograph taken when the Cu mesh side was facing upwards in Experiment 2;

[0030] Figure 9 This is a test photograph taken with the Ti mesh side facing upwards in Experiment 2.

[0031] Figure 10 This is a schematic diagram of the tensile stress on the sample in Experiment 3;

[0032] Figure 11 This is a graph showing the tensile strength data of the samples in Experiment 3. Detailed Implementation

[0033] Specific Implementation Method 1: This implementation method is a method for preparing asymmetric wettability Janus material using diffusion welding, specifically carried out according to the following steps:

[0034] 1. Diffusion Welding: The porous substrate and Ti mesh are ultrasonically cleaned with anhydrous ethanol for 5 min to 15 min and then air-dried. The porous substrate and Ti mesh are then stacked parallel to each other between two graphite blocks, and a pressure of 0.2 MPa to 0.5 MPa is applied. Then, under vacuum or inert gas protection, the temperature is raised from room temperature to 750℃ to 850℃ at a heating rate of 5℃ / min to 15℃ / min and held for 2 min to 10 min for diffusion welding. The temperature is then cooled to room temperature at a cooling rate of 5℃ / min to 15℃ / min to obtain the heterogeneous connection structure of porous substrate / Ti mesh.

[0035] The porous matrix is ​​a metallic or non-metallic material that is stable under vacuum, high temperature, and alkaline solution conditions.

[0036] II. Hydrothermal Treatment: Place the sample prepared in step one into a hydrothermal reactor, add a NaOH aqueous solution with a concentration of 0.5 mol / L to 3 mol / L to completely immerse the sample, and fill the reactor with NaOH aqueous solution at a volume ratio of 40% to 60%. Raise the temperature from room temperature to 200℃ to 280℃ at a heating rate of 5℃ / min to 15℃ / min and hold for 60min to 120min. Cool the sample to room temperature with the furnace, remove the sample, rinse it with deionized water, and then air dry it naturally.

[0037] 3. Modification: Place the sample dried in step 2 into a stearic acid ethanol solution with a concentration of 0.005 mol / L to 0.02 mol / L, let it stand for 5 h to 30 h, then take it out and let it air dry naturally to obtain Janus material with asymmetric wettability. The porous matrix side is hydrophobic and the Ti mesh side is hydrophilic.

[0038] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the porous matrix mentioned in step one is a metallic material that is stable under vacuum, high temperature, and alkaline solution conditions, such as copper mesh, nickel mesh, iron mesh, tungsten mesh, molybdenum mesh, gold mesh, silver mesh, platinum mesh, stainless steel mesh, or foamed metal. Everything else is the same as in Specific Implementation Method One.

[0039] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the porous matrix mentioned in step one is a non-metallic material that is stable under vacuum, high temperature, and alkaline solution conditions, such as alumina ceramic, silicon nitride ceramic, silicon carbide, or carbon material. Everything else is the same as in Specific Implementation Method One or Two.

[0040] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the vacuum degree in step one is 5 × 10⁻⁶. -4 Pa ~ 5 × 10 -3 Pa. The rest is the same as in any of the specific embodiments one to three.

[0041] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the porous matrix and Ti mesh described in step one are stacked in multiple alternating layers. Everything else is the same as in Specific Implementation Method Four.

[0042] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the heterogeneous interconnection structure of the porous matrix / Ti mesh described in step one is prepared by magnetron sputtering. Everything else is the same as in Specific Implementation Method Five.

[0043] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the inert gas mentioned in step one is argon or a hydrogen-argon mixture. Everything else is the same as in Specific Implementation Method Six.

[0044] The invention was verified using the following experiments:

[0045] Experiment 1: This experiment demonstrates a method for preparing asymmetric wettability Janus materials using diffusion welding, specifically carried out according to the following steps:

[0046] 1. Diffusion Welding: 300-mesh pure copper mesh and 600-mesh Ti mesh were ultrasonically cleaned with anhydrous ethanol for 10 min and air-dried. Then, the copper mesh and Ti mesh were stacked parallel to each other and placed between two graphite blocks. A pressure of 0.25 MPa was applied, and then diffusion welding was performed under vacuum at a heating rate of 10℃ / min from room temperature to 800℃ and held for 5 min. Finally, the temperature was cooled to room temperature at a cooling rate of 10℃ / min to obtain a heterogeneous connection structure of porous matrix / Ti mesh.

[0047] The surface area of ​​the pure copper mesh is 40mm × 30mm;

[0048] Vacuum degree is 5×10 -3 Pa;

[0049] The surface area of ​​the Ti mesh is 40mm × 30mm;

[0050] II. Hydrothermal treatment: Place the sample prepared in step one into a hydrothermal reactor, add a 1.5 mol / L NaOH aqueous solution to completely immerse the sample, and fill the reactor with 50% NaOH aqueous solution. Heat from room temperature to 250℃ at a heating rate of 10℃ / min and hold for 90 min. Cool to room temperature with the furnace, remove the sample, rinse with deionized water, and then air dry.

[0051] 3. Modification: Place the sample dried in step 2 into a 0.01 mol / L stearic acid ethanol solution, let it stand for 24 hours, then remove it and let it air dry naturally to obtain Janus material with asymmetric wettability.

[0052] Figure 1 An optical micrograph of one side of the Cu mesh after diffusion welding in step one of Experiment 1;

[0053] Figure 2 An optical micrograph of one side of the Ti mesh after diffusion bonding in step one of Experiment 1;

[0054] Figure 3 The image shows a cross-sectional SEM image of the micro-bonding interface between the Cu mesh and the Ti mesh after diffusion welding in step one of Experiment 1. It can be seen from the image that the Cu mesh and the Ti mesh have formed a bonding interface.

[0055] Figure 4 The image shows the SEM image of the Cu mesh surface morphology of the sample after hydrothermal treatment, which is the second step in Experiment 1. Figure 5 The image shows the SEM image of the Ti mesh surface morphology of the sample after hydrothermal treatment in step two of Experiment 1. It can be seen from the image that multi-level rough structures were obtained on both sides of the Cu mesh and Ti mesh after diffusion welding and hydrothermal treatment in this experiment.

[0056] Figure 6 This is an image of the static contact angle (WCA) of water droplets on the Cu mesh surface of the sample after modification in step three of Experiment 1. Figure 7 The image shows the static contact angle (WCA) of water droplets on the Ti mesh surface of the sample after modification in step three of Experiment 1. It can be seen from the image that the Cu mesh side is hydrophobic and the Ti mesh side is hydrophilic, proving that Janus material with asymmetric wettability was obtained in this experiment.

[0057] Experiment 2: Support both ends of the Janus material prepared in step 3 of Experiment 1. Figure 8 When the Cu mesh side is facing upwards, water droplets penetrate from the Cu mesh side into the Ti mesh side. Figure 9 When the Ti mesh side is facing upwards, water droplets remain on one side of the Ti mesh and fail to penetrate it, proving that the Janus material prepared in Experiment 1 has unidirectional water permeability.

[0058] Experiment 3: Tensile tests were conducted on the heterogeneous interconnected structure of the porous matrix / Ti mesh prepared in step one of Experiment 1 and the product after hydrothermal treatment in step two. Figure 10 This is a schematic diagram of the sample being stretched. Figure 11 The image shows the tensile strength data of the samples. The left column represents the heterogeneous connection structure of the porous matrix / Ti mesh from step one, while the right column represents the product after hydrothermal treatment in step two. It can be seen that the strengths of both are essentially the same. The modification in step three does not affect the mechanical properties (this is common knowledge in the field). Firstly, the fracture point of the sample is located in the Cu mesh matrix, not at the connection between the Cu and Ti meshes. Secondly, the strength calculation uses macroscopic measurements of the Cu mesh thickness and width, which contain numerous voids; the actual strength borne by the Cu wires in the Cu mesh is much greater than the measured value. Therefore, this demonstrates that the Janus material prepared by this method possesses good mechanical stability.

Claims

1. A method for preparing asymmetric wettability Janus materials using diffusion welding, characterized in that... The method for preparing asymmetric wettability Janus materials using diffusion welding is carried out according to the following steps:

1. Diffusion Welding: The porous substrate and Ti mesh are ultrasonically cleaned with anhydrous ethanol for 5 min to 15 min and then air-dried. The porous substrate and Ti mesh are then stacked parallel to each other between two graphite blocks, and a pressure of 0.2 MPa to 0.5 MPa is applied. Then, under vacuum or inert gas protection, the temperature is raised from room temperature to 750℃ to 850℃ at a heating rate of 5℃ / min to 15℃ / min and held for 2 min to 10 min for diffusion welding. The temperature is then cooled to room temperature at a cooling rate of 5℃ / min to 15℃ / min to obtain the heterogeneous connection structure of porous substrate / Ti mesh. The porous matrix is ​​a metallic or non-metallic material that is stable under vacuum, high temperature, and alkaline solution conditions. II. Hydrothermal Treatment: Place the sample prepared in step one into a hydrothermal reactor, add a NaOH aqueous solution with a concentration of 0.5 mol / L to 3 mol / L to completely immerse the sample, and fill the reactor with NaOH aqueous solution at a volume ratio of 40% to 60%. Raise the temperature from room temperature to 200℃ to 280℃ at a heating rate of 5℃ / min to 15℃ / min and hold for 60min to 120min. Cool the sample to room temperature with the furnace, remove the sample, rinse it with deionized water, and then air dry it naturally.

3. Modification: Place the sample dried in step 2 into a stearic acid ethanol solution with a concentration of 0.005 mol / L to 0.02 mol / L, let it stand for 5 h to 30 h, then take it out and let it air dry naturally to obtain Janus material with asymmetric wettability. The porous matrix side is hydrophobic and the Ti mesh side is hydrophilic.

2. The method for preparing asymmetric wettability Janus material using diffusion welding according to claim 1, characterized in that... The porous matrix mentioned in step one is a metal material that is stable under vacuum, high temperature, and alkaline solution conditions, such as copper mesh, nickel mesh, iron mesh, tungsten mesh, molybdenum mesh, gold mesh, silver mesh, platinum mesh, stainless steel mesh, or foamed metal.

3. The method for preparing asymmetric wettability Janus material using diffusion welding according to claim 1, characterized in that... The porous matrix mentioned in step one is a non-metallic material that is stable under vacuum, high temperature, and alkaline solution conditions, such as alumina ceramics, silicon nitride ceramics, silicon carbide, or carbon materials.

4. The method for preparing asymmetric wettability Janus material using diffusion welding according to claim 1, characterized in that... The vacuum level in step one is 5 × 10⁻⁶. -4 Pa ~ 5 × 10 -3 Pa.

5. The method for preparing asymmetric wettability Janus material using diffusion welding according to claim 1, characterized in that... The porous matrix and Ti mesh mentioned in step one are stacked in multiple alternating layers.

6. The method for preparing asymmetric wettability Janus material using diffusion welding according to claim 1, characterized in that... The heterogeneous interconnection structure of the porous matrix / Ti mesh described in step one is prepared by magnetron sputtering.

7. A method for preparing asymmetric wettability Janus material using diffusion welding according to claim 1, characterized in that... The inert gas mentioned in step one is argon or a mixture of hydrogen and argon.

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