CN117798504B - Preparation method of reentrant corner structure with adjustable local wettability - Google Patents

Abstract

The invention discloses a method for preparing a concave angle structure with adjustable local wettability, comprising: using a laser to induce microcolumn self-growth on the surface of a base material to obtain a microcolumn structure array; covering the top of the microcolumn structure with a heterogeneous material tape whose material is different from the base material, using a femtosecond laser to in-situ prepare a concave angle top structure on the surface of the heterogeneous material tape to obtain a mushroom head microcolumn structure; spraying a super-hydrophobic coating on the entire base material including the surface of the mushroom head microcolumn structure; using a femtosecond laser to in-situ sweep the super-hydrophobic coating in the central local area of the surface of the heterogeneous material tape, processing a hydrophilic vertex, and preparing a concave angle structure with adjustable local wettability. The concave angle structure prepared by the invention has excellent underwater air film retention and recovery, and has good underwater drag reduction capability.

Description

A method for preparing a concave angle structure with adjustable local wettability

Technical Field

The present invention belongs to the technical field of super-hydrophobic functional materials, and more specifically, relates to a method for preparing a concave angle structure with adjustable local wettability.

Background technique

The frictional resistance encountered by ships during navigation accounts for about 50% of the total resistance, and for underwater torpedoes, submarines, etc., this proportion can be as high as 70%. This not only reduces the speed of ships, but also increases energy consumption and aggravates greenhouse gas emissions. Reducing the frictional resistance generated during the movement process has a significant effect on improving the efficiency of ship transportation, saving energy, reducing greenhouse gas emissions, and reducing pollution. Therefore, the research on drag reduction and efficiency improvement technology has become a common concern in the shipping industry.

Among them, super-hydrophobic surfaces (SHSs) can bind air film layers underwater, transform part of the solid-liquid contact interface into a gas-liquid contact interface, and generate velocity slip on the gas-liquid interface to reduce flow resistance. It is a new and efficient drag reduction method; underwater drag reduction is achieved by constructing a specific hydrophobic microstructure layer on the outer surface of ships and aircraft. It has the advantages of simplicity, economy and marine anti-fouling function, and has potential applications in related fields such as marine engineering. However, most super-hydrophobic materials are prone to collapse or disappearance of the air film sealed on their surface after being disturbed by water flow underwater, thereby affecting or losing underwater drag reduction performance. In order to solve these problems, it is necessary to design a new structure that can maintain a long-term stable air film underwater and have efficient drag reduction performance.

Summary of the invention

An object of the present invention is to solve at least the above-mentioned problems and/or disadvantages and to provide at least the advantages which will be described hereinafter.

In order to achieve these purposes and other advantages according to the present invention, a method for preparing a concave angle structure with adjustable local wettability is provided, comprising the following steps:

Step 1: Using laser to induce micro-pillar self-growth on the surface of the substrate material to obtain a micro-pillar structure array;

Step 2: Cover the top of the micro-column structure with a heterogeneous material tape whose material is different from the base material, and use a femtosecond laser to in-situ prepare a concave corner top structure on the surface of the heterogeneous material tape to obtain a mushroom head micro-column structure;

Step 3: spraying a super-hydrophobic coating on the entire substrate material including the surface of the mushroom head micro-column structure;

Step 4: Use a femtosecond laser to in-situ remove the super-hydrophobic coating in the central local area of the surface of the heterogeneous material tape, process the hydrophilic vertex, and prepare a concave angle structure with adjustable local wettability.

Preferably, the base material is heat-shrinkable polystyrene.

Preferably, in the step one, a femtosecond laser is used to continuously draw a pre-programmed two-dimensional circle on the surface of the base material, and the base material in the two-dimensional circle is separated from the base material on the x-y plane by ablation. As the number of times the laser scans the circle increases, the accumulated heat of the laser causes the underlying base material to shrink and grow, forming a microcolumn structure array.

Preferably, in the step 1, the scanning power of the laser is 100-200 mW, the scanning speed is 30-100 mm/s, and the number of scanning times for each microcolumn structure is 50-80 times.

Preferably, the material of the heterogeneous material tape in step 2 includes one of aluminum foil, polytetrafluoroethylene, polyethylene terephthalate, polyimide, and polydimethylsiloxane.

Preferably, in the step 2, a femtosecond laser is used to continuously draw two-dimensional circles in situ on the heterogeneous material tape covering the top of the micro-pillar structure array until the concave corner top structure is cut out, and the excess heterogeneous material is torn off.

Preferably, the thickness of the heterogeneous material tape on the top of the concave angle structure surface is 50 μm.

Preferably, in step three, the material of the super-hydrophobic coating comprises Glaco solution and hydrophobic silica particles, and the super-hydrophobic coating is sprayed with a spray gun at a distance of 10 cm from the base material.

The invention discloses an application of a concave angle structure with adjustable local wettability, wherein the concave angle structure with adjustable local wettability is applied to construct a hydrophobic microstructure layer on the outer surface of a ship or a spacecraft to achieve underwater drag reduction.

The present invention has at least the following beneficial effects:

First, the concave angle structure is manufactured by laser in situ induced self-growth on the polystyrene (PS) surface. Compared with the traditional micro-nano processing concave angle preparation method, it has the advantages of simple preparation process, short preparation time, flexible control of parameters and adjustable local wettability.

Secondly, the hydrophilic points on the top of the prepared concave angle structure with adjustable local wettability can firmly pin the air-liquid interface underwater, achieving better underwater air film retention while having efficient drag reduction performance;

Third, by utilizing the flexibility of the polystyrene (PS) substrate, its good underwater air film retention and drag reduction performance can be easily transferred to curved surfaces, showing excellent application potential.

Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the preparation process of the concave angle structure with adjustable local wettability in Example 1;

FIG2 is a SEM photograph of a concave angle structure with adjustable local wettability prepared in Example 1;

FIG3 is a comparison diagram of the drag reduction speed in air of the concave angle structures prepared in Example 1 and Comparative Example 1-Comparative Example 2;

FIG4 is a comparison diagram of the changes in drag reduction rate of the concave corner structures prepared in Example 1 and Comparative Example 1-Comparative Example 2 under repeated experiments.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

It should be understood that terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

Example 1

As shown in FIG1 , this embodiment provides a method for preparing a concave angle structure with adjustable local wettability, comprising the following steps:

Step 1: Use a femtosecond laser to continuously draw a pre-programmed two-dimensional circle on the surface of a polystyrene (PS) plate. The scanning power is 140mw, the scanning speed is 50mm/s, and the number of scans is 65 times. The PS layer in the two-dimensional circle is separated from the substrate on the x-y plane by ablation. As the number of laser scanning circles increases, the accumulated heat of the laser causes the PS to shrink and grow, forming a microcolumn structure.

Step 2: Cover the top of the micro-column structure with a layer of aluminum foil tape, use a femtosecond laser to continuously draw a two-dimensional circle until the mushroom head top structure is cut out, and tear off the excess aluminum foil tape to obtain a mushroom head micro-column structure;

Step 3: Spraying Glaco solution, a product of SOFT99, on the entire polystyrene (PS) board including the surface of the mushroom head micro-column structure at a spraying distance of 10 cm to obtain a super hydrophobic coating;

Step 4: Use a femtosecond laser to in-situ remove the super-hydrophobic coating in the central local area of the aluminum foil surface, process the hydrophilic vertex, and prepare a concave angle structure with adjustable local wettability; the concave angle structure prepared in this example is recorded as HMMs.

The contact angle of the concave angle structure in Example 1 was measured to be 121°, the rolling angle was 90°, and it had high adhesion. After 100 drag reduction tests, the drag reduction rate was 43.7%.

Comparative Example 1

This comparative example proposes a method for preparing a concave angle structure with adjustable local wettability, and the preparation method comprises the following steps:

Step 1: Processing of micro-column structure surface: Use femtosecond laser to continuously draw pre-programmed two-dimensional circles on the surface of polystyrene (PS) plate, with a scanning power of 140mw, a scanning speed of 50mm/s, and a scanning frequency of 65 times. The PS layer in the two-dimensional circle is separated from the substrate on the x-y plane by ablation. As the number of laser scanning circles increases, the accumulated heat of the laser causes the PS to shrink and grow, forming a micro-column structure surface.

Step 2: Spraying super-hydrophobic coating: Using Glaco solution, a product of SOFT99, a super-hydrophobic coating was sprayed on a polystyrene (PS) plate at a distance of 10 cm using a spray gun; the concave corner structure prepared in this comparative example was recorded as SHMs.

The contact angle of the structure surface in Comparative Example 1 was measured to be 154°, and the rolling angle was 4°. After 100 drag reduction tests, the drag reduction rate dropped to 18.2%.

Comparative Example 2

This comparative example proposes a concave angle structure with adjustable local wettability, and the preparation method comprises the following steps:

Step 1: Processing of the concave angle structure surface: Use a femtosecond laser to continuously draw a pre-programmed two-dimensional circle on the surface of a polystyrene (PS) plate, with a scanning power of 140mw, a scanning speed of 50mm/s, and a scanning number of 65 times. The PS layer in the two-dimensional circle is separated from the matrix on the x-y plane by ablation. As the number of laser scanning circles increases, the accumulated heat of the laser causes the PS to shrink and grow, thus forming a microcolumn structure.

Step 2: Then, on the aluminum foil tape covering the top of the micro-pillar structure array, a femtosecond laser is used to continuously draw a two-dimensional circle in situ until the concave corner top structure is cut out, and the excess aluminum foil tape is torn off to obtain the concave corner structure;

Step 3: Spraying super-hydrophobic coating: Using Glaco solution, a product of SOFT99, a super-hydrophobic coating was sprayed on a polystyrene (PS) plate at a distance of 10 cm using a spray gun; the concave corner structure prepared in this comparative example was recorded as SHMMs.

The contact angle of the structure surface in Example 2 was measured to be 152°, and the rolling angle was 6°. After 100 drag reduction experiments, the drag reduction rate was 40.9%.

Application Example 1

This application example provides an application of a concave angle structure with adjustable local wettability. The concave angle structure with adjustable local wettability is prepared by Example 1. The concave angle structure with adjustable local wettability is used to construct a hydrophobic microstructure layer on the outer surface of ships and aircraft to achieve underwater drag reduction.

The drag reduction speeds of the original polystyrene microcolumn structure (Hs) in air and water, the drag reduction speeds of the concave angle structure (HMMs) prepared in Example 1, the concave angle structure (SHMs) prepared in Comparative Example 1, and the concave angle structure (SHMMs) prepared in Comparative Example 2 in water were measured respectively, and Figure 3 was obtained. It can be seen from Figure 3 that the speed of Hs passing through the drag reduction test light gate in the air is 176 mm/s. Under the influence of water resistance, its underwater passing speed is reduced to 159 mm/s. The underwater passing speeds of SHMs, SHMMs and HMMs are 165.9 mm/s, 168.6 mm/s and 166.8 mm/s, respectively. The corresponding drag reduction rates are 40.5%, 56.4% and 45.8%, respectively, all of which have obvious drag reduction effects.

The drag reduction rate data of the concave angle structure (HMMs) prepared in Example 1, the concave angle structure (SHMs) prepared in Comparative Example 1, and the concave angle structure (SHMMs) prepared in Comparative Example 2 during 0 to 100 drag reduction tests were measured respectively, and Figure 4 was obtained. It can be seen from Figure 4 that in 75 to 100 deceleration tests, the concave angle structure prepared in Example 1 has a greater drag reduction rate than Comparative Examples 1 and 2, indicating that the concave angle structure prepared in Example 1 can pin the air film more stably underwater, and its drag reduction rate does not change substantially after multiple experiments.

The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims (7)

1. A method for preparing a concave angle structure with adjustable local wettability, characterized in that it comprises the following steps: Step 1: Using laser to induce micro-pillar self-growth on the surface of the substrate material to obtain a micro-pillar structure array; Step 2: Cover the top of the micro-column structure with a heterogeneous material tape whose material is different from the base material, and use a femtosecond laser to in-situ prepare a concave corner top structure on the surface of the heterogeneous material tape to obtain a mushroom head micro-column structure; Step 3: spraying a super-hydrophobic coating on the entire substrate material including the surface of the mushroom head micro-column structure; Step 4: Use a femtosecond laser to in-situ sweep away the super-hydrophobic coating in the central local area of the surface of the heterogeneous material tape, process the hydrophilic vertex, and prepare a concave angle structure with adjustable local wettability; The base material is heat-shrinkable polystyrene; In the step 1, a femtosecond laser is used to continuously draw a pre-programmed two-dimensional circle on the surface of the substrate material, and the substrate material in the two-dimensional circle is separated from the substrate material on the x-y plane by ablation. As the number of times the laser scans the circle increases, the accumulated heat of the laser causes the underlying substrate material to shrink and grow, forming a microcolumn structure array. 2. The method for preparing a concave angle structure with adjustable local wettability according to claim 1, characterized in that in the step 1, the scanning power of the laser is 100-200 mW, the scanning speed is 30-100 mm/s, and the number of scans for each microcolumn structure is 50-80 times. 3. The method for preparing a concave angle structure with adjustable local wettability according to claim 1, characterized in that the material of the heterogeneous material tape in step 2 comprises one of aluminum foil, polytetrafluoroethylene, polyethylene terephthalate, polyimide, and polydimethylsiloxane. 4. The method for preparing a concave angle structure with adjustable local wettability according to claim 1 is characterized in that in the step 2, a femtosecond laser is used to continuously draw a two-dimensional circle in situ on the heterogeneous material tape covering the top of the microcolumn structure array until the concave angle top structure is cut out, and the excess heterogeneous material is torn off. 5. The method for preparing a concave angle structure with adjustable local wettability according to claim 1, characterized in that the thickness of the heterogeneous material tape on the top of the concave angle structure surface is 50 μm. 6. The method for preparing a concave angle structure with adjustable local wettability according to claim 1, characterized in that in the step 3, the material of the super-hydrophobic coating comprises a Glaco solution and hydrophobic silica particles, and the super-hydrophobic coating is sprayed with a spray gun at a distance of 10 cm from the base material. 7. An application of a concave angle structure with locally adjustable wettability, wherein the concave angle structure with locally adjustable wettability is prepared by the preparation method of a concave angle structure with locally adjustable wettability according to any one of claims 1 to 6, and is characterized in that the concave angle structure with locally adjustable wettability is used to construct a hydrophobic microstructure layer on the outer surface of ships and aircraft to achieve underwater drag reduction.