阅读说明：本技术 一种具有高效滴状凝结的金属表面及其制备方法 (Metal surface with efficient dropwise condensation and preparation method thereof ) 是由 龙江游 曹佐 谢小柱 于 2019-08-19 设计创作，主要内容包括：本发明属于金属表面处理技术领域,公开了一种具有高效滴状凝结的金属表面及其制备方法。该金属表面包括亲水区域和超疏水区域；先采用脉冲激光烧蚀金属基材,在金属表面制得周期性凹凸微纳结构；清洗表面后,用低表面能物质修饰凹凸微纳结构,得到超疏水的金属表面；再通过表面精密抛磨或脉冲激光烧蚀去除超疏水的金属表面的周期性凹凸微纳结构中凸起部分的低表面能物质制得；在无低表面能物质的凸起部分的表面形成亲水区域,涂覆低表面能物质的凹入部分为超疏水区域。该金属表面在凝结时,优先在亲水区域形成凝结液滴,由于受到周围超疏水区域的限制,液滴更容易离开金属表面,使表面始终保持滴状凝结状态,提高凝结效率。(The invention belongs to the technical field of metal surface treatment, and discloses a metal surface with efficient dropwise condensation and a preparation method thereof. The metal surface comprises hydrophilic regions and super-hydrophobic regions; firstly, ablating a metal substrate by adopting pulse laser, and preparing a periodic concave-convex micro-nano structure on the surface of the metal; after the surface is cleaned, modifying the concave-convex micro-nano structure by using a low surface energy substance to obtain a super-hydrophobic metal surface; removing low surface energy substances of the convex parts in the periodic concave-convex micro-nano structure on the super-hydrophobic metal surface by surface precision polishing or pulsed laser ablation to prepare the super-hydrophobic metal surface coating; hydrophilic regions are formed on the surfaces of the convex portions free of the low surface energy substance, and the concave portions coated with the low surface energy substance are super-hydrophobic regions. When the metal surface is coagulated, the coagulated liquid drops are preferentially formed in the hydrophilic area, and the liquid drops are more easily separated from the metal surface due to the limitation of the surrounding super-hydrophobic area, so that the surface is always kept in a drop-shaped coagulation state, and the coagulation efficiency is improved.)

1. A metal surface having highly efficient droplet condensation, wherein the metal surface comprises hydrophilic regions and superhydrophobic regions; firstly, ablating a metal substrate by adopting pulse laser, and preparing a periodic concave-convex micro-nano structure on the surface of the metal; after the surface is cleaned, modifying the concave-convex micro-nano structure by using a low surface energy substance to obtain a super-hydrophobic metal surface; removing low surface energy substances of the convex parts in the periodic concave-convex micro-nano structure on the super-hydrophobic metal surface by surface precision grinding or pulsed laser ablation to prepare the super-hydrophobic metal surface coating; hydrophilic regions are formed on the surfaces of the raised portions that are free of low surface energy species, while the recessed portions coated with low surface energy species are superhydrophobic regions.

2. The metal surface with high efficiency of droplet condensation according to claim 1, wherein the metal substrate is copper, copper alloy, aluminum alloy, steel or titanium alloy.

3. The metal surface with efficient droplet condensation according to claim 1, wherein the pulsed laser can be a nanosecond laser, a picosecond laser, or a femtosecond laser; the pulse width of the pulse laser is 200 femtoseconds to 10 nanoseconds; the laser in the pulse laser is infrared light, visible light or ultraviolet light, and the laser wavelength in the pulse laser is 300-1100 nm; the pulse repetition frequency of the pulse laser is 10 kHz-2 MHz.

4. The metal surface with efficient dropwise condensation according to claim 1, wherein the period of the concave-convex periodic micro-nano structure is 1-100 μm; the convex part in the concave-convex periodic micro-nano structure is in a conical shape, a trapezoid shape, a mastoid shape or a convex block, and the concave part is in an inverted triangle shape, an inverted trapezoid shape or a groove.

5. The metal surface with high efficiency drop-shaped condensation according to claim 4, wherein the height of the raised part in the concavo-convex periodic micro-nano structure is 1-50 μm.

6. The metal surface with efficient droplet coagulation as claimed in claim 1, wherein the surface of the super-hydrophobic region is further attached with particles generated by laser ablation, and the particle size of the particles is 10-1000 nm.

7. The method of claim 1 wherein the low surface energy material is a material having a surface energy of less than 25mJ/m²Is less than 25 mN/m.

8. The metal surface with efficient droplet coagulation of claim 7, wherein the low surface energy material is one or more of a siloxane, fluorosilane, or fatty acid.

9. The metal surface with highly effective droplet coagulation as claimed in claim 1, wherein the hydrophilic region has a water surface contact angle of 0.1 to 90 ° and an area of 0.1 to 500 μm²(ii) a The water surface contact angle of the super-hydrophobic area is 150-180 degrees; the thickness of the protruding part for removing the periodic concave-convex micro-nano structure is 0.1-5 mu m.

10. The method for preparing a metal surface with efficient droplet condensation according to any of claims 1-9, characterized by comprising the following specific steps:

s1, ablating a metal base material by using pulse laser to obtain a convex-concave periodic surface micro-nano structure on the surface of the metal base material;

s2, modifying the metal surface of the concave-convex periodic surface micro-nano structure by using a low-surface-energy substance to obtain a super-hydrophobic concave-convex micro-nano structure;

s3, removing low surface energy substances of the convex part of the periodic concave-convex micro-nano structure through surface precision grinding or pulse laser ablation to obtain the material; hydrophilic regions are formed on the surfaces of the raised portions that are free of low surface energy species, while the recessed portions coated with low surface energy species are superhydrophobic regions.

Technical Field

The invention belongs to the technical field of metal substrate surface treatment, and particularly relates to a metal bonding surface with efficient dropwise condensation and a preparation method thereof.

Background

The process of water vapor becoming water upon cooling is known as condensation. Coagulation is a key step in industrial processes such as power generation, seawater desalination, thermal management and the like. On the surface of the solid, the condensation process of water vapor includes two forms of drop condensation and film condensation. When the film is condensed, the condensed liquid drops form a water film on the surface, so that the subsequent condensation and heat exchange processes are blocked, and the condensation efficiency is influenced. On the contrary, when the drops are condensed, the condensed liquid leaves the surface when growing to a certain degree, so that the solid surface always has an area in a naked state, thereby improving the efficiency of condensation and heat exchange. The condensation and heat exchange efficiency of the drop condensation is far higher than that of the film condensation.

The conventional means for forming drop-shaped coagulation is to perform hydrophobic modification on the surface of the material, weaken the wetting and spreading of the coagulation liquid drop on the surface and enable the coagulation liquid drop to leave the surface more easily. However, it is difficult to maintain the state of dropwise coagulation for a long time in practical use by conventional hydrophobic modification. In recent years, with the development of nanotechnology, a super-hydrophobic surface with a lotus effect has attracted much attention due to its extremely strong water repellency. When the super-hydrophobic surface is applied to condensation, water vapor can partially enter the surface microstructure, so that the super-hydrophobic surface is partially failed, the liquid is prevented from being separated, and the condensation performance of the super-hydrophobic surface is influenced. Thus, some techniques accelerate the detachment of the liquid by additional means. For example, patent CN 102269539B discloses a method for controlling the diameter of drops when they fall off by applying a wide frequency vibration to a superhydrophobic surface. However, these techniques are relatively complex and costly to apply. How to accelerate the separation of liquid and maintain efficient drop-shaped condensation by treating the surface per se has urgent practical significance.

Disclosure of Invention

To address the above-discussed deficiencies and drawbacks of the prior art, it is a primary object of the present invention to provide a metal surface having highly efficient droplet condensation.

It is another object of the present invention to provide a method for preparing the above metal surface with highly efficient droplet condensation. The method comprises the steps of preparing a conical periodic surface micro-nano structure on a metal surface by using pulse laser, matching with surface hydrophobic modification to realize a super-hydrophobic matrix, and removing the top of the conical structure by surface fine grinding or selective laser ablation to obtain a micron-sized local hydrophilic region. In the condensation process, condensation preferentially occurs in the hydrophilic region, and is limited by the surrounding sunken super-hydrophobic region in the growing process, so that the condensed liquid drops quickly leave the surface, the falling of the condensed liquid drops on the surface is accelerated, and the condensation efficiency is finally improved.

The purpose of the invention is realized by the following technical scheme:

a metal surface having highly efficient droplet condensation, said metal surface comprising hydrophilic regions and superhydrophobic regions; firstly, ablating a metal substrate by adopting pulse laser, and preparing a periodic concave-convex micro-nano structure on the surface of the metal; after the surface is cleaned, modifying the concave-convex micro-nano structure by using a low surface energy substance to obtain a super-hydrophobic metal surface; removing low surface energy substances of the convex parts in the periodic concave-convex micro-nano structure on the super-hydrophobic metal surface by surface precision polishing or pulsed laser ablation to prepare the super-hydrophobic metal surface coating; hydrophilic regions are formed on the surfaces of the raised portions that are free of low surface energy species, while the recessed portions coated with low surface energy species are superhydrophobic regions.

Preferably, the metal substrate is copper, a copper alloy, aluminum, an aluminum alloy, steel or a titanium alloy.

Preferably, the pulsed laser may be a nanosecond laser, a picosecond laser, or a femtosecond laser; the pulse width of the pulse laser is 200 femtoseconds to 10 nanoseconds; the laser in the pulse laser is infrared light, visible light or ultraviolet light, and the laser wavelength in the pulse laser is 300-1100 nm; the pulse repetition frequency of the pulse laser is 10 kHz-2 MHz.

Preferably, the period of the concave-convex periodic micro-nano structure is 1-100 μm, the convex part in the concave-convex periodic micro-nano structure is in a cone shape, a trapezoid shape, a mastoid shape or a convex block, and the concave part is in an inverted triangle shape, an inverted trapezoid shape or a groove.

Preferably, the height of the convex part in the concave-convex periodic micro-nano structure is 1-50 μm.

Preferably, particles generated by laser ablation are further attached to the surface of the super-hydrophobic region, and the particle size of the particles is 10-1000 nm.

Preferably, the low surface energy substance is a substance with a surface energy of less than 25mJ/m²Is less than 25 mN/m.

More preferably, the low surface energy material is one or more of siloxane, fluorosilane, or fatty acid.

Preferably, the water surface contact angle of the hydrophilic region is 0.1-90 degrees, and the area of the hydrophilic region is 0.1-500 mu m²(ii) a The water surface contact angle of the super-hydrophobic area is 150-180 degrees; the thickness of the protruding part for removing the periodic concave-convex micro-nano structure is 0.1-5 mu m.

The preparation method of the metal surface with efficient dropwise condensation comprises the following specific steps:

s1, ablating a metal base material by using pulse laser to obtain a convex-concave periodic surface micro-nano structure on the surface of the metal base material;

s2, modifying the metal surface of the concave-convex periodic surface micro-nano structure by using a low-surface-energy substance to obtain a super-hydrophobic concave-convex micro-nano structure;

s3, removing low surface energy substances of the convex part of the periodic concave-convex micro-nano structure through surface precision polishing or pulse laser ablation to obtain the material; hydrophilic regions are formed on the surfaces of the raised portions that are free of low surface energy species, while the recessed portions coated with low surface energy species are superhydrophobic regions.

The laser ablation removal in the preparation method provided by the invention means that when the energy density of the pulse laser exceeds the ablation threshold of a certain material, the evaporation and melting phenomena occur on the surface of the material in a laser action area to remove the formed material, and the removal amount depends on laser parameters.

Compared with the prior art, the invention has the following beneficial effects:

1. the method comprises the steps of preparing a concave-convex periodic surface micro-nano structure on a metal surface by pulse laser, matching surface modification of low free energy substances to obtain a super-hydrophobic metal surface, and removing the top of the concave-convex periodic surface micro-nano structure by surface precision grinding or selective pulse laser ablation to obtain the metal surface with the concave-convex micro-nano structure with the convex part having hydrophilicity and the periphery having super-hydrophobicity. In the condensation process, the metal surface prepared by the method can accelerate the separation of condensation liquid drops and improve the condensation efficiency.

2. According to the invention, the concave-convex periodic surface micro-nano structure is formed by ablating the surface of the metal material by using laser, the prepared structure is stable, and the period and the depth of the micro-nano structure can be adjusted, so that the final condensation effect can be adjusted, and the method has great flexibility and designability.

3. The invention removes the convex part of the concave-convex periodic surface micro-nano structure by surface precision grinding or selective pulse laser ablation, and the removal depth can be better controlled, thereby realizing the distribution of hydrophilic and super-hydrophobic areas with different proportions.

4. The invention promotes the condensation process by the concave-convex micro-nano structure with hydrophilic convex part and super-hydrophobic periphery. The hydrophilic convex area is beneficial to rapid nucleation of steam to form micron-sized liquid drops, the existence of the surrounding super-hydrophobic area inhibits the interconnection of micron-sized condensed liquid drops, and the formation of large condensed liquid drops is avoided. Meanwhile, the micron-sized liquid drops are more easily dropped from the surface under the constraint of the surrounding super-hydrophobic matrix, so that the coagulation process is accelerated. Compared with the common super-hydrophobic surface, even if the super-hydrophobic part is partially ineffective, because the raised hydrophilic area is higher than the surrounding super-hydrophobic area, and the area of the hydrophilic area is small, the condensed liquid drops still can be separated from the surface more easily under the action of gravity.

Drawings

Fig. 1 is an electron micrograph of the aluminum metal surface with highly efficient droplet condensation in example 1.

Fig. 2 is a schematic diagram of the contact angle of a droplet on the surface of aluminum metal with highly efficient droplet-like condensation in example 1.

Fig. 3 is a photograph comparing the coagulation of the aluminum metal surface with the highly efficient droplet coagulation in example 1 and a general aluminum metal surface.

Detailed Description

The following examples are presented to further illustrate the present invention and should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.