阅读说明：本技术 一种有序封闭式微纳复合结构防冰表面及其制备方法 (Ordered closed micro-nano composite structure anti-icing surface and preparation method thereof ) 是由 颜黄苹 陈子露 王子俊 尹靖博 于 2021-06-22 设计创作，主要内容包括：本发明涉及一种功能性表面工程领域,具体涉及有序封闭式微纳复合结构防冰表面及其制备方法,综合脉冲激光及水热法进行表面微纳化处理,形成有序封闭式微纳复合结构防冰表面,有序封闭式结构间的空气能阻止水滴的渗入,进而降低表面与水滴间的热传递,从而延长结冰时间,防冰效果相对较好,所述有序封闭式微纳复合结构表面具有疏水性,可延缓结冰时间,降低冰层与表面粘附力,增强表面的机械稳定性。(The invention relates to the field of functional surface engineering, in particular to an ordered closed micro-nano composite structure anti-icing surface and a preparation method thereof.)

1. The ordered closed micro-nano composite structure anti-icing surface is characterized by comprising a plurality of tangent periodic tubular microstructures distributed on a metal substrate, wherein the tubular microstructures are provided with nano structures, the tubular microstructures and the nano structures form a micro-nano composite structure, air gaps exist among the tubular microstructures, and air gaps exist among the micro-nano composite structures.

2. The ordered closed micro-nano composite structure anti-icing surface according to claim 1, wherein the nanostructures comprise hairy nanostructures, colloidal nanostructures, small pore nanostructures, and/or coral nanostructures.

3. The ordered closed micro-nano composite structure anti-icing surface according to claim 1, wherein a plurality of tangential periodic tubular microstructures are arranged in order on the surface of the metal substrate.

4. The ordered closed micro-nano composite structure anti-icing surface according to claim 1, wherein the cross section of the tubular microstructure is circular.

5. The ordered closed micro-nano composite structure anti-icing surface as claimed in claim 1, wherein the characteristic dimension of the tubular microstructure is 180-220 μm, the outer diameter R of the tubular microstructure is 90-110 μm, the inner diameter R is 45-55 μm, the height h is 50-60 μm, and the depth d of the inner ring is 50-60 μm.

6. The method for preparing the anti-icing surface of the ordered closed micro-nano composite structure according to any one of claims 1 to 5 is characterized by comprising the following steps:

s1: polishing and cleaning a metal substrate to be processed;

s2: constructing a closed periodic tubular microstructure on the smooth surface of a metal substrate by using pulse laser, and cleaning the metal surface by using deionized water after laser processing;

s3: carrying out hydrothermal oxidation on the metal surface obtained by laser processing to obtain a nano structure on the tubular microstructure on the metal surface;

s4: and carrying out surface low-energy treatment on the metal surface to obtain the micro-nano composite structure surface with the anti-icing characteristic.

7. The method for preparing an anti-icing surface of an ordered closed micro-nano composite structure according to claim 6, wherein the metal substrate in the step S1 is made of titanium alloy, aluminum alloy or other metals, the polishing step is to polish and grind the metal surface by using different types of sand paper, the cleaning method is to wash the residues on the ground metal surface by using deionized water, place the washed residues in absolute ethyl alcohol for ultrasonic cleaning, wash the residual absolute ethyl alcohol on the surface by using the deionized water after being taken out, and blow-dry the metal surface by using nitrogen.

8. The method for preparing an anti-icing surface according to the ordered closed micro-nano composite structure of claim 6, wherein the plurality of periodic tubular microstructures on the surface of the metal substrate are arranged in a tangential and ordered manner and in a closed manner in step S2.

9. The method for preparing an anti-icing surface with an ordered closed micro-nano composite structure according to claim 6, wherein the step S3 of oxidizing the metal surface by a hydrothermal method is to put a metal substrate obtained by laser processing into H with the temperature of 60-110 ℃₂O₂Oxidizing in the solution for 1-9h, washing impurities on the surface of the metal by using clear water after the oxidation is finished, then placing the metal on a heating plate at 450 ℃ for high-temperature heating for 1 hour, and then annealing at the speed of 5 ℃ per minute until the temperature is reduced to normal temperature, so that a nano structure grows on the periodic tubular microstructure on the surface of the metal, and the surface of the micro-nano composite structure is obtained.

10. The method for preparing an anti-icing surface of an ordered closed micro-nano composite structure according to claim 6, wherein the low-energy treatment method in the step S3 is to place the metal surface of the micro-nano composite structure in a prepared 2 wt% heptafluoro-decaalkyl trimethoxy silane (Fas-17) ethanol solution, the solution is required to completely cover the surface of the sample for soaking, and the sample is taken out and placed in the air for airing after being soaked for 24 hours.

Technical Field

The invention relates to the field of functional surface engineering, in particular to a surface treatment method for improving the anti-icing performance of a metal surface by performing surface micro-nano treatment by combining pulse laser and a hydrothermal method.

Background

Icing is a ubiquitous natural phenomenon on metal surfaces. The problem of icing on metal low-temperature cold surfaces widely relates to important industrial fields such as aerospace, wind power/photovoltaic power generation, heat transfer, heat dissipation, refrigeration, transportation, electric power communication and the like. Under certain conditions, the adhesion and accumulation of frost on the low-temperature cold surface not only can reduce the performance and the operation efficiency of equipment, but also can bring huge economic loss in severe cases, thereby threatening the life and property safety of people. In view of serious harm of icing to production and life, the anti-icing performance of the metal low-temperature cold surface and the control technology thereof are one of the key points and hot points of urgent attention in the relevant research field.

In recent years, the application of a superhydrophobic surface with a micro-nano structure to ice prevention has received extensive attention in related research fields. The anti-icing means that the icing time of the supercooled water is prolonged, so that the supercooled water has enough time to be separated from an icing surface by the action of gravity, wind power, centrifugal force and the like before solidification. A large number of researches show that the super-hydrophobic surface can prolong the icing induction time of surface water drops, has smaller adhesion to frost and reduces the tendency of ice accumulation.

Generally, the ice formation on the surface of the material is formed by a cooling nucleation mechanism of water droplets. The change in the amount of heat per unit time of the water droplet is the difference between the amount of heat taken from the air per unit time by thermal conduction and radiation and the amount of heat transferred to the base material. When water drops fall on the surface of the base material, if the contact area between the water drops and the surface of the base material is small, the heat transferred to the base material is reduced, and the change value of the heat per unit time is increased and the drop temperature of the water drops is reduced, so that the water drops are not easy to freeze. According to the inspiration, the micro-nano structure on the surface of the substrate material has an important influence on the anti-icing performance of the substrate material.

At present, the micro-nano structure on the surface of the base material for ice prevention is mostly an open micro-nano structure array, such as a cylinder, a cuboid, a cone and other micro-nano arrays. The open micro-nano structure has poor mechanical performance and stability, and is easy to damage due to mechanical actions such as processing, extremely severe environment, impact, friction and the like in the using process, so that the durability of the anti-icing performance is poor. If the practical application condition is considered, no matter the airplane wing or various equipment exposed in the air is frozen, water drops often drop on the surface of an object from a high position, the pressure stability of the open type microstructure is poor, the structure is easy to damage, and when the liquid drops collide, the hydrophobicity often fails, so that the anti-icing effect is poor.

At present, for the preparation of surface micro-nano structure, common methods such as sol-gel method, chemical vapor deposition method, electrostatic spinning method, anodic oxidation method, template method, chemical etching method, nano-imprinting method, electrodeposition method and self-assembly method are used. Although the preparation methods have specific advantages, the corresponding disadvantages cannot be ignored, such as high cost, complex preparation steps, material limitation, insufficient controllability of micro-nano structures and the like.

Disclosure of Invention

Based on the above, the ordered closed micro-nano composite structure anti-icing surface and the preparation method thereof are needed to be provided, and the key for improving the anti-icing performance of the surface of the metal substrate is to construct a reasonable and ordered closed micro-nano structure so as to enhance the mechanical stability and the dynamic anti-icing performance of the surface and prolong the icing time.

In order to achieve the purpose, the invention provides an ordered closed micro-nano composite structure anti-icing surface which comprises a plurality of tangent periodic tubular microstructures distributed on a metal substrate, wherein the tubular microstructures are provided with nano structures, the tubular microstructures and the nano structures form a micro-nano composite structure, air gaps exist among the tubular microstructures, and the micro-nano composite structure has air gaps.

Further, the nanostructure comprises an antler-like nanostructure, a colloidal nanostructure, a small-pore nanostructure, and/or a coral nanostructure.

Further, a plurality of tangential periodic tubular microstructures are arranged in an ordered manner on the surface of the metal substrate.

Further, the cross section of the tubular microstructure is circular.

Further, the characteristic dimension of the tubular microstructure is 180-220 μm, preferably 200 μm. The outer diameter R of the tubular microstructure is 90-110 μm, the inner diameter R is 45-55 μm, the height h is 50-60 μm, and the depth d of the inner ring is 50-60 μm.

Furthermore, the size of the nano structure is 100 nm-1 μm.

The invention also provides a preparation method of the ordered closed micro-nano composite structure anti-icing surface, which comprises the following steps:

s1: polishing and cleaning a metal substrate to be processed;

s2: constructing a closed periodic tubular microstructure on the smooth surface of a metal substrate by using pulse laser, and cleaning the metal surface by using deionized water after laser processing;

s3: carrying out hydrothermal oxidation on the metal surface obtained by laser processing to obtain a nano structure on the tubular microstructure on the metal surface;

s4: and carrying out surface low-energy treatment on the metal surface to obtain the micro-nano composite structure surface with the anti-icing characteristic.

Further, the nanostructure comprises an antler-like nanostructure, a colloidal nanostructure, a small-pore nanostructure, and/or a coral nanostructure.

Further, the metal substrate in the step S1 is made of titanium alloy, aluminum alloy or other metals, the polishing step is to polish and polish the metal surface by using different types of abrasive paper, the cleaning method is to wash the residues on the polished metal surface by using deionized water, and place the residues in absolute ethyl alcohol for ultrasonic cleaning, after taking out, the residual absolute ethyl alcohol on the surface is washed by using deionized water, and the metal surface is dried by nitrogen.

Further, in step S2, the plurality of periodic tubular microstructures on the surface of the metal substrate are arranged tangentially and orderly to form a closed structure. In step S2, active control of the periodic microstructure on the metal surface can be achieved by optimizing the parameters of the pulse laser processing technique (laser pulse width, repetition frequency, laser power, scanning speed, scanning interval, scanning frequency, etc.).

Further, the hydrothermal oxidation of the metal surface in step S3 is performed by placing the laser processed metal substrate in H at 60-110 ℃₂O₂Oxidizing in the solution for 1-9h, washing impurities on the surface of the metal by using clear water after the oxidation is finished, then placing the metal on a heating plate at 450 ℃ for high-temperature heating for 1 hour, and then annealing at the speed of 5 ℃ per minute until the temperature is reduced to normal temperature, so that a nano structure grows on the periodic tubular microstructure on the surface of the metal, and the surface of the micro-nano composite structure is obtained. The nano structure can be controlled by the length of the oxidation time, and is in an antler shape, a colloid shape, a small hole shape, a coral shape and a coral shape when the oxidation time is 1h, 3h, 5h, 7h and 9h, namely the change is not obvious when the oxidation time exceeds 7 h.

Further, the low-energy processing method in the step S3 is to put the micro-nano composite structure metal surface into a prepared 2 wt% heptafluoro-decaalkyl trimethoxy silane (Fas-17) ethanol solution, the solution needs to completely cover the sample surface for soaking, and the sample surface is taken out and put into the air for drying after 24 hours of soaking.

Different from the prior art, the technical scheme has the following beneficial effects:

(1) according to the invention, an ordered closed micro-nano structure design is adopted, the contact area between water drops and a substrate material is reduced by the rough surface of the structure, the air captured between surface gaps in the icing process is not influenced by the outside, an air gap exists between the tubular micro-structure and the micro-nano composite structure, the air between the ordered closed structure can prevent the water drops from permeating, and further the heat transfer between the surface and the water drops is reduced, so that the icing time is prolonged, the anti-icing effect is relatively good, the surface of the ordered closed micro-nano composite structure has hydrophobicity, the icing time can be delayed, the adhesion force between an ice layer and the surface is reduced, and the mechanical stability of the surface is enhanced.

(2) Compared with an open micro-nano structure, the closed micro-nano structure has the advantages that local impact can be effectively dispersed on the whole surface due to the continuity of the whole wall structure, the pressure stability is high, the impact of liquid drops dropping from a high position can be resisted, the water drops are quickly bounced off, the impact resistance is high, the hydrophobicity is kept, and the dynamic anti-icing performance of the closed structure is superior to that of the open structure.

(3) The pulse laser provided by the invention is used for processing the periodic microstructure, the preparation cost is low, the steps are simple, the controllability of the microstructure is good, and meanwhile, the pulse laser has the advantages of non-contact, high precision, repeatability, flexibility, environmental protection and the like, so that the pulse laser is a powerful tool for replacing the traditional micromachining method.

(4) The invention provides a method for combining laser micro-nano texture with a hydrothermal method, and the surface is subjected to low-energy post-treatment, so that the surface has super-hydrophobicity, the icing time can be delayed, and the adhesion between an ice layer and the surface can be reduced.

Drawings

FIG. 1 is a schematic view of a pulsed laser process for preparing a microstructure on a metal surface according to an embodiment of the present invention;

FIG. 2 is an enlarged partial schematic view of FIG. 1;

FIG. 2 is a flow chart of a preparation method of a metal surface micro-nano composite structure according to an embodiment of the invention;

FIGS. 3 a-3 l are electron micrographs of nano-scale structures on a metal surface at different oxidation times after laser texturing, in accordance with one embodiment of the present invention; wherein FIGS. 3 a-3 b show unoxidized electron micrographs; FIGS. 3 c-3 d show electron micrographs of oxidation time 1 h; FIGS. 3 e-3 f show electron micrographs of oxidation time 3 h; FIGS. 3 g-3 h show electron micrographs of oxidation time 5 h; FIGS. 3 i-3 j show electron micrographs of oxidation time 7 h; FIGS. 3 k-3 l show electron micrographs of oxidation time 9 h;

FIG. 4 is a schematic view of a conventional metal surface in contact with a water droplet;

FIG. 5 is a schematic view of a surface of an enclosed structure in contact with a water droplet according to one embodiment of the present invention;

FIG. 6 is a flow chart of a second metal surface micro-nano composite structure preparation method according to an embodiment of the invention;

FIG. 7 is a schematic view of a laser processing system according to a second embodiment of the present invention;

FIG. 8 is a schematic view of a platform for testing the tangential adhesion of ice on a metal surface according to an embodiment of the present invention.

FIG. 9 is a schematic diagram of a normal adhesion force testing platform for icing on a metal surface according to an embodiment of the invention.

Description of reference numerals:

1. metal substrate, 2, tubular microstructure, 3, nanostructure, 4, air gap.

Detailed Description

To explain technical contents, structural features, and objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.

Example one

Referring to fig. 1 and fig. 2, the ordered closed micro-nano composite structure anti-icing surface of the embodiment includes a plurality of tangential periodic tubular microstructures 2 distributed on a metal substrate 1, and the metal substrate 1 may be selected from, but not limited to, metals such as titanium alloy and aluminum alloy. The tubular microstructures 2 with the same shape and size are orderly arranged on the surface of the metal substrate and periodically and repeatedly arranged on the metal substrate 1, the adjacent tubular microstructures 2 are mutually tangent, and all the tubular microstructures on the whole metal substrate 1 are mutually tightly abutted to fill the whole surface of the metal substrate 1. The tubular microstructures 2 are provided with nano structures 3, the tubular microstructures 2 and the nano structures 3 form micro-nano composite structures, air gaps 4 exist among the tubular microstructures 2, and air gaps exist among the micro-nano composite structures.

Referring to fig. 2, the tubular microstructure 2 has a circular cross-section. The characteristic dimension of the tubular microstructure 2 is 180-220 μm, preferably 200 μm. The outer diameter R of the tubular microstructure 2 is 90-110 μm, the inner diameter R is 45-55 μm, the height h is 50-60 μm, and the depth d of the inner ring is 50-60 μm.

Referring to fig. 3 a-3 l, the nanostructures 3 comprise hairy, colloidal, small-pore and/or coral-like nanostructures. The size of the nano structure is 100 nm-1 μm.

To further analyze the beneficial effects of the present embodiment in principle, the process of contacting the common metal surface and the metal surface of the present embodiment with water droplets, respectively, is illustrated and explained herein. Referring to fig. 4, fig. 4 is a schematic view of a common metal surface in contact with a water droplet; because the whole metal surface is a smooth hydrophilic plane, water drops are directly adsorbed on the metal surface, and the contact area of the whole water drops and the metal surface is large, the heat conducted to the metal surface is large, the heat change value of the water drops in unit time is reduced, the drop temperature of the water drops is large, and therefore the water drops are easy to freeze.

Referring to fig. 5, in the schematic diagram of the contact between the surface of the closed structure and the water droplet in the embodiment of the present invention, a composite micro-nano structure formed by a nano structure 3 on a tubular microstructure 2 is adopted in the embodiment, the middle of the whole tubular microstructure 2 is concave, the edge is narrow, when the water droplet falls on the upper side, the contact area between the water droplet and the metal surface is small, especially in the hollow position of the tubular microstructure, the air in the tubular microstructure gap on the metal surface can prevent the water droplet from infiltrating, the water droplet is suspended on the hollow surface with the periodic tubular microstructure, a certain interval is formed between the water droplet and the metal surface, and the heat transfer between the metal surface and the water droplet is reduced, so that the freezing time is prolonged. The closed tubular microstructures are tangent and tightly abutted with each other, so that the distance between the microstructures is reduced, the blocking capability to water drops is improved, and the anti-icing effect is greatly enhanced. The surface of the closed micro-nano structure can effectively disperse local impact to the whole surface due to the continuity of the whole wall structure, has stronger pressure stability and higher impact resistance, can resist the impact of liquid drops dropping from a high position, and keeps hydrophobic property, so the dynamic anti-icing property of the closed structure is superior to that of an open structure. Therefore, the ordered closed micro-nano structure can greatly enhance the mechanical stability and dynamic anti-icing property of the metal surface, prolong the icing time and greatly improve the anti-icing property of the metal substrate surface.

Example two

Referring to fig. 6, the figure illustrates a flow chart of a preparation method of a metal surface micro-nano composite structure, and the second embodiment provides a preparation method of an ordered closed micro-nano composite structure anti-icing surface, which includes the following steps:

s1: polishing and cleaning a metal substrate to be processed; the metal substrate in the step S1 is made of titanium alloy, aluminum alloy or other metals, the polishing step is to polish and polish the metal surface by using 200#, 500# and 1000# abrasive paper, the cleaning method is to wash the residues on the polished metal surface by using deionized water, place the residues in absolute ethyl alcohol for ultrasonic cleaning for five minutes, wash the residual absolute ethyl alcohol on the surface by using the deionized water after taking out the residues, and blow-dry the metal surface by nitrogen.

S2: referring to fig. 7, a schematic of a laser machining system is illustrated. Constructing a closed periodic tubular microstructure on the smooth surface of a metal substrate by using high-speed pulse laser, and cleaning the metal surface by using deionized water after laser processing; the high-speed pulse laser adopts femtosecond pulse laser, and the laser processing setting parameters are as follows: the laser pulse energy density is 40-60J/cm²The pulse repetition frequency is 15-25kHz, the spot diameter is 30-40 μm, the pulse duration is 200-400ns, the laser speed is 800-1200mm/s, the processing times are 5-15, and the laser line spacing is 0.008-0.012 mm. And cleaning the surface with deionized water after laser processing to obtain a closed microstructure. In step S2, the plurality of periodic tubular microstructures on the surface of the metal substrate are arranged in a tangent and ordered manner.

S3: oxidizing the metal surface obtained by laser processing to obtain a nano structure on the tubular microstructure of the metal surface; the surface oxidation method comprises the step of putting a surface sample obtained by laser processing into H respectively at reaction temperatures of 60 ℃, 80 ℃ and 100 DEG C₂O₂Oxidizing in the solution for 1h, 3h, 5h and 7h respectively, washing surface impurities with clear water after the oxidation is finished, placing on a heating plate at 450 ℃ for high-temperature heating for 1h, then annealing at the speed of 5 ℃ per minute until the temperature is reduced to normal temperature, and growing a nano structure on the microstructure of the sample to obtain the micro-nano composite structure surface. Wherein the nanometer structure is different with the oxidation time, and the nanometer structure is in the shape of hairy, colloidal, small-hole and coral when the oxidation time is 1h, 3h, 5h and 7h。

S4: and carrying out surface low-energy treatment on the metal surface to obtain the micro-nano composite structure surface with the anti-icing characteristic. The low-energy treatment method comprises the following steps of mixing heptafluoro decaalkyl trimethoxy silane (Fas-17) and absolute ethyl alcohol according to the mass ratio of 1: 49 are proportioned and stirred to give a 2% wt. Fas-17 ethanol solution. And (3) putting the microstructure sample into a prepared 2 wt% Fas-17 ethanol solution, wherein the solution needs to completely cover the surface of the sample to be soaked for 24 hours, and taking out the sample to be placed in the air to be dried.

The second embodiment also provides a performance detection method of the anti-icing surface with the ordered closed micro-nano composite structure characteristics, so as to verify the effectiveness of the product and the method provided by the invention.

And S5, referring to the graph in FIG. 8 and FIG. 9, the performance test of the sample mainly comprises the following steps: surface contact angle measurement; and (5) testing the anti-icing performance.

i. The contact angle measurement is mainly used for judging the hydrophobicity degree of the sample, and the contact angle of the sample prepared by the method can reach 169 degrees, namely the sample is a super-hydrophobic surface.

The anti-icing performance test mainly comprises water drop icing and water vapor condensation frosting, and specifically comprises the following steps: testing the icing time of the water drops on different surfaces in a low-temperature environment, and recording the icing process of the water drops; and combining the process of water vapor condensation and frosting, measuring the frosting quality of the surface of the sample at different times, and carrying out comparative analysis on the anti-frosting performance of the surface.

Tangential adhesion of the ice layer to the sample surface and normal adhesion test, i.e. the ease of ice block peeling.

And S6, combining the performance test results, repeating the steps (1) to (4) until micro-nano composite structures with different performance requirements are obtained.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrases "comprising … …" or "comprising … …" does not exclude the presence of additional elements in a process, method, article, or terminal that comprises the element. Further, herein, "greater than," "less than," "more than," and the like are understood to exclude the present numbers; the terms "above", "below", "within" and the like are to be understood as including the number.

Although the embodiments have been described, once the basic inventive concept is obtained, other variations and modifications of these embodiments can be made by those skilled in the art, so that the above embodiments are only examples of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures or equivalent processes using the contents of the present specification and drawings, or any other related technical fields, which are directly or indirectly applied thereto, are included in the scope of the present invention.