A subtractive etching micro-nano multi-stage rough structure copper surface for enhancing boiling heat transfer

Abstract

A kind of subtractive etching micro-nano multi-stage rough structure copper surface for strengthening boiling heat transfer, it is related to micro-nano composite structure strengthening phase change heat transfer field.The etching micro-nano multi-stage rough structure is completely covered on the surface of copper substrate, and the micro-nano multi-stage rough structure includes micron-level cavity, nanometer-level cavity / hole and nanometer-level granular protrusion.Nanometer granular protrusion is distributed on the bottom or sidewall of micron cavity, part of the cavity is nested with secondary micron / nanometer cavity, nanometer granular protrusion can be connected into sheet structure, and finally form multi-stage staggered rough surface;The structure provides stable bubble nucleation site by micron cavity, reduces nucleation superheat, stores gas by nanometer hole and forms capillary network to accelerate working medium supplement, and nanometer granular protrusion enhances local capillary force, which significantly strengthens boiling heat transfer performance.And it shows good stability in boiling test, and is suitable for high-power electronic heat dissipation and energy field phase change heat transfer equipment.

Description

Technical Field

[0001] This utility model relates to the field of enhanced phase change heat transfer technology, specifically to a subtractive etched micro / nano multi-level rough structure for enhancing boiling heat transfer. Background Technology

[0002] With the rapid development of micro / nano manufacturing technology and the increasing precision of equipment and devices used in the microelectronics field, the demand for efficient thermal management systems to solve heat dissipation problems in limited integrated spaces is growing. Surface micro / nano structuring has become an important research direction for improving boiling heat transfer performance. Micro / nano structures can significantly enhance boiling heat transfer. By increasing surface roughness, more nucleation sites can be provided, promoting bubble formation and increasing the heat transfer area. Furthermore, altering surface wettability can accelerate the replenishment of the liquid working fluid, thereby enhancing heat transfer.

[0003] Studies have shown that micron-scale structures, such as micropillar arrays, microporous structures, and microgrooves, can increase the effective heat transfer area by 2-3 orders of magnitude through geometric morphology design, directly enhancing the heat transport capacity per unit area. The capillary pumping effect of the microstructure surface topology can improve liquid wettability, forming a continuous gas-liquid two-phase cycle, and the structure-induced uniform heat flux distribution can effectively suppress local overheating. Of particular note is the good matching between micron-scale structural parameters and bubble nucleation characteristic scales (typically 1-100 μm). By controlling the surface morphology, the nucleation site density can be increased by 2-3 orders of magnitude, thereby significantly improving the boiling heat transfer coefficient. At the nanoscale, structures such as nanopillar arrays, porous nanocoatings, and sintered surfaces of micro- and nanoparticles exhibit unique heat transfer enhancement mechanisms. The high specific surface area characteristics increase surface roughness by 1-2 orders of magnitude, reducing nucleation overheating to 1 / 3-1 / 5 of that of traditional surfaces. Studies on the synergistic effect between micro and nanostructures show that nanopillar arrays can reduce adhesion by 45-60% by limiting the contact line length of the bubble substrate, resulting in a 30-50% reduction in bubble detachment time. For nanoporous structures, the strong capillary forces generated by their submicron-level pores synergize with the macroscopic boiling process, achieving a dynamic equilibrium in the phase transition process while maintaining high evaporation flux. However, the fabrication processes of micro and nano hierarchical structures are often complex and costly. Therefore, optimizing the fabrication methods of micro and nano structures is of great significance for developing high-performance heat transfer surfaces and promoting their industrial applications.

[0004] Common methods for fabricating micro / nano structures include electrodeposition, etching, sintering, and laser processing. However, techniques such as electrodeposition and sintering are limited in industrial-scale application due to their complex processes and stringent equipment requirements. In contrast, green chemical etching technology exhibits unique advantages in the field of functionalized surface fabrication due to its strong process compatibility, low operating costs, and minimal environmental impact. Most existing nanostructure fabrication technologies are based on additive manufacturing principles, which involve stacking nanoscale features onto a substrate through epitaxial growth or physical deposition. However, structures formed through additive manufacturing often suffer from inherent defects such as insufficient bonding strength. In practical applications, the micro / nano structures on the surface may be at risk of peeling or aging. Chemical etching technology, based on subtractive manufacturing principles, has significant advantages in structural reliability. By controllably removing the substrate material, micro / nano hierarchical structures can be directly constructed, effectively avoiding the risk of structure detachment. Therefore, etching can be used to fabricate simple, low-cost, and highly stable micro / nano hierarchical structure surfaces. Utility Model Content

[0005] The purpose of this invention is to propose a subtractive etching micro / nano-level roughened copper surface structure for enhancing boiling heat transfer and its preparation method. The proposed structure is a micro / nano-level structure composed of micron-scale cavities, nano-scale cavities / pores, and nano-scale granular protrusions. This structure can significantly improve the boiling performance of the copper surface by increasing the heat transfer area, enhancing capillary wicking, and providing more bubble nucleation sites, thereby achieving the goal of enhancing boiling heat transfer. Furthermore, the preparation method of this structure does not rely on expensive specialized large-scale equipment or harsh experimental environments, enabling simple, convenient, low-cost, and rapid preparation of stable micro / nano-level structures. This method has many significant advantages, such as high efficiency, strong scalability, and the ability to achieve large-scale preparation, showing broad prospects for industrial applications. This subtractive etching micro / nano-level roughened copper surface structure and its preparation method have extremely high applicability and practical value in heat dissipation applications such as enhancing boiling heat transfer.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A subtractive etching micro / nano-level rough structure copper surface for enhancing boiling heat transfer, wherein the etched micro / nano-level rough structure completely covers the surface of the copper substrate, and the micro / nano-level rough structure includes micron-level cavities, nano-level cavities / holes, and nano-level granular protrusions, which together constitute a multi-level structure.

[0008] There are nanoscale granular protrusions with uniform particle size distribution at the bottom and / or sidewalls of some micron-sized cavities; there are nanoscale cavities / holes at the bottom of some micron-sized cavities, and there are also independent nanoscale cavities / holes on the surface of the copper substrate; there are also independent micron-sized cavities on the surface of the copper substrate.

[0009] At the bottom of a relatively large micrometer-sized cavity, there is also a relatively small micrometer-sized cavity.

[0010] Multiple nanoscale particle-like protrusions are connected to form a sheet-like structure;

[0011] The micron-scale concave cavity has a lateral (parallel copper surface dimension) of 1µm-15µm and a depth of 500nm-15µm; the nano-scale concave cavity / hole has a dimension (parallel copper surface dimension) of 150nm-800nm ​​and a depth of 50nm-600nm; and the nano-scale granular protrusion structure (diameter dimension) has a dimension of 40nm-200nm. The micro-nano multi-level structure composed of these three structures provides multi-level features for surface functionality.

[0012] The final result is a multi-scale rough structure consisting of micron-scale cavities, nano-scale cavities / holes, nano-scale granular protrusions, and micron-scale blocky / sheet-like structures interwoven on the unetched copper substrate surface.

[0013] A method for preparing a subtractive etching micro / nano-level roughened copper surface for enhancing boiling heat transfer includes the following steps:

[0014] Step A: Ultrasonic cleaning of the copper substrate using a cleaning solution;

[0015] Step B: Using a mixed aqueous solution of ammonium persulfate and chloride as the etching solution, the cleaned copper substrate is placed in the etching solution for etching. After etching, the substrate is cleaned to obtain a subtractive etched micro / nano-level roughened structure surface. In the mixed aqueous solution of ammonium persulfate and chloride, ammonium persulfate and chloride are used as solutes. Preferably, the chloride is sodium chloride or potassium chloride, and the mass ratio of solute to water is 1:3. The mass ratio of ammonium persulfate to chloride in the solute is 1:9-3:7, and the temperature of the etching solution is 15-35℃.

[0016] Preferably, in step B of the above preparation method, the copper substrate is placed in the etching solution for etching for 10 min or 15 min.

[0017] Preferably, in step B of the above preparation method, the cleaning process after etching is performed by using ethanol to ultrasonically clean the target metal substrate with low power in order to remove residual etching solution in the micro-nano hierarchical structure generated by etching.

[0018] A copper surface with a subtractive etching micro / nano-level rough structure for enhancing boiling heat transfer was prepared according to the above method. The multi-level rough structure includes micron-level cavities, nano-level cavities / holes, and nano-level granular protrusions.

[0019] The subtractive etching micro / nano multi-level roughened structure for enhanced boiling heat transfer prepared according to the above method is applied in the field of evaporation / boiling phase change heat transfer technology.

[0020] The beneficial effects of this utility model are as follows:

[0021] 1. The proposed etched micro / nano-level roughened copper surface combines microstructure and nanostructure, with the synergistic effect of these structures enhancing boiling heat transfer performance. Its multi-level roughened structure includes micron-level cavities, nano-level cavities / pores, and nano-level granular protrusions. The micron-level cavities serve as ideal stable bubble nucleation sites, effectively trapping gas or vapor and reducing the superheat required for bubble nucleation, making it easier for bubbles to form at lower wall superheats. The nano-level cavities / pores can store some gas, providing timely bubble nucleation sites, and the gaps between the micron-level and nano-level cavities / pores form a complex, interconnected capillary network. The nano-level granular protrusions, located at the bottom and walls of the micron-level cavities, further enhance local capillary forces and improve liquid replenishment capacity. Thus, the synergistic effect of these three structures significantly enhances the boiling heat transfer performance of the copper surface.

[0022] 2. The method for preparing a subtractive etching micro / nano-level roughened copper surface proposed in this invention is simple and quick, requiring no expensive specialized equipment or harsh experimental environment. Compared to additive manufacturing, subtractive manufacturing can achieve higher processing precision and surface quality, and is more stable. This invention uses chemical wet etching to fabricate micro / nano-level structures using anisotropic etching, which is a low-cost and convenient method. A stable micro / nano-level structure surface can be obtained by directly immersing the copper substrate in the etching solution for 1-15 minutes. It boasts high production efficiency and exhibits excellent stability in boiling tests, making it suitable for large-scale industrial applications.

[0023] 3. For processing copper substrate surfaces, this invention proposes a simple, easy-to-implement, and environmentally friendly etching solution formulation: a mixed aqueous solution of ammonium persulfate and sodium chloride. While maintaining a constant solute-to-water mass ratio of 1:3, different etching effects can be achieved by controlling the mass ratio of ammonium persulfate to sodium chloride. When the mass ratio is between 1:9 and 3:7, a distinct micro-nano level rough structure can be etched onto the copper substrate, exhibiting advantages such as high etching rate and low corrosivity to other materials. Simultaneously, during the etching process, the bubbles and gas films generated by the decomposition of ammonium persulfate, and the other oxides generated by the oxidation reaction, can intensify the anisotropic etching of the copper substrate surface, increase the surface roughness, further increase the bubble nucleation sites on the copper substrate surface, and enhance boiling performance.

[0024] 4. The copper etching solution proposed in this invention is used to process the surface of a copper substrate. Ammonium persulfate acts as the core oxidant in the solution, decomposing through a free radical chain reaction to generate sulfate free radicals, which then react with the copper surface to oxidize it, resulting in etching. In this reaction system, Cl- reacts with the generated Cu... 2+ The formation of a stable [CuCl4]2- complex effectively prevents the formation of passivation layers such as CuO or Cu(OH)2 on the copper surface, ensuring continuous activation of the reaction interface. On the other hand, Cl- acts as a catalyst, accelerating the etching of copper by ammonium persulfate through an intermediate transition state. However, during the reaction, ammonium persulfate etches the Cu surface along grain boundaries, leading to selective corrosion. At copper grain boundaries, due to the loose atomic arrangement or impurity segregation, the grain boundaries may be preferentially etched, resulting in the removal of material at the grain boundaries. Furthermore, since copper has a face-centered cubic (FCC) crystal structure, the etching rate of different crystal faces may vary. Due to differences in crystal orientation and size among the grains in the copper substrate, specific compositions and ratios of etching solutions will produce different corrosion rates for different crystal faces, resulting in inconsistent corrosion rates in different areas of the copper substrate surface during etching, thus forming a micro / nano-level rough structure. During the etching process, Cu... 2+ When the concentration in a localized area is too high, it fails to form a stable [CuCl4]2- complex with Cl- in time, resulting in Cu... 2+ It will catalyze the reaction to oxidize Cu to Cu + Furthermore, the local concentration of sulfate free radicals is relatively low, which can also oxidize Cu to Cu. + Cu + It is very unstable and can be easily reduced to elemental copper, which precipitates out in the form of nanoparticles and adheres to the copper wall to form nanoscale protrusions, thereby further generating micro-nano multi-level structures on the surface of the copper substrate.

[0025] 5. The nano-level structure, through the synergistic effect of micro and nano structures, can significantly increase the heat flux density (CHF) and heat transfer coefficient (HTC) of the copper substrate surface. Furthermore, different mass ratios of ammonium persulfate to sodium chloride in the etching solution produce varying degrees of enhancement to boiling performance. Experimental tests show that when the mass ratio of ammonium persulfate to sodium chloride in the etching solution is 3:7, the maximum CHF reaches 223.97 W / cm². -2 When the mass ratio of ammonium persulfate to sodium chloride in the etching solution is 1:9, the maximum HTC is reached at 20.8 W / cm². -2 K -1 Compared to a copper plane, the efficiency was increased by 125.5% and 524.6% respectively, demonstrating a significant boiling heat transfer enhancement effect.

[0026] In summary, the method for preparing subtractive etching micro / nano-level rough structures proposed in this invention has advantages such as strong stability, simplicity, low cost, strong scalability, and the ability to be mass-produced and engineered, and has a very broad application prospect. Attached Figure Description

[0027] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0028] Figure 1 This is a schematic cross-sectional view of a copper surface with a subtractive etching micro / nano-level roughened structure used to enhance boiling heat transfer.

[0029] Figure 2 This is a schematic diagram of the front structure of a copper surface with a subtractive etching micro / nano-level roughened structure used to enhance boiling heat transfer.

[0030] 101 is a copper substrate, 102 is a micron-sized cavity, 103 is a nano-sized cavity / pore, and 104 is a nano-sized granular protrusion.

[0031] Figure 3 This is an optical photograph of the micro / nano-level rough structure sample prepared in Example 1 of this utility model.

[0032] Figure 4 This is a SEM image of the micro / nano-level rough structure sample prepared in Example 1 of this utility model.

[0033] Figure 5 The figure shows a comparison of the boiling heat transfer performance of two different boiling surfaces, namely the micro-nano multi-level rough structure surface-A and the smooth copper plane, under normal pressure with deionized water as the working fluid in Embodiment 1 of this utility model. (a) is the boiling curve and (b) is the heat transfer coefficient curve.

[0034] Figure 6 This is an optical photograph of the micro / nano-level rough structure sample prepared in Example 2 of this utility model.

[0035] Figure 7 This is an SEM image of the micro / nano-level rough structure sample prepared in Example 2 of this utility model.

[0036] Figure 8 The graph shows a comparison of the boiling heat transfer performance of three different boiling surfaces—the micro-nano multi-level rough structure surface-B in Embodiment 2, the micro-nano multi-level rough structure surface-A in Embodiment 1, and the smooth copper plane—under normal pressure using deionized water as the working fluid. (a) is the boiling curve, and (b) is the heat transfer coefficient curve.

[0037] Figure 9 A comparison of the heat transfer coefficients of the micro / nano-level rough structure surface-B in Embodiment 2 of this utility model with other surfaces.

[0038] Figure 10 This is an optical photograph of the micro / nano-level rough structure sample prepared in Example 3 of this utility model.

[0039] Figure 11 The graph shows a comparison of the heat transfer performance of the micro-nano multi-level rough structure surface-C in Embodiment 3 of this utility model under normal pressure after three consecutive saturated pool boiling tests using deionized water as the working fluid. (a) is the boiling curve, and (b) is the heat transfer coefficient curve. Detailed Implementation

[0040] To more clearly illustrate this utility model, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the present invention. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of this utility model.

[0041] A subtractive etching technique for enhancing boiling heat transfer to create micro / nano-level roughened copper surfaces, see [link / reference]. Figure 1 and Figure 2 The etched micro / nano-level roughening structure completely covers the surface of the copper substrate. The micro / nano-level roughening structure includes micron-level cavities, nano-level cavities / holes, and nano-level granular protrusions, forming a composite structure. Uniformly distributed nano-level granular protrusions exist at the bottom and / or sidewalls of some micron-level cavities; nano-level cavities / holes exist at the bottom of some micron-level cavities; independent nano-level cavities / holes also exist on the surface of the copper substrate; and independent micron-level cavities also exist on the surface of the copper substrate.

[0042] Multiple nanoscale particle-like protrusions are connected to form a sheet-like structure;

[0043] The micron-scale concave cavity has a lateral (parallel copper surface size) of 1µm-15µm and a depth of 500nm-15µm; the nano-scale concave cavity / hole has a size (parallel copper surface size) of 150nm-800nm ​​and a depth of 50nm-600nm; and the nano-scale granular protrusion structure (diameter structure size) has a size of 40nm-200nm. The micro-nano multi-level structure composed of these three structures provides multi-level features for surface functionality.

[0044] Some relatively large micron-sized cavities also have relatively small micron-sized cavities at their bottom.

[0045] The final result is a multi-scale rough structure consisting of micron-scale cavities, nano-scale cavities / holes, nano-scale granular protrusions, and micron-scale blocky / sheet-like structures interwoven on the unetched copper substrate surface.

[0046] Example 1

[0047] Preferably, the mass ratio of ammonium persulfate, sodium chloride, and water in the etching solution is controlled to be 3:7:30, and etching is performed for 10 minutes to prepare a subtractive etched micro / nano-level rough structure on a copper substrate, comprising the following steps:

[0048] Step A: Use a cleaning solution to ultrasonically clean a round copper sheet with a diameter of 10mm and a thickness of 1mm.

[0049] Step B: Prepare an etching solution by mixing ammonium persulfate, sodium chloride, and water in a mass ratio of 3:7:30. Immerse the target metal substrate in the etching solution and etch for 10 minutes. After etching, ultrasonically clean the substrate with ethanol at 40% power to obtain a subtractive etched micro / nano-level rough structure surface.

[0050] Figure 4 This is a SEM image of the micro / nano-level rough structure surface etched using this method. Figure 4 It can be clearly seen that the micro-nano multi-level rough structure surface etched by this method is a rough structure consisting of interspersed protruding block / sheet structures and micron-level and nano-level cavities / holes, and also contains a large number of nano-level particle protrusions. Figure 4 In (a), it can be clearly seen that the sample surface contains a large number of micron-sized cavities and nano-sized granular protrusions. The size of the cavities is approximately 6-10 μm, while the nano-sized cavities / pores are fewer, with a size of 500 nm-800 nm. Figure 4 In (b) and (c), nanoscale protrusions with a size of 100nm-200nm can be clearly seen. These protrusions can increase the replenishment of liquid through capillary action, thereby enhancing the boiling effect.

[0051] The surface of the subtractive etched micro / nano-level roughened structure was subjected to saturated pool boiling heat transfer tests under normal pressure using deionized water as the working fluid, with a smooth copper plane used as a reference sample. Figure 5 This is a comparison chart of the boiling performance of saturated tanks. Figure 5 (a) is the boiling curve. Figure 5 (b) shows the heat transfer coefficient curve. Figure 5 It can be seen that, at this mass ratio, the boiling performance of the subtractive etched micro / nano-level roughened structure surface obtained by etching is significantly better than that of ordinary copper plane, with its CHF reaching a maximum of 223.98 W·cm⁻¹. -2 HTC has a power rating of 13.98W·cm. -2· K -1 Compared with the copper plane, CHF increased by 125.5% and HTC increased by 330.1%, which shows that the structure greatly improves the heat transfer performance of the copper surface.

[0052] Example 2

[0053] Preferably, the mass ratio of ammonium persulfate, sodium chloride, and water in the etching solution is controlled at 1:9:30, and etching is performed for 10 minutes to prepare a subtractive etching micro / nano-level roughened structure on a copper substrate, comprising the following steps:

[0054] Step A: Use a cleaning solution to ultrasonically clean a round copper sheet with a diameter of 10mm and a thickness of 1mm.

[0055] Step B: Prepare an etching solution by mixing ammonium persulfate, sodium chloride, and water in a mass ratio of 1:9:30. Immerse the target metal substrate in the etching solution for 10 minutes. After etching, clean the substrate to obtain a subtractive etched micro / nano-level roughened structure surface.

[0056] Figure 7 This is a SEM image of the micro / nano-level rough structure surface etched using this method. Figure 7 In (a), cavities with diameters between 1-8 μm are clearly visible, as well as some nanoscale cavities / pores and nanoscale granular protrusions. Figure 7 In (b), cavities / pores with diameters ranging from 200 nm to 600 nm can be clearly seen. The reason for the low heat transfer coefficient of this sample is the large number of nanoscale cavities / pores distributed on its surface, which is conducive to the retention of residual gas and promotes bubble nucleation.

[0057] The surface of the subtractive etched micro / nano-level rough structure was subjected to saturated pool boiling heat transfer testing under normal pressure using deionized water as the working fluid. A smooth copper plane and the micro / nano-level rough structure surface-A in Example 1 were used as reference samples. Figure 8 This is a comparison chart of the boiling performance of saturated tanks. Figure 8 (a) is the boiling curve. Figure 8 In diagram (b), the heat transfer coefficient curve is shown. Figure 8 It can be seen that, at this mass ratio, the boiling performance of the subtractive etched micro / nano-level roughened structure surface is significantly better than that of ordinary copper plane, with the highest CHF of this sample reaching 183.84 W·cm⁻¹. -2 HTC reaches 20.8W·cm -2· K -1 Compared to copper planes, the heat transfer coefficient (CHF) increased by 85.1% and the heat transfer temperature (HTC) increased by 524.6%, showing a significant improvement in HTC and very low wall superheat. Furthermore, compared to high-performance surfaces in existing literature, the heat transfer coefficient of etched micro / nano-level roughened structures is at the highest level. Figure 9 The image shows a comparison of the heat transfer coefficients of the sample surface with those of nanowire array surfaces (Nano Energy, 2017, 38:59-65), microgroove array surfaces (Renewable Energy, 2022, 187:790-800), microporous surfaces (Applied Thermal Engineering, 2020, 165:114396), GNP / Cu-Al2O3 coated surfaces (Thermal Science and Engineering Progress, 2023, 43:101965), and laser-textured deposited surfaces (Applied Surface Science, 2024, 661:160015). It is evident that the micro / nano-level roughened structure etched under these conditions significantly improves the boiling performance of the sample and has broad application prospects.

[0058] Example 3

[0059] The subtractive etching micro / nano-level roughened structures on copper substrates were prepared by controlling the mass ratio of ammonium persulfate, sodium chloride, and water in the etching solution to 3:7:30 and etching for 15 minutes. The process included the following steps:

[0060] Step A: Use a cleaning solution to ultrasonically clean a round copper sheet with a diameter of 10mm and a thickness of 1mm.

[0061] Step B: Prepare an etching solution by mixing ammonium persulfate, sodium chloride, and water in a mass ratio of 3:7:30. Immerse the target metal substrate in the etching solution and etch for 15 minutes. After etching, ultrasonically clean the substrate with ethanol at 40% power to obtain a subtractive etched micro / nano-level rough structure surface.

[0062] Boiling heat transfer stability tests were conducted on the surface of the subtractive etched micro / nano multi-level rough structure under normal pressure using deionized water as the working fluid. The maximum test heat flux was set to 80% of CHF to prevent temperature spikes at the critical heat flux density, which could burn out the sample and the testing equipment and affect the judgment of the sample's boiling stability. Figure 11 This is a comparison chart of the boiling performance of saturated tanks. Figure 11 (a) is the boiling curve. Figure 11 In diagram (b), the heat transfer coefficient curve is shown. Figure 11 It can be seen that the heat flow curves and heat transfer coefficient curves during the three boiling processes are basically consistent, with the first boiling process showing slightly higher performance. This may be due to the system's thermal inertia and preheating issues. Overall, the sample exhibits good stability and can be used in engineering for extended periods, demonstrating broad application prospects.

[0063] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of this utility model are still within the protection scope of this utility model.

Claims

1. A method for enhancing boiling heat transfer through subtractive etching of micro / nano-level roughened copper surfaces, characterized in that, The etched micro / nano-level roughness structure completely covers the surface of the copper substrate. The micro / nano-level roughness structure includes micron-level cavities, nano-level cavities / holes, and nano-level granular protrusions, which together constitute a multi-level structure.

2. The subtractive etching micro / nano-level roughened copper surface for enhancing boiling heat transfer according to claim 1, characterized in that, There are nanoscale granular protrusions with uniform particle size distribution at the bottom and / or sidewalls of some micron-sized cavities; Nanoscale cavities / holes exist at the bottom of some micron-sized cavities, and independent nanoscale cavities / holes also exist on the surface of the copper substrate; independent micron-sized cavities also exist on the surface of the copper substrate.

3. A subtractive etching micro / nano-level roughened copper surface for enhancing boiling heat transfer according to claim 1, characterized in that, Multiple nanoscale particle-like protrusions are connected to form a sheet-like structure.

4. A subtractive etching micro / nano-level roughened copper surface for enhancing boiling heat transfer according to claim 1, characterized in that, The micron-scale concave parallel copper surface has a lateral dimension of 1 μm-15 μm and a depth of 500 nm-15 μm, the nano-scale concave / pore parallel copper surface has a dimension of 150 nm-800 nm and a depth of 50 nm-600 nm, and the nano-scale granular protrusion structure has a diameter of 40 nm-200 nm. The micro-nano multi-level structure composed of these three structures provides multi-level features for surface functionality.

5. A subtractive etching micro / nano-level roughened copper surface for enhancing boiling heat transfer according to claim 4, characterized in that, At the bottom of a relatively large micrometer-sized cavity, there is also a relatively small micrometer-sized cavity.

6. A subtractive etching micro / nano-level roughened copper surface for enhancing boiling heat transfer according to claim 1, characterized in that, The final result is a multi-scale rough structure consisting of micron-scale cavities, nano-scale cavities / holes, nano-scale granular protrusions, and micron-scale blocky / sheet-like structures interwoven on the unetched copper substrate surface.

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