Reduced material etching micro-nano multistage rough structure copper surface for enhancing boiling heat transfer and preparation method of reduced material etching micro-nano multistage rough structure copper surface

Abstract

The invention discloses a subtractive etching micro-nano multistage rough structure copper surface for strengthening boiling heat transfer and a preparation method thereof, and relates to the technical field of micro-nano composite structure strengthening phase change heat transfer. The etched micro-nano multistage coarse structure completely covers the surface of the copper substrate, the micro-nano multistage coarse structure comprises micron-scale concave cavities, nano-scale concave cavities / holes and nano-scale granular bulges, and the micron-scale concave cavities, the nano-scale concave cavities / holes and the nano-scale granular bulges jointly form a multistage structure; performing ultrasonic cleaning on the target metal substrate by using a cleaning solution; and a mixed aqueous solution of ammonium persulfate and chlorate is used as an etching solution, and the cleaned target metal substrate is left to stand in the etching solution for etching. And after the etching is finished, cleaning to obtain the etched micro-nano composite rough structure surface. Ammonium persulfate and chlorate are used as solutes, and the mass ratio of the solutes to the solvent is 1: 3. The mass ratio of the ammonium persulfate to the chlorate in the solute is (1: 9)-(3: 7). The method has high production efficiency, shows good thermal stability in a boiling test, and is beneficial to industrial large-scale application and production.

Description

Technical Field

[0001] The present invention relates to the technical field of enhanced phase change heat transfer, and in particular to a method for preparing a subtractive etching micro-nano multi-level rough structure for enhancing boiling heat transfer. Background Art

[0002] With the rapid development of micro-nano manufacturing technology and the increasing sophistication of equipment and devices used in the microelectronics field, there is an increasing demand for efficient thermal management systems to solve heat dissipation problems in limited integrated spaces. Surface micro-nanostructuring has become an important research direction for improving boiling heat transfer performance. Micro-nanostructuring can greatly enhance boiling heat transfer. Micro-nanostructuring can increase surface roughness, provide more nucleation sites, promote bubble formation, increase heat transfer area, change surface wettability, and accelerate the replenishment of liquid working fluids to achieve the purpose of enhancing heat transfer.

[0003] Research has shown that micron-scale structures such as micropillar arrays, micropore 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 microstructured surface topology can improve liquid wettability, forming a continuous gas-liquid two-phase circulation, and the structure-induced uniform distribution of heat flux can effectively suppress local overheating. Of particular note is that the micron-scale structural parameters are well matched to the characteristic scale of bubble nucleation (usually 1-100μm). By regulating the surface morphology, the density of nucleation sites can be increased by 2-3 orders of magnitude, thereby significantly improving the boiling heat transfer coefficient. At the nanoscale level, structures such as nanopillar arrays, porous nanocoatings, and micro-nanoparticle sintered surfaces exhibit unique heat transfer enhancement mechanisms. The high specific surface area characteristics increase the surface roughness by 1-2 orders of magnitude, and the nucleation superheat can be reduced to 1 / 3-1 / 5 of that of traditional surfaces. Research on micro-nano synergistic effects has shown that nanopillar arrays can reduce adhesion by 45-60% by limiting the length of the bubble-substrate contact line, resulting in a 30-50% reduction in bubble detachment time. In nanoporous structures, the strong capillary forces generated by their submicron pores synergize with the macroscopic boiling process, achieving a dynamic balance in the phase change process while maintaining a high evaporation flux. However, the fabrication process for micro-nano hierarchical structures is often complex and costly. Therefore, optimizing the fabrication methods for micro-nano structures is of great significance for developing high-performance heat transfer surfaces and promoting their industrial application.

[0004] Common methods for fabricating micro- and nanostructures include electrodeposition, etching, sintering, and laser processing. However, these techniques, such as electrodeposition and sintering, are limited in their industrial-scale application due to their complex processes and stringent equipment requirements. In contrast, green chemical etching offers unique advantages in the field of functionalized surface fabrication due to its strong process compatibility, low operating costs, and minimal environmental impact. Existing nanostructure fabrication techniques are mostly based on additive manufacturing principles, where nanoscale features are superimposed on a substrate through epitaxial growth or physical deposition. However, structures formed by additive manufacturing often suffer from inherent weaknesses such as insufficient bonding strength. In practical applications, surface micro- and nanostructures may be at risk of flaking or aging. Chemical etching, based on subtractive manufacturing principles, offers significant advantages in structural reliability. By controlling the removal of the substrate material, micro- and nanoscale hierarchical structures can be directly constructed, effectively avoiding the risk of structural detachment. Therefore, etching methods can create simple, low-cost, and highly stable micro- and nanoscale hierarchical surfaces. Summary of the Invention

[0005] The purpose of the present invention is to propose a subtractive etched micro-nano multi-level rough structure copper surface for enhancing boiling heat transfer and a preparation method thereof. The structure proposed in the present invention is a micro-nano multi-level structure composed of micron-scale cavities, nano-scale cavities / holes and nano-scale granular protrusions. This structure can greatly improve the boiling performance of the copper surface by increasing the heat transfer area, improving capillary wicking, and providing more bubble nucleation sites, thereby achieving the purpose of enhancing boiling heat transfer. In addition, the preparation method of this structure does not require expensive professional large-scale equipment and a harsh experimental environment, and can achieve a simple, convenient, low-cost and rapid preparation of a stable micro-nano multi-level structure. This method has many significant advantages, such as high work efficiency and strong scalability. It can also achieve large-scale preparation and has broad prospects for industrial application. The subtractive etched micro-nano multi-level rough structure copper surface and its preparation method have extremely high applicability and practical value in heat dissipation applications such as enhancing boiling heat transfer.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

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

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

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

[0010] Multiple nano-scale granular protrusions are connected into a sheet-like structure;

[0011] The lateral size of the micron-scale cavity (size parallel to the copper surface) is 1um-15μm, and the depth is 500nm-15μm. The size of the nanoscale cavity / hole (size parallel to the copper surface) is 150nm-800nm, and the depth is 50nm-600nm. The size of the nanoscale granular protrusion structure (diameter structure size) is 40nm-200nm. The micro-nano multi-level structure composed of the three structures provides multi-level characteristics for surface functionality.

[0012] The final result is a cross-scale multi-level rough structure in which micron-scale cavities, nano-scale cavities / holes, nano-scale granular protrusions, and micron-scale block / sheet structures formed on the surface of the unetched copper substrate are intertwined.

[0013] A method for preparing a copper surface with a micro-nano multi-level rough structure by subtractive etching for enhancing boiling heat transfer comprises the following steps:

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

[0015] Step B: Using a mixed aqueous solution of ammonium persulfate and chloride as an etching solution, the cleaned copper substrate is placed in the etching solution for etching. After the etching is completed, the subtractive etching micro-nano multi-level rough structure surface prepared by cleaning is obtained. The mixed aqueous solution of ammonium persulfate and chloride, wherein ammonium persulfate and chloride are 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°C.

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

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

[0018] A subtractive-etched micro-nano multi-level rough structure copper surface for enhancing boiling heat transfer is prepared according to the above method, wherein the multi-level rough structure includes micron-scale cavities, nanoscale cavities / holes, and nanoscale granular protrusions.

[0019] The application of a subtractive etched micro-nano multi-level rough structure for enhancing boiling heat transfer prepared according to the above method is used in the field of evaporation / boiling phase change heat transfer technology.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The etched micro-nano multi-level rough structure copper surface proposed in the present invention combines microstructures with nanostructures, and the micro-nanostructures work synergistically to improve the performance of boiling heat transfer. Its multi-level rough structure includes micron-scale cavities, nanoscale cavities / holes, and nanoscale granular protrusions. The micron-scale cavities in the structure are ideal stable bubble nucleation points. The cavities can effectively retain gas or vapor, reduce the superheat required for bubble nucleation, and make bubbles more likely to be generated at lower wall superheat. The nanoscale cavities / holes can store a portion of the gas, providing bubble nucleation sites in a timely manner, and the gaps between the micron-scale cavities and nanoscale cavities / holes form a complex, interconnected capillary network. The nanoscale granular protrusions are located at the bottom and wall of the micron-scale cavities, which can further enhance the local capillary force and improve the liquid replenishment capacity. As a result, the boiling heat transfer performance of the copper surface is greatly enhanced under the synergistic effect of the three structures.

[0022] 2. The method for preparing a copper surface with a subtractive etching micro-nano multi-level rough structure proposed in the present invention is simple and quick, and does not require expensive professional equipment and a harsh experimental environment. Compared with additive manufacturing, subtractive manufacturing can achieve higher processing accuracy and surface quality, and is more stable. The present invention adopts chemical wet etching to utilize anisotropic etching to manufacture micro-nano multi-level structures, which is a low-cost and convenient method. A stable micro-nano multi-level structure surface can be obtained by directly placing the copper substrate in the etching solution for etching for 1min-15min. It has high production efficiency and shows good stability in boiling tests, which is conducive to large-scale industrial application.

[0023] 3. For the processing of the copper substrate surface, the present invention proposes a simple, easy-to-implement and environmentally friendly etching solution formula, namely, a mixed aqueous solution of ammonium persulfate and chloride salt. Wherein, under the condition of keeping the total mass of the solute and the mass ratio of water at 1:3 unchanged, different etching effects can be achieved by controlling the mass ratio of ammonium persulfate to sodium chloride. When the mass ratio of ammonium persulfate to sodium chloride is between 1:9-3:7, a micro-nano multi-level rough structure can be clearly etched on the copper substrate, and it has the advantages of high etching rate and low corrosiveness to other objects. At the same time, during the etching process in the etching solution, the bubbles and air film generated by the decomposition of ammonium persulfate and the other oxides generated by the oxidation reaction can intensify the anisotropic etching of the etching solution on the copper substrate surface, increase the roughness of the sample surface, further increase the bubble nucleation sites on the copper substrate surface, and enhance the boiling performance.

[0024] 4. Use the copper etching solution proposed in the invention to process the surface of the copper substrate. Ammonium persulfate acts as the core oxidant in the solution, decomposing through a free radical chain reaction to produce sulfate radicals, which react with the copper surface to cause the copper surface to be etched. In this reaction system, Cl- reacts with the generated Cu 2+ A stable [CuCl4]2- complex is formed. This complexation process effectively prevents the formation of passivation layers such as CuO or Cu(OH)2 on the copper surface, ensuring the continuous activation of the reaction interface. On the other hand, Cl- acts as a catalyst to accelerate the etching of copper by ammonium persulfate through an intermediate transition state. However, during the reaction, ammonium persulfate etches the Cu surface along the grain boundaries, which leads to selective corrosion during the etching process. At the grain boundaries of copper, due to the loose atomic arrangement or the presence of impurity segregation, the grain boundaries may be corroded preferentially, resulting in the removal of material at the grain boundaries. In addition, the crystal structure of copper is face-centered cubic (FCC), and the etching rates of different crystal planes may be different. Due to the differences in crystal orientation and size of the grains in the copper substrate, the etching solution with a specific composition and ratio will produce different corrosion rates for different crystal planes, resulting in inconsistent corrosion rates in different areas of the copper substrate surface during the etching process, thereby forming a micro-nano multi-level rough structure. During the etching process, Cu 2+ The concentration in the local area is too high, and it fails to form a stable [CuCl4]2- complex with Cl- in time. 2+ It catalyzes the oxidation of Cu to Cu + , and the local concentration of sulfate radicals is low, which will also oxidize Cu into Cu + , Cu + It is very unstable and can be easily reduced to elemental copper, precipitating in the form of nanoparticles and attaching to the copper wall to form nanoscale protruding particles, thereby further generating a micro-nano multi-level structure on the surface of the copper substrate.

[0025] 5. The nanoscale multi-level structure can significantly increase the heat flux (CHF) and heat transfer coefficient (HTC) of the copper substrate surface through the synergistic effect of micro-nanostructures. Different mass ratios of ammonium persulfate to chloride in the etching solution have different enhancement effects on 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 is 223.97 W cm -2 When the mass ratio of ammonium persulfate to sodium chloride in the etching solution is 1:9, the maximum HTC is 20.8 W cm -2 K -1 , which were increased by 125.5% and 524.6% respectively compared with the copper plane, showing a significant boiling heat transfer enhancement effect.

[0026] In summary, the method for preparing micro-nano multi-level rough structures by subtractive etching proposed in the present invention has the advantages of strong stability, simplicity, low cost, strong scalability, large-scale production and engineering application, and has a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 1 A schematic diagram of the cross-sectional structure of a copper surface with a subtractive micro-nano multi-level rough structure for enhancing boiling heat transfer;

[0029] Figure 2 A schematic diagram of the front structure of a subtractive-etched micro-nano multi-level roughened copper surface for enhancing boiling heat transfer.

[0030] 101 is the copper substrate, 102 is the micron-scale cavity, 103 is the nanometer-scale cavity / hole, and 104 is the nanometer-scale granular protrusion.

[0031] Figure 3 This is an optical photograph of the micro-nano multi-level rough structure sample prepared in Example 1 of the present invention.

[0032] Figure 4 This is a SEM photograph of the micro-nano multi-level rough structure sample prepared in Example 1 of the present invention.

[0033] Figure 5 This is a comparison chart of the saturated pool boiling heat transfer performance under normal pressure using deionized water as the working fluid for two different boiling surfaces, the micro-nano multi-level rough structure surface-A and the smooth copper plane in Example 1 of the present invention. (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 multi-level rough structure sample prepared in Example 2 of the present invention.

[0035] Figure 7 This is a SEM photograph of the micro-nano multi-level rough structure sample prepared in Example 2 of the present invention.

[0036] Figure 8 This is a comparison chart of the saturated pool boiling heat transfer performance under normal pressure with deionized water as the working fluid for three different boiling surfaces: the micro-nano multi-level rough structure surface-B in Example 2 of the present invention, the micro-nano multi-level rough structure surface-A in Example 1, and the smooth copper plane. (a) is the boiling curve and (b) is the heat transfer coefficient curve.

[0037] Figure 9 Comparison of heat transfer coefficients between the micro-nano multi-level rough structure surface-B and other surfaces in Example 2 of the present invention

[0038] Figure 10 This is an optical photograph of the micro-nano multi-level rough structure sample prepared in Example 3 of the present invention.

[0039] Figure 11 This is a comparison chart of the heat transfer performance of three consecutive saturated pool boilings under normal pressure using deionized water as the working fluid for the micro-nano multi-level rough structure surface-C in Example 3 of the present invention. (a) is the boiling curve and (b) is the heat transfer coefficient curve. DETAILED DESCRIPTION

[0040] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and drawings. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0041] A subtractive etching micro-nano multi-level rough structure copper surface for enhancing boiling heat transfer, see Figure 1 and Figure 2 The etched micro-nano multi-level rough structure completely covers the surface of the copper substrate. The micro-nano multi-level rough structure includes micron-scale cavities, nano-scale cavities / holes, and nano-scale granular protrusions, which together constitute a multi-level structure; nano-scale granular protrusion structures with uniform particle size distribution exist at the bottom and / or sidewall of some micron-scale cavities; nano-scale cavities / holes exist at the bottom of some micron-scale cavities, and independent nano-scale cavities / holes also exist on the surface of the copper substrate; independent micron-scale cavities also exist on the surface of the copper substrate;

[0042] Multiple nano-scale granular protrusions are connected into a sheet-like structure;

[0043] The micron-scale cavity has a lateral dimension (parallel to the copper surface) of 1um-15μm and a depth of 500nm-15μm. The nanoscale cavity / hole has a dimension (parallel to the copper surface) of 150nm-800nm ​​and a depth of 50nm-600nm. The nanoscale granular protrusion has a diameter 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 have relatively small micron-sized cavities at their bottoms.

[0045] The final result is a cross-scale multi-level rough structure in which micron-scale cavities, nano-scale cavities / holes, nano-scale granular protrusions, and micron-scale block / sheet structures formed on the surface of the unetched copper substrate are intertwined.

[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 etching micro-nano multi-level rough structure on a copper substrate, comprising the following steps:

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

[0049] Step B: Prepare an etching solution containing ammonium persulfate, sodium chloride, and water in a mass ratio of 3:7:30. Etch the target metal substrate in the etching solution for 10 minutes. After etching, ultrasonic cleaning with ethanol at 40% power is performed to produce a subtractive-etched micro-nano hierarchical roughened surface.

[0050] Figure 4 This is the SEM image of the surface of the micro-nano multi-level rough structure etched by 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 composed of raised block / sheet structures and micron-scale cavities and nanoscale cavities / holes interlaced with each other, and there are also a large number of nanoscale granular protrusions. Figure 4 In (a), it can be clearly seen that there are a large number of micron-scale cavities and nano-scale granular protrusions on the surface of the sample. The size of the cavities is about 6-10μm, while the nano-scale cavities / holes are relatively few and the size is between 500nm and 800nm. Figure 4 In (b) and (c), nanoscale protrusions with a size of 100nm-200nm can be clearly seen. These protrusions can increase fluid replenishment through capillary action to achieve the effect of enhancing boiling.

[0051] The saturated pool boiling heat transfer test was carried out on the subtractive etched micro-nano multi-level rough structure surface at normal pressure with deionized water as the working fluid, and a smooth copper plane was used as a reference sample. Figure 5 This is a comparison chart of saturated pool boiling performance. Figure 5 (a) is the boiling curve, Figure 5 (b) is 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 multi-level rough structure surface is significantly better than that of the ordinary copper plane, and its CHF reaches a maximum of 223.98 W·cm -2 , HTC is 13.98W·cm -2· K -1 Compared with the copper plane, CHF is increased by 125.5% and HTC is increased by 330.1%. This shows that this structure has greatly improved 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 to be 1:9:30, and etching is performed for 10 minutes to prepare a subtractive etching micro-nano multi-level rough structure on a copper substrate, comprising the following steps:

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

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

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

[0057] The subtractive etched micro-nano multi-level rough structure surface was subjected to saturated pool boiling heat transfer test under normal pressure with deionized water as the working medium, and a smooth copper plane and the micro-nano multi-level rough structure surface-A in Example 1 were used as reference samples. Figure 8 This is a comparison chart of saturated pool boiling performance. Figure 8 (a) is the boiling curve, Figure 8 (b) is the heat transfer coefficient curve, Figure 8 It can be seen that at this mass ratio, the boiling performance of the subtractive etched micro-nano multi-level rough structure surface is significantly better than that of the ordinary copper plane. The highest CHF of this sample is 183.84 W·cm -2 , HTC reached 20.8W·cm -2· K -1 Compared with the copper plane, CHF increased by 85.1% and HTC increased by 524.6%. It is obvious that the HTC of the sample has been greatly improved, and the wall overheating is very low. And compared with the high-performance surfaces in the existing literature, the heat transfer coefficient of the etched micro-nano multi-level rough structure surface is also at the highest level. Figure 9The following chart compares the heat transfer coefficients of this sample surface with those of a nanowire array surface (Nano Energy, 2017, 38:59-65), a microgroove array surface (Renewable Energy, 2022, 187:790-800), a microporous surface (Applied Thermal Engineering, 2020, 165:114396), a GNP / Cu-Al2O3 coating surface (Thermal Science and Engineering Progress, 2023, 43:101965), and a laser textured deposition surface (Applied Surface Science, 2024, 661:160015). This shows that the micro-nano multi-level roughness etched under these conditions significantly improves the boiling performance of the sample and has broad application prospects.

[0058] Example 3

[0059] 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 15 minutes to prepare a subtractive etching micro-nano multi-level rough structure on a copper substrate, including the following steps:

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

[0061] Step B: Prepare an etching solution containing ammonium persulfate, sodium chloride, and water in a mass ratio of 3:7:30. Etch the target metal substrate in the etching solution for 15 minutes. After etching, ultrasonic cleaning with ethanol at 40% power yields a subtractive-etched micro-nano hierarchical roughened surface.

[0062] The boiling heat transfer stability test of the subtractive etched micro-nano multi-level rough structure surface was carried out under normal pressure with deionized water as the working fluid. The maximum test heat flux was 80% of CHF to prevent the temperature from soaring when the critical heat flux density was reached, which would cause the sample and the test equipment to burn and affect the judgment of the boiling stability of the sample. Figure 11 This is a comparison chart of saturated pool boiling performance. Figure 11 (a) is the boiling curve, Figure 11 (b) is the heat transfer coefficient curve, 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 performance of the first boiling process being slightly higher, which may be due to the thermal inertia of the system and preheating issues. Overall, the sample has good stability and can be used in engineering for a long time, with broad application prospects.

[0063] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

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

2. A subtractive etching micro-nano multi-level rough structure copper surface for enhancing boiling heat transfer according to claim 1, characterized in that: On the bottom / sidewall of some micron-sized cavities, there are nano-scale granular protrusions with uniform particle size distribution; There are nanoscale cavities / holes at the bottom of some micron-scale cavities, and there are also independent nanoscale cavities / holes on the surface of the copper substrate; there are also independent micron-scale cavities on the surface of the copper substrate.

3. The subtractive etching micro-nano multi-level rough structure copper surface for enhancing boiling heat transfer according to claim 1, characterized in that: Multiple nano-scale granular protrusions are connected into a sheet-like structure.

4. The subtractive etching micro-nano multi-level rough structure copper surface for enhancing boiling heat transfer according to claim 1, characterized in that: The lateral size of the micron-scale cavity (size parallel to the copper surface) is 1um-15μm, and the depth is 500nm-15μm. The size of the nanoscale cavity / hole (size parallel to the copper surface) is 150nm-800nm, and the depth is 50nm-600nm. The size of the nanoscale granular protrusion structure (diameter structure size) is 40nm-200nm. The micro-nano multi-level structure composed of the three structures provides multi-level characteristics for surface functionality.

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

6. The subtractive etching micro-nano multi-level rough structure copper surface for enhancing boiling heat transfer according to claim 1, characterized in that: The final result is a cross-scale multi-level rough structure in which micron-scale cavities, nano-scale cavities / holes, nano-scale granular protrusions, and micron-scale block / sheet structures formed on the surface of the unetched copper substrate are intertwined.

7. A method for preparing a copper surface with a micro-nano multi-level rough structure for enhancing boiling heat transfer by subtractive etching according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step A: ultrasonically cleaning the copper substrate using a cleaning solution; Step B: Using a mixed aqueous solution of ammonium persulfate and chloride as an etching solution, the cleaned copper substrate is placed in the etching solution for etching. After the etching is completed, the subtractive etching micro-nano multi-level rough structure surface prepared by cleaning is obtained. The mixed aqueous solution of ammonium persulfate and chloride, wherein ammonium persulfate and chloride are 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°C.

8. The method for preparing a copper surface with a subtractive etching micro-nano multi-level rough structure for enhanced boiling heat transfer according to claim 7, characterized in that: In the step B, the copper substrate is placed in an etching solution for etching, and the etching time is 1 min to 15 min.

9. In the cleaning process after etching in step B, the target metal substrate is cleaned with ethanol using low-power ultrasonic cleaning to remove residual etching solution in the micro-nano multi-level structure generated by etching.

10. Application of the subtractive etching micro-nano multi-level rough structure copper surface according to any one of claims 1 to 6 in the field of evaporation / boiling phase change heat transfer technology.

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