A multi-stage micro-nano inverse simple cubic structure and a preparation method thereof

Abstract

The application discloses a multistage micro-nano inverse simple cubic structure and a preparation method thereof, and belongs to the technical field of electronic device heat dissipation and two-phase heat exchange. The multistage micro-nano inverse simple cubic structure comprises a three-dimensional interconnected porous framework composed of an inverse simple cubic array, a micro-groove structure distributed on the surface of the three-dimensional interconnected porous framework, and a copper oxide nanowire rough layer covering the surface of the three-dimensional interconnected porous framework. The multistage micro-nano inverse simple cubic structure is formed by macroscopic interconnected channels, micro-grooves and nanowires on the surface of a copper substrate, so that the critical heat flow density and the boiling heat transfer coefficient are simultaneously improved. The multistage micro-nano inverse simple cubic structure provides a critical heat flow density of 520 W / cm 2 and a boiling heat transfer coefficient of 571 kW / m 2 ·K, and embodies the effect of the application in solving the problem that the capillary backfilling and the permeation liquid supplementing channel are difficult to be considered in the porous structure.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation and two-phase heat exchange technology for electronic devices, specifically to a multi-level micro / nano inverse simple cubic structure and its preparation method. Background Technology

[0002] As electronic chips and optoelectronic devices develop towards higher integration, higher performance, and miniaturization, the heat generation per unit area of ​​these devices continues to rise, placing higher demands on heat dissipation and temperature control technologies. Heat dissipation bottlenecks have become a key issue restricting the development of the electronics and optoelectronic industries. This is especially true when heat flux density exceeds 100 W / cm². 2 Under certain operating conditions, traditional natural convection and single-phase liquid cooling methods are insufficient for effective heat dissipation. In contrast, two-phase heat exchange systems utilize the large amount of latent heat absorbed by the phase change of the working fluid, removing more heat per unit area. Therefore, they offer significant advantages in improving the lifespan and operational reliability of electronic devices and possess potential for further engineering and expansion applications. Among these, nucleate boiling achieves highly efficient heat exchange through a cyclical vaporization and liquid replenishment process, and is considered a highly promising thermal management technology due to its high heat transfer intensity.

[0003] The key to achieving high-performance boiling heat transfer lies in simultaneously improving the boiling heat transfer coefficient and the critical heat flux. However, there is an inherent contradiction between these two in terms of mechanism. Improving the boiling heat transfer coefficient often depends on a denser number of bubble nucleation sites, but too many nucleation sites will promote the rapid growth and merging of bubbles under high heat flux, thereby forming local gas films or dry spots, hindering liquid replenishment and triggering a boiling crisis, which will reduce the critical heat flux.

[0004] To address this contradiction, a common strategy for enhancing boiling is to introduce porous / capillary wicking structures. These structures utilize capillary forces to drive liquid recirculation, maintaining the wettability of the heated surface and ensuring stable liquid supply. To increase the critical heat flux, the wicking structure must possess excellent wicking properties, namely high capillary force and high permeability. High capillary force provides sufficient driving force for liquid recirculation, while high permeability reduces recirculation resistance. However, capillary force and permeability are in competition. Reducing the pore size increases capillary pressure, thus enhancing the driving force, but significantly reduces permeability and increases recirculation resistance. Conversely, increasing the pore size reduces flow resistance but weakens the capillary driving force. Simultaneously, bubble nucleation places specific requirements on structural size. Generally, the typical cavity / pore size for effectively triggering stable nucleation is considered to be 1μm to 10μm. If the structural feature size is too large, it cannot provide nucleation sites; if it is too small, it can easily lead to excessively high recirculation resistance or limited bubble expulsion. Summary of the Invention

[0005] This invention provides a multi-level micro / nano anti-simple cubic structure and its preparation method, which effectively solves the technical problem that existing boiling heat transfer methods cannot simultaneously improve the boiling heat transfer coefficient and critical heat flux density. At the same time, it provides a multi-level micro / nano anti-simple cubic structure that achieves a synergistic improvement in critical heat flux density and boiling heat transfer coefficient without sacrificing the macroscopic replenishment channel. This overcomes the different requirements of capillary force and permeability on feature size, achieves high wicking performance, and at the same time takes into account the requirements of bubble nucleation on feature size.

[0006] The first objective of this invention is to provide a multi-level micro / nano inverse simple cubic structure fabricated on a copper substrate. The multi-level micro / nano inverse simple cubic structure comprises: a three-dimensional interconnected porous framework composed of an inverse simple cubic array, the three-dimensional interconnected porous framework having periodic cavities and windows, the cavities and windows being interconnected to form three-dimensional fluid channels for enhancing the replenishment of liquid from the main fluid region to the boiling region; a microgroove structure distributed on the surface of the three-dimensional interconnected porous framework, the microgroove structure being formed by inverting and replicating a layer-by-layer printed texture, for providing bubble nucleation sites and regulating bubble growth and detachment; and a copper oxide nanowire roughening layer covering the surface of the three-dimensional interconnected porous framework, serving as a superhydrophilic wetting surface for enhancing liquid rewetting and gas-liquid phase change heat transfer processes.

[0007] In this invention, the multi-level micro-nano anti-simple cubic structure is formed on the surface of a copper substrate by forming a multi-level capillary network consisting of macroscopic interconnected channels, microgrooves and nanowires, thereby achieving a simultaneous increase in critical heat flux density and boiling heat transfer coefficient.

[0008] The macroscopic interconnected channels are a three-dimensional interconnected porous framework composed of an inverse simple cubic array, used to provide liquid replenishment channels and increase the critical heat flux density. The three-dimensional interconnected porous framework has high porosity and low tortuosity to achieve high permeability and reduce liquid replenishment resistance.

[0009] A microgroove structure is constructed on the surface of the three-dimensional interconnected porous framework to increase effective bubble nucleation sites and improve the boiling heat transfer coefficient. The microgroove structure is used to add microscale grooves, edge and corner features to provide bubble nucleation sites and regulate bubble growth and detachment.

[0010] A roughened layer of copper oxide nanowires is coated on the surface of the three-dimensional interconnected porous framework and microgroove structure to provide superhydrophilicity and increase the solid-liquid contact area, thereby synergistically enhancing the liquid rewetting and gas-liquid phase change processes.

[0011] The multi-level micro / nano anti-simple cubic structure of this invention has a critical heat flux density of 520 W / cm² under normal pressure saturated deionized water boiling conditions. 2 The boiling heat transfer coefficient is 571 kW / m³. 2·K. Compared to a smooth copper substrate, the critical heat flux density and boiling heat transfer coefficient of the multi-level micro-nano inverse simple cubic structure of the present invention are increased by 1630% and 633%, respectively.

[0012] In a preferred embodiment, the anti-simple cubic array is a negative model of a simple cubic sphere stacked structure. The anti-simple cubic array is formed by periodically arranging anti-simple cubes along the x and y directions, with cavities formed between four adjacent anti-simple cubes. Each cavity has four windows, and adjacent cavities are connected through corresponding windows. In this invention, the three-dimensional interconnected porous framework has regularly arranged and interconnected periodic cavities and windows, forming a three-dimensional fluid channel. In this invention, the cavities are spherical, and their characteristic dimension is the diameter of the sphere; the windows are circular, and their characteristic dimension is the diameter of the circle.

[0013] In a preferred embodiment, the diameter of the cavity is 0.5 mm to 1 mm, the diameter of the window is 0.2 mm to 0.4 mm, and the ratio of the diameter of the window to the diameter of the cavity is 0.35 to 0.7.

[0014] In a preferred embodiment, the microgroove structure is formed by transferring layer-by-layer textures during a reverse replication process, providing microscale surface features. The microgroove structure includes multiple microgrooves, each with a height of 5 μm to 10 μm and a width of 1 μm to 100 μm. In this invention, the microscale surface features include microscale grooves, edge and corner features, to provide bubble nucleation sites and regulate bubble growth and detachment.

[0015] In a preferred embodiment, the copper oxide nanowire roughening layer has a diameter of 0.1 μm to 0.5 μm and a length of 1 μm to 5 μm.

[0016] In a preferred embodiment, the static water contact angle of the roughened copper oxide nanowire layer is 0° to 10°; preferably 0° to 4°.

[0017] The second objective of this invention is to provide a method for preparing multi-level micro / nano anti-simple cubic structures, comprising the following steps: A simple cubic template with microgrooves on its surface was obtained by layer-by-layer micro-nano 3D printing. The pores of the simple cubic template were filled by electrochemical deposition, and the template was then removed to obtain a three-dimensional interconnected porous framework with microgrooves on its surface. The three-dimensional interconnected porous framework with microgrooves was then subjected to chemical oxidation and thermal treatment to construct a roughened layer of copper oxide nanowires, resulting in a multi-level micro-nano anti-simple cubic structure.

[0018] As a preferred embodiment, the method of layer-by-layer micro / nano 3D printing is as follows: projection micro-stereolithography or equivalent layer-by-layer photopolymerization is used to form a printing layer with a thickness of 5μm to 10μm; the printing layer generates layer-by-layer texture during the layer-by-layer micro / nano 3D printing process, forming a layer texture undulation structure; the layer texture undulation structure is transferred to the surface of a three-dimensional interconnected porous framework during the electrochemical deposition filling inversion replication process, forming a microgroove structure.

[0019] In this invention, the layer-by-layer micro-nano 3D printing is a projection micro-stereolithography, and the thickness of the printed layer is 5μm to 10μm; preferably 5μm.

[0020] In a preferred embodiment, the electrolyte for electrochemical deposition is composed of a copper salt, an inorganic acid, a surfactant, a chloride ion additive, and water. The concentration of the copper salt is 0.3 mol / L to 1.0 mol / L, the concentration of the inorganic acid is 0.5 mol / L to 2.0 mol / L, and the total concentration of the surfactant and chloride ion additive is 1 g / L to 2 g / L. More preferably, the copper salt is copper sulfate; the inorganic acid is sulfuric acid; the surfactant is sodium dodecyl sulfonate; the chloride ion additive is sodium chloride; and the thickness of the anti-simple cubic copper framework is 1 mm.

[0021] As a preferred embodiment, the electrochemical deposition method is as follows: depositing at a current density of 1 mA / cm² to 5 mA / cm² for 5 min to 30 min, and then depositing at a current density of 5 mA / cm² to 20 mA / cm² for 6 h to 18 h, to form an inverse simple cubic structure copper framework.

[0022] In a preferred embodiment, the method for removing the simple cubic structure template is to use an alkaline solution, wherein the alkaline solution is a sodium hydroxide solution with a concentration of 0.5 mol / L to 2.0 mol / L, the removal temperature is 60℃ to 80℃, and the removal time is 2h to 6h.

[0023] In a preferred embodiment, the chemical oxidation method involves placing a three-dimensional interconnected porous framework with a microgrooved surface in a mixed solution of sodium hydroxide and ammonium persulfate, and reacting it at 30°C–40°C for 15–120 minutes to generate a copper hydroxide nanowire layer in situ on the surface of the three-dimensional interconnected porous framework with a microgrooved surface. In the mixed solution of sodium hydroxide and ammonium persulfate, the concentration of sodium hydroxide is 2 mol / L–3 mol / L, and the concentration of ammonium persulfate is 0.1 mol / L–0.2 mol / L. The heat treatment method involves heat treatment at 150°C–200°C for 10–30 minutes to transform the copper hydroxide nanowires into copper oxide nanowires, forming a roughened copper oxide nanowire layer. In this invention, the heat treatment transforms the copper hydroxide nanowires into copper oxide nanowires to improve structural stability.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: Addressing the technical challenge of simultaneously improving both the boiling heat transfer coefficient and critical heat flux density in existing boiling heat transfer methods, this invention provides a multi-level micro / nano inverse simple cubic structure. This multi-level micro / nano inverse simple cubic structure comprises a three-dimensional interconnected porous framework composed of an inverse simple cubic array, microgroove structures distributed on the surface of the three-dimensional interconnected porous framework, and a roughened layer of copper oxide nanowires covering the surface of the three-dimensional interconnected porous framework. This invention achieves simultaneous improvement of critical heat flux density and boiling heat transfer coefficient by forming a multi-level capillary network on the surface of a copper substrate, consisting of macroscopic interconnected channels, microgrooves, and nanowires.

[0025] This invention employs an inverse simple cubic array to construct a three-dimensional interconnected porous framework. The three-dimensional interconnected porous framework has high porosity, low tortuosity, and high permeability, which can significantly reduce the replenishment resistance under high heat flux density boiling conditions and enhance the rapid replenishment of liquid from the main fluid region to the boiling region, inhibiting the formation and expansion of dry spots, thereby effectively increasing the critical heat flux density.

[0026] This invention introduces a microgroove structure on the surface of a three-dimensional interconnected porous skeleton, formed by layer-by-layer printing of layer-by-layer texture replication. The microgroove structure can provide a large number of microscale surface features, such as microscale grooves, edge and corner features, which can significantly increase the effective bubble nucleation sites and regulate the bubble growth and detachment process, which is beneficial to improving the boiling heat transfer coefficient.

[0027] This invention generates a roughened layer of copper oxide nanowires in situ on the surface of a three-dimensional interconnected porous framework through chemical oxidation and heat treatment. The roughened layer of copper oxide nanowires endows the structure with stable superhydrophilic properties and increases the effective solid-liquid contact area, thereby achieving a synergistic improvement in critical heat flux density and boiling heat transfer coefficient without sacrificing the macroscopic liquid replenishment channel.

[0028] The multi-level micro / nano inverse simple cubic structure provided by this invention can maintain stable boiling operation with high heat flux density under normal pressure saturated deionized water pool boiling conditions, and can simultaneously provide 520 W / cm². 2 The critical heat flux density and 571 kW / m 2 The boiling heat transfer coefficient of K reflects the effectiveness of this invention in addressing the difficulty of simultaneously managing capillary recharge and permeation replenishment channels in porous structures. Compared to a smooth copper substrate, the critical heat flux density and boiling heat transfer coefficient of the multi-level micro / nano inverse simple cubic structure of this invention are increased by 1630% and 633%, respectively. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the multi-level micro-nano anti-simple cubic structure prepared in Example 1 of the present invention, wherein a is a three-dimensional interconnected porous framework composed of anti-simple cubic structure, b is a microgroove structure formed by layer-by-layer micro-nano 3D printing with texture inversion, c is a rough layer of copper oxide nanowires, d is the size diagram corresponding to the parameters in a, e is the size diagram corresponding to the parameters in b, and f is the size diagram corresponding to the parameters in c.

[0030] Figure 2 This is a scanning electron microscope image of a three-dimensional interconnected porous framework with microgroove structures on the surface of a multi-level micro / nano anti-simple cubic structure prepared in Example 1 of the present invention.

[0031] Figure 3 This is a scanning electron microscope image of the microgroove structure in the multi-level micro / nano anti-simple cubic structure prepared in Example 1 of the present invention.

[0032] Figure 4 This is a scanning electron microscope image of the roughened layer of copper oxide nanowires in the multi-level micro / nano anti-simple cubic structure prepared in Example 1 of the present invention.

[0033] Figure 5 The image shows the contact angle test results of the superhydrophilic surface of the multi-level micro / nano anti-simple cubic structure prepared in Example 1 of this invention.

[0034] Figure 6 The boiling experiment test diagram shows the multi-level micro / nano anti-simple cubic structure prepared in Example 1 of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0036] It should be noted that the technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Certain terms are used in this invention to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This invention does not distinguish components based on differences in terminology, but rather on differences in function. As used throughout the specification and claims, "comprising" is an open-ended term and should be understood as "including but not limited to".

[0037] Existing technologies typically employ two main approaches to improve boiling heat transfer performance: active enhancement and passive enhancement. Active enhancement, such as external excitations like electric, magnetic, or acoustic fields, can promote bubble detachment and fluid disturbance, but these systems are complex to implement, energy-intensive, and have limited engineering applicability. Therefore, passive enhancement is more engineering-friendly, aiming to improve the boiling process without introducing additional energy consumption through structural and surface design. Porous / capillary structures can enhance liquid replenishment and delay dry spot expansion to increase the critical heat flux density, while microscale surface features can provide nucleation sites and modulate bubble behavior to improve the boiling heat transfer coefficient. However, existing enhancement structures often struggle to simultaneously meet the requirements of continuous replenishment and efficient nucleation under high heat flux density conditions. On one hand, improving wicking performance requires structures with both high capillary drive and high permeability, which compete for feature size. On the other hand, bubble nucleation typically requires micrometer-scale feature sizes (e.g., 1 μm–10 μm) to provide stable nucleation cavities / edge structures. Therefore, developing a boiling heat transfer enhancement structure that can synergistically achieve low-resistivity rapid liquid replenishment and efficient and stable nucleation within the same structure is an important requirement in the field of thermal management. Based on this, this invention provides a multi-level micro / nano anti-simple cubic structure and its preparation method.

[0038] The technical solution of the present invention will be analyzed and described in detail below.

[0039] This invention provides a multi-level micro / nano inverse simple cubic structure, fabricated on a copper substrate. The multi-level micro / nano inverse simple cubic structure includes: a three-dimensional interconnected porous framework composed of an inverse simple cubic array, the framework having periodic cavities and windows interconnected to form three-dimensional fluid channels, used to enhance the replenishment of liquid from the main fluid region to the boiling region; a microgroove structure distributed on the surface of the three-dimensional interconnected porous framework, formed by inverting and replicating layer-by-layer printed textures, used to provide bubble nucleation sites and regulate bubble growth and detachment; and a copper oxide nanowire roughening layer covering the surface of the three-dimensional interconnected porous framework, serving as a superhydrophilic wetting surface to enhance liquid rewetting and gas-liquid phase change heat transfer processes.

[0040] The multi-level micro / nano inverse simple cubic structure of this invention is formed on the surface of a copper substrate, creating a multi-level capillary network composed of macroscopic interconnected channels, microgrooves, and nanowires. The macroscopic interconnected channels are a three-dimensional interconnected porous framework composed of an inverse simple cubic array, used to provide liquid replenishment channels and increase the critical heat flux density. The three-dimensional interconnected porous framework has high porosity and low tortuosity to achieve high permeability and reduce liquid replenishment resistance.

[0041] A microgroove structure is constructed on the surface of a three-dimensional interconnected porous framework to increase effective bubble nucleation sites and improve the boiling heat transfer coefficient. The microgroove structure adds microscale grooves, edges, and corner features to provide bubble nucleation sites and regulate bubble growth and detachment. A copper oxide nanowire roughening layer is coated on the surface of the three-dimensional interconnected porous framework and the microgroove structure to provide superhydrophilicity and increase the solid-liquid contact area, thereby synergistically enhancing liquid rewetting and gas-liquid phase change processes. This invention achieves a simultaneous improvement in critical heat flux and boiling heat transfer coefficient through the synergistic effect of the three-dimensional interconnected porous framework, the microgroove structure, and the copper oxide nanowire roughening layer.

[0042] The multi-level micro / nano inverse simple cubic structure of this invention, under high heat flux density boiling conditions, enhances the rapid replenishment of liquid from the main fluid region to the boiling region through macroscopically interconnected channels, suppressing the formation and expansion of dry spots, thereby increasing the critical heat flux density. The microgroove structure, derived from the layer-by-layer printing texture transferred during the inversion replication process, provides numerous microscale grooves and edge features on the skeleton surface, increasing effective nucleation sites and regulating bubble growth and detachment, thus improving the boiling heat transfer coefficient. The roughened layer of copper oxide nanowires, generated in situ through chemical oxidation and heat treatment, possesses superhydrophilic properties and increases the effective solid-liquid contact area, further enhancing liquid rewetting and gas-liquid phase transition processes, thereby achieving a synergistic improvement in critical heat flux density and boiling heat transfer coefficient.

[0043] The multi-level micro / nano anti-simple cubic structure provided by this invention can maintain stable nucleation boiling heat transfer capability in the high heat flux density range, with a critical heat flux density of 520 W / cm². 2 Meanwhile, the maximum boiling heat transfer coefficient is 571 kW / m³. 2 • K. Boiling test results show that the heat transfer coefficient of a smooth copper surface is 33 kW / m. 2 K, critical heat flux density is 71 W / cm² 2 The smooth copper surface is a copper substrate without any micro or nano structures. Compared with the smooth copper surface, the heat transfer coefficient and critical heat flux density of the multi-level micro-nano anti-simple cubic structure provided by the present invention are increased by 1630% and 633%, respectively.

[0044] The multi-level micro-nano anti-simple cubic structure of the present invention will be described in detail below through specific embodiments.

[0045] Example 1 A method for fabricating a multi-level micro / nano anti-simple cubic structure includes the following steps: Step 1, Substrate Pretreatment: First, a high-purity copper sheet with dimensions of 100mm×65mm×0.3mm is selected as the substrate. It is then ultrasonically cleaned with acetone, ethanol and deionized water in sequence to remove organic contaminants from the surface. After that, it is etched in 0.5M dilute hydrochloric acid for 3 minutes to remove the oxide layer, thus obtaining the pretreated copper sheet.

[0046] Step 2, Layer-by-layer micro / nano 3D printing of a simple cubic structure template: A simple cubic structure template is printed layer by layer using projection micro-stereolithography, with a layer thickness of 10 μm. After printing, the template undergoes cleaning, post-curing, and drying. During the layer-by-layer forming process, a layer-by-layer texture (layer undulation structure) is formed on the template surface for subsequent reverse replication of microgrooves. The template structural parameters are: cavity diameter dimensions... d p =0.7mm, window diameter d w =0.28mm, d w / d p =0.4.

[0047] Step 3: Template fixing: Fix the simple cubic structure template to the designated area on the surface of the pretreated copper sheet, and ensure that the template and the pretreated copper sheet are reliably attached to avoid detachment during the electrodeposition process.

[0048] Step 4: Template-Assisted Electrochemical Deposition to Construct an Inverse Simple Cubic Copper Framework: Using a pretreated copper sheet as the cathode and a copper block as the anode, electrodeposition is performed in an electrochemical deposition electrolyte. The electrolyte consists of 0.5 mol / L copper sulfate, 2.0 mol / L sulfuric acid, and 2 g / L sodium dodecyl sulfate and sodium chloride. The mass ratio of sodium dodecyl sulfate to sodium chloride is 1:1. The electrochemical deposition process includes: first, using 1 mA / cm²... 2 Deposition for 30 minutes to enhance adhesion between the template and the substrate, then at 20 mA / cm². 2 After 6 hours of deposition, a copper framework with an inverse simple cubic structure and a thickness of 1 mm was obtained. During the electrodeposition process, copper deposition filled the pores of the template to form an inverse simple cubic framework, while the layer texture on the template surface was transferred to the framework surface during the inversion replication process to form a microgroove structure.

[0049] Step 5: Remove the template to obtain a self-supporting inverse simple cubic structure: Place the sample after electrodeposition in step 4 in a 0.5 mol / L sodium hydroxide solution and treat it at 80℃ for 6 h to remove the template; then wash it thoroughly with deionized water and dry it to obtain a self-supporting inverse simple cubic structure.

[0050] Step 6: Construction of a roughened copper oxide nanowire layer through chemical oxidation and thermal treatment: The self-supporting inverse simple cubic structure was immersed in a mixed solution of sodium hydroxide and ammonium persulfate for chemical oxidation, with a sodium hydroxide concentration of 2.5 mol / L and an ammonium persulfate concentration of 0.13 mol / L. The reaction was carried out at 40℃ for 30 min, resulting in the in-situ formation of a copper hydroxide nanowire layer on the structure surface. Subsequently, heating at 180℃ for 30 min transformed the copper hydroxide nanowires into copper oxide nanowires and improved the structural stability, thereby obtaining a multi-level micro / nano inverse simple cubic structure with a roughened copper oxide nanowire layer on the surface. The resulting copper oxide nanowires had a diameter of 0.1 μm, a length of 3 μm, and a static water contact angle of approximately 3°.

[0051] Example 2 A method for fabricating a multi-level micro / nano anti-simple cubic structure includes the following steps: Step 1, Substrate Pretreatment: First, a high-purity copper sheet with dimensions of 100mm×65mm×0.3mm is selected as the substrate. It is then ultrasonically cleaned with acetone, ethanol and deionized water in sequence to remove organic contaminants from the surface. After that, it is etched in 1M dilute hydrochloric acid for 1 minute to remove the oxide layer, thus obtaining the pretreated copper sheet.

[0052] Step 2, Layer-by-layer micro / nano 3D printing of a simple cubic structure template: A simple cubic structure template is printed layer by layer using projection micro-stereolithography, with a layer thickness of 5μm. After printing, the template undergoes cleaning, post-curing, and drying. During the layer-by-layer forming process, a layer-by-layer texture (layer texture undulation structure) is formed on the template surface for subsequent reverse replication of microgrooves. The template structural parameters are: cavity diameter dimensions... d p =0.5mm, window diameter d w =0.2mm, d w / d p =0.4.

[0053] Step 3: Template fixing: Fix the simple cubic structure template to the designated area on the surface of the pretreated copper sheet, and ensure that the template is reliably attached to the copper substrate to avoid detachment during the electrodeposition process.

[0054] Step 4: Template-Assisted Electrochemical Deposition to Construct an Inverse Simple Cubic Copper Framework: Using a pretreated copper sheet as the cathode and a copper block as the anode, electrodeposition is performed in an electrochemical deposition electrolyte. The electrolyte consists of 1 mol / L copper sulfate, 1 mol / L sulfuric acid, and 1 g / L sodium dodecyl sulfate and sodium chloride. The mass ratio of sodium dodecyl sulfate to sodium chloride is 1:1. The electrochemical deposition process includes: first, using 5 mA / cm²... 2Deposition for 20 minutes to enhance adhesion between the template and the substrate, then at 10 mA / cm 2 After 12 hours of deposition, a copper framework with an inverse simple cubic structure and a thickness of 1 mm was obtained. During the electrodeposition process, copper deposition filled the pores of the template to form an inverse simple cubic framework, while the layer texture on the template surface was transferred to the framework surface during the inversion replication process to form a microgroove structure.

[0055] Step 5: Remove the template to obtain a self-supporting inverse simple cubic structure: Place the sample after electrodeposition in step 4 in a 2 mol / L sodium hydroxide solution and treat it at 60℃ for 3 h to remove the template; then wash it thoroughly with deionized water and dry it to obtain a self-supporting inverse simple cubic structure.

[0056] Step 6: Construction of a roughened copper oxide nanowire layer through chemical oxidation and thermal treatment: The self-supporting inverse simple cubic structure was immersed in a mixed solution of sodium hydroxide and ammonium persulfate for chemical oxidation, with a sodium hydroxide concentration of 2 mol / L and an ammonium persulfate concentration of 0.15 mol / L. The reaction was carried out at 35℃ for 60 min, resulting in the in-situ formation of a copper hydroxide nanowire layer on the structure surface. Subsequently, heating at 160℃ for 60 min transformed the copper hydroxide nanowires into copper oxide nanowires and improved the structural stability, thereby obtaining a multi-level micro / nano inverse simple cubic structure with a roughened copper oxide nanowire layer on the surface. The resulting copper oxide nanowires had a diameter of 0.2 μm, a length of 5 μm, and a static water contact angle of approximately 2°.

[0057] In Examples 1 and 2 above, multi-level micro / nano inverse simple cubic structures for enhanced boiling heat transfer were successfully prepared. The microstructure and performance of the multi-level micro / nano inverse simple cubic structure prepared in Example 1 are analyzed below.

[0058] Test 1: Microscopic morphology analysis.

[0059] Figure 1 and Figure 2 This is a schematic diagram and scanning electron microscope image of the multi-level micro / nano anti-simple cubic structure prepared in Example 1 of the present invention. Figure 1 and Figure 2 As can be seen, the structure is a three-dimensional interconnected porous skeleton composed of an inverse simple cubic array, with regularly arranged cavities and windows inside. The cavities and windows are interconnected to form a three-dimensional fluid channel, thereby providing a low-torsion interconnection path for liquid replenishment and reducing replenishment resistance.

[0060] Figure 3 This is a scanning electron microscope image of the surface microgroove structure of the multi-level micro / nano anti-simple cubic structure in Embodiment 1 of the present invention. Figure 3It can be seen that the skeleton surface has a microgroove / layer texture structure distributed along the layer-by-layer forming direction. It should be noted that the microgroove structure originates from the transfer of the layer texture formed during the layer-by-layer micro / nano 3D printing template process during the reverse replication process. It provides a large number of microscale grooves, edge and corner features on the skeleton surface, which can serve as effective bubble nucleation sites and are conducive to controlling the bubble growth, detachment and renewal process, thereby enhancing the nucleation boiling heat transfer intensity and improving the boiling heat transfer coefficient.

[0061] Figure 4 This is a scanning electron microscope (SEM) image of the surface roughened layer of copper oxide nanowires with a multi-level micro / nano anti-simple cubic structure, as described in Example 1 of the present invention. Figure 4 As can be seen, after chemical oxidation / thermal treatment, a dense copper oxide nanowire roughening layer is formed in situ on the skeleton surface. This copper oxide nanowire roughening layer can significantly improve surface wettability and increase the effective solid-liquid contact area, thereby enhancing capillary rewetting ability and improving interfacial wetting stability. This is beneficial for inhibiting the formation and spread of dry spots, and thus increasing the critical heat flux density.

[0062] Figure 5 This is a schematic diagram showing the contact angle test results of the superhydrophilic surface of the multi-level micro / nano anti-simple cubic structure in Embodiment 1 of the present invention. Figure 5 As can be seen, the droplets spread rapidly on the surface of the structure in Example 1, and the measured static water contact angle is 3°. This indicates that the multi-level micro-nano anti-simple cubic structure surface of Example 1 possesses superhydrophilic characteristics. It should be noted that the superhydrophilic properties can accelerate the spreading and replenishment of liquid on the framework surface, and work together with the low-resistance transport of the three-dimensional interconnected channels to improve the stability of liquid supply under high heat flux density conditions and suppress local drying.

[0063] Test 2: Boiling test.

[0064] The multi-level micro-nano anti-simple cubic structure sample prepared in Example 1 was installed on a pool boiling heat transfer test platform. Deionized water was used as the working fluid. The heating power was gradually increased under normal pressure saturated deionized water conditions. The wall temperature and heat flux density data were recorded, and the boiling heat transfer curve and the curve of boiling heat transfer coefficient as a function of heat flux density were obtained. Figure 6 This is a boiling experiment test curve of the multi-level micro / nano anti-simple cubic structure in Embodiment 1 of the present invention. Figure 6 It can be seen that the multi-level micro / nano anti-simple cubic structure can maintain stable nucleate boiling heat transfer capacity in the high heat flux density range, with a critical heat flux density of 520 W / cm². 2 Meanwhile, the maximum boiling heat transfer coefficient is 571 kW / m³. 2 • K. Boiling test results show that the heat transfer coefficient of a smooth copper surface is 33 kW / m. 2 K, critical heat flux density is 71 W / cm²2 The smooth copper surface is a copper substrate without any micro / nano structures. Compared to the smooth copper surface, the heat transfer coefficient and critical heat flux density of the multi-level micro / nano inverse simple cubic structure in Example 1 are increased by 1630% and 633%, respectively.

[0065] The above results show that the embodiments of the present invention provide a low-resistance liquid replenishment channel through an anti-simple cubic three-dimensional interconnected channel, and enhance the nucleation and rewetting process by combining surface microgrooves and a superhydrophilic rough layer of copper oxide nanowires, thereby achieving a simultaneous increase in critical heat flux density and boiling heat transfer coefficient under high heat flux density conditions.

[0066] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A multi-level micro / nano anti-simple cubic structure, characterized in that, The multi-level micro / nano inverse simple cubic structure is fabricated on the surface of a copper substrate, and the multi-level micro / nano inverse simple cubic structure includes: A three-dimensional interconnected porous framework, composed of an inverse simple cubic array, has periodic cavities and windows. The cavities and windows are interconnected to form a three-dimensional fluid channel, which is used to enhance the replenishment of liquid from the main fluid region to the boiling region. Microgroove structures are distributed on the surface of the three-dimensional interconnected porous skeleton. The microgroove structures are formed by reverse replication of the layered texture printed layer by layer, which is used to provide bubble nucleation sites and regulate bubble growth and detachment. A roughened layer of copper oxide nanowires covers the surface of the three-dimensional interconnected porous framework, serving as a superhydrophilic wetting surface to enhance liquid rewetting and gas-liquid phase change heat transfer processes.

2. The multi-level micro / nano anti-simple cubic structure according to claim 1, characterized in that, The anti-simple cube array is a negative module of a simple cube sphere stacked structure. The anti-simple cube array is formed by periodically arranging anti-simple cubes along the x and y directions, and cavities are formed between four adjacent anti-simple cubes. Each cavity has four windows, and two adjacent cavities are connected through corresponding windows.

3. The multi-level micro / nano anti-simple cubic structure according to claim 2, characterized in that, The diameter of the cavity is 0.5mm to 1mm, the diameter of the window is 0.2mm to 0.4mm, and the ratio of the diameter of the window to the diameter of the cavity is 0.35 to 0.

7.

4. The multi-level micro / nano anti-simple cubic structure according to claim 1, characterized in that, The microgroove structure is formed by transferring layer-by-layer textures during the inversion replication process, and is used to provide microscale surface features; The microgroove structure includes multiple microgrooves, each of which has a height of 5μm to 10μm and a width of 1μm to 100μm.

5. The multi-level micro / nano anti-simple cubic structure according to claim 1, characterized in that, In the roughened layer of copper oxide nanowires, the diameter of the copper oxide nanowires is 0.1 μm to 0.5 μm and the length is 1 μm to 5 μm; the static water contact angle of the roughened layer of copper oxide nanowires is 0° to 10°.

6. A method for preparing a multi-level micro / nano anti-simple cubic structure according to any one of claims 1 to 5, comprising the following steps: A simple cubic template with a microgroove structure on the surface was obtained by layer-by-layer micro-nano 3D printing. The pores of the simple cubic template are filled by electrochemical deposition, and the simple cubic template is removed to obtain a three-dimensional interconnected porous skeleton with a microgroove structure on the surface. A three-dimensional interconnected porous framework with a microgroove structure on its surface was chemically oxidized and thermally treated to construct a roughened layer of copper oxide nanowires, resulting in a multi-level micro / nano inverse simple cubic structure.

7. The method for preparing the multi-level micro / nano anti-simple cubic structure according to claim 6, characterized in that, The method of layer-by-layer micro-nano 3D printing is as follows: projection micro-stereolithography or equivalent layer-by-layer photopolymerization printing is used to form a printing layer with a thickness of 5μm to 10μm. The printed layer generates layer-by-layer textures during the layer-by-layer micro-nano 3D printing process, forming a layer texture undulation structure; the layer texture undulation structure is transferred to the surface of a three-dimensional interconnected porous skeleton during the electrochemical deposition filling inversion replication process, forming a microgroove structure.

8. The method for preparing the multi-level micro / nano anti-simple cubic structure according to claim 6, characterized in that, The electrolyte for electrochemical deposition consists of copper salt, inorganic acid, surfactant, chloride ion additive and water. The concentration of copper salt is 0.3 mol / L to 1.0 mol / L, the concentration of inorganic acid is 0.5 mol / L to 2.0 mol / L, and the total concentration of surfactant and chloride ion additive is 1 g / L to 2 g / L. The electrochemical deposition method is as follows: deposit at a current density of 1 mA / cm² to 5 mA / cm² for 5 min to 30 min, and then deposit at a current density of 5 mA / cm² to 20 mA / cm² for 6 h to 18 h to form an inverse simple cubic structure copper framework. The method for removing the simple cubic structure template is to use an alkaline solution, wherein the alkaline solution is a sodium hydroxide solution with a concentration of 0.5 mol / L to 2.0 mol / L, the removal temperature is 60℃ to 80℃, and the removal time is 2h to 6h.

9. The method for preparing the multi-level micro / nano anti-simple cubic structure according to claim 8, characterized in that, The copper salt is copper sulfate; the inorganic acid is sulfuric acid; the surfactant is sodium dodecyl sulfonate; the chloride ion additive is sodium chloride; and the thickness of the anti-simple cubic copper skeleton is 1 mm.

10. The method for preparing the multi-level micro / nano anti-simple cubic structure according to claim 6, characterized in that, The chemical oxidation method is as follows: a three-dimensional interconnected porous framework with a microgroove structure on its surface is placed in a mixed solution of sodium hydroxide and ammonium persulfate, and reacted at 30℃~40℃ for 15min~120min to generate a copper hydroxide nanowire layer in situ on the surface of the three-dimensional interconnected porous framework with a microgroove structure; in the mixed solution of sodium hydroxide and ammonium persulfate, the concentration of sodium hydroxide is 2mol / L~3mol / L, and the concentration of ammonium persulfate is 0.1mol / L~0.2mol / L. The heat treatment method is as follows: heat treatment is carried out at 150℃~200℃ for 10min~30min to transform copper hydroxide nanowires into copper oxide nanowires, forming a rough layer of copper oxide nanowires.

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