Nanoscale through-porous aluminum foil and method of making the same

Abstract

The application relates to the technical field of aluminum foil corrosion preparation, and discloses a nanoscale through-porous aluminum foil and a preparation method thereof, wherein the preparation method comprises the following steps: aluminum foil surface pretreatment, molecular template preparation, resonance frequency measurement, five-stage gradient corrosion, template removal and cleaning and heat treatment. The molecular template is formed into a patterned guide through a self-assembled monolayer and a nanoimprint / lithography technology; different acid liquid combinations are used in the five-stage corrosion, and an alternating voltage frequency related to the inherent resonance frequency of the aluminum foil is applied, so that gradient corrosion control from hole opening, deepening, hole expansion, trimming to fine processing is realized. Through the spatial guidance of the molecular template, the energy focusing of the resonance frequency and the time sequence cooperation of the gradient corrosion, the order, the throughness and the uniformity of the hole structure are significantly improved, the prepared porous aluminum foil has the advantages of controllable pore diameter, high porosity and good mechanical properties, and is suitable for high-tech fields such as battery separators and filter materials.

Description

Technical Field

[0001] This invention relates to the field of aluminum foil etching preparation technology, and in particular to a nanoscale through-porous aluminum foil and its preparation method. Background Technology

[0002] Porous metallic materials, due to their unique structural characteristics and excellent physicochemical properties, have shown great application potential in many high-tech fields. Aluminum, as the most abundant metallic element in the Earth's crust, has advantages such as low density, good electrical conductivity, strong corrosion resistance, and low cost. Porous aluminum foil has important application value in battery separators, filter materials, catalyst carriers, and sensor electrodes.

[0003] Traditional methods for preparing porous aluminum foil mainly include powder metallurgy, foaming, dealloying, and electrochemical etching. Powder metallurgy prepares porous aluminum by mixing aluminum powder with a pore-forming agent, pressing, and sintering. However, this method struggles to achieve high porosity and a uniform pore structure, and the pore size is typically large (above the micrometer level). Foaming prepares porous aluminum by introducing gas or a foaming agent into molten aluminum, but it is difficult to control the pore size and distribution, and it is mainly suitable for three-dimensional bulk materials. Dealloying selectively etches certain components in the aluminum alloy to leave a porous aluminum framework, but it has strict requirements on the alloy composition, and the etching process is difficult to control.

[0004] Electrochemical corrosion is currently the most commonly used method for preparing porous aluminum foil. Its basic principle is to create pores on the surface and inside the aluminum foil through an electrochemical process. Traditional electrochemical corrosion methods typically use a DC power supply to apply voltage to the aluminum foil in an acidic or alkaline electrolyte, causing anodic dissolution of the aluminum to form pores. However, traditional electrochemical corrosion methods have the following inherent drawbacks: The corrosion process is characterized by several challenges: First, the formation of pores is highly random. Corrosion initiation points are typically located at defects, impurities, or grain boundaries on the aluminum foil surface, resulting in uneven pore distribution and varying pore sizes. Second, pore connectivity is poor. During corrosion, pores tend to close inside the aluminum foil, forming numerous blind pores rather than through pores, severely impacting material transport efficiency. Third, pore size control is difficult. Precise control of pore size at the nanoscale is challenging, particularly achieving controllable adjustment within the 10-100 nm range. Fourth, process repeatability is low. The corrosion process is extremely sensitive to parameters such as the aluminum foil surface condition, electrolyte composition, temperature, and current density; even minor changes can lead to significant differences in pore structure. Fifth, structural order is poor. The formed pores are mostly randomly distributed, lacking orderly arrangement, which limits applications in areas requiring regular structures.

[0005] To overcome these problems, researchers have tried various improvement methods. The template method uses anodic aluminum oxide (AAO) or porous polymers as templates, filling the template pores with aluminum or aluminum alloys through physical or chemical methods, and then removing the template to obtain a porous structure. This method can obtain ordered pore structures, but the template preparation process is complex, and the interface between the template and the aluminum foil can affect pore quality. The additive method adds surfactants, polymers, or metal ions to the etching solution to adjust the pore structure by changing the properties of the etching interface; however, additives may introduce impurities, affecting material purity. The current waveform control method uses pulsed current, alternating current, or special waveform current instead of direct current to influence the etching process by modulating the current parameters, but the improvement effect is limited.

[0006] While these improved methods have enhanced the performance of porous aluminum foil to some extent, they have not fundamentally solved the core problems of precise control of nanoscale pores, complete interconnection of pores, and structural order. In particular, existing technologies are insufficient for applications requiring nanoscale through-pores (such as high-performance battery separators and precision filter membranes). Therefore, developing a novel method for preparing porous aluminum foil capable of precisely controlling the nanoscale through-pore structure has significant scientific and practical value. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a nanoscale through-hole porous aluminum foil and its preparation method, which aims to solve the problems of disordered pore structure, poor permeability, difficulty in precise control of pore size and low process repeatability in the preparation of porous aluminum foil by existing electrochemical corrosion methods.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing nanoscale through-porous aluminum foil, comprising the following steps: Aluminum foil surface pretreatment: Place the aluminum foil in an alkaline cleaning solution for 10-120 seconds to remove surface oil and natural oxide layer, and then rinse it with deionized water. Molecular template preparation: The pretreated aluminum foil is immersed in a molecular self-assembly solution and reacted at 20-80℃ for 1-48 hours to form a self-assembled monolayer on the aluminum foil surface. A patterned template of 10-200 nm is created on the self-assembled monolayer by nanoimprinting or photolithography. Resonance frequency determination: The inherent mechanical resonance frequency fr of the aluminum foil was determined using vibration testing equipment; First-stage gradient etching: An aluminum foil with a patterned template is placed in a first-stage etching solution containing 0.3-5 wt% citric acid and 0.05-8 wt% hydrochloric acid, with a pH of 1.5-4.0. An AC voltage with a frequency of f1 and an amplitude of 1-4V is applied at a temperature of 30-60℃ for 20-120 seconds. The relationship between f1 and the inherent resonant frequency fr of the aluminum foil is: f1 = (0.4-0.8) × fr. Secondary gradient corrosion: The aluminum foil after primary corrosion is placed in a secondary corrosion solution containing 0.3-4 wt% oxalic acid and 0.02-9 wt% sulfuric acid, with a pH of 1.0-3.0. An AC voltage with a frequency of f2 and an amplitude of 2-5V is applied at a temperature of 40-70℃ for 15-90 seconds. The relationship between f2 and the inherent resonant frequency fr of the aluminum foil is: f2 = (0.8-1.2) × fr. Three-stage gradient corrosion: The aluminum foil after secondary corrosion is placed in a third-stage corrosion solution containing 0.08-7 wt% hydrochloric acid and 0.3-5 wt% citric acid, with a pH of 0.5-2.0; an AC voltage with a frequency of f3 and an amplitude of 3-6V is applied at a temperature of 50-80℃ for 15-90 seconds; the relationship between f3 and the inherent resonant frequency fr of the aluminum foil is: f3 = (1.5-2.5) × fr; Four-stage gradient corrosion: The aluminum foil after three-stage corrosion is placed in a fourth-stage corrosion solution, which contains 0.02-9 wt% sulfuric acid, 0.08-7 wt% hydrochloric acid, 0.3-4 wt% citric acid, and 0.3-5 wt% oxalic acid, with a pH value of 0.9-2.5; at a temperature of 40-70℃, an AC voltage with a frequency of f4 and an amplitude of 2-5V is applied, and the corrosion time is 15-90 seconds; wherein the relationship between f4 and the inherent resonant frequency fr of the aluminum foil is: f4 = (1.2-1.8) × fr; Five-stage refined etching: The aluminum foil after four-stage etching is placed in a fifth-stage etching solution, which contains 0.3-4 wt% citric acid and 0.01-0.5 wt% surfactant, with a pH value of 2.5-4.0; at a temperature of 30-60℃, an AC voltage with a frequency of f5 and an amplitude of 0.5-3V is applied, and the etching time is 10-60 seconds; wherein the relationship between f5 and the inherent resonant frequency fr of the aluminum foil is: f5 = (0.6-1.0) × fr; Template removal and cleaning: After etching, the aluminum foil is placed in a template removal solution to remove the molecular template, and then cleaned with deionized water; Heat treatment: Heat the cleaned porous aluminum foil at 100-350℃ for 10-120 minutes.

[0009] The method for preparing the nanoscale through-porous aluminum foil, wherein the molecular self-assembly solution is selected from at least one of the following: an alkyl thiol ethanol solution with a concentration of 0.1-10 mmol / L; a silane coupling agent toluene solution with a concentration of 0.1-5 vol%; or an organophosphate ethanol solution with a concentration of 0.05-2 mmol / L.

[0010] The method for preparing the nanoscale through-porous aluminum foil includes the following: the alkyl thiol is selected from at least one of n-dodecyl thiol, n-hexadecyl thiol, 11-mercaptoundecanoic acid, and 1-octane thiol; the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and vinyltriethoxysilane; and the organophosphate is selected from at least one of octadecylphosphonic acid and hexadecylphosphonic acid.

[0011] The method for preparing the nanoscale through-hole porous aluminum foil, wherein the method for determining the inherent mechanical resonance frequency fr is as follows: fix both ends of the aluminum foil, allow the middle part to vibrate freely, use a laser vibrometer or accelerometer to measure the vibration spectrum of the aluminum foil, and take the first-order resonance frequency as fr.

[0012] The method for preparing the nanoscale through-porous aluminum foil, wherein the template removal solution is selected from at least one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, hydrofluoric acid solution and organic solvent.

[0013] In the method for preparing the nanoscale through-porous aluminum foil, the organic solvent is selected from at least one of ethanol, acetone, and chloroform.

[0014] A nanoscale through-porous aluminum foil, wherein the nanoscale through-porous aluminum foil is prepared by the preparation method of the present invention.

[0015] Beneficial Effects: This invention achieves significant technical results in the structural control and performance improvement of porous aluminum foil through spatial guidance of molecular templates, energy focusing of resonant frequencies, and temporal synergy of multi-level gradient corrosion. Regarding the orderliness and uniformity of the pore structure, this invention forms a patterned template on the aluminum foil surface through molecular self-assembly and nanoimprint / photolithography, precisely pre-setting the corrosion initiation point in space and realizing the regular arrangement of pore positions. The introduction of resonant frequencies, by matching the mechanical vibration characteristics of the aluminum foil, generates local microflows and periodic stresses during the corrosion process, concentrating the corrosion process in the pre-set template exposure area and significantly suppressing the occurrence of random corrosion. The synergistic effect of these two factors jointly achieves precise control and highly uniform distribution of nanoscale pore size.

[0016] Regarding pore connectivity and structural integrity, the five-stage gradient corrosion strategy achieves programmable control of the corrosion process by employing targeted corrosion solution components (such as citric acid, oxalic acid, hydrochloric acid, and sulfuric acid) and AC voltage modulated based on resonant frequencies (f1 to f5) at different stages. Specifically, the first and second stages of corrosion focus on pore initiation and vertical deepening, the third and fourth stages are responsible for lateral pore enlargement and pore wall trimming, and the fifth stage completes fine cleaning. This staged, functionalized corrosion sequence, combined with the optimization of mass transfer and reaction interfaces by resonant vibration, effectively guides the longitudinal extension of the corrosion path and prevents premature pore closure or bottleneck formation, thereby successfully preparing porous structures with smooth pore walls and good connectivity.

[0017] In terms of comprehensive performance optimization, the aforementioned synergistic mechanism ensures the structural strength and flexibility of the material while achieving high porosity; the resonance effect promotes the discharge of corrosion products, avoids local blockage, and helps to form open channels with high porosity; at the same time, the fine control of gradient corrosion and the heat treatment process stabilize the microstructure of the pore wall, so that the porous aluminum foil can obtain a high specific surface area while maintaining good mechanical properties and fatigue resistance.

[0018] Furthermore, this invention significantly improves the controllability and repeatability of the process. By corroding the frequency with the inherent resonance characteristics of the aluminum foil, the process parameters can be adapted to aluminum foil substrates of different specifications, reducing batch variations. The multi-parameter collaborative design of gradient corrosion also provides a flexible means to precisely control the final pore structure (such as pore size, aspect ratio, and porosity), overcoming the shortcomings of traditional methods that are sensitive to process changes and produce random results.

[0019] In summary, this invention systematically solves the core problems of structural disorder, poor permeability, and difficulty in control in the preparation of nanoscale through-hole aluminum foil through a three-in-one technical solution of template positioning, resonance enhancement, and gradient deepening, and realizes precise and controllable preparation of structure from macroscopic arrangement to microscopic morphology. Attached Figure Description

[0020] Figure 1 This is a flowchart of a method for preparing a nanoscale through-hole porous aluminum foil according to the present invention.

[0021] Figure 2 This is an electron microscope image of the nanoscale through-porous aluminum foil prepared in Example 1 of the present invention.

[0022] Figure 3 This is an electron microscope image of the nanoscale through-porous aluminum foil prepared in Example 2 of the present invention.

[0023] Figure 4 This is an electron microscope image of the nanoscale through-porous aluminum foil prepared in Example 3 of the present invention.

[0024] Figure 5This is an electron microscope image of the nanoscale through-porous aluminum foil prepared in Comparative Example 1 of this invention.

[0025] Figure 6 This is an electron microscope image of the nanoscale through-porous aluminum foil prepared in Comparative Example 2 of this invention.

[0026] Figure 7 This is an electron microscope image of the nanoscale through-porous aluminum foil prepared in Comparative Example 3 of this invention.

[0027] Figure 8 This is an electron microscope image of the nanoscale through-porous aluminum foil prepared in Comparative Example 4 of this invention.

[0028] Figure 9 This is a transmission electron microscope image of the nanoscale through-porous aluminum foil prepared in Example 1 of the present invention.

[0029] Figure 10 This is a transmission electron microscope image of the nanoscale through-porous aluminum foil prepared in Comparative Example 1 of this invention. Detailed Implementation

[0030] This invention provides a nanoscale through-porous aluminum foil and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following examples provide further detailed description of the invention. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0031] Please see Figure 1 , Figure 1 The present invention provides a method for preparing nanoscale through-porous aluminum foil, which includes the following steps: S10. Aluminum foil surface pretreatment: Place the aluminum foil in an alkaline cleaning solution for 10-120 seconds to remove surface oil and natural oxide layer, and then rinse it with deionized water. In this step, industrial aluminum foil surfaces typically contain contaminants such as oil, dust, and processing aids, which hinder subsequent molecular self-assembly processes. Furthermore, aluminum rapidly forms a 2-5 nm thick layer of natural alumina in air; this chemically stable oxide layer impedes direct contact between self-assembly molecules and the aluminum substrate. This embodiment selects alkaline cleaning solutions such as sodium hydroxide or potassium hydroxide to remove surface oil and the natural oxide layer because aluminum is an amphoteric metal, soluble in both acids and alkalis. Under alkaline conditions, Al₂O₃ and Al undergo the following reaction: Al2O3 + 2OH - → 2AlO2 - + H₂O;2Al+2OH - + 6H₂O→2[Al(OH)₄] -+ 3H2↑; and alkaline solutions have a good saponification effect on oil stains: R-COO-R'+NaOH→R-COONa+R'-OH.

[0032] Cleaning time less than 10 seconds may not completely remove the oxide layer and oil stains; more than 120 seconds may lead to excessive corrosion of the aluminum substrate and increased surface roughness. An optimal cleaning time of 10-1200 seconds removes contaminants while maintaining a smooth surface. Finally, rinsing with deionized water removes residual alkali and reaction products, preventing contamination of subsequent steps. This step provides a clean canvas for the preparation of the S20 molecular template. Insufficient pretreatment prevents self-assembled molecules from forming an ordered monolayer on the aluminum surface, significantly reducing the subsequent spatial guidance effect.

[0033] S20. Molecular template preparation: The pretreated aluminum foil is immersed in a molecular self-assembly solution and reacted at 20-80℃ for 1-48 hours to form a self-assembled monolayer on the aluminum foil surface. A patterned template of 10-200nm is created on the self-assembled monolayer by nanoimprinting or photolithography. In this embodiment, a molecular layer with a specific pattern is formed on the surface of the aluminum foil as a blueprint for corrosion. The exposed area becomes the corrosion initiation point, while the covered area is protected. By controlling the corrosion initiation position, the initial position and arrangement of the pores can be precisely controlled. The self-assembled monolayer can also change the local surface properties, affecting the corrosion rate and direction.

[0034] In this embodiment, the molecular self-assembly solution is selected from at least one of the following: alkyl thiols with a concentration of 0.1-10 mmol / L; a silane coupling agent toluene solution with a concentration of 0.1-5 vol%; and an organophosphate ethanol solution with a concentration of 0.05-2 mmol / L. Specifically, the sulfur atom in the alkyl thiols forms a strong coordination bond with aluminum (Al-S bond energy approximately 200 kJ / mol), and intermolecular van der Waals forces cause the alkyl chains to arrange in an orderly manner; the siloxane alkyl group in the silane coupling agent reacts with the hydroxyl groups on the aluminum surface to form Si-O-Al covalent bonds; and the phosphate group in the organophosphate forms a stable coordination compound with aluminum. For example, the alkyl thiol is selected from at least one of n-dodecyl thiol, n-hexadecyl thiol, 11-mercaptoundecanoic acid, and 1-octane thiol; the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and vinyltriethoxysilane; the organophosphate is selected from at least one of octadecylphosphonic acid and hexadecylphosphonic acid, but is not limited thereto.

[0035] This embodiment utilizes nanoimprinting or photolithography to create patterned templates of 10-200 nm on self-assembled monolayers. Nanoimprinting offers low cost, high efficiency, and suitability for large-area manufacturing; photolithography provides high precision and flexible patterns, making it suitable for complex designs. The steps in this embodiment provide a spatially guiding template for the S40-S80 etching process, and the template pattern determines the geometric characteristics of the final pore structure.

[0036] S30. Resonance Frequency Measurement: The inherent mechanical resonance frequency fr of the aluminum foil is measured using vibration testing equipment. This embodiment measures the mechanical resonant frequency of the aluminum foil, which is the basis for utilizing the resonance effect. The resonant frequency of aluminum foil with different thicknesses, sizes, and clamping methods is different and needs to be measured separately. The AC frequency of the subsequent etching step is set based on the resonant frequency.

[0037] As an example, the method for determining the inherent mechanical resonant frequency *fr* is as follows: Fix both ends of the aluminum foil and allow the middle portion to vibrate freely. Measure the vibration spectrum of the aluminum foil using a laser vibrometer or an accelerometer, and take the first-order resonant frequency as *fr*. Vibration testing equipment selection: Laser vibrometer: non-contact, high precision (down to the nm level), does not affect the sample; Accelerometer: contact type, easy to install, low cost. For a typical 20μm thick aluminum foil with an effective length of 40mm, *fr* ≈ 130-150Hz. The *fr* measured in this embodiment is the reference for the frequency settings (f1-f5) in S40-S80, ensuring that the AC frequency matches the mechanical properties of the aluminum foil to achieve the resonance enhancement effect.

[0038] S40, First-stage gradient etching: The aluminum foil with a patterned template is placed in the first-stage etching solution, which contains 0.3-5 wt% citric acid and 0.05-8 wt% hydrochloric acid, with a pH value of 1.5-4.0; at a temperature of 30-60℃, an AC voltage with a frequency of f1 and an amplitude of 1-4V is applied, and the etching time is 20-120 seconds; wherein the relationship between f1 and the inherent resonant frequency fr of the aluminum foil is: f1=(0.4-0.8)×fr; The main function of this step is to initiate initial corrosion at the exposed sites of the template, forming seeds for nanoscale pores and preventing severe corrosion from destroying the guiding effect of the molecular template; at the same time, it provides initial channels for subsequent corrosion. In this embodiment, the corrosion solution consists of 0.3-5 wt% citric acid and 0.05-8 wt% hydrochloric acid. Citric acid, as a weak organic acid, has the following characteristics: corrosion inhibition: it forms a soluble complex [Al(C6H5O7)] with aluminum. 2+ Controls corrosion rate; pH buffering capacity: maintains solution pH stability; hydrochloric acid mainly provides H+. + To maintain an appropriate corrosion rate, the choice of high citric acid and low hydrochloric acid concentrations ensures gentle corrosion.

[0039] In this embodiment, the pH value is selected as 1.5-4.0. If the pH > 4.0, the corrosion rate is too slow and the efficiency is low; if the pH < 2.0, the corrosion is too fast and the template is damaged. In this embodiment, the step temperature is selected as 30-60℃. For every 10℃ increase in temperature, the reaction rate increases by about 2-3 times. The 30-60℃ range balances the reaction rate and control precision.

[0040] The electrical parameters for this embodiment are as follows: Frequency f1 = (0.4-0.8) × fr: lower than the resonant frequency, producing mild vibration. Its physical meaning is: sub-resonant state, with a small vibration amplitude. Its main function is to promote mass transfer rather than strong agitation; Voltage selection is 1-4V: a low voltage to control the corrosion rate. The peak value of AC voltage 1-4V is sufficient to drive corrosion but not excessive; Time selection is 20-120 seconds: sufficient to form initial pores but not to cause excessive corrosion.

[0041] In this embodiment, the electrochemical principle of corrosion is as follows: Under the action of alternating current, the corrosion process of aluminum includes the anodic half-reaction: Al → Al 3+ +3e - Cathode half-reaction: 2H + 2e - →H2↑;Overall reaction: 2Al + 6H + →2Al 3+ +3H2↑; The presence of citric acid alters the reaction pathway: Al 3+ +C6H8O7→ [Al(C6H5O7)] 2+ + 3H + This complexation reaction consumes Al 3+ This promotes further dissolution of aluminum while buffering pH.

[0042] In this embodiment, the area with the exposed molecular template has a faster corrosion rate because: the thiol-covered area is hydrophobic, which hinders the contact of the etchant; the thiol-aluminum interface has a high electron density, resulting in a positive shift in the corrosion potential; and the exposed area has no protective layer and is in direct contact with the etchant.

[0043] Synergy with resonant frequency: When f1 is set lower than fr, it produces mild vibrations, which have the following effects: promoting the diffusion of the corrosive agent to the corrosion front; preventing reaction products (H2 bubbles) from remaining on the surface; and not compromising the integrity of the molecular template.

[0044] S50, Secondary Gradient Corrosion: The aluminum foil after primary corrosion is placed in a secondary corrosion solution containing 0.3-4 wt% oxalic acid and 0.02-9 wt% sulfuric acid, with a pH of 1.0-3.0. An AC voltage with a frequency of f2 and an amplitude of 2-5V is applied at a temperature of 40-70℃ for 15-90 seconds. The relationship between f2 and the inherent resonant frequency fr of the aluminum foil is: f2 = (0.8-1.2) × fr. The main purpose of this step is to deepen the channel based on the initial hole, increase the depth-to-width ratio, promote longitudinal corrosion rather than lateral expansion, and ensure that the channel develops in the depth direction.

[0045] This step selects an etching solution containing 0.3-4 wt% oxalic acid and 0.02-9 wt% sulfuric acid. Oxalic acid, as a dibasic organic acid, is characterized by its affinity for Al. 3+ A soluble complex [Al(C2O4)3] is formed. 3- It promotes deep corrosion; oxalate ions are small and have strong diffusion ability, easily entering deep pores; it has a certain reducing property, preventing passivation of aluminum surfaces; sulfuric acid, as a strong acid, provides high conductivity and H+. + The advantage of using the two together is that oxalic acid promotes longitudinal corrosion, while sulfuric acid maintains an appropriate corrosion rate.

[0046] This step selects a pH value of 1.0-3.0, which is lower than that of the first-level corrosion to accelerate corrosion; however, it is still controlled within a certain range to avoid over-corrosion; the selected temperature is 40-70℃, which is slightly higher than that of the first level to increase the reaction rate, but does not exceed 70℃ to prevent boiling and violent reaction.

[0047] The electrical parameters selected in this step are: frequency f2=(0.8-1.2)×fr: close to the resonant frequency, with the largest vibration amplitude. Strong vibration generates microflow and stress concentration, promoting longitudinal corrosion; voltage of 2-5V: medium voltage, providing sufficient driving force; time of 15-90 seconds: appropriate time to achieve channel deepening.

[0048] In this embodiment, the initial pores formed in the first stage provide a channel for secondary corrosion, making it easier for oxalic acid to diffuse to the bottom of the pores and achieve selective longitudinal corrosion.

[0049] S60, Three-stage gradient corrosion: The aluminum foil after secondary corrosion is placed in a third-stage corrosion solution, which contains 0.08-7 wt% hydrochloric acid and 0.3-5 wt% citric acid, with a pH value of 0.5-2.0; at a temperature of 50-80℃, an AC voltage with a frequency of f3 and an amplitude of 3-6V is applied, and the corrosion time is 15-90 seconds; wherein the relationship between f3 and the inherent resonant frequency fr of the aluminum foil is: f3 = (1.5-2.5) × fr; The main purpose of this step is to: enlarge the aperture to prevent the channel from becoming too deep and closing up; and to correct narrow areas in the channel to make the diameter of the channel more consistent.

[0050] This step uses a corrosion solution consisting of 0.08-7 wt% hydrochloric acid and 0.3-5 wt% citric acid. Hydrochloric acid, as a strong acid, is characterized by its rapid corrosion rate and high Cl content. - Small ionic radius, strong permeability; reacts violently with aluminum: 2Al + 6HCl → 2AlCl3 + 3H2↑; Cl - It destroys the passivation film of aluminum; citric acid can buffer the severe corrosion of hydrochloric acid and prevent over-corrosion; when the two are combined, hydrochloric acid provides rapid lateral corrosion, while citric acid controls the uniformity of corrosion.

[0051] This step uses a pH value of 0.5-2.0, which is strongly acidic and promotes rapid corrosion. If the pH is less than 0.5, the corrosion may be too fast and difficult to control. The temperature is set at 50-80℃. Higher temperatures accelerate the corrosion reaction, but the temperature should not exceed 80℃ to prevent the solution from boiling.

[0052] The electrical parameters selected in this step are: frequency f3 = (1.5-2.5) × fr: at this point, the frequency is higher than the resonant frequency, and the state is in super-resonance. The vibration modes are complex, including: bending vibration: promoting lateral material transport; torsional vibration: generating shear force to remove deposits on the hole wall; combined vibration: multiple modes are superimposed to achieve all-round hole enlargement; voltage is 3-6V: a relatively high voltage to provide strong driving force; time is 15-90 seconds: to control the degree of hole enlargement.

[0053] In this embodiment, the deep hole formed in the second stage provides a framework for the third stage of hole enlargement. Hydrochloric acid corrodes from the hole wall inward, achieving lateral expansion. Without the vertical deepening in the second stage, the third stage of hole enlargement may only occur on the surface.

[0054] S70, Quadruple Gradient Corrosion: The aluminum foil after tertiary corrosion is placed in a quaternary corrosion solution containing 0.02-9 wt% sulfuric acid, 0.08-7 wt% hydrochloric acid, 0.3-4 wt% citric acid, and 0.3-5 wt% oxalic acid, with a pH of 0.9-2.5. An AC voltage with a frequency of f4 and an amplitude of 2-5V is applied at a temperature of 40-70℃ for 15-90 seconds. The relationship between f4 and the inherent resonant frequency fr of the aluminum foil is: f4 = (1.2-1.8) × fr. The main functions of this step are: to make the shape of the channel more regular, eliminate irregular protrusions and depressions; improve the quality of the hole wall and reduce surface defects; eliminate the internal stress generated during the corrosion process; and balance the degree of corrosion in each area to improve uniformity.

[0055] The etching solution used in this step consists of 0.02-9 wt% sulfuric acid, 0.08-7 wt% hydrochloric acid, 0.3-4 wt% citric acid, and 0.3-5 wt% oxalic acid. These four acids work synergistically: sulfuric acid maintains conductivity and acidity; hydrochloric acid continues to slightly expand the pores; citric acid buffers and complexes, controlling the etching rate; and oxalic acid deepens and refines the pores. Different acids play different roles, achieving comprehensive finishing.

[0056] This step selects a pH value of 0.9-2.5, which is moderately acidic, allowing for trimming without excessive corrosion; and a Xunze temperature of 40-70℃: a moderate temperature that balances the reaction rate and ensures precise control. The electrical parameters selected for this step are: frequency f4 = (1.2-1.8) × fr: slightly higher than the resonant frequency, a gentle super-resonance state, producing moderate vibration, sufficient for trimming but not excessive; voltage 2-5V: medium voltage; time 15-90 seconds: sufficient to complete the trimming.

[0057] In this embodiment, the first three stages form the basic hole structure, but defects and irregularities may exist. The fourth stage of etching performs finishing to improve the quality of the hole; without the fourth stage of finishing, the hole may have bottlenecks, roughness, and other problems.

[0058] S80, Level 5 Refined Corrosion: The aluminum foil after Level 4 corrosion is placed in the Level 5 corrosion solution, which contains 0.3-4 wt% citric acid and 0.01-0.5 wt% surfactant, with a pH value of 2.5-4.0; at a temperature of 30-60℃, an AC voltage with a frequency of f5 and a voltage amplitude of 0.5-3V is applied, and the corrosion time is 10-60 seconds; wherein the relationship between f5 and the inherent resonant frequency fr of the aluminum foil is: f5 = (0.6-1.0) × fr; The main functions of this step are: to remove corrosion products and impurities; to further improve the smoothness of the hole walls; to slightly corrode any remaining template material; and to improve surface properties in preparation for subsequent processing or application.

[0059] The etching solution selected in this step consists of 0.3-4 wt% citric acid and 0.01-0.5 wt% surfactant. The low concentration of citric acid is a mild acid that gently corrodes and cleans the surface. The surfactant (such as sodium dodecylbenzene sulfonate) can reduce surface tension, improve wettability, emulsify, remove oily residues, and prevent the redeposition of impurities.

[0060] This step uses a pH value of 2.5-4.0, which is relatively mild and mainly serves a cleaning function rather than strong corrosion; the temperature is selected as 30-60℃, which is a moderate temperature and promotes the action of surfactants.

[0061] The electrical parameters selected for this step are as follows: Frequency f5 = (0.6-1.0) × fr: close to or slightly below the resonant frequency, gentle vibration, assisting cleaning, not causing strong corrosion, mainly used for mass transfer; Voltage 0.5-3V: low voltage, small current; Time 10-60 seconds: short time, cleaning can be completed.

[0062] In this embodiment, the fifth-level corrosion is the final step in the corrosion process. Its mild nature ensures that the formed pore structure is not damaged, while improving surface quality. It prepares the surface for subsequent S90 template removal and S100 heat treatment.

[0063] S90, Template Removal and Cleaning: After etching, the aluminum foil is placed in template removal solution to remove the molecular template, and then cleaned with deionized water; The main purpose of this step is to: eliminate organic residues to obtain a clean aluminum surface; remove any residual corrosion liquid and reaction products; and provide a clean surface for heat treatment or functionalization.

[0064] The template removal solution is selected from at least one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, hydrofluoric acid solution and organic solvent, wherein the organic solvent is selected from at least one of ethanol, acetone and chloroform, but is not limited thereto.

[0065] For example, for thiol templates: the template removal solution can be an alkaline solution (NaOH / KOH), and the reaction is: RS-Al + OH- - →RS - +AlO2 - +H2O For silane templates: the template removal solution can be buffered hydrofluoric acid, and the reaction is: Si-O-Al + HF → SiF4 + AlF3 + H2O; For phosphate templates: the template removal solution can be either acidic or alkaline.

[0066] In this embodiment, after the etching is completed, the template has fulfilled its guiding mission and needs to be removed to obtain pure porous aluminum foil. Cleaning ensures that there are no chemical residues, creating conditions for heat treatment.

[0067] S100, Heat treatment: Heat the cleaned porous aluminum foil at 100-350℃ for 10-120 minutes.

[0068] The main functions of this step are: to eliminate residual stress that may be generated during the corrosion process; to stabilize the pore structure, allowing the atoms on the pore walls to rearrange and making the structure more stable; to remove adsorbed substances, removing water and gas adsorbed on the surface; to improve mechanical properties, which may involve recovery and recrystallization, thus increasing strength; and to form a protective oxide layer: a dense Al2O3 layer is formed on the surface, improving corrosion resistance.

[0069] Heat treatment, as the final step in the preparation of porous aluminum foil, locks in the pore structure, improves material stability, and prepares the material for practical applications.

[0070] The core of this invention lies in the organic combination of molecular self-assembly technology, mechanical resonance principle, and gradient corrosion strategy to form a synergistic effect and achieve precise control of the corrosion process. Its core principle is based on the following three core mechanisms: Firstly, the spatial guidance mechanism of molecular templates: This invention constructs a self-assembled monolayer (SAM) on the surface of aluminum foil. Through intermolecular forces (such as thiol-aluminum coordination bonds, silane-aluminum covalent bonds, and phosphate-aluminum coordination bonds), an ordered molecular array is formed on the aluminum surface. These molecules form nanoscale chemical patterns on the aluminum surface, altering the local surface energy, electron density, and chemical reactivity. Specific patterns are created on the SAM using nanoimprinting or photolithography techniques, allowing the removal or modification of SAM molecules in certain areas, exposing the underlying aluminum matrix. During electrochemical corrosion, the exposed areas become preferential corrosion sites, while the SAM-covered areas are protected, thereby achieving spatially selective control of the corrosion location. Molecular templates not only determine the initial location of pores but also influence the direction of corrosion propagation through the orientation of molecular arrangement. Secondly, there's the energy focusing mechanism of resonant frequencies: aluminum foil, as an elastic body, possesses inherent mechanical vibration characteristics. When an alternating electric field is applied, the aluminum foil undergoes forced vibration under the influence of the electric field force and its own inertial force. When the alternating current frequency matches the inherent mechanical resonant frequency of the aluminum foil, resonance occurs, and the vibration amplitude significantly increases. Resonant vibration produces two key effects: first, it forms local microflows, enhancing the transport of corrosive agents to the corrosion front and the diffusion of reaction products into the bulk solution, preventing pore blockage caused by product accumulation; second, it generates energy focusing in stress concentration areas (such as pore tips and defects). The invention generates periodic stresses, promoting preferential corrosion in these areas and making the corrosion process more directional. By precisely controlling the relationship between the AC frequency and the aluminum foil resonant frequency, the resonance intensity can be adjusted, thereby controlling the uniformity and directionality of corrosion. Thirdly, the spatiotemporal synergistic mechanism of gradient corrosion: The corrosion process provided by this invention is not a simple superposition of a single mechanism, but a synergistic effect of multiple mechanisms at different spatiotemporal scales. This invention designs a five-level gradient corrosion strategy, each level having a specific functional positioning: Level 1 corrosion (pore-opening stage): mainly using citric acid, mild corrosion, forming initial nanopores at the exposed position of the template, establishing corrosion channels; Level 2 corrosion (deepening stage): mainly using oxalic acid, promoting longitudinal corrosion, deepening the corrosion. The process involves three stages of corrosion: Level 1 (hole enlargement stage): primarily using hydrochloric acid to accelerate lateral corrosion, enlarge the pore diameter, and prevent premature pore closure; Level 2 (hole finishing stage): balancing multiple acids to refine the pore shape, improve pore wall smoothness, and eliminate local defects; Level 3 (refining stage): using low-concentration acid and surfactants to clean the pores and remove residual impurities. The frequency settings for each corrosion stage are also matched to the corrosion function: Levels 1 and 5 use excitation below the resonant frequency to generate gentle vibrations suitable for fine control; Level 2 uses excitation close to the resonant frequency to generate moderate vibrations and promote etchant transport; Levels 3 and 4 use excitation above the resonant frequency to generate stronger vibrations and accelerate the corrosion process.

[0071] The present invention will be further explained and illustrated below through specific embodiments: Example 1 A method for preparing nanoscale through-porous aluminum foil based on a hexadecylthiol template, comprising the following steps: 1. Material preparation Aluminum foil: 1070 industrial pure aluminum, thickness 20μm, width 100mm, length 200mm, aluminum content ≥99.7%; Chemical reagents: Sodium hydroxide (analytical grade), n-hexadecyl mercaptan (96%), anhydrous ethanol (analytical grade), citric acid (food grade), hydrochloric acid (36-38%), oxalic acid (analytical grade), sulfuric acid (98%), sodium dodecylbenzenesulfonate; 2. Aluminum foil surface pretreatment Cut aluminum foil into 50mm×50mm samples; prepare a 1.5wt% sodium hydroxide aqueous solution and heat it to 50℃; immerse the aluminum foil in the sodium hydroxide solution and ultrasonically clean it for 60 seconds; remove the aluminum foil and rinse it with deionized water 3 times, 30 seconds each time; dry the surface of the aluminum foil with high-purity nitrogen gas.

[0072] 3. Preparation of molecular templates Prepare an ethanol solution of 1.0 mmol / L n-hexadecyl mercaptan and dissolve it by sonication; The pretreated aluminum foil was immersed in a mercaptan solution and reacted in a 50°C constant temperature water bath for 18 hours. Remove the aluminum foil and rinse it with ethanol to remove the physically adsorbed thiol molecules; The thiol layer was imprinted using a nanoimprint apparatus with a silicon template (50 nm pore size, 100 nm pore spacing, hexagonal arrangement); Imprinting conditions: pressure 5MPa, temperature 80℃, time 5 minutes; After imprinting, rinse lightly with ethanol to remove thiol molecules from the crushed areas.

[0073] 4. Resonance frequency measurement Fix the two ends of the aluminum foil sample with the template with clamps, with an effective vibration length of 40mm; The vibration spectrum of aluminum foil was determined using a Polytec PSV-500 laser vibrometer via a random excitation method. Test conditions: Frequency range 10-1000Hz, resolution 0.5Hz; The first-order natural resonant frequency fr was measured to be 132 Hz.

[0074] 5. Preparation of corrosive solution First-stage corrosion solution: 4.5 wt% citric acid, 0.8 wt% hydrochloric acid, prepared with deionized water, pH=2.9; Second-stage corrosion solution: 3.2 wt% oxalic acid, 2.5 wt% sulfuric acid, prepared with deionized water, pH=2.1; The third-stage corrosion solution consists of 5.8 wt% hydrochloric acid and 2.2 wt% citric acid, prepared with deionized water, pH=1.4. Fourth-level corrosive solution: sulfuric acid 2.5wt%, hydrochloric acid 2.5wt%, citric acid 2.0wt%, oxalic acid 2.0wt%, prepared with deionized water, pH=1.9; Fifth-stage corrosion solution: 0.8 wt% citric acid, 0.08 wt% sodium dodecylbenzenesulfonate, prepared with deionized water, pH=3.3.

[0075] 6. Five-level gradient corrosion The corrosion apparatus is a self-made five-tank continuous corrosion system, with each corrosion tank having a volume of 2L, and equipped with a constant temperature circulating water bath, mechanical stirring, and titanium mesh counter electrode.

[0076] First-level corrosion: Heat the corrosive solution to 45°C and maintain the temperature; turn on the stirrer at 200 rpm. An aluminum foil sample was used as the working electrode, and a titanium mesh was used as the counter electrode. An AC voltage was applied. Voltage parameters: Sine wave, frequency f1 = 0.6 × fr = 79 Hz (approximately 80 Hz), voltage amplitude 2.2 V; corrosion time: 70 seconds; During the corrosion process, uniform bubbles were observed to appear on the surface of the aluminum foil.

[0077] Second-level corrosion: The aluminum foil after primary etching is quickly transferred to the secondary etching tank; The temperature of the corrosive solution is 50℃; the stirring speed is 250 rpm. Voltage parameters: Sine wave, frequency f2=1.0×fr=132Hz, voltage amplitude 3.5V; corrosion time: 45 seconds; An increase in bubble production was observed, and the transparency of the aluminum foil slightly improved.

[0078] Third-level corrosion: The aluminum foil after secondary etching is transferred to the tertiary etching tank; the etching solution temperature is 60℃; the stirring speed is 300rpm. Voltage parameters: Sine wave, frequency f3=2.0×fr=264Hz, voltage amplitude 4.5V; corrosion time: 35 seconds; Vigorous bubble formation was observed, and the transparency of the aluminum foil was significantly improved.

[0079] Fourth level corrosion: The aluminum foil after the third-stage etching was transferred to the fourth-stage etching tank; the etching solution temperature was 50℃; the stirring speed was 250rpm. Voltage parameters: Sine wave, frequency f4=1.5×fr=198Hz, voltage amplitude 3.2V; corrosion time: 30 seconds; The formation of bubbles tends to become more gradual.

[0080] Fifth level corrosion: The aluminum foil after the fourth-stage etching was transferred to the fifth-stage etching tank; the etching solution temperature was 40℃; the stirring speed was 150rpm. Voltage parameters: sine wave, frequency f5=0.8×fr=106Hz, voltage amplitude 1.5V; corrosion time: 25 seconds; Almost no bubbles were produced.

[0081] 7. Template Removal and Cleaning Prepare a 0.8 wt% sodium hydroxide aqueous solution at room temperature; immerse the etched aluminum foil in the sodium hydroxide solution for 5 minutes to remove the thiol template; remove the aluminum foil and rinse it 5 times with deionized water; dehydrate it with anhydrous ethanol and dry it with high-purity nitrogen.

[0082] 8. Heat treatment Aluminum foil was placed in a muffle furnace; under nitrogen protection, the temperature was increased to 220°C at 5°C / min; the temperature was held for 30 minutes; and the foil was cooled to room temperature with the furnace to obtain nanoscale through-porous aluminum foil.

[0083] Example 2 A method for preparing nanoscale through-porous aluminum foil based on APTES silane template, comprising the following steps: 1. Material preparation Aluminum foil: 1090 industrial pure aluminum, 15μm thick, aluminum content ≥99.9% New reagents: 3-aminopropyltriethoxysilane (APTES, 99%), toluene (analytical grade), hydrofluoric acid (40%), acetic acid (analytical grade); 2. Aluminum foil surface pretreatment Plasma cleaning is used instead of alkaline cleaning: Place the aluminum foil in a plasma cleaner, introduce argon gas, power 150W, cleaning time 3 minutes; rinse with deionized water and dry with nitrogen.

[0084] 3. Preparation of molecular templates Prepare a 2.0 vol% APTES toluene solution; immerse aluminum foil in the APTES solution and react at room temperature for 24 hours; remove the aluminum foil, rinse with toluene, and dry with nitrogen; use electron beam lithography to create a dual-scale pattern on the silane layer: the primary pattern consists of dots with a diameter of 80 nm, a spacing of 150 nm, and a hexagonal arrangement; the secondary pattern consists of dots with a diameter of 400 nm, a spacing of 800 nm, distributed at the vertices of the hexagonal arrangement.

[0085] 4. Resonance frequency measurement Same as in Example 1, the natural resonant frequency fr was measured to be 185 Hz.

[0086] 5. Preparation of corrosive solution First-stage corrosion solution: 5.0 wt% citric acid, 0.5 wt% hydrochloric acid, pH=3.1; Second-stage corrosion solution: 4.0 wt% oxalic acid, 3.0 wt% sulfuric acid, pH=2.0; Third-stage corrosion solution: hydrochloric acid 7.0 wt%, citric acid 1.5 wt%, pH=1.2; Fourth-level corrosive solution: sulfuric acid 3.0 wt%, hydrochloric acid 3.0 wt%, citric acid 1.8 wt%, oxalic acid 1.8 wt%, pH=1.8; Fifth-stage corrosion solution: 1.2 wt% citric acid, 0.12 wt% sodium dodecylbenzenesulfonate, pH=3.1.

[0087] 6. Five-level gradient corrosion First-stage corrosion: Temperature 42℃, f1 = 0.5×fr = 93Hz, Voltage 2.0V, Time 65 seconds; Second-stage corrosion: Temperature 48℃, f2 = 0.9×fr = 167Hz, Voltage 3.2V, Time 40 seconds; Third-stage corrosion: Temperature 58℃, f3 = 2.2×fr = 407Hz, Voltage 4.8V, Time 30 seconds; Fourth-stage corrosion: Temperature 48℃, f4 = 1.6×fr = 296Hz, Voltage 3.5V, Time 25 seconds; Fifth-stage corrosion: Temperature 38℃, f5 = 0.7×fr = 130Hz, Voltage 1.2V, Time 20 seconds. 7. Template Removal The silane template was removed using a buffered hydrofluoric acid solution: 0.5wt% HF + 2.0wt% NH4F, pH=5.2; soaking time 8 minutes; and thorough rinsing with deionized water.

[0088] 8. Heat treatment Nanoscale through-porous aluminum foil was obtained by heat treatment at 250℃ for 20 minutes under nitrogen protection.

[0089] Example 3 A method for preparing nanoscale through-porous aluminum foil based on octadecylphosphonic acid template, comprising the following steps: 1. Material preparation Aluminum foil: 1050 industrial pure aluminum, 25μm thickness, aluminum content ≥99.5% New reagents: Octadecylphosphonic acid (95%), 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES, 97%). 2. Aluminum foil surface pretreatment Clean with 1.0wt% NaOH solution at 60℃ for 40 seconds using ultrasonic cleaning; rinse with deionized water and dry with nitrogen.

[0090] 3. Preparation of molecular templates Prepare an ethanol solution of 0.5 mmol / L octadecylphosphonic acid; immerse aluminum foil in the solution and react at 70°C for 8 hours; nanoimprinting: silicon template with pore size of 30 nm, spacing of 80 nm, square arrangement; imprinting conditions: 6 MPa, 85°C, 4 minutes.

[0091] 4. Resonance frequency measurement The laser vibration meter measured fr=108Hz (the frequency is lower for thicker aluminum foil).

[0092] 5. Preparation of corrosive solution First-stage corrosion solution: 2.5 wt% citric acid, 1.0 wt% hydrochloric acid, pH=2.7; Second-stage corrosion solution: oxalic acid 3.5wt%, sulfuric acid 2.0wt%, pH=2.2; Third-stage corrosion solution: hydrochloric acid 4.5wt%, citric acid 2.5wt%, pH=1.5; Fourth-level corrosive solution: sulfuric acid 2.0 wt%, hydrochloric acid 2.0 wt%, citric acid 2.5 wt%, oxalic acid 1.5 wt%, pH=2.0; Fifth-stage corrosion solution: 0.5 wt% citric acid, 0.05 wt% sodium dodecylbenzenesulfonate, pH=3.5.

[0093] 6. Five-level gradient corrosion First-stage corrosion: Temperature 48℃, f1 = 0.7×fr = 76Hz, Voltage 2.5V, Time 75 seconds; Second-stage corrosion: Temperature 52℃, f2 = 1.1×fr = 119Hz, Voltage 3.8V, Time 50 seconds; Third-stage corrosion: Temperature 62℃, f3 = 1.8×fr = 194Hz, Voltage 5.0V, Time 40 seconds; Fourth-stage corrosion: Temperature 52℃, f4 = 1.3×fr = 140Hz, Voltage 3.0V, Time 35 seconds; Fifth-stage corrosion: Temperature 42℃, f5 = 0.9×fr = 97Hz, Voltage 1.8V, Time 30 seconds. 7. Template Removal Soak in 0.5wt% NaOH solution at room temperature for 6 minutes; rinse thoroughly with deionized water.

[0094] 8. Heat treatment Nanoscale through-porous aluminum foil was obtained by heat treatment at 180°C for 40 minutes in air atmosphere.

[0095] Comparative Example 1 (Traditional Electrochemical Corrosion Method) A method for preparing porous aluminum foil, the preparation steps of which differ from those in Example 1 are as follows: no molecular template is applied, and the resonance frequency is not measured; the etching solution is a single hydrochloric acid solution (5.0 wt%); the power supply is a DC constant voltage, voltage 5.0 V; the etching process is single-stage etching, time 180 seconds; the temperature is 60 °C; the post-treatment is deionized water rinsing and heat treatment at 150 °C for 30 minutes.

[0096] Comparative Example 2 (Resonance Etching without Molecular Template) A method for preparing porous aluminum foil, the preparation steps of which differ from those of Example 1 are: no molecular template is applied; the remaining steps are the same as those of Example 1.

[0097] Comparative Example 3 (with molecular template but no resonance frequency modulation) A method for preparing porous aluminum foil differs from Example 1 in that: the resonant frequency is not measured, and a fixed frequency AC current is used; the corrosion frequency is a fixed frequency of 100Hz; the remaining steps are the same as in Example 1.

[0098] Comparative Example 4 (with molecular template and resonance frequency but no gradient corrosion) A method for preparing porous aluminum foil, the preparation steps of which differ from those in Example 1 are as follows: the etching solution used is a single composite acid solution (citric acid 3%, hydrochloric acid 2%, sulfuric acid 1%, oxalic acid 1%, pH=2.0); the frequency setting is f=1.0×fr=132Hz for all; single-stage etching is performed at a voltage of 3.5V, a time of 200 seconds, and a temperature of 50℃.

[0099] Comprehensive performance tests were performed on all samples prepared in Examples 1-3 and Comparative Examples 1-4. The pore structure was characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 2-8 And as shown in Table 1.

[0100] Table 1. Pore structure characterization results

[0101] from Figure 2-8 As can be seen from the results in Table 1, Examples 1-3 exhibited excellent pore size control capabilities, with pore size variation coefficients of only 11.5-14.3%, which are much lower than those of Comparative Examples 1-4 (33.3-56.7%). This indicates that the synergistic effect of molecular template and resonance frequency modulation significantly improved pore size uniformity. The pores in Examples 1 and 3 are highly ordered, which is direct evidence of the spatial guidance effect of the molecular template. The pores in Comparative Example 2 (without template) and Comparative Example 4 (without gradient corrosion) are randomly distributed. Example 2 successfully achieved a dual-scale pore structure, with primary nanopores (85 nm) and secondary buffer pores (420 nm) coexisting. This multi-level pore structure is difficult to achieve in traditional methods. The pore size variation coefficient of Comparative Example 1 (traditional method) is as high as 56.7%, indicating that the randomness of traditional electrochemical corrosion is extremely strong. The pore size uniformity of Comparative Example 3 (with template but no resonance) is improved compared with Comparative Example 2 (without template but with resonance), but not as good as Example 1, indicating that both template and resonance are indispensable.

[0102] The samples of Example 1 and Comparative Example 1 were observed using a transmission electron microscope (TEM), and the results are as follows: Figure 9 and Figure 10 As shown in the figure, the channel of Example 1 extends from the surface to the bottom, is continuous without interruption, and has a uniform wall thickness; the channel of Comparative Example 1 is mostly blind, with only about 30% of the channel extending through, and the channel is irregular with a large number of bottleneck structures.

[0103] Porosity tests were performed on samples from Examples 1-3 and Comparative Examples 1-4 using the mercury porosimetry method. The results are shown in Table 2. Table 2 Porosity test results

[0104] As can be seen from the data in Table 2, the porosity of Examples 1-3 reached 49.8-54.2%, which was significantly higher than that of Comparative Examples 1-4 (38.6-48.7%). High porosity means a larger active area, which is beneficial to improving the functional performance of the material. The porosity of Comparative Examples 2 and 3 was between that of Examples and Comparative Example 1, indicating that the template, resonance, and gradient corrosion each contributed to improving the porosity, and the synergistic effect of the three was the best.

[0105] Mechanical properties were tested on the samples from Examples 1-3 and Comparative Examples 1-4, and the results are shown in Table 3.

[0106] Table 3 Mechanical Performance Test Results

[0107] As can be seen from the data in Table 3, Comparative Example 1 (traditional method) has the highest tensile strength (92.5 MPa), but this comes at the cost of low porosity (38.6%). Example 1 maintains a tensile strength of 71.5 MPa even with a porosity of 54.2%, demonstrating superior overall strength-porosity performance. Examples 1-3 all exceeded 100 bending cycles, while Comparative Examples 2-4 did not reach 100 cycles, indicating that the porous aluminum foil prepared by this invention has better flexibility and fatigue resistance. Example 2 has the highest tensile strength (76.8 MPa), which may be related to the stress dispersion effect of the dual-scale pore structure. Comparative Example 4 (without gradient corrosion) has the worst mechanical properties, indicating that gradient corrosion is beneficial for forming a pore structure with uniform structure and low stress concentration.

[0108] In summary, the core innovation of this invention lies in the synergy of template, resonance, and gradient, rather than a simple addition. This synergistic effect is manifested in: spatial-energy synergy: the molecular template provides spatial positioning (where to corrode), and the resonance frequency provides energy focusing (how to corrode efficiently), the combination of the two achieves precise and efficient corrosion; temporal-spatial synergy: gradient corrosion provides optimization strategies in the temporal dimension (different methods at different stages), combined with the spatial control of the molecular template, to achieve a multidimensionally controllable corrosion process; chemical-physical synergy: the chemical composition of the corrosive solution regulates the corrosion reaction, and the physical effect of resonance vibration regulates mass transfer and interfacial processes, the combination of the two achieves comprehensive optimization of the corrosion process. Experimental data fully demonstrate this synergistic effect: the performance indicators of Example 1 (synergistic effect of the three) are significantly better than any single or two-factor comparative examples. It is particularly noteworthy that the performance of Comparative Example 2 (no template) and Comparative Example 3 (no resonance) is significantly better than that of Comparative Example 1 (traditional method), but not as good as Example 1, and there is no significant difference between the two (p>0.05), indicating that the template and resonance have similar contribution weights and there is a synergistic rather than a simple additive relationship. It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing nanoscale through-porous aluminum foil, characterized in that, Including the following steps: Aluminum foil surface pretreatment: Place the aluminum foil in an alkaline cleaning solution for 10-120 seconds to remove surface oil and natural oxide layer, and then rinse it with deionized water. Molecular template preparation: The pretreated aluminum foil is immersed in a molecular self-assembly solution and reacted at 20-80℃ for 1-48 hours to form a self-assembled monolayer on the aluminum foil surface. A patterned template of 10-200 nm is created on the self-assembled monolayer by nanoimprinting or photolithography. Resonance frequency determination: The inherent mechanical resonance frequency fr of the aluminum foil was determined using vibration testing equipment; First-stage gradient etching: An aluminum foil with a patterned template is placed in a first-stage etching solution containing 0.3-5 wt% citric acid and 0.05-8 wt% hydrochloric acid, with a pH of 1.5-4.

0. An AC voltage with a frequency of f1 and an amplitude of 1-4V is applied at a temperature of 30-60℃ for 20-120 seconds. The relationship between f1 and the inherent resonant frequency fr of the aluminum foil is: f1 = (0.4-0.8) × fr. Secondary gradient corrosion: The aluminum foil after primary corrosion is placed in a secondary corrosion solution containing 0.3-4 wt% oxalic acid and 0.02-9 wt% sulfuric acid, with a pH of 1.0-3.

0. An AC voltage with a frequency of f2 and an amplitude of 2-5V is applied at a temperature of 40-70℃ for 15-90 seconds. The relationship between f2 and the inherent resonant frequency fr of the aluminum foil is: f2 = (0.8-1.2) × fr. Three-stage gradient corrosion: The aluminum foil after secondary corrosion is placed in a third-stage corrosion solution containing 0.08-7 wt% hydrochloric acid and 0.3-5 wt% citric acid, with a pH of 0.5-2.0; an AC voltage with a frequency of f3 and an amplitude of 3-6V is applied at a temperature of 50-80℃ for 15-90 seconds; the relationship between f3 and the inherent resonant frequency fr of the aluminum foil is: f3 = (1.5-2.5) × fr; Four-stage gradient corrosion: The aluminum foil after three-stage corrosion is placed in a fourth-stage corrosion solution, which contains 0.02-9 wt% sulfuric acid, 0.08-7 wt% hydrochloric acid, 0.3-4 wt% citric acid, and 0.3-5 wt% oxalic acid, with a pH value of 0.9-2.5; at a temperature of 40-70℃, an AC voltage with a frequency of f4 and an amplitude of 2-5V is applied, and the corrosion time is 15-90 seconds; wherein the relationship between f4 and the inherent resonant frequency fr of the aluminum foil is: f4 = (1.2-1.8) × fr; Five-stage refined etching: The aluminum foil after four-stage etching is placed in a fifth-stage etching solution, which contains 0.3-4 wt% citric acid and 0.01-0.5 wt% surfactant, with a pH value of 2.5-4.0; at a temperature of 30-60℃, an AC voltage with a frequency of f5 and an amplitude of 0.5-3V is applied, and the etching time is 10-60 seconds; wherein the relationship between f5 and the inherent resonant frequency fr of the aluminum foil is: f5 = (0.6-1.0) × fr; Template removal and cleaning: After etching, the aluminum foil is placed in a template removal solution to remove the molecular template, and then cleaned with deionized water; Heat treatment: Heat the cleaned porous aluminum foil at 100-350℃ for 10-120 minutes.

2. The method for preparing nanoscale through-porous aluminum foil according to claim 1, characterized in that, The molecular self-assembly solution is selected from at least one of the following: alkyl thiols with a concentration of 0.1-10 mmol / L; toluene solution of silane coupling agent with a concentration of 0.1-5 vol%; or ethanol solution of organophosphate with a concentration of 0.05-2 mmol / L.

3. The method for preparing nanoscale through-porous aluminum foil according to claim 2, characterized in that, The alkyl thiol is selected from at least one of dodecyl thiol, hexadecyl thiol, 11-mercaptoundecanoic acid, and 1-octane thiol; the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and vinyltriethoxysilane; the organophosphate is selected from at least one of octadecylphosphonic acid and hexadecylphosphonic acid.

4. The method for preparing nanoscale through-porous aluminum foil according to claim 1, characterized in that, The method for determining the inherent mechanical resonance frequency fr is as follows: fix both ends of the aluminum foil and let the middle part vibrate freely. Use a laser vibrometer or accelerometer to measure the vibration spectrum of the aluminum foil and take the first resonance frequency as fr.

5. The method for preparing nanoscale through-porous aluminum foil according to claim 1, characterized in that, The template removal solution is selected from at least one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, hydrofluoric acid solution, and organic solvent.

6. The method for preparing nanoscale through-porous aluminum foil according to claim 5, characterized in that, The organic solvent is selected from at least one of ethanol, acetone, and chloroform.

7. A nanoscale through-porous aluminum foil, characterized in that, It is prepared by the method described in any one of claims 1-6 for the preparation of nanoscale through-porous aluminum foil.

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