A DURABLE ACTIVE ANTI-ICING CONDUCTOR FOR USE IN A LOW-TEMPERATURE AND HIGH-HUMIDITY ENVIRONMENT, AND A METHOD FOR PREPARING THE SAME

Abstract

The present invention relates to the field of anti-icing material preparation, and in particular to a durable active anti-icing conductor for use in a low-temperature and high-humidity environment, and a method for preparing the same. The conductor comprises a dendritic composite porous structure formed on an aluminum substrate; the dendritic composite porous structure is configured to comprise an upper layer and a lower layer; a pore diameter of an upper pore in the upper layer is smaller than a pore diameter of a lower pore in the lower layer; a pore depth ratio of the upper pore to the lower pore is less than 1:2; both the upper pore and the lower pore are filled with a modifier and a lubricant.

Claims

1. An active anti-icing conductor for use in a low-temperature and high-humidity environment, wherein a surface ice adhesion strength of the active anti-icing conductor is not greater than 5 kPa; wherein the active anti-icing conductor is a dendritic composite porous structure formed on an aluminum substrate; the dendritic composite porous structure is configured to comprise an upper layer and a lower layer, wherein a total pore depth of the dendritic composite porous structure is 5-31 m; a pore diameter of an upper pore in the upper layer is smaller than a pore diameter of a lower pore in the lower layer, and a pore diameter ratio of the upper pore to the lower pore is 1:31:2; a pore depth ratio of the upper pore to the lower pore is less than 1:2; a ratio of number of the upper pore to number of the lower pore is 4-6:1; both the upper pore and the lower pore are filled with a modifier and a lubricant; a surface porosity of the dendritic composite porous structure is 50-66% with an inter-pore spacing of 10-38 nm.

2. The active anti-icing conductor according to claim 1, wherein the surface porosity of the dendritic composite porous structure is 66%.

3. (canceled)

4. (canceled)

5. The active anti-icing conductor according to claim 1, wherein the modifier is silane-ethanol.

6. A method for preparing the active anti-icing conductor according to claim 1, wherein the method comprises two anodization processes and one pore expansion process, comprising the following steps: (1) First anodization: placing a cleaned aluminum substrate in an H.sub.2C.sub.2O.sub.4 electrolyte, and applying an anodization current of 0.080.16 A/cm.sup.2 for 6-10 min to form an upper porous structure; (2) Second anodization: placing the product obtained in step (1) in an H.sub.3PO.sub.4 electrolyte, and applying an anodization current of 0.080.16 A/cm.sup.2 for 7-12 min to form a lower porous structure, wherein the lower porous structure forms while the upper porous structure dissolves, and a concentration of an aluminum ion is adjusted to 600-700 mg/L; (3) Pore expansion: immersing the formed two-layer porous product in an H.sub.3PO.sub.4 solution for 0-45 min to perform pore expansion, and washing and drying the resulting dendritic composite porous structure; (4) Filling with a modifier and a lubricant: filling the dendritic composite porous structure obtained in step (3) with a modifier using a vacuum infusion method to modify the dendritic composite porous structure, followed by filling with a lubricant, wherein the modifier is silane-ethanol.

7. The method according to claim 6, wherein a mass percentage of the silane-ethanol used in step (4) is 2 wt. %.

Description

DESCRIPTION OF DRAWINGS

[0025] To make the embodiments of the present invention or the technical solutions in the prior art clearer, the drawings required to be used in the description of the embodiments or the prior art will be briefly introduced below. It is obvious that the drawings described below are some embodiments of the present invention, and that other drawings can be obtained from these drawings for those of ordinary skill in the art without making inventive effort.

[0026] FIG. 1 is a scanning electron microscope (SEM) image of the dendritic composite porous structure of the present invention.

[0027] FIG. 2 shows the morphological characteristics of samples under different pore depth ratios (the pore depth ratio of upper pores to lower pores being (a) 1:0, (b) 2:1, (c) 1:1, (d) 1:2, (e) 1:3, and (f) 1:5, respectively).

[0028] FIG. 3 is a bar chart showing the initial amount of stored lubricant and the number of self-healing cycles under different pore depth ratios ((a) initial amount of lubricant; (b) number of self-healing cycles).

[0029] FIG. 4 is a curve showing the self-healing time under different pore depth ratios.

[0030] FIG. 5 shows the surface and cross-sectional morphology of porous structures with different porosity levels: [0031] (a) 37%, (b) 50%, (c) 66%, and (d) 72%.

[0032] FIG. 6 is an enlarged view of the porous structures with different porosity levels.

[0033] FIG. 7 shows the experimental results of initial lubricant amount and self-healing time under different porosity levels in a slow water droplet deposition experiment ((a) initial amount of lubricant; (b) self-healing time).

[0034] FIG. 8 shows the experimental results of CA, CHA, and surface morphology under different porosity levels in a slow water droplet deposition experiment ((a) contact angle (CA); (b) contact angle hysteresis (CHA); (c) surface morphology after 900 droplets deposition).

[0035] FIG. 9 is a graph showing the variation in ice adhesion strength with porosity.

[0036] FIG. 10 is a diagram showing the volume comparison of different porous structures under constant inter-pore spacing ((a) single-layer porous structure vs. simple composite porous structure; (b) single-layer porous structure vs. dendritic composite porous structure).

[0037] FIG. 11 shows the experimental results of frosting/defrosting cycles on the conventional single-layer porous surface and the dendritic porous surface ((a) effect of frosting/defrosting cycles on ice adhesion strength; (b) CA value during frosting/defrosting cycles; (c) effect of frosting/defrosting cycles on lubricant retention rate; (d) comparison of frost particle size between different porous structures).

[0038] FIG. 12 shows the experimental results of frosting/defrosting cycles on the conventional single-layer porous surface and the dendritic porous surface ((a) frosting time and state of different porous structures without frosting/defrosting cycles; (b) frosting time and state after 140 frosting/defrosting cycles).

[0039] FIG. 13 shows the surface morphology of dendritic composite porous structures formed under different aluminum ion concentrations.

[0040] FIG. 14 shows the surface morphology of dendritic composite porous structures formed under different anodization durations or current densities.

[0041] FIG. 15 shows the ice adhesion strength of samples under different anodization durations or current densities.

DETAILED DESCRIPTION

[0042] To make the objective, the technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in combination with drawings. It is obvious that the described embodiments are some of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making inventive effort shall belong to the protection scope of the present invention.

[0043] It should be noted that the term include, comprise or any variant thereof is intended to encompass nonexclusive inclusion so that a process, method, article or device including a series of elements includes not only those elements but also other elements which have been not listed definitely or an element(s) inherent to the process, method, article or device. Moreover, the expression comprising a(n) . . . in which an element is defined will not preclude presence of an additional identical element(s) in a process, method, article or device comprising the defined element(s) unless further defined.

[0044] As used herein, the term about, typically means +/5% of the stated value, more typically +/4% of the stated value, more typically +/3% of the stated value, more typically, +/2% of the stated value, even more typically +/1% of the stated value, and even more typically +/0.5% of the stated value.

[0045] Throughout this application, embodiments of this invention may be presented with reference to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc.; as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0046] As used in the present invention, the term active anti-icing conductor refers to a conductor capable of inhibiting ice formation from the initial stage of ice accretion or slowing the progression of ice accretion, which is primarily achieved through a surface ice adhesion strength that is lower than that of conventional anti-icing conductors (20 kPa).

[0047] As used in the present invention, the term porosity refers to the surface porosity of a cross-section, which is calculated as the ratio of the total area of the pores (Ap) to the total surface area (A), i.e.,

[00001]$P=\frac{.Math.A_P}{A}.$

[0048] As used in the present invention, the term inter-pore spacing refers to the distance between adjacent pores on a cross-section.

Embodiment 1

Preparation

Method for Preparing an Anti-Icing Conductor Comprising a Dendritic Composite Porous Structure

[0049] (1) An aluminum plate is cut into dimensions of 2.52.00.1 cm.sup.3, then cleaned with ethanol to remove surface contaminants. A 1 mol/L NaOH solution is used to remove the oxide on the aluminum surface, followed by rinsing with deionized water to remove residual alkali. A porous structure is formed on the clean sample surface via anodization, using the aluminum plate as the anode and a stainless steel plate as the cathode. A dendritic porous structure with a two-layer pore configuration is obtained through a two-step anodization process. In the first step, first anodization is performed in a 0.3 mol/L H.sub.2C.sub.2O.sub.4 electrolyte for 6-10 min to form the upper pores (also referred to as oxalic acid small pores). In the second step, second anodization is performed in 0.3 mol/L H.sub.3PO.sub.4 electrolyte for 7-12 min to form the lower pores (referred to as phosphoric acid large pores). In the third step, the resulting two-layer porous structure is immersed in 5 wt. % H.sub.3PO.sub.4 solution at 30 C. for 45 min for pore expansion. By adjusting the anodization current (0.080.16 A/cm.sup.2) and anodization duration, dendritic porous structures with different depth ratios, as well as different total pore depths, are obtained. Additionally, dendritic porous structures with different porosity levels are obtained by controlling either the aluminum ion concentration (600-1000 mg/L) or the duration of the pore expansion process (0-45 min). The prepared porous surface is then rinsed with ethanol and dried in an oven at 75 C. [0050] (2) The dendritic porous structure obtained in step (1) is immersed in a 2 wt. % silane-ethanol solution to modify the pores and enhance the surface affinity for the lubricant. To ensure that the nano-scale pores are completely filled with the modifier, a vacuum infusion method is used in the embodiment. Specifically, the prepared porous sample is placed in a vacuum chamber for 5 hours to remove air from the pores. The lubricant is then infused into the pore structure of a sample and maintained for 12 hours. The sample is taken out and excess lubricant is blown off the surface using compressed air. Finally, the lubricated surface is successfully prepared.

Method for Preparing an Anti-Icing Conductor Comprising a Conventional Single-Layer Porous Structure

[0051] (1) The aluminum plate is first anodized in a 0.3 mol/L H.sub.2C.sub.2O.sub.4 electrolyte, followed by pore expansion in a 5 wt. % H.sub.3PO.sub.4 solution at 30 C. [0052] (2) The single-layer porous structure is then filled with the modifier using procedures similar to step (2) in the preparation of an anti-icing conductor comprising a dendritic composite porous structure.

Embodiment 2

Characterization of the Dendritic Composite Porous Structure

Experiment for Determining the Optimal Pore Depth Ratio and Porosity

1. Characterization

[0053] The surface and cross-sectional morphology are characterized using a field-emission scanning electron microscope (SEM, Zeiss Auriga, Germany). The contact angle (CA) is measured using a contact angle goniometer (SINDIN, SDC-350, China), with a water droplet volume of 3 L. The droplet volume is then increased from 3 L to 6 L and subsequently decreased from 6 L to 3 L to measure the advancing and receding contact angles of the sample surface. The contact angle hysteresis (CAH) is calculated as the difference between the advancing and receding angles.

[0054] The initial amount of lubricant (m.sub.0) in the dendritic porous surface is determined by measuring the mass difference of the porous surface before and after lubricant infusion. To evaluate lubricant consumption, the sample is weighed periodically during frosting/defrosting and freezing/de-icing cycles to determine the remaining amount of lubricant (m.sub.i). The lubricant retention rate is calculated as (m.sub.i/m.sub.0)100%.

[0055] A droplet detachment experiment is used to investigate the lubricant consumption and self-healing performance of the dendritic composite porous surface. Water droplets are produced using a syringe connected to a peristaltic pump (Rongbai, BT100-2J, China), with the syringe needle positioned 1 cm above the sample. Water droplets of 8 L in volume are continuously deposited on the inclined sample surface (tilted at 30). During this process, the lubricant is gradually removed by the motion of the droplets resulting in lubricant consumption. To test the self-healing performance of the sample after lubricant consumption, droplets are deposited on the sample at a faster rate of 180 drops per minute. When the lubricant at the top of the pores is nearly consumed and the SLIPS loses its lubricating performance (defined as the standard for depletion of surface lubricant), the peristaltic pump is stopped. The sample is then left at room temperature until a new lubricant film formed on the porous surface, which is considered complete self-healing. The self-healing time is recorded. The droplet detachment experiment is repeated on the healed sample until the self-healing time exceeds 48 hours (i.e., the self-healing speed during 48h is investigated, assuming extreme weather typically lasts for 48 hours). To study the lubricant consumption rate on the dendritic porous surface, water droplets are deposited slowly on the inclined surface (at a rate of 30 drops per minute). Contact angle (CA), contact angle hysteresis (CAH), and microscopic images are measured and recorded at different time intervals.

[0056] Note: Self-healing of the anti-icing conductor does not occur after every single droplet is dropped to the conductor. In this experiment, it is observed that one self-healing event typically occurs after 180 droplets. Considering that in low-temperature environments, falling water droplets would likely freeze, this experiment is conducted at room temperature to serve as an accelerated test.

2. Results

2.1 Determination of the Optimal Pore Depth Ratio

2.1.1 Morphology

[0057] FIG. 2 shows the morphological characteristics of samples under different pore depth ratios.

2.1.2 Structural Parameters

[0058] This includes surface porosity, pore depth, as well as pore diameter and inter-pore spacing of a cross-section.

TABLE-US-00001 TABLE 1 Surface porosity and pore depth Conventional porous Pore depth ratio structure Dendritic composite porous structure (upper pores:lower pores, (I-shaped, I) (Y-shaped, Y) upper to lower) (1:0) 2:1 1:1 1:2 1:3 1:5 Surface Average pore size 114.9 10.8 118.9 13.3 117.3 13.4 116.6 14.9 117.1 16.6 115.6 12.5 (nm) Porosity (%) 66 67 67 66 67 66 Cross- Upper-layer pore 30.7 19.9 14.7 9.7 7.5 5.3 depth (m) section Lower-layer pore 10.9 15.5 21.0 22.6 25.5 depth (m) Total pore depth 30.7 30.8 30.2 30.7 30.1 30.8 (m)

TABLE-US-00002 TABLE 2 Pore diameter and inter-pore spacing of the cross-section Conventional porous structure Dendritic composite porous structure Pore depth ratio (I) (Y) (upper to lower) (1:0) 2:1 1:1 1:2 1:3 1:5 Cross- Upper- Average 85.8 80.6 78.0 83.8 78.5 75.8 section layer pore size (nm) Lower- Average 180.2 185.0 198.3 188.9 190.1 layer pore size (nm)

[0059] Conclusion: This embodiment successfully prepares dendritic porous structures with different pore depth ratios. As the structure satisfies the requirement that the total area of lower pores is greater than that of the upper pores (see FIG. 10), the dendritic porous structure has a larger volume than conventional single-layer porous structures and is capable of storing more lubricant.

[0060] When the pore depth ratio (upper to lower) of the dendritic porous structure is 1:2, the total pore depth is 9-31 m. Experimental results show that when the pore depth exceeds 31 m, the resistivity of the conductor increases beyond 0.1131 /km, which exceeds the limit defined by GB/T 1179-2017 Round Wire Concentric Lay Overhead electrical Stranded Conductors.

2.1.3 Rapid Water Droplet Detachment Experiment

[0061] FIG. 3 shows the initial amount of stored lubricant under different pore depth ratios, as well as the number of self-healing cycles under different pore depth ratios.

[0062] FIG. 4 shows the self-healing time under different pore depth ratios.

[0063] Conclusion: (1) The dendritic composite porous structure can store more lubricant than the conventional (traditional) single-layer porous structure. Due to the higher lubricant storage capacity, it also achieves a greater number of self-healing cycles than the conventional single-layer porous structure. (2) Increasing the pore depth of the lower pores enhances the storage capacity of the lubricant (e.g., a 1:5 pore depth ratio stores more lubricant than a 1:2 pore depth ratio). However, the number of self-healing cycles is found to be the same for both the 1:3 and 1:5 pore depth ratios, indicating that 1:3 pore depth ratio is a critical value. The 1:2 pore depth ratio yields only one fewer cycle than the 1:3 pore depth ratio. (3) It is also found that when the pore depth ratio is very small (e.g., 1:5), the proportion of lower pores increases. Since the lubricant migration speed is inversely proportional to the pore diameter, a smaller pore depth ratio results in longer self-healing time. (4) When the pore depth ratio (upper to lower) is 1:2, the self-healing time across the entire experiment is the shortest (e.g., for seven cycles of healing, the green curve on the left of the time axis shows the shortest duration), indicating the fastest self-healing speed.

[0064] In summary, considering both lubricant storage capacity and self-healing time/speed, the optimal pore depth ratio (upper to lower) is less than 1:2.

2.2 Determination of the Optimal Porosity

2.2.1 Morphology

[0065] FIG. 5 shows the surface and cross-sectional morphology of porous structures with different porosity levels.

2.2.2 Structural Parameters

TABLE-US-00003 TABLE 3 Structural characteristics of porous surfaces with different surface porosity levels Dendritic composite porous structure (Y) Surface porosity (%) 37 50 66 72 Surface Average pore size 80.6 9.7 98.0 11.2 116.6 14.9 131.1 21.0 (nm) Upper-layer pore 9.7 9.5 9.7 7.3 depth (m) Cross- Lower-layer pore 20.2 21.2 21 21.5 section depth (m) Pore depth ratio 1:2 1:2 1:2 0.8:2 (upper to lower) Total pore depth (m) 29.9 30.7 30.7 28.8

[0066] Conclusion: In this embodiment, dendritic porous structures with different surface porosity levels are prepared by performing a pore expansion process. When the pore depth ratio of the upper pores to the lower pores is 1:2, the surface porosity is 50%-66%.

[0067] Studies have confirmed that low porosity is detrimental to the stability of the lubricant film and the anti-wettability of the lubricated surface, as well as the lubricant storage capacity. In other words, porosity is related to the oil-retaining capability. However, when the pore expansion process increases the porosity beyond a certain threshold, it may lead to rupture of the pore walls and collapse of the upper pore structure, resulting in the formation of micron-scale corrosion pits (i.e., larger pores). This not only compromises anti-wetting performance but also accelerates lubricant consumption. FIG. 6 shows enlarged views of structures with different porosity levels, indicating that when the porosity reaches 72%, the pore structure is visibly damaged. Among the porous structures prepared, the morphology is found to be optimal when the porosity is 66%.

2.2.3 Slow Water Droplet Detachment Experiment

[0068] FIGS. 7 and 8 show the experimental results of porous structures with different porosity levels in the slow water droplet detachment experiment.

[0069] Conclusion: The results further confirm that increasing surface porosity enhances the lubricant storage capacity and shortens the self-healing time. However, when surface porosity becomes too high (e.g., 72%), partial collapse and damage of the pore walls occur, accelerating lubricant consumption. Therefore, considering lubricant storage capacity, lubricant consumption, and self-healing speed comprehensively, the optimal surface porosity is approximately 66%.

Embodiment 3

[0070] Determination of the spacing between adjacent pores (inter-pore spacing) in the dendritic porous structure

1. Experiment

[0071] The dendritic porous structure is prepared using the method described in Embodiment 1. The inter-pore spacing is measured using the ImageJ software based on scanning electron microscope (SEM) images.

2. Results

2.1 Effect of Inter-Pore Spacing on Ice Adhesion Strength

[0072] In general, the spacing between adjacent pores is correlated with the ice adhesion strength. Smaller inter-pore spacing leads to lower ice adhesion strength. However, if the inter-pore spacing becomes too small, friction between the ice and the structure surface during the de-icing process increases, which may result in structural damage to the pores. FIG. 9 shows the effect of inter-pore spacing on ice adhesion strength.

[0073] Conclusion: This embodiment confirms that when the porosity of the dendritic composite porous structure is within the range of 50%-66%, the ice adhesion strength on the dendritic composite porous structure is not greater than 5 kPa. In contrast, in the prior art, the ice adhesion strength of anti-icing conductors is typically defined at no greater than 20 kPa. Furthermore, the experimental results of this embodiment reveal that as the ice adhesion strength on the anti-icing conductor decreases, both the volume and thickness of accreted ice on the conductor are significantly reducedsubstantially below the critical icing thickness of 30 cm commonly observed in the prior art. As a result, when ice blocks or icicles formed on the conductor detach from the conductor, the amplitude of de-icing jumping or galloping is significantly reduced, thereby contributing to the extended service life of the conductor.

[0074] Experimental results of this embodiment further reveal that when the ice adhesion strength is controlled below 5 kPa, the inter-pore spacing of the structure prepared by the method of the present invention falls within the range of 10 nm 38 nm. When the inter-pore spacing exceeds 38 nm, the ice adhesion strength rises above 5 kPa. If the inter-pore spacing falls below 10 nm, de-icing operations on the sample surface may damage the pore structure.

2.2 Volume of Different Porous Structures Under Identical Inter-Pore Spacing

[0075] FIG. 10 compares the pore volume of different porous structures when the inter-pore spacing is identical.

[0076] Conclusion: The formula for calculating the pore area is as follows:

[0077] Wherein m, n, and k respectively represent the number of pores; A and B represent the pore areas; V represents the pore volume; and H represents the pore depth. For a simple composite porous structure, it must hold that V.sub.2>V.sub.1.

[00002]$V_1=\left({.Math.}_{i=1}^n{A}_i\right)\left(H_1+H_2\right);V_2=\left({.Math.}_{i=1}^n{A}_i\right)H_1+\left({.Math.}_{i=1}^n{B}_i\right)H_2.$

[0078] When the pores are densely arranged such that the inter-pore spacing is sufficiently small, the volume (V.sub.3) of a single-layer porous structure may also exceed V.sub.2. Therefore, the design of a simple composite porous structure does not necessarily demonstrate a greater lubricant storage capacity compared to a single-layer porous structure.

[00003]$V_3=\left({.Math.}_{i=1}^m{A}_i\right)\left(H_1+H_2\right).$

[0079] However, in the dendritic composite porous structure prepared in this embodiment, the upper pores are densely arranged and the volume of the lower pores is increased:

[00004]$V_4=\left({.Math.}_{i=1}^m{A}_i\right)H_1+\left({.Math.}_{i=1}^k{B}_i\right)H_2.$

Therefore, in order to ensure V.sub.4>V.sub.3,

[00005]${.Math.}_{i=1}^m{A}_i>{.Math.}_{i=1}^k{B}_i$

must be satisfied. Accordingly, in the dendritic composite porous structure designed in this embodiment, m:k=4-6:1; A.sub.i:B.sub.i=1:31:2.

Embodiment 4

Functional Characterization of the Dendritic Composite Porous Structure

Durability Verification of the Lubricated Surface with Dendritic Porous Structure

1. Characterization:

[0080] Measurement of ice adhesion strength. The sample is fixed on a platform inside an environmental chamber. A hollow cylindrical plastic mold is placed on the sample surface and filled with water to a height of approximately 10 mm. The temperature and humidity in the chamber are maintained at 15 C. and 40%, respectively. After 30 min, the water is completely frozen, forming an ice block with a diameter of 14.2 mm. A force sensor (HANDPI, SH-100N, China) is used to push the mold horizontally, with the probe kept 3 mm from the sample surface and a loading speed of approximately 1 mm/s. The maximum shear force during the separation of the mold from the sample is recorded, and the ice adhesion strength is subsequently calculated. Durability of the SLIPS is evaluated through repeated icing/de-icing cycles. The icing procedure follows the same steps as the ice adhesion strength test. Ice is mechanically removed to complete one icing/de-icing cycle. During the cycles, the sample's contact angle (CA), contact angle hysteresis (CAH), ice adhesion strength, and lubricant retention rate are measured. Both conventional single-layer porous surfaces and dendritic porous surfaces are tested repeatedly for frosting/defrosting cycles until the ice adhesion strength of the dendritic porous surface exceeds 20 kPa (the upper limit for self-deicing behavior of anti-icing surfaces).

[0081] Frosting experiments are conducted using a Peltier cooling plate maintained at 8 C. to test the anti-frosting performance of SLIPS. The plate is enclosed with insulating foam, and humidity is maintained at approximately 99% using a humidifier. Macroscopic images of the frosting process are recorded using a camera, and the microscopic morphology is measured using a digital microscope (MIXOUT, SM-U500, China). The frosting time is recorded when all condensation droplets on the sample surface has frozen. Durability of SLIPS is evaluated through multiple frosting/defrosting cycles. After the surface of the sample on the cooling plate is fully frosted, the frosted layer is heated to remove the frost, completing one cycle. Ice adhesion strength, CA, frosting time, and lubricant retention rate are measured during cycles. Long-term icing/de-icing cycle tests are conducted on both conventional single-layer porous surfaces and dendritic porous surfaces. Once the ice adhesion strength exceeds 20 kPa, the sample is allowed to rest for 12 hours for sufficient self-healing. The icing/de-icing-healing cycle is repeated until the ice adhesion strength still exceeds 20 kPa after self-healing.

2. Results

2.1 Frosting/Defrosting Cycles

[0082] FIGS. 11 and 12 show the results of the frosting/defrosting cycles on conventional single-layer porous surfaces (I-SLIPS) and dendritic composite porous surfaces (Y-SLIPS).

[0083] Conclusion: (1) The dendritic composite porous surface (Y-SLIPS) exhibits an ice adhesion strength exceeding 20 kPa at the 140th frosting/defrosting cycle, surpassing the critical threshold defined in the prior art. In contrast, the conventional single-layer porous surface (I-SLIPS) reaches the 20 kPa threshold at the 100th frosting/defrosting cycle. (2) With an increasing number of the frosting/defrosting cycles, the frosting time on the lubricated surfaces decreases, indicating a decline in the self-healing capability of the conductor. At the 140th frosting/defrosting cycle, the dendritic composite porous surface shows a drop in anti-frosting performance, whereas the conventional single-layer porous surface (I-SLIPS) exhibits a significantly shorter frosting time, demonstrating that Y-SLIPS has superior long-term anti-frosting durability compared to I-SLIPS.

2.2 Long-Term Icing/De-Icing Cycles

[0084] Conclusion: Using the same critical ice adhesion strength threshold of 20 kPa defined by the prior art, Y-SLIPS is able to endure approximately 190 icing/de-icing cycles. This is attributed to its higher lubricant storage capacity, slower lubricant consumption, and timely self-healing, which help maintain low ice adhesion strength. Y-SLIPS exhibits six effective self-healing events before failure occurred on the seventh attempt. Under the same conditions, I-SLIPS could only endure 140 icing/de-icing cycles, with the ice adhesion strength exceeding 20 kPa after the 140th icing/de-icing cycle. I-SLIPS exhibits only four effective self-healing events, failing on the fifth. Therefore, compared to I-SLIPS, the Y-SLIPS structure formed using the dendritic composite porous structure demonstrates superior anti-icing durability and longer service life under icing conditions.

Embodiment 5

Effect of the Preparation Method on the Dendritic Composite Porous Structure

[0085] 1. A brief description of the preparation method is as follows: [0086] (1) First, anodization is performed in an H.sub.2C.sub.2O.sub.4 electrolyte for 6-10 min to form the upper pores (also referred to as oxalic acid small pores in the upper layer). [0087] (2) Next, anodization is performed in an H.sub.3PO.sub.4 electrolyte for 7-12 min to form the lower pores (referred to as phosphoric acid large pores in the lower layer). [0088] (3) Finally, immersing the formed two-layer porous structure in an H.sub.3PO.sub.4 solution for 0-45 minutes to perform pore expansion (expand the pore diameter of the formed two-layer porous product).

[0089] The challenge in this preparation method lies in the second anodization step: the phosphoric acid electrolyte tends to dissolve the already formed oxalic acid pores in the upper layer. By controlling the concentration of aluminum ions in the solution, the chemical dissolution rate of the upper pore walls by phosphoric acid can be regulated. Anodization is currently the most convenient and effective method for preparing nanoporous structures. However, using anodization to create multilayer porous structures involves a dynamic process in which new pores form while previously formed pores dissolve. If this process is not properly controlled, it becomes difficult to obtain a porous structure that meets the requirements.

[0090] Therefore, by adjusting the anodization current and anodization duration, dendritic composite porous structures with different pore depth ratios and total depths can be obtained. Dendritic porous structures with different porosity levels can also be achieved by controlling the concentration of aluminum ions. Changes in anodization duration and current density affect not only the pore depth ratio but also the surface characteristics of the pores.

2. Results

[0091] 2.1 Effect of aluminum ion concentration on the surface morphology of the formed dendritic composite porous structure is shown in FIG. 13.

TABLE-US-00004 TABLE 4 Experimental results of aluminum ion concentration Aluminum ion concentration 0-330 330-600 600-700 700-1000 mg/L mg/L mg/L mg/L >1000 mg/L Surface Pore walls Partial Densely Relatively Even sparser morphology ruptured rupture of arranged sparse nano- nano-scale surface pore small pores scale pore pore walls arrangement arrangement

[0092] Conclusion: When the concentration of aluminum ions is in the range of 600-700 mg/L, densely arranged small pores are readily formed on the surface, which meets the performance requirements for active anti-icing as described in the present invention.

[0093] 2.2 Experimental results under different anodization durations and current densities are shown in FIG. 14.

TABLE-US-00005 TABLE 5 Experimental results of different anodization durations and current densities Current density <0.08 A/cm.sup.2 0.08~0.16 A/cm.sup.2 >0.16 A/cm.sup.2 Anodization duration <12 min 12-18 min >18 min Surface morphology Sparse nano- Densely arranged Pore walls scale pores small pores ruptured Pore Upper layer 11.8 9.7 7.3 depth (m) of Lower layer 8.5 21.0 23.2 upper (m) and lower layers

[0094] Conclusion: Densely arranged small pores meeting the requirements can be obtained by controlling the anodization current density (0.080.16 A/cm.sup.2) and anodization duration (12-18 min). In addition, the anodization current density and duration also affect the depth of the resulting pores.

Embodiment 6

Comparison Between the Dendritic Composite Porous Structure Prepared by the Method of the Present Invention and the Composite Porous Structure in the Prior Art

TABLE-US-00006 TABLE 6 Comparison of different composite porous structures Comparison Dendritic composite porous Composite porous structure in the item structure prior art Porous Dendritic porous structure with a Two-layer composite porous structure structure smaller upper pore and a larger with a larger outer pore and a smaller lower pore; the depth ratio of the inner pore; the depths of the inner and upper pore to the lower pore is outer pores are the same; the inner less than 1:2; the number ratio of pore is filled with a healing agent, and the upper pore to the lower pore is the outer pore comprises an air 4-6:1. The composite porous cushion. structure is fully filled with a modifier. Function of The larger lower pore stores the The inner pore stores the healing pores modifier and the smaller upper agent and the outer pore forms an air pore reduces the consumption. cushion to repel water droplets under The non-1:1 (the number ratio of low temperature conditions. the upper pore to the lower pore) arrangement allows more storage of the modifier. Preparation 1. Oxidation in H.sub.2C.sub.2O.sub.4 electrolyte 1. Oxidation in H.sub.3PO.sub.4 electrolyte to method to form the upper pore. form the outer pore. 2. Oxidation in H.sub.3PO.sub.4 electrolyte 2. Oxidation in H.sub.2C.sub.2O.sub.4 electrolyte to to form the lower pore. form the inner pore. 3. Immersion of the formed two- layer porous structure in H.sub.3PO.sub.4 solution to perform pore expansion. Surface ice Not greater than 5 kPa 6.5 kPa adhesion strength Problem Active anti-icing Delayed icing addressed

[0095] The embodiments of the present invention are described above with reference to the accompanying drawings, but the present invention is not limited to the aforementioned specific embodiments. The aforementioned embodiments are merely illustrative and not limiting. For those of ordinary skill in the art, many forms can be made under the teaching of the present invention without departing from the spirit of the present invention and the scope of the claims, all of which shall fall within the protection scope of the present invention.