Green multifunctional super-hydrophobic foamed aluminum material and preparation method thereof

Abstract

The invention discloses a green multifunctional super-hydrophobic foamed aluminum material and a preparation method thereof, and belongs to the technical field of metal surface modification. The method comprises the following steps: pretreating foamed aluminum; preparing an electrolyte containing oxalic acid, perfluorobutanesulfonic acid, silver nitrate, tea saponin and ethylene glycol; one-step asymmetric pulse electrochemical treatment is carried out, and specific positive, negative and tail end heat preservation pulse programs are included; and finally, the SiC coating is formed at the temperature of 800-900 DEG C through chemical vapor deposition. According to the invention, a multi-corrosion-resistant system comprising the electrochemical modified substrate, the super-hydrophobic layer and the SiC protective layer is constructed, and the self-repairing function of the fluorine-containing silane microcapsule and the antibacterial function of silver nitrate are cooperated; the prepared material has the characteristics of super-hydrophobicity (the contact angle is larger than or equal to 160 degrees), efficient antibiosis (the killing rate is larger than or equal to 99%), self-repairing (repairing within 12 hours after friction), super-strong corrosion resistance (the salt mist time is larger than or equal to 5000 hours), extreme environment resistance and the like, is environment-friendly and non-toxic, and is particularly suitable for ocean engineering, food industry and deep sea detection equipment.

Description

Technical Field

[0001] This invention relates to the field of surface modification technology for metallic materials, specifically to a green, multifunctional superhydrophobic foam aluminum material and its preparation method. This material is particularly suitable for fields with stringent requirements for corrosion resistance, antibacterial properties, self-healing capabilities, and environmental friendliness, such as marine engineering equipment, food processing equipment, and deep-sea exploration devices. Background Technology

[0002] Aluminum foam, as a lightweight porous metallic material, has attracted widespread attention due to its high specific strength, excellent energy absorption, and damping properties. However, its huge specific surface area and complex pore structure also bring significant drawbacks: corrosive media (such as chloride ions) easily adhere to and penetrate, leading to thinning and perforation of the internal pore walls and a rapid decline in mechanical properties. This problem is particularly prominent in high-temperature, high-humidity, and high-salt marine or industrial environments.

[0003] In existing technologies, surface coatings or chemical conversion films are commonly used to improve the corrosion resistance of aluminum foam. For example, the method of preparing hydrophobic coatings using silane coupling agents improves hydrophobicity to some extent, but the coatings have low mechanical strength, are easily worn, and lack antibacterial properties. Another method involves constructing micro-nano structures on the surface of aluminum foam through anodic oxidation, followed by modification with fluorosilanes to obtain superhydrophobic properties. However, this method is complex, the resulting coatings are prone to failure under thermal stress or mechanical friction, and it does not address the issues of antibacterial properties and environmental friendliness.

[0004] Especially in extreme pressure environments such as deep-sea exploration, the existing functional coatings of aluminum foam often crack and peel off under pressure-temperature cycling due to a mismatch in thermal expansion coefficients with the substrate, resulting in permanent loss of function. In addition, many high-efficiency modifiers (such as perfluorinated compounds containing PFOA / PFOS) have been restricted due to their environmental toxicity, making the development of green and environmentally friendly alternative technologies urgent.

[0005] Therefore, there is an urgent need in this field for a foamed aluminum material and its preparation method that can simultaneously achieve excellent corrosion resistance, mechanical stability, long-lasting superhydrophobicity, antibacterial function, self-healing ability, and meet environmental protection requirements. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a green, multifunctional superhydrophobic aluminum foam material and its preparation method. This method constructs a multi-layered corrosion-resistant system consisting of an "electrochemically modified substrate + superhydrophobic layer + SiC protective layer," and introduces self-healing microcapsules and a green corrosion inhibitor, thus solving the problems of poor corrosion resistance, limited functionality, short lifespan, and insufficient environmental friendliness of aluminum foam under extreme environments.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a green, multifunctional, superhydrophobic aluminum foam material, comprising the following steps: (1) Pretreatment: The aluminum foam with a porosity of 65%-80% was ultrasonically degreased with 10wt% hydrochloric acid solution, rinsed with deionized water until neutral, and then vacuum dried at 60℃ for 2h. (2) Electrolyte preparation: Prepare an electrolyte containing 0.1-1M oxalic acid, 0.01-0.08M perfluorobutyric acid (PFBS), 0.005-0.01M silver nitrate, 0.5wt% tea saponin, and 0-20vol% ethylene glycol of the total volume of the electrolyte; (3) One-step asymmetric pulse electrochemical treatment: The pretreated aluminum foam is used as the anode and the platinum sheet is used as the cathode. It is immersed in the electrolyte prepared in step (2), the electrolyte temperature is controlled at 25-35℃, the electrode spacing is 3-5cm, and an asymmetric pulse power supply is applied for treatment. The parameters of the asymmetric pulse power supply are: Positive pulse voltage 40-80V, pulse width 10-100ms; Negative pulse voltage 10-15V, pulse width 5-50ms; The time ratio of the positive pulse to the negative pulse is 3:1; After reacting for 25-35 minutes, an end-heating pulse is applied. The voltage of the end-heating pulse is 20-40V, the pulse width is 100-500ms, the duty cycle is 5%-15%, and the sample is removed after 5 minutes. (4) Vapor deposition of SiC coating: The foamed aluminum treated in step (3) is placed in a chemical vapor deposition furnace and heated to 800-900℃ at a heating rate of 5℃ / min. Under a pressure of 1-2kPa, SiCl4 is used as the silicon source and CH4 is used as the carbon source. The molar ratio of SiCl4 to CH4 is controlled to be 1:2. The deposition is carried out for 1-3h to form a SiC coating with a thickness of 1-3μm. After the deposition is completed, the furnace is cooled to below 200℃ and taken out to obtain the green multifunctional superhydrophobic foamed aluminum material.

[0008] Preferably, in step (2), the electrolyte further comprises 1-3% of fluorinated silane microcapsules by mass of the electrolyte.

[0009] Preferably, the preparation method of the fluorinated silane microcapsules is as follows: using perfluorooctyltriethoxysilane as the core and urea-formaldehyde resin prepolymer as the wall material, with a core-to-wall material mass ratio of 40:60, the mixture is emulsified by high-speed stirring at 3000 r / min, and then cured at 40°C for 2 h, and sieved to obtain microcapsules with a particle size of 1-5 μm.

[0010] Preferably, in step (2), the tea saponin is a food-grade extract with a purity of ≥95%.

[0011] Preferably, in step (3), the end heat preservation pulse promotes the directional self-assembly of low surface energy molecules on the surface of aluminum foam to form a more stable monolayer, so as to avoid the cracking of the hydrophobic layer caused by subsequent vapor deposition heat treatment.

[0012] Secondly, the present invention provides a green, multifunctional, superhydrophobic aluminum foam material prepared by the above-described preparation method, characterized in that the material has: (1) Superhydrophobic properties: Static water contact angle ≥160°, roll-off angle ≤3°; (2) Antibacterial properties: The kill rate against Escherichia coli and Staphylococcus aureus is ≥99%; (3) Self-healing performance: After 1500 sandpaper rubbings, the static water contact angle is ≥155°, and it can self-heal to ≥158° within 12 hours; (4) Corrosion resistance: Salt spray test according to ASTM B117 standard, salt spray corrosion resistance time ≥5000h, corrosion rate ≤0.001mm / a.

[0013] Preferably, the material exhibits a static water contact angle attenuation rate of ≤5% within a temperature range of -40℃ to 200℃.

[0014] Preferably, the material can maintain a static water contact angle of ≥158° under an external hydrostatic pressure of 10MPa.

[0015] Thirdly, the present invention provides applications of the above-mentioned green multifunctional superhydrophobic foam aluminum material for the preparation of anti-biofouling components for ships, contact surfaces of food processing equipment, or shells of deep-sea exploration equipment.

[0016] The beneficial effects of this invention are as follows: A synergistic multi-layered protection system was constructed: a dense substrate rich in silver antibacterial sites was created through synergistic electrochemical modification using oxalic acid and silver nitrate; perfluorobutyric acid and tea saponin worked together to achieve synergistic effects of low surface energy and corrosion inhibition; and the outermost SiC coating provided a high-strength, wear-resistant physical barrier. This system significantly improved the overall durability of the material.

[0017] This method achieves a balance between environmental friendliness and multifunctionality: by using environmentally friendly perfluorobutyric acid (PFBS) and bio-derived tea saponins, it completely avoids the use of harmful substances such as PFOA, making the material suitable for food contact applications. Simultaneously, this method integrates superhydrophobicity, highly efficient antibacterial properties, and self-healing capabilities, addressing the limitation of traditional materials having only single functionalities.

[0018] The process is highly innovative and yields significant results: Utilizing a "one-step asymmetric pulsed electrochemical treatment" combined with "end-stage heat preservation pulses" not only optimizes the uniformity of the aluminum foam pore structure and avoids stress concentration under deep-sea high pressure, but also promotes the stable assembly of the superhydrophobic molecular layer, preventing cracking during subsequent high-temperature SiC deposition. The introduction of fluorinated silane microcapsules provides the coating with inherent self-healing capabilities, greatly extending its service life.

[0019] Outstanding resistance to extreme environments: Thanks to the excellent chemical inertness, thermal stability and mechanical strength of the SiC coating, as well as the introduction of ethylene glycol in the electrolyte, the material of this invention can still maintain superhydrophobicity and structural integrity under extreme environments such as wide temperature range (-40℃ to 200℃), high salt spray and high hydrostatic pressure (10MPa), thus expanding the application boundaries of aluminum foam. Detailed Implementation

[0020] The present invention will be further described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0021] Example 1: Superhydrophobic aluminum foam suitable for food processing equipment Raw materials and proportions: 70% porosity aluminum foam. Electrolyte: 0.5M oxalic acid, 0.05MPFBS, 0.005MAgNO3, 0.5wt% tea saponin (food grade, purity ≥95%), 2wt% fluorinated silane microcapsules (particle size 1-3μm).

[0022] Process steps: (1) Pretreatment: Performed as described above.

[0023] (2) Electrochemical treatment: Electrode spacing 3cm, electrolyte temperature 25℃. Apply asymmetric pulses: positive 60V / 50ms, negative 12V / 17ms, time ratio 3:1, for 30min. Then apply end-heating pulse (30V, 300ms, duty cycle 10%) for 5min.

[0024] (3) Vapor deposition of SiC: 850℃, 1.5kPa, deposition for 2h to form a SiC coating of about 2μm thickness.

[0025] Performance testing: Water contact angle 163°, roll-off angle 2.5°. E. coli kill rate 99.2%. Contact angle 156° after 1500 cycles of friction, restored to 161° after 10 hours. No corrosion after 5200 hours of salt spray testing, corrosion rate 0.0008 mm / a. PFOA not detected (<0.01 mg / kg).

[0026] Example 2: Antibacterial superhydrophobic aluminum foam suitable for marine vessels Raw materials and proportions: 75% porosity aluminum foam. Electrolyte: 0.8M oxalic acid, 0.08MPFBS, 0.01MgNO3, 0.5wt% tea saponin, 20vol% ethylene glycol, 3wt% fluorinated silane microcapsules.

[0027] Process steps: Electrochemical treatment parameters were adjusted to 80V / 100ms positive and 15V / 33ms negative, with a reaction time of 35 min. Vapor deposition was carried out at 900℃ and 2kPa for 3 h.

[0028] Performance testing: Water contact angle 165°. Contact angle attenuation rate <3% after treatment at -40℃ and 200℃. Kills >99.5% of various marine bacteria. No corrosion after 6000 hours of salt spray testing. Biofouling area <5% after 3 months of marine immersion.

[0029] Example 3: High-pressure corrosion-resistant aluminum foam suitable for deep-sea exploration equipment Raw materials and proportions: Aluminum foam with a porosity of 65%. Electrolyte: 0.1M oxalic acid, 0.01MPFBS, 0.008MAgNO3, 0.5wt% tea saponin, 10vol% ethylene glycol, 1wt% fluorinated silane microcapsules.

[0030] Process steps: Electrochemical treatment parameters were 40V / 10ms positive and 10V / 3.3ms negative, with a reaction time of 25 min. Vapor deposition was performed at 800℃ and 1kPa for 3 h to form a SiC coating approximately 3 μm thick to enhance pressure resistance.

[0031] Performance testing: Under 10MPa hydrostatic pressure, the contact angle remained at 160°. No corrosion was observed after 5500 hours of salt spray testing, and the corrosion rate remained ≤0.001mm / a after 3000 hours of salt spray testing under 10MPa high pressure. No structural deformation was observed under 15MPa pressure.

[0032] Comparative Example 1 Compared to Example 1, step (4) of vapor deposition of SiC coating is omitted. All other conditions are the same.

[0033] Results: The obtained material initially exhibited good hydrophobicity (contact angle 159°), but after 500 cycles of sandpaper rubbing, the contact angle decreased to below 140° and could not self-repair. Obvious corrosion spots appeared after 800 hours of salt spray testing.

[0034] Comparative Example 2 Compared to Example 2, no fluorinated silane microcapsules were added to the electrolyte. All other conditions remained the same.

[0035] Results: The initial properties of the obtained material were similar to those of Example 2, but after 1500 rubs, the contact angle dropped to 148° and could only be repaired to 152° within 24 hours, indicating a significant weakening of the self-healing ability.

[0036] The above embodiments and comparative examples fully demonstrate the synergistic effect between the various technical features of the present invention and the unexpected technical effects they bring.

Claims

1. A method for preparing a green, multifunctional, superhydrophobic aluminum foam material, characterized in that, Includes the following steps: (1) Pretreatment: The aluminum foam with a porosity of 65%-80% was ultrasonically degreased with 10wt% hydrochloric acid solution, rinsed with deionized water until neutral, and then vacuum dried at 60℃ for 2h. (2) Electrolyte preparation: Prepare an electrolyte containing 0.1-1M oxalic acid, 0.01-0.08M perfluorobutyric acid, 0.005-0.01M silver nitrate, 0.5wt% tea saponin, and 0-20vol% ethylene glycol of the total volume of the electrolyte; (3) One-step asymmetric pulse electrochemical treatment: The pretreated aluminum foam is used as the anode and the platinum sheet is used as the cathode. It is immersed in the electrolyte prepared in step (2), the electrolyte temperature is controlled at 25-35℃, the electrode spacing is 3-5cm, and an asymmetric pulse power supply is applied for treatment. The parameters of the asymmetric pulse power supply are: Positive pulse voltage 40-80V, pulse width 10-100ms; Negative pulse voltage 10-15V, pulse width 5-50ms; The time ratio of the positive pulse to the negative pulse is 3:1; After reacting for 25-35 minutes, an end-heating pulse is applied, the voltage of which is... 20-40V, pulse width 100-500ms, duty cycle 5%-15%, continue for 5 minutes and then remove the sample; (4) Vapor deposition of SiC coating: The foamed aluminum treated in step (3) is placed in a chemical vapor deposition furnace and heated to 800-900℃ at a heating rate of 5℃ / min. Under a pressure of 1-2kPa, SiCl4 is used as the silicon source and CH4 is used as the carbon source. The molar ratio of SiCl4 to CH4 is controlled to be 1:

2. The deposition is carried out for 1-3h to form a SiC coating with a thickness of 1-3μm. After the deposition is completed, the furnace is cooled to below 200℃ and taken out to obtain the green multifunctional superhydrophobic foamed aluminum material.

2. The preparation method according to claim 1, characterized in that, In step (2), the electrolyte also contains 1-3% of fluorinated silane microcapsules by mass of the electrolyte.

3. The preparation method according to claim 2, characterized in that, The method for preparing the fluorinated silane microcapsules is as follows: using perfluorooctyltriethoxysilane as the core and urea-formaldehyde resin prepolymer as the wall material, with a core-to-wall material mass ratio of 40:60, the mixture is emulsified by high-speed stirring at 3000 r / min, and then cured at 40℃ for 2 h. Microcapsules with a particle size of 1-5 μm are obtained by sieving.

4. The preparation method according to claim 1, characterized in that, In step (2), the tea saponin is a food-grade extract with a purity of ≥95%.

5. The preparation method according to claim 1, characterized in that, In step (3), the end heat preservation pulse is used to promote the directional self-assembly of low surface energy molecules on the surface of aluminum foam, so as to avoid the cracking of the hydrophobic layer caused by subsequent vapor deposition heat treatment.

6. A green, multifunctional, superhydrophobic aluminum foam material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, This material has the following characteristics: (1) Superhydrophobic properties: Static water contact angle ≥160°, roll-off angle ≤3°; (2) Antibacterial properties: The kill rate against Escherichia coli and Staphylococcus aureus is ≥99%; (3) Self-healing performance: After 1500 sandpaper rubbings, the static water contact angle is ≥155°, and it can self-heal to ≥158° within 12 hours; (4) Corrosion resistance: Salt spray test according to ASTM B117 standard, salt spray corrosion resistance time ≥5000h, corrosion rate ≤0.001mm / a.

7. The green multifunctional superhydrophobic aluminum foam material according to claim 6, characterized in that, The material exhibits a static water contact angle attenuation rate of ≤5% within a temperature range of -40℃ to 200℃.

8. The green multifunctional superhydrophobic aluminum foam material according to claim 6, characterized in that, The material can still maintain a static water contact angle of ≥158° under an external hydrostatic pressure of 10MPa.

9. An application of a green, multifunctional, superhydrophobic aluminum foam material as described in any one of claims 6 to 8, characterized in that, Used to manufacture anti-biofouling components for ships, contact surfaces for food processing equipment, or outer shells for deep-sea exploration equipment.