Glutamic acid modified electroplated nickel-chromium alloy-based high-hardness super-hydrophobic coating and preparation method thereof

Abstract

According to the glutamic acid modified electroplated nickel-chromium alloy-based high-hardness super-hydrophobic coating and the preparation method thereof, aluminum alloy serves as a cathode, a platinum sheet electrode serves as an anode, nickel-chromium alloy electroplating liquid is adopted, electroplating is carried out under the ultrasonic condition, after electroplating is completed, the surface of an electroplated layer is coated with an HDTMS ethanol diluent, and the glutamic acid modified electroplated nickel-chromium alloy-based high-hardness super-hydrophobic coating is obtained. And heating to obtain the electroplated nickel-chromium alloy-based high-hardness super-hydrophobic coating. According to the glutamic acid modified electroplated nickel-chromium alloy-based high-hardness super-hydrophobic coating, in the electroplating process, glutamic acid modified aluminum oxide nano-particles are introduced into the alloy coating, and glutamic acid can enhance the dispersity of the aluminum oxide nano-particles in a water-phase electroplating solution so as to enhance the dispersity of the nano-particles in a nickel-chromium alloy layer; and the coordination effect between amino groups hung on the aluminum oxide nanoparticles and subsequently coated HDTMS can be enhanced, and the interface strengthening effect between the nickel-chromium-aluminum oxide high-hardness coating and the HDTMS can also be achieved through the coordination effect between amino groups hung on the nickel-chromium alloy and the HDTMS.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of materials, and particularly relates to a glutamic acid modified electroplated nickel-chromium alloy based high-hard super-hydrophobic coating and a preparation method thereof. BACKGROUND

[0002] High-hard wear-resistant high-adhesion super-hydrophobic coatings have significant application value in the fields of industrial manufacturing, aerospace, smart materials, etc. Super-hydrophobic coatings coated on the surfaces of various substrates are usually used as anti-corrosion, surface cleaning, antibacterial, etc. to realize the protection of the substrate surface. Coating a super-hydrophobic protective film on the surface of an aluminum alloy is also an effective method for protecting the aluminum alloy material, thereby significantly enhancing its durability. Although super-hydrophobic coatings have shown many advantages as described above, their mechanical durability is still not satisfactory, including the insufficient adhesion between the hydrophobic coating and the substrate and the insufficient wear resistance of the hydrophobic coating, which makes the hydrophobic properties of the super-hydrophobic coating not long-lasting. The currently reported methods for strengthening the mechanical properties of super-hydrophobic coatings also include network crosslinking of high polymer coatings and strengthening of resin-based hydrophobic coatings, etc. SUMMARY

[0003] Therefore, the present application aims to overcome the defects in the prior art and proposes a glutamic acid modified electroplated nickel-chromium alloy based high-hard super-hydrophobic coating and a preparation method thereof.

[0004] To achieve the above-mentioned purposes, the technical solution of the present application is as follows: A modified alumina nanoparticle, wherein the modified alumina nanoparticle is obtained by surface modification of alumina nanoparticles with glutamic acid.

[0005] The glutamic acid modified alumina nanoparticles are used to enhance the dispersibility of the nanoparticles in the aqueous electroplating solution. One carboxyl group (-COOH) in the glutamic acid molecule can be dissociated into a carboxyl anion (-COO - ), which forms a stable coordination bond (O-Al coordination, similar to a metal-carboxylic acid complex) with Al 3+ or bonds with the hydroxyl group (-OH) on the surface of the alumina, thereby anchoring the glutamic acid on the surface of the alumina nanoparticles and forming an organic modification layer. The other carboxyl group of the glutamic acid remains as a free carboxyl group due to steric hindrance or low reactivity. The increased hydrophilicity of the nanoparticle surface and the electrostatic repulsion on the nanoparticle surface (the amino group can be protonated to -NH3 + in water, and the carboxyl group itself is negatively charged) together enhance the dispersibility of the alumina nanoparticles in the aqueous electroplating solution, thereby avoiding agglomeration and uniformly dispersing the alumina nanoparticles in the nickel-chromium alloy layer during electroplating, thereby significantly improving the hardness and wear resistance of the alloy layer.

[0006] Further, the modified alumina nanoparticles are made by a method comprising the following steps: dissolving glutamic acid in deionized water, mixing uniformly to obtain a glutamic acid aqueous solution, dispersing alumina nanoparticles in the glutamic acid aqueous solution, adjusting the pH value of the solution, stirring under heating, centrifuging, washing, and drying after the reaction is completed to obtain the modified alumina nanoparticles.

[0007] Further, the mass ratio of the alumina nanoparticles, glutamic acid, and deionized water is 1-5:0.2-1:100; the particle size of the alumina nanoparticles is 20-100 nm; the temperature of the deionized water is 30-60℃; the pH value is 5-7; the heating temperature is 40-60℃, and the stirring time is 4-10 hours.

[0008] Further, the electroplating solution contains the modified alumina nanoparticles.

[0009] Further, the electrolyte further comprises the following components with the following molar concentrations: nickel chloride 0.3-0.6 M, chromium chloride 0.3-0.6 M, sodium citrate 0.2-0.4 M, citric acid 0.3-0.5 M, and glutamic acid 0.02-0.1 M.

[0010] A preparation method of a glutamic acid-modified electroplated nickel-chromium alloy-based high-hard super-hydrophobic coating, comprising the following steps: An aluminum alloy is used as the cathode, a platinum electrode is used as the anode, the nickel-chromium alloy electroplating solution is used for electroplating under ultrasonic conditions, and after the electroplating is completed, an ethanol dilution solution of hexadecyltrimethoxysilane (HDTMS) is coated on the surface of the electroplating layer, and the glutamic acid-modified electroplated nickel-chromium alloy-based high-hard super-hydrophobic coating is obtained after heating.

[0011] Further, the ethanol dilution solution of HDTMS is a mixed solution of hexadecyltrimethoxysilane (HDTMS) and ethanol with a volume ratio of 1:1-5.

[0012] Further, the constant current density of the electroplating step is 50-100 mA•cm -2 , and the time is 45-75 minutes.

[0013] Further, the power of the ultrasonic step is 100-500 W; the temperature of the heating step is 120-150℃, and the time is 0.5-1 hour.

[0014] The surface of the alumina nanoparticles is modified by glutamic acid, which enhances the hydrophilicity of the surface of the nanoparticles, provides the dispersibility of the nanoparticles in water, and forms negative groups on the surface of the nanoparticles to avoid the agglomeration of the nanoparticles in the aqueous electroplating solution based on the electrostatic repulsion; in the electroplating process, an ultrasonic environment is used to promote the uniform dispersion of the alumina nanoparticles in the nickel-chromium alloy layer, increase the hardness of the nickel-chromium alloy, and improve the surface roughness of the substrate; in the electroplating process, the carboxyl groups of the added glutamic acid form coordination bonds with the nickel-chromium alloy to be fixed on the surface of the alloy; in the subsequent process, the amino groups on the surface of the alumina nanoparticles and the silicon hydroxyl groups generated by the hydrolysis of HDTMS undergo dehydration condensation to form silicon-oxygen-nitrogen bonds; the polar covalent bonds promote the firm combination between the substrate and the hydrophobic film, and a nickel-chromium alloy-based high-hard super-hydrophobic coating with high adhesion is assembled on the surface of the aluminum alloy substrate.

[0015] The glutamic acid-modified electroplated nickel-chromium alloy-based high-hard super-hydrophobic coating prepared by the preparation method.

[0016] In the electroplating process, in addition to the glutamic acid-modified alumina nanoparticles added to the electroplating solution, an appropriate amount of glutamic acid is also added; the nickel and chromium in the nickel-chromium alloy are transition metal ions, which can form coordination bonds with the carboxyl groups of the glutamic acid in the electroplating solution; the glutamic acid can be adsorbed on the surface of the nickel-chromium alloy layer through coordination, that is, the strong coordination ability of the glutamic acid with the aluminum ions and the surface hydroxyl groups of the alumina nanoparticles and the nickel / chromium ions in the nickel-chromium alloy enables the glutamic acid to be firmly and stably fixed on the surface of the substrate; in the process of coating HDTMS, the amino groups on the surface of the alumina nanoparticles and the nickel-chromium alloy layer and the silicon hydroxyl groups generated by the hydrolysis of HDTMS undergo dehydration condensation to form high-energy silicon-oxygen-nitrogen (Si-O-N) bonds; the polar covalent bonds promote the firm combination between the substrate and the hydrophobic film, thereby forming a stable interfacial connection. Based on this, a nickel-chromium alloy-based super-hydrophobic coating with high hardness, wear resistance, and high adhesion is assembled on the surface of the aluminum alloy substrate.

[0017] Compared with the prior art, the present application has the following advantages: The glutamic acid-modified electroplated nickel-chromium alloy-based high-hard super-hydrophobic coating introduces glutamic acid-modified alumina nanoparticles into the alloy coating during the electroplating process; the glutamic acid not only enhances the dispersibility of the alumina nanoparticles in the aqueous electroplating solution to enhance the dispersibility of the nanoparticles in the nickel-chromium alloy layer and strengthen the coordination between the amino groups of the alumina nanoparticles and the subsequently coated HDTMS, but also realizes the interfacial strengthening effect between the nickel-chromium-alumina high-hard coating and HDTMS through the coordination between the amino groups of the nickel-chromium alloy and HDTMS, thereby assembling a super-hydrophobic film with high hardness, wear resistance, and high adhesion.

[0018] The glutamic acid modified electroplated nickel-chromium alloy based high-hard super-hydrophobic coating has important reference value for preparation of firm super-hydrophobic coatings on surfaces of aluminum alloy substrates and other metal substrates, and plays a very key role in surface protection of metal materials, and is favorable for reducing material maintenance cost and prolonging service life. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The hardness value data graph for the embodiment of the present application is shown in the figure, in which a is aluminum alloy control, b is comparative example 1, c is comparative example 2, and d is example 1. Figure 2 The peeling area ratio data graph for the embodiment of the present application is shown in the figure, in which a is comparative example 2, and b is example 1. Figure 3 The water droplet static contact angle data graph for the embodiment of the present application is shown in the figure, in which a is comparative example 1, b is comparative example 2, and c is example 1. DETAILED DESCRIPTION

[0020] Unless defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; and the experimental methods are all conventional methods unless otherwise specified.

[0021] The present application will be described in detail below with reference to examples.

[0022] Example 1 A preparation method of a glutamic acid modified electroplated nickel-chromium alloy based high-hard super-hydrophobic coating, comprising the following steps: (1) glutamic acid and deionized water are mixed at a ratio of 1:100 to obtain a glutamic acid aqueous solution, and aluminum oxide nanoparticles are dispersed in the glutamic acid aqueous solution (the mass ratio of glutamic acid to aluminum oxide nanoparticles is 1:5), NaOH solution is used to adjust the pH of the glutamic acid aqueous solution to about 5, and the mixture is heated and stirred at 50°C for 6 hours, and then centrifuged and washed to remove unbound free glutamic acid, and then dried to obtain glutamic acid modified aluminum oxide nanoparticles; (2) 0.5 M nickel chloride, 0.5 M chromium chloride, 0.3 M sodium citrate, 0.5 M citric acid, 0.1 M glutamic acid, and the glutamic acid modified aluminum oxide nanoparticles are uniformly mixed (the mass concentration of the glutamic acid modified aluminum oxide nanoparticles in the electroplating solution is 2%) to obtain an electroplating solution; (3) aluminum alloy is used as a cathode, and a platinum electrode is used as an anode, and the electroplating solution is electroplated at a current density of 80 mA•cm -2Electroplating was performed at a constant current density for 50 minutes, with an ultrasonic power of 200 W. After electroplating, an ethanol-diluted solution of HDTMS (1:1 volume ratio) was coated onto the sample surface. The coated sample was then spin-coated and heated at 150°C for 1 hour to obtain a high-hardness, wear-resistant, and highly adhesive nickel-chromium alloy-based superhydrophobic coating. The final coating surface had a contact angle of 166°, an adhesion grade of 5B, and a surface hardness of 725.

[0023] Example 2 The only difference from Example 1 is that the constant current density is 100 mA•cm. -2 The electroplating time was 60 minutes, and the ultrasonic power was 300 W. The final coating surface had a contact angle of 165°, an adhesion grade of 5B, and a surface hardness of 720.

[0024] Comparative Example 1 The only difference from Example 1 is that the electroplating solution includes the following components: 0.5 M nickel chloride, 0.5 M chromium chloride, 0.3 M sodium citrate, and 0.5 M citric acid. The final coating surface has a static water droplet contact angle of 143°, a coating hardness of 576, and an adhesion grade of 3B.

[0025] Comparative Example 2 The only difference from Example 1 is that the electroplating solution includes the following components: 0.5 M nickel chloride, 0.5 M chromium chloride, 0.3 M sodium citrate, 0.5 M citric acid, and alumina nanoparticles (the mass concentration of glutamic acid-modified alumina nanoparticles in the electroplating solution is 2%). The final coating surface exhibits a static water droplet contact angle of 155°, an adhesion grade of 4B, and a hardness of 670.

[0026] Comparative Example 3 The only difference from Example 1 is that the mass ratio of glutamic acid to alumina nanoparticles is 2:1, the contact angle of the final coating surface is 160°, the adhesion of the coating is grade 4B, and the surface hardness of the coating is 690.

[0027] like Figure 1 As shown, the hardness of the nickel-chromium alloy layer is improved after electroplating nickel-chromium alloy on the aluminum alloy surface. The embedding of alumina nanoparticles further enhances the hardness of the nickel-chromium alloy layer. The surface hardness distribution of the nickel-chromium alloy coating without glutamate modification of the alumina nanoparticles is uneven, while the embedding of glutamate-modified alumina nanoparticles results in a significant improvement in the hardness value and uniformity of the nickel-chromium alloy layer. Figure 2 As shown, the adhesion of the glutamic acid-modified nickel-chromium alloy / alumina nanoparticle-HDTMS coating interface is significantly improved; Figure 3As shown, the hydrophobic film sample surface hydrophobicity and uniformity of the alumina nanoparticles and nickel-chromium alloy layer are significantly improved after modification by glutamic acid.

[0028] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A modified alumina nanoparticle, characterized by: The modified alumina nanoparticles are obtained by surface modification of alumina nanoparticles with glutamic acid.

2. The modified alumina nanoparticle of claim 1, wherein: The modified alumina nanoparticles are prepared by a method comprising the following steps: dissolving glutamic acid in deionized water, mixing uniformly to obtain a glutamic acid aqueous solution, dispersing alumina nanoparticles in the glutamic acid aqueous solution, adjusting the pH value of the solution, stirring under heating, and after the reaction is completed, centrifuging, washing, and drying to obtain the modified alumina nanoparticles.

3. The modified alumina nanoparticle of claim 2, wherein: The mass ratio of the alumina nanoparticles, glutamic acid, and deionized water is 1-5:0.2-1:100; the particle size of the alumina nanoparticles is 20-100 nm; the temperature of the deionized water is 30-60℃; the pH value is 5-7; the heating temperature is 40-60℃, and the stirring time is 4-10 hours.

4. A nickel-chromium alloy electroplating solution characterized by: The electroplating solution contains the modified alumina nanoparticles according to any one of claims 1-3; the mass concentration of the modified alumina nanoparticles in the electroplating solution is 1-5%.

5. The nickel-chromium alloy electroplating solution of claim 4, wherein: The electrolyte further comprises the following molar concentrations of components: nickel chloride 0.3-0.6 M, chromium chloride 0.3-0.6 M, sodium citrate 0.2-0.4 M, citric acid 0.3-0.5 M, and glutamic acid 0.02-0.1 M.

6. A method for preparing a glutamic acid-modified electroplated nickel-chromium alloy-based high-hardness superhydrophobic coating, characterized in that: The method comprises the following steps: An aluminum alloy is used as the cathode, a platinum electrode is used as the anode, the nickel-chromium alloy electroplating solution according to claim 4 or 5 is used for electroplating under ultrasonic conditions, after the electroplating is completed, an HDTMS ethanol diluent is coated on the surface of the electroplating layer, and after heating, the glutamic acid-modified electroplated nickel-chromium alloy-based high-hard super-hydrophobic coating is obtained.

7. The method of claim 6, wherein the method is characterized by: The HDTMS ethanol diluent is a mixed solution of HDTMS and ethanol in a volume ratio of 1:1-5.

8. The method of claim 6, wherein the method is characterized by: The constant current density of the electroplating step is 50-100 mA•cm -2 , and the time is 45-75 minutes.

9. The method of claim 6, wherein the method is characterized by: The power of the ultrasonic step is 100-500 W; the temperature of the heating step is 120-150℃, and the time is 0.5-1 hour.

10. A glutamic acid-modified electroplated nickel-chromium alloy-based high-hard super-hydrophobic coating prepared by the preparation method according to any one of claims 6-9.

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