Preparation method of nano-particle-doped micro-arc oxidation film layer

Abstract

The invention belongs to the field of material surface treatment, and particularly relates to a preparation method of a nano-particle-doped micro-arc oxidation film layer. According to the method, a nano-particle dispersion liquid based on nano-silica sol is added into a micro-arc oxidation basic electrolyte through a micro-arc oxidation (MAO) technology, and a nano-particle-doped micro-arc oxidation film layer is prepared on the surface of a base material. Nano-silica sol is adopted as a dispersing agent, and through the synergistic effect of the nano-silica sol dispersing agent and the micro-arc oxidation reaction, the technical problems that in a traditional micro-arc oxidation process, nano-particles are difficult to dope, and the growth rate of a film layer is low are solved. By means of the method, different functional nano particles can be effectively doped into the micro-arc oxidation film layer, preparation of multiple functional ceramic film layers is achieved, and the film layers are high in binding force with a base body, high in growth rate, resistant to high temperature, good in insulativity, suitable for industrial batch production and capable of having certain social and economic value.

Description

Technical Field

[0001] The present invention belongs to the field of material surface treatment, and specifically relates to a method for preparing a micro-arc oxidation film doped with nanoparticles, which is applicable to valve metals such as aluminum, magnesium, titanium, tantalum, niobium, zirconium and their alloys or composite materials. Background Art

[0002] Micro-arc oxidation technology (MAO) is a new surface modification technology based on in-situ electrochemical growth. By applying a high voltage on the surface of valve metals such as aluminum, magnesium, titanium and their alloys, micro-area plasma discharge is induced in the electrolyte, causing complex electrochemical, thermodynamic and plasma chemical reactions between the metal matrix and the electrolyte components, and finally a dense ceramic oxide film is in-situ formed on the surface of the matrix. Compared with traditional anodic oxidation, the film formed by micro-arc oxidation has higher hardness, excellent wear resistance, corrosion resistance and insulation performance, and the film and the matrix are metallurgically bonded, with significantly improved bonding strength. At present, this technology has been widely applied in the fields of aerospace engine components, automotive lightweight components, household appliances, laptop computers, robots, semiconductor equipment and biomedical implants, etc.

[0003] However, the traditional micro-arc oxidation electrolyte system (such as silicate, phosphate system) has limitations in improving the performance and functional expansion of the film. On the one hand, the preparation efficiency of the micro-arc oxidation film prepared in the traditional electrolyte system is low, and the growth rate of the film is generally 2-5 μm / min. On the other hand, directly introducing functional nanoparticles (such as AlN, Si3N4, etc.) into the traditional electrolyte system often has strong chemical inertness on the particle surface, making it difficult to form effective charge adsorption with ions (such as OH - 、SiO3 2- etc.) in the electrolyte, so the electrophoretic mobility is extremely low and it is difficult to participate in the micro-arc oxidation reaction. Therefore, designing and developing a process that can not only improve the preparation efficiency of the film but also realize the incorporation of functional nanoparticles has important value for the practical production application of micro-arc oxidation technology. Summary of the Invention

[0004] Aiming at the problems of low film growth rate and difficulty in incorporating functional nanoparticles existing in the existing micro-arc oxidation technology, the purpose of the present invention is to provide a method for preparing a micro-arc oxidation film doped with nanoparticles, which realizes the coordinated regulation of rapid film growth and high-efficiency doping of nanoparticles by optimizing the electrolyte components and the particle surface modification process, and significantly improves the comprehensive performance and preparation efficiency of the film.

[0005] To achieve the above purpose, the technical solution specifically adopted by the present invention is as follows:

[0006] A method for preparing a micro-arc oxidation film doped with nanoparticles, comprising the following steps:

[0007] (1) Substrate surface pretreatment: The substrate is pickled, degreased by ultrasonic wave, and dried.

[0008] (2) Preparation of micro-arc oxidation electrolyte: Under magnetic stirring, the nanoparticle suspension dispersed in nano-silica sol is added to the micro-arc oxidation basic electrolyte to obtain the micro-arc oxidation electrolyte.

[0009] In the micro-arc oxidation electrolyte, the total volume of the micro-arc oxidation electrolyte is 2L, the conductive salts are sodium silicate, sodium hexametaphosphate and sodium hydroxide, and their concentrations are 1-80 g / L, 1-60 g / L and 0.5-20 g / L respectively. The volume fraction of nano-silica sol is 5-50%, the concentration of nanoparticles is 5-50 g / L, and the rest is deionized water.

[0010] (3) Micro-arc oxidation: The substrate after surface pretreatment is put into the micro-arc oxidation electrolyte, and the substrate is subjected to micro-arc oxidation treatment to obtain a micro-arc oxidation film layer doped with nanoparticles.

[0011] In the method for preparing the micro-arc oxidation film layer doped with nanoparticles, in step (1), the substrate is valve metal aluminum, magnesium, titanium, tantalum, niobium, zirconium and their alloys or composite materials.

[0012] In the method for preparing the micro-arc oxidation film layer doped with nanoparticles, in step (2), the preparation process of the nanoparticle suspension is as follows: The nanoparticles are added to the nano-silica sol, and magnetic stirring is carried out for 1-50 h to make them fully dispersed to obtain the nanoparticle suspension.

[0013] In the method for preparing the micro-arc oxidation film layer doped with nanoparticles, in step (2), the parameters of the nano-silica sol are: the SiO2 content is 5-30 wt.%, the average particle size of SiO2 is 5-20 nm, and the pH is 8-10.

[0014] In the method for preparing the micro-arc oxidation film layer doped with nanoparticles, in step (2), the nanoparticles are any one or more of AlN, Si3N4, TiO2, Al2O3, SiC, ZrO2, MoS2, h-BN, TiN, B4C, CeO2, ZnO nano-ceramic particles.

[0015] In the method for preparing the micro-arc oxidation film layer doped with nanoparticles, in step (2), preferably, the concentration of sodium silicate is 20-50 g / L, the concentration of sodium hexametaphosphate is 10-30 g / L, and the concentration of sodium hydroxide is 0.5-5 g / L.

[0016] In the method for preparing the micro-arc oxidation film layer doped with nanoparticles, in step (3), the micro-arc oxidation treatment time is 1-100 min, and the current density is 0.2-50 A / dm 2, with a duty cycle of 2-30% and a frequency of 500-5000 Hz.

[0017] In the method for preparing a micro-arc oxidation film layer doped with nanoparticles, in step (3), diffraction peaks of the doped particles can be observed in the XRD pattern of the micro-arc oxidation film layer prepared on the substrate surface.

[0018] In the method for preparing a micro-arc oxidation film layer doped with nanoparticles, in step (3), the growth rate of the micro-arc oxidation film layer prepared on the substrate surface is 20 μm / min or more.

[0019] The design concept of the present invention is:

[0020] In the prior art, due to the repulsion between the surface charge of functional nanoparticles and electrolyte ions, the mobility is low, and it is difficult for traditional dispersants (such as EDTA, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate) to achieve the synergy of stable particle dispersion and high-speed film layer growth. In micro-arc oxidation, it is difficult for nanoparticles to be incorporated due to charge repulsion, resulting in a low film layer growth rate. The present invention uses nano-silica sol as a dispersant to promote the synergy of nanoparticle doping and film layer growth rate. By introducing nano-silica sol, using the charge adsorption effect of its surface hydroxyl groups (-OH) with nanoparticles and electrolyte ions, the electrophoretic mobility of the particles is significantly improved. At the same time, the silica sol participates in the reaction during the discharge process to generate a silicate matrix, accelerating the growth of the film layer. The core innovation point of the present invention is to use nano-silica sol as a dispersant, and through the synergistic effect of the nano-silica sol dispersant and the micro-arc oxidation reaction, solve the technical problems of difficult nanoparticle doping and low film layer growth rate in the traditional micro-arc oxidation process.

[0021] The present invention forms a new micro-arc oxidation process through a synergistic scheme of dispersant + electrolyte formulation + electrical parameter optimization. Nano-silica sol as a dispersant: improves the electrophoretic mobility of particles through the charge adsorption of surface hydroxyl groups with nanoparticles / electrolyte ions; the silica sol participates in the reaction: the surface hydroxyl groups of nano-silica sol form an effective adsorption with nanoparticles, enhancing the surface charge of the particles, improving the electrophoretic mobility, enabling them to effectively participate in the micro-arc oxidation discharge reaction, and generating a silicate phase during the discharge process, accelerating the growth of the film layer. In addition, the present invention adopts a combination of electrical parameters (duty cycle 2-30%, frequency 500-5000 Hz) and electrolyte components (sodium silicate 1-80 g / L, sodium hexametaphosphate 1-60 g / L, sodium hydroxide 0.5-20 g / L), and at the same time combines the dispersing effect of nano-silica sol to achieve the synergistic regulation of rapid film layer growth and particle doping. The nano-scale SiO2 particles of the silica sol form a composite network structure with the silicate in the electrolyte. The nano-network structure and SiO3 in the electrolyte 2-Synergistic effects are formed to promote the deposition of ceramic phases, prevent agglomeration, and achieve stable dispersion of nanoparticles. This not only improves the dispersibility of nanoparticles but also enhances the conductivity of the electrolyte. Thus, a dispersion and reaction synergy mechanism of nano-silica sol is realized, which is applicable to various nanoparticles such as AlN, Si3N4, SiC, ZrO2, TiO2, and Al2O3.

[0022] The advantages and beneficial effects of the present invention are as follows:

[0023] 1. In the prior art, directly introducing functional nanoparticles often has difficulties because the surface of the particles has strong chemical inertness, making it difficult to form effective charge adsorption with ions in the electrolyte, resulting in low electrophoretic mobility and difficulty in participating in the micro-arc oxidation reaction. In the present invention, through the micro-arc oxidation (MAO) technology, a nanoparticle dispersion solution based on nano-silica sol is added to the basic micro-arc oxidation electrolyte to prepare a micro-arc oxidation film layer doped with nanoparticles on the surface of the substrate. The present invention uses nano-silica sol as a dispersant to uniformly disperse the nanoparticles and effectively combine them with the ions in the electrolyte, enabling the micro-arc oxidation film layer to be doped with various functional nano-ceramic particles, providing a general strategy for doping various nanoparticles in micro-arc oxidation.

[0024] 2. The growth rate of the micro-arc oxidation film layer prepared by the present invention can exceed 20 μm / min, which is 5 to 10 times that of the traditional micro-arc oxidation process under the same electrical parameters. The growth rate of the film layer is significantly improved, greatly enhancing the preparation efficiency of the film layer and effectively saving the energy consumption required for production.

[0025] 3. The film layer prepared by the present invention has high bonding strength with the substrate, high density, and good corrosion resistance and high-temperature resistance.

[0026] 4. By doping nanoparticles with different functions, the present invention can achieve the preparation of different functional ceramic film layers.

[0027] 5. The composite film layer prepared by the method of the present invention can effectively improve the anti-corrosion, insulation, heat conduction, and high-temperature resistance of valve metals such as aluminum, magnesium, and titanium and their alloys, thus meeting the needs of fields such as aerospace, automotive parts, semiconductor equipment, power electronics, household appliances, laptop computers, electronic device packaging, and marine equipment, with a wide range of applications.

[0028] 6. The method of the present invention can effectively incorporate one or multiple functional nanoparticles into the micro-arc oxidation film layer to achieve the preparation of various functional ceramic film layers. The film layer has strong bonding force with the substrate, high growth rate, high temperature resistance, corrosion resistance, and heat shock resistance, and is suitable for industrial mass production, with significant social and economic value. Description of the Drawings

[0029] Figure 1XRD patterns, film thickness and breakdown voltage data of the micro-arc oxidation film layer samples of 6061 aluminum alloy doped with aluminum nitride (AlN) prepared in Example 1 of the present invention and the samples of Comparative Example 1. Among them, (a) XRD pattern, the abscissa 2Theta is the diffraction angle (degree), and the ordinate Intensity is the relative intensity (a.u.); (b) film thickness; (c) breakdown voltage.

[0030] Figure 2 XRD patterns, film thickness and breakdown voltage data of the micro-arc oxidation film layer samples of 6061 aluminum alloy doped with silicon nitride (Si3N4) prepared in Example 2 of the present invention and the samples of Comparative Example 2. Among them, (a) XRD pattern, the abscissa 2Theta is the diffraction angle (degree), and the ordinate Intensity is the relative intensity (a.u.); (b) film thickness; (c) breakdown voltage.

[0031] Figure 3 XRD patterns, film thickness and breakdown voltage data of the micro-arc oxidation film layer of commercially pure titanium doped with aluminum nitride (AlN) prepared in Example 3 of the present invention and the samples of Comparative Example 3. Among them, (a) XRD pattern, the abscissa 2Theta is the diffraction angle (degree), and the ordinate Intensity is the relative intensity (a.u.); (b) film thickness; (c) breakdown voltage.

[0032] Figure 4 XRD patterns, film thickness and breakdown voltage data of the micro-arc oxidation film layer samples of AZ31b magnesium alloy doped with aluminum nitride (AlN) prepared in Example 4 of the present invention and the samples of Comparative Example 4. Among them, (a) XRD pattern, the abscissa 2Theta is the diffraction angle (degree), and the ordinate Intensity is the relative intensity (a.u.); (b) film thickness; (c) breakdown voltage.

[0033] Figure 5 XRD patterns, film thickness and breakdown voltage data of the micro-arc oxidation film layer samples of 6061 aluminum alloy co-doped with aluminum nitride (AlN) and silicon nitride (Si3N4) prepared in Example 5 of the present invention and the samples of Comparative Example 5. Among them, (a) XRD pattern, the abscissa 2Theta is the diffraction angle (degree), and the ordinate Intensity is the relative intensity (a.u.); (b) film thickness; (c) breakdown voltage. Detailed implementation manners

[0034] In the specific implementation process, the present invention proposes a method for preparing a micro-arc oxidation film layer doped with nanoparticles, including the following steps:

[0035] (1) Substrate surface pretreatment: The substrate is pickled, degreased by ultrasonic cleaning, and dried to remove the surface oxide layer and oil stains, thereby improving the adhesion of the subsequent film layer.

[0036] (2) Preparation of the basic electrolyte: A nanoparticle suspension dispersed in nano-silica sol is added to the basic electrolyte to obtain a micro-arc oxidation electrolyte. Among them, the parameters of the nano-silica sol are: the SiO2 content is 5 - 30 wt.%, the average particle size of SiO2 is 5 - 20 nm, and the pH is 8 - 10.

[0037] (3) Micro-arc oxidation: The substrate after surface pretreatment is placed in the micro-arc oxidation electrolyte, and the substrate is subjected to micro-arc oxidation treatment to obtain a micro-arc oxidation film layer doped with nanoparticles.

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Example 1

[0040] In this example, a method for preparing a micro-arc oxidation film layer doped with nanoparticles (the substrate in this example is 6061 aluminum alloy) includes the following steps:

[0041] (1) Pretreatment of the aluminum alloy sheet: First, ultrasonically clean in acetone for 8 minutes to remove the oil stains on the surface, then place it in an acidic solution H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 60 seconds to remove the oxide film and impure contaminants on the substrate surface, and finally ultrasonically clean in alcohol for 5 minutes and then dry in an oven at 60 °C.

[0042] (2) Preparation of the micro-arc oxidation basic electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container containing 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0043] (3) Preparation of the nanoparticle suspension: Add 15 g of AlN nanoparticles to 200 ml of nano-silica sol, and stir magnetically for 6 hours to disperse them fully to obtain a suspension. Among them, the parameters of the nano-silica sol are: the SiO2 content is 30 wt.%, the average particle size of SiO2 is 9.6 nm, and the pH is 9.55.

[0044] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and stir magnetically for 1 hour to mix them fully to obtain a micro-arc oxidation electrolyte.

[0045] (5) Micro-arc oxidation surface treatment: Place the aluminum alloy sheet treated in step (1) into the electrolyte prepared in step (4). Set the power supply in the constant current mode and perform micro-arc oxidation treatment for 5 minutes to obtain the sample in Example 1. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0046] Example 2

[0047] In this example, a method for preparing a micro-arc oxidation film layer doped with nanoparticles (the substrate in this example is 6061 aluminum alloy) includes the following steps:

[0048] (1) Pretreatment of aluminum alloy sheet: First, ultrasonically clean in acetone for 6 minutes to remove surface oil stains. Then, place it in an acidic solution H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 30 seconds to remove the oxide film and impure contaminants on the substrate surface. Finally, put it into alcohol, ultrasonically clean for 5 minutes, and then dry in an oven at 60 °C.

[0049] (2) Prepare the basic micro-arc oxidation electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container containing 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0050] (3) Prepare the nanoparticle suspension: Add 15 g of Si3N4 nanoparticles to 200 ml of nano-silica sol, and stir magnetically for 6 hours to fully disperse it to obtain a suspension. Among them, the parameters of the nano-silica sol are: the SiO2 content is 30 wt.%, the average particle size of SiO2 is 9.6 nm, and the pH is 9.55.

[0051] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and stir magnetically for 1 hour to fully mix them to obtain the micro-arc oxidation electrolyte.

[0052] (5) Micro-arc oxidation surface treatment: Place the aluminum alloy sheet treated in step (1) into the electrolyte prepared in step (4). Set the power supply in the constant current mode and perform micro-arc oxidation treatment for 5 minutes to obtain the sample in Example 2. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0053] Example 3

[0054] In this example, a method for preparing a micro-arc oxidation film layer doped with nanoparticles (the substrate in this example is commercially pure titanium) includes the following steps:

[0055] (1) Pretreatment of titanium sheet: First, ultrasonically clean in acetone for 7 min to remove surface oil stains. Then, place it in an acidic solution of H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 90 s to remove the oxide film and impure contaminants on the substrate surface. Finally, put it into alcohol for ultrasonic cleaning for 5 min and then dry it in an oven at 60 °C.

[0056] (2) Preparation of micro-arc oxidation basic electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container filled with 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0057] (3) Preparation of nanoparticle suspension: Add 15 g of AlN nanoparticles to 200 ml of nano-silica sol, and stir magnetically for 6 h to fully disperse them to obtain a suspension. Among them, the parameters of the nano-silica sol are: the SiO2 content is 30 wt.%, the average particle size of SiO2 is 9.6 nm, and the pH is 9.55.

[0058] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and stir magnetically for 1 h to fully mix them to obtain the micro-arc oxidation electrolyte.

[0059] (5) Micro-arc oxidation surface treatment: Place the titanium sheet treated in step (1) in the electrolyte prepared in step (4), set the power supply in the constant current mode, and perform micro-arc oxidation treatment for 5 min to obtain the sample in Example 3. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0060] Example 4

[0061] In this example, a method for preparing a micro-arc oxidation film layer doped with nanoparticles (the substrate in this example is AZ31b magnesium alloy) includes the following steps:

[0062] (1) Pretreatment of magnesium alloy sheet: First, ultrasonically clean in acetone for 10 min to remove surface oil stains. Then, place it in an acidic solution of H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 60 s to remove the oxide film and impure contaminants on the substrate surface. Finally, put it into alcohol for ultrasonic cleaning for 5 min and then dry it in an oven at 60 °C.

[0063] (2) Preparation of micro-arc oxidation basic electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container filled with 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0064] (3) Preparation of nanoparticle suspension: Add 15 g of AlN nanoparticles into 200 ml of nano-silica sol, and magnetically stir for 6 h to fully disperse them to obtain a suspension. Among them, the parameters of the nano-silica sol are: the SiO2 content is 30 wt.%, the average particle size of SiO2 is 9.6 nm, and the pH is 9.55.

[0065] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and magnetically stir for 1 h to fully mix them to obtain a micro-arc oxidation electrolyte.

[0066] (5) Micro-arc oxidation surface treatment: Place the magnesium alloy sheet treated in step (1) into the electrolyte prepared in step (4), set the power supply in the constant current mode, and perform micro-arc oxidation treatment for 5 min to obtain the sample in Example 4. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0067] Example 5

[0068] In this example, a method for preparing a micro-arc oxidation film layer doped with nanoparticles (the substrate in this example is 6061 aluminum alloy) includes the following steps:

[0069] (1) Pretreatment of aluminum alloy sheet: First, ultrasonically clean in acetone for 8 min to remove surface oil stains, then place it in an acidic solution H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 60 s to remove the oxide film and impure contaminants on the substrate surface, and finally put it into alcohol for ultrasonic cleaning for 5 min and then dry it in an oven at 60 °C.

[0070] (2) Preparation of micro-arc oxidation basic electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide into a container filled with 1.8 L of deionized water in sequence, and then magnetically stir until completely dissolved.

[0071] (3) Preparation of nanoparticle suspension: Add 10 g of AlN nanoparticles and 10 g of Si3N4 nanoparticles into 200 ml of nano-silica sol, and magnetically stir for 6 h to fully disperse them to obtain a suspension. Among them, the parameters of the nano-silica sol are: the SiO2 content is 30 wt.%, the average particle size of SiO2 is 9.6 nm, and the pH is 9.55.

[0072] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and magnetically stir for 1 h to fully mix them to obtain a micro-arc oxidation electrolyte.

[0073] (5) Micro-arc oxidation surface treatment: Place the aluminum alloy sheet treated in step (1) into the electrolyte prepared in step (4). Set the power supply in the constant current mode and perform micro-arc oxidation treatment for 5 minutes to obtain the sample in Example 5. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0074] To better illustrate the technical effects brought by preparing the composite film layer doped with nanoparticles by micro-arc oxidation in the present invention, a comparative example is used for comparison.

[0075] Comparative Example 1

[0076] In this comparative example, the nano-silica sol in the suspension preparation is replaced with deionized water, and the micro-arc oxidation film layer of 6061 aluminum alloy doped with aluminum nitride is used as a comparative sample. The preparation steps are as follows:

[0077] (1) Pretreatment of aluminum alloy sheet: First, ultrasonically clean in acetone for 8 minutes to remove surface oil stains, then place it in an acidic solution H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 60 seconds to remove the oxide film and impurity contaminants on the substrate surface. Finally, put it into alcohol, ultrasonically clean for 5 minutes, and then dry it in an oven at 60 °C.

[0078] (2) Prepare the basic micro-arc oxidation electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container containing 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0079] (3) Prepare the nanoparticle suspension: Add 15 g of AlN nanoparticles to 200 ml of deionized water and stir magnetically for 6 hours to make it fully dispersed to obtain a suspension.

[0080] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3) and stir magnetically for 1 hour to make them fully mixed to obtain the micro-arc oxidation electrolyte.

[0081] (5) Micro-arc oxidation surface treatment: Place the aluminum alloy sheet treated in step (1) into the electrolyte prepared in step (4). Set the power supply in the constant current mode and perform micro-arc oxidation treatment for 5 minutes to obtain the sample in Comparative Example 1. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0082] Comparative Example 2

[0083] In this comparative example, the nano-silica sol in the suspension preparation was replaced with deionized water to prepare a micro-arc oxidation film of 6061 aluminum alloy doped with silicon nitride as a comparative sample. The preparation steps are as follows:

[0084] (1) Pretreatment of aluminum alloy sheet: First, ultrasonically clean in acetone for 6 minutes to remove surface oil stains, then place it in an acidic solution of H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 30 seconds to remove the oxide film and impure contaminants on the substrate surface. Finally, put it into alcohol, ultrasonically clean for 5 minutes, and then dry in an oven at 60 °C.

[0085] (2) Prepare the basic micro-arc oxidation electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container containing 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0086] (3) Prepare the nano-particle suspension: Add 15 g of Si3N4 nano-particles to 200 ml of deionized water, and stir magnetically for 6 hours to fully disperse them to obtain a suspension.

[0087] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and stir magnetically for 1 hour to fully mix them to obtain the micro-arc oxidation electrolyte.

[0088] (5) Micro-arc oxidation surface treatment: Place the aluminum alloy sheet treated in step (1) in the electrolyte prepared in step (4). Set the power supply in the constant current mode and perform micro-arc oxidation treatment for 5 minutes to obtain the sample in Comparative Example 2. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0089] Comparative Example 3

[0090] In this comparative example, the nano-silica sol in the suspension preparation was replaced with deionized water to prepare a micro-arc oxidation film of commercially pure titanium doped with aluminum nitride as a comparative sample. The preparation steps are as follows:

[0091] (1) Pretreatment of titanium sheet: First, ultrasonically clean in acetone for 7 minutes to remove surface oil stains, then place it in an acidic solution of H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 90 seconds to remove the oxide film and impure contaminants on the substrate surface. Finally, put it into alcohol, ultrasonically clean for 5 minutes, and then dry in an oven at 60 °C.

[0092] (2) Prepare the basic micro-arc oxidation electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container containing 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0093] (3) Preparation of nanoparticle suspension: Add 15 g of AlN nanoparticles into 200 ml of deionized water, and stir magnetically for 6 h to fully disperse them to obtain a suspension.

[0094] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and stir magnetically for 1 h to fully mix them to obtain a micro-arc oxidation electrolyte.

[0095] (5) Micro-arc oxidation surface treatment: Place the titanium sheet treated in step (1) into the electrolyte prepared in step (4), set the power supply in the constant current mode, and perform micro-arc oxidation treatment for 5 min to obtain the sample in Comparative Example 3. Among them, the current density is 2 A / dm 2 , the duty cycle is 10%, the frequency is 1000 Hz, and the electrolyte temperature is controlled at 25 °C.

[0096] Comparative Example 4

[0097] In this comparative example, the nano-silica sol in the preparation of the suspension is replaced by deionized water, and the micro-arc oxidation film layer of AZ31b magnesium alloy doped with aluminum nitride is used as a comparative sample. The preparation steps are as follows:

[0098] (1) Pretreatment of magnesium alloy sheet: First, ultrasonically clean in acetone for 10 min to remove surface oil stains, then place it in an acidic solution H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 60 s to remove the oxide film and impure contaminants on the substrate surface. Finally, put it into alcohol, ultrasonically clean for 5 min, and then dry it in an oven at 60 °C.

[0099] (2) Preparation of micro-arc oxidation basic electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide into a container filled with 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0100] (3) Preparation of nanoparticle suspension: Add 15 g of AlN nanoparticles into 200 ml of deionized water, and stir magnetically for 6 h to fully disperse them to obtain a suspension.

[0101] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3), and stir magnetically for 1 h to fully mix them to obtain a micro-arc oxidation electrolyte.

[0102] (5) Micro-arc oxidation surface treatment: Place the magnesium alloy sheet treated in step (1) into the electrolyte prepared in step (4), set the power supply in the constant current mode, and perform micro-arc oxidation treatment for 5 min to obtain the sample in Comparative Example 4. Among them, the current density is 2 A / dm 2, with a duty cycle of 10%, a frequency of 1000 Hz, and the electrolyte temperature controlled at 25°C.

[0103] Comparative Example 5

[0104] In this comparative example, the nano-silica sol in the suspension preparation was replaced with deionized water, and a micro-arc oxidation film layer of 6061 aluminum alloy co-doped with aluminum nitride and silicon nitride was prepared as a comparative sample. The preparation steps are as follows:

[0105] (1) Pretreatment of aluminum alloy sheet: First, ultrasonically clean in acetone for 8 min to remove surface oil stains, then place it in an acidic solution of H2O:HNO3:HF = 5:4:1 (volume ratio) at room temperature for 60 s to remove the oxide film and impure contaminants on the substrate surface. Finally, put it into alcohol for ultrasonic cleaning for 5 min and then dry it in an oven at 60°C.

[0106] (2) Prepare the basic micro-arc oxidation electrolyte: Add 60 g of sodium silicate, 20 g of sodium hexametaphosphate, and 4 g of sodium hydroxide to a container containing 1.8 L of deionized water in sequence, and then stir magnetically until completely dissolved.

[0107] (3) Prepare the nano-particle suspension: Add 10 g of AlN nano-particles and 10 g of Si3N4 nano-particles to 200 ml of deionized water, and stir magnetically for 6 h to fully disperse them to obtain a suspension.

[0108] (4) Mix the basic electrolyte prepared in step (2) and the suspension prepared in step (3) and stir magnetically for 1 h to fully mix them to obtain the micro-arc oxidation electrolyte.

[0109] (5) Micro-arc oxidation surface treatment: Place the aluminum alloy sheet treated in step (1) in the electrolyte prepared in step (4), set the power supply in the constant current mode, and perform micro-arc oxidation treatment for 5 min to obtain the sample in Comparative Example 5. Among them, the current density is 2 A / dm 2 , with a duty cycle of 10%, a frequency of 1000 Hz, and the electrolyte temperature controlled at 25°C.

[0110] As Figure 1 (a) shows the XRD patterns of the 6061 aluminum alloy micro-arc oxidation doped aluminum nitride composite film layer prepared by the method of Example 1 and the sample of Comparative Example 1. It can be seen that obvious aluminum nitride diffraction peaks can be observed in the XRD pattern of Example 1, and almost no aluminum nitride diffraction peaks can be seen in the XRD pattern of the sample of Comparative Example 1.

[0111] As Figure 1(b), thickness comparison between the micro-arc oxidation doped aluminum nitride composite coating on 6061 aluminum alloy prepared by the method of Example 1 and the sample of Comparative Example 1; it can be seen from the figure that the thickness of the sample of Example 1 is 105.92 μm, and its growth rate is higher than that of the sample of Comparative Example 1, reaching 21.18 μm / min.

[0112] As Figure 1 (c), breakdown voltage comparison between the micro-arc oxidation doped aluminum nitride composite coating on 6061 aluminum alloy prepared by the method of Example 1 and the sample of Comparative Example 1; it can be seen from the figure that the breakdown voltage of the sample of Example 1 is 1086.7 V, much higher than 193.3 V of the sample of Comparative Example 1, indicating that it has better insulation performance.

[0113] As Figure 2 (a), XRD patterns of the micro-arc oxidation doped silicon nitride composite coating on 6061 aluminum alloy prepared by the method of Example 2 and the sample of Comparative Example 2. It can be seen from the figure that obvious silicon nitride diffraction peaks can be observed in the XRD pattern of the sample of Example 2, while almost no silicon nitride diffraction peaks can be seen in the XRD pattern of the sample of Comparative Example 2.

[0114] As Figure 2 (b), thickness comparison between the micro-arc oxidation doped silicon nitride composite coating on 6061 aluminum alloy prepared by the method of Example 2 and the sample of Comparative Example 2; it can be seen from the figure that the thickness of the sample of Example 2 is 104.29 μm, and its growth rate is higher than that of the sample of Comparative Example 2, reaching 20.86 μm / min.

[0115] As Figure 2 (c), breakdown voltage comparison between the micro-arc oxidation doped silicon nitride composite coating on 6061 aluminum alloy prepared by the method of Example 2 and the sample of Comparative Example 2; it can be seen from the figure that the breakdown voltage of the sample of Example 2 is 1040 V, much higher than 196.7 V of the sample of Comparative Example 2, indicating that it has better insulation performance.

[0116] As Figure 3 (a), XRD patterns of the micro-arc oxidation doped aluminum nitride composite coating on commercially pure titanium prepared by the method of Example 3 and the sample of Comparative Example 3. It can be seen from the figure that obvious aluminum nitride diffraction peaks can be observed in the XRD pattern of the sample of Example 3, while almost no aluminum nitride diffraction peaks can be seen in the XRD pattern of the sample of Comparative Example 3.

[0117] As Figure 3 (b), thickness comparison between the micro-arc oxidation doped aluminum nitride composite coating on commercially pure titanium prepared by the method of Example 3 and the sample of Comparative Example 3; it can be seen from the figure that the thickness of the sample of Example 3 is 86.29 μm, and its growth rate is higher than that of the sample of Comparative Example 3, reaching 17.26 μm / min.

[0118] As Figure 3 (c) shows the comparison of the breakdown voltages between the commercial pure titanium micro-arc oxidation doped aluminum nitride composite film prepared by the method of Example 3 and the sample of Comparative Example 3; it can be seen from the figure that the breakdown voltage of the sample of Example 3 is 870V, much higher than 220V of the sample of Comparative Example 3, indicating that it has more excellent insulation performance.

[0119] As Figure 4 (a) shows the XRD patterns of the AZ31b magnesium alloy micro-arc oxidation doped aluminum nitride composite film prepared by the method of Example 4 and the sample of Comparative Example 4. It can be seen from this that obvious aluminum nitride diffraction peaks can be observed in the XRD pattern of the sample of Example 4, while almost no aluminum nitride diffraction peaks can be seen in the XRD pattern of the sample of Comparative Example 4.

[0120] As Figure 4 (b) shows the comparison of the thicknesses between the AZ31b magnesium alloy micro-arc oxidation doped aluminum nitride composite film prepared by the method of Example 4 and the sample of Comparative Example 4; it can be seen from the figure that the thickness of the sample of Example 4 is 71.02μm, and its growth rate is higher than that of the sample of Comparative Example 4, reaching 14.20μm / min.

[0121] As Figure 4 (c) shows the comparison of the breakdown voltages between the AZ31b magnesium alloy micro-arc oxidation doped aluminum nitride composite film prepared by the method of Example 4 and the sample of Comparative Example 4; it can be seen from the figure that the breakdown voltage of the sample of Example 4 is 610V, much higher than 143.3V of the sample of Comparative Example 4, indicating that it has more excellent insulation performance.

[0122] As Figure 5 (a) shows the XRD patterns of the 6061 aluminum alloy micro-arc oxidation co-doped aluminum nitride and silicon nitride composite film prepared by the method of Example 5 and the sample of Comparative Example 5. It can be seen from this that obvious aluminum nitride and silicon nitride diffraction peaks can be observed in the XRD pattern of the sample of Example 5, while almost no aluminum nitride diffraction peaks can be seen in the XRD pattern of the sample of Comparative Example 5.

[0123] As Figure 5 (b) shows the comparison of the thicknesses between the 6061 aluminum alloy micro-arc oxidation co-doped aluminum nitride and silicon nitride composite film prepared by the method of Example 5 and the sample of Comparative Example 5; it can be seen from the figure that the thickness of the sample of Example 5 is 105.96μm, and its growth rate is higher than that of the sample of Comparative Example 5, reaching 21.20μm / min.

[0124] As Figure 5As shown in (c), comparison of the breakdown voltages of the micro-arc oxidation co-doped aluminum nitride and silicon nitride composite film prepared by the method of Example 5 and the sample of Comparative Example 5; it can be seen from the figure that the breakdown voltage of the sample of Example 5 is 1113.3 V, much higher than 206.7 V of the sample of Comparative Example, indicating that it has more excellent insulation performance.

[0125] It can be seen from the above examples, comparative examples and drawings that Comparative Examples 1-5 show that when deionized water is used to replace silica sol, almost no nanoparticles are incorporated and the growth rate is only at the traditional level, proving that the dual functions of silica sol (dispersant + reactant) play a key role. The film thicknesses of Examples 1-5 using the method of the present invention reach 71-106 μm, the growth rate reaches 14-22 μm / min, and the treatment time is only 5 min. It can effectively introduce nanoparticles into the micro-arc oxidation film layer, the doping amount of nanoparticles is significantly increased (XRD shows obvious characteristic peaks of AlN / Si3N4), and the growth rate and breakdown voltage of the film layer are increased, improving the production efficiency and promising large-scale production in industry.

[0126] The above are only the optimal implementation modes listed in the present invention. It should be pointed out that for all those skilled in the art of this technology, without departing from the spirit of the appended claims and the principles shown in the present invention, the shown embodiments can also be changed or altered, and these changes should also be regarded as the scope of the rights protected by the present invention.

Claims

1. A method for preparing a micro-arc oxidation film layer doped with nanoparticles, characterized in that, It includes the following steps: (1) Substrate surface pretreatment: The substrate is pickled, degreased by ultrasonic wave, and dried; (2) Preparation of micro-arc oxidation electrolyte: Under magnetic stirring, the nanoparticle suspension dispersed in nano-silica sol is added to the micro-arc oxidation basic electrolyte to obtain the micro-arc oxidation electrolyte; In the micro-arc oxidation electrolyte, the total volume of the micro-arc oxidation electrolyte is 2L, the conductive salts are sodium silicate, sodium hexametaphosphate and sodium hydroxide, and the concentrations are 1-80g / L, 1-60g / L and 0.5-20g / L respectively. The volume fraction of nano-silica sol is 5-50%, the concentration of nanoparticles is 5-50g / L, and the rest is deionized water; (3) Micro-arc oxidation: The substrate after surface pretreatment is put into the micro-arc oxidation electrolyte, and the substrate is subjected to micro-arc oxidation treatment to obtain a micro-arc oxidation film layer doped with nanoparticles.

2. The preparation method of the micro-arc oxidation film layer doped with nanoparticles according to claim 1, characterized in that, In step (1), the substrate is valve metal aluminum, magnesium, titanium, tantalum, niobium, zirconium and their alloys or composite materials.

3. The preparation method of the micro-arc oxidation film layer doped with nanoparticles according to claim 1, characterized in that, In step (2), the preparation process of the nanoparticle suspension is as follows: The nanoparticles are added to the nano-silica sol, and magnetic stirring is carried out for 1-50h to make them fully dispersed to obtain the nanoparticle suspension.

4. The preparation method of the micro-arc oxidation film layer doped with nanoparticles according to claim 1 or 3, characterized in that, In step (2), the parameters of the nano-silica sol are: the SiO2 content is 5-30wt.%, the average particle size of SiO2 is 5-20nm, and the pH is 8-10.

5. The preparation method of the micro-arc oxidation film layer doped with nanoparticles according to claim 1 or 3, characterized in that, In step (2), the nanoparticles are any one or more of AlN, Si3N4, TiO2, Al2O3, SiC, ZrO2, MoS2, h-BN, TiN, B4C, CeO2, ZnO nano-ceramic particles.

6. The preparation method of the micro-arc oxidation film layer doped with nanoparticles according to claim 1, wherein, In step (2), preferably, the concentration of sodium silicate is 20-50g / L, the concentration of sodium hexametaphosphate is 10-30g / L, and the concentration of sodium hydroxide is 0.5-5g / L.

7. The method for preparing a micro-arc oxidation film layer doped with nanoparticles according to claim 1, wherein, In step (3), the micro-arc oxidation treatment time is 1 to 100 min, the current density is 0.2 to 50 A / dm 2 , the duty cycle is 2 to 30%, and the frequency is 500 to 5000 Hz.

8. The preparation method of the micro-arc oxidation film layer doped with nanoparticles according to claim 1, characterized in that, In step (3), the diffraction peak of the doped particles can be observed in the XRD pattern of the micro-arc oxidation film layer prepared on the substrate surface.

9. The preparation method of the micro-arc oxidation film layer doped with nanoparticles according to claim 1, characterized in that, In step (3), the growth rate of the micro-arc oxidation film layer prepared on the substrate surface is above 20μm / min.

Images