Method for solving agglomeration of nanoparticles in micro-arc oxidation electrolyte

Abstract

The invention discloses a method for solving agglomeration of nano-particles in micro-arc oxidation electrolyte, which comprises the following steps: firstly, carrying out polishing and phosphoric acid pretreatment on a magnesium alloy sample, and then carrying out anodic electrodeposition in ethanol-based electrolyte containing nano titanium dioxide by taking the magnesium alloy sample as an anode, so that the nano-particles are fixed on the surface of a matrix in advance; and then taking the sample deposited with the nano-particles as an anode, and performing micro-arc oxidation treatment in silicate electrolyte to finally obtain the micro-arc oxidation ceramic layer containing the uniformly dispersed nano-particles. Through a composite process of anodic electrodeposition and micro-arc oxidation, the problem of agglomeration of nanoparticles in a micro-arc oxidation electrolyte is fundamentally avoided, and the defects of high energy consumption, complex process, non-repeated use of the electrolyte and the like in a traditional ultrasonic stirring and surface modification method are overcome; the method has the characteristics of simplicity and convenience in operation, energy conservation, environment friendliness, excellent film performance and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of metal material surface treatment technology, especially a kind of method for solving the agglomeration of nano particles in micro-arc oxidation electrolyte, it is applicable to the surface strengthening treatment of magnesium alloy and other valve metals. BACKGROUND

[0002] At present, valve metal is irreplaceable in high-end industry, medical treatment, electronics and other fields due to its lightweight, good biocompatibility and other unique properties. However, the problems of corrosion resistance and hardness greatly limit the widespread use of valve metals. Micro-arc oxidation technology is often used for surface treatment of valve metals. The ceramic film layer generated on the surface of valve metal improves the performance of the film layer, but the performance of the generated film layer is single and cannot be widely used.

[0003] In current research, many researchers add nano particles such as aluminum oxide, zinc oxide and silicon dioxide to the micro-arc oxidation electrolyte to improve the comprehensive performance of the film layer. However, the agglomeration problem of nano particles in the electrolyte has not been effectively solved. At present, the methods to solve the agglomeration of nano particles in the micro-arc oxidation electrolyte are basically divided into two types: (1) ultrasonic stirring; (2) surface modification of nano particles. Both of these two traditional methods have certain defects. The method of ultrasonic stirring requires a large amount of energy. During the entire experiment, the ultrasonic and stirring instruments need to be turned on at the same time, which generates a large amount of energy and requires high heat dissipation of the entire instrument. Moreover, this method has a large loss of chemicals, and the electrolyte after the experiment cannot be reused, which violates the purpose of energy saving and emission reduction. The method of surface modification of nano particles requires the introduction of the same functional groups on the surface of nano particles to repel each other, thereby achieving dispersion effect. This method is complex to operate. The selection of introduced functional groups, the conditions of surface modification (temperature, pH and time), and whether the introduced functional groups have an impact on the micro-arc oxidation electrolyte need to be constantly explored to achieve the target effect. This method is time-consuming and labor-intensive, and is not suitable for widespread use.

[0004] In addition, in the existing patent literature, there is also a process of "electrodeposition first and then micro-arc oxidation" to solve other technical problems. However, these existing technologies usually use "cathodic electrodeposition" as a pretreatment step, which aims to deposit a layer of metal or alloy coating on the surface of the workpiece before micro-arc oxidation. This "cathodic electrodeposition + micro-arc oxidation" process is fundamentally different from the "anodic electrodeposition + micro-arc oxidation" of the present application in principle, treatment object and technical effect. Cathodic electrodeposition is a conventional technical means in the field of electrodeposition, while electrodeposition of valve metals (such as magnesium alloy) as anode is not a conventional method, because anode process usually leads to dissolution of the base metal, which is not conducive to the formation of coating.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte, to solve the above technical problems existing in the prior art.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte of the present application comprises the following steps:

[0009] S1 cut the magnesium alloy into a cube with a side length of 1 cm, drill a hole with a depth of 1 cm on the side of the cube, polish the sample on a grinding and polishing machine to 400#, 800#, 1000# and 1200#, wash the surface stains with deionized water, and dry with anhydrous ethanol to obtain a standby sample;

[0010] Soak the standby sample in a (1-3) wt% phosphoric acid solution for 30-50 seconds to obtain a pretreated magnesium alloy sample;

[0011] S2 use the pretreated magnesium alloy sample as an anode, fix it on the clamp of the electrodeposition equipment, use a titanium plate or a graphite plate as a cathode, and put it into an electrolyte containing nano-titanium dioxide;

[0012] Adjust the electrodeposition process parameters and perform electrodeposition treatment;

[0013] S3 after the electrodeposition is completed, take out the magnesium alloy sample from the electrolyte, put it into an oven for drying, and obtain a magnesium alloy film layer sample containing nanoparticles;

[0014] S4 use the magnesium alloy film layer sample containing nanoparticles as an anode, fix it on the clamp of the micro-arc oxidation equipment, use a stainless steel plate as a cathode, put it into an electrolytic tank containing a silicate electrolyte, adjust the micro-arc oxidation process parameters, and perform micro-arc oxidation;

[0015] After the micro-arc oxidation is completed, take out the magnesium alloy film layer sample containing nanoparticles from the electrolyte, rinse it with deionized water and anhydrous ethanol respectively, and dry it with a hair dryer to obtain a micro-arc oxidation magnesium alloy film layer containing nanoparticles.

[0016] Compared with the prior art, the method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte provided by the present application fundamentally avoids the agglomeration of nanoparticles in the electrolyte through the composite process of "anode electrodeposition + micro-arc oxidation", overcomes the defects of high energy consumption, complex process, and non-reusable electrolyte existing in the traditional ultrasonic stirring and surface modification method, and has the characteristics of simple operation, energy saving and environmental protection, excellent film layer performance, etc. BRIEF DESCRIPTION OF DRAWINGS ​

[0017] Figure 1 The flow chart of the method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte provided by the embodiment of the present application;

[0018] Figure 2 is the SEM image of the surface of the magnesium alloy without electrodeposition;

[0019] Figure 3 is the SEM image of the surface of the magnesium alloy with electrodeposition;

[0020] Figure 4 is the SEM and EDS images of the magnesium alloy with electrodeposited nano-TiO2 after micro-arc oxidation;

[0021] Figure 5 is the XRD images of the two groups of samples with and without electrodeposition. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application, which do not constitute a limitation of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0023] Firstly, the terms possibly used in the present application are described as follows:

[0024] The terms “include”, “contain”, “have”, “possess” or other similar semantic descriptions should be interpreted as non-exclusive inclusion.

[0025] The term “consist of” means excluding any technical feature elements not explicitly listed. If this term is used in the claims, the term will make the claim closed, so that it does not contain technical feature elements other than the explicitly listed technical feature elements, but the conventional impurities related thereto are excluded. If the term only appears in a certain clause of the claim, it is only limited to the elements explicitly listed in this clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0026] The contents not described in detail in the embodiments of the present application belong to the prior art known to those skilled in the art. If the specific conditions are not indicated in the embodiments of the present application, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used in the embodiments of the present application are not indicated by the manufacturer, they are all conventional products that can be obtained by market purchase.

[0027] The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte of the present application comprises the following steps:

[0028] S1 cutting the magnesium alloy into a cube with a side length of 1 cm, drilling a hole with a depth of 1 cm on the side of the cube, polishing the sample on a grinding and polishing machine to 400#, 800#, 1000# and 1200#, washing the surface stains with deionized water, drying with anhydrous ethanol to obtain a standby sample;

[0029] immersing the standby sample in a (1-3) wt% phosphoric acid solution for 30-50 seconds to obtain a pretreated magnesium alloy sample;

[0030] S2 fixing the pretreated magnesium alloy sample as an anode on a clamp of an electrodeposition device, taking a titanium plate or a graphite plate as a cathode, and placing them into an electrolyte containing nano-titanium dioxide;

[0031] adjusting the electrodeposition process parameters to perform electrodeposition treatment;

[0032] S3 after the electrodeposition is completed, taking the magnesium alloy sample out of the electrolyte and placing it into an oven for drying to obtain a magnesium alloy film layer sample containing nano-particles;

[0033] S4 fixing the magnesium alloy film layer sample containing nano-particles as an anode on a clamp of a micro-arc oxidation device, taking a stainless steel plate as a cathode, and placing them into an electrolytic tank containing a silicate electrolyte, adjusting the micro-arc oxidation process parameters to perform micro-arc oxidation;

[0034] after the micro-arc oxidation is completed, taking the magnesium alloy film layer sample containing nano-particles out of the electrolyte, respectively washing it with deionized water and anhydrous ethanol, and drying it with a hair dryer to obtain a micro-arc oxidation magnesium alloy film layer containing nano-particles.

[0035] The electrolyte containing nano-titanium dioxide in step S2 is an ethanol solution with a water-free ethanol to deionized water ratio of 4:1, and the solution contains 0.001-0.005 parts by mass of sodium dodecyl sulfate and 0.1-0.5 parts by mass of titanium dioxide.

[0036] The configuration method of the electrolyte containing nano-titanium dioxide in step S2 is as follows: first, sodium dodecyl sulfate is added to the ethanol solution and stirred until it is completely dissolved, then nano-titanium dioxide is slowly added to the ethanol solution while continuously stirring to make it fully dispersed, thereby obtaining the electrodeposition electrolyte containing nano-titanium dioxide.

[0037] In step S2, the electrodeposition process parameters are as follows: in the constant voltage mode, the voltage is 6-10 V, and the deposition time is 5-10 minutes.

[0038] The silicate electrolyte in step S4 contains 6-18 parts by mass of sodium silicate, 3-9 parts by mass of sodium hydroxide and 2-4 parts by mass of glycerol.

[0039] ​The micro-arc oxidation electric parameters in step S4 are: in constant current mode, current is 1-3A, pulse frequency is 500-1000Hz, duty cycle is 20-40%, and oxidation time is 10-30 minutes.

[0040] In the micro-arc oxidation process, the circulating cooling water is kept open, so that the electrolyte temperature is maintained between 20-40°C.

[0041] The polishing method in step S1 is: first, 400# sandpaper is used to polish the six surfaces of the magnesium alloy, then 400# sandpaper is used to polish the 12 edges of the magnesium alloy, and then 800#, 1000# and 1200# sandpaper are used to polish the six surfaces of the magnesium alloy, respectively.

[0042] As can be seen from the above, the method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte provided by the embodiment of the application solves the agglomeration of nanoparticles in the electrolyte fundamentally by pre-treating the valve metal surface through anodic electrodeposition and then preparing a composite coating through micro-arc oxidation, and the method has important significance for the application and popularization of nanoparticles in the micro-arc oxidation film.

[0043] In order to more clearly show the technical solutions provided by the application and the technical effects produced, the following describes the method provided by the embodiment of the application in detail with specific examples.

[0044] The application adopts the following technical solutions:

[0045] The method pre-constructs a film layer containing nanoparticles on the surface of the magnesium alloy through anodic electrodeposition, and then performs micro-arc oxidation treatment. The application creatively utilizes the anodic electrodeposition process to cause the magnesium alloy substrate as an anode to be slightly dissolved, expose a fresh active surface, and simultaneously utilize the electric field force to make the negatively charged nanoparticles adsorb and preliminarily fix on the substrate. This method fundamentally avoids the direct dispersion of the nanoparticles in the MAO electrolyte, thereby solving the agglomeration and settlement problem of the nanoparticles.

[0046] Compared with the existing "cathodic electrodeposition + micro-arc oxidation" process, the "anodic electrodeposition + micro-arc oxidation" of the application is an unconventional technical means, and the advantages and technical problems that can be solved include:

[0047] 1. Solve the agglomeration problem of nanoparticles: the nanoparticles are preliminarily fixed on the surface of the magnesium alloy through anodic electrodeposition, rather than being directly added to the MAO electrolyte, thereby avoiding the agglomeration and settlement of the nanoparticles in the MAO electrolyte from the source.

[0048] 2. Strengthen the binding force between nanoparticles and the substrate: the slight corrosion and activation of the anodic process on the surface of magnesium alloy exposes fresh metal active sites, enhancing the mechanical interlocking and binding force between nanoparticles and the substrate, which is conducive to the incorporation of nanoparticles in the subsequent MAO process.

[0049] 3. Simplify the process and reduce energy consumption: there is no need to use high-energy ultrasonic or stirring equipment to maintain nanoparticle dispersion during the MAO process, which significantly reduces energy consumption and the requirement for equipment heat dissipation.

[0050] 4. Improve economic efficiency and environmental protection: the electrolyte after electrodeposition can be stored and reused multiple times, reducing the consumption of nanoparticles and chemical reagents, and meeting the purpose of energy saving and emission reduction.

[0051] 5. Avoid the uncertainty brought by surface modification: there is no need for complex surface modification treatment of nanoparticles, avoiding the unpredictable influence of modified functional groups on the MAO process and the final film performance.

[0052] 6. Obtain more excellent film performance: the composite film prepared by this method has a more dense surface, uniform nanoparticle distribution, and good bonding with the substrate, significantly improving the comprehensive performance of the film, such as corrosion resistance.

[0053] Compared with traditional dispersion techniques, the beneficial effects of the present application are:

[0054] First, the titanium dioxide nanoparticles are fixed on the surface of the magnesium alloy by electrodeposition technology, indirectly blocking the dispersion, agglomeration and sedimentation of titanium dioxide nanoparticles in the micro-arc oxidation electrolyte. The dispersion, agglomeration and sedimentation of nanoparticles in the electrolyte are usually solved by traditional methods (ultrasonic stirring and surface modification), which has high energy consumption, high drug consumption, and the prepared electrolyte cannot be reused, and the operation is complex. In the complex environment of high temperature and high pressure of micro-arc oxidation, the use of ultrasonic stirring in the traditional method has a higher requirement for equipment heat dissipation, and the use of surface modification method may cause changes in the structure of the surface of the nanoparticles, which ultimately affects the performance of the film. The use of anode electrodeposition + micro-arc oxidation method can prepare a film with a more dense surface and better corrosion resistance, and this method has low energy consumption, simple operation, and the electrolyte after electrodeposition can be stored and reused. Specific embodiments

[0055] Referring to Figure 1 In some embodiments of the present application, the method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte comprises:

[0056] S1 cut the magnesium alloy into A 1cm cube is drilled with 1cm deep holes on the side of the cube. The sample is polished on a polishing machine to 400#, 800#, 1000# and 1200#. The surface stains are cleaned with deionized water and dried with anhydrous ethanol to obtain a standby sample (as shown in Figure 2 ). The standby sample is soaked in a 1-3wt% phosphoric acid solution for 30-50 seconds to obtain a pretreated magnesium alloy sample (as shown in Figure 3 ).

[0057] S2 The pretreated magnesium alloy sample is fixed on the clamp of the electrodeposition device as an anode, and a titanium plate or a graphite plate is used as a cathode and placed in an electrolyte containing nano-titanium dioxide. The electrodeposition process parameters are adjusted for electrodeposition treatment.

[0058] S3 After the electrodeposition is completed, the magnesium alloy sample is taken out of the electrolyte and dried in an oven to obtain a magnesium alloy film layer sample containing nano-particles.

[0059] S4 The magnesium alloy film layer sample containing nano-particles is fixed on the clamp of the micro-arc oxidation device as an anode, and a stainless steel plate is used as a cathode and placed in an electrolytic tank containing a silicate electrolyte. The micro-arc oxidation process parameters are adjusted for micro-arc oxidation. After the micro-arc oxidation is completed, the magnesium alloy film layer sample containing nano-particles is taken out of the electrolyte, rinsed with deionized water and anhydrous ethanol, and dried with a hair dryer to obtain a micro-arc oxidation magnesium alloy film layer containing nano-particles (as shown in Figure 4 ). The film layer is analyzed by XRD (as shown in Figure 5 ).

[0060] In the present application, the particle size of the nano-titanium dioxide is 30-45 nanometers, and the purity is 99%.

[0061] In step S1 of the present application, the standby sample is soaked in a 1-3wt% phosphoric acid solution, and further preferably 3wt%; the soaking time is 30-50 seconds, and further preferably 50 seconds.

[0062] It can be understood that soaking the magnesium alloy sample in a phosphoric acid solution can effectively remove the surface oxides and corrosion products, avoiding interference with the adhesion of the electrodeposited layer; by increasing the concentration of a certain amount of phosphoric acid and the soaking time, the magnesium alloy substrate can be slightly corroded to expose a clean magnesium alloy surface, enhancing the direct contact between the magnesium alloy and the nano-particles and enhancing the adhesion; to a certain extent, the magnesium alloy surface is activated, and the rapid regeneration of the surface passivation layer is temporarily inhibited, providing a higher active surface for the electrodeposition process.

[0063] In step S2 of the present application, a titanium plate or a graphite plate is used as a cathode, and further preferably a graphite plate.

[0064] In step S3 of the present application, the oven temperature is 30-70°C, preferably 70°C; the drying time is 10-20 minutes, preferably 20 minutes.

[0065] In some examples of the present application, the electrolyte containing nanometer titanium dioxide in step S2 is: ethanol solution 300ml (deionized water: deionized water = 4:1), sodium dodecyl sulfate 0.001-0.005 parts by mass, titanium dioxide 0.1-0.5 parts by mass, further preferably: ethanol solution 300ml, sodium dodecyl sulfate 0.005 parts by mass, titanium dioxide 0.5 parts by mass.

[0066] In some cases of the present application, the micro-arc oxidation electrolyte in step S4 is: sodium silicate 6-18 parts by mass, sodium hydroxide 3-9 parts by mass, glycerol 2-4 parts by mass, preferably sodium silicate 12-18 parts by mass, sodium hydroxide 6-9 parts by mass, glycerol 3-4 parts by mass, further preferably sodium silicate 18 parts by mass, sodium hydroxide 9 parts by mass, glycerol 4 parts by mass.

[0067] Specifically, the silicate electrolyte is the existing silicate system electrolyte, composed of sodium silicate, sodium hydroxide, glycerol and deionized water.

[0068] In some embodiments of the present application, the method for configuring the electrolyte containing nanometer titanium dioxide in step S2 is: first add sodium dodecyl sulfate to the ethanol solution, stir until completely dissolved, slowly add nanometer titanium dioxide to the ethanol solution, and continuously stir to make it fully dispersed, to obtain the electrodeposition electrolyte containing nanometer titanium dioxide.

[0069] It can be understood that sodium dodecyl sulfate can be used as a dispersant to make nanometer titanium dioxide uniformly dispersed in the ethanol solution during stirring, and uniformly distributed on the surface of the magnesium alloy during electrodeposition.

[0070] In some embodiments of the present application, the electrodeposition process parameters in step S2 are: in constant voltage mode, the voltage is 6-10V, and the deposition time is 5-10 minutes, preferably in constant voltage mode, the voltage is 8-10V, and the deposition time is 8-10 minutes, further preferably in constant voltage mode, the voltage is 10V, and the deposition time is 10 minutes.

[0071] In some embodiments of the present application, the micro-arc oxidation process parameters in step S4 are as follows: constant current mode, current 1-3 A, pulse frequency 500-1000 Hz, duty cycle 20-40%, oxidation time 10-30 minutes, preferably constant current mode, current 2-3 A, pulse frequency 800-1000 Hz, duty cycle 30-40%, oxidation time 20-30 minutes, further preferably constant current mode, current 3 A, pulse frequency 1000 Hz, duty cycle 40%, oxidation time 30 minutes.

[0072] Specifically, during the micro-arc oxidation process, the temperature of the electrolyte is maintained at 20-40°C by circulating cooling water.

[0073] It can be understood that when the temperature is low, the discharge intensity may be inhibited, resulting in a thin or insufficiently dense film layer, and when the temperature is too high, the discharge is intensified, resulting in a rough film layer with increased porosity. And 20-40°C is a controllable range verified, which can balance the reaction efficiency and stability.

[0074] In some embodiments of the present application, the polishing method in step S1 is as follows: first polish the six surfaces of the magnesium alloy with 400 grit sandpaper, then polish the 12 edges of the magnesium alloy with 400 grit sandpaper, and then polish the six surfaces of the magnesium alloy with 800 grit, 1000 grit and 1200 grit sandpaper, respectively.

[0075] It can be understood that the edge parts will have more intense discharge due to the concentration of electric field during the micro-arc oxidation process, which is prone to form uneven coating or burrs. Polishing can eliminate these defects and improve the consistency of the surface. Polishing with different grits can make the magnesium alloy surface more uniform, which is beneficial to the uniform growth of the micro-arc oxidation ceramic film layer.

[0076] Embodiment 1

[0077] S1 Cut the magnesium alloy into a square of 1 cm x 1 cm, drill a 1 cm deep hole on the side of the square, polish the sample on a grinding and polishing machine with 400#, 800#, 1000# and 1200#, wash the surface stains with deionized water, dry with anhydrous ethanol, and obtain a standby sample. Soak the standby sample in a 1 wt% phosphoric acid solution for 30 seconds to obtain a pretreated magnesium alloy sample. S2 Take 300 ml of ethanol solution, add 0.001 parts by mass of sodium dodecyl sulfate to the ethanol solution, stir to dissolve, then add 0.1 parts by mass of nano-titanium dioxide and continuously stir to fully disperse to obtain an electrodeposition electrolyte containing nano-titanium dioxide.

[0078]

[0079] ​S3. The prepared electrodeposition electrolyte was added to the electrodeposition equipment. The pretreated magnesium alloy sample was used as the anode and fixed on the fixture of the electrodeposition equipment, ensuring that the pretreated magnesium alloy sample was completely immersed in the electrolyte and that the current was evenly distributed on the sample surface. The graphite plate was used as the cathode. The electrodeposition parameters were adjusted to keep the electrodeposition voltage constant at 6V and the deposition time at 5 minutes. After electrodeposition, the sample was placed in a 30°C oven to dry for 10 minutes.

[0080] S4. Prepare a 1-liter solution by mixing 6 parts by mass of sodium silicate, 3 parts by mass of sodium hydroxide, 2 parts by mass of glycerol, and deionized water. Stir until homogeneous to obtain a micro-arc oxidation electrolyte. Add the prepared electrolyte to the electrolytic cell. Use the electrodeposited magnesium alloy sample as the anode and fix it on the fixture of the micro-arc oxidation equipment. Use a stainless steel plate as the cathode to ensure full contact between the sample and the electrolyte. Adjust the electrical parameters to keep the current constant at 1A, the frequency at 500Hz, the duty cycle at 20%, and the oxidation time at 10 minutes. Maintain the electrolyte temperature at 20-40°C during the micro-arc oxidation process. After oxidation, rinse continuously with deionized water for 5 minutes to remove residual electrolyte and impurities from the surface. Dry with a hair dryer to obtain a magnesium alloy micro-arc oxidation film with nano-titanium dioxide.

[0081] Example 2

[0082] S1 cuts magnesium alloy into A cube of cm diameter was prepared by drilling a 1 cm deep hole in its side. The sample was then polished to 400#, 800#, 1000#, and 1200# grit using a polishing machine. Surface stains were cleaned with deionized water, and the sample was dried with anhydrous ethanol to obtain a ready-to-use sample. The ready-to-use sample was then immersed in a 2 wt% phosphoric acid solution for 40 seconds to obtain a pretreated magnesium alloy sample.

[0083] S2 Take 300 ml of ethanol solution, add 0.003 parts by mass of sodium dodecyl sulfate to the ethanol solution, stir to dissolve, then add 0.3 parts by mass of nano titanium dioxide and stir continuously to fully disperse it to obtain an electrodeposition electrolyte containing nano titanium dioxide.

[0084] S3. The prepared electrodeposition electrolyte was added to the electrodeposition equipment. The pretreated magnesium alloy sample was used as the anode and fixed on the fixture of the electrodeposition equipment, ensuring that the pretreated magnesium alloy sample was completely immersed in the electrolyte and that the current was evenly distributed on the sample surface. The graphite plate was used as the cathode. The electrodeposition parameters were adjusted to keep the electrodeposition voltage constant at 8V and the deposition time at 8 minutes. After electrodeposition, the sample was placed in a 50°C oven to dry for 15 minutes.

[0085] S4. Prepare a 1-liter solution by mixing 12 parts by mass of sodium silicate, 6 parts by mass of sodium hydroxide, 3 parts by mass of glycerol, and deionized water. Stir until homogeneous to obtain a micro-arc oxidation electrolyte. Add the prepared electrolyte to the electrolytic cell. Use the electrodeposited magnesium alloy sample as the anode and fix it on the fixture of the micro-arc oxidation equipment. Use a stainless steel plate as the cathode to ensure full contact between the sample and the electrolyte. Adjust the electrical parameters to keep the current constant at 2A, the frequency at 800Hz, the duty cycle at 30%, and the oxidation time at 20 minutes. Maintain the electrolyte temperature at 20-40°C during the micro-arc oxidation process. After oxidation, rinse continuously with deionized water for 5 minutes to remove residual electrolyte and impurities from the surface. Dry with a hair dryer to obtain a magnesium alloy micro-arc oxidation film with nano-titanium dioxide.

[0086] Example 3

[0087] S1 cuts magnesium alloy into A cube of cm was prepared, with a 1cm hole drilled in its side. The sample was then polished to 400#, 800#, 1000#, and 1200# grit using a polishing machine. Surface stains were cleaned with deionized water, and the sample was dried with anhydrous ethanol to obtain a ready-to-use sample. The ready-to-use sample was then immersed in a 3wt% phosphoric acid solution for 50 seconds to obtain a pretreated magnesium alloy sample.

[0088] S2 Take 300 ml of ethanol solution, add 0.005 parts by mass of sodium dodecyl sulfate to the ethanol solution, stir to dissolve, then add 0.5 parts by mass of nano titanium dioxide and stir continuously to fully disperse it to obtain an electrodeposition electrolyte containing nano titanium dioxide.

[0089] S3. The prepared electrodeposition electrolyte was added to the electrodeposition equipment. The pretreated magnesium alloy sample was used as the anode and fixed on the fixture of the electrodeposition equipment, ensuring that the pretreated magnesium alloy sample was completely immersed in the electrolyte and that the current was evenly distributed on the sample surface. The graphite plate was used as the cathode. The electrodeposition parameters were adjusted to keep the electrodeposition voltage constant at 10V and the deposition time at 10 minutes. After electrodeposition, the sample was placed in a 70°C oven to dry for 20 minutes.

[0090] S4 Take sodium silicate 18 parts by mass, sodium hydroxide 9 parts by mass, glycerol 4 parts by mass and deionized water to configure into 1 liter solution, stirring to make it mixed evenly, get micro-arc oxidation electrolyte, add the prepared electrolyte into the electrolytic tank, the magnesium alloy sample after electrodeposition as anode, fixed on the fixture of micro-arc oxidation equipment, stainless steel plate as cathode, ensure that the sample and electrolyte are in full contact, adjust the electrical parameters, so that the current is constant at 3A, frequency is 1000Hz, duty cycle is 40%, oxidation time is 30 minutes, keep the electrolyte temperature at 20-40°C during micro-arc oxidation process, after oxidation, rinse with deionized water for 5 minutes to remove the residual electrolyte and impurities on the surface, dry with a hair dryer, get the magnesium alloy micro-arc oxidation film layer with nano titanium dioxide.

[0091] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. The information disclosed in the background section of this paper is only intended to deepen the understanding of the overall background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for solving the agglomeration of nanoparticles in a micro-arc oxidation electrolyte, characterized in that, The method comprises the steps of: S1 cut the magnesium alloy into cm cube, drill 1 cm deep holes on the side of the cube, polish the sample on the grinding and polishing machine to 400#, 800#, 1000# and 1200#, clean the surface stains with deionized water, dry with anhydrous ethanol to obtain a standby sample; immersing the standby sample in a 1-3 wt% phosphoric acid solution for 30-50 seconds to obtain a pretreated magnesium alloy sample; S2: fixing the pretreated magnesium alloy sample as an anode on a clamp of an electrodeposition device, using a titanium plate or a graphite plate as a cathode, and placing the sample into an electrolyte containing nano-titanium dioxide; adjusting the electrodeposition process parameters to perform electrodeposition treatment; S3: after the electrodeposition is completed, taking the magnesium alloy sample out of the electrolyte and placing it into an oven for drying to obtain a magnesium alloy film layer sample containing nano-particles; S4: fixing the magnesium alloy film layer sample containing nano-particles as an anode on a clamp of a micro-arc oxidation device, using a stainless steel plate as a cathode, placing the sample into an electrolytic tank containing a silicate electrolyte, and adjusting the micro-arc oxidation process parameters to perform micro-arc oxidation; after the micro-arc oxidation is completed, taking the magnesium alloy film layer sample containing nano-particles out of the electrolyte, rinsing it with deionized water and anhydrous ethanol, and drying it with a hair dryer to obtain a micro-arc oxidation magnesium alloy film layer containing nano-particles.

2. The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte according to claim 1, characterized in that, The electrolyte containing nano-titanium dioxide in step S2 is an ethanol solution with a volume ratio of anhydrous ethanol to deionized water being 4:1, and the solution contains 0.001-0.005 parts by mass of sodium dodecyl sulfate and 0.1-0.5 parts by mass of titanium dioxide.

3. The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte according to claim 2, characterized in that, The configuration method of the electrolyte containing nano-titanium dioxide in step S2 is as follows: first, sodium dodecyl sulfate is added to the ethanol solution and stirred until it is completely dissolved, then nano-titanium dioxide is slowly added to the ethanol solution while continuously stirring to make it fully dispersed, and finally the electrodeposition electrolyte containing nano-titanium dioxide is obtained.

4. The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte according to claim 3, characterized in that, In step S2, the electrodeposition process parameters are as follows: in the constant voltage mode, the voltage is 6-10 V, and the deposition time is 5-10 minutes.

5. The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte according to claim 1, characterized in that, The silicate electrolyte in step S4 contains 6-18 parts by mass of sodium silicate, 3-9 parts by mass of sodium hydroxide, and 2-4 parts by mass of glycerol.

6. The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte according to claim 5, characterized in that, The micro-arc oxidation electrical parameters in step S4 are as follows: in the constant current mode, the current is 1-3 A, the pulse frequency is 500-1000 Hz, the duty cycle is 20-40%, and the oxidation time is 10-30 minutes.

7. The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte according to claim 6, characterized in that, During the micro-arc oxidation process, the circulating cooling water is kept open to maintain the electrolyte temperature at 20-40°C.

8. The method for solving the agglomeration of nanoparticles in the micro-arc oxidation electrolyte according to claim 1, characterized in that, The polishing method in step S1 is as follows: first, polish the six surfaces of the magnesium alloy with 400# sandpaper, then polish the 12 edges of the magnesium alloy with 400# sandpaper, and finally polish the six surfaces of the magnesium alloy with 800#, 1000#, and 1200# sandpaper, respectively.

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