Nanoparticle modified electrolyte and application thereof, thermal control coating and preparation method thereof, and thermal control part

Abstract

The invention relates to the field of surface engineering, and discloses a nanoparticle modified electrolyte and application thereof, a thermal control coating and a preparation method thereof, and a thermal control component. The electrolyte provided by the invention comprises silicate, phosphate, hydroxide and zirconium dioxide nanoparticles, the concentration of the zirconium dioxide nanoparticles is 5-50g / L, and the particle size is 20-50nm. According to the zirconium dioxide nanoparticle modified micro-arc oxidation electrolyte, through zirconium dioxide nanoparticle filling, densification and optical interference effects, the thermal control performance that alpha S is equal to 0.24-0.28 and epsilon H is larger than or equal to 0.85 is achieved, and meanwhile the neutral salt mist resistance is improved to 96 h or above; accurate regulation and control of thermal control parameters and long-acting blocking of corrosive media are achieved at the same time through a single ceramic layer, and the full-life-cycle high-reliability service requirement of thermal control components is met.

Description

Technical Field

[0001] This application relates to the field of surface engineering, and more particularly to a nanoparticle-modified electrolyte and its application, a thermal control coating and its preparation method, and a thermal control component. Background Technology

[0002] Spacecraft components must withstand the dual challenges of special storage environments and on-orbit thermal cycling during their service life. In special storage environments such as coastal areas, the concentration of chloride ions in the air can reach as high as 5-10 mg / m³. 3 When the relative humidity exceeds 85%, visible pitting corrosion will appear on magnesium alloys after 3-6 months of storage, affecting the performance and safety of the components. After entering orbit, the components undergo cyclic temperature shocks of ±120℃ per rail. If the solar absorption ratio of the thermal control coating is higher than α... S A value greater than 0.30 will cause the temperature drift of structural components to exceed 30°C, directly affecting the accuracy of optical loads and the lifespan of electronic devices.

[0003] While traditional micro-arc oxidation films can provide a certain hemispherical emissivity, their porosity is generally greater than 8% and their microcrack density is high, forming rapid chloride ion penetration channels, resulting in a neutral salt spray life of less than 24 hours. Although existing composite coatings have improved salt spray performance to 48 hours, the organic sealing layer becomes brittle and cracks after 2000 thermal cycles at -150℃ to +150℃, and new corrosion galvanic cells are formed at the interface, leading to protective failure. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a nanoparticle-modified electrolyte, so that the thermally controlled coating generated by micro-arc oxidation of the electrolyte achieves α S ≤0.28, ε H It has a thermal control performance of ≥0.85, and significantly improves its resistance to neutral salt spray, extending it to over 96 hours.

[0005] Another objective of this application is to provide the application of the above-mentioned electrolyte in the preparation of thermal control coatings; Another objective of this application is to provide a thermal control coating based on the above-mentioned electrolyte and a method for preparing the same. Another objective of this application is to provide a thermal control component based on the above-mentioned thermal control coating, so that the thermal control component possesses the excellent performance brought about by the above-mentioned thermal control coating.

[0006] In order to solve the above-mentioned technical problems / achieve the above-mentioned objectives, or at least partially solve the above-mentioned technical problems / achieve the above-mentioned objectives, as a first aspect of this application, a nanoparticle modified electrolyte is provided, comprising silicate, phosphate, hydroxide and zirconium dioxide nanoparticles; wherein the concentration of the zirconium dioxide nanoparticles is 5~50 g / L and the particle size is 20~50 nm.

[0007] Optionally, the electrolyte comprises 30-60 g / L of silicate, 3-10 g / L of phosphate, 2-10 g / L of hydroxide, and 5-50 g / L of zirconium dioxide nanoparticles.

[0008] Further optionally, the silicate includes sodium silicate, the phosphate includes sodium dihydrogen phosphate, and the hydroxide includes sodium hydroxide.

[0009] Optionally, the electrolyte further includes a dispersant selected from any one of sodium citrate, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate.

[0010] As a second aspect of this application, the application of the electrolyte in the preparation of micro-arc oxidation thermal control coatings is provided.

[0011] As a third aspect of this application, a thermal control coating is provided, which is formed by micro-arc oxidation of the electrolyte described in this application.

[0012] As a fourth aspect of this application, a method for preparing the thermal control coating described in this application is provided, comprising: Using a magnesium alloy as the anode and a stainless steel plate as the cathode, the material is placed in the electrolyte described in this application for micro-arc oxidation to obtain the thermal control coating on the surface of the magnesium alloy.

[0013] Optionally, the process parameters for the micro-arc oxidation include: Frequency 500~1000Hz, duty cycle 10~20%.

[0014] Optionally, the micro-arc oxidation is carried out using a vacuum gas stirring system with the assistance of inert gas or compressed air.

[0015] As a fifth aspect of this application, a thermal control component is provided, including a magnesium alloy substrate and a thermal control coating disposed on the surface of the magnesium alloy substrate, the thermal control coating including the thermal control coating described in this application.

[0016] This application provides a micro-arc oxidation electrolyte modified with zirconium dioxide nanoparticles, which achieves α through the filling, densification, and optical interference effects of zirconium dioxide nanoparticles. S =0.24~0.28、ε H With a thermal control performance of ≥0.85, the resistance to neutral salt spray is improved to over 96 hours. A single ceramic layer enables precise control of thermal control parameters and long-term isolation from corrosive media, meeting the high reliability service requirements of thermal control components throughout their entire life cycle. Attached Figure Description

[0017] Figure 1The image shown is a scanning electron microscope (SEM) image of the micro-arc oxidation coating in Example 1 (left) and an EDSMapping image of the elemental distribution of Mg, Si, Zr, and O (right). Figure 2 The image shown is a scanning electron microscope image (300 μm, 50 μm, 10 μm) with zirconium dioxide nanoparticles added at concentrations of 25 g / L, 30 g / L, 40 g / L, and 50 g / L. Figure 3 The XRD phase analysis diagrams are shown for zirconium dioxide nanoparticles with addition amounts of 25 g / L, 30 g / L, and 40 g / L. Detailed Implementation

[0018] This application discloses a nanoparticle-modified electrolyte and its application, a thermal control coating and its preparation method, and a thermal control component. Those skilled in the art can refer to the content of this application and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products, processes, and applications described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the preparation methods described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0020] Nanoparticle modification technology can capture and encapsulate molten oxides in micro-arc oxidation, allowing them to migrate with the melt flow to the bottom of the discharge micropores, thus filling the micropores. Simultaneously, the nanoparticles construct a three-dimensional physical barrier network within the ceramic layer, forcing corrosive media to bypass the long path formed by the nanoparticles to reach the substrate, significantly slowing down the corrosion process. However, achieving optimal results depends on the precise selection of nanoparticles and their compatibility with other components of the electrolyte. Currently, there is no research method for preparing magnesium alloy micro-arc oxidation films that simultaneously possess both low solar absorptivity and high corrosion resistance, and stable preparation methods for α-type... S A systematic solution with a viscosity of ≤0.28 and a corrosion protection life of ≥96h.

[0021] In the first aspect of this application, addressing the deficiency in existing technologies for preparing magnesium alloy micro-arc oxidation films that simultaneously possess low solar absorptivity and high corrosion resistance, a micro-arc oxidation electrolyte modified with zirconium dioxide nanoparticles is provided. This electrolyte comprises silicates, phosphates, hydroxides, and zirconium dioxide nanoparticles. The concentration of the zirconium dioxide nanoparticles is 5-50 g / L, and the particle size is 20-50 nm. The concentration of the zirconium dioxide nanoparticles can be selected from 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, or any value between these two ranges. The particle size of the zirconium dioxide nanoparticles can be selected from 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or any value between these two ranges. Zirconia nanoparticles, as the core modifying component of the electrolyte in this application, have a particle size of 20-50 nm, which allows them to enter the bottom of the discharge micropores with a filling rate of >85%, forming a physical barrier.

[0022] Traditional micro-arc oxidation films have micropores with diameters of 3-5 μm and steep pore walls. Multiple reflections and absorptions of sunlight after incidence lead to α-ray dilution. S The pore size is relatively high. This application utilizes zirconium dioxide nanoparticles to reduce the micropore diameter to 1.0~1.5 μm, resulting in smooth pore bottoms and a pyramid-like microstructure on the surface, with a roughness Ra≤1.0 μm and α... S The solar absorptivity was stably controlled within the range of 0.24–0.28, with batch-to-batch fluctuations of ±0.015, which is superior to the ±0.030 fluctuation of the solar absorptivity of traditional micro-arc oxidation films. ZrO2 exhibits high emissivity (ε) in the 8–14 μm infrared band. H (≈0.92), the diffuse distribution makes the overall ε of the film layer ≈0.92), H By increasing the efficiency to 0.85~0.90, the heat dissipation efficiency of thermal control components, such as heat sink base plates, can be improved by 15%, while the heat dissipation area can be reduced by 10%, thus reducing the system weight.

[0023] In some embodiments of this application, the electrolyte comprises 30-60 g / L of silicate, 3-10 g / L of phosphate, 2-10 g / L of hydroxide, and 5-50 g / L of zirconium dioxide nanoparticles. The silicate provides the basic film-forming anion SiO3. 2- During discharge, an amorphous SiO2 matrix is ​​formed, whose high infrared radiation characteristics ensure ε H ≥0.85; phosphate provides PO4 3- This promotes the formation of the Mg3(PO4)2 phase and improves the film density; the hydroxide maintains a pH ≥ 13, ensuring stable complexation of the silicate without hydrolysis and precipitation. In some other embodiments of this application, the silicate includes sodium silicate, and the silicate concentration can be selected from 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L or any value between the two; the phosphate includes sodium dihydrogen phosphate, and the phosphate concentration can be selected from 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L or any value between the two; the hydroxide includes sodium hydroxide, and the hydroxide concentration can be selected from 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L or any value between the two.

[0024] In some embodiments of this application, the electrolyte further includes a dispersant selected from sodium citrate, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate. The dispersant, through electrostatic steric hindrance, complexes with the hydroxyl groups on the surface of ZrO2 particles to form an electrical double layer, increasing the absolute value of the Zeta ζ potential to above 40 mV. This prevents the aggregation of nanoparticles in a strongly alkaline environment, ensuring a 48-hour sedimentation rate of <5% for the nanoparticles. This guarantees that the nanoparticles uniformly enter the molten oxide within the micro-arc discharge micro-region, thus ensuring the long-term stability of the electrolyte.

[0025] In some embodiments of this application, the electrolyte is mixed by a combination of ultrasonic dispersion and mechanical stirring, with ultrasonic dispersion lasting 30-60 minutes (power density 0.8-1.2 W / cm³). 3 The nanoparticles are initially deagglomerated by stirring at a frequency of 40kHz, and then mechanically stirred for 12-24 hours to maintain their suspension. The two work together to ensure uniform dispersion and form a stable suspension electrolyte with a sedimentation rate of <5% after 48 hours.

[0026] In a second aspect of this application, the application of the described electrolyte in the preparation of micro-arc oxidation thermal control coatings is provided. Coatings prepared using the zirconia nanoparticle-modified electrolyte of this application have at least the following advantages: (1) Precise and stable thermal control performance: After modification by zirconium dioxide nanoparticles, a submicron-level flat structure is formed on the surface of the film, Rayleigh scattering is significantly reduced, the solar absorptivity is stably controlled in the range of 0.24~0.28 with a fluctuation range of ±0.015, the hemispherical emissivity is increased to 0.85~0.90 due to the high infrared radiation characteristics of ZrO2, and the heat dissipation efficiency is increased by more than 15%, which meets the precise temperature control requirements of ±10℃ for thermal control components.

[0027] (2) The corrosion protection life is greatly extended: the filling of zirconium dioxide nanoparticles increases the tortuosity of the penetration path of corrosive media by 3 times. After 96 hours of neutral salt spray test (GB / T 10125-2021), the corrosion area is <2%, which reaches the current level of composite coatings. Moreover, the single ceramic layer structure has no risk of interface failure. The corrosion protection life can cover the 15-year design life of thermal control components. (3) Synergistic enhancement of nano-effect: Zirconia nanoparticles form a dispersed strengthening phase in the ceramic layer, which hinders crack propagation. The film density is >97% and the microhardness is ≥400HV, which is more than 30% higher than conventional micro-arc oxidation, meeting the load-bearing and scratch resistance requirements of the mounting surface. (4) Outstanding process stability: The dispersant system ensures that the electrolyte does not settle within 48 hours, the utilization rate of nanoparticles is >90%, the process repeatability is over 95%, and the batch-to-batch absorption ratio deviation is <0.02, making it suitable for mass production of thermal control components.

[0028] In a third aspect of this application, a thermal control coating is provided, formed by micro-arc oxidation using the electrolyte described in this application. The thermal control coating uses a magnesium alloy substrate as a carrier, and the modified thermal control coating is formed on its surface by micro-arc oxidation using the electrolyte described in this application. The coating is uniformly bright white, with a final film thickness of 40~80μm (batch deviation ≤ ±5μm), surface roughness Ra ≤ 1.0μm (smooth micro-ripples, no sharp protrusions), porosity ≤ 3%, and chloride ion permeability coefficient reduced by more than 60% compared to the unmodified film, achieving a long-lasting anti-corrosion effect.

[0029] In a fourth aspect of this application, a method for preparing the thermal control coating described in this application is provided, comprising: Using a magnesium alloy as the anode and a stainless steel plate as the cathode, the material is placed in the electrolyte described in this application for micro-arc oxidation to obtain the thermal control coating on the surface of the magnesium alloy.

[0030] In some embodiments of this application, the process parameters of the micro-arc oxidation include: frequency 500~1000Hz and duty cycle 10~20%. High-frequency, low-duty-cycle pulses can refine the discharge channel to a pore size ≤1.5μm, allowing ZrO2 nanoparticles to be fully dispersed and distributed during the micro-region melting-solidification process and fill the bottom of the micropores, forming a dense barrier layer without penetrating pores.

[0031] In other embodiments of this application, the process parameters for micro-arc oxidation further include: Voltage 450~600V, current density 5~10A / dm 2 Processing time: 30-45 min; electrolyte temperature: 15-30℃; voltage: 450-600V using a linear boost + constant voltage mode; voltage is increased to the working voltage within 0-5 min to form a barrier layer; the remaining time is spent maintaining the working voltage to promote ceramic layer growth; current density: 5-10 A / dm³. 2 The corresponding single-pulse energy is 0.6~1.5J. If the energy is too low, the nanoparticles will not be deposited sufficiently, and if it is too high, the molten material will splash. The frequency of 500~1000Hz ensures that the single discharge time is 1~2ms, and the duty cycle of 10~20% ensures that heat is dissipated within the pulse interval and avoids heat accumulation.

[0032] In some embodiments of this application, the micro-arc oxidation is assisted by a vacuum gas stirring system that introduces inert gas or compressed air. The system may consist of a vacuum pump, a gas distributor, and an electrolytic cell. The vacuum degree is maintained at -0.08 to -0.09 MPa, and nitrogen or compressed air is introduced through the gas distributor at the bottom of the cell. The gas flow rate is 0.5 to 2 L / min, and the upward flow velocity is 0.1 to 0.3 m / s. The vacuum gas stirring produces the following effects: (1) the rising bubbles drive the electrolyte circulation, so that the suspension concentration deviation of zirconium dioxide nanoparticles is <3%, avoiding gravity sedimentation; (2) the bubbles break on the surface of the workpiece, generating micro-vibrations, promoting the detachment of discharge products, and preventing local overheating.

[0033] In some embodiments of this application, the magnesium alloy substrate further includes a pretreatment process of decontamination, pickling, and rinsing before micro-arc oxidation. The decontamination includes, but is not limited to, degreasing with acetone (removing the oil film), and ultrasonication may be used if necessary. The pickling includes, but is not limited to, treatment with dilute hydrochloric acid, such as 10% dilute hydrochloric acid for 1-2 minutes. Appropriate cleaning with dilute hydrochloric acid can dissolve the oxide scale without causing intergranular corrosion. Pickling can increase the surface activation energy, which is beneficial for the uniform growth of the oxide film in the early stages of micro-arc oxidation. Finally, rinsing with deionized water prevents impurity ions from being introduced into the electrolyte and affecting discharge stability.

[0034] In some embodiments of this application, after micro-arc oxidation, a post-processing step of cleaning and drying the component is included. In other embodiments of this application, the post-processing includes: The component is removed and rinsed with deionized water, then dried at 110~130℃ for 2~3 hours to form a bright white nanoparticle modified micro-arc oxidation thermal control anti-corrosion coating with a thickness of 40~80μm, surface roughness Ra≤1.0μm, porosity≤3%, and chloride ion permeation rate reduced by more than 60% compared with conventional membranes.

[0035] In the post-treatment stage, deionized water rinsing is performed using a combination of spraying (pressure 0.2 MPa, time 3 min) and soaking (5 min) to remove residual electrolyte from the surface and pores. Drying is carried out in a clean oven at a heating rate of 5℃ / min, holding at 110~130℃ for 2~3 hours to fully remove residual moisture and hydroxyl groups from the ceramic layer, ensuring a volume shrinkage rate of <2% and preventing microcracks. After drying, the coating is allowed to cool naturally to room temperature, resulting in a uniform bright white coating. In a fifth aspect of this application, a thermal control component is provided, comprising a magnesium alloy substrate and a thermal control coating disposed on the surface of the magnesium alloy substrate, the thermal control coating comprising the thermal control coating described in this application.

[0036] In some embodiments of this application, the magnesium alloy matrix includes, but is not limited to, MB15 magnesium alloy.

[0037] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials are kept consistent to ensure comparability. Unless otherwise specified, all experimental materials and reagents used in the examples are commercially available.

[0038] The following provides further details regarding the nanoparticle electrolyte and its application, the thermal control coating and its preparation method, and the thermal control components provided in this application.

[0039] Example 1: 1. Magnesium alloy workpiece: MB15 magnesium alloy sheet (40mm×40mm×2mm) is selected. 2. Preparation of Nano-Modified Electrolyte: Add 15L of deionized water (conductivity ≤1μS / cm) to a 20L sealed electrolytic cell, and start the vacuum gas stirring system (nitrogen flow rate 1.2L / min). Add 50g / L (750g) sodium silicate, 6g / L (90g) sodium dihydrogen phosphate, 4g / L (60g) sodium hydroxide, and 3g / L (45g) sodium citrate sequentially. Stir for 30min until completely dissolved. Then, slowly add 25g / L (375g) of 30nm zirconium dioxide nanoparticles. Continue stirring while simultaneously starting ultrasonic dispersion at a power density of 1.0W / cm³. 3 The electrolyte was sonicated at a frequency of 40 kHz for 45 minutes. Then, it was continuously mechanically stirred for 18 hours to form a stable suspension. After the electrolyte settled, the measured conductivity was 20 mS / cm, pH = 13.3, the sedimentation rate was 2.1% after 48 hours, and the z-potential of ZrO2 particles was -42 mV, confirming that the dispersion stability met the standards. 3. Micro-arc oxidation process: The workpiece is clamped on an aluminum alloy fixture, ensuring a conductive area and preventing damage during assembly and disassembly. The workpiece is immersed 12cm below the electrolyte surface. The anode is connected to the workpiece, and the cathode is a stainless steel plate with a 16cm electrode spacing. Process parameters are set as follows: voltage 520V (stepped mode: 0~1min to 520V, maintaining the operating voltage for the remaining time), current density 6A / dm³. 2 The processing time was 35 minutes. The electrolyte temperature was controlled at 25±2℃ through jacket cooling and gas stirring, the frequency was 800Hz, and the duty cycle was 15%. During the discharge process, the bubbles from the vacuum gas stirring burst uniformly on the workpiece surface, and the micro-arcs appeared fine and bluish-white, without localized ablation. After the treatment, the workpiece surface was uniformly bright white, without yellow spots or flow marks, and the film layer was initially formed and complete. 4. Performance Testing: Coating thickness 59μm, surface roughness Ra=0.8μm, solar absorptivity α S =0.24, hemispherical emissivity ε H =0.90, microhardness up to 450HV, corrosion area of ​​1.5% after 96h of neutral salt spray test, and the coating is intact after 2000 thermal cycles (-150℃~+150℃). Figure 1 The image shows a scanning electron microscope (SEM) image (left) and an EDS mapping image (right) of the micro-arc oxidation coating with the addition of zirconium dioxide nanoparticles in Example 1.

[0040] Example 2: 1. Magnesium alloy workpiece: Mg-Li alloy plate (36mm×36mm×3mm) is selected. 2. Preparation of Nano-Modified Electrolyte: Add 15L of deionized water to a 20L sealed electrolytic cell and start the vacuum gas stirring system (compressed air flow rate 1.5L / min). Add 60g / L (900g) sodium silicate, 7g / L (105g) sodium dihydrogen phosphate, 4g / L (60g) sodium hydroxide, and 0.5g / L (7.5g) sodium dodecylbenzenesulfonate sequentially. Stir for 40min until completely dissolved, then add 30g / L (450g) of 50nm zirconium dioxide nanoparticles. The ultrasonic dispersion power density is 1.2W / cm³. 3 The frequency was 40 kHz, and the time was 60 min. Mechanical stirring was then continued for 24 h to form a stable suspension. After the electrolyte settled, the measured conductivity was 24 mS / cm, pH = 13.4, the sedimentation rate was 1.8% after 48 h, and the ZrO2 particle zeta potential was -48 mV, confirming that the dispersion stability met the standards. 3. Micro-arc oxidation process: The workpiece is clamped on an aluminum alloy fixture, the surface of which is treated with hard anodizing for insulation. Process parameters are set as follows: voltage 600V (stepped mode: voltage increases to 600V from 0 to 1 minute, and is maintained for the remaining time), current density 8A / dm³.2 The treatment time was 40 minutes, the electrolyte temperature was 32±2℃ (with gas stirring and cooling system working together), the frequency was 1000Hz, and the duty cycle was 12%. The high frequency and low duty cycle combined with gas stirring resulted in dense, dotted discharge micro-arcs, bluish-white in color, without macroscopic arc spots, and uniform film growth. After treatment, the workpiece surface was uniformly bright white with good color consistency. 4. Performance Testing: Coating thickness 62μm, surface roughness Ra=0.9μm, solar absorptivity α S =0.25, hemispherical emissivity ε H =0.89, microhardness up to 460HV, corrosion area <1% after 96h of neutral salt spray test, coating intact after 2000 thermal cycles (-150℃~+150℃).

[0041] Example 3: The micro-arc oxidation coating was prepared according to the process in Example 1, except that the concentration of zirconium dioxide nanoparticles was adjusted and relevant tests were performed. Figure 2 The image shows scanning electron microscope (SEM) images (300 μm, 50 μm, and 10 μm) of zirconium dioxide nanoparticles at concentrations of 25 g / L, 30 g / L, 40 g / L, and 50 g / L.

[0042] Figure 3 The XRD phase analysis diagrams of 25 g / L, 30 g / L, and 40 g / L zirconium dioxide nanoparticles are shown. The characteristic peaks of zirconium dioxide are located at 2θ of 30.6° and 50.7°. The intensity of these two peaks increases significantly with the increase of zirconium dioxide nanoparticle concentration, indicating that the zirconium dioxide nanoparticles are successfully attached to the surface of the micro-arc oxide film layer, and the intensity increases with the increase of concentration.

[0043] Comparative Example 1 (No nanoparticles added): 1. Magnesium alloy workpiece: MB15 magnesium alloy sheet (40mm×40mm×2mm) is selected. 2. Preparation of nano-modified electrolyte: Add 15L of deionized water (conductivity ≤1μS / cm) to a 20L sealed electrolytic cell, and start the vacuum gas stirring system (nitrogen flow rate 1.2L / min). Add sodium silicate 50g / L (750g), sodium dihydrogen phosphate 6g / L (90g), sodium hydroxide 4g / L (60g), and sodium citrate 3g / L (45g) in sequence, and stir for 30min until completely dissolved (except for the absence of zirconium dioxide nanoparticles, the electrolyte formulation is the same as in Example 1); 3. Micro-arc oxidation process: The workpiece is clamped on an aluminum alloy fixture, ensuring a conductive area and preventing damage during assembly and disassembly. The workpiece is immersed 12cm below the electrolyte surface. The anode is connected to the workpiece, and the cathode is a stainless steel plate with a 16cm electrode spacing. Process parameters are set as follows: voltage 520V (stepped mode: 0~1min to 520V, maintaining the operating voltage for the remaining time), current density 6A / dm³. 2 The processing time was 35 minutes. The electrolyte temperature was controlled at 25±2℃ through jacket cooling and gas stirring, the frequency was 800Hz, and the duty cycle was 15%. During the discharge process, the bubbles from the vacuum gas stirring burst uniformly on the workpiece surface, and the micro-arc appeared fine and yellowish-white, without localized ablation. After the treatment, the workpiece surface was uniformly grayish-white, without yellow spots or flow marks, and the film layer was initially formed and complete (the micro-arc oxidation process was the same as in Example 1). 4. Performance Testing: Coating thickness 52μm, surface roughness Ra=1.7μm, solar absorptivity α S =0.36, hemispherical emissivity ε H =0.83, microhardness reaches 320HV, corrosion area is 6.8% after 96h of neutral salt spray test, and powdering occurs in some areas of the coating after 16 thermal cycles (-150℃ to +150℃). Without the addition of zirconium dioxide nanoparticles, the thermal control performance of the micro-arc oxidation film is much lower than that with the addition of zirconium dioxide nanoparticles.

[0044] Comparative Example 2 (compared to titanium dioxide nanoparticles): 1. Magnesium alloy workpiece: Mg-Li alloy plate (36mm×36mm×3mm) is selected. 2. Preparation of Nano-Modified Electrolyte: Add 15L of deionized water to a 20L sealed electrolytic cell and start the vacuum gas stirring system (compressed air flow rate 1.5L / min). Add 60g / L (900g) sodium silicate, 7g / L (105g) sodium dihydrogen phosphate, 4g / L (60g) sodium hydroxide, and 0.5g / L (7.5g) sodium dodecylbenzenesulfonate sequentially. Stir for 40min until completely dissolved, then add 30g / L (450g) of 50nm titanium dioxide nanoparticles. Ultrasonic dispersion power density: 1.2W / cm³. 3 The frequency was 40 kHz, and the time was 60 min. Mechanical stirring was then continued for 24 h to form a stable suspension. After the electrolyte settled, the measured conductivity was 28 mS / cm, pH = 13.2, the sedimentation rate was 1.2% after 48 h, and the zeta potential of TiO2 particles was -56 mV, confirming that the dispersion stability met the standards. 3. Micro-arc oxidation process: The workpiece is clamped on an aluminum alloy fixture, the surface of which is treated with hard anodizing for insulation. Process parameters are set as follows: voltage 600V (stepped mode: voltage increases to 600V from 0 to 1 minute, and is maintained for the remaining time), current density 8A / dm³.2 The treatment time was 40 minutes, the electrolyte temperature was 32±2℃ (with gas stirring and cooling system working together), the frequency was 1000Hz, and the duty cycle was 12%. The high frequency and low duty cycle combined with gas stirring resulted in dense, dotted discharge micro-arcs, bluish-white in color, without macroscopic arc spots, and uniform film growth. After treatment, the workpiece surface was uniformly bluish-gray with good color consistency. 4. Performance Testing: Coating thickness 67μm, surface roughness Ra=1.9μm, solar absorptivity α S =0.42, hemispherical emissivity ε H =0.84, microhardness reaches 360HV, corrosion area is 5.4% after 96h of neutral salt spray test, and the coating remains intact after 2000 thermal cycles (-150℃~+150℃). With the addition of titanium dioxide nanoparticles, the solar absorptivity of the film is significantly increased, but the performance is far lower than that of the micro-arc oxidation film with zirconium dioxide nanoparticles.

[0045] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A nanoparticle-modified electrolyte, characterized in that, It includes silicates, phosphates, hydroxides, and zirconium dioxide nanoparticles; the concentration of the zirconium dioxide nanoparticles is 5~50 g / L, and the particle size is 20~50 nm.

2. The electrolyte according to claim 1, characterized in that, It includes 30-60 g / L of silicates, 3-10 g / L of phosphates, 2-10 g / L of hydroxides, and 5-50 g / L of zirconium dioxide nanoparticles.

3. The electrolyte according to claim 1 or 2, characterized in that, The silicate includes sodium silicate, the phosphate includes sodium dihydrogen phosphate, and the hydroxide includes sodium hydroxide.

4. The electrolyte according to claim 1, characterized in that, It also includes a dispersant selected from any one of sodium citrate, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate.

5. The application of the electrolyte according to any one of claims 1-4 in the preparation of micro-arc oxidation thermal control coatings.

6. A thermal control coating, characterized in that, It is formed by micro-arc oxidation of the electrolyte according to any one of claims 1-4.

7. The method for preparing the thermal control coating according to claim 6, characterized in that, include: Using a magnesium alloy as the anode and a stainless steel plate as the cathode, the material is placed in the electrolyte described in any one of claims 1-4 for micro-arc oxidation to obtain the thermal control coating on the surface of the magnesium alloy.

8. The preparation method according to claim 7, characterized in that, The process parameters for micro-arc oxidation include: Frequency 500~1000Hz, duty cycle 10~20%.

9. The preparation method according to claim 7 or 8, characterized in that, The micro-arc oxidation is carried out using a vacuum gas stirring system that introduces inert gas or compressed air for assistance.

10. A thermal control component, characterized in that, It includes a magnesium alloy substrate and a thermal control coating disposed on the surface of the magnesium alloy substrate, wherein the thermal control coating includes the thermal control coating of claim 6.

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