A method for preparing a corrosion-resistant coating

Abstract

The application provides a corrosion-resistant coating preparation method and relates to the technical field of semiconductor processing. The application forms a multi-level and high-performance corrosion-resistant coating system through the construction of a micro-arc oxidation ceramic transition layer, the precise regulation of a chelating agent on a rare earth sol and the application of ultraviolet light curing technology. The method not only significantly improves the adhesion of the coating to the substrate, the uniformity of the coating and the curing efficiency, but more importantly, effectively regulates the micro-chemical state of the corrosion-resistant functional layer, thereby optimizing the coating performance according to specific application requirements and effectively solving the severe challenges faced by the surface protection of the aluminum cavity of a remote plasma source in the field of semiconductor equipment manufacturing.

Description

Technical Field

[0001] This application relates to the field of semiconductor processing technology, and more specifically, to a method for preparing a corrosion-resistant coating. Background Technology

[0002] In the semiconductor equipment manufacturing field, surface protection of aluminum cavities in remote plasma sources (RPS) faces severe challenges. Traditional technical solutions suffer from three key defects: First, the interface bonding mechanism between conventional sol-gel coatings and the aluminum substrate is weak, relying mainly on physical adsorption and random chemical bonding. Under continuous plasma bombardment and thermal stress cycling, the coating is prone to interfacial delamination, leading not only to protective failure but also to particulate contaminants polluting the process environment. Second, existing coating technologies struggle to adapt to the complex geometry of the cavity. Whether it's the capillary effect of dip coating or the uneven atomization of spray coating, uneven coating thickness or uncovered areas will form at critical locations such as cavity corners and threaded holes. These defective areas will become preferential corrosion initiation points under corrosive plasma. Third, there is a fundamental contradiction between traditional high-temperature sintering processes and the thermal stability of the aluminum substrate. When the processing temperature exceeds 400°C, the aluminum substrate will undergo irreversible softening and deformation; while if low-temperature curing is used, a large amount of organic components will remain inside the coating, forming a porous structure, significantly reducing its resistance to plasma penetration. Of particular note is the lack of effective means for controlling the microscopic chemical state of functional coatings in existing technologies. For example, in cerium-containing coating systems, trivalent cerium (Ce) 3+ ) and tetravalent cerium (Ce 4+ The ratio of ions directly affects the passivation ability of the coating in different corrosive media (such as fluorine-based and chlorine-based plasmas), but traditional processes cannot achieve controllable adjustment of this ratio, resulting in the inability to optimize the coating performance for specific application scenarios.

[0003] There is currently no effective technical solution to the above problems. Summary of the Invention

[0004] The purpose of this application is to provide a method for preparing a corrosion-resistant coating, which aims to solve the technical problems in the surface protection of aluminum cavity of remote plasma source (RPS) in the field of semiconductor equipment manufacturing, such as weak bonding between coating and substrate, poor coating uniformity, contradiction between curing process and thermal stability of aluminum substrate, and lack of effective means to control the micro-chemical state of functional coating.

[0005] In a first aspect, this application provides a method for preparing a corrosion-resistant coating, comprising the steps of: S1. Micro-arc oxidation treatment is performed on the aluminum substrate cavity to form a ceramic transition layer on the surface of the aluminum substrate cavity; S2. Prepare rare earth sols containing chelating agents; S3. Apply rare earth sol to the surface of the ceramic transition layer and perform ultraviolet curing treatment to form a corrosion-resistant functional layer.

[0006] This technical solution effectively solves the problems of poor adhesion and easy peeling of traditional coatings by constructing a ceramic transition layer and a corrosion-resistant functional layer on the surface of the aluminum substrate cavity. At the same time, it avoids damage to the aluminum substrate caused by high-temperature sintering and achieves the effective formation of the corrosion-resistant functional layer, thereby significantly improving the corrosion resistance and service life of the aluminum substrate cavity.

[0007] Optionally, step S1 includes: The aluminum-based cavity is placed in a silicate-based electrolyte; A bipolar pulse power supply is used to apply voltage to the aluminum substrate cavity, where bipolar means that the polarities of the two electrodes are opposite; By using micro-arc oxidation technology and controlling the micro-arc oxidation process parameters, a ceramic transition layer with a thickness ranging from 50±5 micrometers and a Vickers hardness ranging from 1200HV to 1500HV is grown in situ on the surface of an aluminum substrate cavity. The micro-arc oxidation process parameters include current density, frequency, duty cycle and processing time.

[0008] This technical solution employs a bipolar pulse power supply and silicate-based electrolyte for micro-arc oxidation treatment, which can precisely control the thickness and hardness of the ceramic transition layer, ensuring a good bond between the transition layer and the aluminum substrate, and providing a solid foundation for the adhesion of subsequent functional layers, effectively improving the overall mechanical properties and stability of the coating.

[0009] Optionally, the chelating agent includes acetylacetone, and the rare earth sol contains yttrium and cerium. The steps for preparing rare earth sols containing chelating agents include: A rare earth sol containing yttrium and cerium was prepared using acetylacetone. By controlling the amount of acetylacetone added (ranging from 0.05 ml to 0.30 ml), the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer was controlled within the range of 20% to 90%.

[0010] This technical solution effectively regulates the proportion of tetravalent cerium ions in the corrosion-resistant functional layer by precisely controlling the amount of acetylacetone added. This allows for the optimization of the passivation capability of the coating according to different corrosion environment requirements, solving the problem of uncontrollable microscopic chemical state of functional coatings in existing technologies.

[0011] Optionally, the steps of preparing a rare earth sol containing yttrium and cerium using acetylacetone, and controlling the amount of acetylacetone added (ranging from 0.05 ml to 0.30 ml) to ensure that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer is controlled within the range of 20% to 90%, include: Yttrium source, cerium source and acetylacetone are mixed in a beaker containing solvent. The amount of acetylacetone added is controlled to be in the range of 0.05ml-0.30ml. The beaker is then placed in a water bath at a preset temperature and stirred to obtain a mixed solution. Add deionized water to the mixed solution in steps while continuing to stir; Adjust the pH of the mixed solution to 3-4 using dilute nitric acid; The mixed solution after pH adjustment was aged to prepare a rare earth sol with a controllable proportion of tetravalent cerium ions, so that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer was controlled within the range of 20% to 90%.

[0012] Optionally, the solvent is anhydrous ethanol, the yttrium source is Y(NO3)3·6H2O, and the cerium source is Ce(NO3)3·6H2O.

[0013] Optionally, after the step of preparing a rare earth sol with a controllable proportion of tetravalent cerium ions, a filtration process is also included: The prepared rare earth sol was filtered using a polytetrafluoroethylene (PTFE) filter membrane.

[0014] Optionally, step S3 includes: using a spin coating process to coat the rare earth sol onto the surface of the ceramic transition layer in two stages, with the first stage coating at a preset first rotation speed and the second stage coating at a preset second rotation speed; The coated rare earth sol was then subjected to ultraviolet light curing treatment. By repeatedly performing spin coating and UV curing processes, a Y2O3-CeO2 composite layer is constructed on the surface of the ceramic transition layer as a corrosion-resistant functional layer.

[0015] Optionally, the first speed is 500rpm-800rpm, and the working time of the first stage is 10s-20s; the second stage is 3000rpm-5000rpm, and the working time of the second speed is 30s-60s.

[0016] Optionally, the step of UV curing the coated rare earth sol includes: A ceramic transition layer coated with rare earth sol was irradiated with excimer ultraviolet light with a wavelength of 172 nm. The photon energy of the excimer ultraviolet light was used to break the organic chemical bonds in the rare earth sol and to generate ozone and oxygen free radicals, thereby promoting the condensation reaction of the rare earth sol.

[0017] Optionally, before step S1, the method further includes the step: S0. The aluminum substrate cavity is cleaned using a three-step ultrasonic cleaning process, which includes sequentially using acetone, anhydrous ethanol and deionized water as cleaning media to remove organic matter, residual impurities and ionic contaminants from the surface of the aluminum substrate cavity.

[0018] As can be seen from the above, the corrosion-resistant coating preparation method provided in this application effectively solves the problems of poor adhesion between the coating and the substrate, easy peeling, insufficient coating uniformity, and contradiction between the curing process and the thermal stability of the aluminum substrate in the prior art by sequentially constructing a ceramic transition layer and a corrosion-resistant functional layer on the surface of the aluminum substrate cavity. Specifically, firstly, by performing micro-arc oxidation treatment on the aluminum substrate cavity, a ceramic transition layer with high hardness and a specific thickness is grown in situ on the substrate surface. This transition layer forms a metallurgical bond with the aluminum substrate, significantly enhancing the bonding strength between the coating and the substrate and overcoming the defect of weak interfacial bonding in traditional sol-gel coatings. Secondly, a rare earth sol containing a chelating agent is prepared and a corrosion-resistant functional layer is formed by ultraviolet light curing treatment, avoiding damage to the aluminum substrate caused by traditional high-temperature sintering and solving the problem of poor thermal stability of the aluminum substrate. In addition, by precisely controlling the amount of chelating agent added, the proportion of tetravalent cerium ions in the corrosion-resistant functional layer is effectively controlled, enabling the coating to optimize passivation ability for different corrosive media and overcoming the limitation of uncontrollable microscopic chemical state of functional coatings in the prior art. In summary, the technical solution of this application not only improves the adhesion, uniformity and density of the coating, but also achieves controllable optimization of the coating performance, providing an efficient, reliable and universal solution for the surface protection of aluminum cavities of remote plasma sources in the semiconductor equipment manufacturing field.

[0019] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart illustrating the corrosion-resistant coating preparation method provided in the embodiments of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] Firstly, referring to Figure 1 This application provides a method for preparing a corrosion-resistant coating, comprising the following steps: S1. Micro-arc oxidation treatment is performed on the aluminum substrate cavity to form a ceramic transition layer on the surface of the aluminum substrate cavity; S2. Prepare rare earth sols containing chelating agents; S3. Apply rare earth sol to the surface of the ceramic transition layer and perform ultraviolet curing treatment to form a corrosion-resistant functional layer.

[0024] Micro-arc oxidation involves applying high voltage to a metal (such as aluminum) in an electrolyte solution to induce micro-arc discharge on its surface, thereby growing a dense ceramic layer in situ on the metal surface. This ceramic layer typically possesses high hardness, wear resistance, and corrosion resistance, significantly improving the surface properties of the substrate.

[0025] Chelating agents: In the preparation of rare earth sols, chelating agents can stabilize rare earth elements and control their hydrolysis and condensation reaction rates, thereby affecting the microstructure and properties of the final coating, especially the proportion of rare earth ion valence states.

[0026] Rare earth sols: Rare earth elements are dispersed in a solvent in the form of nanoparticles or ion clusters. Rare earth sols are precursors for preparing rare earth oxide coatings, which can be cured to form rare earth oxide coatings with specific functions (such as corrosion resistance).

[0027] Ultraviolet (UV) curing: A method that rapidly solidifies liquid resin or sol into a solid coating. Compared with traditional thermal curing, UV curing has advantages such as fast curing speed, low energy consumption, and minimal thermal damage to the substrate, making it particularly suitable for heat-sensitive substrates.

[0028] Corrosion-resistant functional layer: This functional layer can effectively isolate the corrosive medium from the base material, thereby protecting the base material from corrosion and extending its service life.

[0029] The following example will provide a more detailed explanation of the above technical solution: Assuming a corrosion-resistant coating is required for the RPS aluminum cavity to meet the long-term protection needs in a highly oxidizing CF4 / O2 plasma environment (CF4 content 30%), the high Ce content of this invention is employed. 4+ Group rare earth sol formulation (expected Ce) 4+ The coating preparation was verified by using a ratio of 80-90%.

[0030] First, the aluminum substrate cavity undergoes pretreatment. This involves a three-step ultrasonic cleaning process, using acetone, anhydrous ethanol, and deionized water sequentially as cleaning media to thoroughly remove organic matter, residual impurities, and ionic contaminants from the surface of the aluminum substrate cavity. For example, the cavity is ultrasonically cleaned in acetone for 5 minutes to remove grease; then transferred to anhydrous ethanol for ultrasonic cleaning for 3 minutes to remove residual impurities; finally, it is ultrasonically cleaned in deionized water for 5 minutes and repeated once to thoroughly remove ethanol residue, followed by drying.

[0031] Next, the cleaned aluminum substrate cavity was subjected to micro-arc oxidation treatment. The aluminum substrate cavity was used as the anode, and a 316L stainless steel plate as the cathode, placed in a silicate-based electrolyte. A bipolar pulse power supply was used to apply voltage to the aluminum substrate cavity, and the micro-arc oxidation process parameters were strictly controlled, such as a current density of 10-15 A / dm², a frequency of 500 Hz, a duty cycle of 20%-30%, and a treatment time of 60±10 minutes. Through high-voltage discharge, a dense ceramic transition layer was grown in situ on the aluminum substrate surface. After the micro-arc oxidation treatment, the aluminum substrate cavity was removed, and the surface was rinsed with high-pressure deionized water to remove any residual silicate-based electrolyte. It was then placed in an 80°C forced-air drying oven for 50 minutes to obtain a cavity with an alumina transition layer on its surface. The thickness of this transition layer was precisely controlled at 50±5 µm, and its Vickers hardness reached 1200-1500 HV, forming a strong metallurgical bond with the aluminum substrate. This step solves the problem of insufficient adhesion between traditional coatings and the substrate, providing a solid foundation for the adhesion of subsequent functional layers.

[0032] Next, rare earth sols containing chelating agents are prepared. For example, acetylacetone (ACAC) is used to prepare rare earth sols containing yttrium and cerium. The specific procedure is as follows: 15 ml of anhydrous ethanol is added to a 50 ml glass beaker as the base solvent, and different volumes of anhydrous ethanol are added according to different experimental groups (high Ce content). 4+ Add 0.25ml to the group, medium content Ce4+ Add 0.15ml of low-concentration Ce to the group. 4+ (No additional additives needed). Weigh 0.364g Y(NO3)3·6H2O and 0.022g Ce(NO3)3·6H2O, and add them together to a glass beaker. Place the glass beaker in a 40℃ constant temperature water bath and magnetically stir at 500rpm for 15 minutes to completely dissolve the solid raw materials. Then, accurately pipette 0.05ml ACAC into the glass beaker, and continue to maintain the 40℃ water bath and magnetic stirring at 500rpm for 30 minutes. Use a small amount of ACAC to promote the dissolution of Ce. 3+ To Ce 4+ The process involved two separate additions of 0.05 ml deionized water, with stirring at 500 rpm for 20 minutes after each addition to slowly promote the sol hydrolysis reaction. The pH of the solution was adjusted to 3.6 using 0.1 mol / L dilute nitric acid, ensuring the pH remained within the 3-4 range. Finally, the prepared solution was aged in a 50°C oven for 30 minutes to promote the hydrolysis-condensation reaction equilibrium and improve sol stability. After aging, the prepared rare earth sol was slowly injected using a syringe with a 0.22 µm polytetrafluoroethylene filter membrane to filter out solid impurities, resulting in a clear and transparent rare earth sol. The proportion of tetravalent cerium ions in the rare earth sol was detected to be 80%-90%. Two control groups with a medium Ce content were also prepared. 4+ Group and low content of Ce 4+ All groups were prepared using the same steps described above, among which the medium-content Ce 4+ The anhydrous ethanol replenishment volume for this group was 0.15 ml, corresponding to an ACAC addition volume of 0.15 ml. The proportion of tetravalent cerium ions in the rare earth sol was detected to be 50%-65%; low Ce content... 4+ No anhydrous ethanol was added to the group, and the corresponding amount of ACAC added was 0.30 ml. The proportion of tetravalent cerium ions in the rare earth sol was detected to be 20%-30%.

[0033] By controlling the amount of ACAC added, the chelation balance relationship (Ce) can be utilized. 3+ +3ACAC Ce(ACAC)3+3H + The above three sets of data can verify that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer can be controlled within the range of 20% to 90%, thereby achieving precise control of the coating's microstructure parameters to adapt to corrosion mechanisms under different plasma atmospheres.

[0034] Finally, the rare earth sol was coated onto the surface of the ceramic transition layer and cured under ultraviolet light. Using an existing vertical spin coating apparatus, the aluminum substrate cavity with the ceramic transition layer was fixed on the apparatus's vacuum rotary fixture. The spin speed curve was set as follows: the first stage was 500 rpm for 10 seconds (low-speed sol spreading), and the second stage was 3000 rpm for 30 seconds (high-speed control of film thickness). 3 ml of the prepared rare earth sol (high Ce content) was pipetted using a 5 ml pipette. 4+ The coating process involves uniformly dripping the coating material from the top of the aluminum substrate cavity onto the inner wall surface, and then starting the spin coating equipment according to the set rotation speed curve. After spin coating, the cavity is immediately transferred to a 172nm excimer ultraviolet curing device, where the ultraviolet light flux density is set to 58mW / cm², and the coating is cured for 9 minutes. This spin coating-curing cycle is repeated 9 times to construct a Y₂O₃-CeO₂ composite layer as a corrosion-resistant functional layer on the surface of the ceramic transition layer. This spin coating process, combined with ultraviolet curing, solves the problems of uneven coating and substrate damage caused by high-temperature sintering in traditional methods. Ultraviolet curing utilizes high-energy photons to break the organic chemical bonds in the rare earth sol and excite the generation of ozone and oxygen free radicals, promoting the condensation reaction of the sol. This achieves the decomposition of organic components and the formation of an inorganic oxide network at temperatures below 150°C, avoiding thermal damage to the aluminum substrate.

[0035] After curing, the aluminum substrate cavity was removed for observation. The functional layer was uniformly transparent, without obvious scratches, and the film layer was well bonded to the substrate. Using this spin-coating process combined with UV curing technology, a uniformly thick Y2O3-CeO2 composite layer as a corrosion-resistant functional layer can be constructed on the surface of the ceramic transition layer. This Y2O3-CeO2 composite layer has a dense structure, consistent with high Ce content... 4+ Group coating performance requirements.

[0036] During the actual spin coating process, the rotation speed can be monitored in real time using the equipment's built-in speed monitoring system to ensure that the speed fluctuation does not exceed ±3 rpm. After every three curing cycles, the power of the 172nm ultraviolet light source is measured using an ultraviolet power meter to ensure that the power attenuation does not exceed 4%. If it does, the light source should be replaced promptly. The aluminum substrate cavity with the prepared coating is placed in a CF4 / O2 plasma corrosion test environment and continuously corroded for 60 minutes. After that, it is removed and observed. If the coating has no defects such as peeling or cracks, and there are no obvious corrosion marks on the inner wall of the cavity, it meets the high Ce standard. 4+ The design aims to meet the long-life protection requirements of aluminum-based cavities in high-oxidation plasma environments. Among these, Ce in rare-earth sol... 4+ The content of [specific component] is an adjustable formula parameter that can be adjusted according to the actual requirements of corrosion resistance.

[0037] The above-mentioned technical solution utilizes micro-arc oxidation to grow a dense ceramic transition layer, primarily composed of α-Al₂O₃, on the surface of an aluminum substrate, forming a strong metallurgical bond with the aluminum substrate. This effectively solves the problem of insufficient adhesion between traditional coatings and the substrate. Compared to traditional sol-gel coatings, which mainly rely on physical adsorption and limited chemical bonding, the ceramic transition layer of this application provides stable interfacial support, significantly improving the coating's resistance to peeling.

[0038] Furthermore, this application achieves precise control over the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer by formulating a rare-earth sol containing a chelating agent and accurately controlling the amount of chelating agent added. This technique solves the problem of existing coating systems lacking the ability to precisely control key microstructural parameters. For example, in cerium oxide doped systems, Ce... 3+ / Ce 4+ The ratio has a decisive influence on the corrosion mechanism and durability under different plasma atmospheres. This application can optimize the coating performance according to different process gases (such as CF4, Cl2, NF3), improving the coating's applicability and lifespan under varying operating conditions, which is impossible to achieve with traditional formulation processes.

[0039] Finally, this application employs a spin coating process combined with UV curing to form a corrosion-resistant functional layer. Spin coating effectively solves the problem of traditional coating processes (such as dip coating and spray coating) being limited by the "masking effect" and "edge accumulation" phenomena of hydrodynamics, making it difficult to achieve uniform coverage of nanoscale films in complex areas. Through staged spin coating, uniform coverage of complex areas such as unevenness and gaps inside the RPS cavity is ensured, avoiding localized weak protection. Simultaneously, UV curing avoids the problem of traditional sol-gel technologies relying on high-temperature sintering (e.g., sintering temperatures above 800℃) to achieve sufficient densification and crystallization of the coating. High-temperature sintering far exceeds the thermal stability limit of the aluminum substrate, leading to softening deformation and deterioration of mechanical properties in the cavity. The UV curing process in this application can achieve the decomposition of organic components and the formation of an inorganic oxide network at temperatures below 150℃, effectively protecting the integrity and mechanical properties of the aluminum substrate while ensuring the densification and crystallinity of the coating, avoiding problems such as organic residue and loose structure. In summary, the technical solution of this application demonstrates significant technological progress and innovation in terms of bonding strength, uniformity, matrix protection, and microstructure control.

[0040] In some implementations, step S1 includes: The aluminum-based cavity is placed in a silicate-based electrolyte; A bipolar pulse power supply is used to apply voltage to the aluminum substrate cavity, where bipolar means that the polarities of the two electrodes are opposite; By using micro-arc oxidation technology and controlling the micro-arc oxidation process parameters, a ceramic transition layer with a thickness ranging from 50±5 micrometers and a Vickers hardness ranging from 1200HV to 1500HV is grown in situ on the surface of an aluminum substrate cavity. The micro-arc oxidation process parameters include current density, frequency, duty cycle and processing time.

[0041] Silicate-based electrolytes, used as reaction media in micro-arc oxidation processes, primarily provide silicate and oxygen ions necessary for ceramic layer formation and serve as a conductive medium. The preparation of the silicate-based electrolyte involves dissolving 85 g / L Na₂SiO₃, 12 g / L NaOH, and 6 g / L Na₂EDTA in an appropriate amount of deionized water in a 15 L plastic electrolytic cell. After thorough stirring until completely dissolved, the solution is transferred to a volumetric container and brought to a final volume of 15 L with deionized water. The mixture is then stirred until homogeneous, yielding a silicate-based electrolyte with a pH of 12.0. The silicate-based electrolyte is crucial for ensuring the uniform growth and density of the ceramic transition layer, preventing localized uneven reactions or defects caused by inappropriate electrolyte composition. A bipolar pulse power supply is used to apply voltage to the aluminum substrate cavity; this bipolar pulse power supply is a power device capable of alternately applying forward and reverse voltages. In the micro-arc oxidation process, a bipolar pulsed power supply is used to apply voltage. The positive pulse promotes the growth and densification of the oxide film, while the reverse pulse suppresses local overheating, reduces film defects, and promotes the release of internal stress, thereby improving the quality and uniformity of the ceramic layer. The bipolar pulsed power supply can be controlled in various ways, such as by adjusting the width, amplitude, frequency, and duty cycle of the positive and negative pulses to achieve precise control of the micro-arc oxidation process. Using the micro-arc oxidation process, by controlling the process parameters, a ceramic transition layer with a thickness ranging from 50±5 micrometers and a Vickers hardness ranging from 1200HV to 1500HV is grown in situ on the surface of an aluminum substrate cavity. The micro-arc oxidation process parameters include current density, frequency, duty cycle, and processing time. Micro-arc oxidation is a technology for in-situ growth of ceramic oxide films on metal surfaces. Its core lies in inducing micro-arc discharge on the metal surface through high-voltage discharge, thereby forming a dense ceramic layer on the substrate surface. The realization of this process relies on the precise control of a series of key parameters, including current density, frequency, duty cycle, and processing time. Current density determines the intensity of the micro-arc discharge and the growth rate of the film; frequency and duty cycle affect the energy distribution of the pulse and the compactness of the film; and processing time directly determines the final thickness of the film. By synergistically regulating these parameters, the physical properties of the formed ceramic transition layer, such as thickness, hardness, and porosity, can be precisely controlled to meet specific application requirements.

[0042] This solution ensures the quality and performance of the ceramic transition layer by optimizing the implementation details of the micro-arc oxidation process. First, the aluminum substrate cavity is placed in a silicate-based electrolyte. This electrolyte, acting as a reaction medium, not only provides the ions needed to form the alumina ceramic layer but also promotes uniform growth of the ceramic layer through its specific chemical composition, effectively avoiding localized uneven reactions or defects that may occur with traditional electrolytes. Second, a bipolar pulse power supply is used to apply voltage to the aluminum substrate cavity. Bipolarity refers to the opposite polarity of the two electrodes; this power supply mode allows for alternating application of forward and reverse pulses. The forward pulse promotes rapid growth and densification of the oxide film, while the reverse pulse helps suppress localized overheating, reduce internal stress in the film, and promote defect repair, thereby significantly improving the uniformity and density of the ceramic layer. Finally, by precisely controlling the micro-arc oxidation process parameters, including current density, frequency, duty cycle, and processing time, fine-tuning of the ceramic transition layer growth process is achieved. Current density affects the intensity of the micro-arc discharge and the film growth rate, while frequency and duty cycle synergistically influence the distribution of pulse energy and the densification of the film structure. Processing time directly determines the final film thickness. Through the synergistic effect of these parameters, a ceramic transition layer with a thickness ranging from 50±5 micrometers and a Vickers hardness ranging from 1200HV to 1500HV can be grown in situ on the surface of an aluminum substrate cavity. This ceramic transition layer with its specific thickness and hardness range not only possesses excellent mechanical strength and wear resistance, but more importantly, it forms a strong metallurgical bond with the aluminum substrate, providing a solid and stable foundation for the subsequent adhesion of corrosion-resistant functional layers.

[0043] As a specific implementation method, step S1 can be carried out as follows: First, the cleaned RPS aluminum cavity is used as the anode and placed in a silicate-based electrolyte. Then, a bipolar pulse power supply is used to apply voltage to the aluminum substrate cavity. During the micro-arc oxidation process, process parameters can be strictly controlled, such as setting the current density to 10-15 A / dm², the frequency to 500 Hz, the duty cycle to 20%-30%, and the processing time to 60±10 minutes. Through high-voltage discharge, a dense ceramic layer mainly composed of α-Al₂O₃ is grown in situ on the surface of the aluminum substrate cavity. The thickness of this ceramic transition layer can be precisely controlled to 50±5 micrometers, forming a strong metallurgical bond with the aluminum substrate, and its Vickers hardness can reach 1200HV-1500HV.

[0044] Through the above technical solution, this application can precisely control the micro-arc oxidation process, thereby forming a ceramic transition layer with a specific thickness and hardness range on the surface of the aluminum substrate cavity. This ceramic transition layer is not only uniform in thickness and high in hardness, but also forms a strong metallurgical bond with the aluminum substrate cavity, effectively solving the problems of unstable quality, uneven thickness, insufficient hardness, or poor adhesion of the ceramic transition layer in traditional micro-arc oxidation processes. Therefore, the formed ceramic transition layer can provide a stable, dense, and mechanically strong substrate for the subsequent corrosion-resistant functional layer, significantly improving the overall performance and reliability of the entire corrosion-resistant coating system. Especially under harsh conditions such as continuous plasma impact and thermal cycling, it can effectively prevent early coating peeling, thereby extending the service life of the RPS cavity.

[0045] In some embodiments, the chelating agent includes acetylacetone, and the rare earth sol contains yttrium and cerium. The steps for preparing rare earth sols containing chelating agents include: A rare earth sol containing yttrium and cerium was prepared using acetylacetone. By controlling the amount of acetylacetone added (ranging from 0.05 ml to 0.30 ml), the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer was controlled within the range of 20% to 90%.

[0046] Among the chelating agents is acetylacetone. Acetylacetone is an organic compound with a unique molecular structure. Its active methylene group can form a stable chelate ring with metal ions, thus playing a crucial role in the sol-gel system. As a chelating agent, acetylacetone can effectively inhibit the hydrolysis and condensation reaction rates of rare earth metal ions, preventing premature precipitation or the formation of uneven particles, ensuring the stability and homogeneity of the sol system. Furthermore, the addition of acetylacetone can also affect the redox potential of the system, thereby regulating the valence balance of cerium ions.

[0047] Rare earth sols contain yttrium and cerium. A rare earth sol is a colloidal solution formed by dispersing rare earth metal ion precursors in a solvent. Subsequent hydrolysis and condensation reactions can form nanoscale oxide particles. Yttrium (Y) and cerium (Ce) are two important rare earth elements, exhibiting excellent physicochemical properties in their oxide forms (Y₂O₃ and CeO₂). Yttrium oxide (Y₂O₃) is commonly used as a structural stabilizer, significantly improving the density, hardness, and thermal stability of coatings, and enhancing their mechanical properties. Cerium oxide (CeO₂), on the other hand, possesses unique Ce₂ content. 3+ / Ce 4+ The variable valence state characteristic has attracted much attention, which makes it exhibit excellent performance in catalysis, ultraviolet absorption, and corrosion resistance. Combining these two elements in rare earth sol aims to prepare a composite coating with both excellent structural stability and tunable functionality.

[0048] The amount of acetylacetone added is controlled within the range of 0.05 ml to 0.30 ml. The amount of acetylacetone added is one of the key parameters for precisely controlling the properties of rare earth sols. An appropriate amount of acetylacetone ensures that rare earth metal ions are fully chelated, thereby effectively controlling the rate of hydrolysis and condensation reactions, preventing excessively rapid gel formation or precipitation, and ensuring the stability and uniformity of the sol. Simultaneously, the amount of acetylacetone added also affects the pH and redox potential of the sol system, thus influencing the valence state balance of cerium ions. By precisely controlling its addition within a specific range, the proportion of tetravalent cerium ions in the final coating can be effectively controlled to meet the performance requirements under different corrosive environments. The amount of acetylacetone added can be adjusted according to the concentration of rare earth metal ions, the type of solvent, and the desired reaction rate and valence state control targets.

[0049] This application describes a method for preparing rare earth sols by introducing acetylacetone as a chelating agent and combining it with yttrium and cerium. Acetylacetone can form stable chelates with cerium ions. By controlling the amount of acetylacetone added, the chelating equilibrium relationship, such as Ce, can be utilized. 3+ + 3ACAC Ce(ACAC)3+3H + This method allows for precise control of the valence state balance of cerium ions in the rare earth sol, enabling programmable adjustment of the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer within the range of 20% to 90%. The presence of yttrium helps enhance the structural stability and mechanical properties of the coating. This precise valence state control capability allows the coating to be optimized for different plasma atmospheres (such as oxidizing or reducing environments), thus maintaining excellent corrosion resistance under various working conditions. After being coated onto the surface of an aluminum substrate cavity treated with micro-arc oxidation, the rare earth sol forms a good bond with the ceramic transition layer, further enhancing the overall protective capability of the entire coating system. In this way, the proposed solution effectively solves the problem of unstable corrosion resistance caused by insufficient cerium ion valence state control in traditional technologies, significantly improving the applicability and lifespan of the coating in complex plasma environments.

[0050] In some embodiments, the step of preparing a rare earth sol containing yttrium and cerium using acetylacetone, and controlling the amount of acetylacetone added (ranging from 0.05 ml to 0.30 ml) to ensure that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer is controlled within the range of 20% to 90% includes: Yttrium source, cerium source and acetylacetone are mixed in a beaker containing solvent. The amount of acetylacetone added is controlled to be in the range of 0.05ml-0.30ml. The beaker is then placed in a water bath at a preset temperature and stirred to obtain a mixed solution. Add deionized water to the mixed solution in steps while continuing to stir; Adjust the pH of the mixed solution to 3-4 using dilute nitric acid; The mixed solution after pH adjustment was aged to prepare a rare earth sol with a controllable proportion of tetravalent cerium ions, so that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer was controlled within the range of 20% to 90%.

[0051] In the above technical solution, yttrium source, cerium source, and acetylacetone are mixed in a beaker containing solvent. The yttrium and cerium sources are compounds providing yttrium and cerium, respectively, and are the basic components for forming rare earth sols. The yttrium source can be yttrium nitrate, yttrium chloride, or yttrium acetate, etc., and the cerium source can be cerium nitrate, cerium chloride, or cerium acetate, etc. Acetylacetone acts as a chelating agent; controlling the amount added (ranging from 0.05 ml to 0.30 ml) allows it to influence the valence transformation of cerium ions from the initial mixing stage, which is a key factor in achieving controllable tetravalent cerium ion proportions. The solvent is used to dissolve the yttrium source, cerium source, and acetylacetone, ensuring uniform dispersion of the reactants. Common solvents include anhydrous ethanol, isopropanol, or methanol. The beaker is the container for the mixing reaction and can be a glass beaker, plastic beaker, or reaction vessel, etc. The mixing process aims to ensure thorough contact and uniform dispersion of the components. Besides magnetic stirring, mechanical stirring or ultrasonic dispersion can also be used. Subsequently, the beaker is placed in a water bath at a preset temperature and stirred to obtain a mixed solution. The water bath environment precisely controls the reaction temperature, promotes the stable progress of the chelation reaction, and avoids localized overheating or uneven temperature distribution. Stirring further ensures the homogeneity of the solution and accelerates the reaction process. Next, deionized water is added to the mixed solution in stages while stirring continues. The purpose of adding deionized water in stages is to slowly initiate the hydrolysis reaction of the sol, effectively avoiding precipitation or aggregation caused by rapid dilution or excessively fast hydrolysis, thereby maintaining the homogeneity and stability of the sol. Deionized water can be added in small, multiple portions or slowly dripped using a peristaltic pump. Continuous stirring ensures the uniformity of the hydrolysis reaction. Finally, the pH of the mixed solution is adjusted to 3-4 using dilute nitric acid. Dilute nitric acid, as a pH adjuster, creates a suitable acidic environment crucial for optimizing the redox conditions of cerium ions, directly affecting the efficiency and final proportion of their conversion from trivalent to tetravalent. Besides dilute nitric acid, dilute hydrochloric acid or dilute acetic acid can also be used for adjustment. pH monitoring and control can be achieved in real-time using a pH meter, pH test strips, or an automatic titrator. Furthermore, the pH-adjusted solution undergoes aging. Aging is an important maturation process that allows for slow structural rearrangement and condensation reactions within the sol system, thereby enhancing the stability of the sol and the density of the final coating, preventing the cerium ion valence ratio from drifting in subsequent steps. Aging can be carried out in an oven, at room temperature, or in a constant temperature chamber, thus preparing a rare earth sol with a controllable tetravalent cerium ion ratio, ensuring that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer is controlled within the range of 20% to 90%. Acetylacetone is a key chelating agent in this step, and its amount directly determines the proportion of tetravalent cerium ions generated.By precisely controlling the total amount of acetylacetone added, combined with the synergistic effect of the aforementioned steps, the proportion of tetravalent cerium ions can be repeatedly adjusted within the target range. The amount of acetylacetone added can be controlled using a precision pipette, burette, or precision pump.

[0052] The method described in this application achieves precise and controllable preparation of the tetravalent cerium ion ratio in rare earth sols through the above steps, thus laying the foundation for subsequent performance optimization of the corrosion-resistant functional layer. First, yttrium source, cerium source, and acetylacetone are mixed in a solvent. By controlling the amount of acetylacetone added and stirring in a water bath at a preset temperature, this initial stage ensures that the reactants are fully dissolved and initially chelated under uniform and stable temperature conditions, creating favorable conditions for subsequent valence state control. Acetylacetone begins to exert its chelating effect at this stage, affecting the initial valence state equilibrium of cerium ions. Subsequently, deionized water is added stepwise with continuous stirring. This aims to prevent aggregation or precipitation in the sol system through a slow hydrolysis reaction, maintaining its uniformity and stability, which is crucial for the stable control of the cerium ion valence state. Next, the pH of the mixed solution is adjusted to 3-4 using dilute nitric acid. This specific acidic environment is carefully selected to optimize the redox conditions of cerium ions, directly affecting the efficiency of their conversion from trivalent to tetravalent, thus providing a chemical driving force for achieving the target ratio. Subsequently, the pH-adjusted mixed solution is aged, a process that allows the sol system to fully mature, enhancing structural density and ionic stability, and effectively preventing the controlled cerium ion valence ratio from drifting during subsequent processing. Therefore, by precisely controlling the amount of acetylacetone added, keeping the total addition within the range of 0.05ml-0.30ml, the chelation balance of cerium ions can be further finely controlled, thereby preparing a rare earth sol with a controllable tetravalent cerium ion ratio within the range of 20% to 90%. This method, closely integrated with other steps in the aforementioned corrosion-resistant coating preparation method, jointly solves the problem in existing technologies where coatings cannot be optimized for different process gases. Specifically, the rare earth sol prepared by this method allows for precise setting of the tetravalent cerium ion ratio according to actual needs. When this sol is coated onto a ceramic transition layer formed on the surface of an aluminum substrate cavity and cured under ultraviolet light to form a corrosion-resistant functional layer, the valence ratio of cerium ions in the functional layer directly affects its corrosion behavior and durability under different plasma atmospheres (such as CF4, Cl2, NF3). For example, in some plasma environments, a high proportion of tetravalent cerium ions may provide superior corrosion resistance, while in others, a lower proportion may be required. This solution provides a means to programmably control the valence state of cerium ions, enabling the final corrosion-resistant functional layer to be "customized" according to specific plasma process requirements. This significantly improves the coating's applicability and service life under varying operating conditions, effectively avoiding early failure and cavity contamination problems caused by coating performance mismatch.

[0053] The following is a specific example to illustrate this. In preparing a rare earth sol with a controllable tetravalent cerium ion ratio, firstly, 15 ml of anhydrous ethanol is added to a 50 ml glass beaker, and 0.25 ml of anhydrous ethanol is added as needed to prepare a sol with a high tetravalent cerium ion composition. Then, 0.364 g of Y(NO3)3·6H2O and 0.022 g of Ce(NO3)3·6H2O are weighed and added to the beaker. The beaker is placed in a 40°C constant temperature water bath and magnetically stirred at 500 rpm for 15 minutes to ensure that all solid raw materials are completely dissolved and a homogeneous solution is formed. Next, 0.05 ml of acetylacetone is accurately pipetted into the beaker using a 100 µl pipette, and magnetic stirring continues for 30 minutes at 40°C and 500 rpm. The chelating properties of acetylacetone promote the conversion of trivalent cerium ions to tetravalent cerium ions, forming a preliminarily stable solution. Following this, 0.05 ml of deionized water was added to the above mixed solution in two separate additions, with stirring at 500 rpm for 20 minutes after each addition to slowly promote the hydrolysis reaction of the sol and avoid local aggregation. Subsequently, the pH of the solution was adjusted to 3.6 using 0.1 M dilute nitric acid, while simultaneously monitoring the pH in real time to ensure it remained within the range of 3-4. Finally, the pH-adjusted mixed solution was placed in a 50°C oven for aging for 30 minutes to promote the hydrolysis-condensation reaction to reach equilibrium, thereby improving the stability of the rare earth sol. Through the above specific operations, a rare earth sol with a controllable proportion of tetravalent cerium ions can be prepared; for example, a sol in which the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer is controlled within the range of 20% to 90%.

[0054] Through the above technical solution, this application provides a method for precisely and programmably controlling the proportion of tetravalent cerium ions in rare earth sols. This method effectively solves the problem of the lack of effective means for programmably controlling the valence state of cerium ions in existing technologies by optimizing the sol preparation process, including refined mixing, stepwise hydrolysis, precise pH adjustment, and aging treatment, combined with precise control of the amount of acetylacetone added. Specifically, this solution ensures that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer is precisely controlled within the range of 20% to 90%. This precise control capability allows the coating to be "customized" and optimized according to the specific corrosion mechanisms and durability requirements of the RPS cavity under different plasma atmospheres (such as CF4, Cl2, NF3). For example, in plasma environments requiring higher oxidation resistance, a coating with a higher proportion of tetravalent cerium ions can be prepared; while in environments requiring specific catalytic activity, the proportion can be adjusted to a more suitable level. Therefore, this solution significantly improves the adaptability of the corrosion-resistant functional layer to varying operating conditions, extends the service life of the aluminum substrate cavity, and effectively reduces the risk of cavity corrosion and particulate contamination caused by coating performance mismatch.

[0055] In some embodiments, the solvent is anhydrous ethanol, the yttrium source is Y(NO3)3·6H2O, and the cerium source is Ce(NO3)3·6H2O.

[0056] Using anhydrous ethanol as a solvent effectively avoids interference from impurities introduced by moisture, ensuring the uniformity of the sol during mixing and subsequent processing. The pure environment of anhydrous ethanol is conducive to the complete dissolution and stable existence of rare earth salt precursors, reducing precipitation or aggregation caused by excessively rapid hydrolysis, thus ensuring the homogeneity of the sol system. Meanwhile, Y(NO3)3·6H2O and Ce(NO3)3·6H2O were chosen as the yttrium source and cerium source, respectively, both of which are nitrate precursors with good solubility and stability. They can dissolve rapidly and completely in anhydrous ethanol, providing high-purity yttrium and cerium ions. In particular, for the cerium source, cerium nitrate hexahydrate ensures that cerium ions readily combine with chelating agents (such as acetylacetone) to form stable complexes. This stable complexation is key to precisely controlling the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer by controlling the amount of chelating agent added. In the above steps for preparing rare earth sol containing chelating agents, yttrium source, cerium source, and a predetermined amount of acetylacetone are mixed in a beaker containing solvent and stirred in a water bath to obtain a mixed solution. Subsequently, deionized water is added to the mixed solution stepwise while stirring continues. The pH of the mixed solution is adjusted using dilute nitric acid, and then aged. By using the specific solvent and rare earth source materials described above, it is ensured that rare earth elements exist stably and uniformly in the solution throughout the sol preparation process and react fully with the chelating agent. This makes it possible to precisely control the proportion of tetravalent cerium ions by adjusting the amount of acetylacetone added. This precise control is crucial for optimizing the performance of the corrosion-resistant functional layer under different plasma atmospheres, because Ce... 3+ / Ce 4+ The ratio directly affects the corrosion mechanism and durability of the coating. Therefore, the solution proposed in this application fundamentally improves the preparation quality of rare earth sol and the precision of cerium ion valence state control by optimizing the solvent and rare earth source materials, thereby enhancing the performance consistency and reliability of the corrosion-resistant functional layer.

[0057] Through the above technical solution, this application effectively solves the problems of impurity introduction, sol instability, and difficulty in precisely controlling the valence state of cerium ions caused by improper selection of solvents and source materials in the traditional sol preparation process by specifically defining the solvent and rare earth source materials. Using anhydrous ethanol as the solvent significantly reduces the risk of impurities introduced by water and excessively rapid hydrolysis, thereby ensuring the purity and uniformity of the rare earth sol. Simultaneously, the selection of Y(NO3)3·6H2O and Ce(NO3)3·6H2O as yttrium and cerium sources ensures the stability and high purity of the rare earth ion source and provides a basis for the effective complexation of cerium ions with the chelating agent. This optimization fundamentally improves the preparation quality of the rare earth sol, making it possible to precisely control the proportion of tetravalent cerium ions in the corrosion-resistant functional layer by controlling the amount of chelating agent added in subsequent steps. Ultimately, the solution proposed in this application can produce a more stable and reliable corrosion-resistant functional layer, thereby improving the durability and applicability of the coating in complex plasma environments and solving the technical bottleneck of poor coating performance consistency and inability to optimize for different working conditions in the prior art.

[0058] In some embodiments, after the step of preparing a rare earth sol with a controllable proportion of tetravalent cerium ions, a filtration process is also included: The prepared rare earth sol was filtered using a polytetrafluoroethylene (PTFE) filter membrane.

[0059] Filtration is a physical separation process designed to remove solid particulate impurities from liquids using porous media. Its function is to improve the purity and homogeneity of the solution, preventing solid particles from introducing defects in subsequent processes. This process can be achieved in various ways, such as gravity filtration, vacuum filtration, or pressure filtration, using filter media with different pore sizes to purify the sol. Polytetrafluoroethylene (PTFE) membranes are microporous membranes made of PTFE material, possessing excellent chemical inertness, corrosion resistance, high-temperature resistance, and a precise pore size distribution. Its chemical inertness ensures that it will not chemically react with rare earth sols during filtration, thus avoiding the introduction of new impurities or alteration of the sol's chemical composition; the precise pore size distribution ensures efficient retention of particles of specific sizes while allowing effective components in the sol to pass through smoothly.

[0060] As a specific implementation method, after aging the pH-adjusted mixed solution, filtration can be performed immediately. Specifically, the aged rare earth sol is propelled through a 0.22µm pore size polytetrafluoroethylene (PTFE) filter membrane using a syringe. This process effectively removes any unreacted particles or polymers that may be present in the sol, resulting in a clear and transparent rare earth sol. For example, a syringe with a 0.22µm PTFE filter membrane can be used to slowly push the prepared rare earth sol in, filtering out solid impurities and ensuring the purity of the sol, laying the foundation for the subsequent formation of a high-quality corrosion-resistant functional layer.

[0061] The above-described technical solution, involving filtration after the preparation of the rare earth sol, effectively removes any undissolved particles or impurities that may be present in the sol. This prevents these particles from embedding into the corrosion-resistant functional layer during subsequent coating and curing processes, thereby significantly reducing the surface roughness and internal defects of the coating. The pure rare earth sol contributes to the formation of a denser and more uniform corrosion-resistant functional layer, improving the adhesion between the coating and the ceramic transition layer, and enhancing the coating's resistance to plasma corrosion. Combined with the previous precise control of the tetravalent cerium ion ratio, this filtration process further ensures the integrity of the functional layer's microstructure and the stability of its macroscopic properties, thus extending the coating's service life under complex operating conditions and reducing the risk of particle contamination due to coating failure.

[0062] In some embodiments, step S3 includes: using a spin coating process to coat rare earth sol onto the surface of the ceramic transition layer in two stages, wherein the first stage is coated at a preset first rotation speed and the second stage is coated at a preset second rotation speed. The coated rare earth sol was then subjected to ultraviolet light curing treatment. By repeatedly performing spin coating and UV curing processes, a Y2O3-CeO2 composite layer is constructed on the surface of the ceramic transition layer as a corrosion-resistant functional layer.

[0063] Specifically, spin coating is a coating technology that uses centrifugal force to uniformly spread liquid materials into a thin film by rotating the substrate at high speed. The principle involves applying a small amount of liquid to the center of the substrate, and then, through rapid rotation of the substrate, causing the liquid to diffuse towards the edges under centrifugal force, ultimately forming a film of uniform thickness. This process can be performed using a desktop spin coater, adjusting parameters such as rotation speed and time; or it can utilize customized cavity spin coaters to accommodate substrates of specific shapes and sizes.

[0064] The rare earth sol is coated onto the ceramic transition layer surface in two stages. The first stage is performed at a preset first rotation speed, and the second stage at a preset second rotation speed. This means that by setting different rotation speeds and durations during a single coating process, precise control over the coating thickness and uniformity can be achieved. The first stage typically uses a lower rotation speed to ensure the sol spreads fully on the substrate surface and eliminates any inhomogeneities that may be caused by the initial droplet addition. The second stage uses a higher rotation speed to precisely control the film thickness and promote solvent evaporation, forming a dense and uniform film. For example, the first stage can be set to a lower rotation speed (e.g., several hundred rpm) for a shorter duration to ensure initial wetting and spreading of the sol; the second stage can be set to a higher rotation speed (e.g., several thousand rpm) for a longer duration to achieve precise control of the film thickness and sufficient solvent evaporation. Alternatively, the first stage can focus on the uniform spreading of the sol, while the second stage focuses on removing excess sol and forming the desired film structure.

[0065] UV curing of coated rare-earth sol involves using specific wavelengths of UV light to induce polymerization and cross-linking reactions in the photosensitive material, rapidly transforming the liquid sol into a solid film. This method is characterized by low temperature, speed, and high efficiency, avoiding damage to the substrate material from high temperatures and effectively promoting coating densification. Irradiation can be performed using broad-spectrum or narrow-spectrum UV light sources such as mercury lamps or LED UV light sources; alternatively, excimer UV light sources can be used, utilizing their high-energy photons to trigger specific chemical reactions.

[0066] Repeated spin-coating and UV curing processes, through multiple cycles, construct a Y₂O₃-CeO₂ composite layer as a corrosion-resistant functional layer on the ceramic transition layer surface. This layer-by-layer coating construction is a key method to achieve the desired coating thickness, density, and performance. Multiple thin-layer stacking effectively avoids defects such as cracking and unevenness that may result from a single thick coating, while ensuring that each layer is fully cured, thus gradually building a composite functional layer with excellent performance. The Y₂O₃-CeO₂ composite layer, as a corrosion-resistant functional layer, utilizes the excellent corrosion resistance and stability of yttrium and cerium oxides in a plasma environment. The number of cycles can be set according to the target coating thickness and performance requirements, for example, 2-10 cycles; alternatively, the number of cycles can be dynamically adjusted by real-time monitoring of coating thickness or performance until the preset standard is achieved.

[0067] This application's solution effectively solves the problems of uneven coating and insufficient single-coat application by using a staged spin coating and repeated curing cycles. First, after micro-arc oxidation treatment of the aluminum substrate cavity to form a ceramic transition layer on its surface, and preparing a rare earth sol containing a chelating agent, a spin coating process is used to coat the rare earth sol in two stages. The first stage is coated at a preset first rotation speed, which helps the sol to initially spread evenly on the ceramic transition layer surface, effectively avoiding edge accumulation and shading caused by hydrodynamic effects. The second stage is coated at a preset second rotation speed, further optimizing the sol distribution and thickness control, ensuring complete coverage of the nanoscale film on the complex cavity structure. Next, the coated rare earth sol is cured with ultraviolet light, utilizing ultraviolet light energy to promote the chemical bonding and condensation reaction of the sol, forming a dense structure without the need for high-temperature treatment, thus preventing substrate damage. Then, the spin coating process and UV curing treatment are repeated multiple times to gradually build a Y2O3-CeO2 composite layer. This not only enhances the overall thickness and uniformity of the coating but also improves the density and bonding strength of the functional layer, ultimately forming a stable and reliable corrosion-resistant functional layer. This approach, combined with the ceramic transition layer formed by micro-arc oxidation and precisely formulated rare-earth sol, provides an effective way to prepare high-performance, highly uniform, and highly dense corrosion-resistant coatings on the surface of aluminum substrate cavities.

[0068] In one specific implementation, a dedicated spin coating device can be used. The cavity with the ceramic transition layer is fixed on a rotatable fixture, and the coaxiality deviation of the fixture is adjusted to be less than 0.05 mm. A spin-coating curve is set; for example, in the first stage, coating is performed at a preset first spin speed of 500 rpm for a preset working time of 10 seconds; in the second stage, coating is performed at a preset second spin speed of 3000 rpm for a preset working time of 30 seconds. The prepared rare earth sol is pipetted and evenly dripped onto the surface of the transition layer on the inner wall of the cavity from the top of the cavity. The spin coating device is then started and runs according to the set spin-coating curve. After spin coating, the cavity is immediately transferred to a UV curing device, and the ceramic transition layer coated with rare earth sol is irradiated with excimer ultraviolet light at a wavelength of 172 nm. For example, the UV flux density is set to 58 mW / cm², and the curing time is 9 minutes. The above spin coating and UV curing cycle is repeated, for example, 9 times, to construct a Y₂O₃-CeO₂ composite layer as a corrosion-resistant functional layer on the surface of the ceramic transition layer.

[0069] Through the above technical solutions, this application effectively solves the problems of uneven coating, weak local protection, and difficulty in forming a sufficiently thick and dense coating in a single coating in complex cavities using traditional coating methods. The staged spin coating process ensures the initial uniform spreading of rare earth sol on the ceramic transition layer surface and precise control of subsequent film thickness, significantly reducing the occurrence of "masking effect" and "edge accumulation" phenomena. Ultraviolet curing treatment achieves rapid densification of the coating at low temperature, avoiding damage to the aluminum substrate cavity caused by high temperature, while promoting the decomposition of organic components and the formation of inorganic oxide networks. Repeated spin coating and ultraviolet curing cycles enable the Y2O3-CeO2 composite layer to be built layer by layer, thereby obtaining sufficient thickness and higher density and bonding strength, significantly improving the durability and anti-stripping performance of the corrosion-resistant functional layer in plasma environment. By combining the ceramic transition layer formed by micro-arc oxidation with precisely formulated rare earth sol, this application provides an effective way to prepare a high-performance, highly uniform, and highly dense corrosion-resistant coating on the surface of an aluminum substrate cavity, thereby extending the service life of the cavity and ensuring its stable operation under harsh working conditions.

[0070] In some implementations, the first speed is 500rpm-800rpm, the first stage operating time is 10s-20s, the second stage is 3000rpm-5000rpm, and the second speed operating time is 30s-60s.

[0071] The first rotational speed refers to the speed at which the aluminum substrate cavity rotates during the first stage of the spin coating process. This speed controls the initial spreading and wetting effect of the rare earth sol on the surface of the ceramic transition layer. The first rotational speed can be set in a low range, such as between 500 rpm and 800 rpm, depending on factors such as the viscosity of the sol, surface tension, and the required coating thickness, to ensure smooth spreading of the sol and avoid splashing or localized accumulation. Alternatively, an initial rotational speed that allows the sol to uniformly cover all surface features can be selected based on the complexity of the cavity geometry. The working time of the first stage refers to the duration of the spin coating operation at the first rotational speed. This time ensures that the rare earth sol has sufficient time to fully wet the surface of the ceramic transition layer and penetrate its microstructure. The working time can be set in a range of, for example, 10 to 20 seconds, depending on the porosity of the ceramic transition layer, the permeability of the sol, and the required degree of wetting. Alternatively, an optimal time can be determined experimentally to ensure that the sol forms a uniform initial film layer during the low-speed stage. The second rotational speed refers to the speed at which the aluminum substrate cavity rotates during the second stage of the spin coating process. This rotational speed is used to remove excess rare-earth sol and force the sol to flow uniformly on the surface, thereby controlling the coating thickness and uniformity. The second rotational speed can be set in a higher range, such as between 3000 rpm and 5000 rpm, depending on the target coating thickness, the rheological properties of the sol, and the cavity size, to effectively remove excess sol and promote film densification. Alternatively, the rotational speed can be adjusted to meet the coating requirements of sols with different viscosities or solid contents. The working time of the second stage refers to the duration of the spin-coating operation at the second rotational speed. This time is used to maintain the high-speed state to promote the densification and stabilization of the sol film and prevent uneven coating thickness or defects due to insufficient time. The working time can be set in a range of, for example, 30 seconds to 60 seconds, depending on the sol drying rate, solvent evaporation characteristics, and the required film stability. Alternatively, the high-speed stage time can be extended to further optimize the smoothness and uniformity of the film.

[0072] This application addresses issues such as poor coating uniformity, inadequate thickness control, and edge accumulation on complex cavity surfaces by precisely controlling the spin-coating process of rare earth sols. In the aforementioned corrosion-resistant coating preparation method, the aluminum substrate cavity is first subjected to micro-arc oxidation treatment to form a ceramic transition layer on its surface, providing a foundation for the adhesion of subsequent functional layers. Subsequently, a rare earth sol containing a chelating agent is prepared, which will serve as the material for the corrosion-resistant functional layer. In the step of coating the rare earth sol onto the surface of the ceramic transition layer and performing ultraviolet curing to form the corrosion-resistant functional layer, this application employs a two-stage spin-coating process. In the first stage, by setting a lower initial spin speed and corresponding working time, the rare earth sol can be smoothly spread on the surface of the ceramic transition layer, fully wetting and penetrating into the microstructure, laying a uniform foundation for subsequent film formation and effectively avoiding sol splashing or localized accumulation caused by excessively high initial spin speeds. Subsequently, in the second stage, by setting a higher second rotation speed and corresponding working time, centrifugal force is used to remove excess sol and force the sol to flow uniformly on the surface, thereby precisely controlling the film thickness and significantly reducing the "masking effect" and "edge accumulation" phenomena caused by hydrodynamic effects. This two-stage coordinated control of rotation speed and time ensures that the rare earth sol can achieve uniform coverage of nanoscale films even in complex cavity areas with unevenness and gaps. By repeatedly executing this optimized spin coating process and UV curing treatment, a dense, uniform, and stable Y2O3-CeO2 composite corrosion-resistant functional layer is finally constructed on the surface of the ceramic transition layer. This precise control of spin coating parameters enables the acquisition of a high-density coating without relying on high-temperature sintering, thereby avoiding thermal damage to the aluminum substrate cavity and ensuring the coating's resistance to plasma corrosion.

[0073] Through the above technical solution, this application effectively solves the problems of poor coating uniformity, poor thickness control, and edge accumulation in the spin coating process on complex cavity surfaces in the prior art. Precisely defining the first rotation speed, the first stage working time, the second rotation speed, and the second stage working time optimizes the spreading, wetting, and leveling process of the rare earth sol on the ceramic transition layer surface. The lower first rotation speed ensures stable initial spreading and sufficient wetting of the sol, avoiding sol splashing and local accumulation; while the higher second rotation speed effectively removes excess sol and forces uniform film leveling, significantly reducing the "masking effect" and "edge accumulation" phenomena. This staged rotation speed and time synergy enables uniform coverage and precise thickness control of nanoscale films even in complex areas such as unevenness and gaps inside the aluminum substrate cavity. Therefore, the final corrosion-resistant functional layer exhibits excellent uniformity, density, and stability, significantly improving the coating's resistance to peeling and corrosion under continuous plasma impact and thermal cycling conditions, thereby extending the service life of the RPS cavity and reducing the risk of particulate contamination.

[0074] In some embodiments, the step of UV curing the coated rare earth sol includes: A ceramic transition layer coated with rare earth sol was irradiated with excimer ultraviolet light with a wavelength of 172 nm. The photon energy of the excimer ultraviolet light was used to break the organic chemical bonds in the rare earth sol and to generate ozone and oxygen free radicals, thereby promoting the condensation reaction of the rare earth sol.

[0075] Irradiation with 172nm excimer ultraviolet light provides high-energy photons that can directly break the organic chemical bonds in rare earth sols, effectively removing organic residues and preventing a porous coating structure. Simultaneously, it excites the generation of ozone and oxygen free radicals. These active oxygen species promote the condensation reaction of the rare earth sol, accelerating the cross-linking and densification process of the coating. This results in the formation of a stable corrosion-resistant functional layer without the need for high temperatures, ensuring the aluminum substrate is protected from thermal deformation. This ultraviolet curing method, applied to rare earth sols already coated on the surface of a ceramic transition layer via spin coating, ensures that when constructing a Y2O3-CeO2 composite layer as a corrosion-resistant functional layer on the aluminum substrate cavity surface, the functional layer achieves sufficient densification and organic removal at low temperatures, while avoiding thermal damage to the aluminum substrate and ceramic transition layer. This overall improves the performance and reliability of the corrosion-resistant coating.

[0076] Through the above technical solution, this application can avoid the softening deformation and mechanical property degradation of the aluminum substrate caused by traditional high-temperature sintering methods, while effectively removing organic residues in rare earth sols, thus solving the problems of insufficient coating density and poor durability. This low-temperature curing technology ensures that the corrosion-resistant functional layer forms a dense, pure, and strongly bonded structure on the aluminum substrate, significantly improving the coating's corrosion resistance and service life in plasma environments.

[0077] In some implementations, the step S1 is preceded by: S0. The aluminum substrate cavity is cleaned using a three-step ultrasonic cleaning process, which includes sequentially using acetone, anhydrous ethanol and deionized water as cleaning media to remove organic matter, residual impurities and ionic contaminants from the surface of the aluminum substrate cavity.

[0078] This application addresses the negative impact of surface contaminants on the aluminum substrate cavity on subsequent coating preparation by introducing a pre-cleaning step S0 before the micro-arc oxidation treatment (S1). Specifically, this three-step ultrasonic cleaning process uses acetone, anhydrous ethanol, and deionized water sequentially as cleaning media to achieve targeted removal of various contaminants on the aluminum substrate cavity surface. First, acetone effectively removes organic matter from the aluminum substrate cavity surface, preventing it from carbonizing or forming an obstructive layer during subsequent micro-arc oxidation, thus ensuring uniform and dense growth of the ceramic transition layer. Second, anhydrous ethanol removes residual acetone and minute physical impurities, further purifying the aluminum substrate cavity surface and providing a clean substrate for subsequent micro-arc oxidation. Finally, deionized water thoroughly removes ionic contaminants, preventing ions from participating in reactions or depositing during micro-arc oxidation, which could lead to defects or decreased adhesion in the ceramic transition layer. This step-by-step, targeted cleaning strategy, combined with the mechanical action of ultrasound, can efficiently and thoroughly clean the surface of the aluminum substrate cavity, providing ideal starting conditions for the subsequent micro-arc oxidation treatment (S1), thereby significantly improving the quality of the ceramic transition layer and its adhesion to the aluminum substrate cavity, and thus optimizing the performance of the entire corrosion-resistant coating.

[0079] As a specific implementation method, before performing micro-arc oxidation treatment (S1) on the aluminum substrate cavity, the following steps can be followed for cleaning: First, completely immerse the Φ200mm×400mm aluminum substrate cavity in a container containing acetone (e.g., 25ml) and clean it using ultrasound (100W power, 40kHz frequency) for 5 minutes to efficiently remove organic contaminants such as grease and resin from the surface of the aluminum substrate cavity. Then, after draining the cleaned aluminum substrate cavity, transfer it to a container containing anhydrous ethanol (e.g., 25ml) and perform ultrasonic cleaning again for 3 minutes to further remove residual acetone and small particulate impurities. Finally, place the drained aluminum substrate cavity in a container containing deionized water (e.g., 50ml) and perform ultrasonic cleaning for 5 minutes, repeating this water washing step (a total of two water washes) to thoroughly remove ethanol residue and ionic contaminants. After cleaning, the aluminum substrate cavity is placed in a forced-air drying oven (70℃) for 40 minutes to ensure that there is no moisture residue on its surface, in preparation for the subsequent micro-arc oxidation treatment (S1).

[0080] The above technical solution effectively removes organic matter, residual impurities, and ionic contaminants from the surface of the aluminum substrate cavity, providing a clean substrate for subsequent micro-arc oxidation treatment (S1). This significantly improves the adhesion between the ceramic transition layer and the aluminum substrate cavity, avoids coating defects caused by contaminants, and thus ensures the uniformity and density of the corrosion-resistant coating, ultimately improving the coating's corrosion resistance and service life under complex working conditions.

[0081] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0082] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a corrosion-resistant coating, characterized in that, Including the following steps: S1. Micro-arc oxidation treatment is performed on the aluminum substrate cavity to form a ceramic transition layer on the surface of the aluminum substrate cavity; S2. Prepare rare earth sols containing chelating agents; S3. Apply rare earth sol to the surface of the ceramic transition layer and perform ultraviolet curing treatment to form a corrosion-resistant functional layer.

2. The method for preparing a corrosion-resistant coating according to claim 1, characterized in that, Step S1 includes: The aluminum-based cavity is placed in a silicate-based electrolyte; A bipolar pulse power supply is used to apply voltage to the aluminum substrate cavity, where bipolar means that the polarities of the two electrodes are opposite; By using micro-arc oxidation technology and controlling the micro-arc oxidation process parameters, a ceramic transition layer with a thickness ranging from 50±5 micrometers and a Vickers hardness ranging from 1200HV to 1500HV is grown in situ on the surface of an aluminum substrate cavity. The micro-arc oxidation process parameters include current density, frequency, duty cycle and processing time.

3. The method for preparing a corrosion-resistant coating according to claim 1, characterized in that, Chelating agents include acetylacetone, and rare earth sols contain yttrium and cerium. The steps for preparing rare earth sols containing chelating agents include: A rare earth sol containing yttrium and cerium was prepared using acetylacetone. By controlling the amount of acetylacetone added (ranging from 0.05 ml to 0.30 ml), the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer was controlled within the range of 20% to 90%.

4. The method for preparing a corrosion-resistant coating according to claim 3, characterized in that, The steps for preparing a rare earth sol containing yttrium and cerium using acetylacetone, and controlling the amount of acetylacetone added (ranging from 0.05 ml to 0.30 ml) to ensure that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer is controlled within the range of 20% to 90%, include: Yttrium source, cerium source and acetylacetone are mixed in a beaker containing solvent. The amount of acetylacetone added is controlled to be in the range of 0.05ml-0.30ml. The beaker is then placed in a water bath at a preset temperature and stirred to obtain a mixed solution. Add deionized water to the mixed solution in steps while continuing to stir; Adjust the pH of the mixed solution to 3-4 using dilute nitric acid; The mixed solution after pH adjustment was aged to prepare a rare earth sol with a controllable proportion of tetravalent cerium ions, so that the proportion of tetravalent cerium ions in the final corrosion-resistant functional layer was controlled within the range of 20% to 90%.

5. The method for preparing a corrosion-resistant coating according to claim 4, characterized in that, The solvent was anhydrous ethanol, the yttrium source was Y(NO3)3·6H2O, and the cerium source was Ce(NO3)3·6H2O.

6. The method for preparing a corrosion-resistant coating according to claim 4, characterized in that, After the step of preparing a rare earth sol with a controllable proportion of tetravalent cerium ions, a filtration process is also included: The prepared rare earth sol was filtered using a polytetrafluoroethylene (PTFE) filter membrane.

7. The method for preparing a corrosion-resistant coating according to claim 1, characterized in that, Step S3 includes: using a spin coating process, coating rare earth sol onto the surface of the ceramic transition layer in two stages, with the first stage coating at a preset first rotation speed and the second stage coating at a preset second rotation speed; The coated rare earth sol was then subjected to ultraviolet light curing treatment. By repeatedly performing spin coating and UV curing processes, a Y2O3-CeO2 composite layer is constructed on the surface of the ceramic transition layer as a corrosion-resistant functional layer.

8. The method for preparing a corrosion-resistant coating according to claim 7, characterized in that, The first speed is 500rpm-800rpm, and the working time of the first stage is 10s-20s. The second stage is 3000rpm-5000rpm, and the working time of the second speed is 30s-60s.

9. The method for preparing a corrosion-resistant coating according to claim 7, characterized in that, The steps for UV curing the coated rare earth sol include: A ceramic transition layer coated with rare earth sol was irradiated with excimer ultraviolet light with a wavelength of 172 nm. The photon energy of the excimer ultraviolet light was used to break the organic chemical bonds in the rare earth sol and to generate ozone and oxygen free radicals, thereby promoting the condensation reaction of the rare earth sol.

10. The method for preparing a corrosion-resistant coating according to claim 1, characterized in that, Before step S1, the following steps are also included: S0. The aluminum substrate cavity is cleaned using a three-step ultrasonic cleaning process, which includes sequentially using acetone, anhydrous ethanol and deionized water as cleaning media to remove organic matter, residual impurities and ionic contaminants from the surface of the aluminum substrate cavity.

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