A method for preparing a diamond high-temperature oxidation-resistant silicon-based coating
By employing a multilayer coating preparation method consisting of dispersion, composite sol, and protective sol, the problems of oxidation, cracking, and weak interfacial adhesion of traditional diamond high-temperature antioxidant silicon-based coatings under high-temperature environments were solved, thereby improving the stability and toughness of the coating at high temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HENAN WANMO DIAMOND CO LTD
- Filing Date
- 2026-02-02
- Publication Date
- 2026-06-09
AI Technical Summary
Traditional diamond high-temperature anti-oxidation silicon-based coatings are prone to oxidation in high-temperature environments, and the difference in thermal expansion coefficients leads to cracking. They also have high porosity and weak interfacial bonding, resulting in unstable performance.
A multilayer coating preparation method using dispersion, composite sol and protective sol is adopted. Through plasma activation, gradient densification and high pressure atmosphere treatment, a continuous and stable three-dimensional network structure is formed, which enhances the interfacial bonding and antioxidant properties.
It significantly improves the high-temperature oxidation resistance of the coating, reduces the oxidation weight loss rate, enhances the toughness and interfacial bonding stability of the coating, and avoids cracking and peeling.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of coating preparation technology, and in particular to a method for preparing a diamond high-temperature antioxidant silicon-based coating. Background Technology
[0002] A coating is an extremely thin layer of material that is firmly adhered to the surface of an object (substrate) through physical, chemical, or composite processes. Its thickness is typically between micrometers and millimeters.
[0003] Traditional diamond high-temperature antioxidant silicon-based coatings are prone to oxidation reactions at high temperatures, leading to rapid performance degradation and failure. The significant difference in thermal expansion coefficients between the coating and the diamond substrate makes them highly susceptible to thermal stress during temperature changes, resulting in cracking and peeling. Furthermore, the high porosity and insufficient density of the coating contribute to weak high-temperature resistance to volatilization and unstable protective effects. Moreover, the single-coating system lacks toughness, making it prone to microcracks that quickly propagate under external forces. Additionally, the weak interfacial bonding between coating layers makes delamination failure a common problem. Therefore, this invention provides a method for preparing a diamond high-temperature antioxidant silicon-based coating. Summary of the Invention
[0004] The main objective of this invention is to provide a diamond high-temperature antioxidant silicon-based coating with high scratch critical load and low oxidation weight loss rate, which is applied in a method for preparing a diamond high-temperature antioxidant silicon-based coating.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] This invention provides a method for preparing a diamond high-temperature antioxidant silicon-based coating, the diamond high-temperature antioxidant silicon-based coating comprising the following preparation steps:
[0007] S1. Immerse diamond powder in acetone, set power 300W, ultrasonically clean for 15 minutes, filter out the supernatant, add anhydrous ethanol, set power 300W, ultrasonically clean for 15 minutes, filter, put the diamond powder into a drying oven to dry, set temperature 100℃, dry for 2 hours, spread the dried diamond powder evenly on a quartz boat, use a plasma treatment instrument, introduce mixed gas, set power 80W, gas pressure 15Pa, treat for 20 minutes to obtain activated diamond powder;
[0008] S2. Immerse the activated diamond powder in the dispersion for 5 minutes, pull it up at a rate of 0.3 mm / min, and dry it at 120°C for 1 hour to obtain the first layer of activated diamond powder;
[0009] S3. Immerse the first layer of activated diamond powder in the composite sol for 5 minutes, pull it up at a rate of 0.5 mm / min, and let it stand at 25°C for 12 hours. Repeat the immersion, pulling and standing process 2–3 times to obtain the middle layer of activated diamond powder.
[0010] S4. Immerse the middle layer activated diamond powder in the protective sol for 3 minutes, pull it up at a rate of 0.2 mm / min, and let it stand at 25°C for 8 hours to obtain the treated activated diamond powder.
[0011] S5. Place the treated activated diamond powder into a vacuum muffle furnace for drying. Pour nitrogen gas into the furnace and heat it to 80°C at a heating rate of ≤1°C / min. Hold for 2 hours. Then heat to 120°C and hold for 2 hours. Then heat to 200°C and hold for 2 hours. Then heat to 300°C and hold for 2 hours. Then heat to 600°C and hold for 4 hours. Stop heating and allow the furnace temperature to cool naturally to 25°C to obtain the dried powder.
[0012] S6. Place the dried powder in a high-pressure atmosphere furnace for treatment, introduce argon gas, pressurize to 5MPa, heat to 600℃ at a heating rate of ≤1℃ / min, and let stand for 3 hours to obtain a diamond high-temperature antioxidant silicon-based coating.
[0013] The muffle furnace drying process employs a step-by-step, slow heating method from low to high temperatures. First, a pre-drying stage at 80–120℃ gradually removes residual solvents from the coating, preventing pinholes and cracks caused by rapid evaporation. Then, a degreasing and densification stage at 200–300℃ decomposes and removes residual organic impurities, preventing high-temperature carbonization and pore formation. Finally, a high-temperature curing stage at 600℃ promotes deep cross-linking of the coating, forming a continuous and stable three-dimensional network structure and enhancing the interfacial bonding between coating layers. The continuous introduction of high-purity nitrogen creates an inert atmosphere, effectively isolating oxygen and preventing oxidation and deterioration of diamond powder and coating components at high temperatures. The heating and cooling rates of ≤1℃ / min match the differences in thermal expansion coefficients of the gradient coating layers, alleviating interfacial thermal stress and fundamentally preventing coating cracking and peeling.
[0014] By using a high-pressure atmosphere furnace and leveraging the physical compaction effect of 5MPa high-purity argon gas, combined with a constant temperature environment of 600℃, the process further compresses and eliminates the extremely fine pores and lattice defects remaining after plasma-assisted densification. At the same time, the high-purity argon atmosphere effectively isolates oxygen, preventing the diamond powder and coating components from oxidizing or graphitizing under high temperature and pressure. The 600℃ temperature is consistent with the initial curing temperature, preventing secondary heating from generating new thermal stress. Ultimately, the coating density is increased to over 99.5%, significantly enhancing the coating's high-temperature resistance to volatilization, impermeability, and interfacial bonding stability.
[0015] The purity of nitrogen gas is ≥99.99%.
[0016] The argon gas purity is ≥99.99%.
[0017] Furthermore, the mass-to-volume ratio of the diamond powder, acetone, anhydrous ethanol, dispersion, composite sol, and protective sol is 100g:190-210mL:190-210mL:45-55mL:178-218mL:45-55mL.
[0018] Acetone can quickly dissolve and remove impurities such as oil and dust from the surface of diamond powder, significantly improving the cleanliness of the powder surface. This creates favorable conditions for subsequent plasma activation to introduce hydroxyl groups and enhance the adhesion between the coating and the substrate. At the same time, acetone is highly volatile and can be completely removed by low-temperature drying after cleaning, leaving no residual impurities that contaminate the powder or interfere with the preparation of subsequent coatings. Furthermore, it is chemically stable and does not cause any damage to the diamond substrate, making it highly safe.
[0019] The particle size of diamond powder is 1-5 μm.
[0020] Furthermore, the mixed gas is a mixture of argon and oxygen;
[0021] The volume ratio of argon to oxygen is 3:1.
[0022] Both argon and oxygen have a purity of ≥99.99%.
[0023] Furthermore, the preparation of the dispersion includes the following steps: adding anhydrous ethanol into silicon carbide nanocrystals and ultrasonically dispersing to obtain a dispersion;
[0024] The mass-to-volume ratio of the silicon carbide nanocrystals to anhydrous ethanol is 1 g: 50 mL.
[0025] Furthermore, the preparation of the composite sol includes the following steps:
[0026] A1. Add concentrated nitric acid to the multi-walled carbon nanotubes and reflux at 60°C for 3 hours with stirring speed of 200-300 rpm. Filter the filtrate using a 0.22 μm polytetrafluoroethylene filter membrane, collect the particles, wash the particles 3-4 times with deionized water, and dry the washed particles in a vacuum drying oven at 80°C and a vacuum degree of 0.08-0.1 MPa for 4 hours to obtain activated multi-walled carbon nanotubes.
[0027] A2. Activated multi-walled carbon nanotubes were dispersed in anhydrous ethanol. The power was set to 400W, and the temperature was controlled at <40℃ in an ice-water bath for 30 minutes. 3-(methacryloyloxy)propyltrimethoxysilane was added, and the mixture was stirred at a constant temperature of 70℃ at a speed of 200-300 rpm for 4 hours to obtain a mixture. The mixture was centrifuged at a speed of 8000 rpm for 10 minutes. The supernatant was filtered off, and the precipitate was retained. The precipitate was washed three times with anhydrous ethanol. The washed precipitate was dried in a vacuum drying oven at a temperature of 60℃ and a vacuum degree of 0.08-0.1 MPa for 2 hours to obtain modified multi-walled carbon nanotubes.
[0028] A3. Mix anhydrous ethanol and tetraethyl orthosilicate and stir magnetically at 200-250 rpm for 10 minutes. Add the acid water mixture and stir at 250-300 rpm and 35°C for 2 hours to obtain solution A.
[0029] A4. Modified multi-walled carbon nanotubes were dispersed in anhydrous ethanol at a power of 400W, with the temperature controlled in an ice-water bath below 40℃, for 20 minutes to obtain solution B. Solution B was then added to solution A and stirred at a speed of 250-350 rpm and a temperature of 40℃ for 3 hours. Butyl titanate was added and stirred at a speed of 200-250 rpm and a temperature of 50℃ for 4 hours. Tantalum pentoxide nanocrystals, hafnium dioxide nanocrystals, and yttrium oxide nanocrystals were added sequentially and ultrasonically dispersed at a power of 400W, with the temperature controlled in an ice-water bath below 40℃, for 30 minutes. Silicon carbide nanocrystals were added and ultrasonically dispersed at a power of 400W, with the temperature controlled in an ice-water bath below 40℃, for 20 minutes. 3-(methacryloyloxy)propyltrimethoxysilane was added and stirred at a speed of 200-250 rpm for 1 hour, with the viscosity controlled at [value missing]. A composite sol was obtained.
[0030] The multi-walled carbon nanotubes have a particle size of 5-10 nm, a length of 1-5 μm, and a purity of 95%.
[0031] Furthermore, the mass-to-volume ratio of concentrated nitric acid and multi-walled carbon nanotubes in A1 is 50 mL: 0.5 g;
[0032] The activated multi-walled carbon nanotubes in A2 are dispersed in anhydrous ethanol, and the mass-to-volume ratio of the activated multi-walled carbon nanotubes to the anhydrous ethanol is 0.5g:50mL.
[0033] The mass-to-volume ratio of the activated multi-walled carbon nanotubes and 3-(methacryloyloxy)propyltrimethoxysilane is 0.5 g: 1 mL.
[0034] Furthermore, the volume ratio of anhydrous ethanol to tetraethyl orthosilicate in A3 is 1:5;
[0035] The pH of the acid-water mixture is adjusted to 3.6.
[0036] The mass-to-volume ratio of modified multi-walled carbon nanotubes and anhydrous ethanol in A4 is 0.5 g: 50 mL.
[0037] The mass-to-volume ratio of solution B, solution A, tetrabutyl titanate, tantalum pentoxide nanocrystals, hafnium dioxide nanocrystals, yttrium oxide nanocrystals, silicon carbide nanocrystals, and 3-(methacryloyloxy)propyltrimethoxysilane is 50 mL: 141 mL: 2 mL: 3 g: 1 g: 0.5 g: 1 g: 5 mL.
[0038] The silicon carbide nanocrystals have a particle size of 10 nm and a purity of 99%.
[0039] The hafnium dioxide nanocrystals, yttrium oxide nanocrystals, and silicon carbide nanocrystals all have a particle size of 5-10 nm and a purity of 99.99%.
[0040] The purity of tetrabutyl titanate is 98%.
[0041] 3-(methacryloyloxy)propyltrimethoxysilane is of industrial grade.
[0042] Furthermore, the acid-water mixture is composed of deionized water and dilute hydrochloric acid;
[0043] The volume ratio of the deionized water to the dilute hydrochloric acid is 20:1;
[0044] The mass concentration of the dilute hydrochloric acid is 15%.
[0045] Furthermore, the preparation of the protective sol includes the following steps: adding yttrium oxide and silicon nitride into anhydrous ethanol and ultrasonically dispersing them, setting the power to 400W, and dispersing for 30 minutes to obtain the protective sol.
[0046] Furthermore, the mass-to-volume ratio of yttrium oxide, silicon nitride, and anhydrous ethanol is 0.5 g: 1.5 g: 50 mL.
[0047] Both yttrium oxide and silicon nitride have a particle size of 10 nm and a purity of 99.99%.
[0048] The present invention has the following beneficial effects:
[0049] 1. In this invention, a dispersion liquid is used, whose core thermal expansion coefficient is between that of diamond and the outer coating. This can effectively weaken the internal stress caused by the difference in thermal expansion between different materials under high temperature conditions, thereby reducing the risk of coating cracking and peeling from the root. The preparation process of the transition layer is simple and controllable, the dispersion liquid is evenly dispersed, and the coating formed after lifting is ultra-thin and uniform in thickness. It can tightly cover the diamond surface without affecting the coating effect of the subsequent middle and outer coatings. At the same time, the interfacial bonding strength can be further enhanced through chemical bonding, providing stable structural support for the entire gradient coating system.
[0050] 2. In this invention, a protective sol is used. Its main components can effectively block oxygen penetration in high-temperature environments, inhibit the oxidation reaction between the diamond substrate and the coating, and significantly reduce the volatilization loss of coating components at high temperatures, ensuring performance stability under long-term high-temperature conditions. The protective sol is easy to prepare, has good dispersion uniformity, and the coating formed after lifting is tight and continuous with an ultra-thin thickness. It does not significantly change the flowability and particle size distribution of the diamond powder, is compatible with subsequent curing and post-processing, and takes into account both protective performance and powder application compatibility.
[0051] 3. In this invention, a composite sol is used. On the one hand, it relies on the three-dimensional interpenetrating network structure constructed by carbon nanotubes to exert toughening effects such as bridging, pull-out, and crack deflection. At the same time, it uses the nano-rivet effect of silicon carbide nanocrystals to pin up microcracks inside the coating, significantly improving the fracture toughness and impact resistance of the coating. On the other hand, the high-melting-point particles of tantalum pentoxide nanocrystals and hafnium dioxide nanocrystals doped inside can construct a high-temperature stable skeleton, inhibiting the melting and softening of the coating and structural collapse under extreme high-temperature environments. Moreover, this functional layer can form a strong chemical bond with the inner silicon carbide transition layer and the outer yttrium oxide-silicon nitride protective layer, strengthening the overall interface integrity of the gradient coating, avoiding delamination and cracking, and assisting the outer layer in blocking oxygen penetration, reducing the volatilization loss of coating components at high temperatures, thus comprehensively ensuring the high-temperature oxidation resistance and structural stability of the coating. Detailed Implementation
[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0053] It should be noted that all raw materials used in the following experiments are commercially available.
[0054] The preparation methods of the dispersion, composite sol, and protective sol in the following embodiments and comparative examples of the present invention are as follows:
[0055] I. Preparation of Dispersion
[0056] Add 50 mL of anhydrous ethanol to 1 g of silicon carbide nanocrystals and disperse by ultrasonication at a power of 400 W for 20 minutes to obtain a dispersion.
[0057] II. Preparation of Composite Sol
[0058] A1. Add 50 mL of concentrated nitric acid to 0.5 g of multi-walled carbon nanotubes, reflux and stir at 60 °C for 3 hours at a stirring speed of 200-300 rpm, filter the filtrate through a 0.22 μm polytetrafluoroethylene filter membrane, collect the particles, wash the particles 3-4 times with 30 mL of deionized water, and dry the washed particles in a vacuum drying oven at 80 °C and a vacuum degree of 0.08-0.1 MPa for 4 hours to obtain activated multi-walled carbon nanotubes;
[0059] A2. Activated multi-walled carbon nanotubes were dispersed in 50 mL of anhydrous ethanol. The power was set to 400 W, and the temperature was controlled at <40℃ in an ice-water bath for 30 minutes. Then, 1 mL of 3-(methacryloyloxy)propyltrimethoxysilane was added, and the mixture was stirred at 70℃ for 200-300 rpm for 4 hours to obtain a mixture. The mixture was then centrifuged at 8000 rpm for 10 minutes. The supernatant was filtered off, and the precipitate was retained. The precipitate was washed three times with 30 mL of anhydrous ethanol. The washed precipitate was then dried in a vacuum drying oven at 60℃ and a vacuum of 0.08-0.1 MPa for 2 hours to obtain modified multi-walled carbon nanotubes.
[0060] A3. Mix 100 mL of anhydrous ethanol and 20 mL of tetraethyl orthosilicate with a magnetic stirrer at 200-250 rpm for 10 minutes. Add the acid-water mixture and stir. Adjust the pH to 3.5. Set the stirring speed to 250-300 rpm and the temperature to 35℃. Stir for 2 hours to obtain solution A.
[0061] A4. Disperse the modified multi-walled carbon nanotubes in 50 mL of anhydrous ethanol. Set the power to 400 W, maintain the temperature in an ice-water bath below 40 °C, and disperse for 20 minutes to obtain solution B. Add solution B to solution A and stir. Set the stirring speed to 250-350 rpm and the temperature to 40 °C, and stir for 3 hours. Add 2 mL of tetrabutyl titanate and stir. Set the stirring speed to 200-250 rpm and the temperature to 50 °C, and stir for 4 hours. Add 3 g of tantalum pentoxide nanocrystals, 1 g of hafnium dioxide nanocrystals, and 0.5 g of yttrium oxide nanocrystals sequentially and disperse ultrasonically. Set the power to 400 W, maintain the temperature in an ice-water bath below 40 °C, and disperse for 30 minutes. Add 1 g of silicon carbide nanocrystals and disperse ultrasonically. Set the power to 400 W, maintain the temperature in an ice-water bath below 40 °C, and disperse for 20 minutes. Add 5 mL of 3-(methacryloyloxy)propyltrimethoxysilane and stir. Set the stirring speed to 200-250 rpm and stir for 1 hour, controlling the viscosity at [value missing]. A composite sol was obtained.
[0062] The acid-water mixture is made by mixing 20 mL of deionized water and 1 mL of 15% dilute hydrochloric acid.
[0063] III. Preparation of Protective Sol
[0064] 0.5g of yttrium oxide and 1.5g of silicon nitride were added to 50mL of anhydrous ethanol and ultrasonically dispersed. The power was set to 400W and the dispersion was carried out for 30 minutes to obtain a protective sol.
[0065] Example 1: A method for preparing a diamond high-temperature antioxidant silicon-based coating, wherein the diamond high-temperature antioxidant silicon-based coating includes the following preparation steps:
[0066] S1. Soak 100g of diamond powder in 190mL of acetone, set the power to 300W, and ultrasonically clean for 15 minutes. Filter out the supernatant, add 190mL of anhydrous ethanol, set the power to 300W, and ultrasonically clean for 15 minutes. Filter by suction, dry the diamond powder, spread the dried diamond powder evenly on a quartz boat, use a plasma processor, introduce mixed gas, set the power to 80W, the gas pressure to 15Pa, and process for 20 minutes to obtain activated diamond powder.
[0067] S2. Immerse the activated diamond powder in 45 mL of dispersion, let stand for 5 minutes, pull it up at a rate of 0.3 mm / min, and dry it at 120 °C for 1 hour to obtain the first layer of activated diamond powder;
[0068] S3. Immerse the first layer of activated diamond powder in 178 mL of composite sol for 5 minutes, pull it up at a rate of 0.5 mm / min, and let it stand at 25°C for 12 hours. Repeat the immersion, pulling and standing process 2–3 times to obtain the middle layer of activated diamond powder.
[0069] S4. Immerse the middle layer activated diamond powder in 45mL of protective sol for 3 minutes, pull it up at a rate of 0.2mm / min, and let it stand at 25℃ for 8 hours to obtain the treated activated diamond powder.
[0070] S5. Place the treated activated diamond powder into a vacuum muffle furnace for drying. Pour nitrogen gas into the furnace and heat it to 80°C at a heating rate of ≤1°C / min. Hold for 2 hours. Then heat to 120°C and hold for 2 hours. Then heat to 200°C and hold for 2 hours. Then heat to 300°C and hold for 2 hours. Then heat to 600°C and hold for 4 hours. Stop heating and allow the furnace temperature to cool naturally to 25°C to obtain the dried powder.
[0071] S6. Place the dried powder in a high-pressure atmosphere furnace for treatment, introduce argon gas, pressurize to 5MPa, heat to 600℃ at a heating rate of ≤1℃ / min, and let stand for 3 hours to obtain a diamond high-temperature antioxidant silicon-based coating.
[0072] The mixed gas is a mixture of argon and oxygen;
[0073] The volume ratio of argon to oxygen is 3:1.
[0074] Example 2: A method for preparing a diamond high-temperature antioxidant silicon-based coating, wherein the diamond high-temperature antioxidant silicon-based coating includes the following preparation steps:
[0075] S1. Soak 100g of diamond powder in 200mL of acetone, set the power to 300W, and ultrasonically clean for 15 minutes. Filter out the supernatant, add 200mL of anhydrous ethanol, set the power to 300W, and ultrasonically clean for 15 minutes. Filter by suction, dry the diamond powder, spread the dried diamond powder evenly on a quartz boat, use a plasma processor, introduce mixed gas, set the power to 80W, the gas pressure to 15Pa, and process for 20 minutes to obtain activated diamond powder.
[0076] S2. Immerse the activated diamond powder in 50 mL of dispersion, let stand for 5 minutes, pull it up at a rate of 0.3 mm / min, and dry it at 120 °C for 1 hour to obtain the first layer of activated diamond powder;
[0077] S3. Immerse the first layer of activated diamond powder in 198 mL of composite sol for 5 minutes, pull it up at a rate of 0.5 mm / min, and let it stand at 25°C for 12 hours. Repeat the immersion, pulling and standing process 2–3 times to obtain the middle layer of activated diamond powder.
[0078] S4. Immerse the middle layer activated diamond powder in 50mL of protective sol for 3 minutes, pull it up at a rate of 0.2mm / min, and let it stand at 25℃ for 8 hours to obtain the treated activated diamond powder.
[0079] S5. Place the treated activated diamond powder into a vacuum muffle furnace for drying. Pour nitrogen gas into the furnace and heat it to 80°C at a heating rate of ≤1°C / min. Hold for 2 hours. Then heat to 120°C and hold for 2 hours. Then heat to 200°C and hold for 2 hours. Then heat to 300°C and hold for 2 hours. Then heat to 600°C and hold for 4 hours. Stop heating and allow the furnace temperature to cool naturally to 25°C to obtain the dried powder.
[0080] S6. Place the dried powder in a high-pressure atmosphere furnace for treatment, introduce argon gas, pressurize to 5MPa, heat to 600℃ at a heating rate of ≤1℃ / min, and let stand for 3 hours to obtain a diamond high-temperature antioxidant silicon-based coating.
[0081] The mixed gas is a mixture of argon and oxygen;
[0082] The volume ratio of argon to oxygen is 3:1.
[0083] Example 3: A method for preparing a diamond high-temperature antioxidant silicon-based coating, wherein the diamond high-temperature antioxidant silicon-based coating includes the following preparation steps:
[0084] S1. Soak 100g of diamond powder in 210mL of acetone, set the power to 300W, and ultrasonically clean for 15 minutes. Filter out the supernatant, add 210mL of anhydrous ethanol, set the power to 300W, and ultrasonically clean for 15 minutes. Filter by suction, dry the diamond powder, spread the dried diamond powder evenly on a quartz boat, use a plasma processor, introduce mixed gas, set the power to 80W, the gas pressure to 15Pa, and process for 20 minutes to obtain activated diamond powder.
[0085] S2. Immerse the activated diamond powder in 55 mL of dispersion, let stand for 5 minutes, pull it up at a rate of 0.3 mm / min, and dry it at 120 °C for 1 hour to obtain the first layer of activated diamond powder;
[0086] S3. Immerse the first layer of activated diamond powder in 218 mL of composite sol for 5 minutes, pull it up at a rate of 0.5 mm / min, and let it stand at 25°C for 12 hours. Repeat the immersion, pulling and standing process 2–3 times to obtain the middle layer of activated diamond powder.
[0087] S4. Immerse the middle layer activated diamond powder in 55 mL of protective sol for 3 minutes, pull it up at a rate of 0.2 mm / min, and let it stand at 25°C for 8 hours to obtain the treated activated diamond powder.
[0088] S5. Place the treated activated diamond powder into a vacuum muffle furnace for drying. Pour nitrogen gas into the furnace and heat it to 80°C at a heating rate of ≤1°C / min. Hold for 2 hours. Then heat to 120°C and hold for 2 hours. Then heat to 200°C and hold for 2 hours. Then heat to 300°C and hold for 2 hours. Then heat to 600°C and hold for 4 hours. Stop heating and allow the furnace temperature to cool naturally to 25°C to obtain the dried powder.
[0089] S6. Place the dried powder in a high-pressure atmosphere furnace for treatment, introduce argon gas, pressurize to 5MPa, heat to 600℃ at a heating rate of ≤1℃ / min, and let stand for 3 hours to obtain a diamond high-temperature antioxidant silicon-based coating.
[0090] The mixed gas is a mixture of argon and oxygen;
[0091] The volume ratio of argon to oxygen is 3:1.
[0092] Comparative Example 1: The difference between this comparative example and Example 1 is that:
[0093] No immersion in the dispersion was used in this comparative example.
[0094] Comparative Example 2: The difference between this comparative example and Example 1 is that:
[0095] Composite sol soaking was not used in this comparative example.
[0096] Comparative Example 3 differs from Example 1 in that:
[0097] No protective sol immersion was used in this comparative example.
[0098] Performance testing: The diamond high-temperature antioxidant silicon-based coatings prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 were tested.
[0099] Performance testing: The relevant properties of the diamond high-temperature antioxidant silicon-based coating preparation method samples provided in Examples 1-3 and Comparative Examples 1-3 were tested respectively, and the test data are recorded in Table 1 below:
[0100]
[0101] Based on the above data, the following conclusions can be drawn:
[0102] (1) The critical scratch load of Examples 1-3 is far superior to that of Comparative Examples 1-3. The key point is that the examples are immersed in the dispersion liquid, and their coefficient of thermal expansion is between that of the diamond substrate and the outer composite coating. This can effectively offset the difference in thermal expansion between different layers during high-temperature curing and scratch testing, and avoid microcracks caused by stress concentration at the interface.
[0103] (2) The fracture toughness of Examples 1-3 is far superior to that of Comparative Examples 1-3. The key point is that, through immersion in the composite sol, the multi-walled carbon nanotubes inside the examples can construct a continuous three-dimensional interpenetrating network. When the coating is subjected to external force and microcracks are generated, the multi-walled carbon nanotubes can play the role of bridging, pull-out and crack deflection, consume a large amount of energy required for crack propagation, and delay the further extension of cracks.
[0104] (3) The oxidation weight loss rate of Examples 1-3 at 1700℃ / 100h is far superior to that of Comparative Examples 1-3. The key point is that the Examples have excellent high-temperature chemical stability by immersing in the protective sol. It is not easy to decompose or oxidize at 1700℃, and can form a dense physical barrier, effectively preventing external oxygen from penetrating into the coating and the diamond substrate, and inhibiting the oxidation reaction of diamond.
[0105] Through the above demonstration, the present invention is significantly superior to the control group in terms of critical scratch load, fracture toughness and oxidation weight loss rate at 1700℃ / 100h, thus verifying the advanced nature and rationality of the preparation process.
[0106] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0107] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. A method for preparing a diamond high-temperature antioxidant silicon-based coating, characterized in that, The diamond high-temperature antioxidant silicon-based coating includes the following preparation steps: S1. Soak diamond powder in acetone and ultrasonically disperse it. Filter out the supernatant, add anhydrous ethanol and ultrasonically disperse it. Filter it and dry the diamond powder. Spread the dried diamond powder on a quartz boat and treat it with a plasma treatment instrument to obtain activated diamond powder. S2. Immerse the activated diamond powder in the dispersion, impregnate, pull, and dry to obtain the first layer of activated diamond powder; S3. Immerse the first layer of activated diamond powder in the composite sol, soak, lift, stand, repeat soaking, lifting and drying to obtain the middle layer of activated diamond powder. S4. Immerse the middle layer activated diamond powder in a protective sol, impregnate, lift, and let stand to obtain the treated activated diamond powder. S5. The treated activated diamond powder is placed in a vacuum muffle furnace for drying, and nitrogen gas is introduced to obtain dried powder; S6. The dried powder is placed in a high-pressure atmosphere furnace for treatment, and argon gas is introduced to obtain a diamond high-temperature antioxidant silicon-based coating.
2. The diamond high-temperature antioxidant silicon-based coating according to claim 1, characterized in that, The mass-to-volume ratio of the diamond powder, acetone, anhydrous ethanol, dispersion, composite sol, and protective sol is 100g:190-210mL:190-210mL:45-55mL:178-218mL:45-55mL.
3. The diamond high-temperature antioxidant silicon-based coating according to claim 1, characterized in that, The mixed gas is a mixture of argon and oxygen; The volume ratio of argon to oxygen is 3:
1.
4. The diamond high-temperature antioxidant silicon-based coating according to claim 1, characterized in that, The preparation of the dispersion includes the following steps: Anhydrous ethanol was added to silicon carbide nanocrystals and ultrasonically dispersed to obtain a dispersion. The mass-to-volume ratio of the silicon carbide nanocrystals to anhydrous ethanol is 1 g: 50 mL.
5. The diamond high-temperature antioxidant silicon-based coating according to claim 1, characterized in that, The preparation of the composite sol includes the following steps: A1. Add concentrated nitric acid to the multi-walled carbon nanotubes, reflux and stir at a constant temperature, filter out the filtrate, collect the particles, wash the particles with deionized water, and dry the washed particles in a vacuum drying oven to obtain activated multi-walled carbon nanotubes. A2. Activated multi-walled carbon nanotubes were dispersed in anhydrous ethanol, and 3-(methacryloyloxy)propyltrimethoxysilane was added and stirred to obtain a mixture. The mixture was centrifuged, the supernatant was filtered off, the precipitate was retained, and the precipitate was washed with anhydrous ethanol. The washed precipitate was dried in a vacuum drying oven to obtain modified multi-walled carbon nanotubes. A3. Mix anhydrous ethanol and tetraethyl orthosilicate and stir magnetically. Add the acid-water mixture and stir to obtain solution A. A4. Modified multi-walled carbon nanotubes were dispersed in anhydrous ethanol to obtain solution B. Solution B was added to solution A and stirred. Butyl titanate was added and stirred. Tantalum pentoxide nanocrystals, hafnium dioxide nanocrystals and yttrium oxide nanocrystals were added in sequence and ultrasonically dispersed. Silicon carbide nanocrystals were added and ultrasonically dispersed. 3-(methacryloyloxy)propyltrimethoxysilane was added and stirred to obtain a composite sol.
6. The diamond high-temperature antioxidant silicon-based coating according to claim 5, characterized in that, The mass-to-volume ratio of concentrated nitric acid and multi-walled carbon nanotubes in A1 is 50 mL: 0.5 g; The activated multi-walled carbon nanotubes in A2 are dispersed in anhydrous ethanol, and the mass-to-volume ratio of the activated multi-walled carbon nanotubes to the anhydrous ethanol is 0.5g:50mL. The mass-to-volume ratio of the activated multi-walled carbon nanotubes and 3-(methacryloyloxy)propyltrimethoxysilane is 0.5 g: 1 mL.
7. The diamond high-temperature antioxidant silicon-based coating according to claim 5, characterized in that, The volume ratio of anhydrous ethanol to tetraethyl orthosilicate in A3 is 1:5; The mass-to-volume ratio of modified multi-walled carbon nanotubes and anhydrous ethanol in A4 is 0.5 g: 50 mL. The mass-to-volume ratio of solution B, solution A, tetrabutyl titanate, tantalum pentoxide nanocrystals, hafnium dioxide nanocrystals, yttrium oxide nanocrystals, silicon carbide nanocrystals, and 3-(methacryloyloxy)propyltrimethoxysilane is 50 mL: 141 mL: 2 mL: 3 g: 1 g: 0.5 g: 1 g: 5 mL.
8. The diamond high-temperature antioxidant silicon-based coating according to claim 5, characterized in that, The acid-water mixture is composed of deionized water and dilute hydrochloric acid. The volume ratio of the deionized water to the dilute hydrochloric acid is 20:1; The mass concentration of the dilute hydrochloric acid is 15%.
9. The diamond high-temperature antioxidant silicon-based coating according to claim 1, characterized in that, The preparation of the protective sol includes the following steps: adding yttrium oxide and silicon nitride into anhydrous ethanol and dispersing them by ultrasonication to obtain the protective sol.
10. The diamond high-temperature antioxidant silicon-based coating according to claim 9, characterized in that, The mass-to-volume ratio of yttrium oxide, silicon nitride, and anhydrous ethanol is 0.5 g: 1.5 g: 50 mL.