Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on combination of low-energy self-heat-release technology and bionic glass membrane synergistic oxygen blocking

Abstract

The invention discloses a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on combination of a low-energy self-heat-release technology and a bionic glass film synergistic oxygen barrier. The coating comprises a matrix layer, a transition layer and a bionic glass layer. Compared with the prior art, the ZrB2-SiC ceramic coating has the advantages that the problems of oxidation structure defects and high oxygen permeability of an existing ZrB2-SiC ceramic coating system are solved. The oxidation activity and the oxidation consumption are reduced, the service temperature is increased, the oxidation protection effect is enhanced, and the service life is prolonged. After oxidation at 1700 DEG C for 100 min, the accumulated anti-oxidation protection efficiency is 99.809%, the carbon loss rate is 1.032%, and the stable oxygen barrier protection effect at the high temperature area of 1700 DEG C is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of surface protection coatings for carbon-based composite materials and their preparation, and particularly to a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating that combines low-energy self-exothermic technology with a biomimetic glass film to synergistically prevent oxygen. It can be used for the oxidation corrosion protection of carbon / carbon composite materials and their components in high-temperature environments. In particular, it is applied to the wings of aerospace aircraft, and has a stable high-temperature oxidation resistance effect in an aerobic environment at 1700°C. Background Art

[0002] As an urgently needed structural material serving the aerospace strategies of major countries in the world, carbon structural materials have sp 2 hybrid orbitals and exhibit extremely anisotropic crystal combinations. Through various methods of composite reinforcement, carbon structural materials possess properties such as high melting point, low density, high high-temperature strength, and thermal shock resistance. Therefore, they are widely regarded as suitable high-temperature thermal structural materials for manufacturing engineering components such as hypersonic aircraft. As carbon-based materials, their extreme sensitivity to oxygen is an important factor restricting their production. When the working temperature of engineering components made of carbon structural materials exceeds 370°C, the carbon structural materials will oxidize to produce CO or CO2. When the temperature exceeds 600°C, the oxidation phenomenon will become more intense, posing a potential safety hazard to the use of engineering components.

[0003] Among ultra-high temperature ceramic coating materials, the ZrB2-SiC ceramic system is more excellent. During the oxidation process, SiC can generate SiO2 through reactions during high-temperature oxidation, and ZrB2 forms ZrO2 during high-temperature oxidation. Multiple oxidation products combine to form a Zr-B-Si-O composite glass film, filling the coating pores and effectively hindering the infiltration of oxygen. For example, Li T et al. (Li T, Zhang Y, Lv J, et al. Eliminated siliconization corrosion and improved oxidation resistances of SiC-Si coated C / C composites via a ZrB2-rich transition layer [J]. Corrosion Science, 2022, 195: 109986.) disclosed a ZrB2-SiC-Si ternary phase oxygen barrier coating and its preparation method, and pointed out that for the ternary phase ceramic material under static oxidation protection at 1500 °C, the mass loss of the coating was only 0.09%. Li L et al. (Li L, Yu Y, Yang J, et al. A ZrB2-SiC(Al) coating with improved oxidation resistance for C / C composites: Design, experimental verification and oxidation mechanism [J]. Journal of the European Ceramic Society, 2024, 44(6): 3487-3500.) prepared a ZrB2-SiC(Al) coating by spark plasma sintering. By optimizing the doping amount of alumina, a ZrB2-SiC(Al) coating with excellent oxidation resistance can be obtained. The doping of Al can promote the dissolution of Zr atoms in silica, strengthen the Si-O bond, thus promoting the change of the glass structure and improving the oxidation resistance.

[0004] However, in a high-temperature and oxygen-rich environment, the vapor pressure of B2O3 in the oxidation products of ZrB2 gradually increases, leading to its rapid evaporation, resulting in the loosening of the coating structure and increasing the diffusion path of oxygen in the coating. In addition, after exceeding 1625 °C, the oxidation mode of SiC in an oxygen-rich environment changes from a passive oxidation mode to an active oxidation mode, generating SiO gas and further damaging the oxygen barrier structure of the coating. Given the easy oxidation characteristics of carbon structural materials, the stability and integrity of the oxygen barrier structure and the coating glass film are crucial for inhibiting oxygen penetration. -

[0005] The present invention constructs a biomimetic glass film based on the self-healing repair mechanism of Dracaena cochinchinensis, and uses the low-energy self-exothermic technology to prepare a biomimetic glass film on the basis of the Y2O3-ZrSi2-ZrB2-SiC coating for synergistic oxygen barrier. By constructing a unique coating structure, relying on the synergistic effect of the self-generated film inside the coating and the biomimetic glass film, the loss of the self-generated film inside is reduced. Relying on the high dispersion degree of oxides in the biomimetic glass film, cracks and holes and other defects generated on the surface can be effectively healed during the oxidation process, inhibiting the dynamic evolution of the coating structure and hindering the oxygen permeability. At the same time, the extension of the heat treatment time improves the bonding degree between the coating and the biomimetic glass film, weakens the volatility of the glass film, and improves the stability of the oxygen barrier structure. The high-temperature oxidation resistance temperature of the existing ZrB2-SiC-based oxygen barrier coating is increased by about 100-400 °C. Among them, the final oxygen permeability of the biomimetic glass film with a film-forming treatment of 360 min is 0.600%, and the average oxygen permeability is 1.047%, showing a significant antioxidant gain effect. The structure factor and the inerting factor values of the inerting oxygen barrier performance are 1.446% and 2.065% respectively. Summary of the Invention

[0006] To solve the above problems, the technical solution provided by the present invention is as follows:

[0007] A Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a biomimetic glass film for synergistic oxygen barrier, characterized by comprising a substrate layer, a transition layer, and a biomimetic glass layer. Among them, the substrate layer includes a graphite-based material, the transition layer is a Y2O3-ZrSi2-ZrB2-SiC composite phase coating, and the biomimetic glass layer includes a Zr-Y-Si-O glass layer. The substrate layer and the biomimetic glass layer are respectively arranged on the innermost and outermost sides. The transition layer is arranged between the substrate layer and the biomimetic glass layer.

[0008] Among them, the present invention selects Y2O3 and ZrSi2, which can improve the coating density and have high oxidation resistance, as doping additives to make up for the defects of the ZrB2-SiC coating during high-temperature oxidation; Y2O3 promotes the generation of more Y2SiO5 and Y2Si2O7 in the glass film, and due to the effect of pinning, a Zr-B-Si-O-Y composite phase glass layer is formed. At the same time, Y 3+ is a high-field-strength ion, which has a large agglomeration effect on the glass network structure, increases the overall viscosity of the glass layer, and inhibits the volatilization of SiO2 at high temperatures. The addition of ZrSi2 promotes the formation of ZrSiO4 and enhances the stability of the transition layer. These nanocrystalline particles embedded in the transition layer deflect the diffusion path of oxygen when contacting oxygen, thereby reducing the internal erosion of oxygen to promote the oxidation inhibition ability and reducing the oxygen diffusion rate.

[0009] Among them, the Zr-Y-O nano-powder prepared by low-energy self-exothermic combustion synthesis of the present invention, Y 3+ has an ionic radius (0.092 nm) that is only slightly larger than that of Zr 4+ with an ionic radius of (0.082 nm). During the synthesis process, Y 3+ replaces the position of Zr 4+ in the unit cell, forming a stable fluorite structure and generating a solid solution Zr 0.935 Y 0.065 O 1.968 . At the same time, lattice distortion occurs, which has a greater deflection ability for O during the diffusion process. The degree of dispersion of the oxides ZrSiO4 and Y2Si2O7 in the biomimetic glass film of the present invention is high, and it can effectively heal defects such as cracks and holes generated on the surface during the oxidation process, inhibit the dynamic evolution of the coating structure, and effectively hinder the penetration of oxygen. At the same time, the extension of the heat treatment time improves the bonding degree between the coating and the biomimetic glass film, weakens the volatility of the glass film, and improves the stability of the oxygen barrier structure. The crystallization degree of Y2Si2O7 is relatively high, which can effectively deflect the diffusion direction of oxygen, reduce the erosion of oxygen on the inside of the coating, and thus achieve antioxidant protection for the carbon matrix.

[0010] Particularly, the doping content of Y2O3 in the transition layer Y2O3-ZrSi2-ZrB2-SiC is 0.5-3.5 mol%, the doping content of ZrSi2 is 1-4.0 mol%, and the balance is the main phase ceramics of zirconium boride and silicon carbide; the biomimetic glass layer is a Zr-Y-Si-O material.

[0011] Particularly, the thickness of the transition layer is 1000-4000 μm, and the thickness of the biomimetic glass layer is 500-1500 μm.

[0012] In addition, the present invention also provides a preparation method of a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a biomimetic glass film for synergistic oxygen barrier, including:

[0013] Step 1: Mix the solutions. Weigh 5.00-7.00 g of Y(NO3)3·6H2O and dissolve it in 80-100 ml of deionized water to obtain an aqueous solution of yttrium. Then, weigh 3.00-5.00 g of urea (CH4N2O) and add it to the yttrium nitrate solution, stir evenly to ensure that the urea is completely dissolved.

[0014] Step 2: Low-energy self-exothermic combustion synthesis of Y2O3. Place the uniformly mixed solution obtained in Step 1 into a crucible and put it in an electric furnace. Through trigger-type microwave preheating, quickly heat the solution to about 150°C to 200°C. During this process, water evaporates, the solution gradually concentrates, urea begins to decompose and react with yttrium nitrate, releasing heat and generating a combustion reaction. In the combustion reaction, urea acts as a reducing agent and is converted into CO2 and water vapor. The heat released after combustion causes the reaction temperature to rise rapidly, and finally Y2O3 powder is formed. The preparation reaction formula is as follows:

[0015]

[0016] Step 3: Mix the solutions. Weigh 6.00 - 8.00 g of Zr(NO3)4·5H2O, 4.00 - 6.00 g of Y(NO3)3·6H2O, and 3.00 - 5.00 g of urea (CH4N2O) into a beaker, add 80 - 100 ml of deionized water to obtain an aqueous solution of zirconium and yttrium. Place the beaker on a magnetic stirrer, control the rotation speed at 200 r / min, and mix for 30 min.

[0017] Step 4: Low-energy self-exothermic combustion synthesis of Zr-Y-O solid solution powder. Place the uniformly mixed solution obtained in Step 3 into a crucible and put it in an electric furnace. Quickly heat the solution to about 650 - 700°C through trigger-type microwave preheating. During this process, water evaporates, the solution gradually concentrates, urea begins to decompose and react with yttrium nitrate and zirconium nitrate, releasing heat and generating a combustion reaction. The heat released by the combustion reaction causes the reaction temperature to rise rapidly, and finally Zr-Y-O solid solution powder is formed.

[0018] Step 5: Mix the raw materials. Use zircon powder, boron powder, silicon powder, and yttrium oxide as raw materials, and mix them according to a volume ratio of 6:3:7:1 - 6:5:8:1.5. After ball milling at a ball mill rotation speed of 350 r / min for 5 h, a mixed powder is obtained.

[0019] Step 6: Self-propagating combustion synthesis to prepare powder: Press the composite powder obtained in Step 5 into a block with a diameter of 15 mm and a height of 6 mm through a tablet press, and synthesize the powder through low-temperature exothermic reaction in an argon atmosphere with a pressure of 5 MPa in a self-propagating furnace.

[0020] Step 7: Coating sintering: Wrap the self-propagating powder around a graphite matrix and fill it into a graphite mold with a diameter of 20 mm, and perform plasma spark sintering in a vacuum environment (-99.5 MPa) to prepare a ZrSi2 - bonded Y2O3 modified ZrB2 - SiC coating.

[0021] Step 8: Film formation treatment: Mix the Zr-Y-O nano powder obtained in Step 4 with silica sol to form a colloid, with a slurry ratio of 1:6. Brush it on the surface of the coating and place it in a muffle furnace at 1200°C for film formation treatment to form a glass film.

[0022] In the above method, the chemical composition of the modified coating in the biomimetic film-forming combined with rare earth-doped binary silicide modified gradient oxygen barrier coating prepared is: Y2O3-ZrSi2-ZrB2-SiC; the component of the biomimetic glass layer is: Zr-Y-Si-O glass layer.

[0023] Particularly, in step 1, the molar ratio range of Y(NO)·6HO and urea (CHNO) is: 3:7 to 4:9.

[0024] Particularly, in step 2, the heating rate of synthesizing nano-Y2O3 powder by low-energy self-exothermic combustion is 100 °C / min, and the heating atmosphere is carried out in an air aerobic environment.

[0025] Particularly, in step 3, the molar ratio range of Zr(NO)·5HO, Y(NO)·6HO and urea (CHNO) is: 3:2:5 to 4:3:16. Fuel ratio: It shows a state of fuel remaining, and it is necessary to obtain O2 from the air to act as an auxiliary combustion function to make the fuel burn fully.

[0026] Particularly, in step 4, the microwave preheating and heating rate of the electric furnace is 150 °C / min. The heating temperature fluctuates by ±15%, as Figure 3

[0027] shown, the grain size of the powder synthesized by low-energy self-exothermic synthesis is about 70-75 nm, and ZrO2 is stabilized in the tetragonal crystal form by Y2O3. The chemical reaction that occurs is as follows:

[0028]

[0029] Particularly, in step 6, the preheating temperature of the self-propagating combustion synthesis furnace is 750-800 °C, and a tungsten wire with a diameter of 1.5 mm is used for ignition.

[0030] Particularly, in step 7, the temperature range for preparing the Y2O3-ZrSi2-ZrB2-SiC coating by plasma spark sintering is 1450-1500 °C.

[0031] The advantages of the present invention compared with the prior art are:

[0032] 1. The present invention utilizes the self-healing and repair mechanism of Dracaena cinnabari, and adopts a low-energy self-exothermic technology to prepare a composite ceramic coating with a Y2O3-ZrSi2-ZrB2-SiC transition layer and an outer layer of bionic glass film for synergistic oxygen barrier. The outer bionic glass layer relies on structural oxygen barrier, reducing the internal oxidation loss of the matrix layer and the transition layer structures, reducing oxidation activity and oxidation consumption, and having advantages such as improving the oxygen barrier quality. Moreover, it can effectively avoid the problem that the coating structure becomes loose due to the inherent high activity of transition metal borides, which further exacerbates the oxidation loss and leads to failure. The transition layer gives play to the characteristics of rare earth oxide-doped binary silicides in promoting sintering densification and complex film formation, having the advantages of enhancing the densification of the coating structure and inhibiting oxygen diffusion, achieving a multiple synergistic oxygen barrier effect.

[0033] 2. The powder of the outer bionic glass layer of the present invention is synthesized by trigger-type microwave preheating combustion in low-energy self-exothermic. The solution temperature is rapidly increased to the preheating temperature of 550 °C by microwave heating, making it close to the trigger temperature of 600 °C for the combustion reaction. The preheating time is significantly shortened. Compared with traditional commercial powders, the synthesized powder has a finer particle size. The combustion reaction is completed within 1 - 2 minutes, and the energy utilization rate is as high as 98.97%. The combustion reaction releases heat sufficiently, reducing the external energy input. During the synthesis process, Y 3+ replaces Zr 4+ in the crystal cell, forming a stable fluorite structure and generating a solid solution Zr 0.935 Y 0.065 O 1.968 . At the same time, lattice distortion occurs, having a greater deflection ability for O during the diffusion process. And most ZrO2 is stabilized as a tetragonal crystal form by Y2O3, reducing the stress accumulation during the phase change process.

[0034] 3. As an effective high-temperature oxygen barrier protection coating for carbon / carbon composites, the present invention provides a preparation method of a composite ceramic coating that combines a Y2O3-ZrSi2-ZrB2-SiC coating prepared based on low-energy self-exothermic technology with a bionic glass film for synergistic oxygen barrier. It overcomes the problem of oxidation and loosening of the ZrB2-SiC coating above 1700 °C, not only improves the service temperature of the ZrB2-SiC coating, but also enhances the oxidation protection effect and working life. Moreover, compared with the traditional multi-layer structure coating preparation processes (such as plasma spraying and spark plasma sintering), the present film-forming treatment process has the advantages of simple preparation method, high efficiency, and reduction of energy waste. At the same time, after film-forming treatment, due to the dispersion distribution of particles such as Y2Si2O7 and ZrSiO4, the viscosity of the glass film is increased, and the volatilization tendency of the glass film at high temperature is inhibited. It effectively heals defects such as cracks and holes generated on the surface, inhibits the dynamic evolution of the coating structure, and hinders the oxygen permeability. At the same time, it also overcomes the problems of high sintering temperature and energy waste in the conventional SPS preparation method. In the case of oxidation at 1700 °C for 100 min, the cumulative antioxidant protection efficiency is as high as 99.997%, and the carbon loss rate is only 1.032%, showing excellent high-temperature oxidation resistance.

[0035] 4. The present invention uses a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating that combines low-energy self-exothermic technology with a bionic glass film for synergistic oxygen barrier. The high-temperature stable oxygen barrier protection temperature of the graphite material can be increased to 1700 °C, which is about 100 - 400 °C higher than that of the existing ZrB2-SiC-based oxygen barrier coating. The final oxygen permeability of the bionic glass film after 100 min of film-forming treatment is 0.600%, and the average oxygen permeability is 1.047%. The structure factor and the inerting factor values of the inerting oxygen barrier performance are the lowest, which are 1.446% and 2.065% respectively, showing a significant antioxidant gain effect. At the same time, by using self-propagating combustion synthesis, the coating preparation temperature can be reduced to 1450 °C at most, which is about 450 °C lower than the sintering temperature of the existing conventional SPS preparation method, greatly saving energy consumption and reducing the difficulty of product preparation.

[0036] In summary, the present invention overcomes the problems of high sintering temperature, high material preparation difficulty, energy waste, high-temperature oxidation and loosening, and low antioxidant protection temperature existing in the existing ZrB2-SiC binary phase ceramic coating. It has the advantages of reducing the sintering temperature, simplifying the material preparation difficulty, saving energy consumption, enhancing the densification of the coating structure, reducing internal defects of the coating, reducing oxidation activity and oxidation consumption, increasing the service temperature, enhancing the oxidation protection effect and working life, and achieving the effect of stable oxygen barrier protection in the high-temperature zone of 1700 °C. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the process flow chart of the present invention.

[0038] Figure 2 This is the XRD diffraction pattern of the Zr-Y-O powder synthesized by low-energy self-exothermic combustion in the present invention.

[0039] Figure 3 This is the histogram of the grain size frequency distribution of the Zr-Y-O powder synthesized by low-energy self-exothermic combustion in the present invention.

[0040] Figure 4 (a) This is the HAADF dark field image of the Zr-Y-O powder synthesized by low-energy self-exothermic combustion in the present invention.

[0041] Figure 4 (b) This is the low-magnification TEM image of the Zr-Y-O powder synthesized by low-energy self-exothermic combustion in the present invention.

[0042] Figure 4 (c) This is the corresponding EDS energy spectrum image of the Zr-Y-O powder synthesized by low-energy self-exothermic combustion in the present invention.

[0043] Figure 4 (d) This is the high-magnification TEM image of the Zr-Y-O powder synthesized by low-energy self-exothermic combustion in the present invention.

[0044] Figure 5 This is the XRD diffraction pattern of the glass films obtained in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0045] Figure 6 (a)-(c) These are the low-magnification cross-sectional BSE-SEM images of the coatings before oxidation after film-forming treatment in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0046] Figure 6 (a1)-(c1) These are the BSE-SEM images of the coating-substrate interfaces before oxidation of the coatings after film-forming treatment in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0047] Figure 6 (a2)-(c2) These are the high-magnification cross-sectional BSE-SEM images of the coatings before oxidation after film-forming treatment in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0048] Figure 6 (a3)-(c3) These are the EDS energy spectrum images of the O element corresponding to the cross-sections of the coatings before oxidation of the coatings after film-forming treatment in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0049] Figure 7(a)-(c) are low-magnification BSE-SEM micrographs of the cross-sections of the coatings after film-forming treatment and oxidation at 1700 °C for 100 min in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0050] Figure 7 (a1)-(c1) are BSE-SEM images of the interfaces between the coatings and the substrates after film-forming treatment and oxidation at 1700 °C for 100 min in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0051] Figure 7 (a2)-(c2) are high-magnification BSE-SEM micrographs of the cross-sections of the coatings after film-forming treatment and oxidation at 1700 °C for 100 min in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0052] Figure 7 (a3)-(c3) are EDS spectra of the O element in the cross-sections of the coatings after film-forming treatment and oxidation at 1700 °C for 100 min in Example 3, Example 7 and Comparative Example 1 of the present invention.

[0053] Figure 8 are oxygen permeability curves of the coatings obtained in Example 1, Example 3, Example 5, Example 7, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention during oxidation at 1700 °C for 100 min after film-forming treatment.

[0054] Figure 9 are cumulative antioxidant protection efficiency curves of the coatings obtained in Example 1, Example 3, Example 5, Example 7, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention during oxidation at 1700 °C for 100 min after film-forming treatment. Detailed Embodiments

[0055] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings. It should be emphasized that the embodiments are only some implementation solutions of the present invention and do not represent all implementation solutions. The components shown in the drawings can be configured and designed differently according to actual needs. Among them, the preparation of Y2O3 powder and Zr-Y-O powder by low-energy self-exothermic combustion synthesis in each of the embodiments and comparative examples includes the following steps:

[0056] Step 1: Preparation of Y2O3 powder by low-energy self-exothermic combustion synthesis. Weigh 5.00 - 7.00 g of Y(NO3)3·6H2O and dissolve it in 80 - 100 ml of deionized water. Weigh 3.00 - 5.00 g of urea (CH4N2O) and add it to the yttrium nitrate solution, then stir evenly. Through trigger-type microwave preheating, quickly heat the solution to about 150°C to 200°C. The heat released by the combustion reaction causes the reaction temperature to rise rapidly, and finally Y2O3 powder is formed.

[0057] Step 2: Preparation of Zr-Y-O powder by low-energy self-exothermic combustion synthesis. Weigh 6.00 - 8.00 g of Zr(NO3)4·5H2O, 4.00 - 6.00 g of Y(NO3)3·6H2O and 3.00 - 5.00 g of urea (CH4N2O) into a beaker, add 80 - 100 ml of deionized water, and stir evenly. Through trigger-type microwave preheating, quickly heat the solution to about 650 - 700°C. The heat released by the combustion reaction causes the reaction temperature to rise rapidly, and finally Zr-Y-O solid solution powder is formed.

[0058] Figure 2 The phase structure of the Zr-Y-O solid solution powder prepared by low-energy self-exothermic synthesis is shown. Zr 0.935 Y 0.065 O 1.968 phases and monoclinic ZrO2 phase are detected in the powder. The diffraction peaks of each phase are sharp, indicating good crystallinity. The grain size frequency distribution histogram of the Zr-Y-O solid solution powder prepared by low-energy self-exothermic synthesis is as Figure 3 shown. The grain size of the synthesized Zr-Y-O solid solution powder is about 70 - 75 nm. At the same time, ZrO2 is stabilized in the tetragonal phase by Y2O3. The high-resolution transmission of the Zr-Y-O solid solution powder prepared by low-energy self-exothermic synthesis is as Figure 4 shown. It can be seen that the synthesized powder has distinct particles overall. The particle morphology is in the shape of multi-sided regular cubes, and the particles are relatively dispersed. The three elements Zr, Y, and O in the synthesized powder are relatively evenly dispersed, and the lattice fringes are clear, indicating good crystallinity of the product. The three elements Zr, Y, and O account for 47.39%, 1.83%, and 50.78% respectively.

[0059] Example 1:

[0060] Using graphite as the substrate, an oxygen barrier coating is composed of "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". Among them, the doping content of Y2O3 is .5 mol%, and the doping content of ZrSi2 is 1.0 mol%. The sintering temperature is 1500°C, the holding time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1200°C, and the heat treatment time is 100 min.

[0061] In this embodiment, graphite is used as the substrate, and the oxygen barrier coating is composed of "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer is 0.5 mol%, and the doping content of ZrSi2 is 1.0 mol%. The thickness of the oxygen barrier coating is 4000 μm, and the thickness of the biomimetic glass film is 1500 μm. The specific steps are as follows:

[0062] Step 1: Prepare composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, mixing them in a volume ratio of 6:3:7:1 to 6:5:8:1.5, and synthesizing powder by low-temperature exothermic combustion in a self-propagating furnace under an argon atmosphere with a pressure of 5 MPa.

[0063] Step 2: Sinter the coating. Crush the powder block after self-propagating combustion synthesis, and add 40% of SiC according to the volume ratio for ball milling treatment. Put the composite powder into a plasma spark sintering mold with a diameter of 15 mm. The sintering temperature is 1500 °C, the holding time is 5 min, and the sintering pressure is 30 MPa.

[0064] Step 3: Film-forming treatment of the biomimetic glass film. Mix the Zr-Y-O solid solution powder prepared by the above microwave preheating combustion synthesis with silica sol to form a colloid, brush the colloid on the surface of the coating, and dry it in a constant-temperature drying oven at 50 °C for 30 s; place the composite coating in a high-temperature resistance furnace for film-forming treatment, the heat treatment temperature is 1200 °C, and the heat treatment time is 100 min.

[0065] This embodiment provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a biomimetic glass film for synergistic oxygen barrier. In this embodiment, Y2O3 powder is prepared by low-energy self-exothermic combustion synthesis, Zr-Y-O powder is synthesized by low-energy self-exothermic synthesis, composite powder is prepared by self-propagating combustion synthesis, the coating is sintered by plasma spark, and finally the film-forming treatment of the biomimetic glass film is carried out. The oxidation protection efficiency results at 1700 °C are shown in Table 1. It can be seen from the table that this embodiment is superior to Comparative Examples 1, 2, and 3 in terms of oxidation protection efficiency. Figure 8 , Figure 9 The oxygen permeability curve and cumulative protection efficiency of this coating oxidized at 1700 °C for 100 min are respectively shown. The results show that the coating preparation method described in this embodiment effectively improves the oxidation resistance of the coating.

[0066] Example 2:

[0067] The oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer" with graphite as the substrate. The doping content of Y2O3 is 1.0 mol%, and the doping content of ZrSi2 is 1.5 mol%. The sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1200 °C, and the heat treatment time is 100 min

[0068] In this embodiment, the oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer" with graphite as the substrate. In the Y2O3-ZrSi2-ZrB2-SiC layer, the doping content of Y2O3 is 1.0 mol%, and the doping content of ZrSi2 is 1.5 mol%. The thickness of the oxygen barrier coating is 4000 μm, and the thickness of the biomimetic glass film is 1500 μm. The specific steps are as follows:

[0069] Step 1: Prepare composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, mixing them in a volume ratio of 6:5:7:1.5 - 6:5:8:2, and synthesizing powder by low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa through a self-propagating furnace.

[0070] Step 2: Sinter the coating. Crush the powder block after self-propagating combustion synthesis, and add 40% of SiC according to the volume ratio for ball milling treatment. Put the composite powder into a plasma spark sintering mold with a diameter of 15 mm. The sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa.

[0071] Step 3: Film-forming treatment of the biomimetic glass film. Mix the Zr-Y-O solid solution powder prepared by the above microwave preheating combustion synthesis with silica sol to form a colloid. Brush the colloid on the surface of the coating and dry it in a constant temperature drying oven at 50 °C for 30 s; Place the composite coating in a high-temperature resistance furnace for film-forming treatment, with a heat treatment temperature of 1200 °C and a heat treatment time of 100 min.

[0072] This embodiment provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a biomimetic glass film for synergistic oxygen barrier. In this embodiment, Y2O3 powder is prepared by low-energy self-exothermic combustion synthesis, Zr-Y-O powder is synthesized by low-energy self-exothermic synthesis, composite powder is prepared by self-propagating combustion synthesis, the coating is sintered by plasma spark, and finally the film-forming treatment of the biomimetic glass film is carried out. The oxidation protection efficiency results at 1700 °C are shown in Table 1. It can be seen from the table that this embodiment is superior to Comparative Examples 1, 2, and 3 in terms of oxidation protection efficiency. The results show that the coating preparation method described in this embodiment effectively improves the antioxidant performance of the coating.

[0073] Example 3:

[0074] Using graphite as the substrate, an oxygen barrier coating is composed of "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 is 1.5 mol%, and the doping content of ZrSi2 is 2.0 mol%. The sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1200 °C, and the heat treatment time is 100 min

[0075] In this example, using graphite as the substrate, an oxygen barrier coating is composed of "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer is 1.5 mol%, and the doping content of ZrSi2 is 2.0 mol%. The thickness of the oxygen barrier coating is 4000 μm; the thickness of the biomimetic glass film is 1500 μm. The specific steps are as follows:

[0076] Step 1: Prepare composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, mix them in a volume ratio of 7:5:7:2 to 7:5.5:7:2.5, and synthesize powder through low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa in a self-propagating furnace.

[0077] Step 2: Sinter the coating. Crush the powder block after self-propagating combustion synthesis, and add 40% of SiC according to the volume ratio for ball milling. Put the composite powder into a plasma spark sintering mold with a diameter of 15 mm. The heating rate is 100 °C / min, the sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa.

[0078] Step 3: Film-forming treatment of the biomimetic glass film. Mix the Zr-Y-O solid solution powder prepared by the above microwave preheating combustion synthesis with silica sol to form a colloid. Brush the colloid on the surface of the coating and dry it in a constant temperature drying oven at 50 °C for 30 s; place the composite coating in a high-temperature resistance furnace for film-forming treatment, with a heat treatment temperature of 1200 °C and a heat treatment time of 100 min.

[0079] This example provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a biomimetic glass film for synergistic oxygen barrier. The phase structure of the glass film after 100 min of film-forming treatment at 1200 °C is as Figure 5As shown, it can be seen that after the film-forming treatment, the surface mainly consists of oxidation products ZrO2, ZrSiO4, Y2Si2O7, as well as unreacted ZrB2 and SiC. The diffraction peaks of each phase are sharp, indicating good crystallinity. The surface morphology and cross-sectional morphology of the composite coating before oxidation are as Figure 6 shown. After heat treatment, oxygen is mainly distributed on the surface of the coating, which is the oxide of the biomimetic glass film. The oxygen content is lower closer to the carbon matrix. This indicates that the film-forming treatment has not had a significant impact on the interior of the coating. The surface morphology and cross-sectional morphology of the composite coating after oxidation at 1700°C for 100 min are as Figure 7 shown. An obvious oxide layer appears, with a thickness of about 407 μm. This shows that the introduction of the biomimetic glass has reduced the thickness of the oxide layer by 52.3% compared to Comparative Example 1. The oxidation protection efficiency results at 1700°C are shown in Table 1. It can be seen from the table that this example is superior to Comparative Examples 1, 2, and 3 in terms of oxidation protection efficiency. Figure 8 , Figure 9 respectively show the oxygen permeability curve and cumulative protection efficiency of this coating during oxidation at 1700°C for 100 min. The results indicate that the coating preparation method described in this example effectively improves the oxidation resistance of the coating.

[0080] Example 4:

[0081] Using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 is 2.0 mol%, and the doping content of ZrSi2 is 2.5 mol%. The sintering temperature is 1500°C, the holding time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1200°C, and the heat treatment time is 100 min.

[0082] In this example, using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer is 2.0 mol%, and the doping content of ZrSi2 is 2.5 mol%. The thickness of the oxygen barrier coating is 4000 μm; the thickness of the biomimetic glass film is 1500 μm. The specific steps are as follows:

[0083] Step 1: Prepare the composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, mix them in a volume ratio of 7:5.5:7:3 to 7:6:7:3.5, and synthesize the powder by low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa through a self-propagating furnace.

[0084] Step 2: Sinter the coating. The powder compact after self-propagating combustion synthesis is crushed and ball-milled by adding 40% of SiC according to the volume ratio. The composite powder is put into a plasma spark sintering die with a diameter of 15 mm. The heating rate is 100 °C / min, the sintering temperature is 1500 °C, the holding time is 5 min, and the sintering pressure is 30 MPa.

[0085] Step 3: Film-forming treatment of the bionic glass film. The Zr-Y-O solid solution powder prepared by microwave preheating combustion synthesis above is mixed with silica sol to form a colloid, and the colloid is brushed on the surface of the coating and dried in a constant temperature drying oven at 50 °C for 30 s; the composite coating is placed in a high-temperature resistance furnace for film-forming treatment, the heat treatment temperature is 1200 °C, and the heat treatment time is 100 min.

[0086] This embodiment provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a bionic glass film for synergistic oxygen barrier. In this embodiment, Y2O3 powder is prepared by low-energy self-exothermic combustion synthesis, Zr-Y-O powder is synthesized by low-energy self-exothermic synthesis, composite powder is prepared by self-propagating combustion synthesis, the coating is sintered by plasma spark, and finally the film-forming treatment of the bionic glass film is carried out. The oxidation protection efficiency results at 1700 °C are shown in Table 1. It can be seen from the table that this embodiment is superior to Comparative Examples 1, 2, and 3 in terms of oxidation protection efficiency. The results show that the coating preparation method described in this embodiment effectively improves the oxidation resistance of the coating.

[0087] Example 5:

[0088] Using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + bionic film-forming glass layer". The doping content of Y2O3 is 2.5 mol%, and the doping content of ZrSi2 is 3.0 mol%. The sintering temperature is 1500 °C, the holding time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1200 °C, and the heat treatment time is 100 min

[0089] In this embodiment, using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + bionic film-forming glass layer". The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer is 2.5 mol%, and the doping content of ZrSi2 is 3.0 mol%. The thickness of the oxygen barrier coating is 4000 μm; the thickness of the bionic glass film is 1500 μm. The specific steps are as follows:

[0090] Step 1: Preparation of composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above-mentioned microwave preheating combustion synthesis as raw materials, they are mixed according to a volume ratio of 7:5.5:7:3 to 7:6:7:3.5. Through a self-propagating furnace, powders are synthesized by low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa.

[0091] Step 2: Sintering of the coating. The powder block after self-propagating combustion synthesis is subjected to crushing treatment, and 40% of SiC is added according to the volume ratio for ball milling. The rotational speed of the ball mill is 350 r / min, and ball milling is carried out for 5 h. The composite powder is placed in a plasma spark sintering mold with a diameter of 15 mm. The heating rate is 100 °C / min, the sintering temperature is 1500 °C, the holding time is 5 min, and the sintering pressure is 30 MPa.

[0092] Step 3: Film-forming treatment of the biomimetic glass film. The Zr-Y-O solid solution powder prepared by the above-mentioned microwave preheating combustion synthesis is mixed with silica sol to form a colloid. The colloid is brushed on the surface of the coating and dried in a constant-temperature drying oven at 50 °C for 30 s. The composite coating is placed in a high-temperature resistance furnace for film-forming treatment. The heat treatment temperature is 1200 °C, and the heat treatment time is 100 min.

[0093] This example provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a biomimetic glass film for synergistic oxygen barrier. In this example, Y2O3 powder is prepared by low-energy self-exothermic combustion synthesis, Zr-Y-O powder is synthesized by low-energy self-exothermic synthesis, composite powder is prepared by self-propagating combustion synthesis, the coating is sintered by plasma spark, and finally, film-forming treatment of the biomimetic glass film is carried out. The oxidation protection efficiency results at 1700 °C are shown in Table 1. It can be seen from the table that this example is superior to Comparative Examples 1, 2, and 3 in terms of oxidation protection efficiency. Figure 8 , Figure 9 respectively show the oxygen permeability curve and cumulative protection efficiency of this coating during oxidation at 1700 °C for 100 min. The results show that the coating preparation method described in this example effectively improves the antioxidant performance of the coating.

[0094] Example 6:

[0095] Using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 is 3.0 mol%, and the doping content of ZrSi2 is 3.5 mol%. The sintering temperature is 1500 °C, the holding time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1200 °C, and the heat treatment time is 100 min

[0096] In this embodiment, the oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer" with graphite as the substrate. The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer is 3.0 mol%, and the doping content of ZrSi2 is 3.5 mol%. The thickness of the oxygen barrier coating is 4000 μm; the thickness of the biomimetic glass film is 1500 μm. The specific steps are as follows:

[0097] Step 1: Prepare composite powder by low-energy self-exothermic combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, mix them in a volume ratio of 7:5.5:7:3 to 7:6:7:3.5, and synthesize powder through low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa in a self-propagating furnace.

[0098] Step 2: Sinter the coating. Crush the powder block obtained by self-propagating combustion synthesis, and add 40% of SiC according to the volume ratio for ball milling. Put the composite powder into a plasma spark sintering mold with a diameter of 15 mm. The heating rate is 100 °C / min, the sintering temperature is 1500 °C, the holding time is 5 min, and the sintering pressure is 30 MPa.

[0099] Step 3: Film-forming treatment of the biomimetic glass film. Mix the Zr-Y-O solid solution powder prepared by the above microwave preheating combustion synthesis with silica sol to form a colloid, and brush the colloid on the surface of the coating. Dry it in a constant-temperature drying oven at 50 °C for 30 s; place the composite coating in a high-temperature resistance furnace for film-forming treatment, with a heat treatment temperature of 1200 °C and a heat treatment time of 100 min.

[0100] This embodiment provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating with oxygen barrier synergistically based on low-energy self-exothermic technology combined with a biomimetic glass film. In this embodiment, Y2O3 powder is prepared by low-energy self-exothermic combustion synthesis, Zr-Y-O powder is synthesized by low-energy self-exothermic synthesis, composite powder is prepared by self-propagating combustion synthesis, the coating is sintered by plasma spark, and finally the film-forming treatment of the biomimetic glass film is carried out. The oxidation protection efficiency results at 1700 °C are shown in Table 1. It can be seen from the table that this embodiment is superior to Comparative Examples 1, 2, and 3 in terms of oxidation protection efficiency. The results show that the coating preparation method described in this embodiment effectively improves the oxidation resistance of the coating.

[0101] Example 7:

[0102] The oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer" with graphite as the substrate. The doping content of Y2O3 is 3.5 mol%, and the doping content of ZrSi2 is 4.0 mol%. The sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1200 °C, and the heat treatment time is 100 min

[0103] In this embodiment, the oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer" with graphite as the substrate. The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer is 3.5 mol%, and the doping content of ZrSi2 is 4.0 mol%. The thickness of the oxygen barrier coating is 4000 μm; the thickness of the biomimetic glass film is 1500 μm. The specific steps are as follows:

[0104] Step 1: Prepare the composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by combustion synthesis of the above solution as raw materials, mix them in a volume ratio of 7:5.5:7:3 to 7:6:7:3.5. Pass through a self-propagating furnace to synthesize the powder body by low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa.

[0105] Step 2: Sinter the coating. Crush the powder block after self-propagating combustion synthesis, and add 40% of SiC according to the volume ratio for ball milling. Put the composite powder into a plasma spark sintering mold with a diameter of 15 mm. The heating rate is 100 °C / min, the sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa.

[0106] Step 3: Film-forming treatment of the biomimetic glass film. Mix the Zr-Y-O solid solution powder prepared by microwave preheating combustion synthesis with silica sol to form a colloid, and brush the colloid on the surface of the coating. Dry it in a constant temperature drying oven at 50 °C for 30 s; place the composite coating in a high-temperature resistance furnace for film-forming treatment, the heat treatment temperature is 1200 °C, and the heat treatment time is 100 min.

[0107] This embodiment provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a biomimetic glass film for synergistic oxygen barrier. The phase structure of the glass film after 100 min of film-forming treatment at 1200 °C is as Figure 5 shown. It can be seen that after the film-forming treatment, the surface is mainly composed of oxidation products ZrO2, ZrSiO4, Y2Si2O7, and unreacted ZrB2 and SiC. The diffraction peaks of each phase are sharp, showing good crystallinity. The surface morphology and cross-sectional morphology of the composite coating before oxidation are as Figure 6As shown, after heat treatment, oxygen is mainly distributed on the surface of the coating, which is the oxide of the biomimetic glass film. The oxygen content is lower closer to the carbon matrix. The surface and cross-sectional morphologies of the composite coating after oxidation at 1700°C for 100 min are as Figure 7 shown. An obvious oxide layer appears, with a thickness of about 26 μm, indicating that the introduction of the biomimetic glass reduces the thickness of the oxide layer by 94.3% compared with Comparative Example 1. The oxidation protection efficiency results at 1700°C are shown in Table 1. It can be seen from the table that this example is superior to Comparative Examples 1, 2, and 3 in terms of oxidation protection efficiency. Figure 8 , Figure 9 respectively show the oxygen permeability curve and cumulative protection efficiency of this coating after oxidation at 1700°C for 100 min. The results show that the coating preparation method described in this example effectively improves the oxidation resistance of the coating.

[0108] Comparative Example 1:

[0109] Using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 is 2.5 mol, and the doping content of ZrSi2 is 3.0 mol%. The sintering temperature is 1500°C, the holding time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1100°C, and the heat treatment time is 100 min.

[0110] In this comparative example, using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating". The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer is 2.5 mol%, and the doping content of ZrSi2 is 3.0 mol%. The thickness of the oxygen barrier coating is 4000 μm; the specific steps are as follows:

[0111] Step 1: Prepare composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, mix them in a volume ratio of 7:5.5:7:3 to 7:6:7:3.5. Synthesize the powder body by low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa through a self-propagating furnace.

[0112] Step 2: Sinter the coating. Crush the powder block after self-propagating combustion synthesis, and add 40% of SiC according to the volume ratio for ball milling. The rotation speed of the ball mill is 350 r / min, and ball mill for 5 h. Put the composite powder into a plasma spark sintering mold with a diameter of 15 mm. The heating rate is 100°C / min, the sintering temperature is 1500°C, the holding time is 5 min, and the sintering pressure is 30 MPa.

[0113] Step 3: Film formation treatment of the bionic glass film. Mix the Zr-Y-O solid solution powder prepared by the above microwave preheating combustion synthesis with silica sol to form a colloid, brush the colloid on the surface of the coating, and dry it in a constant temperature drying oven at 50 °C for 30 s; place the composite coating in a high-temperature resistance furnace for film formation treatment, the heat treatment temperature is 1100 °C, and the heat treatment time is 100 min.

[0114] This comparative example provides a Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with bionic glass film for synergistic oxygen barrier. The phase structure of the glass film after heat treatment at 1100 °C for 100 min is as Figure 4 shown. It can be seen that after the film formation treatment, the surface is mainly composed of oxidation products ZrO2, ZrSiO4, Y2Si2O7, and unreacted ZrB2 and SiC. The diffraction peaks of each phase are sharp, showing good crystallinity. The surface morphology and cross-sectional morphology of the composite coating before oxidation are as Figure 6 shown. After heat treatment, oxygen is mainly distributed on the surface of the coating, and the oxygen content is lower closer to the carbon matrix. The surface morphology and cross-sectional morphology of the composite coating after oxidation at 1700 °C for 100 min are as Figure 7 shown. An obvious oxide layer appears, with a thickness of about 459 μm.

[0115] The results of the oxidation protection efficiency at 1700 °C are shown in Table 1. Figure 8 , Figure 9 respectively show the oxygen permeability curve and the cumulative protection efficiency of this coating during oxidation at 1700 °C for 100 min. The results show that in terms of oxidation protection efficiency, compared with Example 5, the oxygen barrier protection effect at 1700 °C is significantly inferior, indicating the advantage and necessity of the process with a film formation heat treatment temperature of 1200 °C and a film formation heat treatment time of 100 min in improving the oxidation protection effect of the coating in the present invention.

[0116] Comparative Example 2:

[0117] Using graphite as the substrate, an oxygen barrier coating composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating" is used, and the bionic film formation treatment is not adopted. The doping content of Y2O3 is 0.5 mol%, and the doping content of ZrSi2 is 1.0 mol%. The sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa. The film formation heat treatment temperature is 1200 °C, and the heat treatment time is 100 min.

[0118] In this comparative example, graphite was used as the substrate, and the oxygen barrier coating was composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating". The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer was 0.5 mol%, and the doping content of ZrSi2 was 1.0 mol%. The biomimetic film-forming treatment was not adopted, and the thickness of the oxygen barrier coating was 4000 μm. The specific steps are as follows:

[0119] Step 1: Prepare composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, they were mixed according to a volume ratio of 7:5.5:7:3 to 7:6:7:3.5. Through a self-propagating furnace, powder was synthesized by low-temperature exothermic combustion in an argon atmosphere with a pressure of 5 MPa.

[0120] Step 2: Sinter the coating. The powder block after self-propagating combustion synthesis was subjected to crushing treatment, and 40% of SiC was added according to the volume ratio for ball milling. The rotation speed of the ball mill was 350 r / min, and the ball milling time was 5 h. The composite powder was placed in a plasma spark sintering mold with a diameter of 15 mm. The heating rate was 100 °C / min, the sintering temperature was 1500 °C, the holding time was 5 min, and the sintering pressure was 30 MPa.

[0121] Step 3: Place the composite coating prepared in Step 2 in a high-temperature resistance furnace for film-forming treatment. The heat treatment temperature was 1200 °C, and the heat treatment time was 100 min.

[0122] This comparative example provides an oxygen barrier coating that does not adopt a biomimetic film-forming structure design, uses graphite as the substrate, and is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating". The oxidation protection efficiency results at 1700 °C are shown in Table 1. Figure 8 , Figure 9 The oxygen permeability curve and cumulative protection efficiency of this coating oxidized at 1700 °C for 100 min are respectively shown. The results show that compared with Example 5 in terms of oxidation protection efficiency, the oxygen barrier protection effect at 1700 °C is significantly inferior, indicating the advantages and necessity of using the matrix layer, self-growing glass layer structure, and biomimetic glass layer in this invention to improve the antioxidant protection effect of the oxygen barrier coating.

[0123] Comparative Example 3:

[0124] Using graphite as the substrate, the oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 is 4.0 mol, and the doping content of ZrSi2 is 4.5 mol%. The sintering temperature is 1500 °C, the holding time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1100 °C, and the heat treatment time is 100 min.

[0125] In this comparative example, graphite was used as the substrate, and an oxygen barrier coating was composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". The doping content of Y2O3 in the Y2O3-ZrSi2-ZrB2-SiC layer was 4.0 mol%, the doping content of ZrSi2 was 4.5 mol%, and the thickness of the oxygen barrier coating was 4000 μm. The specific steps are as follows:

[0126] Step 1: Preparation of composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and yttrium oxide prepared by the above microwave preheating combustion synthesis as raw materials, they were mixed in a volume ratio of 7:5.5:7:3 to 7:6:7:3.5. The powder was synthesized by low-temperature exothermic combustion in a self-propagating furnace under an argon atmosphere with a pressure of 5 MPa.

[0127] Step 2: Sintering of the coating. The powder block after self-propagating combustion synthesis was crushed, and 40% of SiC was added according to the volume ratio for ball milling. The rotation speed of the ball mill was 350 r / min, and the ball milling time was 5 h. The composite powder was placed in a plasma spark sintering mold with a diameter of 15 mm. The heating rate was 100 °C / min, the sintering temperature was 1500 °C, the holding time was 5 min, and the sintering pressure was 30 MPa.

[0128] Step 3: Film-forming treatment of the biomimetic glass film. The Zr-Y-O solid solution powder prepared by the above microwave preheating combustion synthesis was mixed with silica sol to form a colloid. The colloid was coated on the surface of the coating and dried in a constant temperature drying oven at 50 °C for 30 s. The composite coating was placed in a high-temperature resistance furnace for film-forming treatment. The heat treatment temperature was 1200 °C, and the heat treatment time was 100 min.

[0129] The results of the oxidation protection efficiency at 1700 °C are shown in Table 1. Figure 8 , Figure 9 The oxygen permeability curve and the cumulative protection efficiency of this coating oxidized at 1700 °C for 100 min are respectively shown. The results show that in terms of the oxidation protection efficiency, compared with Examples 1 to 7, the oxygen barrier protection effect at 1700 °C is significantly inferior, indicating the advantages and necessity of using a substrate layer, a self-growing glass layer structure, and a biomimetic glass layer in this invention to improve the antioxidant protection effect of the oxygen barrier coating.

[0130] Comparative Example 4:

[0131] Using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + commercially available Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". Among them, the doping content of commercially available Y2O3 is 3.0 mol%, and the doping content of ZrSi2 is 3.5 mol%. The sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa. The film-forming heat treatment temperature is 1100 °C, and the heat treatment time is 100 min.

[0132] In this comparative example, using graphite as the substrate, an oxygen barrier coating is composed of a "base layer + Y2O3-ZrSi2 modified ZrB2-SiC coating + biomimetic film-forming glass layer". In the Y2O3-ZrSi2-ZrB2-SiC layer, the doping content of commercially available Y2O3 is 3.0 mol%, and the doping content of ZrSi2 is 3.5 mol%. The thickness of the oxygen barrier coating is 4000 μm; the specific steps are as follows:

[0133] Step 1: Prepare composite powder by self-propagating combustion synthesis. Using zirconium powder, boron powder, silicon powder, and commercially available yttrium oxide as raw materials, mix them in a volume ratio of 7:5.5:7:3 to 7:6:7:3.5. Synthesize the powder by low-temperature exothermic combustion in a self-propagating furnace under an argon atmosphere with a pressure of 5 MPa.

[0134] Step 2: Sinter the coating. Crush the powder block after self-propagating combustion synthesis, and add 40% of SiC according to the volume ratio for ball milling. The rotation speed of the ball mill is 350 r / min, and ball mill for 5 h. Put the composite powder into a plasma spark sintering mold with a diameter of 15 mm. The heating rate is 100 °C / min, the sintering temperature is 1500 °C, the heat preservation time is 5 min, and the sintering pressure is 30 MPa.

[0135] Step 3: Film-forming treatment of the biomimetic glass film. Mix the Zr-Y-O solid solution powder prepared by microwave preheating combustion synthesis with silica sol to form a colloid. Brush the colloid on the surface of the coating and dry it in a constant temperature drying oven at 50 °C for 30 s; place the composite coating in a high-temperature resistance furnace for film-forming treatment. The heat treatment temperature is 1200 °C, and the heat treatment time is 100 min.

[0136] The oxidation protection efficiency results at 1700 °C are shown in Table 1. The results show that in terms of oxidation protection efficiency, compared with Examples 1-7, the oxygen barrier protection effect at 1700 °C is significantly inferior, indicating the advantage and necessity of using microwave preheating combustion synthesis to prepare Y2O3 in improving the antioxidant protection effect of the coating in the present invention.

[0137] Protection efficiency / % Example 1 99.705 Example 2 99.714 Example 3 99.724 Example 4 99.747 Example 5 99.789 Example 6 99.799 Example 7 99.809 Comparative Example 1 99.459 Comparative Example 2 99.078 Comparative Example 3 99.334 Comparative Example 4 99.223

[0138] Table 1 Results of the oxidation protection efficiency of the coating at 1700 °C

[0139] The above description of the present invention and its embodiments is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. In general, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural forms and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A Y2O3-ZrSi2-ZrB2-SiC composite ceramic coating based on low-energy self-exothermic technology combined with a bionic glass film for synergistic oxygen barrier, characterized in that: It includes a base layer, a transition layer, and a bionic glass layer; The base layer includes a graphite substrate material; The transition layer includes a multiphase Y2O3-ZrSi2-ZrB2-SiC coating; The bionic glass layer includes a Zr-Y-Si-O glass film; The base layer and the bionic glass layer are arranged at the innermost side and the outermost side respectively, and the transition layer is arranged between the base layer and the bionic glass layer.

2. The composite ceramic coating according to claim 1, characterized in that: The doping content of rare earth oxide Y2O3 in the transition layer is 0.5-3.5 mol%, the doping content of binary silicide ZrSi2 is 1-4.0 mol%, and the balance is ZrB2-SiC main phase ceramic.

3. The composite ceramic coating according to claim 1, wherein: The chemical composition of the transition layer is Y2O3-ZrSi2-ZrB2-SiC, and the thickness of the transition layer is 1000-4000 μm.

4. The composite ceramic coating according to claim 1, wherein: The thickness of the bionic glass layer is 500-1500 μm, and the surface of the bionic glass layer is composed of oxidation products ZrO2, ZrSiO4, Y2Si2O7 and incompletely reacted ZrB2 and SiC.

5. The composite ceramic coating according to claim 1, wherein: The Y2O3 powder synthesized by low-energy self-exothermic combustion has a grain size of 65-70nm, the grain size of the synthesized Zr-YO solid solution powder is 70-75nm, and ZrO2 is stabilized in a tetragonal crystal form by Y2O3.

6. The composite ceramic coating according to claim 1, wherein: When preparing self-propagating Y2O3-ZrSi2-ZrB2 powder, the raw materials are B powder, Zr powder, Si powder, and Y2O3 powder synthesized by low-energy self-exothermic synthesis. The preheating temperature of the self-propagating combustion synthesis furnace is 750-800℃, and a tungsten wire with a diameter of 1.5mm is used for ignition.

7. The composite ceramic coating according to claim 1, wherein: The Y2O3-ZrSi2-ZrB2-SiC coating was prepared by plasma spark sintering in a temperature range of 1450-1500°C, a heating rate of 50°C / min, and a sintering pressure of 30-35 MPa.

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