Method for preparing anti-ablation ZrB2-based ceramic for spaceflight through precursor conversion

Abstract

The invention discloses a method for preparing anti-ablation ZrB2-based ceramic for spaceflight through precursor conversion, and relates to the technical field of ceramic. The method comprises the following steps: stirring and mixing a ZrB2 organic precursor and a polyborosilazane precursor, carrying out cross-linking curing on the fully mixed precursor to obtain a precursor block, carrying out ball milling on the obtained block and reinforced phase ceramic powder, sieving, pressing the powder into a green body with a required shape at normal temperature, and sintering to obtain the ZrB2 / polyborosilazane composite ceramic material. And finally, cracking the green body to obtain a finished product, wherein the finished product does not need to be machined. According to the ZrB2-based ceramic prepared by the method, the forming difficulty and the cracking temperature of an intermediate green body can be reduced, the prepared ceramic is high in compactness, low in residual carbon content and uniform in reinforced phase dispersion, and the oxidation resistance and the ablation resistance of a ceramic material for spaceflight can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of ceramic technology, and specifically to a method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion. Background Technology

[0002] As spacecraft speeds continue to increase, their thermal protection systems and engine hot-end components face unprecedented challenges from extreme service environments. Traditional metallic materials are prone to creep and melting under ultra-high temperatures and complex atmospheres, leading to structural failure. While organic thermal protection materials offer insulation advantages, their low temperature limits cause rapid decomposition, carbonization, or even complete ablation at ultra-high temperatures. Neither of these materials can meet the reliability requirements of next-generation spacecraft. In contrast, ultra-high temperature ceramics are considered the most promising solution due to their superior thermal stability. ZrB2 ceramic, as the lowest density ultra-high temperature ceramic material, possesses an extremely high melting point, a low coefficient of thermal expansion, good corrosion resistance, and excellent ablation resistance, making it a promising candidate for application in the aerospace field.

[0003] Currently, the main methods for preparing ZrB2 ceramics include hot-pressing sintering, high-temperature self-propagating pyrolysis, microwave pyrolysis, and precursor conversion. Among these, precursor conversion involves converting organozirconium polymers into ceramic materials at high temperatures. This method requires low preparation temperatures and no additional pressure is needed during pyrolysis, resulting in ceramics with high molecular-scale uniformity and minimal grain coarsening. However, the application of ZrB2 ceramics still faces two major challenges: first, during ceramic preparation, precursor pyrolysis not only leads to the escape of small-molecule gases but also causes B2O3 volatilization at high temperatures, resulting in insufficient density in the prepared ZrB2 ceramics; second, during service, boron and residual carbon in the ceramic react with oxygen, causing mass loss and performance degradation. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, this invention provides a method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics through precursor conversion. This method utilizes a polyborosilicate precursor, which effectively improves the boron retention rate during the conversion of ZrB2 organic precursor ceramics, reduces byproduct content, and increases ceramic density. Furthermore, the incorporation of oxide and carbide ceramic powders effectively inhibits the abnormal growth of ZrB2 during pyrolysis and facilitates carbothermic reduction of residual carbon within the ceramic, optimizing the phase composition and microstructure of the ceramic material. Under service conditions, this results in a denser protective layer forming on the ceramic surface, further enhancing the mechanical properties and ablation resistance of the ceramic material.

[0005] The first objective of this invention is to provide a method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion, comprising the following steps: The ZrB2 organic precursor, the polyborosilicate precursor, and the crosslinking agent were dispersed in an organic solvent to obtain a precursor solution; The precursor solution was subjected to cross-linking and curing treatment to obtain the precursor bulk. The precursor bulk material is mechanically ground with oxide ceramic powder and carbide ceramic powder to obtain a mixed powder. The mixed powder is placed in a mold and pressed to obtain an intermediate preform; After pyrolysis of the intermediate preform, erosion-resistant ZrB2-based ceramics were obtained. Among them, the oxide ceramic powder is one or more of Sc2O3, Y2O3, and Lu2O3; the carbide ceramic powder is one or more of NbC, HfC, and TaC.

[0006] Preferably, the mass ratio of the ZrB2 organic precursor, the polyborosilicate precursor, and the crosslinking agent is (60~90):(8~25):(0.1~5):(5~20). The crosslinking agent is one or more of DVB, VPSO, and DCP; The organic solvent is one or more of ethanol, methanol, and acetone.

[0007] Preferably, the mass ratio of the precursor bulk to the oxide ceramic powder and the carbide ceramic powder is (75~90):(6~9):(1~7).

[0008] Preferably, the cross-linking curing process includes: The temperature is increased from room temperature to 55-65℃ at a rate of 4-5℃ / min and held for 0.5-1 h. Then, it is increased to 75-85℃ at a rate of 2-3℃ / min and held for 1.5-2.5 h. Next, it is increased to 100-120℃ at a rate of 2-3℃ / min and held for 0.5-1 h. Finally, it is increased to 140-160℃ at a rate of 2-3℃ / min and held for 0.5-1 h. The temperature is then allowed to cool freely to room temperature.

[0009] Preferably, the pyrolysis process includes: The temperature is increased from room temperature to 190-210℃ at a rate of 2-3℃ / min and held for 1-2 hours. Then, the temperature is increased to 700-900℃ at a rate of 2-3℃ / min and held for 2-6 hours. Subsequently, the temperature is increased to 1000-1400℃ at a rate of 2-3℃ / min and held for 4-6 hours. The temperature is then decreased to 500-600℃ at a rate of 3-4℃ / min and held for 10-20 minutes. The temperature is then slowly reduced to 180-220℃ and allowed to cool freely to room temperature. Ar is introduced as a protective gas during the pyrolysis process at a flow rate of 100-500 mL / min.

[0010] Preferably, the mechanical grinding process includes: ball milling the precursor block with oxide ceramic powder and carbide ceramic powder, and passing the ball-milled powder through a 1000-mesh sieve to obtain a mixed powder, wherein the ball milling speed is 200~400 r / min.

[0011] Preferably, the temperature for preparing the precursor solution is 50~80℃.

[0012] Preferably, the pressure application process involves placing the mold in a cold isostatic press at a pressure of 100~220MPa for 20min~50min.

[0013] The second objective of this invention is to provide an ablation-resistant ZrB2-based ceramic for aerospace applications.

[0014] The third objective of this invention is to provide an application of aerospace-grade ablation-resistant ZrB2-based ceramics in aerospace engines.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics through precursor conversion. The method involves mixing an organic ZrB2 precursor with a polyborosilicate precursor, cross-linking and solidifying the thoroughly mixed precursor to obtain a precursor bulk. This bulk is then ball-milled together with reinforcing ceramic powder, sieved, and pressed into a green body of the desired shape at room temperature. Finally, the green body is pyrolyzed, and the resulting product requires no further machining. The ZrB2-based ceramics prepared using this invention reduce the difficulty of intermediate green body forming and its pyrolysis temperature. The resulting ceramics exhibit high density, low residual carbon content, and uniform dispersion of the reinforcing phase, effectively improving the oxidation and ablation resistance of aerospace ceramic materials.

[0016] This invention, through component design and modification, endows ZrB2-based ceramics with a highly dense microstructure featuring a uniformly distributed dispersed phase, effectively suppressing abnormal grain growth at high temperatures and improving the material's density. This unique structure promotes the rapid formation of a dense, stable, and self-healing composite oxide protective layer on the material surface during ablation, efficiently blocking the inward diffusion of oxygen and reducing both the linear and mass ablation rates of the ceramic.

[0017] The addition of a polyborosilazane precursor in this invention enables the mixed precursor solution to form a more stable molecular network structure during cross-linking and curing. During the pyrolysis process, it can effectively inhibit the volatilization of boron in the form of B2O3, thereby promoting the carbothermic reduction reaction to proceed to the right, reducing the formation of ZrC and residual carbon, and increasing the content of ZrB2 in the final product.

[0018] This invention utilizes ultra-high melting point oxide ceramics to consume residual carbon generated by precursor pyrolysis, preventing material performance degradation due to carbon impurity oxidation. During subsequent ablation, the oxide ceramics can form a nanoscale coherent interface with the matrix oxidation products, providing significant strengthening effects by pinning dislocation migration and inhibiting grain boundary slip. Simultaneously, a continuous oxide film is induced on the material surface, constructing an efficient oxygen diffusion barrier, enabling the material to maintain excellent structural integrity and ablation resistance even in extreme thermo-chemical coupling environments.

[0019] The ultra-high temperature carbide ceramic provided by this invention has a high elastic modulus. When introduced into the ceramic material system as a reinforcing phase, it can cause the crack tip to deflect during the propagation process and consume the crack propagation energy through stress field redirection during service, thereby improving the mechanical strength and fracture toughness of the ceramic material. When oxygen atoms diffuse into the material interior along the crack, the ZrB2 ceramic and the carbide ceramic will form a borate glass with good fluidity and higher oxidation resistance temperature after oxidation. This glass dynamically fills the microcracks inside the ceramic, prevents further diffusion of oxygen atoms, and increases the crack propagation threshold stress of the material under service conditions.

[0020] This invention employs a pre-mixing method of multiple precursors, which can reduce the over-reliance on the development of high-cost novel precursors and allows for the flexible introduction of second-phase precursors according to the material's service environment, enabling rapid iterative optimization of the final ceramic material composition and significantly reducing R&D costs and time. Detailed Implementation

[0021] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments, but the embodiments are not intended to limit the present invention.

[0022] The purpose of this invention is to provide a method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion, in order to solve two major problems existing in the application of ZrB2 ceramics. First, during the ceramic preparation process, the pyrolysis of the precursor not only results in the escape of small molecule gases, but also in the volatilization of B2O3 at high temperatures, leading to insufficient density in the prepared ZrB2 ceramics. Second, during service, boron and residual carbon in the ceramics react with oxygen, causing mass loss and performance degradation.

[0023] To achieve the above objectives, the first aspect of the present invention provides a method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion, comprising the following steps: The ZrB2 organic precursor, the polyborosilicate precursor, and the crosslinking agent were dispersed in an organic solvent to obtain a precursor solution; The precursor solution was subjected to cross-linking and curing treatment to obtain the precursor bulk. The precursor bulk material is mechanically ground with oxide ceramic powder and carbide ceramic powder to obtain a mixed powder. The mixed powder is placed in a mold and pressed to obtain an intermediate preform; After pyrolysis of the intermediate preform, erosion-resistant ZrB2-based ceramics were obtained. Among them, the oxide ceramic powder is one or more of Sc2O3, Y2O3, and Lu2O3; the carbide ceramic powder is one or more of NbC, HfC, and TaC.

[0024] The mass ratio of the ZrB2 organic precursor, the polyborosilicate precursor, and the crosslinking agent is (60~90):(8~25):(0.1~5):(5~20). The crosslinking agent is one or more of DVB, VPSO, and DCP; The organic solvent is one or more of ethanol, methanol, and acetone.

[0025] The mass ratio of the precursor bulk to oxide ceramic powder and carbide ceramic powder is (75~90):(6~9):(1~7).

[0026] The cross-linking and curing process includes: The temperature is increased from room temperature to 55-65℃ at a rate of 4-5℃ / min and held for 0.5-1 h. Then, it is increased to 75-85℃ at a rate of 2-3℃ / min and held for 1.5-2.5 h. Next, it is increased to 100-120℃ at a rate of 2-3℃ / min and held for 0.5-1 h. Finally, it is increased to 140-160℃ at a rate of 2-3℃ / min and held for 0.5-1 h. The temperature is then allowed to cool freely to room temperature.

[0027] The pyrolysis process includes: The temperature is increased from room temperature to 190-210℃ at a rate of 2-3℃ / min and held for 1-2 hours. Then, the temperature is increased to 700-900℃ at a rate of 2-3℃ / min and held for 2-6 hours. Subsequently, the temperature is increased to 1000-1400℃ at a rate of 2-3℃ / min and held for 4-6 hours. The temperature is then decreased to 500-600℃ at a rate of 3-4℃ / min and held for 10-20 minutes. The temperature is then slowly reduced to 180-220℃ and allowed to cool freely to room temperature. Ar is introduced as a protective gas during the pyrolysis process at a flow rate of 100-500 mL / min.

[0028] The mechanical grinding process includes: ball milling the precursor block with oxide ceramic powder and carbide ceramic powder, and passing the ball-milled powder through a 1000-mesh sieve to obtain a mixed powder, wherein the ball milling speed is 200~400 r / min.

[0029] The temperature for preparing the precursor solution is 50~80℃.

[0030] The pressure application process involves placing the mold in a cold isostatic press at a pressure of 100~220MPa and holding the pressure for 20min~50min.

[0031] The addition of a polyborosilazane precursor in this invention enables the mixed precursor solution to form a more stable molecular network structure during cross-linking and curing. During the pyrolysis process, it can effectively inhibit the volatilization of boron in the form of B2O3, thereby promoting the carbothermic reduction reaction to proceed to the right, reducing the formation of ZrC and residual carbon, and increasing the content of ZrB2 in the final product.

[0032] An exemplary method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion includes: S1: The precursor solution is composed of ZrB2 organic precursor, polyborosilicate precursor, crosslinking agent, and solvent. The mass ratio of ZrB2 organic precursor, polyborosilicate precursor, and crosslinking agent is (60~90):(8~25):(0.1~5):(5~20). The crosslinking agent is one of DVB, VPSO, and DCP, and the solvent is one of ethanol, methanol, and acetone. The precursor solution mixing process involves placing the solution in a water bath and stirring for 40 to 120 minutes at a temperature of 50°C to 80°C.

[0033] S2: Place the mixed precursor solution in an oven for cross-linking and curing treatment to obtain precursor blocks; The crosslinking curing temperature curve is as follows: from room temperature, the temperature is increased to 60℃ at 4℃ / min and held for 0.5 h to 1 h; then increased to 80℃ at 2℃ / min and held for 1.5 h to 2.5 h; then increased to 110℃ at 2℃ / min and held for 0.5 h to 1 h; then increased to 150℃ at 2℃ / min and held for 0.5 h to 1 h; and finally allowed to cool freely to room temperature.

[0034] S3: The precursor block obtained in step S2 is ball-milled with oxide ceramic powder and carbide ceramic powder. The mass ratio of precursor block, oxide ceramic powder and carbide ceramic powder is (75~90):(6~9):(1~7). The oxide ceramic powder is one of Sc2O3, Y2O3 and Lu2O3, and the carbide ceramic powder is one of NbC, HfC and TaC. The ball milling speed is 200~400 r / min. Adding polyborosilicate precursor can make the mixed precursor solution form a more stable molecular network structure during crosslinking and curing.

[0035] S4: The powder after ball milling in step S3 is screened through a 1000-mesh sieve; S5: Pour the powder obtained in step S4 into a mold for cold pressing to obtain an intermediate blank; Place the mold in a cold isostatic press with a pressure of 100~220MPa and hold for 20min~50min.

[0036] S6: The billet obtained in step S5 is subjected to pyrolysis treatment to obtain the final product. The billet is placed in a pyrolysis furnace, and the pyrolysis temperature curve is as follows: the temperature is increased from room temperature to 200℃ at 2℃ / min and held for 1 h to 2 h; then increased to 800℃ at 2℃ / min and held for 2 h to 6 h; then increased to 1000~1400℃ at 2℃ / min and held for 4 h to 6 h; then decreased to 600℃ at 3℃ / min and held for 10 min to 20 min; after a slow cooling rate to 200℃, the temperature is allowed to cool freely to room temperature; Ar is introduced as a protective gas during the pyrolysis process, and the Ar flow rate is 100~500 mL / min. During the pyrolysis process, the volatilization of boron in the form of B2O3 can be effectively suppressed, thereby promoting the carbothermic reduction reaction to the right, reducing the formation of ZrC and residual carbon, and increasing the content of ZrB2 in the final product.

[0037] A second aspect of this invention provides an ablation-resistant ZrB2-based ceramic for aerospace applications. This ceramic has advantages such as high density, low byproduct content, high extreme temperature stability, and good resistance to ablation and oxidation.

[0038] The third aspect of this invention provides the application of aerospace-grade ablation-resistant ZrB2-based ceramics in aerospace engines.

[0039] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0040] Example 1 The precursor solution consisted of ZrB2 organic precursor, polyborosilazane precursor, DVB, and ethanol in a mass ratio of 75:20:0.5:10. The precursor solution was stirred in a water bath at 60°C for 90 min. The mixed solution was then placed in an oven, and the curing temperature profile was as follows: increasing the temperature from room temperature to 60°C at 4°C / min and holding for 1 h; increasing it to 80°C at 2°C / min and holding for 2 h; increasing it to 110°C at 2°C / min and holding for 1 h; increasing it to 150°C at 2°C / min and holding for 0.5 h; and then allowing it to cool freely to room temperature. Subsequently, the precursor bulk, Y2O3, and TaC were mixed and ball-milled at a mass ratio of 80:6:5 at 220 r / min. After ball milling, the mixture was sieved through a 1000-mesh sieve. The sieved powder was poured into a mold and pressed using a cold isostatic press at a pressure of 150 MPa for 30 min. The pressed billet was placed in a pyrolysis furnace for pyrolysis. The pyrolysis temperature curve was as follows: the temperature was increased from room temperature to 200℃ at a rate of 2℃ / min and held for 2 hours; then increased to 800℃ at a rate of 2℃ / min and held for 3 hours; then increased to 1200℃ at a rate of 2℃ / min and held for 5 hours; then decreased to 600℃ at a rate of 3℃ / min and held for 10 minutes; after the temperature was slowly reduced to 200℃, it was allowed to cool freely to room temperature. Ar was introduced as a protective gas throughout the process, with a flow rate of 150 mL / min. The final product was obtained after the product was removed.

[0041] The ZrB2-based ceramic obtained in Example 1 has a density of 98.3% and a fracture toughness of 5.3 MPa·m. 1 / 2 Heat flux density 4.18 MW / m 2 The linear ablation rate measured after 60 s of ablation was 0.09 μm / s, and the mass ablation rate was 0.037 mg / s.

[0042] Example 2 The precursor solution consisted of ZrB2 organic precursor, polyborosilazane precursor, DVB, and ethanol in a mass ratio of 85:15:0.8:10. The precursor solution was stirred in a water bath at 60℃ for 110 min. The mixed solution was then placed in an oven, and the curing temperature profile was as follows: increasing the temperature from room temperature to 60℃ at 4℃ / min and holding for 1 h; increasing it to 80℃ at 2℃ / min and holding for 2 h; increasing it to 110℃ at 2℃ / min and holding for 1 h; increasing it to 150℃ at 2℃ / min and holding for 0.5 h; and then allowing it to cool freely to room temperature. Subsequently, the precursor bulk, Sc2O3, and NbC were mixed and ball-milled at a mass ratio of 90:8:3 at 220 r / min. After ball milling, the mixture was sieved through a 1000-mesh sieve. The sieved powder was poured into a mold and pressed using a cold isostatic press at a pressure of 150 MPa for 30 min. The pressed billet was placed in a pyrolysis furnace for pyrolysis. The pyrolysis temperature curve was as follows: the temperature was increased from room temperature to 200℃ at a rate of 2℃ / min and held for 2 hours; then increased to 800℃ at a rate of 2℃ / min and held for 5 hours; then increased to 1350℃ at a rate of 2℃ / min and held for 5 hours; then decreased to 600℃ at a rate of 3℃ / min and held for 10 minutes; then decreased slowly to 200℃ and allowed to cool freely to room temperature. Ar was introduced as a protective gas throughout the process, with a flow rate of 150 mL / min. The final product was obtained after the product was removed.

[0043] The ZrB2-based ceramic obtained in Example 2 has a density of 96.8% and a fracture toughness of 4.6 MPa·m. 1 / 2 Heat flux density 4.18 MW / m 2 The linear ablation rate measured after 60 s of ablation was 0.26 μm / s, and the mass ablation rate was 0.11 mg / s.

[0044] Comparative Example 1 The precursor solution consisted of ZrB2 organic precursor, DVB, and ethanol in a mass ratio of 75:0.5:10. The precursor solution was stirred in a water bath at 60°C for 90 min. The mixed solution was then placed in an oven, and the curing temperature profile was as follows: temperature increased from room temperature to 60°C at 4°C / min and held for 1 h; then increased to 80°C at 2°C / min and held for 2 h; then increased to 110°C at 2°C / min and held for 1 h; finally increased to 150°C at 2°C / min and held for 0.5 h, followed by free cooling to room temperature. Subsequently, the precursor bulk, Y2O3, and TaC were mixed and ball-milled at a mass ratio of 80:6:5 at 220 r / min. The ball-milled powder was then sieved through a 1000-mesh sieve. The sieved powder was poured into a mold and pressed using a cold isostatic press at 150 MPa for 30 min. The pressed billet was placed in a pyrolysis furnace for pyrolysis. The pyrolysis temperature curve was as follows: the temperature was increased from room temperature to 200℃ at a rate of 2℃ / min and held for 2 hours; then increased to 800℃ at a rate of 2℃ / min and held for 3 hours; then increased to 1200℃ at a rate of 2℃ / min and held for 5 hours; then decreased to 600℃ at a rate of 3℃ / min and held for 10 minutes; after the temperature was slowly reduced to 200℃, it was allowed to cool freely to room temperature. Ar was introduced as a protective gas throughout the process, with a flow rate of 150 mL / min. The final product was obtained after the product was removed.

[0045] The ZrB2-based ceramic obtained in Comparative Example 1 had a density of 84.3% and a fracture toughness of 2.7 MPa·m. 1 / 2 Heat flux density 4.18 MW / m 2 The linear ablation rate measured after 60 s of ablation was 15.6 μm / s, and the mass ablation rate was 3.52 mg / s.

[0046] Comparative Example 2 The precursor solution consisted of ZrB2 organic precursor, polyborosilazane precursor, DVB, and ethanol in a mass ratio of 85:15:0.8:10. The precursor solution was stirred in a water bath at 60℃ for 110 min. The mixed solution was then placed in an oven, and the curing temperature profile was as follows: increasing the temperature from room temperature to 60℃ at 4℃ / min and holding for 1 h; increasing it to 80℃ at 2℃ / min and holding for 2 h; increasing it to 110℃ at 2℃ / min and holding for 1 h; increasing it to 150℃ at 2℃ / min and holding for 0.5 h; and then allowing it to cool freely to room temperature. The precursor block was then ball-milled at 220 rpm. After ball milling, the powder was sieved through a 1000-mesh sieve. The sieved powder was poured into a mold and pressed using a cold isostatic press at 150 MPa for 30 min. The pressed billet was placed in a pyrolysis furnace for pyrolysis. The pyrolysis temperature curve was as follows: the temperature was increased from room temperature to 200℃ at a rate of 2℃ / min and held for 2 hours; then increased to 800℃ at a rate of 2℃ / min and held for 5 hours; then increased to 1350℃ at a rate of 2℃ / min and held for 5 hours; then decreased to 600℃ at a rate of 3℃ / min and held for 10 minutes; then decreased slowly to 200℃ and allowed to cool freely to room temperature. Ar was introduced as a protective gas throughout the process, with a flow rate of 150 mL / min. The final product was obtained after the product was removed.

[0047] The ZrB2-based ceramic obtained in Comparative Example 2 had a density of 92.6% and a fracture toughness of 3.5 MPa·m. 1 / 2 Heat flux density 4.18 MW / m 2 The linear ablation rate measured after 60 s of ablation was 8.3 μm / s, and the mass ablation rate was 1.94 mg / s.

[0048] It should be noted that Comparative Example 1, lacking the introduction of the polyborosilicate precursor, significantly hindered the ceramic densification process. The polyborosilicate precursor not only acts as an effective molding aid during pressing and pyrolysis but also effectively suppresses the volatilization loss of boron. Without this component, the strong covalent bonds of ZrB2 and the volatilization of boron in gaseous form both lead to a decrease in the density of the final ceramic product and an increase in byproducts. In a high-temperature ablation environment, residual pores become channels for oxygen penetration, accelerating the oxidation and volatilization of the ZrB2 component. Simultaneously, the material surface cannot form a complete protective layer, resulting in decreased ablation performance.

[0049] Although Comparative Example 2 retained the polyborosilicate precursor, ensuring the basic formability and boron retention of the ceramic, the lack of oxide and carbide powders resulted in less than ideal overall performance. Oxide and carbide powders, acting as a rigid framework, can suppress excessive shrinkage and grain growth of the matrix at high temperatures, ensuring dimensional stability. Furthermore, during ablation, the composite glassy phase generated through multi-component oxidation reactions can form a dense and continuous coating layer on the material surface, effectively blocking oxygen diffusion. Without these components, the density of the formed ceramic decreases, the surface oxide layer thickness is insufficient, the oxygen diffusion rate increases, and the ablation rate correspondingly increases.

[0050] In summary, the polyborosilicate precursor is the key functional phase for achieving high densification, while the oxide and carbide powders enhance ablation resistance through microstructure regulation and surface protective layer optimization. The synergistic effect of both is indispensable.

[0051] This invention describes preferred embodiments and their effects. However, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to include both the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion, characterized in that, Includes the following steps: The ZrB2 organic precursor, the polyborosilicate precursor, and the crosslinking agent were dispersed in an organic solvent to obtain a precursor solution; The precursor solution was subjected to cross-linking and curing treatment to obtain the precursor bulk. The precursor bulk material is mechanically ground with oxide ceramic powder and carbide ceramic powder to obtain a mixed powder. The mixed powder is placed in a mold and pressed to obtain an intermediate preform; After pyrolysis of the intermediate preform, erosion-resistant ZrB2-based ceramics were obtained. Among them, the oxide ceramic powder is one or more of Sc2O3, Y2O3, and Lu2O3; the carbide ceramic powder is one or more of NbC, HfC, and TaC.

2. The method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion according to claim 1, characterized in that, The mass ratio of the ZrB2 organic precursor, the polyborosilicate precursor, and the crosslinking agent is (60~90):(8~25):(0.1~5):(5~20). The crosslinking agent is one or more of DVB, VPSO, and DCP; The organic solvent is one or more of ethanol, methanol, and acetone.

3. The method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion according to claim 1, characterized in that, The mass ratio of the precursor bulk to oxide ceramic powder and carbide ceramic powder is (75~90):(6~9):(1~7).

4. The method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion according to claim 1, characterized in that, The cross-linking and curing process includes: The temperature is increased from room temperature to 55-65℃ at a rate of 4-5℃ / min and held for 0.5-1 h. Then, it is increased to 75-85℃ at a rate of 2-3℃ / min and held for 1.5-2.5 h. Next, it is increased to 100-120℃ at a rate of 2-3℃ / min and held for 0.5-1 h. Finally, it is increased to 140-160℃ at a rate of 2-3℃ / min and held for 0.5-1 h. The temperature is then allowed to cool freely to room temperature.

5. The method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion according to claim 1, characterized in that, The pyrolysis process includes: The temperature is increased from room temperature to 190-210℃ at a rate of 2-3℃ / min and held for 1-2 hours. Then, the temperature is increased to 700-900℃ at a rate of 2-3℃ / min and held for 2-6 hours. Subsequently, the temperature is increased to 1000-1400℃ at a rate of 2-3℃ / min and held for 4-6 hours. The temperature is then decreased to 500-600℃ at a rate of 3-4℃ / min and held for 10-20 minutes. The temperature is then slowly reduced to 180-220℃ and allowed to cool freely to room temperature. Ar is introduced as a protective gas during the pyrolysis process at a flow rate of 100-500 mL / min.

6. The method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion according to claim 1, characterized in that, The mechanical grinding process includes: ball milling the precursor block with oxide ceramic powder and carbide ceramic powder, and passing the ball-milled powder through a 1000-mesh sieve to obtain a mixed powder, wherein the ball milling speed is 200~400 r / min.

7. The method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion according to claim 1, characterized in that, The temperature for preparing the precursor solution is 50~80℃.

8. The method for preparing aerospace-grade ablation-resistant ZrB2-based ceramics by precursor conversion according to claim 1, characterized in that, The pressure application process involves placing the mold in a cold isostatic press at a pressure of 100~220MPa and holding the pressure for 20min~50min.

9. An aerospace-grade ablation-resistant ZrB2-based ceramic prepared by the method described in any one of claims 1 to 8.

10. The application of the ablation-resistant ZrB2-based ceramic of claim 9 in aerospace engines.