A method for preparing high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications

Abstract

This invention discloses a method for preparing high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications. First, atomic W is coated onto the surface of SiC powder using hexacarbonyl W and chemical vapor deposition. Then, the W-coated SiC powder and ZrB2 powder are mixed using electromagnetic stirring to obtain ultra-high temperature ceramic powder. Finally, SPS technology is used to densify the ZrB2-SiC ultra-high temperature ceramic. The ZrB2-SiC ultra-high temperature ceramic prepared by this invention possesses a structural characteristic that balances high density and fine grain size, exhibiting high fracture toughness and excellent high-temperature oxidation resistance, and has broad application prospects in the aerospace field.

Description

Technical Field

[0001] This invention relates to the field of ultra-high temperature ceramic composite materials technology, specifically a method for preparing high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications. The ZrB2-SiC ceramic material prepared using this method can achieve high density and fine grains, exhibiting high fracture toughness and excellent high-temperature oxidation resistance, and has broad application prospects in the field of aerospace materials. Background Technology

[0002] With the rapid development and leapfrog progress of aerospace technology, hypersonic vehicles, high-speed reentry vehicles, and reusable transatmospheric vehicles have become research hotspots for various countries. Their hypersonic speed, long-duration flight, and reusable service characteristics place higher demands on the high-temperature resistance, high-temperature oxidation resistance, and toughening properties of heat-resistant materials. Therefore, developing ultra-high-temperature thermal protection materials with excellent mechanical properties and high-temperature oxidation resistance has become a crucial technical problem that urgently needs to be solved for new spacecraft.

[0003] ZrB2-SiC ceramics possess high thermal conductivity, a suitable coefficient of thermal expansion, and good ablation resistance, making them the primary material for current ultra-high temperature ceramic material research. However, due to the significant difference in the coefficients of thermal expansion between ZrB2 and SiC, large thermal stresses can occur during drastic temperature changes, inducing the formation of microcracks. ZrB2 and SiC nanopowders are prone to agglomeration, affecting grain growth behavior during sintering, leading to irregular grain growth and deteriorating mechanical properties and oxidation resistance. Above 1400℃, the density of the silica oxide layer decreases, resulting in insufficient oxidation resistance of ZrB2-SiC ceramics. Therefore, reducing the agglomeration degree and thermal stress concentration of ZrB2 and SiC powders, improving the oxide layer structure and density, and enhancing toughness and oxidation resistance are crucial for developing high-performance ultra-high temperature ceramic materials.

[0004] Refractory metal W possesses excellent ductility, making it an ideal sintering aid for high-temperature materials. As a sintering aid, refractory metal W offers the following advantages: it effectively alleviates thermal stress; its excellent high-temperature resistance and high melting point ensure that the service temperature of ultra-high-temperature ceramic composites remains unaffected; and it improves the oxide layer structure, forming a tungsten oxide-silica composite protective layer and enhancing the density of the oxide layer above 1400℃. However, using refractory metal W as a sintering aid presents the following technical challenges: the high melting point of refractory metals only achieves good densification behavior at relatively high sintering temperatures, leading to grain coarsening in the sintered ceramic material. This creates a conflict between densification and grain refinement, degrading its performance. Furthermore, metal powders are prone to sintering and agglomeration, forming large-sized metal-rich phases in the ceramic matrix, reducing the toughness and strength of the ceramic.

[0005] This invention addresses the need for high-performance ultra-high temperature thermal protection materials for aerospace vehicles. To solve the problems of sintering grain growth and thermal stress concentration in ZrB2-SiC ultra-high temperature ceramics, an innovative preparation technique is designed: utilizing atomic-scale W assembly technology on the ceramic powder surface, a highly active interface of the ceramic powder is constructed, improving the sintering interface of the ultra-high temperature ceramic, avoiding the agglomeration of ZrB2, SiC ceramics, and W metal, achieving a unified process of densification and fine grains, thus preparing high-performance ZrB2-SiC ultra-high temperature ceramics. Specifically, the mechanism is as follows: atomic-scale W can effectively lower the sintering melting point of the metal; high surface / interface activity not only effectively removes oxygen contamination from the ceramic powder surface but also accelerates element transfer and diffusion between the metal and ceramic, lowering the liquid phase formation temperature; the low-temperature passivation layer on the carbonyl metal surface after coating can reduce the binding free energy of powder agglomeration. The ZrB2-SiC ultra-high temperature ceramic prepared by this invention simultaneously achieves high density and fine grains in its structure, exhibiting high fracture toughness and high-temperature oxidation resistance, and has significant application value in the field of aerospace materials. Summary of the Invention

[0006] This invention provides a method for preparing high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications, which solves the technical problem of conflict between densification and grain refinement in ZrB2-SiC ultra-high temperature ceramics. The prepared material has excellent mechanical and oxidation resistance properties.

[0007] This invention is implemented as follows:

[0008] 1) Atomic W coating SiC

[0009] Using hexacarbonyl W powder as a precursor, atomic W was coated onto the surface of SiC ceramic powder by chemical vapor deposition to obtain SiC ceramic powder coated with atomic W.

[0010] 2) Electromagnetic stirring for powder mixing

[0011] SiC ceramic powder coated with atomic W and ZrB2 ceramic powder were weighed separately. The two powders were first placed in an ethanol solution and electromagnetically stirred to obtain a mixed slurry. The mixed slurry was then rotary evaporated under vacuum to obtain a dry mixed powder. Finally, the dry mixed powder was sieved to obtain a composite ceramic powder product with fine particle size and uniform mixing.

[0012] 3) SPS sintering

[0013] The composite ceramic powder product obtained in step 2) is loaded into a graphite mold and placed in an SPS discharge plasma sintering furnace for sintering under vacuum. After sintering, it is cooled to room temperature with the furnace to obtain high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications.

[0014] By coating SiC ceramic powder with atomic-state W, the surface passivation layer of the atomic-state W coating structure reduces the binding free energy of powder agglomeration, thus preventing agglomeration of ball-milled ceramic powder. Atomic-state W improves the surface / interfacial activity between SiC and ZrB2, removes the oxide layer on the ceramic powder surface, lowers the sintering temperature, promotes the densification reaction during sintering, inhibits the growth of sintered crystal grains, and prevents W sintering agglomeration. W element reduces the thermal stress between SiC and ZrB2, increasing the viscosity and density of the oxide layer. Electromagnetic stirring is used to mix the powder, achieving uniform mixing while preserving the atomic-state W-coated SiC structure. Rapid densification is achieved using SPS sintering. Through the coupling of these advantages, a ZrB2-SiC ultra-high temperature ceramic with high fracture toughness and high-temperature oxidation resistance is obtained.

[0015] As a further preferred embodiment, the particle size of the SiC ceramic powder is 400-700 nm, and the particle size of the ZrB2 ceramic powder is 200-500 nm.

[0016] As a further preferred embodiment, the volume percentage of the atomic W-coated SiC ceramic powder to the total volume of the atomic W-coated SiC ceramic powder and ZrB2 ceramic powder is (15-25)%, and the volume percentage of the ZrB2 ceramic powder to the total volume of the atomic W-coated SiC ceramic powder and ZrB2 ceramic powder is (75-85)%.

[0017] As a further preferred embodiment, the electromagnetic stirring process is as follows: a 99% ethanol solution is used as the medium, the mass ratio of solution to powder is 8-12:1, and the electromagnetic stirring time is 5-10 hours; the sieve is 150-250 mesh.

[0018] As a further preferred embodiment, the SPS sintering process has a vacuum degree of 1×10⁻⁶. -4 ~1×10 -3 The heating rate is 100–200℃ / min, the sintering temperature is 1900–2100℃, the holding time is 4–6 min, and the sintering pressure is 30–50 MPa.

[0019] The beneficial effects of this invention are as follows: The ZrB2-SiC ultra-high temperature ceramic prepared by this invention exhibits uniform distribution of ZrB2 and SiC without significant agglomeration, and W is also uniformly distributed; it achieves a balance between high density and fine grain size, with a grain size of 0.5–2 μm and a density >98.3%; it also possesses high fracture toughness and excellent high-temperature oxidation resistance, with a fracture toughness >7.1 MPa·m. 1 / 2 The oxidative weight gain after oxidation at 1500℃ for 2 hours was <5.7 mg / cm³. 2 The process is simple and suitable for large-scale production. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of using hexacarbonyl tungsten to achieve atomic-state W coating of SiC ceramic powder.

[0021] Figure 2 The microstructure of the high-performance ZrB2 (80 Vol.%)-atomic W-coated SiC (20 Vol.%) ultra-high temperature ceramic for aerospace applications prepared in Example 1 is shown.

[0022] Figure 3 The microstructure of the high-performance ZrB2 (85 Vol.%)-atomic W-coated SiC (15 Vol.%) ultra-high temperature ceramic for aerospace applications prepared in Example 2 is shown.

[0023] Figure 4 The microstructure of the high-performance ZrB2 (75 Vol.%)-atomic W-coated SiC (25 Vol.%) ultra-high temperature ceramic for aerospace applications prepared in Example 3 is shown.

[0024] Figure 5 The oxide layer microstructure and EDS surface scan results of the ZrB2 (80 Vol.%)-SiC (20 Vol.%) ultra-high temperature ceramic prepared in Example 1 are shown.

[0025] Figure 6 The oxide layer microstructure and EDS surface scan results of the high-performance ZrB2 (80 Vol.%)-atom W coated SiC (20 Vol.%) ultra-high temperature ceramic for aerospace prepared in Comparative Example 1 are shown.

[0026] Figure 7 This is a schematic diagram of the technical principle of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] Preparation method of high-performance ZrB2 (80 vol.%)-atomic W-coated SiC (20 vol.%) ultra-high temperature ceramics for aerospace applications:

[0030] 1) Atomic W coating SiC

[0031] Using hexacarbonyl W powder as a precursor, atomic W was coated onto the surface of SiC ceramic powder with a particle size of 400–700 nm using chemical vapor deposition. The SiC ceramic powder was placed in a vibrating pyrolysis coating furnace; the hexacarbonyl W was placed in an evaporator heated to 100°C; nitrogen gas was introduced into the evaporator, and the carrier gas and carbonyl W gas entered the vibrating pyrolysis coating furnace together; the vibrating pyrolysis coating furnace was heated to 400°C, and the carbonyl W gas thermally decomposed, coating the surface of the SiC ceramic powder with atomic W, thus obtaining SiC ceramic powder coated with atomic W.

[0032] 2) Electromagnetic stirring for powder mixing

[0033] Weigh out 80 vol.% ZrB2 powder and 20 vol.% SiC powder coated with atomic W. The particle size of the ZrB2 ceramic powder is 200-500 nm. First, put the two powders into an ethanol solution and stir electromagnetically. The mass ratio of solution to powder is 10:1 to obtain a mixed slurry. Then, the mixed slurry is rotary evaporated under vacuum with pure water as the condensing medium. The electromagnetic stirring time is 8 hours to obtain a dry mixed powder. Finally, the dry mixed powder is sieved through a 200-mesh sieve to obtain a composite ceramic powder product with fine particle size and uniform mixing.

[0034] 3) SPS sintering

[0035] The composite ceramic powder product obtained in step 2) is loaded into a graphite mold and placed in an SPS discharge plasma sintering furnace at 5×10⁻⁶ ℃. -4 Sintering was carried out under vacuum conditions, with a heating rate of 150℃ / min, a sintering temperature of 2000℃, a holding time of 5min, and a sintering pressure of 40MPa. After sintering, the furnace was cooled to room temperature to obtain high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications.

[0036] See appendix Figure 2 The microstructure analysis of the ZrB2 (80 vol.%)-atomic W-coated SiC (20 vol.%) ultra-high temperature ceramic obtained in this embodiment showed that the material has a dense microstructure, with ZrB2 and SiC uniformly distributed without obvious agglomeration, and W uniformly distributed. The average grain size was statistically analyzed using Image Pro Plus software, and the ZrB2 grain size was 0.5–2 μm. The density of the ceramic material was measured using the Archimedes displacement method, and the density of the prepared ultra-high temperature ceramic was 98.7%.

[0037] Example 2

[0038] Preparation method of high-performance ZrB2 (85 Vol.%)-atomic W-coated SiC (15 Vol.%) ultra-high temperature ceramics for aerospace applications:

[0039] 1) Atomic W coating SiC

[0040] Using hexacarbonyl W powder as a precursor, atomic W was coated onto the surface of SiC ceramic powder with a particle size of 400–700 nm via chemical vapor deposition, resulting in SiC ceramic powder coated with atomic W. The SiC ceramic powder was then placed in a vibrating pyrolysis coating furnace. The hexacarbonyl W was placed in an evaporator, which was heated to 90°C. Nitrogen gas was introduced into the evaporator, and the carrier gas and carbonyl W gas entered the vibrating pyrolysis coating furnace together. The vibrating pyrolysis coating furnace was heated to 450°C, and the carbonyl W gas thermally decomposed, coating the surface of the SiC ceramic powder with atomic W, resulting in SiC ceramic powder coated with atomic W.

[0041] 2) Electromagnetic stirring for powder mixing

[0042] Weigh out 85 vol.% ZrB2 powder and 15 vol.% SiC powder coated with atomic W. The particle size of the ZrB2 ceramic powder is 200-500 nm. First, put the two powders into an ethanol solution and stir electromagnetically. The mass ratio of solution to powder is 8:1 to obtain a mixed slurry. Then, the mixed slurry is rotary evaporated under vacuum with pure water as the condensing medium. The electromagnetic stirring time is 5 h to obtain a dry mixed powder. Finally, the dry mixed powder is sieved through a 250 mesh sieve to obtain a composite ceramic powder product with fine particle size and uniform mixing.

[0043] 3) SPS sintering

[0044] The composite ceramic powder product obtained in step 2) is loaded into a graphite mold and placed in an SPS discharge plasma sintering furnace at a temperature of 1×10⁻⁶. -4 Sintering was carried out under vacuum conditions, with a heating rate of 200℃ / min, a sintering temperature of 2100℃, a holding time of 4min, and a sintering pressure of 30MPa. After sintering, the furnace was cooled to room temperature to obtain high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications.

[0045] See appendix Figure 3 The microstructure of the ZrB2 (85 vol.%)-atomic W-coated SiC (15 vol.%) ultra-high temperature ceramic obtained in this embodiment was analyzed. It can be seen that the material has a dense microstructure, with ZrB2 and SiC uniformly distributed without obvious agglomeration, and W uniformly distributed. The average grain size was statistically analyzed using Image Pro Plus software, and the ZrB2 grain size was 0.5-2 μm. The density of the ceramic material was measured using the Archimedes displacement method, and the density of the prepared ultra-high temperature ceramic was 98.3%.

[0046] Example 3

[0047] Preparation method of high-performance ZrB2 (75 Vol.%)-atomic W-coated SiC (25 Vol.%) ultra-high temperature ceramics for aerospace applications:

[0048] 1) Atomic tungsten coated SiC

[0049] Using hexacarbonyl W powder as a precursor, atomic W was coated onto the surface of SiC ceramic powder with a particle size of 400–700 nm via chemical vapor deposition, resulting in SiC ceramic powder coated with atomic W. The SiC ceramic powder was then placed in a vibrating pyrolysis coating furnace. The hexacarbonyl W was placed in an evaporator, which was heated to 100°C. Nitrogen gas was introduced into the evaporator, and the carrier gas and carbonyl W gas entered the vibrating pyrolysis coating furnace together. The vibrating pyrolysis coating furnace was heated to 380°C, and the carbonyl W gas thermally decomposed, coating the surface of the SiC ceramic powder with atomic W, resulting in SiC ceramic powder coated with atomic W.

[0050] 2) Electromagnetic stirring for powder mixing

[0051] Weigh out 75 vol.% ZrB2 powder and 25 vol.% hexacarbonyl W-coated SiC powder. The particle size of the ZrB2 ceramic powder is 200-500 nm. First, put the two powders into an ethanol solution and stir electromagnetically. The mass ratio of solution to powder is 12:1 to obtain a mixed slurry. Then, the mixed slurry is rotary evaporated under vacuum with pure water as the condensing medium. The electromagnetic stirring time is 10 h to obtain a dry mixed powder. Finally, the dry mixed powder is sieved through a 150-mesh sieve to obtain a fine-particle-size, uniformly mixed composite ceramic powder product.

[0052] 3) SPS sintering

[0053] The composite ceramic powder product obtained in step 2) is loaded into a graphite mold and placed in an SPS discharge plasma sintering furnace at a temperature of 1×10⁻⁶. -3 Sintering was carried out under vacuum conditions, with a heating rate of 100℃ / min, a sintering temperature of 1900℃, a holding time of 6min, and a sintering pressure of 50MPa. After sintering, the furnace was cooled to room temperature to obtain high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications.

[0054] See appendix Figure 4The microstructure of the ZrB2 (75 Vol.%)-atomic W-coated SiC (25 Vol.%) ultra-high temperature ceramic obtained in this embodiment was analyzed. The material has a dense microstructure, with ZrB2 and SiC uniformly distributed without obvious agglomeration, and W uniformly distributed. The average grain size was statistically analyzed using Image Pro Plus software, and the ZrB2 grain size was 0.5–2 μm. The density of the ceramic material was measured using the Archimedes displacement method, and the density of the prepared ultra-high temperature ceramic was 98.8%.

[0055] Comparative Example

[0056] Comparative Example 1

[0057] Preparation method of ZrB2 (80 Vol.%)-SiC (20 Vol.%) ultra-high temperature ceramics:

[0058] Weigh out 80 vol.% ZrB2 powder and 20 vol.% SiC powder, with a particle size of 400–700 nm for SiC and 200–500 nm for ZrB2. First, place both powders in an ethanol solution and electromagnetically stir, with a solution-to-powder mass ratio of 10:1, to obtain a mixed slurry. Then, rotary evaporate the mixed slurry under vacuum using pure water as the condensing medium, and electromagnetically stir for 8 hours to obtain a dry mixed powder. Finally, sieve the dried mixed powder through a 200-mesh sieve to obtain a fine-particle-size, uniformly mixed composite ceramic powder product. The obtained composite ceramic powder product is then placed in a graphite mold and sintered in an SPS (Spark Plasma) furnace at 5 × 10⁻⁶ ℃. -4 Sintering was carried out under vacuum conditions, with a heating rate of 150℃ / min, a sintering temperature of 2000℃, a holding time of 5min, and a sintering pressure of 40MPa. After sintering, the ceramic was cooled to room temperature in the furnace to obtain the ZrB2(80Vol.%)-SiC(20Vol.%) ultra-high temperature ceramic of Comparative Example 1.

[0059] Comparative Example 2

[0060] Preparation method of ZrB2 (85 Vol.%)-SiC (15 Vol.%) ultra-high temperature ceramics:

[0061] Weigh out 85 vol.% ZrB2 powder and 15 vol.% SiC powder, with a particle size of 400–700 nm for SiC and 200–500 nm for ZrB2. First, place both powders in an ethanol solution and electromagnetically stir, with a solution-to-powder mass ratio of 8:1, to obtain a mixed slurry. Then, rotary evaporate the mixed slurry under vacuum using pure water as the condensing medium, and electromagnetically stir for 5 hours to obtain a dry mixed powder. Finally, sieve the dried mixed powder through a 250-mesh sieve to obtain a fine-particle-size, uniformly mixed composite ceramic powder product. Place the obtained composite ceramic powder product into a graphite mold and sinter it in an SPS (Spark Plasma) furnace at a 1×10⁻⁶ ℃. -4 Sintering was carried out under vacuum conditions, with a heating rate of 200℃ / min, a sintering temperature of 2100℃, a holding time of 4min, and a sintering pressure of 30MPa. After sintering, the ceramic was cooled to room temperature in the furnace to obtain ZrB2-SiC ultra-high temperature ceramic of Comparative Example 2.

[0062] Comparative Example 3

[0063] Preparation method of ZrB2 (75 Vol.%)-SiC (25 Vol.%) ultra-high temperature ceramics:

[0064] Weigh out 75 vol.% ZrB2 powder and 25 vol.% SiC powder, with a particle size of 400–700 nm for SiC and 200–500 nm for ZrB2. First, place both powders in an ethanol solution and electromagnetically stir, with a solution-to-powder mass ratio of 12:1, to obtain a mixed slurry. Then, rotary evaporate the mixed slurry under vacuum using pure water as the condensing medium, and electromagnetically stir for 10 hours to obtain a dry mixed powder. Finally, sieve the dried mixed powder through a 150-mesh screen to obtain a fine-particle-size, uniformly mixed composite ceramic powder product. Place the obtained composite ceramic powder product into a graphite mold and sinter it in an SPS (Spark Plasma) furnace at a 1×10⁻⁶ ℃. -3 Sintering was carried out under vacuum conditions, with a heating rate of 100℃ / min, a sintering temperature of 1900℃, a holding time of 6min, and a sintering pressure of 50MPa. After sintering, the ceramic was cooled to room temperature in the furnace to obtain the high-performance ZrB2-SiC ultra-high temperature ceramic of Comparative Example 3.

[0065] Test case

[0066] The ZrB2 (80 Vol.%)-atomic W-coated SiC (20 Vol.%) ultra-high temperature ceramic of Example 1, the ZrB2 (85 Vol.%)-atomic W-coated SiC (15 Vol.%) ultra-high temperature ceramic of Example 2, and the ZrB2 (75 Vol.%)-atomic W-coated SiC (25 Vol.%) ultra-high temperature ceramic of Example 3 were used as experimental groups.

[0067] Using SiC without atomic W coating as raw material, and employing the same preparation process, ZrB2 (80 Vol.%)-SiC (20 Vol.%) ultra-high temperature ceramics were prepared as control groups. Mechanical properties and high-temperature oxidation resistance were compared in these cases.

[0068] The microstructure and morphology of the material were characterized by scanning electron microscopy (SEM); the density of the ceramic material was measured by Archimedes' displacement method, and the average grain size was calculated by Image Pro Plus software; the fracture toughness was tested by crack method; the oxidation resistance test was carried out in a high-temperature muffle furnace, with an oxidation temperature of 1500℃, an oxidation time of 2h, and an atmospheric oxidation atmosphere.

[0069] Mechanical property test

[0070] The fracture toughness of ceramic materials was tested using a THVS-50 digital Vickers hardness tester to indent cracks. The loading pressure was 5 kg, and the holding time was 20 s. Five points were taken from each sample, and the crack length generated by the indentation was observed and measured using a scanning electron microscope. The formula for calculating fracture toughness is as follows: Where K IC Fracture toughness of ceramic materials (MPa·m) 1 / 2 ); H v E is Vickers hardness (MPa); E is elastic modulus (GPa); L is load (N); C is crack half length (mm).

[0071] Antioxidant performance test

[0072] High-temperature oxidation resistance testing was conducted using a JZ-1700 high-temperature muffle furnace. Before the oxidation experiment, the samples were polished. The oxidation temperature was 1500℃, the oxidation time was 2 hours, and the oxidation environment was atmospheric. The muffle furnace heating rate was 10℃ / min. After oxidation, the samples were cooled to room temperature with the furnace. The mass of the sample strips (accurate to milligrams) was recorded before and after the oxidation experiment, and the weight gain per unit area was calculated using the following formula. Finally, the microstructure of the oxide layer in the cross-section of the oxidized samples was analyzed using SEM and EDS techniques.

[0073]

[0074] In the formula, Δm is the weight gain per unit area of ​​the ceramic sample due to oxidation (mg·cm³). -2 m1 and m0 represent the mass (mg) of the sample before and after oxidation, respectively; S represents the surface area (cm²) of the oxidized ceramic sample. -2 ).

[0075] The experimental results are shown in Table 1.

[0076] Table 1. Fracture toughness and high-temperature oxidation weight gain of ceramic materials prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3

[0077]

[0078]

[0079] As shown in Table 1, compared with ZrB2-SiC ultra-high temperature ceramics prepared using SiC powder, the ZrB2-SiC ultra-high temperature ceramics prepared by coating SiC with atomic W in this invention exhibit significantly improved fracture toughness, ranging from 4.0 to 4.5 MPa·m. 1 / 2 Increased to 7.1–7.8 MPa·m 1 / 2 Meanwhile, the oxidative weight gain after oxidation at 1500℃ for 2 hours decreased significantly, from 7.6–8.7 mg·cm³. -2 Decreased to 4.2–5.7 mg·cm³ -2 It possesses both excellent mechanical properties and high-temperature oxidation resistance.

[0080] From the appendix Figure 5 and attached Figure 6It can be seen that the oxide layers of ZrB2 (80 Vol.%)-atomic W-coated SiC (20 Vol.%) in Example 1 and ZrB2 (80 Vol.%)-SiC (20 Vol.%) in Comparative Example 1 are both composed of a SiO2 layer and a SiC depleted layer. However, the SiO2 layer thickness of the ceramic material in Example 1 is much greater than that of the ceramic material in Comparative Example 1. The thick and dense SiO2 layer helps to suppress the inward diffusion of oxygen. At the same time, the SiC depleted layer thickness of the ceramic material in Example 1 is much smaller than that of the ceramic material in Comparative Example 1, which also indicates that the ceramic material in Example 1 is subjected to less oxidation and has better oxidation resistance. The above demonstrates the beneficial effect of using atomic W-coated SiC powder to prepare ZrB2-SiC ultra-high temperature ceramics on oxidation resistance.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications, comprising the following steps: 1) Atomic W coating SiC Using hexacarbonyl W powder as a precursor, atomic tungsten was coated onto the surface of SiC ceramic powder with a particle size of 400-700 nm by chemical vapor deposition to obtain atomically W-coated SiC ceramic powder; 2) Electromagnetic stirring for powder mixing Atomic W-coated SiC ceramic powder and ZrB2 ceramic powder were weighed separately. The particle size of ZrB2 ceramic powder was 200~500nm. The two powders were first placed in an ethanol solution and electromagnetically stirred to obtain a mixed slurry. Then, the mixed slurry was rotary evaporated under vacuum to obtain a dry mixed powder. Finally, the dry mixed powder was sieved to obtain a composite ceramic powder product with fine particle size and uniform mixing. 3) SPS sintering The composite ceramic powder product obtained in step 2) is loaded into a graphite mold and placed in an SPS discharge plasma sintering furnace for sintering under vacuum. After sintering, it is cooled to room temperature with the furnace to obtain high-performance ZrB2-SiC ultra-high temperature ceramics for aerospace applications.

2. The method for preparing a high-performance ZrB2-SiC ultra-high temperature ceramic for aerospace applications according to claim 1, characterized in that: The volume percentage of atomic W-coated SiC ceramic powder in the total volume of atomic W-coated SiC ceramic powder and ZrB2 ceramic powder is (15~25)%, and the volume percentage of ZrB2 ceramic powder in the total volume of atomic W-coated SiC ceramic powder and ZrB2 ceramic powder is (75~85)%.

3. The method for preparing a high-performance ZrB2-SiC ultra-high temperature ceramic for aerospace applications according to claim 1, characterized in that: The electromagnetic stirring process is as follows: a 99% ethanol solution is used as the medium, the mass ratio of solution to powder is 8~12:1, the electromagnetic stirring time is 5~10 h, and the sieve is 150~250 mesh.

4. The method for preparing a high-performance ZrB2-SiC ultra-high temperature ceramic for aerospace applications according to claim 1, characterized in that: The SPS sintering process: vacuum degree is 1x10 ‐4 ~1x10 ‐3 Pa, heating rate is 100~200 °C / min, sintering temperature is 1900~2100 °C, holding time is 4~6 min, and sintering pressure is 30~50 MPa.

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