SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance and preparation method and application thereof

Abstract

The application belongs to the technical field of ceramic materials, and discloses SiC-high-entropy carbide composite ceramics resistant to high-temperature oxidation and a preparation method and application thereof. 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C (HEC) are ball-milled to obtain mixed powder, and the mixed powder is cold isostatic pressed at 200-250 MPa to obtain ceramic blanks; the blanks are embedded with the mixed powder and sintered at 1800-1900 DEG C in vacuum to obtain the composite ceramics. The composite ceramics have excellent mechanical properties, and the high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C can react to generate liquid phase to fill the holes caused by intergranular phase decomposition, hinder the further oxidation of the matrix and maintain the dense structure of the matrix, thereby enhancing the high-temperature oxidation resistance of the matrix, and the composite ceramics can be applied in the preparation of refractory materials or high-temperature nozzles.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic materials, and particularly relates to a SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance and a preparation method and application thereof. BACKGROUND

[0002] The application of pressureless liquid phase sintered silicon carbide ceramics is limited due to the presence of a large amount of sintering aids, because the intergranular phase of the pressureless liquid phase sintered silicon carbide ceramics will decompose and migrate at high temperatures, so that the ceramic matrix structure is no longer dense, thereby affecting the mechanical properties. High-entropy carbides are proved to have excellent high-temperature oxidation resistance, and a dense oxide layer with high melting point will be formed on the surface of the ceramic after oxidation, thereby hindering the further oxidation of the ceramic matrix. SUMMARY

[0003] In order to solve the problems existing in the prior art, the application aims to provide a SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance.

[0004] Another object of the application is to provide a preparation method of the SiC-high-entropy carbide composite ceramic. The method introduces high-entropy carbides as a reinforcing phase, and the high-entropy carbides have excellent high-temperature oxidation resistance, thereby improving the high-temperature oxidation resistance of the pressureless liquid phase sintered SiC ceramic.

[0005] Still another object of the application is to provide an application of the SiC-high-entropy carbide composite ceramic.

[0006] The object of the application is achieved by the following technical scheme:

[0007] The SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance is prepared by mixing alpha-SiC, Al2O3, CeO2 and high-entropy carbides (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C, adding a solvent and a ball milling medium, mixing, ball milling, drying, sieving to obtain a mixed powder, cold isostatic pressing the mixed powder at 200-250 MPa to obtain a ceramic green body, and then embedding the green body with the mixed powder and vacuum sintering at 1800-1900 DEG C.

[0008] Preferably, the composite ceramic has a hardness of 20-22 GPa and a fracture toughness of 3.5-4.5 MPa·m 1 / 2 .

[0009] Preferably, the particle size of the α-SiC is 300-500 nm, the purity of the α-SiC is above 99.9%, the particle size of the Al2O3 is 100-300 nm, the purity of the Al2O3 is above 99.9%, the particle size of the CeO2 is 100-150 nm, and the purity of the CeO2 is above 99%.

[0010] Preferably, the mass ratio of the α-SiC:Al2O3:CeO2:high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C is (70-80):(4-6):(9-15):(7-9).

[0011] Preferably, the mass ratio of the above-mentioned powder, ball milling medium and solvent is 1:(5-10):(10-15), the ball milling medium is Si3N4, and the solvent is anhydrous ethanol.

[0012] The preparation method of the SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance comprises the following specific steps:

[0013] S1. Mixing α-SiC, Al2O3, CeO2 and high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C, adding solvent and ball milling medium, mixing, ball milling, drying, and sieving to obtain a mixed powder;

[0014] S2. Cold isostatic pressing the mixed powder at 200-250 MPa to obtain a ceramic green body;

[0015] S3. Embedding the ceramic green body with the mixed powder obtained in step S1, heating to 1800-1900 ℃ for vacuum sintering to obtain a SiC-high-entropy carbide composite ceramic.

[0016] Preferably, the thickness of the ceramic green body in step S2 is 3-5 mm.

[0017] Preferably, in step S3, the vacuum degree of the vacuum is below 10 Pa, the mixed powder is 15-20 times the mass of the ceramic green body, the heating rate is 5-10 ℃ / min, and the sintering time is 60-120 min.

[0018] The SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance is used in the field of preparing refractory materials or high-temperature nozzles.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1. The present application introduces high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C as a second phase in pressureless liquid phase sintering SiC ceramics, and sintering is carried out under an argon atmosphere, thereby improving the mechanical properties of SiC ceramics and enhancing the oxidation resistance of SiC ceramics at high temperatures. The pressureless liquid phase sintering SiC ceramics with high-entropy carbide still maintain a dense matrix structure after high-temperature (1300-1500℃) oxidation, effectively maintaining the mechanical properties of SiC-high-entropy carbide composite ceramics at high temperatures.

[0021] 2. The composite ceramics have excellent mechanical properties, and the high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C will react to generate liquid phase to fill the pores generated by intergranular phase decomposition, hinder the further oxidation of the matrix and maintain its dense structure, thereby enhancing its high-temperature oxidation resistance, and can be applied in the preparation of refractory materials or high-temperature nozzles. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Microstructure of SiC-high-entropy carbide composite ceramics of Example 1 and SiC ceramics of Comparative Example 1. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with specific examples, but should not be understood as a limitation of the present application. If not specifically indicated, the technical means used in the examples are conventional means known to those skilled in the art. Unless specifically indicated, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0024] Example 1

[0025] 1. α-SiC (purity 99.9%, particle size 300-500 nm), Al2O3 (purity 99.9%, particle size 100-300 nm), CeO2 (purity 99%, particle size 100-150 nm) and high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2)C, the mixed powder was obtained by ball-milling, drying and sieving according to a mass ratio of Si3N4 grinding balls to the powder of 5:1.

[0026] 2. The mixed powder was put into a mold and cold isostatic pressing was performed at a pressure of 200 MPa to obtain a ceramic green body with a thickness of 5 mm;

[0027] 3. The ceramic green body was put into a crucible and embedded with the mixed powder obtained in step 1, and then put into a vacuum sintering furnace and heated to 1800℃ at a rate of 10℃ / min and kept for 60 min, and the cooling rate was consistent with the heating rate, to obtain SiC-high-entropy carbide composite ceramic.

[0028] Comparative Example 1

[0029] The difference from Example 1 is that no high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C was added in step 1 to obtain SiC ceramic.

[0030] The Vickers hardness of the SiC-high-entropy carbide composite ceramic of Example 1 was 21 GPa, and the fracture toughness was 4 MPa·m 1 / 2 After high-temperature oxidation at 1500℃ for 1 h, the Vickers hardness of the composite ceramic decreased to 20.57 GPa, while the Vickers hardness of the SiC ceramic of Comparative Example 1 decreased to 14.86 GPa. Therefore, the addition of high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C improved the high-temperature oxidation resistance of SiC ceramic and effectively maintained the mechanical properties of SiC-high-entropy carbide composite ceramic at high temperature.

[0031] Figure 1 are microstructures of the SiC-high-entropy carbide composite ceramic of Example 1 and the SiC ceramic of Comparative Example 1. Among them, (a) is the SiC-high-entropy carbide composite ceramic of Example 1, and (b) is the SiC ceramic of Comparative Example 1. It can be seen from Figure 1 that after high-temperature oxidation, the SiC ceramic has a large number of pores in the matrix, which further affects its mechanical properties; while the SiC ceramic with high-entropy carbide still maintains a dense matrix structure after high-temperature oxidation, effectively maintaining the mechanical properties of SiC-high-entropy carbide composite ceramic at high temperature.

[0032] Example 2

[0033] 1. α-SiC (purity 99.9%, particle size 300-500 nm), Al2O3 (purity 99.9%, particle size 100-300 nm), CeO2 (purity 99%, particle size 100-150 nm) and high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C in a mass ratio of 75:5:12:8 were mixed, ball-mixed, dried and sieved according to a mass ratio of Si3N4 grinding ball to the above powder of 5:1 to obtain a mixed powder.

[0034] 2. The mixed powder was put into a mold and cold isostatic pressing was performed at a pressure of 210 MPa to obtain a ceramic green body with a thickness of 4.5 mm.

[0035] 3. The ceramic green body was put into a crucible, the mixed powder obtained in step 1 was used to embed the ceramic green body, and the embedded ceramic green body was put into a vacuum sintering furnace, heated to 1800°C at a rate of 10°C / min, kept for 60 min, and cooled at a rate consistent with the heating rate to obtain a SiC-high-entropy carbide composite ceramic.

[0036] The Vickers hardness of the SiC-high-entropy carbide composite ceramic of this example was 21 GPa, and the fracture toughness was 4.3 MPa·m 1 / 2 After high-temperature oxidation at 1400°C for 1 h, the Vickers hardness of the composite ceramic decreased to 20.36 GPa, and the Vickers hardness of the SiC ceramic of Comparative Example 1 decreased to 15.21 GPa, indicating that the addition of high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C improved the high-temperature oxidation resistance of the SiC ceramic and effectively maintained the mechanical properties of the SiC-high-entropy carbide composite ceramic at high temperature.

[0037] Example 3

[0038] 1. α-SiC (purity 99.9%, particle size 300-500 nm), Al2O3 (purity 99.9%, particle size 100-300 nm), CeO2 (purity 99%, particle size 100-150 nm) and high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C in a mass ratio of 80:4:9:7 were mixed, ball-mixed, dried and sieved according to a mass ratio of Si3N4 grinding ball to the above powder of 10:1 to obtain a mixed powder.

[0039] 2. Put the mixed powder into a mold, and cold isostatic pressing at a pressure of 240 MPa to obtain a ceramic green body with a thickness of 3 mm;

[0040] 3. Put the ceramic green body into a crucible, and embed the ceramic green body with the mixed powder obtained in step 1, and put into a vacuum sintering furnace, and heat at a rate of 10 ℃ / min to 1900 ℃ and keep for 60 min, and the cooling rate is consistent with the heating rate, to obtain SiC-high-entropy carbide composite ceramic.

[0041] The Vickers hardness of the SiC-high-entropy carbide composite ceramic of the embodiment is 22 GPa, and the fracture toughness is 4.5 MPa·m 1 / 2 After high-temperature oxidation at 1300 ℃ for 1 h, the Vickers hardness of the composite ceramic is reduced to 21.49 GPa, while the Vickers hardness of the SiC ceramic of Comparative Example 1 is reduced to 15.57 GPa, indicating that the addition of high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C improves the high-temperature oxidation resistance of SiC ceramic, and effectively maintains the mechanical properties of SiC-high-entropy carbide composite ceramic at high temperature.

[0042] The composite ceramic of the application has excellent mechanical properties, with a hardness of 20-22 GPa and a fracture toughness of 3.5-4.5 MPa·m 1 / 2 After high-temperature (1300-1500 ℃) oxidation, it still maintains a dense matrix structure, effectively maintaining the mechanical properties of SiC-high-entropy carbide composite ceramic at high temperature, and can be applied in the preparation of refractory materials or high-temperature nozzles.

[0043] The above embodiments are the preferred embodiments of the application, but the embodiments of the application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the application shall be equivalent replacement methods, and all shall be included in the protection scope of the application.

Claims

1. A SiC-high-entropy carbide composite ceramic having high-temperature oxidation resistance, characterized by, The composite ceramic is mixed with alpha-SiC, Al2O3, CeO2 and high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C, solvent and ball milling medium, mixing, ball milling, drying, sieving to obtain mixed powder; the mixed powder is cold isostatic pressed at 200-250 MPa to obtain ceramic green body; the ceramic green body is embedded with mixed powder and sintered at 1800-1900 DEG C in vacuum to obtain the composite ceramic; the mass ratio of alpha-SiC: Al2O3: CeO2: high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C is (70-80):(4-6):(9-15):(7-9).

2. The SiC-high entropy carbide composite ceramic with high-temperature oxidation resistance according to claim 1, characterized in that, The hardness of the composite ceramic is 20-22 GPa and the fracture toughness is 3.5-4.5 MPa·m at room temperature 1 / 2 .

3. The SiC-high entropy carbide composite ceramic with high-temperature oxidation resistance according to claim 1, characterized in that, The particle size of the α-SiC is 300-500 nm, the purity of the α-SiC is 99.9% or above, the particle size of the Al2O3 is 100-300 nm, the purity of the Al2O3 is 99.9% or above, the particle size of the CeO2 is 100-150 nm, and the purity of the CeO2 is 99% or above.

4. The SiC-high entropy carbide composite ceramic of claim 1, wherein, The mass ratio of the mixed powder, the ball milling medium and the solvent is 1:(5-10):(10-15), the ball milling medium is Si3N4, and the solvent is anhydrous ethanol.

5. The method of producing a high-temperature oxidation resistant SiC-high-entropy carbide composite ceramic according to any one of claims 1 to 4, characterized in that, The method comprises the following specific steps: S1. Mix α-SiC, Al2O3, CeO2, and high-entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C, add a solvent and a ball milling medium, mix, ball mill, dry, sieve, and obtain a mixed powder; S2. Cold isostatic pressing the mixed powder at 200-250 MPa to obtain a ceramic green body; S3. Embedding the ceramic green body with the mixed powder obtained in step S1, and vacuum sintering at a temperature of 1800-1900 ℃ to obtain the SiC-high-entropy carbide composite ceramic.

6. The method for preparing high-temperature oxidation-resistant SiC-high-entropy carbide multiphase ceramics according to claim 5, characterized in that, The thickness of the ceramic green body in step S2 is 3-5 mm.

7. The method of claim 5, wherein the SiC-high entropy carbide composite ceramic is prepared by the steps of: mixing a SiC powder, a high entropy carbide powder, and a binder to form a mixture; and sintering the mixture at a temperature of 1,800°C to 2,000°C in a vacuum or an inert gas atmosphere. In step S3, the vacuum degree of the vacuum is 10 Pa or below, the mixed powder is 15-20 times the mass of the ceramic green body, the heating rate is 5-10 ℃ / min, and the sintering time is 60-120 min.

8. Use of the SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance according to any one of claims 1-4 in the preparation of refractory materials or high-temperature nozzles.

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