SiC-high-entropy carbide composite ceramic with high-temperature oxidation resistance as well as preparation method and application of SiC-high-entropy carbide composite ceramic

Abstract

The invention belongs to the technical field of ceramic materials, and discloses high-temperature-oxidation-resistant SiC-high-entropy carbide composite ceramic as well as a preparation method and application thereof. The composite ceramic is prepared by the following steps: carrying out ball milling and mixing on alpha-SiC, Al2O3, CeO2 and high-entropy carbide (Hf < 0.2 > Zr < 0.2 > Ta0 < 0.2 > Nb < 0.2 > Ti < 0.2 >) C (HEC) to obtain mixed powder, and carrying out cold isostatic pressing molding at 200-250 MPa to obtain a ceramic biscuit; embedding the biscuit with the mixed powder, and performing vacuum sintering at the temperature of 1800-1900 DEG C to obtain the ceramic. The composite ceramic has excellent mechanical properties, high-entropy carbide (Hf0. 2Zr0. 2Ta0. 2Nb0. 2Ti0. 2) C can react at high temperature to generate a liquid phase to fill holes generated by decomposition of intergranular phases, further oxidation of a matrix is hindered, and a compact structure of the matrix is maintained, so that the high-temperature oxidation resistance of the composite ceramic is enhanced, and the composite ceramic can be applied to the field of preparation of refractory materials or high-temperature nozzles.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and in particular, relates to a SiC-high entropy carbide composite ceramic with high temperature oxidation resistance, and a preparation method and application thereof. Background Art

[0002] The presence of a large number of sintering aids in pressureless liquid phase sintering limits the application of silicon carbide ceramics at high temperatures. This is because the intergranular phase of pressureless liquid phase sintered silicon carbide ceramics will decompose and migrate at high temperatures, making the ceramic matrix structure no longer dense, thus affecting its mechanical properties. High entropy carbides have been proven to have excellent high-temperature oxidation resistance. After oxidation, they will form a high-melting point and dense oxide layer on the ceramic surface, which prevents the ceramic matrix from being further oxidized. Summary of the invention

[0003] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the object of the present invention is to provide a SiC-high entropy carbide composite ceramic with high temperature oxidation resistance.

[0004] Another object of the present invention is to provide a method for preparing the above-mentioned SiC-high entropy carbide composite ceramic. The method introduces high entropy carbide as a reinforcing phase, and because high entropy carbide has excellent high-temperature oxidation resistance, the high-temperature oxidation resistance of pressureless liquid phase sintered SiC ceramics is improved.

[0005] Another object of the present invention is to provide applications of the above-mentioned SiC-high entropy carbide composite ceramics.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A high temperature oxidation resistant SiC-high entropy carbide composite ceramic is a composite of 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 to mix, ball mill, dry and sieve to obtain mixed powder; the mixed powder is formed by cold isostatic pressing at 200-250MPa to obtain a ceramic green blank; the green blank is then embedded with the mixed powder and vacuum sintered at 1800-1900°C to obtain the obtained product.

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

[0009] Preferably, the particle size of the α-SiC is 300-500 nm, and the purity of the α-SiC is above 99.9%, the particle size of the Al2O3 is 100-300 nm, and 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 α-SiC:Al2O3:CeO2: high entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C's mass ratio is (70~80):(4~6):(9~15):(7~9).

[0011] Preferably, the mass ratio of the 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.

[0012] The method for preparing the high temperature oxidation resistant SiC-high entropy carbide composite ceramic comprises the following specific steps:

[0013] S1. 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. The mixed powder is cold isostatically pressed at 200 to 250 MPa to obtain a ceramic green body;

[0015] S3. The mixed powder obtained in step S1 is used to embed the ceramic green body, and the temperature is raised to 1800-1900° C. and vacuum sintered to obtain SiC-high entropy carbide composite ceramics.

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

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

[0018] The application of the high temperature oxidation resistant SiC-high entropy carbide composite ceramic in the field of preparing refractory materials or high temperature nozzles.

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

[0020] 1. The present invention introduces high entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C as the second phase, sintering in an argon atmosphere improves the mechanical properties of SiC ceramics and enhances the oxidation resistance of SiC ceramics at high temperatures. The pressureless liquid phase sintering SiC ceramics with high entropy carbides still maintains 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 of the present invention have excellent mechanical properties. At high temperatures, high entropy carbides (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C will react to generate a liquid phase to fill the holes produced by the decomposition of the intergranular phase, hindering the further oxidation of the matrix and maintaining its dense structure, thereby enhancing its high-temperature oxidation resistance and can be used in the preparation of refractory materials or high-temperature nozzles. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The microstructures of the SiC-high entropy carbide composite ceramic of Example 1 and the SiC ceramic of Comparative Example 1. DETAILED DESCRIPTION

[0023] The content of the present invention is further described below in conjunction with specific examples, but it should not be construed as limiting the present invention. If not specifically indicated, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0024] Example 1

[0025] 1. α-SiC (purity of 99.9%, particle size of 300-500nm), Al2O3 (purity of 99.9%, particle size of 100-300nm), CeO2 (purity of 99%, particle size of 100-150nm) and high entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2)C, ball-milled according to the mass ratio of Si3N4 grinding balls to the above powders being 5:1, dried, and sieved to obtain a mixed powder.

[0026] 2. Place the mixed powder into a mold and perform cold isostatic pressing at a pressure of 200 MPa to obtain a ceramic blank with a thickness of 5 mm;

[0027] 3. Place the ceramic blank into a crucible, and then embed the ceramic blank with the mixed powder obtained in step 1, place it in a vacuum sintering furnace, heat it to 1800°C at a rate of 10°C / min and keep it for 60 minutes. The cooling rate is consistent with the heating rate to obtain SiC-high entropy carbide composite ceramics.

[0028] Comparative Example 1

[0029] The difference from Example 1 is that high entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C, to obtain SiC ceramics.

[0030] The SiC-high entropy carbide composite ceramic of Example 1 has a Vickers hardness of 21 GPa and a fracture toughness of 4 MPa·m 1 / 2 After high-temperature oxidation at 1500℃ for 1h, the Vickers hardness of the composite ceramic dropped to 20.57GPa, while the Vickers hardness of the SiC ceramic in Comparative Example 1 dropped to 14.86GPa. 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C improves the high-temperature oxidation resistance of SiC ceramics and effectively maintains the mechanical properties of SiC-high entropy carbide composite ceramics at high temperatures.

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

[0032] Example 2

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

[0034] 2. The mixed powder is placed in a mold and is formed by cold isostatic pressing at a pressure of 210 MPa to obtain a ceramic blank with a thickness of 4.5 mm;

[0035] 3. Place the ceramic blank into a crucible, and then embed the ceramic blank with the mixed powder obtained in step 1, place it in a vacuum sintering furnace, heat it to 1800°C at a rate of 10°C / min and keep it at that temperature for 60 minutes. The cooling rate is consistent with the heating rate to obtain SiC-high entropy carbide composite ceramics.

[0036] The Vickers hardness of the SiC-high entropy carbide composite ceramic in this embodiment is 21 GPa, and the fracture toughness is 4.3 MPa·m 1 / 2 After 1h of high temperature oxidation at 1400℃, the Vickers hardness of the composite ceramic dropped to 20.36GPa, and the Vickers hardness of the SiC ceramic in Comparative Example 1 dropped to 15.21GPa, 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 ceramics and effectively maintains the mechanical properties of SiC-high entropy carbide composite ceramics at high temperatures.

[0037] Example 3

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

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

[0040] 3. Place the ceramic blank into a crucible, and then embed the ceramic blank with the mixed powder obtained in step 1, place it in a vacuum sintering furnace, heat it to 1900°C at a rate of 10°C / min and keep it for 60 minutes. The cooling rate is consistent with the heating rate to obtain SiC-high entropy carbide composite ceramics.

[0041] The Vickers hardness of the SiC-high entropy carbide composite ceramic in this embodiment is 22 GPa, and the fracture toughness is 4.5 MPa·m 1 / 2 After 1h of high temperature oxidation at 1300℃, the Vickers hardness of the composite ceramic dropped to 21.49GPa, while the Vickers hardness of the SiC ceramic in Comparative Example 1 dropped to 15.57GPa, 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 ceramics and effectively maintains the mechanical properties of SiC-high entropy carbide composite ceramics at high temperatures.

[0042] The composite ceramic of the present invention has excellent mechanical properties, a hardness of 20 to 22 GPa at room temperature, and a fracture toughness of 3.5 to 4.5 MPa·m 1 / 2 After high-temperature (1300-1500°C) oxidation, the matrix structure remains dense, effectively maintaining the mechanical properties of SiC-high entropy carbide composite ceramics at high temperatures, and can be used in the preparation of refractory materials or high-temperature nozzles.

[0043] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A high temperature oxidation resistant SiC-high entropy carbide composite ceramic, characterized in that: The composite ceramic is a composite of 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 to mix, ball mill, dry and sieve to obtain mixed powder; the mixed powder is formed by cold isostatic pressing at 200-250MPa to obtain a ceramic green body; the ceramic green body is then embedded with the mixed powder and vacuum sintered at 1800-1900°C to obtain the obtained product.

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

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

4. The high temperature oxidation resistant SiC-high entropy carbide composite ceramic according to claim 1, characterized in that: The α-SiC:Al2O3:CeO2: high entropy carbide (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C's mass ratio is (70~80):(4~6):(9~15):(7~9).

5. The high temperature oxidation resistant SiC-high entropy carbide composite ceramic according to claim 1, characterized in that: The mass ratio of the mixed powder, ball milling medium and solvent is 1:(5-10):(10-15), the ball milling medium is Si3N4, and the solvent is anhydrous ethanol.

6. The method for preparing the high temperature oxidation resistant SiC-high entropy carbide composite ceramic according to any one of claims 1 to 5, characterized in that: The specific steps include: S1. 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; S2. The mixed powder is cold isostatically pressed at 200 to 250 MPa to obtain a ceramic green body; S3. The mixed powder obtained in step S1 is used to embed the ceramic green body, and the temperature is raised to 1800-1900° C. and vacuum sintered to obtain SiC-high entropy carbide composite ceramics.

7. The method for preparing the high temperature oxidation resistant SiC-high entropy carbide composite ceramic according to claim 6, characterized in that: The thickness of the ceramic blank in step S2 is 3-5 mm.

8. The method for preparing the high temperature oxidation resistant SiC-high entropy carbide composite ceramic according to claim 6, characterized in that: The vacuum degree of the vacuum in step S3 is below 10 Pa, the mixed powder is 15 to 20 times the mass of the ceramic green body, the heating rate is 5 to 10° C. / min, and the sintering time is 60 to 120 min.

9. Use of the high temperature oxidation resistant SiC-high entropy carbide composite ceramic according to any one of claims 1 to 5 in the field of preparing refractory materials or high temperature nozzles.

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