SiC-HfB2 composite ceramic as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of ceramic materials, and discloses SiC-HfB2 composite ceramic as well as a preparation method and application thereof. The preparation method of the composite ceramic comprises the following steps: mixing HfSi2 powder, C powder and SiB6 powder, adding a solvent and a ball milling medium, mixing, drying and sieving to obtain ceramic powder, and carrying out SPS sintering at 1700-1900 DEG C under the vacuum degree of 10Pa and the pressure of 20-35MPa to obtain the composite ceramic. The SiC-HfB2 composite ceramic has good mechanical properties, the hardness at room temperature is 26-30 GPa, the fracture toughness is 3.5-4.5 MPa.m < 1 / 2 >, the bending strength is 450-600 MPa, and the SiC-HfB2 composite ceramic can be applied to an ultra-high temperature (2000 DEG C or above) environment or the field of radiation protection.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic materials and relates to a SiC-HfB2 composite ceramic and a preparation method and application thereof. Background Art

[0002] SiC-HfB2 ceramics have excellent properties such as high hardness, wear resistance, corrosion resistance, oxidation resistance, high temperature resistance, and high high temperature strength. They are used in high temperature kiln tools, combustion nozzles, heat exchangers, sealing rings, and traditional industrial fields. Traditional silicon carbide is difficult to sinter densely due to the characteristics of its crystal structure, resulting in decreased mechanical properties. However, due to the good chemical stability of silicon carbide itself, it has always received widespread attention in aviation or extreme fields. In order to improve the situation that single silicon carbide is difficult to sinter densely and to improve the mechanical properties of silicon carbide, some scholars have proposed introducing sintering aids to increase the density of silicon carbide ceramics. However, many scholars believe that the sintering of silicon carbide mostly improves the mechanical properties of silicon carbide ceramics by introducing a small amount of sintering aids (such as Y2O3). The above method is based on the traditional pressureless sintering to densify silicon carbide ceramics. However, the traditional solid phase sintering method has high temperature, which makes the grain size coarse, resulting in decreased mechanical properties. Summary of the invention

[0003] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the primary purpose of the present invention is to provide a SiC-HfB2 composite ceramic having excellent mechanical properties.

[0004] Another object of the present invention is to provide a method for preparing the above SiC-HfB2 composite ceramics. The method prepares silicon carbide-based ceramics by reaction sintering.

[0005] Another object of the present invention is to provide applications of the above carbide-based ceramics.

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

[0007] A SiC-HfB2 composite ceramic is prepared by mixing HfSi2 powder, C powder and SiB6 powder, adding solvent and ball milling medium, mixing, drying and sieving to obtain ceramic powder, and then SPS sintering is performed at 1700-1900°C under a vacuum degree of 10Pa, a pressure of 20-35MPa.

[0008] Preferably, the particle size of the HfSi2 powder is 1 to 3 μm, the particle size of the C powder is 40 to 60 nm, and the particle size of the SiB6 powder is 1 to 3 μm.

[0009] Preferably, the mass ratio of the total mass of the HfSi2 powder, C powder and SiB6 powder, the ball milling medium and the solvent is (14-16):(4-6):(1-3).

[0010] Preferably, the hardness of the composite ceramic is 26-30 GPa GPa, and the fracture toughness is 3.5-4.5 MPa·m 1 / 2 , the flexural strength is 450~600MPa.

[0011] The preparation method of the SiC-HfB2 composite ceramic comprises the following specific steps:

[0012] S1. The HfSi2 powder, C powder and SiB6 powder are mixed, a solvent and a ball milling medium are added, the mixture is mixed, ball milled, dried and sieved to obtain a ceramic powder;

[0013] S2. Brush a layer of BN on the inner surface of the graphite mold, put it into the graphite mold, and heat it to 1700-1900°C for SPS sintering at a pressure of 20-35MPa and a vacuum degree of 10Pa to obtain SiC-HfB2 composite ceramics.

[0014] Preferably, in step S1, the ball milling medium is SiC ball, the solvent is anhydrous ethanol, and the mesh size of the sieve is 80-1000 mesh.

[0015] Preferably, the heating rate in step S2 is 50-150° C. / min, and the sintering time is 5-10 min.

[0016] The SiC-HfB2 composite ceramic is used in the ultra-high temperature field, and the ultra-high temperature is above 2000°C.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The SiC-HfB2 composite ceramic of the present invention has good mechanical properties, with a Vickers hardness of 26 to 35 GPa GPa at room temperature and a fracture toughness of 3.5 to 4 MPa·m 1 / 2 , the bending strength is 350~500MPa. It can be used in ultra-high temperature (above 2000℃) environment or radiation protection field.

[0019] 2. The present invention adopts the SPS sintering method to synthesize SiC-HfB2 ceramics. This method has a fast sintering speed and can reduce the particle size. DETAILED DESCRIPTION

[0020] 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.

[0021] Example 1

[0022] 1. Mix HfSi2 powder (particle size 1-3 μm), C powder (40-60 nm) and SiB6 powder (particle size 1-3 μm) in a molar ratio of 3:7:1, use SiC grinding balls as the grinding medium, and use anhydrous ethanol (purity 99.99%) as the solvent. Mix SiC grinding balls in a mass ratio of 5:1 and the mixed powder by ball milling, dry, and sieve through a 80-1000 mesh screen to obtain ceramic powder.

[0023] 2. Brush a layer of BN on the inner surface of the graphite mold, put the ceramic powder into the graphite mold, the pressure is 30MPa, and under a vacuum degree of 10Pa, the temperature is raised to 1700℃ at a rate of 100℃ / min for SPS sintering, and the temperature is kept for 10min to obtain SiC-HfB2 composite ceramics.

[0024] The SiC-HfB2 composite ceramic prepared in this embodiment has a Vickers hardness of 26 GPa, a setting parameter of Vickers hardness of 200 g (Hv0.2), and a fracture toughness of 3.5 MPa·m 1 / 2 , the flexural strength is 350MPa.

[0025] Example 2

[0026] 1. Mix HfSi2 powder (particle size 1-3 μm), C powder (40-60 nm) and SiB6 powder (particle size 1-3 μm) in a molar ratio of 3:7:1, use SiC grinding balls as the grinding medium, and use anhydrous ethanol (purity 99.99%) as the solvent. Mix SiC grinding balls in a mass ratio of 5:1 and the mixed powder by ball milling, dry, and sieve through a 80-1000 mesh screen to obtain ceramic powder.

[0027] 2. Brush a layer of BN on the inner surface of the graphite mold, put the ceramic powder into the graphite mold, the pressure is 30MPa, and under a vacuum degree of 10Pa, the temperature is raised to 1800℃ at a rate of 100℃ / min for SPS sintering, and the temperature is kept for 10min to obtain SiC-HfB2 composite ceramics.

[0028] The SiC-HfB2 composite ceramic prepared in this embodiment has a Vickers hardness of 28 GPa (Hv0.2) and a fracture toughness of 3.8 MPa·m 1 / 2 , the flexural strength is 400MPa.

[0029] Example 3

[0030] 1. Mix HfSi2 powder (particle size 1-3 μm), C powder (40-60 nm) and SiB6 powder (particle size 1-3 μm) in a molar ratio of 3:7:1, use SiC grinding balls as the grinding medium, and use anhydrous ethanol (purity 99.99%) as the solvent. Mix SiC grinding balls and the mixed powder in a mass ratio of 5:1 by ball milling, dry, and sieve through a 80-1000 mesh screen to obtain ceramic powder.

[0031] 2. Brush a layer of BN on the inner surface of the graphite mold, put the ceramic powder into the graphite mold, the pressure is 30MPa, and under a vacuum degree of 10Pa, the temperature is raised to 1900℃ at a rate of 100℃ / min for SPS sintering, and the temperature is kept for 10min to obtain SiC-HfB2 composite ceramics.

[0032] The SiC-HfB2 composite ceramic prepared in this embodiment has a Vickers hardness of 35 GPa (Hv0.2) and a fracture toughness of 3.9 MPa·m 1 / 2 , the flexural strength is 450MPa.

[0033] 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 SiC-HfB2 composite ceramic, characterized in that: The composite ceramic is prepared by mixing HfSi2 powder, C powder and SiB6 powder, adding solvent and ball milling medium, mixing, drying and sieving to obtain ceramic powder, and then performing SPS sintering at 1700-1900° C. under a vacuum degree of 10Pa, a pressure of 20-35MPa and a temperature of 1000-1000° C.

2. The SiC-HfB2 composite ceramic according to claim 1, characterized in that: The particle size of the HfSi2 powder is 1 to 3 μm, the particle size of the C powder is 40 to 60 nm, and the particle size of the SiB6 powder is 1 to 3 μm.

3. The SiC-HfB2 composite ceramic according to claim 1, characterized in that: The mass ratio of the total mass of the HfSi2 powder, C powder and SiB6 powder, the ball milling medium and the solvent is (14-16):(4-6):(1-3).

4. The SiC-HfB2 composite ceramic according to claim 1, characterized in that: The composite ceramic has a hardness of 26 to 30 GPa GPa and a fracture toughness of 3.5 to 4.5 MPa·m 1 / 2 , the flexural strength is 450~600MPa.

5. The method for preparing the SiC-HfB2 composite ceramic according to any one of claims 1 to 4, characterized in that: The specific steps include: S1. The HfSi2 powder, C powder and SiB6 powder are mixed, a solvent and a ball milling medium are added, the mixture is mixed, ball milled, dried and sieved to obtain a ceramic powder; S2. Brush a layer of BN on the inner surface of the graphite mold, put it into the graphite mold, and heat it to 1700-1900°C for SPS sintering at a pressure of 20-35MPa and a vacuum degree of 10Pa to obtain SiC-HfB2 composite ceramics.

6. The method for preparing SiC-HfB2 composite ceramic according to claim 5, characterized in that: In step S1, the ball milling medium is SiC ball, the solvent is anhydrous ethanol, and the mesh size of the sieve is 80-1000 meshes.

7. The method for preparing SiC-HfB2 composite ceramic according to claim 5, characterized in that: The heating rate in step S2 is 50-150° C. / min, and the sintering time is 5-10 min.

8. Application of the SiC-HfB2 composite ceramic according to any one of claims 1 to 4 in the ultra-high temperature field.

9. The use of the SiC-HfB2 composite ceramic in the ultra-high temperature field according to claim 8, characterized in that: The ultra-high temperature is above 2000°C.