A SiC-HfB2 composite ceramic, its preparation method and application

Abstract

This invention belongs to the field of ceramic materials technology, and discloses a SiC-HfB2 composite ceramic, its preparation method, and its application. The composite ceramic is prepared by mixing HfSi2 powder, C powder, and SiB6 powder, adding solvent and ball milling media, mixing, drying, and sieving to obtain ceramic powder. The powder is then sintered under vacuum of 10 Pa and pressure of 20–35 MPa at 1700–1900 °C using SPS. This SiC-HfB2 composite ceramic exhibits good mechanical properties, with a hardness of 26–30 GPa at room temperature and a fracture toughness of 3.5–4.5 MPa·m. 1 / 2 With a bending strength of 450-600MPa, it can be used in ultra-high temperature (above 2000℃) environments or radiation protection fields.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, and relates to a SiC-HfB2 composite ceramic, its preparation method and application. Background Technology

[0002] SiC-HfB2 ceramics possess excellent properties such as high hardness, wear resistance, corrosion resistance, oxidation resistance, high temperature resistance, and high high-temperature strength, making them suitable for applications in high-temperature kiln furniture, combustion nozzles, heat exchangers, sealing rings, and traditional industrial fields. Traditional silicon carbide, due to its crystal structure, is difficult to densify, leading to a decrease in mechanical properties. However, due to its inherent good chemical stability, silicon carbide has always attracted widespread attention in aerospace and extreme applications. To address the difficulty of densifying single-phase silicon carbide and improve its mechanical properties, some scholars have proposed introducing sintering aids to increase the density of silicon carbide ceramics. However, many scholars believe that most silicon carbide sintering improves mechanical properties by introducing small amounts of sintering aids (such as Y2O3). The above methods are based on traditional pressureless sintering to densify silicon carbide ceramics. However, traditional solid-state sintering methods involve high temperatures, resulting in coarse grain sizes and a decrease in mechanical properties. Summary of the Invention

[0003] In order to overcome the shortcomings and disadvantages of the existing technology, the primary objective of this invention is to provide a SiC-HfB2 composite ceramic with excellent mechanical properties.

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

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

[0006] The objective of this invention is achieved through the following technical solution:

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

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

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

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

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

[0012] S1. Mix HfSi2 powder, C powder and SiB6 powder, add solvent and ball milling media, and then mix, ball mill, dry and sieve to obtain ceramic powder;

[0013] S2. A layer of BN is brushed onto the inner surface of the graphite mold, which is then placed into the graphite mold. The pressure is 20-35 MPa, and the temperature is raised to 1700-1900℃ under a vacuum of 10 Pa to carry out SPS sintering to obtain SiC-HfB2 composite ceramic.

[0014] Preferably, the ball milling medium in step S1 is SiC balls, the solvent is anhydrous ethanol, and the sieve mesh size 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, where the ultra-high temperature is above 2000℃.

[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 26-35 GPa at room temperature and a fracture toughness of 3.5-4 MPa·m. 1 / 2 Its flexural strength is 350–500 MPa. It can be used in ultra-high temperature (above 2000℃) environments or radiation protection fields.

[0019] 2. This invention employs the SPS sintering method to synthesize SiC-HfB2 ceramics. This method offers a fast sintering speed and can reduce particle size. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments 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 this technical field.

[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 media and anhydrous ethanol (99.99% purity) as the solvent. Then, ball mill the mixture with SiC grinding balls in a mass ratio of 5:1. After drying, sieve through an 80-1000 mesh screen to obtain ceramic powder.

[0023] 2. Brush a layer of BN onto the inner surface of the graphite mold, place the ceramic powder into the graphite mold, apply a pressure of 30 MPa, and sinter at a vacuum of 10 Pa, heating to 1700 °C at a rate of 100 °C / min for SPS sintering, and hold for 10 min to obtain SiC-HfB2 composite ceramic.

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

[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 media and anhydrous ethanol (99.99% purity) as the solvent. Then, ball mill the mixture with SiC grinding balls in a mass ratio of 5:1. After drying, sieve through an 80-1000 mesh screen to obtain ceramic powder.

[0027] 2. Brush a layer of BN onto the inner surface of the graphite mold, place the ceramic powder into the graphite mold, apply a pressure of 30 MPa, and sinter at a vacuum of 10 Pa, heating to 1800 °C at a rate of 100 °C / min for SPS sintering, and hold for 10 min to obtain SiC-HfB2 composite ceramic.

[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 Its flexural strength is 400 MPa.

[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 media and anhydrous ethanol (purity 99.99%) as the solvent. Then, ball mill the mixture with SiC grinding balls in a mass ratio of 5:1. After drying, sieve through an 80-1000 mesh screen to obtain ceramic powder.

[0031] 2. A layer of BN is brushed onto the inner surface of the graphite mold. The ceramic powder is placed into the graphite mold under a pressure of 30 MPa and a vacuum of 10 Pa. The temperature is increased to 1900 °C at a rate of 100 °C / min for SPS sintering and held for 10 min to obtain SiC-HfB2 composite ceramic.

[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 Its flexural strength is 450 MPa.

[0033] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within 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 media, mixing, drying, and sieving to obtain ceramic powder. The powder is then sintered under vacuum of 10 Pa and pressure of 20-35 MPa at 1700-1900℃ using SPS. The particle size of the HfSi2 powder is 1-3 µm, the C powder is 40-60 nm, and the SiB6 powder is 1-3 µm. The mass ratio of the total mass of HfSi2 powder, C powder, and SiB6 powder to the mass ratio of ball milling media to solvent is (14-16):(4-6):(1-3). The molar ratio of HfSi2 powder, C powder, and SiB6 powder is 3:7:

1. The composite ceramic has a Vickers hardness of 26-35 GPa and a fracture toughness of 3.5-4 MPa·m at room temperature. 1 / 2 Its flexural strength is 350~500MPa.

2. The method for preparing SiC-HfB2 composite ceramics according to claim 1, characterized in that, The specific steps include the following: S1. Mix HfSi2 powder, C powder and SiB6 powder, add solvent and ball milling media, and then mix, ball mill, dry and sieve to obtain ceramic powder; S2. Brush a layer of BN onto the inner surface of the graphite mold, load the ceramic powder into the graphite mold, apply a pressure of 20~35MPa, and sinter at a vacuum of 10Pa and a temperature of 1700~1900℃ to obtain SiC-HfB2 composite ceramic.

3. The method for preparing SiC-HfB2 composite ceramics according to claim 2, characterized in that, The ball milling media in step S1 is SiC balls, the solvent is anhydrous ethanol, and the sieve mesh size is 80~1000 mesh.

4. The method for preparing SiC-HfB2 composite ceramics according to claim 2, characterized in that, The heating rate in step S2 is 50~150 ℃ / min, and the sintering time is 5~10 min.

5. The application of the SiC-HfB2 composite ceramic according to claim 1 in the ultra-high temperature field, characterized in that, The ultra-high temperature is above 2000℃.