CN109678523B

CN109678523B - High-entropy ceramic with high-temperature strength and hardness and preparation method and application thereof

Info

Publication number: CN109678523B
Application number: CN201910040601.8A
Authority: CN
Inventors: 郭伟明; 张岩; 吴利翔; 张威; 林华泰
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2019-01-16
Filing date: 2019-01-16
Publication date: 2021-04-06
Anticipated expiration: 2039-01-16
Also published as: CN109678523A

Abstract

The invention belongs to the technical field of ceramic materials, and discloses a high-entropy ceramic with high-temperature strength and hardness, and a preparation method and application thereof. The ceramic is HfO₂、ZrO₂、WO₃、MoO₃、TiO₂And amorphous boron powder as raw materials, ball-milling and mixing the raw materials, and pressing the mixture into a green body; placing into a graphite crucible and vacuum heat treating to obtain (Hf)_xZr_yW_zMo_nTi_m)B₂Solid solution powder; and (3) heating the solid solution powder to 1000-1400 ℃ by adopting spark plasma sintering, filling protective atmosphere, and then heating to 1800-2200 ℃ for calcining to obtain the solid solution powder. The molecular formula of the ceramic is (Hf)_xZr_yW_zMo_nTi_m)B₂Wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, n is more than or equal to 0 and less than or equal to 1, and m is more than or equal to 0 and less than or equal to 1; and x + y + z + n + m is 1; the hardness of the ceramic is 28-42 GPa, and the fracture toughness is 5-10 MPa.m^1/2The bending strength and the high-temperature strength are both 800-1500MPa, and the weight change rate after heat treatment is 0.3-0.5%.

Description

High-entropy ceramic with high-temperature strength and hardness and preparation method and application thereof

Technical Field

The invention belongs to the technical field of ceramic materials, and particularly relates to high-entropy ceramic with high-temperature strength and hardness, and a preparation method and application thereof.

Background

Ultrahigh-temperature ceramic boride ZrB₂、TiB₂、HfB₂The like have good thermal stability and chemical stability, and attract great attention of researchers, and the high-temperature-resistant high-pressure-resistant high-temperature-resistant highAnd (3) candidate materials under extreme environments such as atomic and nitrogen atom environments at 2000 ℃ or higher), rocket engines (chemical reaction atmospheres at 3000 ℃ or higher), and the like. The melting points of the alloy are more than 3000 ℃, and the alloy still has good strength and good thermal shock resistance at more than 1200 ℃, so the alloy is hopefully applied to components such as wing leading edges and the like which need to be used in extreme environments. Researchers are now working on how to further improve their performance to accommodate applications in extreme environments. The prepared solid solution can effectively improve the performance of the material, the high-entropy ceramic material arouses the interest of researchers in recent years, and the high-entropy material has a large amount of dislocation in the system due to a large entropy value, has the excellent properties of high hardness, high toughness, corrosion resistance and the like, and is a very promising material applied to the fields of aerospace, ultrahigh-speed reentry vehicles, nuclear reactors and the like.

It has been reported in literature that most of high-entropy ceramics are prepared by sintering commercially available powder after high-energy ball milling to obtain high-entropy ceramic materials, and although the high-energy ball milling can reduce the particle size of the powder, the high-energy ball milling inevitably introduces ball milling media due to high energy to pollute the powder, and impurities mostly exist in the grain boundary position of the ceramics, which can reduce the high-temperature performance of the materials and limit the application thereof. W is one of the most hard alloys, if WB₂The performance of the material must be greatly improved by adding the high-entropy ceramic (Hf reported by Gild research)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2) The density of the B material is only 92.4 percent, and the hardness is only 17.5 GPa. Since there is little WB in commerce₂Powder of W₂B₅Powder instead of (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂The material is not a single-phase high-entropy ceramic but exists (Ti)_1.6W_2.4)B₄Phase, W₂B₅Powder of other boron compound (ZrB)₂、TiB₂、HfB₂、TaB₂、CrB₂And the like) the lattice structures are different, so that the single-phase high-entropy ceramic is difficult to form by solid solution, the performance of the single-phase high-entropy ceramic is reduced, and the application of the single-phase high-entropy ceramic at high temperature is influenced. In the literatureThe introduction of W is reported to remove impurities in the material, purify grain boundaries and improve the high-temperature performance of the material.

Disclosure of Invention

In order to solve the disadvantages and shortcomings of the prior art, the present invention provides a high-entropy ceramic having high-temperature strength and hardness. The ceramic has a uniform solid solution phase, stable components, stable high-temperature performance, and excellent mechanical property and oxidation resistance.

Another object of the present invention is to provide a method for preparing the above high-entropy ceramic having high-temperature strength and hardness.

Still another object of the present invention is to provide the use of the above high-entropy ceramic having high-temperature strength and hardness.

The purpose of the invention is realized by the following technical scheme:

a high-entropy ceramic having high-temperature strength and hardness, characterized in that the molecular formula of the high-entropy ceramic is (Hf)_xZr_yW_zMo_nTi_m)B₂Wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, m is more than or equal to 0 and less than or equal to 1, and x + y + z + n + m is equal to 1; the high-entropy ceramic is HfO₂、ZrO₂、WO₃、MoO₃、TiO₂Mixing the amorphous boron powder and the amorphous boron powder serving as raw material powder, adding a solvent and a ball milling medium for mixing, drying to obtain mixed powder, carrying out heat treatment on a mixed powder blank prepared by die pressing the mixed powder under a vacuum condition, firstly heating to 800-1200 ℃, keeping the temperature I, then heating to 1400-1600 ℃, keeping the temperature II, grinding and sieving to obtain the (Hf) powder_xZr_yW_zMo_nTi_m)B₂And (2) heating the ultrahigh-temperature high-entropy ceramic powder to 1000-1400 ℃ by adopting spark plasma sintering, filling protective atmosphere, and heating to 1800-2200 ℃ for calcining to obtain the ultrahigh-temperature high-entropy ceramic powder.

Preferably, the molecular formula of the high-entropy ceramic is (Hf)_xZr_yW_zMo_nTi_m)B₂Wherein x is more than or equal to 0.1 and less than or equal to 0.9, y is more than or equal to 0.1 and less than or equal to 0.9, z is more than or equal to 0.1 and less than or equal to 0.9, n is more than or equal to 0.1 and less than or equal to 0.9, m is more than or equal to 0.1 and less than or equal to 0.9, andx + y + z + n + m is 1.

Preferably, the HfO₂、ZrO₂、WO₃、MoO₃And TiO₂The purity of the HfO is more than or equal to 99.9 percent, and the HfO₂、ZrO₂、WO₃、MoO₃And TiO₂The particle size of the particles is 1 to 2 μm.

Preferably, the relative density of the ceramic>98 percent, hardness of 28-42 GPa and fracture toughness of 5-10 MPa.m^1/2The room temperature bending strength is 800-1500MPa, the high temperature strength is 800-1500MPa at 1000-1600 ℃, and the weight change rate of the ceramic after heat treatment at 1000-1500 ℃ is 0.3-0.5%.

Preferably, the ultrahigh-temperature high-entropy ceramic powder (Hf)_xZr_yW_zMo_nTi_m)B₂The purity of the ultra-high temperature high entropy ceramic powder is 99.0-99.9wt%, the grain size of the ultra-high temperature high entropy ceramic powder is 0.1-1 mu m, and the oxygen content of the ultra-high temperature high entropy ceramic powder is 0.1-0.5 wt%.

Preferably, the solvent is ethanol, propanol, methanol or acetone.

Preferably, the protective atmosphere is N₂Or Ar.

Preferably, the heating rates of the temperature rise to 800-1200 ℃ and the temperature rise to 1400-1600 ℃ are both 5-20 ℃/min, and the time of the heat preservation I and the heat preservation II is 0.5-2 h; the calcining time is 1-30 min, the calcining pressure is 10-100 MPa, and the heating rate when the temperature is raised to 1800-2200 ℃ is 100-400 ℃/min.

The preparation method of the high-entropy ceramic with high-temperature strength and hardness comprises the following specific steps:

s1, using HfO₂、ZrO₂、WO₃、MoO₃、TiO₂Adding a solvent and a ball milling medium into the amorphous boron powder serving as raw materials, mixing the amorphous boron powder and the ball milling medium on a roller ball mill for 10-48 hours, and drying to obtain mixed powder;

s2, placing the blank body formed by die pressing the mixed powder into a graphite crucible, heating to 800-1200 ℃ at the speed of 5-20 ℃/min, preserving heat for 0.5-2 h, and then heating to 1400-1600 ℃ at the speed of 5-20 ℃/minKeeping the temperature for 0.5-2 h to obtain (Hf DEG C)_xZr_yW_zMo_nTi_m)B₂Ultra-high temperature high entropy ceramic powder;

s3. will (Hf)_xZr_yW_zMo_nTi_m)B₂Putting the ultrahigh-temperature high-entropy ceramic powder into a graphite mold, heating to 1000-1400 ℃ at the speed of 100-400 ℃/min by adopting spark plasma sintering, filling a protective atmosphere, heating to 1800-2200 ℃ at the speed of 100-400 ℃/min, preserving heat for 1-30 min, and pressurizing to 10-100 MPa for calcination to obtain (Hf)_xZr_yW_zMo_nTi_m)B₂Ultrahigh-temperature high-entropy ceramic.

The high-entropy ceramic with high-temperature strength and hardness is applied to the field of ultra-high temperature limit.

The high-entropy ceramic with high-temperature strength and hardness is prepared from HfO₂、ZrO₂、WO₃、MoO₃、TiO₂And amorphous boron powder as raw materials to prepare (Hf)_xZr_yW_zMo_nTi_m)B₂The ultrahigh-temperature high-entropy ceramic powder solves the problem that W is difficult to dissolve in a solid manner by introducing high-performance W in situ. After spark plasma sintering, solid solution precipitation phase is difficult to appear due to high cooling speed, and single-phase (Hf) is obtained_xZr_yW_zMo_nTi_m)B₂Ultrahigh-temperature high-entropy ceramic due to ultrahigh-temperature transition metal boride HfB₂、ZrB₂、WB₂、MoB₂And TiB₂The ultrahigh-temperature high-entropy ceramic prepared by mutual solid solution has the properties of uniform solid solution phase, stable component, stable high-temperature performance, excellent mechanical property and excellent oxidation resistance.

Compared with the prior art, the invention has the following beneficial effects:

1. the high-entropy ceramic prepared by the invention has high purity of original powder and small particle size, can promote atomic diffusion in the process of forming a solid solution, can realize compact sintering at low temperature, improves sintering performance and improves material performance. The synthesized high-entropy ceramic powder has fine grains and uniform components. The ceramic has the advantages of uniform solid solution phase, stable components, stable high-temperature performance, excellent mechanical property and excellent oxidation resistance.

2. The invention adopts the ultrahigh-temperature high-entropy ceramic powder self-synthesized by the borothermic reduction method as the raw material to prepare the ultrahigh-temperature high-entropy ceramic, can effectively solve the defect that boride purchased commercially is difficult to dissolve in solid, can more easily prepare single-phase ultrahigh-temperature high-entropy ceramic,

3. the method of the invention can prepare single-phase (Hf)_xZr_yW_zMo_nTi_m)B₂The ultra-high temperature high entropy ceramic solves the problem that W is difficult to dissolve in solid, and high performance W is added to ensure that (Hf)_xZr_yW_zMo_nTi_m)B₂The performance of the ultrahigh-temperature high-entropy ceramic is greatly improved.

4. Compared with the reported method for mixing the raw material powder by high-energy ball milling of a plurality of borides in order to improve the powder activity, the raw material mixing method of the method adopts the roller ball mill, realizes high efficiency, simplicity and energy conservation, and avoids the oxidation of impurities and powder generated in the high-energy ball milling process. Compared with the physical mixing uniformity, the method achieves the chemical uniformity of the raw material components. It is also beneficial to the formation of a uniform solid melt phase of the sintered material, and also saves energy and cost.

Drawings

FIG. 1 (Hf) prepared in example 4_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂XRD patterns of the ultrahigh-temperature high-entropy ceramic powder and the ceramic.

Detailed Description

The following examples are presented to further illustrate the present invention and should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Example 1

1. With HfO₂(purity of powder 99.9%, particle diameter 2 μm), ZrO₂(purity of powder 99.9%, particle diameter 2 μm), MoO₃(purity of powder 99.9%, particle diameter 2 μm) and TiO₂(purity of powder 99%, particle size 2 μm) powder was blended in equal atomic ratio with amorphous boron powder (purity 96%, particle size 2 μm) as raw material to obtain (Hf)_0.25Zr_0.25Mo_0.25Ti_0.25)B₂Mixing the above oxides with amorphous boron powder.

2. Ethanol is used as solvent, Si is used as solvent₃N₄The balls are used as ball milling media, and are mixed for 24 hours on a roller ball mill, and mixed and dried to obtain mixed powder.

3. Placing the powder blank after the mixed powder mould pressing into a graphite crucible, heating to 1100 ℃ at the speed of 10 ℃/min, preserving heat for 2h, then heating to 1600 ℃ at the speed of 10 ℃/min, preserving heat for 1h, wherein the whole sintering process is vacuum, the pressure is 0.1Pa, grinding and sieving the obtained powder to obtain (Hf) (Hf is obtained_0.25Zr_0.25Mo_0.25Ti_0.25)B₂Ultrahigh-temperature high-entropy ceramic powder.

4. Will (Hf)_0.25Zr_0.25Mo_0.25Ti_0.25)B₂Putting the ultrahigh-temperature high-entropy ceramic powder into a graphite mould, heating to 2000 ℃ at the heating rate of 200 ℃/min, keeping the temperature for 5min, pressurizing to 30MPa, filling Ar gas at 1200 ℃, and sintering by discharge plasma (SPS) to obtain the ultrahigh-temperature high-entropy ceramic.

This example (Hf) was determined by laser particle size analysis_0.25Zr_0.25Mo_0.25Ti_0.25)B₂The grain diameter of the ultra-high temperature high entropy ceramic powder is 0.75 μm, and the oxygen content of the solid solution powder is 0.5wt% measured by a carbon-oxygen analyzer. The prepared ultrahigh-temperature high-entropy ceramic forms a uniform single-phase solid solution. The relative density is 98 percent, the hardness is 28GPa, and the fracture toughness is 5 MPa.m^1/2The bending strength at room temperature is 920MPa, the high-temperature performance of the ceramic is stable, the bending strength at high temperature of 1200 ℃ is 800MPa, the oxidation resistance of the ceramic is good, and the ceramic is heavy after heat treatment at 1200 DEG CThe amount increased by 0.5%.

Example 2

1. With HfO₂(purity of powder 99.9%, particle diameter 2 μm), ZrO₂(purity of powder 99.9%, particle diameter 2 μm), WO₃(purity of powder 99.9%, particle diameter 2 μm), MoO₃(purity of powder 99.9%, particle diameter 2 μm) and TiO₂(purity of powder 99%, particle size 2 μm) powder was blended in equal atomic ratio with amorphous boron powder (purity 96%, particle size 2 μm) as raw material to obtain (Hf)_0.1Zr_0.2W_0.3Mo_0.2Ti_0.2)B₂Mixing the above oxides with amorphous boron powder.

3. Placing the powder blank after the mixed powder is molded into a graphite crucible, heating to 1100 ℃ at the speed of 10 ℃/min, keeping the temperature for 1h, heating to 1500 ℃ at the speed of 10 ℃/min, keeping the temperature for 1h, wherein the whole sintering process is vacuum and the pressure is 0.1Pa, grinding and sieving the obtained powder to obtain (Hf)_0.1Zr_0.2W_0.3Mo_0.2Ti_0.2)B₂Ultrahigh-temperature high-entropy ceramic powder.

4. Will (Hf)_0.1Zr_0.2W_0.3Mo_0.2Ti_0.2)B₂Placing the ultrahigh-temperature high-entropy ceramic powder into a graphite mold, heating to 2000 deg.C at a heating rate of 300 deg.C/min, maintaining the temperature for 5min, pressurizing to 80MPa, charging Ar gas at 1200 deg.C, and sintering by discharge plasma (SPS) to obtain (Hf)_0.1Zr_0.2W_0.3Mo_0.2Ti_0.2)B₂Ultrahigh-temperature high-entropy ceramic.

This example (Hf) was determined by laser particle size analysis_0.1Zr_0.2W_0.3Mo_0.2Ti_0.2)B₂The grain diameter of the ultra-high temperature high entropy ceramic powder is 0.55 mu m, and the oxygen content of the solid solution powder is 0.3 wt% measured by a carbon-oxygen analyzer. The prepared ultrahigh-temperature high-entropy ceramic forms a uniform single-phase solid solution. The relative density is 99 percent, and the hardness is 40GPa, fracture toughness 8MPa m^1/2The bending strength at room temperature is 1060MPa, the high-temperature performance of the ceramic is stable, the bending strength at high temperature of 1200 ℃ is 980MPa, the oxidation resistance of the ceramic is good, and the weight is increased by 0.5 percent after heat treatment at 1200 ℃.

Example 3

1. With HfO₂(purity of powder 99.9%, particle diameter 2 μm), ZrO₂(purity of powder 99.9%, particle diameter 2 μm), WO₃(purity of powder 99.9%, particle diameter 2 μm), MoO₃(purity of powder 99.9%, particle diameter 2 μm) and TiO₂(purity of powder 99%, particle size 2 μm) powder was blended in equal atomic ratio with amorphous boron powder (purity 96%, particle size 2 μm) as raw material to obtain (Hf)_0.2Zr_0.3W_0.1Mo_0.2Ti_0.2)B₂Mixing the above oxides with amorphous boron powder.

3. Placing the powder blank after the mixed powder mould pressing into a graphite crucible, heating to 1000 ℃ at the speed of 10 ℃/min, keeping the temperature for 1h, then heating to 1550 ℃ at the speed of 10 ℃/min, keeping the temperature for 1h, wherein the whole sintering process is vacuum, the pressure is 0.1Pa, grinding and sieving the obtained powder to obtain (Hf)_0.2Zr_0.3W_0.1Mo_0.2Ti_0.2)B₂Ultrahigh-temperature high-entropy ceramic powder.

4. Will (Hf)_0.2Zr_0.3W_0.1Mo_0.2Ti_0.2)B₂Placing the ultrahigh-temperature high-entropy ceramic powder into a graphite mold, heating to 2000 deg.C at a heating rate of 200 deg.C/min, maintaining the temperature for 5min, pressurizing to 50MPa, charging Ar gas at 1200 deg.C, and sintering by discharge plasma (SPS) to obtain (Hf)_0.2Zr_0.3W_0.1Mo_0.2Ti_0.2)B₂Ultrahigh-temperature high-entropy ceramic.

This example (Hf) was determined by laser particle size analysis_0.2Zr_0.3W_0.1Mo_0.2Ti_0.2)B₂Particles of ultrahigh-temperature high-entropy ceramic powderThe particle size was 0.35 μm, and the oxygen content of the solid solution powder was 0.3% by weight as measured by a carbon-oxygen analyzer. The prepared ultrahigh-temperature high-entropy ceramic forms a uniform single-phase solid solution. The relative density is 99 percent, the hardness is 30GPa, and the fracture toughness is 6 MPa.m^1/2The room temperature bending strength is 1160MPa, the high temperature performance of the ceramic is stable, the bending strength at the high temperature of 1300 ℃ is 1080MPa, the oxidation resistance of the ceramic is good, and the weight is increased by 0.5 percent after the heat treatment at the temperature of 1300 ℃.

Example 4

1. With HfO₂(purity of powder 99.9%, particle diameter 2 μm), ZrO₂(purity of powder 99.9%, particle diameter 2 μm), WO₃(purity of powder 99.9%, particle diameter 2 μm), MoO₃(purity of powder 99.9%, particle diameter 2 μm) and TiO₂(purity of powder 99%, particle size 2 μm) powder was blended in equal atomic ratio with amorphous boron powder (purity 96%, particle size 2 μm) as raw material to obtain (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂Mixing the above oxides with amorphous boron powder.

3. Placing the powder blank after the mixed powder mould pressing into a graphite crucible, heating to 1100 ℃ at the speed of 10 ℃/min, preserving heat for 2h, then heating to 1600 ℃ at the speed of 10 ℃/min, preserving heat for 2h, wherein the whole sintering process is vacuum, the pressure is 0.1Pa, grinding and sieving the obtained powder to obtain (Hf) (Hf is obtained_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂Ultrahigh-temperature high-entropy ceramic powder.

4. Will (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂Placing the ultrahigh-temperature high-entropy ceramic powder into a graphite mold, heating to 2000 deg.C at a heating rate of 150 deg.C/min, maintaining the temperature for 10min, pressurizing to 30MPa, charging Ar gas at 1200 deg.C, and sintering by discharge plasma (SPS) to obtain (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂Ultrahigh-temperature high-entropy ceramic.

FIG. 1 shows (Hf) prepared in this example_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂XRD patterns of the ultrahigh-temperature high-entropy ceramic powder and the ceramic. Wherein, (a) is ultrahigh-temperature high-entropy ceramic powder, and (b) is ultrahigh-temperature high-entropy ceramic; as can be seen from (a) in the figure, (Hf) produced in the present example_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂No HfO is detected in the ultrahigh-temperature high-entropy ceramic powder₂、ZrO₂、WO₃、MoO₃And TiO₂Phase, amorphous boron powder is amorphous, so XRD cannot detect the boron powder, and only a small amount of W is detected₂B₅、WB、(Hf，Zr)O₂And (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂A solid solution phase in which W is hardly solid-dissolved with other substances to form a single-phase solid solution, and (Hf, Zr) O₂Difficult to remove, proving HfO₂、ZrO₂、WO₃、MoO₃And TiO₂Has undergone boron thermal reaction with boron and is converted into ultrahigh-temperature high-entropy ceramic powder. And with HfB₂And ZrB₂The comparison between the standard PDF cards 65-8678 and 65-8704 shows that (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂The peak of (2) was shifted to a high angle, and it was confirmed that five elements were dissolved in each other to decrease the lattice constant, and thus the diffraction peak was shifted. When (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂After the ultra-high temperature high entropy ceramic powder was sintered by SPS, as shown in FIG. 1(b), it detected only (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂(ii) a diffraction peak of (1), no other impurity peak, and (Hf) in comparison with FIG. 1(a)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂Further shift toward high angles, proving W₂B₅And WB phase is solid-dissolved in the high-entropy ceramic matrix, the lattice constant is reduced, and the diffraction peak is shifted to a high angle. This example resulted in a homogeneous single-phase ultra-high temperature high entropy ceramic solid solution.

By laser particle size divisionAnalysis of this example (Hf)_0.2Zr_0.2W_0.2Mo_0.2Ti_0.2)B₂The grain diameter of the ultra-high temperature high entropy ceramic powder is 0.25 μm, and the oxygen content of the solid solution powder is 0.2 wt% measured by a carbon-oxygen analyzer. The prepared ultrahigh-temperature high-entropy ceramic forms a uniform single-phase solid solution. The relative density is 99 percent, the hardness is 42GPa, and the fracture toughness is 10 MPa.m^1/2The room temperature bending strength is 1500MPa, the high temperature performance of the ceramic is stable, the high temperature bending strength of the ceramic is 1480MPa at the temperature of 1200 ℃, the oxidation resistance of the ceramic is good, and the weight is increased by 0.3 percent after heat treatment at the temperature of 1200 ℃.

Example 5

The difference from example 1 is that: separately prepare TiB₂、MoB₂、WB₂、ZrB₂And HfB₂Ultra-high temperature ceramics.

Example 6

The difference from example 1 is that: prepare (Hf)_0.1Ti_0.9)B₂Ultra-high temperature ceramics.

Example 7

The difference from example 1 is that: prepare (Zr)_y0.1Mo_0.9)B₂Ultra-high temperature ceramics.

Example 8

Example 9

The difference from example 1 is that: prepare (W)_0.2Mo_0.8)B₂Ultra-high temperature ceramics.

Example 10

The difference from example 1 is that: prepare (Hf)_0.3Mo_0.7)B₂Ultra-high temperature ceramics.

Example 11

The difference from example 1 is that: prepare (Hf)_0.4Zr_0.2W_0.1Mo_0.1Ti_0.2)B₂Ultra-high temperature ceramics.

Example 12

The difference from example 1 is that: prepare a(Hf_0.5Zr_0.1W_0.1Mo_0.2Ti_0.1)B₂Ultra-high temperature ceramics.

Example 13

The difference from example 1 is that: prepare (Hf)_0.6Zr_0.1W_0.1Mo_0.1Ti_0.1)B₂Ultra-high temperature ceramics.

Example 14

The difference from example 1 is that: prepare (Hf)_0.8Zr_0.05W_0.05Mo_0.1Ti_0.1)B₂Ultra-high temperature ceramics.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations and simplifications are intended to be included in the scope of the present invention.

Claims

1. A high-entropy ceramic having high-temperature strength and hardness, characterized in that the molecular formula of the high-entropy ceramic is (Hf)_xZr_yW_zMo_nTi_m）B₂Wherein, 0<x<1，0<y<1，0<z<1，0<n<1，0<m<1; and x + y + z + n + m = 1; the high-entropy ceramic is HfO₂、ZrO₂、WO₃、MoO₃、TiO₂Mixing the amorphous boron powder and the amorphous boron powder serving as raw material powder, adding a solvent and a ball milling medium for mixing, drying to obtain mixed powder, carrying out heat treatment on a mixed powder blank prepared by die pressing the mixed powder under a vacuum condition, firstly heating to 800-1200 ℃, keeping the temperature I, then heating to 1400-1600 ℃, keeping the temperature II, grinding and sieving to obtain the (Hf) powder_xZr_yW_zMo_nTi_m）B₂The method comprises the following steps of (1) heating the ultrahigh-temperature high-entropy ceramic powder to 1000-1400 ℃ by adopting spark plasma sintering, filling protective atmosphere, heating to 1800-2200 ℃, and calcining to obtain the ultrahigh-temperature high-entropy ceramic powder; the HfO₂、ZrO₂、WO₃、MoO₃And TiO₂The purity of the HfO is more than or equal to 99.9 percent, and the HfO₂、ZrO₂、WO₃、MoO₃And TiO₂The particle size of the particles is 1-2 mu m; the weight change rate of the ceramic after heat treatment at 1000-1500 ℃ is 0.3-0.5%; the hardness is 28-42 GPa, and the fracture toughness is 5-10 MPa.m^1/2The room temperature bending strength is 800-1500MPa, and the high temperature strength at 1000-1600 ℃ is 800-1500 MPa.

2. A high entropy ceramic having high temperature strength and hardness according to claim 1, wherein the high entropy ceramic has a molecular formula of (Hf)_xZr_yW_zMo_nTi_m）B₂Wherein x is more than or equal to 0.1 and less than or equal to 0.9, y is more than or equal to 0.1 and less than or equal to 0.9, z is more than or equal to 0.1 and less than or equal to 0.9, n is more than or equal to 0.1 and less than or equal to 0.9, m is more than or equal to 0.1 and less than or equal to 0.9, and x + y + z + n + m =1 is satisfied.

3. A high entropy ceramic having high temperature strength and hardness in accordance with claim 1, wherein the relative density of the ceramic is > 98%.

4. High-entropy ceramic with high-temperature strength and hardness according to claim 1, wherein the ultra-high-temperature high-entropy ceramic powder (Hf)_xZr_yW_zMo_nTi_m）B₂The purity of the ultra-high temperature and high entropy ceramic powder is 99.0-99.9wt%, the particle size of the ultra-high temperature and high entropy ceramic powder is 0.1-1 mu m, and the oxygen content of the ultra-high temperature and high entropy ceramic powder is 0.1-0.5 wt%.

5. A high-entropy ceramic having high-temperature strength and hardness according to claim 1, wherein the solvent is ethanol, propanol, methanol or acetone.

6. A high-entropy ceramic having high-temperature strength and hardness according to claim 1, wherein the protective atmosphere is N₂Or Ar.

7. The high-entropy ceramic with high-temperature strength and hardness according to claim 1, wherein the heating rates to 800-1200 ℃ and 1400-1600 ℃ are both 5-20 ℃/min, and the time for the heat preservation I and the heat preservation II is 0.5-2 h; the calcining time is 1-30 min, the calcining pressure is 10-100 MPa, and the heating rate when the temperature is raised to 1800-2200 ℃ is 100-400 ℃/min.

8. A preparation method of a high-entropy ceramic with high-temperature strength and hardness according to any one of claims 1 to 7, characterized by comprising the following specific steps:

s1, HfO₂、ZrO₂、WO₃、MoO₃、TiO₂Adding a solvent and a ball milling medium into the amorphous boron powder serving as raw materials, mixing the amorphous boron powder and the ball milling medium on a roller ball mill for 10-48 hours, and drying to obtain mixed powder;

s2, placing the blank body of the mixed powder after mould pressing into a graphite crucible, heating to 800-1200 ℃ at the speed of 5-20 ℃/min, preserving heat for 0.5-2 h, then heating to 1400-1600 ℃ at the speed of 5-20 ℃/min, preserving heat for 0.5-2 h, and obtaining (Hf)_xZr_yW_zMo_nTi_m）B₂Ultra-high temperature high entropy ceramic powder;

s3 (Hf)_xZr_yW_zMo_nTi_m）B₂Putting the ultrahigh-temperature high-entropy ceramic powder into a graphite mold, heating to 1000-1400 ℃ at the speed of 100-400 ℃/min by adopting spark plasma sintering, filling a protective atmosphere, heating to 1800-2200 ℃ at the speed of 100-400 ℃/min, preserving heat for 1-30 min, and pressurizing to 10-100 MPa for calcination to obtain (Hf)_xZr_yW_zMo_nTi_m）B₂High entropy ceramics.

9. Use of the high-entropy ceramic having high-temperature strength and hardness according to any one of claims 1 to 7 in the ultra-high temperature limit field.