Long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic and preparation method and application thereof

文档序号:2281 发布日期:2021-09-17 浏览:60次 中文

1. A preparation method of long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic is characterized by comprising the following operation steps: mixing any five carbides of TiC, ZrC, HfC, VC, WC, TaC and NbC with micron-grade high purity in equal molar ratio to obtain high-entropy carbide ceramic matrix, and adding Si3N4、Al2O3AlN and a sintering aid Y2O3Ball milling to obtain mixed powder, wherein the beta-SiAlON phase for preparing long rod shape is used as toughening phase; the mixed powder is filled into a graphite die, under the protective atmosphere, the axial pressure is applied to 30-40 MPa, the temperature is raised to 1850-2200 ℃, and SPS sintering is carried out, so that long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic is obtained; the addition amount of the toughening phase is 10-40% of the total mass of the mixed powder.

2. The method of claim 1, wherein: saidThe density of the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic is 96-99%, the Vickers hardness is 23-26 GPa, and the fracture toughness is 5-7 MPa.m1/2

3. The method of claim 1, wherein: the purity of the micron-grade high-purity TiC, ZrC, HfC, VC, WC, TaC and NbC is 99-100%.

4. The method of claim 1, wherein: the ball milling is roller ball milling, absolute ethyl alcohol is used as a solvent, and tungsten carbide balls are used as a ball milling medium; the rotating speed of the ball milling is 150-500 r/min, and the ball milling time is 8-24 h.

5. The method of claim 1, wherein: the sintering aid Y2O3Accounting for 0.3-1.5% of the total mass of the mixed powder.

6. The method of claim 1, wherein: the protective atmosphere is argon.

7. The method of claim 1, wherein: the heating rate is 50-200 ℃/min; the sintering time is 10-20 min.

8. The long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the long rod-shaped β -SiAlON toughened high entropy carbide ceramic according to claim 8 in the preparation of support parts, protective housings or structural components of complex structure under high temperature conditions.

Background

The concept of 'high entropy' is derived from research on high-entropy alloys in recent decades, and the alloy material with excellent performance and stable microstructure is prepared by virtue of the 'high entropy effect' of reactants in the preparation process. With the development of the preparation process, the theory of high entropy is gradually applied to the field of preparation of non-metallic compounds, and a high entropy ceramic material is produced.

The chemical formula of five-membered high-entropy ceramics is expressed as (A)0.2B0.2C0.2D0.2E0.2)FnWherein A, B, C, D, E is transition metal elements with equal molar weight, F is a ceramic material system, and the common systems at present comprise carbon, boron, oxygen, silicon and the like; the material has excellent mechanical property and chemical stability, and the mechanical property and the chemical property are very stable in high-temperature application occasions.

At present, in the research of high-entropy ceramics, the preparation of high-entropy carbide ceramics is mature day by day, and a plurality of scholars prepare (Hf) based on high-hardness carbide0.2Zr0.2Ta0.2M0.2Ti0.2) The research shows that the high-entropy treatment improves the oxidation resistance, elastic modulus and hardness of the material, and obviously reduces the thermal conductivity, and the high-entropy ceramic has wide application prospects in the fields of high-temperature metallurgy, engine structural members, thermal insulation members, supporting members and the like.

But the sintering of the material is difficult, the common preparation method needs quite high sintering temperature (more than 2000 ℃), and the ceramic material prepared by directly adopting commercial carbide powder to carry out solid solution sintering has lower relative density (about 93-95.1%); meanwhile, the toughness of the finished material is poor, and only parts with simple shapes can be prepared, so that the further application of the material is greatly restricted.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention mainly aims to provide a preparation method of long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic.

The invention further aims to provide the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic prepared by the preparation method. The high-entropy carbide ceramic utilizes the added long-rod-shaped beta-SiAlON as a second phase to realize toughening of the high-entropy carbide ceramic, improve the fracture toughness and the bending strength of the high-entropy carbide ceramic, and inhibit the growth of crystal grains in a matrix, thereby improving the sintering compactness of the material.

The invention also aims to provide application of the long rod-shaped beta-SiAlON toughened high-entropy carbide ceramic.

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

a preparation method of long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic comprises the following operation steps: mixing any five carbides of TiC, ZrC, HfC, VC, WC, TaC and NbC with micron-grade high purity in equal molar ratio to obtain high-entropy carbide ceramic matrix, and adding Si3N4、Al2O3AlN and a sintering aid Y2O3Ball milling to obtain mixed powder, wherein the beta-SiAlON phase for preparing long rod shape is used as toughening phase; the mixed powder is filled into a graphite die, under the protective atmosphere, the axial pressure is applied to 30-40 MPa, the temperature is raised to 1850-2200 ℃, and SPS sintering is carried out, so that long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic is obtained; the addition amount of the toughening phase is 10-40% of the total mass of the mixed powder.

The density of the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic is 96-99%, the Vickers hardness is 23-26 GPa, and the fracture toughness is 5-7 MPa.m1/2

The purity of the micron-grade high-purity TiC, ZrC, HfC, VC, WC, TaC and NbC is 99-100%.

The ball milling is roller ball milling, absolute ethyl alcohol is used as a solvent, and tungsten carbide balls are used as a ball milling medium; the rotating speed of the ball milling is 150-500 r/min, and the ball milling time is 8-24 h.

The sintering aid Y2O3Accounting for 0.3-1.5% of the total mass of the mixed powder.

The protective atmosphere is argon.

The heating rate is 50-200 ℃/min; the sintering time is 10-20 min.

The long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic prepared by the preparation method.

The long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic is applied to the preparation of supporting parts, protective shells or structural members with complex structures in high-temperature occasions.

Compared with the prior art, the invention has the following advantages and effects:

(1) the long-rod-shaped beta-SiAlON phase introduced by the invention inhibits the growth of carbide grains in the preparation process, and improves the sintering density and mechanical property of the material by refining the grains.

(2) The long rod-shaped beta-SiAlON phase toughened the toughness and the bending strength of the high-entropy carbide ceramic, so that the material can be widely applied to high-temperature structural members with complex structures, and the thermal conductivity and the chemical stability of the material are not influenced.

(3) The invention realizes the toughening of the high-entropy carbide ceramic by adding the long-rod-shaped beta-SiAlON phase, improves the bending strength of the high-entropy carbide ceramic, refines crystal grains in the material and improves the sintering density of the material; the obtained long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic material has the density of 96-99%, the Vickers hardness of 23-26 GPa and the fracture toughness of 5-7 MPa-m1 /2(ii) a The prepared ceramic can be widely applied to supporting parts, protective shells or structural members with complex structures under various high-temperature occasions.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1:

(1) using absolute ethyl alcohol as a solvent, using tungsten carbide balls as a ball milling medium, and mixing TiC (purity 99.6 wt.%), ZrC (purity 99.7 wt.%), NbC (purity 99.8 wt.%), HfC (purity 99.5 wt.%), and TaC (purity 99.7 wt.%) powder according to a molar ratio of 1: 1: 1: 1: 1, mixing materials at the rotating speed of 200r/min, and performing ball milling and mixing for 10 hours to obtain mixed powder A;

(2) using absolute ethyl alcohol as solvent and tungsten carbide ball as ball-milling medium to mix powder A and Si3N4(purity 99.9 wt.%), Al2O3(purity 99.7 wt.%), AlN (purity 99.8 wt.%) and Y2O3(purity 99.8 wt.%) so that long rod-like beta-SiAlON phases (i.e. formed from Si) will form in the mixed powder3N4、Al2O3And beta-Si obtained by AlN reaction4Al2O2N6The reaction formula is as follows: 3/4Si3N4+2/3AlN+2/3Al2O3→β-Si4Al2O2N6) The mass of (a) is 30% of the total mass of the mixed powder, and a sintering aid Y2O3Adding 2% of the total mass of the mixed powder by mass, enabling the rotating speed to be 200r/min, and carrying out ball milling and mixing for 10h to obtain mixed powder B;

(3) and (3) putting the mixed powder B into a graphite die, placing the graphite die in an SPS sintering furnace, axially pressurizing to 30MPa under the protection of argon atmosphere, heating to 2000 ℃ at the speed of 100 ℃/min, then preserving heat for 15min, and naturally cooling to room temperature along with the furnace to obtain the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic.

The density of the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic obtained in the embodiment is 98%, the Vickers hardness is 24GPa, and the fracture toughness is 6 MPa.m1/2

Example 2:

the difference from example 1 is that: and (4) in the step (3), the axial pressurization is 40 MPa.

The density of the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic obtained in the embodiment is 98%, the Vickers hardness is 25GPa, and the fracture toughness is 7 MPa.m1/2

Example 3:

the difference from example 1 is that: the temperature of the temperature rise in the step (3) is 2100 ℃.

The density of the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic obtained in the embodiment is 99%, the Vickers hardness is 24GPa, and the fracture toughness is 6 MPa.m1/2

Example 4

The difference from example 1 is that: and (4) keeping the temperature in the step (3) for 20 min.

The density of the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic obtained in the embodiment is 99%, the Vickers hardness is 24GPa, and the fracture toughness is 5 MPa.m1/2

Example 5

The difference from example 1 is that: the mass of the long rod-shaped beta-SiAlON phase of the mixed powder in the step (2) accounts for 20 percent of the total mass of the mixed powder;

the density of the long-rod-shaped beta-SiAlON toughened high-entropy carbide ceramic obtained in the embodiment is 97%, the Vickers hardness is 23GPa, and the fracture toughness is 6 MPa.m1/2

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.

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