阅读说明：本技术 一种高熵二硼化物-碳化硼复相陶瓷、制备方法及其应用 (High-entropy diboride-boron carbide complex phase ceramic, preparation method and application thereof ) 是由 冉松林 王东 丁祥 金星 李庆归 于 2021-07-29 设计创作，主要内容包括：本发明涉及复相陶瓷技术领域,具体涉及一种高熵二硼化物-碳化硼复相陶瓷、制备方法及其应用；该复相陶瓷包括如下摩尔组分的混合料：过渡金属碳化物(碳化钛、碳化锆、碳化铪、碳化铌、碳化钽、碳化钒、碳化铬、碳化钼、碳化钨)中的5～9种,每种0～1份,硼粉32～60份。所述过渡金属碳化物为其粉末,纯度＞98％,粒度0.5～3μm。所述硼粉纯度＞95％,粒度0.5～3μm。该高熵二硼化物-碳化硼复相陶瓷维氏硬度Hv5≥20GPa,抗弯强度≥420MPa,断裂韧性≥5.0MPa m～(1/2)。本发明实现了轻质、高强韧高熵二硼化物-碳化硼复相陶瓷的快速原位自生制备,且烧结温度低,因而在超高温材料、超硬材料、陶瓷刀具等领域具有广泛的应用前景。(The invention relates to the technical field of complex phase ceramics, in particular to high-entropy diboride-boron carbide complex phase ceramics, a preparation method and application thereof; the complex phase ceramic comprises the following mixture of molar components: 5-9 transition metal carbides (titanium carbide, zirconium carbide, hafnium carbide, niobium carbide, tantalum carbide, vanadium carbide, chromium carbide, molybdenum carbide and tungsten carbide) in 0-1 part of each, and 32-60 parts of boron powder. The transition metal carbide is powder of the transition metal carbide, the purity is more than 98%, and the granularity is 0.5-3 mu m. The purity of the boron powder is more than 95%, and the granularity is 0.5-3 mu m. The Vickers hardness Hv5 of the high-entropy diboride-boron carbide complex phase ceramic is more than or equal to 20GPa, the bending strength is more than or equal to 420MPa, and the fracture toughness is more than or equal to 5.0MPa m 1/2 . The invention realizes the rapid in-situ self-generation preparation of the lightweight, high-strength and high-entropy diboride-boron carbide complex phase ceramic,and the sintering temperature is low, so the method has wide application prospect in the fields of ultra-high temperature materials, superhard materials, ceramic cutters and the like.)

1. The high-entropy diboride-boron carbide complex phase ceramic is characterized by comprising the following components: transition metal carbide powder and boron powder, wherein the transition metal carbide is any 5-9 of titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide and tungsten carbide.

2. The high-entropy diboride-boron carbide complex phase ceramic as claimed in claim 1, wherein the molar parts of the components are respectively as follows: 1-5 parts of each transition metal carbide powder, and 5-8 times of the total parts of the transition metal carbide powder.

3. The high-entropy diboride-boron carbide complex phase ceramic according to claim 1, wherein the purity of the transition metal carbide powder is more than 98%, and the particle size is 0.5-3 μm.

4. The high-entropy diboride-boron carbide complex phase ceramic according to claim 1, wherein the boron powder has a purity of > 95% and a particle size of 0.5-3 μm.

5. A preparation method of the high-entropy diboride-boron carbide complex phase ceramic as claimed in any one of claims 1 to 4, characterized by comprising the following steps:

s1: putting transition metal carbide powder, boron powder and absolute ethyl alcohol into a ball milling tank, adding zirconia grinding balls, and mixing for 24 hours on a ball milling mixer at the speed of 100 r/min;

s2: evaporating the slurry mixed in the step S1 to dryness, and then drying for 24h at 80 ℃;

s3: grinding the dried mixed powder in the step S2 in a mortar, and sieving the ground mixed powder by a standard sieve of 200 meshes;

s4: putting the mixed powder sieved in the step S3 into a graphite die, heating to 1900-2200 ℃ in a discharge plasma sintering furnace at a speed of 100-200 ℃/min, pressurizing at 30-50 MPa, keeping for 1-20 min, and cooling and decompressing;

s5: and demolding and taking out the complex-phase ceramic block from the graphite mold.

6. The application of the high-entropy diboride-boron carbide complex phase ceramic as defined in any one of claims 1 to 4 in the fields of ultra-high temperature materials, superhard materials and ceramic cutters.

Technical Field

The invention relates to the technical field of complex phase ceramics, in particular to high-entropy diboride-boron carbide complex phase ceramics, a preparation method and application thereof.

Background

Ultra-high temperature materials generally refer to a class of materials that have a service temperature in excess of 2000 ℃. Typically comprising refractory metals, carbon materials and ultra high temperature ceramics (borides, carbides and nitrides of transition metals).

The high-entropy boride, carbide and nitride have high strength and high hardness, and have high entropy effect which is not possessed by the traditional ceramic material, so that excellent oxidation resistance and corrosion resistance are obtained. The method has important value for the development and application of novel ultra-high temperature heat-proof materials, wear-resistant and oxidation-resistant high-speed cutting tools, drill bits and other mechanical parts.

Although the high-entropy boride ceramic has excellent performance, the defects of difficult sintering, large brittleness, poor service reliability and the like still exist, and the defects are mainly attributed to the following reasons: first, because the metal boride has a high melting point (TiB)₂Has a melting point of 2980 ℃ and ZrB₂Melting point of 3040 ℃ and TaB₂The melting point is 3100 ℃), the high covalent bond coordination property and the low self-diffusion coefficient make the traditional sintering process difficult to obtain compact materials; secondly, because of the characteristic of difficult sintering, higher sintering temperature is needed, but high-temperature sintering can obtain high density and simultaneously inevitably cause grain growth and even abnormal growth, thus reducing the strength of the ceramic; thirdly, due to the high-temperature sintering characteristics of the ceramic, the mature methods of fiber toughening, phase change toughening and the like are difficult to be applied to the structure design, so that the brittleness and the reliability are poor.

At present, the high-entropy diboride ceramic composite material is generally prepared by adopting a method of combining boron-carbon thermal reduction powder preparation with high-temperature sintering. The single-phase diboride high-entropy ceramic and the complex-phase diboride high-entropy ceramic prepared by the method have the defects of large grain size, easy introduction of oxygen pollution to hinder sintering densification, and limited promotion of high-entropy effect and relative material performance enhancement.

In view of the above-mentioned drawbacks, the inventors of the present invention have finally obtained the present invention through a long period of research and practice.

Disclosure of Invention

The invention aims to solve the problems that the high-entropy diboride ceramic composite material prepared by the existing high-temperature sintering method has larger grain size and is easy to introduce oxygen pollution, so that the improvement of high-entropy effect and relative material performance enhancement is limited, and provides a high-entropy diboride-boron carbide composite ceramic, a preparation method and application thereof.

In order to achieve the aim, the invention provides a high-entropy diboride-boron carbide complex phase ceramic which comprises the following components: transition metal carbide powder and boron powder, wherein the transition metal carbide is any 5-9 of titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide and tungsten carbide.

The molar parts of the components are respectively as follows: 1-5 parts of each transition metal carbide powder, and 5-8 times of the total parts of the transition metal carbide powder.

The purity of the transition metal carbide powder is more than 98%, and the particle size is 0.5-3 mu m.

The purity of the boron powder is more than 95%, and the granularity is 0.5-3 mu m.

The invention also discloses a preparation method of the high-entropy diboride-boron carbide complex phase ceramic, which comprises the following steps:

s1: putting transition metal carbide powder, boron powder and absolute ethyl alcohol into a ball milling tank, adding zirconia grinding balls, and mixing for 24 hours on a ball milling mixer at the speed of 100 r/min;

s2: evaporating the slurry mixed in the step S1 to dryness, and then drying for 24h at 80 ℃;

s3: grinding the dried mixed powder in the step S2 in a mortar, and sieving the ground mixed powder by a standard sieve of 200 meshes;

s4: putting the mixed powder sieved in the step S3 into a graphite die, heating to 1900-2200 ℃ in a discharge plasma sintering furnace at a speed of 100-200 ℃/min, pressurizing at 30-50 MPa, keeping for 1-20 min, and cooling and decompressing;

s5: and demolding and taking out the complex-phase ceramic block from the graphite mold.

The invention also discloses application of the high-entropy diboride-boron carbide complex phase ceramic in the fields of ultra-high temperature materials, superhard materials and ceramic cutters.

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

1. the in-situ reaction self-generation process adopted by the invention realizes the sintering densification of the complex phase ceramic while generating the high-entropy diboride and the boron carbide in situ. The sintering densification temperature can be reduced, the oxygen pollution caused by powder mixing can be reduced, and the in-situ self-generated high-entropy diboride and boron carbide have fine (about 1 micron, shown in figure 2) grains and good compatibility;

2. the high-entropy diboride-boron carbide complex phase ceramic prepared by the method has lower density, higher hardness, strength and fracture toughness than single-phase high-entropy diboride ceramic with the same components;

3. the Vickers hardness Hv5 of the prepared complex phase ceramic is more than or equal to 20GPa, the bending strength is more than or equal to 420MPa, and the fracture toughness is more than or equal to 5.0MPa m^1/2. Compared with single-phase high-entropy diboride ceramic with the same component (Hv5 is 19.44 +/-0.50 GPa, and the fracture toughness is 2.83 +/-0.15 MPa m^1/2) The high-entropy diboride-boron carbide complex phase ceramic prepared by the invention has the advantages of light weight, high strength and toughness;

4. the invention realizes the in-situ reaction rapid preparation of the high-performance high-entropy diboride-boron carbide complex phase ceramic, and has low sintering temperature and obvious grain refinement effect, thereby having wide application prospect in the fields of ultra-high temperature materials, superhard materials, ceramic cutters and the like.

Drawings

FIG. 1 is an X-ray diffraction pattern of a high-entropy diboride-boron carbide complex phase ceramic in examples 1, 2 and 3;

FIG. 2 is a scanning electron micrograph of a high-entropy diboride-boron carbide complex phase ceramic and a corresponding region of the high-entropy diboride-boron carbide complex phase ceramic in example 2;

FIG. 3 is a scanning electron micrograph of the indentation crack propagation path of the high-entropy diboride-boron carbide complex phase ceramic in example 1.

Detailed Description

The above and further features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

Example 1

The raw materials have the following mole parts: 1 part of titanium carbide, 1 part of zirconium carbide, 1 part of hafnium carbide, 1 part of niobium carbide, 1 part of tantalum carbide and 32 parts of boron powder. The preparation process comprises the following steps: (1) putting carbide powder and boron powder into a polyethylene bottle, adding zirconia grinding balls and absolute ethyl alcohol, and carrying out ball milling and mixing for 24 hours; (2) evaporating the mixed slurry on a rotary evaporator to dryness, and then putting the dried slurry into an air-blowing drying oven to dry for 24 hours at the temperature of 80 ℃; (3) sieving the dried powder through a standard sieve of 200 meshes; (4) loading the sieved powder into a graphite die, heating to 2000 ℃ at a speed of 100 ℃/min in a discharge plasma sintering furnace, simultaneously pressurizing to 40MPa, carrying out vacuum sintering for 6 minutes, and then cooling and decompressing; (5) and (4) demolding, and taking out the sintered ceramic sample.

The X-ray diffraction pattern of the obtained in-situ authigenic high-entropy diboride-boron carbide complex phase ceramic is shown in figure 1a, wherein the main phases comprise high-entropy diboride and boron carbide. The density of the complex phase ceramic is 4.9g/cm³The Vickers hardness (Hv5) is 20.65 +/-1.83 GPa, the bending strength is 422 +/-48 MPa, and the fracture toughness is 5.48 +/-0.50 MPa m^1/2. As shown in figure 3, submicron-grade high-entropy diboride and boron carbide grains in the material have the effects of deflecting and branching cracks, and are beneficial to improving the fracture toughness. For comparison, the single-phase diboride high-entropy ceramic material prepared by adopting boron-carbon thermal reduction powder preparation and combining with an SPS sintering method has the density of 8.2g/cm³The Vickers hardness (Hv5) is 19.44 +/-0.50 GPa, and the fracture toughness is 2.83 +/-0.15 MPa m^1/2. The data show that the in-situ synthesized high-entropy diboride-boron carbide complex phase ceramic prepared by the invention has lower density, higher Vickers hardness, bending strength and fracture toughness.

Example 2

The raw materials have the following mole parts: 1 part of titanium carbide, 1 part of zirconium carbide, 1 part of hafnium carbide, 1 part of niobium carbide, 1 part of tantalum carbide, 1 part of vanadium carbide and 38.5 parts of boron powder. The preparation process is the same as that of example 1 and is not repeated herein.

The X-ray diffraction pattern of the obtained in-situ authigenic high-entropy diboride-boron carbide complex phase ceramic is shown in figure 1b, and the main phases comprise high-entropy diboride and boron carbide. The grain size of high-entropy diboride and boron carbide in the complex phase ceramic is about 1 mu m, and all metal elements in the high-entropy phase are uniformly distributed (figure 2). The Vickers hardness (Hv5) of the complex phase ceramic is 21.3 +/-0.8 GPa, the bending strength is 478 +/-49 MPa, and the fracture toughness is 5.80 +/-0.55 MPa m^1/2。

Example 3

The weight portions of the raw materials are as follows: 1 part of titanium carbide, 1 part of zirconium carbide, 1 part of hafnium carbide, 1 part of niobium carbide, 1 part of tantalum carbide, 0.25 part of tungsten carbide and 33.6 parts of boron powder. The preparation process is the same as that of example 1 and is not repeated herein.

The X-ray diffraction pattern of the obtained in-situ autogenous high-entropy diboride-boron carbide complex phase ceramic is shown in figure 1c, and the main phases comprise the high-entropy diboride and the boron carbide. The Vickers hardness (Hv5) of the complex phase ceramic is 20.9 +/-0.5 GPa, the bending strength is 561 +/-72 MPa, and the fracture toughness is 4.45 +/-0.61 MPa m^1/2。

The foregoing is merely a preferred embodiment of the invention, which is intended to be illustrative and not limiting. It will be understood by those skilled in the art that various changes, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.