High-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus and preparation method of high-entropy carbonitride ceramic

Abstract

The invention relates to high-entropy carbonitride ceramic with controllable carbon nitrogen ratio, high hardness and high elastic modulus and a preparation method of the high-entropy carbonitride ceramic, and belongs to the technical field of high-entropy ceramics. In order to solve the problem that the existing preparation method is difficult to consider the regulation and control of the carbon nitrogen ratio and the mechanical property of the high-entropy carbonitride ceramic at the same time, the preparation method comprises the following steps: carrying out ball milling and drying on Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black to obtain mixed powder; performing heat treatment on the mixed powder in a nitrogen atmosphere to obtain ceramic powder; and carrying out spark plasma sintering on the ceramic powder to obtain the high-entropy carbonitride ceramic. The carbon vacancy concentration of a high-entropy system is regulated and controlled by adjusting the molar ratio of the metal powder to the carbon black, then introduction of nitrogen atoms is achieved, the carbon-nitrogen ratio of the ceramic powder is easier to regulate and control, grain growth can be effectively avoided through spark plasma sintering, the compact fine-grain high-entropy carbonitride ceramic can be obtained within a short time, and the high-entropy carbonitride ceramic has a good application prospect. The improvement of the mechanical property of the high-entropy carbonitride ceramic is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of high entropy ceramics, relates to a method for manufacturing special ceramic products, and specifically relates to a high entropy carbonitride ceramic with a controllable carbon-nitrogen ratio, high hardness and high elastic modulus, and a preparation method thereof. Background Art

[0002] Compared with traditional binary ceramics, high entropy ceramics have better antioxidant properties, mechanical properties and thermophysical properties, and have become a hot topic of research at home and abroad in recent years. At present, research at home and abroad is mainly focused on single anion high entropy ceramics such as borides, carbides, and nitrides. Compared with single anion high entropy ceramics, multi-anion high entropy ceramics have a relatively higher configurational entropy due to the increase in the number of anions, showing a broader performance regulation space and designability. Among them, high entropy carbonitrides are easier to synthesize than high entropy borocarbides because the corresponding single anion high entropy ceramics have the same face-centered cubic crystal structure, and are more outstanding in mechanical properties. They have great application prospects in the field of ultra-high temperature thermal protection.

[0003] The carbon-nitrogen ratio of high-entropy carbonitrides has an important influence on the composition, structure and properties of ceramics. For example, as the carbon-nitrogen ratio increases, the hardness and modulus increase, and the fracture toughness decreases. Therefore, it is of great significance to explore the preparation method of ceramics with easy-to-control carbon-nitrogen ratio. The synthesis methods of high-entropy carbonitride ceramic powders mainly include carbon thermal reduction-nitridation method, sol-gel-nitridation method, mechanical alloying-nitridation method and solid solution reaction method. The carbon-nitrogen ratio is difficult to control by the carbon thermal reduction-nitridation method using metal oxides, carbon black and nitrogen as starting materials and the sol-gel-nitridation method using metal oxides, metal chlorides or metal salts as metal sources, carbon black or organic matter as carbon sources, and nitrogen as nitrogen sources. The mechanical alloying-nitridation method using metal element, carbon black and nitrogen as starting materials and the solid solution reaction method using single component metal carbide and metal nitride as starting materials are easier to control the carbon-nitrogen ratio. Compared with the solid solution reaction method, the mechanical alloying-nitridation method has a lower cost, but the ceramic powder synthesized by this method has a larger particle size, which will have an adverse effect on the sintering performance of the ceramic. The particle size of the powder can be reduced by reducing the heat treatment temperature of the ceramic powder, but it is not conducive to the solid solution of the ceramic powder phase, and has an adverse effect on the chemical stability and density of the ceramic. Summary of the invention

[0004] In order to solve the problem that the existing preparation method is difficult to balance the carbon-nitrogen ratio regulation and the mechanical properties of high-entropy carbonitride ceramics, the present invention provides a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus and a preparation method thereof.

[0005] The technical solution of the present invention:

[0006] A method for preparing high-entropy carbonitride ceramics with controllable carbon-nitrogen ratio, high hardness and high elastic modulus, comprising: ball-milling and drying Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black according to a certain molar ratio to obtain a mixed powder; heat-treating the mixed powder in a nitrogen atmosphere to obtain ceramic powder; and spark plasma sintering the ceramic powder to obtain a high-entropy carbonitride ceramic.

[0007] Furthermore, the molar ratio of the Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black is 2:(2-4):(2-4):(0.5-1.5):(0.5-1.5):(5-9).

[0008] Furthermore, the particle sizes of the Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder are all 5-10 μm, the particle size of the carbon black is 1-3 μm, and the purity of the Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black is higher than 99.5%.

[0009] Furthermore, the medium of the mixed ball milling is alcohol, the ball-to-material ratio is 4-6:1, the ball milling speed is 200-300 r / min, and the ball milling time is 20-30 h.

[0010] Furthermore, the drying temperature is 80-100° C., and the drying time is 6-8 hours.

[0011] Furthermore, the heat treatment is performed by heating the temperature to 1500-1600°C at a heating rate of 3-5°C / min, keeping the temperature for 1-2h, and then cooling the temperature to room temperature at a cooling rate of 3-5°C / min.

[0012] Furthermore, the particle size of the ceramic powder is 3 to 7 μm.

[0013] Furthermore, the spark plasma sintering is carried out under vacuum conditions, heating to 1800-1900°C at a heating rate of 80-100°C / min, keeping the temperature for 10-15min, cooling to 200-300°C at a cooling rate of 10-20°C / min, and then naturally cooling to room temperature. The sintering pressure is 30-40MPa.

[0014] Furthermore, the spark plasma sintering is carried out under vacuum conditions, heating to 1700-1750°C at a heating rate of 80-100°C / min, keeping warm for 5-10 minutes, then heating to 1800-1900°C at a heating rate of 80-100°C / min, keeping warm for 5-10 minutes, cooling to 200-300°C at a cooling rate of 10-20°C / min, and then naturally cooling to room temperature. The sintering pressure is 30-40MPa.

[0015] A high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus prepared by the preparation method provided by the present invention, wherein the grain size of the high-entropy carbonitride ceramic is 2-3 μm.

[0016] Beneficial effects of the present invention:

[0017] The preparation method of high entropy carbonitride ceramics provided by the present invention uses metal element powder and metal hydride powder as metal sources, carbon black as carbon source, and nitrogen as nitrogen source, and utilizes the exothermic reaction of metal element powder and carbon black at high temperature combined with nitriding heat treatment to synthesize ceramic powder. The present invention adjusts the molar ratio of metal powder to carbon black to regulate the carbon vacancy concentration of the high entropy system, thereby realizing the introduction of nitrogen atoms, and making it easier to regulate the carbon-nitrogen ratio of the ceramic powder. The present invention utilizes spark plasma sintering to realize further solid solution of ceramic powder and preparation of high entropy carbonitride ceramics, which can effectively avoid grain growth, obtain dense and fine-grained high entropy carbonitride ceramics in a relatively short time, and is conducive to the improvement of the mechanical properties of high entropy carbonitride ceramics. The Vickers hardness of the high entropy carbonitride ceramics prepared by the present invention is 20.12-22.04 GPa, and the elastic modulus is 479-510 GPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the XRD pattern of the high entropy carbonitride ceramic prepared in Example 3;

[0019] Figure 2 This is a SEM image of the fracture surface of the high entropy carbonitride ceramic prepared in Example 3;

[0020] Figure 3 This is a SEM image of the ceramic powder corresponding to the high entropy carbonitride ceramic prepared in Example 3;

[0021] Figure 4 This is a comparison chart of the carbon-nitrogen ratio, Vickers hardness and elastic modulus of the high entropy carbonitride ceramics prepared in Examples 1 to 7. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with the embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention. The process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art. If not specifically specified, the raw materials used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0023] Example 1

[0024] The present embodiment provides a method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus. The carbon-nitrogen ratio of the high-entropy carbonitride ceramic in the present embodiment is 2.75.

[0025] In this embodiment, high entropy carbonitride ceramics are prepared according to the following steps:

[0026] Step 1: Mix raw material powder:

[0027] The raw material powders used in this embodiment are Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder with a particle size distribution of 5 to 10 μm and a purity higher than 99.5%, and carbon black with a particle size distribution of 1 to 3 μm and a purity higher than 99.5%.

[0028] The raw material powders were mixed in a molar ratio of 2:2:2:0.5:0.5:5 for Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black. The mixing method was ball milling. The ball milling medium was alcohol. The ball-to-material ratio was 4:1. The ball milling speed was 240 r / min. The ball milling time was 30 h. After ball milling, the powders were collected and placed in a vacuum drying oven. They were dried at 80° C. for 8 h to obtain mixed powders.

[0029] Step 2: Synthesize ceramic powder:

[0030] The mixed powder obtained in step 1 is placed in a nitrogen atmosphere for heat treatment, the temperature is increased to 1500°C at a heating rate of 5°C / min and kept at this temperature for 2h, and then the temperature is cooled to room temperature at a cooling rate of 5°C / min. The heat-treated powder is ground to obtain a ceramic powder with a particle size of 4.46±1.33μm.

[0031] Step 3: Preparation of high entropy carbonitride ceramics:

[0032] The ceramic powder obtained in step 2 is placed in a graphite mold with good thermal conductivity and lined with graphite paper, and spark plasma sintering is carried out under vacuum conditions. The sintering pressure is 30 MPa, and the temperature is increased to 1720°C at a heating rate of 80°C / min and kept at this temperature for 7 minutes, then increased to 1820°C at a heating rate of 100°C / min and kept at this temperature for 8 minutes, then cooled to 250°C at a cooling rate of 20°C / min, and finally naturally cooled to room temperature to obtain a high entropy carbonitride ceramic with a grain size of 2.29±0.69μm.

[0033] Example 2

[0034] The present embodiment provides a method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus. The carbon-nitrogen ratio of the high-entropy carbonitride ceramic in the present embodiment is 2.92.

[0035] In this embodiment, high entropy carbonitride ceramics are prepared according to the following steps:

[0036] Step 1: Mix raw material powder:

[0037] The raw material powders used in this embodiment are Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder with a particle size distribution of 5 to 10 μm and a purity higher than 99.5%, and carbon black with a particle size distribution of 1 to 3 μm and a purity higher than 99.5%.

[0038] The raw material powders were mixed in a molar ratio of 2:2.5:2.5:0.75:0.75:6 for Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black. The mixing method was ball milling. The ball milling medium was alcohol. The ball-to-material ratio was 6:1. The ball milling speed was 300 r / min. The ball milling time was 25 h. After ball milling, the powders were collected and placed in a vacuum drying oven. They were dried at 100 ° C for 6 h to obtain mixed powders.

[0039] Step 2: Synthesize ceramic powder:

[0040] The mixed powder obtained in step 1 is placed in a nitrogen atmosphere for heat treatment, the temperature is increased to 1550°C at a heating rate of 3°C / min and kept at this temperature for 2 hours, and then the temperature is cooled to room temperature at a cooling rate of 3°C / min. The heat-treated powder is ground to obtain a ceramic powder with a particle size of 4.41±1.39μm.

[0041] Step 3: Preparation of high entropy carbonitride ceramics:

[0042] The ceramic powder obtained in step 2 is placed in a graphite mold with good thermal conductivity and lined with graphite paper, and spark plasma sintering is carried out under vacuum conditions. The sintering pressure is 40 MPa, and the temperature is increased to 1750°C at a heating rate of 100°C / min and kept for 7 minutes, then increased to 1850°C at a heating rate of 100°C / min and kept for 8 minutes, then cooled to 300°C at a cooling rate of 15°C / min, and finally naturally cooled to room temperature to obtain a high entropy carbonitride ceramic with a grain size of 2.38±0.65μm.

[0043] Example 3

[0044] The present embodiment provides a method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus. The carbon-nitrogen ratio of the high-entropy carbonitride ceramic in the present embodiment is 2.87.

[0045] In this embodiment, high entropy carbonitride ceramics are prepared according to the following steps:

[0046] Step 1: Mix raw material powder:

[0047] The raw material powders used in this embodiment are Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder with a particle size distribution of 5 to 10 μm and a purity higher than 99.5%, and carbon black with a particle size distribution of 1 to 3 μm and a purity higher than 99.5%.

[0048] The raw material powders were mixed in a molar ratio of 2:3:3:1:1:7 for Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black. The mixing method was ball milling. The ball milling medium was alcohol. The ball-to-material ratio was 5:1. The ball milling speed was 280 r / min. The ball milling time was 24 h. After ball milling, the powders were collected and placed in a vacuum drying oven. They were dried at 90 ° C for 7 h to obtain mixed powders.

[0049] Step 2: Synthesize ceramic powder:

[0050] The mixed powder obtained in step 1 is placed in a nitrogen atmosphere for heat treatment, the temperature is increased to 1550°C at a heating rate of 5°C / min and kept at this temperature for 2h, and then the temperature is cooled to room temperature at a cooling rate of 3°C / min. The heat-treated powder is ground to obtain a ceramic powder with a particle size of 4.34±1.31μm.

[0051] Step 3: Preparation of high entropy carbonitride ceramics:

[0052] The ceramic powder obtained in step 2 is placed in a graphite mold with good thermal conductivity and lined with graphite paper, and spark plasma sintering is carried out under vacuum conditions. The sintering pressure is 35 MPa, and the temperature is increased to 1750°C at a heating rate of 100°C / min and kept at this temperature for 7 minutes, then increased to 1850°C at a heating rate of 80°C / min and kept at this temperature for 8 minutes, then cooled to 250°C at a cooling rate of 12°C / min, and finally naturally cooled to room temperature to obtain a high entropy carbonitride ceramic with a grain size of 2.26±0.63μm.

[0053] Example 4

[0054] The present embodiment provides a method for preparing a high-entropy carbonitride ceramic with high hardness and high elastic modulus and a controllable carbon-nitrogen ratio. The carbon-nitrogen ratio of the high-entropy carbonitride ceramic in the present embodiment is 2.81.

[0055] In this embodiment, high entropy carbonitride ceramics are prepared according to the following steps:

[0056] Step 1: Mix raw material powder:

[0057] The raw material powders used in this embodiment are Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder with a particle size distribution of 5 to 10 μm and a purity higher than 99.5%, and carbon black with a particle size distribution of 1 to 3 μm and a purity higher than 99.5%.

[0058] The raw material powders were mixed according to the molar ratio of Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black of 2:3.5:3.5:1.25:1.25:8, the mixing method was ball milling, the ball milling medium was alcohol, the ball-to-material ratio was 6:1, the ball milling speed was 300r / min, and the ball milling time was 20h. After ball milling, the powders were collected and placed in a vacuum drying oven, and dried at 90°C for 8h to obtain mixed powders.

[0059] Step 2: Synthesize ceramic powder:

[0060] The mixed powder obtained in step 1 is placed in a nitrogen atmosphere for heat treatment, the temperature is increased to 1580°C at a heating rate of 5°C / min and kept at this temperature for 1h, and then the temperature is cooled to room temperature at a cooling rate of 3°C / min. The heat-treated powder is ground to obtain a ceramic powder with a particle size of 4.17±1.25μm.

[0061] Step 3: Preparation of high entropy carbonitride ceramics:

[0062] The ceramic powder obtained in step 2 is placed in a graphite mold with good thermal conductivity and lined with graphite paper, and spark plasma sintering is carried out under vacuum conditions. The sintering pressure is 40 MPa, and the temperature is increased to 1850°C at a heating rate of 100°C / min and kept for 10 minutes, then cooled to 200°C at a cooling rate of 15°C / min, and finally naturally cooled to room temperature to obtain high entropy carbonitride ceramics with a grain size of 2.34±0.73μm.

[0063] Example 5

[0064] The present embodiment provides a method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus. The carbon-nitrogen ratio of the high-entropy carbonitride ceramic in the present embodiment is 2.89.

[0065] In this embodiment, high entropy carbonitride ceramics are prepared according to the following steps:

[0066] Step 1: Mix raw material powder:

[0067] The raw material powders used in this embodiment are Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder with a particle size distribution of 5 to 10 μm and a purity higher than 99.5%, and carbon black with a particle size distribution of 1 to 3 μm and a purity higher than 99.5%.

[0068] The raw material powders were mixed according to the molar ratio of Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black of 2:4:4:1.5:1.5:9, the mixing method was ball milling, the ball milling medium was alcohol, the ball-to-material ratio was 5:1, the ball milling speed was 280r / min, and the ball milling time was 25h. After ball milling, the powders were collected and placed in a vacuum drying oven, and dried at 100°C for 6h to obtain mixed powders.

[0069] Step 2: Synthesize ceramic powder:

[0070] The mixed powder obtained in step 1 is placed in a nitrogen atmosphere for heat treatment, the temperature is increased to 1550°C at a heating rate of 3°C / min and kept at this temperature for 2h, and then the temperature is cooled to room temperature at a cooling rate of 5°C / min. The heat-treated powder is ground to obtain a ceramic powder with a particle size of 4.31±1.26μm.

[0071] Step 3: Preparation of high entropy carbonitride ceramics:

[0072] The ceramic powder obtained in step 2 is placed in a graphite mold with good thermal conductivity and lined with graphite paper, and spark plasma sintering is carried out under vacuum conditions. The sintering pressure is 30 MPa, and the temperature is increased to 1750°C at a heating rate of 90°C / min and kept for 10 min, then increased to 1850°C at a heating rate of 100°C / min and kept for 5 min, then cooled to 300°C at a cooling rate of 10°C / min, and finally naturally cooled to room temperature to obtain a high entropy carbonitride ceramic with a grain size of 2.25±0.66 μm.

[0073] Example 6

[0074] The present embodiment provides a method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus. The carbon-nitrogen ratio of the high-entropy carbonitride ceramic in the present embodiment is 2.27.

[0075] In this embodiment, high entropy carbonitride ceramics are prepared according to the following steps:

[0076] Step 1: Mix raw material powder:

[0077] The raw material powders used in this embodiment are Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder with a particle size distribution of 5 to 10 μm and a purity higher than 99.5%, and carbon black with a particle size distribution of 1 to 3 μm and a purity higher than 99.5%.

[0078] The raw material powders were mixed in a molar ratio of 2:3:3:1:1:6 for Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black, and the mixing method was ball milling, the ball milling medium was alcohol, the ball-to-material ratio was 6:1, the ball milling speed was 300r / min, and the ball milling time was 20h. After ball milling, the powders were collected and placed in a vacuum drying oven, and dried at 80°C for 8h to obtain mixed powders.

[0079] Step 2: Synthesize ceramic powder:

[0080] The mixed powder obtained in step 1 is placed in a nitrogen atmosphere for heat treatment, the temperature is increased to 1580°C at a heating rate of 5°C / min and kept at this temperature for 2 hours, and then the temperature is cooled to room temperature at a cooling rate of 3°C / min. The heat-treated powder is ground to obtain a ceramic powder with a particle size of 3.91±1.21μm.

[0081] Step 3: Preparation of high entropy carbonitride ceramics:

[0082] The ceramic powder obtained in step 2 is placed in a graphite mold with good thermal conductivity and lined with graphite paper, and spark plasma sintering is carried out under vacuum conditions. The sintering pressure is 40 MPa, and the temperature is increased to 1900°C at a heating rate of 100°C / min and kept for 15 minutes, then cooled to 250°C at a cooling rate of 15°C / min, and finally naturally cooled to room temperature to obtain a high-entropy carbonitride ceramic with a grain size of 2.40±0.71μm.

[0083] Example 7

[0084] The present embodiment provides a method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus. The carbon-nitrogen ratio of the high-entropy carbonitride ceramic in the present embodiment is 4.35.

[0085] In this embodiment, high entropy carbonitride ceramics are prepared according to the following steps:

[0086] Step 1: Mix raw material powder:

[0087] The raw material powders used in this embodiment are Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder with a particle size distribution of 5 to 10 μm and a purity higher than 99.5%, and carbon black with a particle size distribution of 1 to 3 μm and a purity higher than 99.5%.

[0088] The raw material powders were mixed according to the molar ratio of Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black of 2:3:3:1:1:8, and the mixing method was ball milling, the ball milling medium was alcohol, the ball-to-material ratio was 5:1, the ball milling speed was 250r / min, and the ball milling time was 24h. After ball milling, the powders were collected and placed in a vacuum drying oven, and dried at 80°C for 8h to obtain mixed powders.

[0089] Step 2: Synthesize ceramic powder:

[0090] The mixed powder obtained in step 1 is placed in a nitrogen atmosphere for heat treatment, the temperature is increased to 1550°C at a heating rate of 5°C / min and kept at this temperature for 2h, and then the temperature is cooled to room temperature at a cooling rate of 3°C / min. The heat-treated powder is ground to obtain a ceramic powder with a particle size of 4.96±1.42μm.

[0091] Step 3: Preparation of high entropy carbonitride ceramics:

[0092] The ceramic powder obtained in step 2 is placed in a graphite mold with good thermal conductivity and lined with graphite paper, and spark plasma sintering is carried out under vacuum conditions. The sintering pressure is 40 MPa, and the temperature is increased to 1900°C at a heating rate of 100°C / min and kept for 10 minutes, then cooled to 250°C at a cooling rate of 15°C / min, and finally naturally cooled to room temperature to obtain a high-entropy carbonitride ceramic with a grain size of 2.35±0.68μm.

[0093] Figure 1 The XRD pattern (X-ray diffraction pattern) of the high entropy carbonitride ceramic prepared in Example 3; Figure 1 It can be seen that the ceramic is composed of a single (Ti, Zr, Hf, Ta, Cr)CN solid solution phase, and no other phases or oxide phases were found.

[0094] Figure 2 The SEM image (scanning electron micrograph) of the fracture surface of the high entropy carbonitride ceramic prepared in Example 3 is shown in FIG.

[0095] Figure 3 The SEM image of the ceramic powder corresponding to the high entropy carbonitride ceramic prepared in Example 3; Figure 2 and Figure 3 By comparison, the grain size of the high-entropy carbonitride ceramic is smaller than that of the corresponding ceramic powder. Thanks to the rapid densification of spark plasma sintering, the grain growth is better suppressed.

[0096] Figure 4 is a comparison chart of the carbon-nitrogen ratio, Vickers hardness and elastic modulus of the high entropy carbonitride ceramics prepared in Examples 1 to 7, Figure 4 It can be seen that the (Ti, Zr, Hf, Ta, Cr)CN high entropy carbonitride ceramics prepared in all embodiments have high Vickers hardness and elastic modulus. At the same time, by adjusting the molar ratio of metal powder to carbon black, the carbon-nitrogen ratio of the (Ti, Zr, Hf, Ta, Cr)CN high entropy carbonitride ceramics can be effectively regulated.

Claims

1. A method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus, characterized in that: Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black are ball-milled and dried according to a certain molar ratio to obtain a mixed powder; the mixed powder is placed in a nitrogen atmosphere for heat treatment to obtain a ceramic powder; the ceramic powder is subjected to spark plasma sintering to obtain a high entropy carbonitride ceramic.

2. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 1, characterized in that: The molar ratio of the Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black is 2:(2-4):(2-4):(0.5-1.5):(0.5-1.5):(5-9).

3. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 1 or 2, characterized in that: The particle sizes of the Ti powder, ZrH2 powder, Hf powder, Ta powder and Cr powder are all 5-10 μm, the particle size of the carbon black is 1-3 μm, and the purity of the Ti powder, ZrH2 powder, Hf powder, Ta powder, Cr powder and carbon black is higher than 99.5%.

4. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 3, characterized in that: The medium of the mixed ball milling is alcohol, the ball-to-material ratio is 4-6:1, the ball milling speed is 200-300 r / min, and the ball milling time is 20-30 hours.

5. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 4, characterized in that: The drying temperature is 80-100° C. and the drying time is 6-8 hours.

6. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 5, characterized in that: The heat treatment comprises heating the temperature to 1500-1600° C. at a heating rate of 3-5° C. / min, keeping the temperature for 1-2 hours, and then cooling the temperature to room temperature at a cooling rate of 3-5° C. / min.

7. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 6, characterized in that: The particle size of the ceramic powder is 3-7 μm.

8. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 7, characterized in that: The spark plasma sintering is carried out under vacuum conditions, heating to 1800-1900°C at a heating rate of 80-100°C / min, keeping the temperature for 10-15min, cooling to 200-300°C at a cooling rate of 10-20°C / min, and then naturally cooling to room temperature. The sintering pressure is 30-40MPa.

9. The method for preparing a high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus according to claim 7, characterized in that: The spark plasma sintering is carried out under vacuum conditions, heating to 1700-1750°C at a heating rate of 80-100°C / min, keeping the temperature for 5-10 minutes, then heating to 1800-1900°C at a heating rate of 80-100°C / min, keeping the temperature for 5-10 minutes, cooling to 200-300°C at a cooling rate of 10-20°C / min, and then naturally cooling to room temperature. The sintering pressure is 30-40MPa.

10. A high-entropy carbonitride ceramic with controllable carbon-nitrogen ratio, high hardness and high elastic modulus prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The grain size of the high entropy carbonitride ceramic is 2-3 μm.

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