Aluminum-containing high-entropy carbonitride ceramic and method of making the same

Abstract

The application discloses a kind of aluminum-containing high-entropy carbonitride ceramics and preparation method thereof, the aluminum-containing high-entropy carbonitride ceramic is by high-entropy carbonitride ceramic matrix and AlN particle dispersed distribution in high-entropy carbonitride ceramic matrix, Al is contained in the high-entropy carbonitride ceramic matrix, the high-entropy carbonitride ceramic provided by the application, Al is contained in high-entropy carbonitride ceramic matrix, while also containing in-situ generated AlN second phase particle, Al and in-situ generated AlN particle respectively utilize solid solution strengthening and second phase strengthening to improve the mechanical properties of high-entropy ceramic, while the formation of aluminum oxide in oxidation process improves the oxidation resistance of high-entropy ceramic, so that the aluminum-containing high-entropy carbonitride ceramic provided by the application has good mechanical properties and excellent oxidation resistance.

Description

Technical Field

[0001] This invention relates to an aluminum-containing high-entropy carbonitride ceramic and its preparation method; it belongs to the field of high-entropy ceramic material preparation technology. Background Technology

[0002] In 2004, researchers proposed the material design concept of "multi-principal element alloys," later known as "high-entropy alloys," which consist of five or more elements with atomic fractions controlled between 5% and 35%. With in-depth interdisciplinary research, the high-entropy design concept has gradually expanded to ceramic materials, leading to the development and design of a series of high-entropy ceramics. Following the initial high-entropy oxide ceramics, research focus gradually shifted to high-entropy carbides, which possess excellent hardness and wear resistance. High-entropy carbides with a NaCl crystal structure have Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W elements from groups IVB, VB, and VIB occupying cation sites, and C occupying anion sites. Subsequently, by introducing nitrogen (N) elements into the anion sites of high-entropy carbides, high-entropy carbonitride ceramics were further developed, exhibiting improved strength, toughness, and wear resistance compared to carbides. However, the oxidation resistance of such high-entropy carbide / carbonitride ceramic materials needs to be improved under high-temperature conditions, which seriously limits the expansion of the application fields of high-entropy ceramics with ultra-high melting points. Therefore, while ensuring mechanical properties, it is very important to improve the oxidation resistance of high-entropy carbonitride ceramics themselves.

[0003] The elemental composition of high-entropy carbonitrides is relatively fixed. The cation-occupying metals are selected from nine elements in groups IVB, VB, and VIB. The properties of high-entropy ceramics can be controlled by adjusting the composition and microstructure. Patent CN202311449160.X prepared (TiCrVNbTa)(CN) using high-energy ball milling and high-temperature, high-pressure sintering. Furthermore, as described in patent CN202310151143.1, SiC can be added to high-entropy ceramics to improve material properties. However, directly adding a second phase is not conducive to the overall improvement of material properties due to interface issues. Summary of the Invention

[0004] In view of the problem that it is not easy to achieve a synergistic improvement effect on the mechanical properties and oxidation resistance of high-entropy carbonitride ceramics in the prior art, the first objective of the present invention is to provide an aluminum-containing high-entropy carbonitride ceramic with both good mechanical properties and excellent oxidation resistance. In the present invention, the lattice distortion and high-entropy effect brought about by the multi-component metal atoms in the carbonitride are used to promote the solid solution of Al into the carbonitride.

[0005] The second objective of this invention is to provide a method for preparing aluminum-containing high-entropy carbonitride ceramics.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The present invention discloses an aluminum-containing high-entropy carbonitride ceramic, which is composed of a high-entropy carbonitride ceramic matrix and AlN particles dispersed in the high-entropy carbonitride ceramic matrix, wherein the high-entropy carbonitride ceramic matrix contains Al.

[0008] The high-entropy carbonitride ceramic provided by this invention contains Al in its matrix and also contains in-situ generated AlN second-phase particles. The Al and the in-situ generated AlN particles are strengthened by solid solution and strengthened by the second phase to improve the mechanical properties of the high-entropy ceramic, respectively. At the same time, the formation of aluminum oxide during the oxidation process improves the oxidation resistance of the high-entropy ceramic. Thus, the aluminum-containing high-entropy carbonitride ceramic provided by this invention has both good mechanical properties and excellent oxidation resistance.

[0009] In a preferred embodiment, the atomic percentage of aluminum in the high-entropy carbonitride ceramic is 1–4 at.%, preferably 1–3 at.%, and more preferably 2–3 at.%. In this invention, controlling the atomic percentage of aluminum within the above range allows for the simultaneous improvement of the mechanical properties and oxidation resistance of the aluminum-containing high-entropy carbonitride ceramic. Excessive addition, however, will cause a decrease in hardness.

[0010] In a preferred embodiment, the high-entropy carbonitride ceramic matrix further contains transition metal elements, carbon and nitrogen, wherein the transition metal elements are selected from any five of Ti, V, Zr, Nb, Mo, Hf, Ta, and Cr, and the atomic percentage of the transition metal elements in the high-entropy carbonitride ceramic is 46–49 at.%, the atomic percentage of carbon in the high-entropy carbonitride ceramic is 30–70 at.%, and the atomic percentage of nitrogen in the high-entropy carbonitride ceramic matrix is ​​30–70 at.%.

[0011] This invention discloses a method for preparing aluminum-containing high-entropy carbonitride ceramics, characterized in that: oxides corresponding to transition metal elements, nano-alumina, and carbon black are selected according to a designed ratio and mixed to obtain a mixed powder; the mixed powder is subjected to an in-situ carbothermic reduction nitridation reaction in a nitrogen atmosphere to obtain aluminum-containing high-entropy carbonitride ceramic powder; and the high-entropy carbonitride ceramic powder is then subjected to spark plasma sintering to obtain aluminum-containing high-entropy carbonitride ceramics.

[0012] In the preparation method of this invention, through the carbothermic reduction nitridation synthesis process of high-entropy carbonitride ceramics using IVB, VB, VIB group metals, aluminum oxides, and carbon black, a portion of Al enters the crystal structure of the high-entropy carbonitride ceramic, while a portion of Al reacts with N to form AlN particles in situ. The Al in the high-entropy carbonitride ceramic and the in-situ generated AlN particles can enhance the mechanical properties of the high-entropy ceramic through solid solution strengthening and second-phase strengthening, while also improving the oxidation resistance of the high-entropy ceramic.

[0013] In a preferred embodiment, the average particle size of the oxides corresponding to the transition metal elements is 0.2–10 μm, the average particle size of alumina is 0.04–0.08 μm, and the average particle size of carbon black is 0.1–2 μm.

[0014] The inventors discovered that the choice of raw material particle size affects the size and distribution of AlN particles generated in situ. The average particle size of alumina needs to be significantly lower than that of transition metal oxides in order to form diffusely distributed AlN particles. If the average particle size of alumina is close to or larger than that of transition metal oxides, coarse AlN particles will appear, thereby damaging the material properties.

[0015] In a preferred embodiment, the total mass fraction of oxides corresponding to transition metal elements in the mixed powder is 77.92–79.41 wt.%, the mass fraction of alumina is 0.32–1.28 wt.%, and the mass fraction of carbon black is 15–25 wt.%.

[0016] In the actual exploration process of this invention, by designing the aluminum element in the raw material powder to increase in a gradient, the Al content in the high-entropy carbonitride ceramic matrix and the content of in-situ generated AlN particles gradually increase during the in-situ carbothermic reduction nitridation reaction. Thus, by controlling the alumina content in the mixture, the Al content and AlN second-phase particle content in the aluminum-containing high-entropy carbonitride ceramic matrix can be controlled. At the same time, it was found that only by controlling the Al content within the range of this invention can the aluminum-containing high-entropy carbonitride ceramic possess both good mechanical properties and excellent oxidation resistance.

[0017] In a preferred embodiment, the mixing method is ball milling, with a ball-to-material ratio of 3 to 7:1, a ball milling speed of 150 to 300 rpm, and a ball milling time of 24 to 48 hours.

[0018] In a further preferred embodiment, the ball milling is a wet ball milling process, the milling medium is anhydrous ethanol, and the milling direction is forward rotation. In actual operation, the high-energy ball milling mixes the materials to obtain a powder mixture slurry, which is then dried completely in a drying oven to obtain a mixed powder.

[0019] The inventors discovered that ball milling parameters affect the uniformity of powder mixing and thus the uniformity of the powder material. Ball milling at short durations, low ball-to-powder ratios, and low speeds results in insufficient mixing, leading to severe inhomogeneity in the composition of subsequent carbonitride powders. Conversely, ball milling at long durations, high ball-to-powder ratios, and high speeds inevitably introduces impurities from the milling jar and milling balls.

[0020] In a preferred embodiment, during the in-situ carbothermic reduction nitriding reaction, the flow rate of nitrogen gas is 8–12 sccm / g. In this invention, 8–12 sccm / g refers to a nitrogen gas flow rate of 8–12 sccm per gram of mixed powder. The nitrogen flow rate primarily affects the formation of aluminum nitride; a flow rate that is too low is detrimental to aluminum nitride synthesis, while a flow rate that is too high will lead to an increase in the nitrogen content of the high-entropy ceramic matrix, hindering precise composition control.

[0021] In a preferred embodiment, the temperature of the in-situ carbothermal reduction nitriding reaction is 1500–1700°C, and the time of the in-situ carbothermal reduction nitriding reaction is 1–3 h.

[0022] The inventors discovered that the reaction parameters of the in-situ carbothermic reduction nitridation reaction of high-entropy carbonitride powder directly affect the microstructure and properties of the material. Too low a reaction temperature or too short a reaction time will lead to incomplete reaction and uneven element distribution; too high a reaction temperature or too long a reaction time will cause the powder to be too coarse and degrade the properties of the high-entropy ceramic material.

[0023] In actual operation, depending on the condition of the high-entropy carbonitride ceramic powder, it can be appropriately ground before spark plasma sintering.

[0024] In a preferred embodiment, the discharge plasma sintering is carried out under vacuum conditions. The discharge plasma sintering process is as follows: the temperature is raised to 1900-2100℃, preferably 1950-2050℃, at a heating rate of 80-120℃ / min, held for 10-15min, and then cooled to room temperature. The pressure of the discharge plasma sintering is 30-45MPa.

[0025] The inventors discovered that the parameters of spark plasma sintering affect the microstructure and properties of ceramics. Low sintering temperature, short sintering time, and low pressure lead to insufficient density and poor performance of high-entropy ceramics; while high sintering temperature, long sintering time, and high pressure lead to grain coarsening and performance degradation.

[0026] Principles and advantages

[0027] This invention provides an aluminum-containing high-entropy carbonitride ceramic, which is composed of an aluminum-containing high-entropy carbonitride ceramic matrix and AlN particles dispersed within the high-entropy carbonitride ceramic matrix. The Al and in-situ generated AlN particles in the high-entropy carbonitride ceramic enhance the mechanical properties of the high-entropy ceramic through solid solution strengthening and second-phase strengthening, while also improving its oxidation resistance through the formation of aluminum oxides during oxidation.

[0028] This invention employs the aforementioned component ratios and preparation methods, using high-energy ball milling to prepare uniform mixed oxide and carbon black powders. Subsequently, an in-situ carbothermal reduction nitridation reaction is performed to synthesize aluminum-containing high-entropy carbonitride powder. Finally, aluminum-containing high-entropy ceramics are sintered via spark plasma. With the addition of aluminum, by controlling the in-situ carbothermal reduction nitridation reaction, a portion of Al enters the high-entropy carbonitride ceramic lattice structure, while another portion of Al reacts with N to form AlN particles in situ. By varying the aluminum content, the Al content and AlN particle content in the high-entropy ceramic matrix can be controlled, thereby improving the mechanical properties and oxidation resistance of the aluminum-containing high-entropy carbonitride ceramic.

[0029] Compared with conventional methods for preparing high-entropy carbonitride ceramics, this invention has the following advantages:

[0030] 1. This invention utilizes the synergistic carbothermic reduction nitridation reaction of transition metal oxides and alumina to achieve the following: while some Al enters the high-entropy carbonitride ceramic lattice structure, another portion of Al reacts with N in situ to form dispersed AlN particles.

[0031] 2. The Al and in-situ generated AlN particles in high-entropy carbonitride ceramics can improve the mechanical properties of high-entropy ceramics through solid solution strengthening and second-phase strengthening. On the other hand, in a high-temperature oxidation environment, the presence of Al will react with oxygen to form an aluminum-containing oxide layer, which will hinder the oxidation process and improve the high-temperature oxidation resistance of high-entropy carbonitride ceramics.

[0032] In summary, the convenient preparation method adopted in this invention can obtain aluminum-containing high-entropy carbonitride ceramics. With the addition of an appropriate amount of aluminum, the mechanical properties and oxidation resistance of the high-entropy ceramics are superior to those of high-entropy carbonitride ceramics prepared without aluminum, and it has the prospect of industrial-scale production and application. Detailed Implementation

[0033] Comparative Example 1

[0034] Preparation and Properties of High-Entropy Carbonitride Ceramics Without Adding Aluminum

[0035] Step 1: Mixing transition metal oxide powder with carbon powder

[0036] According to the weight ratio of each component oxide powder and the required carbon black powder calculated in the design, 4.90g of TiO2 powder, 13.54g of Ta2O5 powder, 8.15g of Nb2O5 powder, 7.54g of ZrO2 powder, 5.58g of V2O5 powder, and 10.29g of C powder were weighed. The particle size of the oxides corresponding to the transition metal elements was 0.2-10μm, and the particle size of the C powder was 0.3μm. After mixing the powders, they were placed in a ball mill jar, 80ml of anhydrous ethanol was added, and ball milling was carried out for 24h at a ball-to-powder ratio of 5:1 and a ball milling speed of 250 rpm. After the slurry was thoroughly dried, a powder mixture was obtained.

[0037] Step 2: Preparation of aluminum-free high-entropy carbonitride ceramic powder

[0038] The powder mixture obtained in the first step was sieved and placed in a graphite boat. Nitrogen gas at 10 sccm / g was introduced into a tube furnace, and the temperature was raised to 1600℃ and held for 2 hours to carry out an in-situ carbothermic reduction nitridation reaction. The furnace was then cooled to obtain high-entropy carbonitride ceramic powder.

[0039] Step 3: Preparation of aluminum-free high-entropy carbonitride ceramic bulk

[0040] The uniformly mixed high-entropy carbonitride ceramic powder obtained in the second step was sintered into a bulk material by spark plasma sintering. The sintering pressure was 40 MPa, and the material was heated to 2000 °C at a heating rate of 100 °C / min under vacuum conditions. The temperature was held for 10 minutes, and the material was cooled to room temperature in the furnace to obtain the high-entropy carbonitride ceramic bulk material.

[0041] Step 4: Mechanical properties and oxidation resistance of aluminum-free high-entropy carbonitride ceramic bulk materials

[0042] The high-entropy carbonitride ceramic material prepared in this example has a Vickers hardness of H. v The strength of 1.0 is 22.98 GPa, and the fracture toughness is 2.27 MPa / m. 2 After oxidation at 800℃ for 2 hours, the weight gain was 1072.06 × 10⁻⁶. -4 g / cm 2 .

[0043] Comparative Example 2

[0044] The synthesis conditions of the high-entropy carbonitride powder were the same as those of Comparative Example 1. After obtaining aluminum-free high-entropy carbonitride powder, aluminum powder was added and ball-milled with it. Then, the same discharge plasma sintering as that of Comparative Example 1 was carried out. It was found that due to the low melting point of Al, the Al that melted under pressure was squeezed out of the powder gaps and evaporated. No Al was found in the high-entropy ceramic.

[0045] Comparative Example 3

[0046] According to the weight ratio of each component oxide powder and the required carbon black powder calculated by the design, the five transition metal carbonitrides have the same atomic percentage of 19.8%, while the atomic percentage of aluminum is 1%. After adding 1% aluminum, 4.88g of TiO2 powder, 13.48g of Ta2O5 powder, 8.11g of Nb2O5 powder, 7.50g of ZrO2 powder, 5.55g of V2O5 powder, 0.16g of Al2O3 powder, and 10.32g of C powder were weighed. The particle size of Al2O3 powder is 1.0μm, the particle size of the oxides corresponding to the transition metal elements is 0.2-10μm, and the particle size of C powder is 0.3μm. Then, the same powder synthesis and spark plasma sintering process as in Comparative Example 1 was carried out. It was found that because the particle size of the added Al2O3 powder was relatively coarse and not significantly smaller than that of the transition metal oxide powder, the AlN particles generated by the reaction were large and not dispersed.

[0047] Example 1

[0048] Step 1: Mixing of transition metal oxide powder, alumina powder, and carbon powder. Based on the calculated weight ratios of each component oxide powder and the required carbon black powder, the five transition metal carbonitrides have the same atomic percentage of 19.8%, while the added aluminum element has an atomic percentage of 1%. Weigh out 4.88g of TiO2 powder, 13.48g of Ta2O5 powder, 8.11g of Nb2O5 powder, 7.50g of ZrO2 powder, and 5.5g of V2O5 powder. 5g of Al2O3 powder, 0.16g of Al2O3 powder, and 10.32g of C powder were mixed. The particle size of Al2O3 powder was 50nm, the particle size of the oxides of transition metal elements was 0.2-10μm, and the particle size of C powder was 0.3μm. The mixed powders were placed in a ball mill jar, 80ml of anhydrous ethanol was added, and the mixture was ball-milled at a ball-to-powder ratio of 5:1 and a ball milling speed of 250 rpm for 24h. After the slurry was thoroughly dried, a powder mixture was obtained.

[0049] Step 2: Preparation of aluminum-containing high-entropy carbonitride ceramic powder

[0050] The powder mixture obtained in the first step was sieved and placed in a graphite boat. Nitrogen gas of 10 sccm / g was introduced into a tube furnace, and the temperature was raised to 1600℃ and held for 2 hours to carry out an in-situ carbothermic reduction nitriding reaction. The furnace was then cooled to obtain aluminum-containing high-entropy carbonitride ceramic powder.

[0051] Step 3: Preparation of aluminum-containing high-entropy carbonitride ceramic bulk

[0052] The uniformly mixed high-entropy carbonitride ceramic powder obtained in the second step was sintered into a bulk material by spark plasma sintering. The sintering pressure was 40 MPa, and the material was heated to 2000°C at a heating rate of 100°C / min under vacuum conditions. The temperature was held for 10 minutes, and the material was cooled to room temperature in the furnace to obtain an aluminum-containing high-entropy carbonitride ceramic bulk material.

[0053] Step 4: Mechanical properties and oxidation resistance of high-entropy carbonitride ceramic bulks

[0054] The Vickers hardness H of the aluminum-containing high-entropy carbonitride ceramic material prepared in this example is... v The strength of 1.0 is 23.86 GPa, and the fracture toughness is 2.70 MPa / m. 2 After oxidation at 800℃ for 2 hours, the weight gain was 868.04*10. -4 g / cm 2 .

[0055] Example 2

[0056] Step 1: Mixing transition metal oxide powder, alumina powder, and carbon powder

[0057] Based on the calculated weight ratio of each component oxide powder and the required carbon black powder, the five transition metal carbonitrides have the same atomic percentage of 19.6%, while the atomic percentage of aluminum is 2%. 4.86g of TiO2 powder, 13.42g of Ta2O5 powder, 8.07g of Nb2O5 powder, 7.47g of ZrO2 powder, 5.52g of V2O5 powder, 0.32g of Al2O3 powder, and 10.35g of C powder were weighed. The particle size of Al2O3 powder was 50nm, the particle size of the oxides corresponding to the transition metal elements was 0.2–10μm, and the particle size of C powder was 0.3μm. After mixing the powders, they were placed in a ball mill jar, 80ml of anhydrous ethanol was added, and ball milling was performed at a ball-to-powder ratio of 5:1 and a speed of 250 rpm for 24 hours using forward high-energy ball milling. After thoroughly drying the slurry, a powder mixture was obtained.

[0058] Step 2: Preparation of aluminum-containing high-entropy carbonitride ceramic powder

[0059] The powder mixture obtained in the first step was sieved and placed in a graphite boat. Nitrogen gas at 10 sccm was introduced into a tube furnace, and the temperature was raised to 1600℃ and held for 2 hours to carry out an in-situ carbothermic reduction nitriding reaction. The furnace was then cooled to obtain aluminum-containing high-entropy carbonitride ceramic powder.

[0060] Step 3: Preparation of aluminum-containing high-entropy carbonitride ceramic bulk

[0061] The uniformly mixed high-entropy carbonitride ceramic powder obtained in the second step was sintered into a bulk material by spark plasma sintering. The sintering pressure was 40 MPa, and the material was heated to 2000°C at a heating rate of 100°C / min under vacuum conditions. The temperature was held for 10 minutes, and the material was cooled to room temperature in the furnace to obtain an aluminum-containing high-entropy carbonitride ceramic bulk material.

[0062] Step 4: Testing the oxidation resistance of aluminum-containing high-entropy carbonitride ceramic bulk materials

[0063] The Vickers hardness H of the aluminum-containing high-entropy carbonitride ceramic material prepared in this example is... v The strength of 1.0 is 23.93 GPa, and the fracture toughness is 2.63 MPa / m. 2 After oxidation at 800℃ for 2 hours, the weight gain was 759.22*10. -4 g / cm 2 .

[0064] Example 3

[0065] Step 1: Mixing transition metal oxide powder, alumina powder, and carbon powder

[0066] Based on the calculated weight ratio of each component oxide powder and the required carbon black powder, the five transition metal carbonitrides have the same atomic percentage of 19.4%, while the atomic percentage of aluminum is 3%. The following powders were weighed: 4.83g TiO2 powder, 13.35g Ta2O5 powder, 8.04g Nb2O5 powder, 7.43g ZrO2 powder, 5.50g V2O5 powder, 0.48g Al2O3 powder, and 10.37g C powder. The particle size of Al2O3 powder is 50nm, the particle size of the oxides corresponding to the transition metal elements is 0.2–10μm, and the particle size of C powder is 0.3μm. After mixing the powders, they were placed in a ball mill jar, 80ml of anhydrous ethanol was added, and the mixture was ball-milled at a ball-to-powder ratio of 5:1 and a ball milling speed of 250 rpm for 24 hours using a forward high-energy ball milling method. After thoroughly drying the slurry, a powder mixture was obtained.

[0067] Step 2: Preparation of aluminum-containing high-entropy carbonitride ceramic powder

[0068] The powder mixture obtained in the first step was sieved and placed in a graphite boat. Nitrogen gas of 10 sccm / g was introduced into a tube furnace, and the temperature was raised to 1600℃ and held for 2 hours to carry out an in-situ carbothermic reduction nitriding reaction. The furnace was then cooled to obtain aluminum-containing high-entropy carbonitride ceramic powder.

[0069] Step 3: Preparation of aluminum-containing high-entropy carbonitride ceramic bulk

[0070] The uniformly mixed high-entropy carbonitride ceramic powder obtained in the second step was sintered into a bulk material by spark plasma sintering. The sintering pressure was 40 MPa, and the material was heated to 2000°C at a heating rate of 100°C / min under vacuum conditions. The temperature was held for 10 minutes, and the material was cooled to room temperature in the furnace to obtain an aluminum-containing high-entropy carbonitride ceramic bulk material.

[0071] Step 4: Mechanical properties and oxidation resistance of high-entropy carbonitride ceramic bulks

[0072] The high-entropy carbonitride ceramic material prepared in this example showed an oxidation weight gain of 831.03 × 10⁻⁶ after oxidation at 800 °C for 2 hours. -4 g / cm 2 Vickers hardness H v The strength of 1.0 is 23.62 GPa, and the fracture toughness is 3.06 MPa / m. 2 .

[0073] Example 4

[0074] Step 1: Mixing transition metal oxide powder, alumina powder, and carbon powder

[0075] Based on the calculated weight ratio of each component oxide powder and the required carbon black powder, the five transition metal carbonitrides have the same atomic percentage of 19.2%, while the atomic percentage of aluminum is 4%. 4.81g of TiO2 powder, 13.29g of Ta2O5 powder, 8.00g of Nb2O5 powder, 7.40g of ZrO2 powder, 5.47g of V2O5 powder, 0.64g of Al2O3 powder, and 10.40g of C powder were weighed. The particle size of Al2O3 powder was 50nm, the particle size of the oxides corresponding to the transition metal elements was 0.2–10μm, and the particle size of C powder was 0.3μm. After mixing the powders, they were placed in a ball mill jar, 80ml of anhydrous ethanol was added, and ball milling was performed at a ball-to-powder ratio of 5:1 and a speed of 250 rpm for 24 hours using forward high-energy ball milling. After thoroughly drying the slurry, a powder mixture was obtained.

[0076] Step 2: Preparation of aluminum-containing high-entropy carbonitride ceramic powder

[0077] The powder mixture obtained in the first step was sieved and placed in a graphite boat. Nitrogen gas of 10 sccm / g was introduced into a tube furnace, and the temperature was raised to 1600℃ and held for 2 hours to carry out an in-situ carbothermic reduction nitriding reaction. The furnace was then cooled to obtain aluminum-containing high-entropy carbonitride ceramic powder.

[0078] Step 3: Preparation of aluminum-containing high-entropy carbonitride ceramic bulk

[0079] The uniformly mixed high-entropy carbonitride ceramic powder obtained in the second step was sintered into a bulk material by spark plasma sintering. The sintering pressure was 40 MPa, and the material was heated to 2000°C at a heating rate of 100°C / min under vacuum conditions. The temperature was held for 10 minutes, and the material was cooled to room temperature in the furnace to obtain an aluminum-containing high-entropy carbonitride ceramic bulk material.

[0080] Step 4: Mechanical properties and oxidation resistance of high-entropy carbonitride ceramic bulks

[0081] The Vickers hardness H of the aluminum-containing high-entropy carbonitride ceramic material prepared in this example is... v The strength of 1.0 is 21.87 GPa, and the fracture toughness is 3.09 MPa / m. 2 After oxidation at 800℃ for 2 hours, the weight gain was 775.31*10. -4 g / cm 2 .

Claims

1. A method of producing an aluminum-containing high-entropy carbonitride ceramic, characterized by: According to the design ratio, oxides of transition metal elements, nano-alumina and carbon black are mixed to obtain a mixed powder. The mixed powder is subjected to in-situ carbothermic reduction nitridation reaction in a nitrogen atmosphere to obtain aluminum-containing high-entropy carbonitride ceramic powder. The aluminum-containing high-entropy carbonitride ceramic powder is then subjected to spark plasma sintering to obtain aluminum-containing high-entropy carbonitride ceramic. The average particle size of the oxides corresponding to the transition metal elements is 0.2~10 μm, the average particle size of alumina is 0.04~0.08 μm, and the average particle size of carbon black is 0.1~2 μm; In the mixed powder, the total mass fraction of oxides corresponding to transition metal elements is 77.92~79.41 wt.%, the mass fraction of alumina is 0.32~1.28 wt.%, and the mass fraction of carbon black is 15~25 wt.%; totaling 100%. The aluminum-containing high-entropy carbonitride ceramic is composed of a high-entropy carbonitride ceramic matrix and AlN particles dispersed in the high-entropy carbonitride ceramic matrix, wherein the high-entropy carbonitride ceramic matrix contains Al; In the high-entropy carbonitride ceramic, the atomic percentage of aluminum is 1~4 at.%% The in-situ carbothermic reduction nitriding reaction is carried out at a temperature of 1500~1700℃ and for a time of 1~3h. The discharge plasma sintering is carried out under vacuum conditions. The discharge plasma sintering process is as follows: the temperature is raised to 1900~2100℃ at a heating rate of 80~120℃ / min, held for 10~15min, and then cooled to room temperature. The pressure of the discharge plasma sintering is 30~45MPa. The high-entropy carbonitride ceramic matrix also contains transition metal elements, carbon, and nitrogen, wherein the transition metal elements are selected from any five of Ti, V, Zr, Nb, Mo, Hf, Ta, and Cr.

2. The method for preparing an aluminum-containing high-entropy carbonitride ceramic according to claim 1, characterized in that: The mixing method is ball milling, with a ball-to-material ratio of 3~7:1, a ball milling speed of 150~300 rpm, and a ball milling time of 24~48 h; The ball milling is a wet ball milling process, the ball milling medium is anhydrous ethanol, and the ball milling direction is forward rotation.

3. The method for preparing an aluminum-containing high-entropy carbonitride ceramic according to claim 1, characterized in that: The flow rate of nitrogen gas introduced in the in-situ carbothermic reduction nitridation reaction is 8~12 sccm / g.