High-entropy ultrahigh-temperature ceramic material and preparation method therefor

Abstract

A high-entropy ultrahigh-temperature ceramic material and a preparation method therefor. The high-entropy ultrahigh-temperature ceramic material is boron-containing nitrogen-containing carbide, and has a molecular formula of XCyBzNw, wherein X is at least four of Zr, Hf, Ti, Ta, Nb, V and W, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, and y+z+w≤1. The high-entropy ultrahigh-temperature ceramic material is a single-phase solid solution and has a face-centered cubic structure. The high-entropy ultrahigh-temperature ceramic material has both a temperature resistance characteristic and an antioxidation characteristic at an ultrahigh melting point, and has important potential for use in protection of key petroleum and petrochemical equipment against extreme high temperature and strong-corrosion media and in ultrahigh-temperature thermal protection systems.

Description

High-entropy ultrahigh-temperature ceramic material and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202311180019.4 filed on September 13, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of high-entropy and ultra-high-temperature carbide ceramics, and in particular to a high-entropy and ultra-high-temperature ceramic material and a preparation method thereof. Background Art

[0004] Ultra-high temperature ceramics have high melting points, high stability and high-temperature strength. In the petroleum and petrochemical industries, downhole drill bits and high-temperature corrosion component surfaces need to face harsh environments such as extreme high temperatures and strong corrosive media. The use of ultra-high temperature ceramics to form protective coatings can extend the service life of key equipment. At the same time, the high melting point of ultra-high temperature ceramics also makes it an important candidate material for extreme environment thermal protection systems in aerospace. However, in ultra-high temperature ceramics, binary carbides have poor oxidation resistance, which affects their potential applications. According to the size of the entropy value (S), ultra-high temperature ceramics are usually divided into low-entropy ultra-high temperature ceramics (S≤1.0R), medium-entropy ultra-high temperature ceramics (1.0R<S≤1.5R) and high-entropy ultra-high temperature ceramics (S>1.5R) ceramics, where R is the gas constant.

[0005] High entropy ultra-high temperature ceramics usually refer to solid solutions formed by five or more ceramic components. Due to its novel "high entropy effect" and excellent anti-oxidation performance, it has become one of the research hotspots in the ceramic field in recent years. CN109180188A discloses a high entropy boron carbide ultra-high temperature ceramic powder with the molecular formula XC y B z , wherein X is at least two of Zr, Ti, Hf, V, Nb, Ta, Cr, Mo or W, 0.6≤y<1.0, 0<z≤0.4, y+z=1, and has a single-phase face-centered cubic structure. The ceramic powder is a single-phase solid solution with a face-centered cubic structure and contains boron. It has both the high-temperature resistance of carbides and the oxidation resistance of borides, and can be used to prepare high-entropy boron-containing carbide ultra-high temperature ceramic blocks or composite materials that are resistant to oxidation and ablation. However, during the oxidation and ablation process of the high-entropy boron-containing carbide ultra-high temperature ceramic powder, boron will oxidize to form boron oxide. When the temperature is higher than its boiling point (1860℃), a large amount of boron oxide will volatilize, causing defects such as pores and cracks, which is not conducive to the ablation resistance of the boron-containing carbide. Therefore, the ablation resistance of the high-entropy boron-containing carbide ceramic powder still needs to be further improved.

[0006] Wen et al. synthesized a carbide solid solution containing N (Hf0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )(C 0.5 N 0.5 )(Wen T,et al.Journal of the American Ceramic Society,2020,103(11):6475-6489), Peng et al. synthesized (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )(C 0.8 N 0.2 )(Peng Z, et al.Corrosion Science, 2021, 184:109359). Their research results show that nitrogen doping enables carbide ceramics to form stronger chemical bonds, giving them higher ablation resistance.

[0007] The introduction of nitrogen into high-entropy boron-containing carbide ultra-high-temperature ceramic powders can improve ablation resistance. However, the introduction of nitrogen easily leads to the formation of new phases. Currently, there are no reports on the preparation of single-phase high-entropy boron-containing and nitrogen-containing carbide ceramics. This is because nitrogen has a lower reaction free energy with metal elements in Groups IV and V of the periodic table. Compared with C and B, it preferentially forms stable nitrides, making it difficult for C and B to further dissolve into the carbide. As a result, the introduced C and B elements do not dissolve but react with the metal elements to form a second phase.

[0008] Guan et al. (GUAN J, et al. Journal of the American Ceramic Society, 2022, 105(10): 6417-6426) mixed a variety of metal powders and amorphous BCN powders by high-energy ball milling and then hot-pressed sintered them at 1900°C to produce boron- and nitrogen-containing carbide composite ceramics. However, the boron- and nitrogen-containing carbide composite ceramics have more than one phase, including BN(C) phase, (Ta 0.2 Nb 0.2 Zr 0.2 Hf 0.2 Ti 0.2 )(B, C, N) phase and oxide phase, and with the decrease of BCN addition, a new phase MB2 appears. This document does not involve how to prepare only (Ta 0.2 Nb 0.2 Zr 0.2 Hf 0.2 Ti 0.2)(B,C,N) phase correlation method.

[0009] Therefore, there is an urgent need to provide a high-entropy ultrahigh-temperature ceramic material with a single phase, which does not destroy the face-centered cubic structure of carbides and contains both boron and nitrogen elements, and a preparation method thereof.

[0010] Summary of the Invention

[0011] The purpose of the present invention is to solve the problems of poor oxidation resistance of binary carbide ultrahigh temperature ceramics and poor ablation resistance of high entropy boron-containing carbides, and to provide a high entropy ultrahigh temperature ceramic material and a preparation method thereof.

[0012] In order to achieve the above object, the first aspect of the present invention provides a high entropy ultrahigh temperature ceramic material, wherein the molecular formula of the high entropy ultrahigh temperature ceramic material is XC y B z N w , wherein X is at least four of Zr, Hf, Ti, Ta, Nb, V, and W, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, y+z+w≤1, and the high-entropy ultrahigh-temperature ceramic material is a single-phase solid solution having a face-centered cubic structure.

[0013] Preferably, X is four or five of Zr, Hf, Ti, Ta, Nb, V, and W.

[0014] Preferably, X is Zr, Hf, Ti and Ta, or X is Zr, Hf, Ti, Ta and Nb.

[0015] Preferably, 0.75≤y≤0.95, 0.01≤z≤0.15, 0.05≤w≤0.15, y+z+w≤1.

[0016] Preferably, the molecular formula of the high entropy ultrahigh temperature ceramic material is (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 )(C 0.82 B 0.10 N 0.08 )、(Zr 0.4 Hf 0.2 Ti 0.2 Ta 0.2 )(C 0.70 B 0.15 N 0.15 )、(Zr 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )(C 0.90 B 0.03 N0.07 )、(Zr 0.3 Hf 0.3 Ti 0.2 Ta 0.1 Nb 0.1 )(C 0.87 B 0.06 N 0.07 )

[0017] A second aspect of the present invention provides a method for preparing a high-entropy ultrahigh temperature ceramic material, wherein the method comprises the following steps:

[0018] (1) mixing metal powder and carbon powder and grinding them to obtain a mixed powder; wherein the metal powder is selected from at least four of Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder, and W powder;

[0019] (2) subjecting the mixed powder to pressureless spark plasma sintering to obtain carbide powder;

[0020] (3) mixing the carbide powder with B2O3 powder under vacuum conditions and then calcining the mixture to obtain boron-containing carbide powder;

[0021] (4) mixing the boron carbide powder and g-C3N4 powder under vacuum conditions and then subjecting the mixture to a high-temperature heat treatment to obtain a high-entropy ultrahigh-temperature ceramic material; wherein the temperature of the high-temperature heat treatment is 1500-1800°C;

[0022] Wherein, the molecular formula of the high entropy ultrahigh temperature ceramic material is XC y B z N w , X is metal, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, y+z+w≤1.

[0023] Preferably, the metal powder is selected from four or five of the group consisting of Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder, and W powder.

[0024] Preferably, the metal powder is Zr powder, Hf powder, Ti powder and Ta powder, or the metal powder is Zr powder, Hf powder, Ti powder, Ta powder and Nb powder.

[0025] Preferably, the grinding is wet ball milling; wherein, the operating conditions of the wet ball milling include: ball milling speed of 150-300 rpm, ball milling time of 1-5 h, ball milling medium of ethanol and / or water, and ball-to-material ratio of 6-10:1.

[0026] Preferably, the operating conditions of the pressureless spark plasma sintering include: vacuum degree ≤ 10 Pa, heating rate of 50-150° C. / min, temperature of 1300-1800° C., and holding time of 15-60 min.

[0027] Preferably, the operating conditions of the pressureless spark plasma sintering include: vacuum degree ≤ 5 Pa, heating rate of 80-120° C. / min, temperature of 1500-1700° C., and holding time of 20-40 min.

[0028] Preferably, the calcination operating conditions include: vacuum degree ≤ 10 Pa, heating rate of 30-150° C. / min, temperature of 1400-1900° C., and holding time of 15-60 min.

[0029] Preferably, the calcination operating conditions include: vacuum degree ≤ 5 Pa, heating rate of 50-100° C. / min, temperature of 1600-1800° C., and holding time of 20-40 min.

[0030] Preferably, the temperature of the high temperature heat treatment is 1600-1700°C.

[0031] Preferably, the vacuum degree of the high-temperature heat treatment is ≤10 Pa, the heating rate is 30-150° C. / min, and the holding time is 15-60 min.

[0032] Preferably, the vacuum degree of the high-temperature heat treatment is ≤5 Pa, the heating rate is 50-100° C. / min, and the holding time is 20-40 min.

[0033] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0034] 1) The high-entropy ultrahigh-temperature ceramic material provided in the present invention contains both B and N elements, has a single phase, a face-centered cubic structure, and has excellent ablation resistance and oxidation resistance;

[0035] 2) The preparation method of the high-entropy ultrahigh-temperature ceramic material provided in the present invention has a short preparation time, is easy to control the reaction process, and does not introduce impurities during the process, which is conducive to optimizing the content of each component and obtaining a high-purity single-phase solid solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a microscopic morphology and elemental surface scanning analysis diagram of the high-entropy ultrahigh temperature ceramic material prepared in Example 1;

[0037] FIG2 is an XRD pattern of the high entropy ultrahigh temperature ceramic material prepared in Example 1;

[0038] FIG3 is an XRD pattern of the boron- and nitrogen-containing carbide prepared in Comparative Example 1;

[0039] FIG4 is an XRD pattern of the boron-containing carbide prepared in Comparative Example 2. DETAILED DESCRIPTION

[0040] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0041] The first aspect of the present invention provides a high entropy ultrahigh temperature ceramic material, wherein the molecular formula of the high entropy ultrahigh temperature ceramic material is XC y B z N w , wherein X is at least four of Zr, Hf, Ti, Ta, Nb, V, and W, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, and y+z+w≤1; the high-entropy ultrahigh temperature ceramic material is a single-phase solid solution having a face-centered cubic structure.

[0042] Among them, in the present invention, the high-entropy ultrahigh temperature ceramic material is a boron-nitrogen-containing carbide, which contains both B and N elements, has a single phase, a face-centered cubic structure, and has excellent ablation resistance and oxidation resistance.

[0043] In a preferred embodiment of the present invention, X is four or five of Zr, Hf, Ti, Ta, Nb, V, and W.

[0044] In the present invention, Zr, Hf, Ti, Ta, Nb, V, and W can form a solid solution. While the present invention limits the number of types of X, it does not impose any particular restrictions on the composition ratio of the various metals in X. For example, X can be Zr, Hf, Ti, and Ta in any ratio, or Zr, Hf, Ti, Ta, and Nb in any ratio. Preferably, the composition of the various metals in X is the same.

[0045] In a preferred embodiment of the present invention, y can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.96, 0.97, 0.98, 0.99, 0.999, and any number between these values. Preferably, 0.75≤y≤0.95.

[0046] In a preferred embodiment of the present invention, z can be 0.001, 0.01, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, and any number between these values, preferably, 0.01≤z≤0.15.

[0047] In a preferred embodiment of the present invention, w can be 0.001, 0.01, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, and any number between these values, preferably, 0.05≤w≤0.15.

[0048] In a preferred embodiment of the present invention, the molecular formula of the high entropy ultrahigh temperature ceramic material is (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 )(C 0.82 B 0.10 N 0.08 )、(Zr 0.4 Hf 0.2 Ti 0.2 Ta 0.2 )(C 0.70 B 0.15 N 0.15 )、(Zr 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )(C 0.90 B 0.03 N 0.07 )、(Zr 0.3 Hf 0.3 Ti 0.2 Ta 0.1 Nb 0.1 )(C 0.87 B 0.06 N 0.07 )

[0049] The high-entropy ultrahigh-temperature ceramic material provided in the present invention combines the ultra-high melting point temperature resistance of carbides and nitrides with the antioxidant properties of borides, providing protection against extreme high temperatures and highly corrosive media for key equipment in the petroleum and petrochemical industries, and has important potential applications in ultra-high-temperature thermal protection systems in aerospace.

[0050] A second aspect of the present invention provides a method for preparing a high-entropy ultrahigh temperature ceramic material, wherein the method comprises the following steps:

[0051] (1) mixing metal powder and carbon powder and grinding them to obtain a mixed powder; wherein the metal powder is selected from at least four of Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder, and W powder;

[0052] (2) subjecting the mixed powder to pressureless spark plasma sintering to obtain carbide powder;

[0053] (3) mixing the carbide powder with B2O3 powder under vacuum conditions and then calcining the mixture to obtain boron-containing carbide powder;

[0054] (4) mixing the boron-containing carbide powder with g-C3N4 powder under vacuum conditions and subjecting the mixture to a high-temperature heat treatment to obtain a high-entropy ultrahigh-temperature ceramic material, i.e., a boron-containing and nitrogen-containing carbide; wherein the high-temperature heat treatment temperature is 1500-1800°C;

[0055] Wherein, the molecular formula of the high entropy ultrahigh temperature ceramic material is XC y B z N w , X is metal, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, y+z+w≤1.

[0056] Among them, in the present invention, the C in g-C3N4 powder is mainly used to react with the O element introduced by B2O3 powder to eliminate the O element. If there is still g-C3N4 powder after eliminating the O element, the excess g-C3N4 powder will be dissolved into the boron and nitrogen carbide during the preparation process, but will not form a second phase. Therefore, by adjusting the feeding amount of metal powder, carbon powder, B2O3 powder and g-C3N4 powder, a material with the molecular formula XC y B z N w High-entropy ultra-high temperature ceramic materials - boron and nitrogen carbides.

[0057] In step (1):

[0058] In a preferred embodiment of the present invention, the metal powder is selected from four or five of the group consisting of Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder, and W powder.

[0059] The present invention does not impose any particular limitation on the mixing ratio of the metal powders, and the amounts of the various metal powders can be adjusted according to actual needs. Preferably, the amounts of the various metal powders in X are the same.

[0060] In a preferred embodiment of the present invention, the metal powder is Zr powder, Hf powder, Ti powder and Ta powder, or the metal powder is Zr powder, Hf powder, Ti powder, Ta powder and Nb powder.

[0061] In a preferred embodiment of the present invention, the purity of the metal powder and the carbon powder are both ≥98%, and the metal powder and the carbon powder are both micron-scale and / or nano-scale powders.

[0062] In a preferred embodiment of the present invention, the grinding is selected from ball milling, preferably wet ball milling; wherein the operating conditions of the wet ball milling include: ball milling speed of 150-300 rpm, ball milling time of 1-5h, ball milling medium of ethanol and / or water, and ball-to-material ratio of 6-10:1.

[0063] In a preferred embodiment of the present invention, the ball milling is followed by drying to obtain a mixed powder, wherein the drying temperature may be 30-60°C.

[0064] In step (2):

[0065] In a preferred embodiment of the present invention, the operating conditions of the pressureless spark plasma sintering include: vacuum degree ≤10Pa, preferably ≤5Pa; heating rate 50-150°C / min, preferably 80-120°C / min; temperature 1300-1800°C, preferably 1500-1700°C; holding time 15-60min, preferably 20-40min.

[0066] In the present invention, mixing metal powder with carbon powder and then pressureless spark plasma sintering can produce a non-stoichiometric, high-purity, low-free-carbon, single-phase carbide solid solution powder material with carbon vacancy defects. The formation of carbon vacancy defects creates conditions for the introduction of elements B and N.

[0067] In a preferred embodiment of the present invention, after pressureless spark plasma sintering, the sintered product is crushed and ball-milled to obtain carbide powder.

[0068] Among them, in the present invention, the ball milling after pressureless discharge plasma sintering is preferably wet ball milling, and the operating conditions of the wet ball milling include: the ball milling speed is 150-300 rpm, the time is 0.1-5h, the ball milling medium is ethanol and / or water, and the ball-to-material ratio is 6-10:1.

[0069] In step (3):

[0070] In a preferred embodiment of the present invention, the purity of the B2O3 powder is ≥98%, and the powder is micron-scale and / or nano-scale.

[0071] In a preferred embodiment of the present invention, the calcination operating conditions include: vacuum degree ≤10Pa, preferably ≤5Pa; heating rate of 30-150℃ / min, preferably 50-100℃ / min; temperature of 1400-1900℃, preferably 1600-1800℃; holding time of 15-60min, preferably 20-40min.

[0072] In step (4):

[0073] In a preferred embodiment of the present invention, the purity of the g-C3N4 powder is ≥98%, and the powder is micron-scale and / or nano-scale.

[0074] Among them, in the present invention, the inventors have found through research that when g-C3N4 powder is used as a nitrogen source, on the one hand, the C in g-C3N4 can consume the O element introduced by B2O3 powder to avoid the formation of metal oxides; on the other hand, the N element can fill the carbon vacancies in the carbide and dissolve into the carbide lattice to form a solid solution without destroying the face-centered cubic structure of the carbide.

[0075] In a preferred embodiment of the present invention, the temperature of the high-temperature heat treatment is preferably 1600-1700°C.

[0076] In a preferred embodiment of the present invention, the vacuum degree of the high-temperature heat treatment is ≤10Pa, preferably ≤5Pa; the heating rate is 30-150°C / min, preferably 50-100°C / min; and the holding time is 15-60min, preferably 20-40min.

[0077] In the present invention, the calcination in step (3) and the high-temperature heat treatment in step (4) can be carried out under vacuum, and there is no special limitation on the heating method and heating equipment. The heating equipment includes but is not limited to a vacuum sintering furnace, a spark plasma sintering furnace, a high-temperature graphitization furnace, a muffle furnace and the like. Preferably, the calcination in step (3) and the high-temperature heat treatment in step (4) are carried out in a vacuum sintering furnace, and both are pressureless sintering.

[0078] In a preferred embodiment of the present invention, 0.75≤y≤0.95, 0.01≤z≤0.15, 0.05≤w≤0.15, and y+z+w≤1.

[0079] The preparation method of the high-entropy ultrahigh-temperature ceramic material provided in the present invention uses B2O3 powder as the B source and g-C3N4 powder as the N source, which can ensure that there are no impurity elements in the synthesized high-entropy ultrahigh-temperature ceramic material and no other phases will be generated. Not only can a high-purity single-phase solid solution be obtained, but the preparation time can also be shortened, the difficulty of controlling the preparation process can be reduced, and it is more conducive to optimizing the design of the content of each component, significantly improving the ablation resistance and antioxidant properties of the high-entropy ultrahigh-temperature ceramic material.

[0080] The present invention will be described in detail below through examples. In the examples and comparative examples, the Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, carbon powder, B2O3 powder and g-C3N4 powder are all micron-grade powders with a purity of ≥99%.

[0081] Example 1

[0082] (1) Zr powder, Hf powder, Ti powder, Ta powder, and C powder were mixed in a molar ratio of 0.25:0.25:0.25:0.25:0.8, and then ball-milled for 2 h in a planetary ball mill using ethanol as the ball milling medium, at a speed of 200 rpm and a ball-to-material ratio of 6:1. The mixed powder was taken out after ball milling, dried at 40°C, and sieved to obtain a mixed powder;

[0083] (2) placing the above mixed powder in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering, with the vacuum degree in the furnace less than 5 Pa, heating to 1600°C at a heating rate of 100°C / min and holding for 30 minutes, then cooling to room temperature, taking out and crushing, and ball milling into powder in a ball mill, with ethanol as the ball milling medium, a rotation speed of 200 rpm, a ball-to-material ratio of 6:1, and a ball milling time of 0.5 h. After ball milling, the mixed powder was taken out and dried at 40°C to obtain carbide powder;

[0084] (3) Based on the B element in the B2O3 powder and the C element in the carbide powder, the B2O3 powder and the carbide powder are mixed in ethanol at a molar ratio of 0.1:0.8, taken out after 24 hours, and dried at 40°C; then placed in a graphite pot, and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa, and heated to 1600°C at a heating rate of 50°C / min, kept at this temperature for 30 minutes, and then cooled to room temperature and taken out to obtain boron-containing carbide powder;

[0085] (4) Based on the N element in g-C3N4 powder and the C element in the boron-containing carbide powder, the g-C3N4 powder and the boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.1:0.8, taken out after 24 hours, and dried at 40°C; then placed in a graphite can and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa. The temperature is raised to 1700°C at a heating rate of 50°C / min, kept warm for 30 minutes, and then cooled to room temperature and taken out to obtain boron- and nitrogen-containing carbide powder, that is, high-entropy ultrahigh temperature ceramic material.

[0086] Figure 1 shows the micromorphology and elemental surface scanning analysis of the high-entropy, ultrahigh-temperature ceramic material prepared in Example 1. The figure shows that the particle size of the high-entropy, ultrahigh-temperature ceramic material is ~100 nm. The elemental surface scanning results show that the powder contains Zr, Hf, Ti, Ta, C, B, and N elements, and the elements are evenly distributed, indicating that the high-entropy, ultrahigh-temperature ceramic material forms a solid solution.

[0087] According to ICP-OES element content analysis, the atomic ratio of Zr, Hf, Ti and Ta is 0.25:0.25:0.25:0.25, and the atomic ratio of C, B and N is 0.82:0.10:0.08. The molecular formula of the high-entropy ultrahigh temperature ceramic material is (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 )(C 0.82 B 0.10 N 0.08 ).

[0088] Example 2

[0089] (1) Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, and C powder were mixed in a molar ratio of 0.2:0.2:0.2:0.2:0.2:0.9, and then ball-milled for 2 h in a planetary ball mill using ethanol as the ball milling medium, at a speed of 150 rpm and a ball-to-material ratio of 6:1. After ball milling, the mixture was taken out, dried at 40°C, and sieved to obtain a mixed powder;

[0090] (2) placing the above mixed powder in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering, with the vacuum degree in the furnace less than 5 Pa, heating to 1600°C at a heating rate of 100°C / min and holding for 30 minutes, then cooling to room temperature, taking out and crushing, and ball milling into powder in a ball mill, with ethanol as the ball milling medium, a rotation speed of 200 rpm, a ball-to-material ratio of 6:1, and a ball milling time of 0.5 h. After ball milling, the mixed powder was taken out and dried at 40°C to obtain carbide powder;

[0091] (3) Based on the B element in the B2O3 powder and the C element in the carbide powder, the B2O3 powder and the carbide powder are mixed in ethanol at a molar ratio of 0.1:0.9, taken out after 24 hours, and dried at 40°C; then placed in a graphite pot, and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa, and heated to 1800°C at a heating rate of 100°C / min and kept at this temperature for 30 minutes, and then cooled to room temperature and taken out to obtain boron-containing carbide powder;

[0092] (4) Based on the N element in g-C3N4 powder and the C element in the boron-containing carbide powder, the g-C3N4 powder and the boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.1:0.9, taken out after 24 hours, and dried at 40°C; then placed in a graphite can and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa. The temperature is raised to 1600°C at a heating rate of 100°C / min and kept at this temperature for 30 minutes. Then, the powder is cooled to room temperature and taken out to obtain boron- and nitrogen-containing carbide powder, which is also a high-entropy ultrahigh-temperature ceramic material.

[0093] According to ICP-OES element content analysis, the atomic ratio of Zr, Hf, Ti, Ta and Nb is 0.2:0.2:0.2:0.2:0.2, and the atomic ratio of C, B and N is 0.90:0.03:0.70. The molecular formula of the high entropy ultrahigh temperature ceramic material is (Zr 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )(C 0.90 B 0.03 N 0.07 ).

[0094] Example 3

[0095] (1) Zr powder, Hf powder, Ti powder, Ta powder, and C powder were mixed in a molar ratio of 0.4:0.2:0.2:0.2:0.7, and then ball-milled for 2 h in a planetary ball mill using ethanol as the milling medium, at a speed of 200 rpm and a ball-to-material ratio of 6:1. The milled mixture was taken out, dried at 40°C, and sieved to obtain a mixed powder;

[0096] (2) placing the above mixed powder in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering, with a vacuum degree of less than 5 Pa in the furnace, heating to 1800°C at a heating rate of 60°C / min and holding for 15 minutes, then cooling to room temperature, taking out and crushing, and ball milling into powder in a ball mill, using ethanol as the ball milling medium, a rotation speed of 200 rpm, a ball-to-material ratio of 6:1, and a ball milling time of 0.5 h. After ball milling, the mixed powder was taken out and dried at 40°C to obtain carbide powder;

[0097] (3) Based on the B element in the B2O3 powder and the C element in the carbide powder, the B2O3 powder and the carbide powder are mixed in ethanol at a molar ratio of 0.15:0.7, taken out after 24 hours, and dried at 40°C; then placed in a graphite pot, and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa, and heated to 1600°C at a heating rate of 30°C / min, kept at this temperature for 15 minutes, and then cooled to room temperature and taken out to obtain boron-containing carbide powder;

[0098] (4) Based on the N element in g-C3N4 powder and the C element in the boron-containing carbide powder, the g-C3N4 powder and the boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.15:0.7, taken out after 24 hours, and dried at 40°C; then placed in a graphite can and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa. The temperature is raised to 1800°C at a heating rate of 120°C / min, kept at this temperature for 15 minutes, and then cooled to room temperature and taken out to obtain boron- and nitrogen-containing carbide powder, that is, high-entropy ultrahigh temperature ceramic material.

[0099] According to ICP-OES element content analysis, the atomic ratio of Zr, Hf, Ti and Ta is 0.4:0.2:0.2:0.2, the atomic ratio of C, B and N is 0.70:0.15:0.15, and the molecular formula of the high-entropy ultrahigh temperature ceramic material is (Zr 0.4 Hf 0.2 Ti 0.2 Ta 0.2 )(C 0.70 B 0.15 N 0.15 ).

[0100] Example 4

[0101] (1) Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, and C powder were mixed in a molar ratio of 0.3:0.3:0.1:0.1:0.1:0.9, and ball milled for 2 h in a planetary ball mill using ethanol as the ball milling medium, at a speed of 150 rpm and a ball-to-material ratio of 6:1. After ball milling, the mixture was taken out, dried at 40°C, and sieved to obtain a mixed powder;

[0102] (2) placing the mixed powder in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering, with a vacuum degree of less than 5 Pa in the furnace, heating the mixture to 1400°C at a heating rate of 140°C / min and holding the temperature for 50 min, then cooling the mixture to room temperature, removing the mixture and crushing the mixture, and grinding the mixture into powder in a ball mill using ethanol as the ball milling medium, a rotation speed of 200 rpm, a ball-to-material ratio of 6:1, and a ball milling time of 0.5 h. After ball milling, the mixture was removed and dried at 40°C to obtain carbide powder;

[0103] (3) Based on the B element in the B2O3 powder and the C element in the carbide powder, the B2O3 powder and the carbide powder are mixed in ethanol at a molar ratio of 0.1:0.9, taken out after 24 hours, and dried at 40°C; then placed in a graphite pot, and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa, and heated to 1500°C at a heating rate of 120°C / min and kept at this temperature for 50 minutes, and then cooled to room temperature and taken out to obtain boron-containing carbide powder;

[0104] (4) Based on the N element in g-C3N4 powder and the C element in the boron-containing carbide powder, the g-C3N4 powder and the boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.1:0.9, taken out after 24 hours, and dried at 40°C; then placed in a graphite can and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa. The temperature is raised to 1500°C at a heating rate of 30°C / min, kept warm for 50 minutes, and then cooled to room temperature and taken out to obtain boron- and nitrogen-containing carbide powder, that is, high-entropy ultrahigh temperature ceramic material.

[0105] According to ICP-OES element content analysis, the atomic ratio of Zr, Hf, Ti, Ta and Nb is 0.3:0.3:0.2:0.1:0.1, the atomic ratio of C, B and N is 0.87:0.06:0.07, and the molecular formula of the high-entropy ultrahigh temperature ceramic material is (Zr 0.3 Hf 0.3 Ti 0.2 Ta 0.1 Nb 0.1 )(C 0.87 B 0.06 N 0.07 ).

[0106] Comparative Example 1

[0107] The same as Example 1, except that in step (4), the vacuum sintering furnace is heated to 1300° C. at a heating rate of 50° C. / min.

[0108] (1) Zr powder, Hf powder, Ti powder, Ta powder, and C powder were mixed in a molar ratio of 0.25:0.25:0.25:0.25:0.8, and then ball-milled for 2 h in a planetary ball mill using ethanol as the ball milling medium, at a speed of 200 rpm and a ball-to-material ratio of 6:1. The mixed powder was taken out after ball milling, dried at 40°C, and sieved to obtain a mixed powder;

[0109] (2) placing the above mixed powder in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering, with the vacuum degree in the furnace less than 5 Pa, heating to 1600°C at a heating rate of 100°C / min and holding for 30 minutes, then cooling to room temperature, taking out and crushing, and ball milling into powder in a ball mill, with ethanol as the ball milling medium, a rotation speed of 200 rpm, a ball-to-material ratio of 6:1, and a ball milling time of 0.5 h. After ball milling, the mixed powder was taken out and dried at 40°C to obtain carbide powder;

[0110] (3) Based on the B element in the B2O3 powder and the C element in the carbide powder, the B2O3 powder and the carbide powder are mixed in ethanol at a molar ratio of 0.1:0.8, taken out after 24 hours, and dried at 40°C; then placed in a graphite pot, and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa, and heated to 1600°C at a heating rate of 50°C / min, kept at this temperature for 30 minutes, and then cooled to room temperature and taken out to obtain boron-containing carbide powder;

[0111] (4) Based on the N element in the g-C3N4 powder and the C element in the boron-containing carbide powder, the g-C3N4 powder and the boron-containing carbide powder were mixed in deionized water at a molar ratio of 0.1:0.8, taken out after 24 hours, and dried at 40°C; then placed in a graphite can and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5 Pa. The temperature was raised to 1300°C at a heating rate of 50°C / min, kept warm for 30 minutes, and then cooled to room temperature and taken out to obtain boron- and nitrogen-containing carbide powder.

[0112] Comparative Example 2

[0113] The same as Example 1, except that step 4 is omitted and a carbon source is added in step 3.

[0114] (1) Zr powder, Hf powder, Ti powder, Ta powder, and C powder were mixed in a molar ratio of 0.25:0.25:0.25:0.25:0.8, and then ball-milled for 2 h in a planetary ball mill using ethanol as the ball milling medium, at a speed of 200 rpm and a ball-to-material ratio of 6:1. The mixed powder was taken out after ball milling, dried at 40°C, and sieved to obtain a mixed powder;

[0115] (2) placing the above mixed powder in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering, with the vacuum degree in the furnace less than 5 Pa, heating to 1600°C at a heating rate of 100°C / min and holding for 30 minutes, then cooling to room temperature, taking out and crushing, and ball milling into powder in a ball mill, with ethanol as the ball milling medium, a rotation speed of 200 rpm, a ball-to-material ratio of 6:1, and a ball milling time of 0.5 h. After ball milling, the mixed powder was taken out and dried at 40°C to obtain carbide powder;

[0116] (3) Based on the B element in the B2O3 powder and the C element in the carbide powder, the B2O3 powder and the above-mentioned carbide powder are mixed in ethanol at a molar ratio of 0.1:0.8, and 6wt% phenolic resin based on the total mass of the powder is added. After 24 hours, the powder is taken out and dried at 40°C; then, it is placed in a graphite can and pressurelessly sintered in a vacuum sintering furnace with a vacuum degree of less than 5Pa. The temperature is raised to 1600°C at a heating rate of 50°C / min, kept at this temperature for 30 minutes, and then cooled to room temperature and taken out to obtain boron-containing carbide powder.

[0117] The ICP-OES element content analysis showed that the atomic ratio of Zr, Hf, Ti and Ta was 0.25:0.25:0.25:0.25, and the atomic ratio of C, B and N was 0.83:0.10. The molecular formula of the boron carbide powder was (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 )(C 0.83 B 0.10 ).

[0118] Test Example 1

[0119] The powders prepared in Example 1 and Comparative Examples 1-2 were characterized by XRD, and the characterization results are shown in Figures 2-4, respectively.

[0120] Figure 2 is an XRD pattern of the high-entropy ultrahigh temperature ceramic material prepared in Example 1. As shown in Figure 2, the single-phase solid solution of the high-entropy ultrahigh temperature ceramic material prepared in Example 1 has a face-centered cubic structure.

[0121] Figure 3 is an XRD pattern of the boron- and nitrogen-containing carbide powder prepared in Comparative Example 1. As shown in Figure 3, the boron- and nitrogen-containing carbide powder prepared in Comparative Example 1 exhibits diffraction peaks of a Zr-Hf-Ti-Ta-CBN solid solution, HfO2, and g-C3N4, indicating that the powder is a mixture of these three substances. The Zr-Hf-Ti-Ta-CBN solid solution exhibits a characteristic peak of ZrC, indicating that when the high-temperature heat treatment temperature is low, the reaction of g-C3N4 with the O introduced by B2O3 is incomplete, resulting in the final powder containing the oxide impurity HfO2, and the powder cannot form a single phase of boron- and nitrogen-containing carbide.

[0122] Figure 4 is an XRD pattern of the boron-containing carbide powder prepared in Comparative Example 2. As shown in Figure 4, the boron-containing carbide powder is a single-phase solid solution having a face-centered cubic structure.

[0123] Test Example 2

[0124] The products prepared in Example 1 and Comparative Example 2 were tested for ablation performance and antioxidant performance. The test results are shown in Table 1:

[0125] The high-entropy ultrahigh-temperature ceramic material prepared in Example 1 and the boron carbide powder prepared in Comparative Example 2 were heated to 1900°C at 100°C / min under vacuum conditions (<5Pa), and maintained at a pressure of 50MPa for 10 minutes to obtain a bulk ceramic with a relative density of >95%. The bulk ceramic was subjected to an ablation performance test in a plasma ablation device, and the mass ablation rate (%) was calculated based on the mass change of the ceramic before and after ablation. The ablation temperature was 2500°C and the ablation time was 60s. The smaller the mass ablation rate, the better the ablation resistance of the product.

[0126] The antioxidant properties of the products prepared in Example 1 and Comparative Example 2 were tested using TG-DSC in an air atmosphere at a heating rate of 10°C / min, a product particle size of 5 μm, and an air atmosphere. The initial oxidation temperature was read from the DSC heating curve. A higher initial oxidation temperature indicates better antioxidant properties.

[0127] Table 1

[0128] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A high entropy ultrahigh temperature ceramic material, characterized in that: The molecular formula of the high entropy ultrahigh temperature ceramic material is XC y B z N w ; Wherein, X is at least 4 of Zr, Hf, Ti, Ta, Nb, V, and W, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, y+z+w≤1; the high-entropy ultrahigh temperature ceramic material is a single phase solid solution having a face-centered cubic structure.

2. The high entropy ultrahigh temperature ceramic material according to claim 1, wherein: X is four or five of Zr, Hf, Ti, Ta, Nb, V, and W.

3. The high entropy ultrahigh temperature ceramic material according to claim 2, wherein: X is Zr, Hf, Ti and Ta, or X is Zr, Hf, Ti, Ta and Nb.

4. The high entropy ultrahigh temperature ceramic material according to claim 1, wherein: 0.75≤y≤0.95, 0.01≤z≤0.15, 0.05≤w≤0.15, y+z+w≤1.

5. The high entropy ultrahigh temperature ceramic material according to claim 1, wherein: The molecular formula of the high entropy ultrahigh temperature ceramic material is (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 )(C 0.82 B 0.10 N 0.08 )、(Zr 0.4 Hf 0.2 Ti 0.2 Ta 0.2 )(C 0.70 B 0.15 N 0.15 )、(Zr 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )(C 0.90 B 0.03 N 0.07 )、(Zr 0.3 Hf 0.3 Ti 0.2 Ta 0.1 Nb 0.1 )(C 0.87 B 0.06 N 0.07 ) 6. A method for preparing a high entropy ultrahigh temperature ceramic material, characterized in that: The method comprises the following steps: (1) mixing metal powder and carbon powder and grinding them to obtain a mixed powder; wherein the metal powder is selected from at least four of Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder, and W powder; (2) subjecting the mixed powder to pressureless spark plasma sintering to obtain carbide powder; (3) mixing the carbide powder and B2O3 powder under vacuum conditions and then calcining the mixture to obtain boron-containing carbide powder; (4) Under vacuum conditions, the boron carbide powder is mixed with g-C3N4 powder and then subjected to high temperature Heat treatment to obtain a high entropy ultra-high temperature ceramic material; wherein the temperature of the high temperature heat treatment is 1500-1800°C; Wherein, the molecular formula of the high entropy ultrahigh temperature ceramic material is XC y B z N w , X is metal, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, y+z+w≤1.

7. The preparation method according to claim 6, wherein: The metal powder is selected from four or five of Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder and W powder.

8. The preparation method according to claim 7, wherein: The metal powder is Zr powder, Hf powder, Ti powder and Ta powder, or the metal powder is Zr powder, Hf powder, Ti powder, Ta powder and Nb powder.

9. The preparation method according to claim 6, wherein: The grinding is wet ball milling; wherein the operating conditions of the wet ball milling include: a ball milling speed of 150-300 rpm, a ball milling time of 1-5 hours, a ball milling medium of ethanol and / or water, and a ball-to-material ratio of 6-10:

1.

10. The preparation method according to claim 6, wherein: The operating conditions of the pressureless spark plasma sintering include: vacuum degree ≤10Pa, heating rate of 50-150°C / min, temperature of 1300-1800°C, and holding time of 15-60min.

11. The preparation method according to claim 10, wherein: The operating conditions of the pressureless spark plasma sintering include: vacuum degree ≤5Pa, heating rate of 80-120°C / min, temperature of 1500-1700°C, and holding time of 20-40min.

12. The preparation method according to claim 6, wherein: The calcination operation conditions include: vacuum degree ≤ 10Pa, heating rate of 30-150°C / min, temperature of 1400-1900°C, and heat preservation time of 15-60min.

13. The preparation method according to claim 12, wherein: The calcination operation conditions include: vacuum degree ≤ 5 Pa, heating rate of 50-100° C. / min, temperature of 1600-1800° C., and heat preservation time of 20-40 min.

14. The preparation method according to claim 6, wherein: The temperature of the high temperature heat treatment is 1600-1700°C.

15. The preparation method according to claim 14, wherein: The vacuum degree of the high temperature heat treatment is ≤10Pa, the heating rate is 30-150°C / min, and the heat preservation time is 15-60min.

16. The preparation method according to claim 15, wherein: The vacuum degree of the high temperature heat treatment is ≤5Pa, the heating rate is 50-100°C / min, and the insulation time is 20-40min.

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