Boron-containing nitrogen-containing carbide and method for producing the same

Abstract

This invention relates to the field of high-entropy, ultra-high temperature carbide ceramics technology, and discloses a boron- and nitrogen-containing carbide and its preparation method. The molecular formula of the boron- and nitrogen-containing carbide 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 boron-nitrogen-containing carbide is a single-phase solid solution with a face-centered cubic structure. The boron-nitrogen-containing carbide provided in this invention possesses both ultra-high melting point temperature resistance and oxidation resistance, and has important potential applications in ultra-high temperature thermal protection systems.

Description

Technical Field

[0001] This invention relates to the field of high-entropy ultra-high temperature carbide ceramics technology, specifically to a boron- and nitrogen-containing carbide and its preparation method. Background Technology

[0002] Ultra-high temperature ceramics possess advantages such as high melting point, high stability, and high high-temperature strength, making them suitable for components like the nose cone and wingtips of hypersonic vehicles, and the throat liner and diffuser section of rockets. They are important candidate materials for the thermal protection systems of space shuttles and strategic missiles. Based on their entropy value (S), ultra-high temperature ceramics are typically classified 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), where R is the gas constant.

[0003] High-entropy ultra-high temperature ceramics typically refer to solid solutions formed by five or more ceramic components. Due to their novel "high-entropy effect" and excellent properties, they have become one of the research hotspots in the ceramics field in recent years. CN109180188A discloses a high-entropy boron-containing carbide ultra-high temperature ceramic powder with the molecular formula XC. y B z The molecule is a single-phase face-centered cubic structure, where 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, and y + z = 1. This ceramic powder is a single-phase solid solution with a face-centered cubic structure and contains boron, possessing both the high-temperature resistance of carbides and the oxidation resistance of boron compounds. It can be used to prepare high-entropy boron-containing carbide ultra-high-temperature ceramic bulks or composite materials resistant to ablation and oxidation. However, during the oxidation and ablation process, boron in this boron-containing carbide will oxidize to form boron oxide. At temperatures above its boiling point (1860℃), the volatilization of a large amount of boron oxide will cause defects such as pores and cracks, which is detrimental to the ablation resistance of boron-containing carbides. Therefore, the ablation resistance of high-entropy boron-containing carbide ceramics still needs further improvement.

[0004] Wen et al. synthesized a carbide solid solution containing N and C (Hf 0.2 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 Nb0.2 Ti 0.2 (C) 0.8 N 0.2 (Peng Z, et al. Corrosion Science, 2021, 184: 109359). Their research results indicate that nitrogen doping enables carbide ceramics to form stronger chemical bonds, resulting in higher ablation resistance.

[0005] Introducing nitrogen into high-entropy boron-containing carbide ultra-high temperature ceramic powder can improve its ablation resistance. However, the introduction of nitrogen easily leads to the formation of new phases. Currently, there are no reports on methods for preparing single-phase boron-nitrogen-containing high-entropy carbide ceramics. This is because nitrogen has a lower reaction free energy with metals in Groups IV and V of the periodic table. Compared with carbon (C) and boron (B), nitrogen preferentially forms stable nitrides, making it difficult for C and B to further dissolve into the carbide. Consequently, the introduced C and B do not undergo solid solution but react with the metal to form a second phase.

[0006] Guan et al. (GUAN J, et al. Journal of the American Ceramic Society, 2022, 105(10): 6417-6426) prepared boron-nitrogen-containing carbide multiphase ceramics by mixing various metal powders and amorphous BCN powders through high-energy ball milling and hot-pressing at 1900℃. However, the phases of this boron-nitrogen-containing carbide multiphase ceramic were not unique, including BN(C) phase, (Ta) phase, etc. 0.2 Nb 0.2 Zr 0.2 Hf 0.2 Ti 0.2 The literature describes the preparation of (B,C,N) phases and oxide phases, and the emergence of a new phase, MB2, as the amount of BCN added decreases. However, it does not address how to prepare phases containing only (Ta) 0.2 Nb 0.2 Zr 0.2 Hf 0.2 Ti 0.2 Correlation methods for (B,C,N) phases.

[0007] Therefore, there is an urgent need to provide a boron-nitrogen carbide with a single phase that does not destroy the face-centered cubic structure of the carbide and contains both boron and nitrogen elements, as well as a method for its preparation. Summary of the Invention

[0008] The purpose of this invention is to solve the problem of poor ablation resistance of high-entropy boron-containing carbide ultra-high temperature ceramic powder, and to provide a boron- and nitrogen-containing carbide and its preparation method.

[0009] To achieve the above objectives, a first aspect of the present invention provides a boron-nitrogen-containing carbide, wherein the molecular formula of the boron-nitrogen-containing carbide is XC. y B z N w X is at least four of Zr, Hf, Ti, Ta, Nb, V, and W, with 0.6 ≤ y < 1, 0 < z ≤ 0.4, 0 < w ≤ 0.4, and y + z + w ≤ 1. The boron- and nitrogen-containing carbides are single-phase solid solutions with a face-centered cubic structure.

[0010] Preferably, X is 4 or 5 of Zr, Hf, Ti, Ta, Nb, V, and W.

[0011] Preferably, X is Zr, Hf, Ti, and Ta, or X is Zr, Hf, Ti, Ta, and Nb.

[0012] Preferably, 0.75≤y≤0.95, 0.01≤z≤0.15, 0.05≤w≤0.15, and y+z+w≤1.

[0013] Preferably, the molecular formula of the boron- and nitrogen-containing carbide 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 One or more of the following.

[0014] A second aspect of the present invention provides a method for preparing boron- and nitrogen-containing carbides, wherein the method includes the following steps:

[0015] (1) The metal powder and carbon powder are mixed and then ground 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;

[0016] (2) The mixed powder is subjected to pressureless discharge plasma sintering to obtain carbide powder;

[0017] (3) Under vacuum conditions, the carbide powder is mixed with B2O3 powder and then calcined to obtain boron-containing carbide powder;

[0018] (4) Under vacuum conditions, the boron-containing carbide powder is mixed with g-C3N4 powder and then subjected to high-temperature heat treatment to obtain boron-nitrogen-containing carbides; wherein the temperature of the high-temperature heat treatment is 1500-1800℃.

[0019] The molecular formula of the boron- and nitrogen-containing carbides is XC. y B z N w X is a metal, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, y+z+w≤1.

[0020] Preferably, the metal powder is selected from four or five of the following: Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder, and W powder.

[0021] 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.

[0022] Preferably, 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 h, a ball milling medium of ethanol and / or water, and a ball-to-material ratio of 6-10:1.

[0023] Preferably, the operating conditions for the pressureless discharge plasma sintering include: vacuum degree ≤10Pa, heating rate of 50-150℃ / min, temperature of 1300-1800℃, and holding time of 15-60min.

[0024] Preferably, the operating conditions for the pressureless discharge plasma sintering include: vacuum degree ≤ 5 Pa, heating rate of 80-120℃ / min, temperature of 1500-1700℃, and holding time of 20-40 min.

[0025] Preferably, the calcination operating conditions include: vacuum degree ≤10Pa, heating rate of 30-150℃ / min, temperature of 1400-1900℃, and holding time of 15-60min.

[0026] Preferably, the calcination operating conditions include: vacuum degree ≤ 5 Pa, heating rate of 50-100℃ / min, temperature of 1600-1800℃, and holding time of 20-40 min.

[0027] Preferably, the temperature of the high-temperature heat treatment is 1600-1700℃.

[0028] Preferably, the vacuum degree of the high-temperature heat treatment is ≤10Pa, more preferably ≤5Pa; the heating rate is 30-150℃ / min, more preferably 50-100℃ / min; and the holding time is 15-60min, more preferably 20-40min.

[0029] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0030] 1) The boron-nitrogen-containing carbides provided in this invention contain both B and N elements, and have a single phase with a face-centered cubic structure, exhibiting excellent ablation resistance and oxidation resistance.

[0031] 2) The method for preparing boron- and nitrogen-containing carbides provided in this invention has a short preparation time, is easy to control the reaction process, and introduces no impurities. It is beneficial to optimize the design of the content of each component and obtain a high-purity single-phase solid solution. Attached Figure Description

[0032] Figure 1 These are the microstructure and elemental surface scan diagrams of the boron- and nitrogen-containing carbides prepared in Example 1;

[0033] Figure 2 This is the XRD pattern of the boron- and nitrogen-containing carbides prepared in Example 1;

[0034] Figure 3 The XRD pattern of the boron- and nitrogen-containing carbides prepared in Comparative Example 1 is shown.

[0035] Figure 4 This is the XRD pattern of the boron-containing carbide prepared in Comparative Example 2. Detailed Implementation

[0036] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] A first aspect of the present invention provides a boron-nitrogen-containing carbide, wherein the molecular formula of the boron-nitrogen-containing carbide is XC.y B z N w X is at least four of Zr, Hf, Ti, Ta, Nb, V, and W, with 0.6 ≤ y < 1, 0 < z ≤ 0.4, 0 < w ≤ 0.4, and y + z + w ≤ 1; the boron- and nitrogen-containing carbides are single-phase solid solutions with a face-centered cubic structure.

[0038] In this invention, the boron-nitrogen carbide contains both B and N elements, has a single phase, a face-centered cubic structure, and exhibits excellent ablation resistance and oxidation resistance.

[0039] In a preferred embodiment of the present invention, X is four or five of Zr, Hf, Ti, Ta, Nb, V, and W.

[0040] In this invention, Zr, Hf, Ti, Ta, Nb, V, and W can form a solid solution. While the invention limits the number of elements X, it does not specifically limit the proportions of the various metals in X. For example, X can be any proportion of Zr, Hf, Ti, and Ta, or any proportion of Zr, Hf, Ti, Ta, and Nb. Preferably, the composition of all metals in X is the same.

[0041] In a preferred embodiment of the present invention, y can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.9, 0.95, 0.96, 0.97, 0.98, 0.99, 0.999, or any number between these values. Preferably, 0.75 ≤ y ≤ 0.95.

[0042] 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, or any number between these values. Preferably, 0.01 ≤ z ≤ 0.15.

[0043] 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, or any number between these values. Preferably, 0.05 ≤ w ≤ 0.15.

[0044] In a preferred embodiment of the present invention, the molecular formula of the boron- and nitrogen-containing carbide is (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 (C) 0.82B 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 One or more of the following.

[0045] The boron-nitrogen carbides provided in this invention combine the high melting point and temperature resistance of carbides and nitrides with the oxidation resistance of borides, and have important potential applications in ultra-high temperature thermal protection systems.

[0046] A second aspect of the present invention provides a method for preparing boron- and nitrogen-containing carbides, wherein the method includes the following steps:

[0047] (1) The metal powder and carbon powder are mixed and then ground 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;

[0048] (2) The mixed powder is subjected to pressureless discharge plasma sintering to obtain carbide powder;

[0049] (3) Under vacuum conditions, the carbide powder is mixed with B2O3 powder and then calcined to obtain boron-containing carbide powder;

[0050] (4) Under vacuum conditions, the boron-containing carbide powder is mixed with g-C3N4 powder and then subjected to high-temperature heat treatment to obtain boron-nitrogen-containing carbides; wherein the temperature of the high-temperature heat treatment is 1500-1800℃.

[0051] The molecular formula of the boron- and nitrogen-containing carbides is XC. y B z N w X is a metal, 0.6≤y<1, 0<z≤0.4, 0<w≤0.4, y+z+w≤1.

[0052] In this invention, the carbon (C) in the g-C3N4 powder is mainly used to react with the oxygen (O) introduced by the B2O3 powder to eliminate the O element. If there is still g-C3N4 powder remaining after eliminating the oxygen element, the excess g-C3N4 powder will dissolve into the boron- and nitrogen-containing carbides during the preparation process, but will not form a second phase. Therefore, by adjusting the feeding amounts of metal powder, carbon powder, B2O3 powder, and g-C3N4 powder, a material with the molecular formula XC can be prepared. y B z N w Boron- and nitrogen-containing carbides.

[0053] In step (1):

[0054] In a preferred embodiment of the present invention, the metal powder is selected from four or five of the following: Zr powder, Hf powder, Ti powder, Ta powder, Nb powder, V powder, and W powder.

[0055] In this invention, the mixing ratio of metal powders is not specifically limited, and the amount of each metal powder can be adjusted according to actual needs. Preferably, the amount of each metal powder in X is the same.

[0056] In a preferred embodiment of the present invention, the metal powder is Zr powder, Hf powder, Ti powder and Ta powder, or Zr powder, Hf powder, Ti powder, Ta powder and Nb powder.

[0057] In a preferred embodiment of the present invention, the purity of both the metal powder and the carbon powder is ≥98%, and both the metal powder and the carbon powder are micron-sized and / or nano-sized powders.

[0058] 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 1-5 h, ball milling medium of ethanol and / or water, and ball-to-material ratio of 6-10:1.

[0059] In a preferred embodiment of the present invention, the mixture is ball-milled and then dried to obtain a mixed powder. The drying temperature can be 30-60°C.

[0060] In step (2):

[0061] In a preferred embodiment of the present invention, the operating conditions for the pressureless discharge plasma sintering include: vacuum degree ≤10Pa, preferably ≤5Pa; heating rate 50-150℃ / min, preferably 80-120℃ / min; temperature 1300-1800℃, preferably 1500-1700℃; and holding time 15-60min, preferably 20-40min.

[0062] In this invention, by mixing metal powder and carbon powder and then performing pressureless discharge plasma sintering, a high-purity, low-free-carbon single-phase carbide solid solution powder material with non-stoichiometric carbon vacancy defects can be prepared. The formation of carbon vacancy defects can create conditions for the introduction of boron (B) and nitrogen (N) elements.

[0063] In a preferred embodiment of the present invention, after pressureless discharge plasma sintering, the sintered product is crushed and ball-milled to obtain carbide powder.

[0064] In this invention, the ball milling after pressureless discharge plasma sintering is preferably wet ball milling. The operating conditions of the wet ball milling include: the ball milling speed is 150-300 rpm, the time is 1-5 h, the ball milling medium is ethanol and / or water, and the ball-to-material ratio is 6-10:1.

[0065] In step (3):

[0066] In a preferred embodiment of the present invention, the purity of the B2O3 powder is ≥98%, and it is a micron-sized and / or nano-sized powder.

[0067] 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℃; and holding time of 15-60min, preferably 20-40min.

[0068] In step (4):

[0069] In a preferred embodiment of the present invention, the purity of both the powder and the g-C3N4 powder is ≥98%, and the powder is micron-sized and / or nano-sized.

[0070] In this invention, the inventors discovered through research that using g-C3N4 powder as a nitrogen source has the following advantages: Firstly, the C in g-C3N4 can consume the O element introduced by B2O3 powder, thus avoiding the formation of metal oxide phases. Secondly, 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.

[0071] In a preferred embodiment of the present invention, the temperature of the high-temperature heat treatment is preferably 1600-1700℃.

[0072] 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℃ / min, preferably 50-100℃ / min; and the holding time is 15-60min, preferably 20-40min.

[0073] In this invention, the calcination in step (3) and the high-temperature heat treatment in step (4) can be carried out under vacuum. There are no special limitations on the heating method and heating equipment. The heating equipment includes, but is not limited to, vacuum sintering furnaces, spark plasma sintering furnaces, high-temperature graphitization furnaces, muffle furnaces, etc. Preferably, the calcination in step (3) and the high-temperature heat treatment in step (4) are carried out in a vacuum sintering furnace, both of which are pressureless sintering.

[0074] 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.

[0075] The method for preparing boron- and nitrogen-containing carbides provided in this invention uses B2O3 powder as the B source and g-C3N4 powder as the N source. This ensures that the synthesized boron- and nitrogen-containing carbides are free of impurity elements and do not generate other phases. It not only yields high-purity single-phase solid solutions but also shortens the preparation time, reduces the difficulty of controlling the preparation process, and is more conducive to optimizing the design of the content of each component, significantly improving the ablation resistance and oxidation resistance of boron- and nitrogen-containing carbides.

[0076] The present invention will be described in detail below through examples. In the examples and comparative examples, Zr powder, Hf powder, Ti powder, Ta powder, Nd powder, carbon powder, B2O3 powder and g-C3N4 powder are all micron-sized powders with a purity of ≥99%.

[0077] Example 1

[0078] (1) Zr powder, Hf powder, Ti powder, Ta powder and C powder are mixed in a molar ratio of 0.25:0.25:0.25:0.25:0.8 and then ball-milled in a planetary ball mill for 2 h. The ball milling medium is ethanol, the rotation speed is 200 rpm, and the ball-to-material ratio is 6:1. After ball milling, the mixture is taken out, dried at 40℃, and sieved to obtain mixed powder.

[0079] (2) The above mixed powder was placed in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1600℃ at a heating rate of 100℃ / min and held for 30 min. Then it was cooled to room temperature, crushed, and ball-milled into powder in a ball mill. The ball milling medium was ethanol, the rotation speed was 200 rpm, the ball-to-material ratio was 6:1, and the ball milling time was 0.5 h. After ball milling, it was taken out and dried at 40℃ to obtain carbide powder.

[0080] (3) Based on the B element in B2O3 powder and the C element in carbide powder, B2O3 powder and the above carbide powder are mixed in ethanol at a molar ratio of 0.1:0.8. After 24 hours, the mixture is taken out and dried at 40°C. Then it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1600°C at a heating rate of 50°C / min and held for 30 min. Then it is cooled to room temperature and taken out to obtain boron-containing carbide powder.

[0081] (4) Based on the N element in g-C3N4 powder and the C element in boron-containing carbide powder, g-C3N4 powder and boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.1:0.8. After 24 hours, the mixture is taken out and dried at 40°C. Then, it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1700°C at a heating rate of 50°C / min and held for 30 min. Then, it is cooled to room temperature and taken out to obtain boron-containing and nitrogen-containing carbide powder.

[0082] Figure 1 The figures show the microstructure and elemental surface scan analysis of the boron-nitrogen-containing carbides prepared in Example 1. The figures show that the boron-nitrogen-containing carbide powder has a particle size of ~100 nm. The elemental surface scan results show that the powder contains Zr, Hf, Ti, Ta, C, B, and N elements, with uniform elemental distribution, indicating that the boron-nitrogen-containing carbide powder has formed a solid solution.

[0083] ICP-OES elemental 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 0.82:0.10:0.08. The molecular formula of the boron- and nitrogen-containing carbide powder was (Zr... 0.25 Hf 0.25 Ti 0.25 Ta 0.25 (C) 0.82 B 0.10 N 0.08 ).

[0084] Example 2

[0085] (1) Zr powder, Hf powder, Ti powder, Ta powder, Nd powder and C powder are mixed in a molar ratio of 0.2:0.2:0.2:0.2:0.2:0.9 and then ball-milled in a planetary ball mill for 2 h. The ball milling medium is ethanol, the rotation speed is 150 rpm, and the ball-to-material ratio is 6:1. After ball milling, the mixture is taken out, dried at 40℃, and sieved to obtain the mixed powder.

[0086] (2) The above mixed powder was placed in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1600℃ at a heating rate of 100℃ / min and held for 30 min. Then it was cooled to room temperature, crushed, and ball-milled into powder in a ball mill. The ball milling medium was ethanol, the rotation speed was 200 rpm, the ball-to-material ratio was 6:1, and the ball milling time was 0.5 h. After ball milling, it was taken out and dried at 40℃ to obtain carbide powder.

[0087] (3) Based on the B element in B2O3 powder and the C element in carbide powder, B2O3 powder and the above carbide powder are mixed in ethanol at a molar ratio of 0.1:0.9. After 24 hours, the mixture is taken out and dried at 40°C. Then it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1800°C at a heating rate of 100°C / min and held for 30 min. Then it is cooled to room temperature and taken out to obtain boron-containing carbide powder.

[0088] (4) Based on the N element in g-C3N4 powder and the C element in boron-containing carbide powder, g-C3N4 powder and boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.1:0.9. After 24 hours, the mixture is taken out and dried at 40°C. Then, it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1600°C at a heating rate of 100°C / min and held for 30 min. Then, it is cooled to room temperature and taken out to obtain boron-containing and nitrogen-containing carbide powder.

[0089] ICP-OES elemental analysis showed that the atomic ratio of Zr, Hf, Ti, Ta, and Nb was 0.2:0.2:0.2:0.2:0.2, and the atomic ratio of C, B, and N was 0.90:0.03:0.70. The molecular formula of the boron- and nitrogen-containing carbide powder was (Zr... 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 (C) 0.90 B 0.03 N 0.07 ).

[0090] Example 3

[0091] (1) Zr powder, Hf powder, Ti powder, Ta powder and C powder are mixed in a molar ratio of 0.4:0.2:0.2:0.2:0.7 and then ball-milled in a planetary ball mill for 2 h. The ball milling medium is ethanol, the rotation speed is 200 rpm, and the ball-to-material ratio is 6:1. After ball milling, the mixture is taken out, dried at 40℃, and sieved to obtain the mixed powder.

[0092] (2) The above mixed powder was placed in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1800℃ at a heating rate of 60℃ / min and held for 15 min. Then it was cooled to room temperature, crushed, and ball-milled into powder in a ball mill. The ball milling medium was ethanol, the rotation speed was 200 rpm, the ball-to-material ratio was 6:1, and the ball milling time was 0.5 h. After ball milling, the powder was taken out and dried at 40℃ to obtain carbide powder.

[0093] (3) Based on the B element in B2O3 powder and the C element in carbide powder, B2O3 powder and the above carbide powder are mixed in ethanol at a molar ratio of 0.15:0.7. After 24 hours, the mixture is taken out and dried at 40°C. Then, it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1600°C at a heating rate of 30°C / min and held for 15 minutes. Then, it is cooled to room temperature and taken out to obtain boron-containing carbide powder.

[0094] (4) Based on the N element in g-C3N4 powder and the C element in boron-containing carbide powder, g-C3N4 powder and boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.15:0.7. After 24 hours, the mixture is taken out and dried at 40°C. Then, it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1800°C at a heating rate of 120°C / min and held for 15 min. Then, it is cooled to room temperature and taken out to obtain boron-containing and nitrogen-containing carbide powder.

[0095] ICP-OES elemental analysis showed that the atomic ratio of Zr, Hf, Ti, and Ta was 0.4:0.2:0.2:0.2, and the atomic ratio of C, B, and N was 0.70:0.15:0.15. The molecular formula of the boron- and nitrogen-containing carbide powder was (Zr... 0.4 Hf 0.2 Ti 0.2 Ta 0.2 (C) 0.70 B 0.15 N 0.15 ).

[0096] Example 4

[0097] (1) Zr powder, Hf powder, Ti powder, Ta powder, Nd powder and C powder are mixed in a molar ratio of 0.3:0.3:0.1:0.1:0.1:0.9 and then ball-milled in a planetary ball mill for 2 h. The ball milling medium is ethanol, the rotation speed is 150 rpm, and the ball-to-material ratio is 6:1. After ball milling, the mixture is taken out, dried at 40℃, and sieved to obtain the mixed powder.

[0098] (2) The above mixed powder was placed in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1400℃ at a heating rate of 140℃ / min and held for 50 min. Then it was cooled to room temperature, crushed, and ball-milled into powder in a ball mill. The ball milling medium was ethanol, the rotation speed was 200 rpm, the ball-to-material ratio was 6:1, and the ball milling time was 0.5 h. After ball milling, the powder was taken out and dried at 40℃ to obtain carbide powder.

[0099] (3) Based on the B element in B2O3 powder and the C element in carbide powder, B2O3 powder and the above carbide powder are mixed in ethanol at a molar ratio of 0.1:0.9. After 24 hours, the mixture is taken out and dried at 40°C. Then it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1500°C at a heating rate of 120°C / min and held for 50 min. Then it is cooled to room temperature and taken out to obtain boron-containing carbide powder.

[0100] (4) Based on the N element in g-C3N4 powder and the C element in boron-containing carbide powder, g-C3N4 powder and boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.1:0.9. After 24 hours, the mixture is taken out and dried at 40°C. Then, it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1500°C at a heating rate of 30°C / min and held for 50 minutes. Then, it is cooled to room temperature and taken out to obtain boron-containing and nitrogen-containing carbide powder.

[0101] ICP-OES elemental analysis showed that the atomic ratio of Zr, Hf, Ti, Ta, and Nb was 0.3:0.3:0.2:0.1:0.1, and the atomic ratio of C, B, and N was 0.87:0.06:0.07. The molecular formula of the boron- and nitrogen-containing carbide powder was (Zr... 0.3 Hf 0.3 Ti 0.2 Ta 0.1 Nb 0.1 (C) 0.87 B 0.06 N 0.07 ).

[0102] Comparative Example 1

[0103] Similar to Example 1, except that in step (4), the vacuum sintering furnace is heated to 1300°C at a heating rate of 30°C / min.

[0104] (1) Zr powder, Hf powder, Ti powder, Ta powder and C powder are mixed in a molar ratio of 0.25:0.25:0.25:0.25:0.8 and then ball-milled in a planetary ball mill for 2 h. The ball milling medium is ethanol, the rotation speed is 200 rpm, and the ball-to-material ratio is 6:1. After ball milling, the mixture is taken out, dried at 40℃, and sieved to obtain mixed powder.

[0105] (2) The above mixed powder was placed in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1600℃ at a heating rate of 100℃ / min and held for 30 min. Then it was cooled to room temperature, crushed, and ball-milled into powder in a ball mill. The ball milling medium was ethanol, the rotation speed was 200 rpm, the ball-to-material ratio was 6:1, and the ball milling time was 0.5 h. After ball milling, it was taken out and dried at 40℃ to obtain carbide powder.

[0106] (3) Based on the B element in B2O3 powder and the C element in carbide powder, B2O3 powder and the above carbide powder are mixed in ethanol at a molar ratio of 0.1:0.8. After 24 hours, the mixture is taken out and dried at 40°C. Then it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1600°C at a heating rate of 50°C / min and held for 30 min. Then it is cooled to room temperature and taken out to obtain boron-containing carbide powder.

[0107] (4) Based on the N element in g-C3N4 powder and the C element in boron-containing carbide powder, g-C3N4 powder and boron-containing carbide powder are mixed in deionized water at a molar ratio of 0.1:0.8. After 24 h, the mixture is taken out and dried at 40 °C. Then, it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1300 °C at a heating rate of 50 °C / min and held for 30 min. Then, it is cooled to room temperature and taken out to obtain boron-containing and nitrogen-containing carbide powder.

[0108] Comparative Example 2

[0109] Same as Example 1, except that step 4 is omitted and a carbon source is added in step 3.

[0110] (1) Zr powder, Hf powder, Ti powder, Ta powder and C powder are mixed in a molar ratio of 0.25:0.25:0.25:0.25:0.8 and then ball-milled in a planetary ball mill for 2 h. The ball milling medium is ethanol, the rotation speed is 200 rpm, and the ball-to-material ratio is 6:1. After ball milling, the mixture is taken out, dried at 40℃, and sieved to obtain mixed powder.

[0111] (2) The above mixed powder was placed in a pressureless discharge plasma sintering graphite mold for pressureless discharge plasma sintering. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1600℃ at a heating rate of 100℃ / min and held for 30 min. Then it was cooled to room temperature, crushed, and ball-milled into powder in a ball mill. The ball milling medium was ethanol, the rotation speed was 200 rpm, the ball-to-material ratio was 6:1, and the ball milling time was 0.5 h. After ball milling, the powder was taken out and dried at 40℃ to obtain carbide powder.

[0112] (3) Based on the B element in B2O3 powder and the C element in carbide powder, B2O3 powder and the above carbide powder are mixed in ethanol at a molar ratio of 0.1:0.8. 6 wt% phenolic resin of the total mass of the powder is added. After 24 h, it is taken out and dried at 40°C. Then it is placed in a graphite jar and sintered in a vacuum sintering furnace without pressure. The vacuum degree in the furnace is less than 5 Pa. The temperature is raised to 1600°C at a heating rate of 50°C / min and held for 30 min. Then it is cooled to room temperature and taken out to obtain boron-containing carbide powder.

[0113] ICP-OES elemental 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- and nitrogen-containing carbide powder was (Zr... 0.25 Hf 0.25 Ti 0.25 Ta 0.25 (C) 0.83 B 0.10 ).

[0114] Test Example 1

[0115] The powders prepared in Example 1 and Comparative Examples 1-2 were characterized by XRD, and the characterization results are as follows: Figure 2-4 As shown.

[0116] Figure 2 The image shows the XRD pattern of the boron-nitrogen-containing carbide powder prepared in Example 1. Figure 2 It can be seen that the boron- and nitrogen-containing carbide powder single-phase solid solution prepared in Example 1 has a face-centered cubic structure.

[0117] Figure 3The image shows the XRD pattern of the boron- and nitrogen-containing carbide powder prepared in Comparative Example 1. Figure 3 It can be seen that the boron-nitrogen carbide powder prepared in Comparative Example 1 exhibits diffraction peaks of Zr-Hf-Ti-Ta-CBN solid solution, HfO2, and g-C3N4, indicating that the powder is a mixture of these three substances. Among them, the Zr-Hf-Ti-Ta-CBN solid solution shows the characteristic peak of ZrC, indicating that when the high-temperature heat treatment temperature is low, the reaction between g-C3N4 and the O introduced by B2O3 is incomplete, and the final powder contains oxide impurity HfO2, and the powder cannot form a single phase of boron-nitrogen carbide.

[0118] Figure 4 The image shows the XRD pattern of the boron-containing carbide powder prepared in Comparative Example 2. Figure 4 It can be seen that the boron-containing carbide powder single-phase solid solution has a face-centered cubic structure.

[0119] Test Example 2

[0120] The ablation performance and antioxidant performance of the products prepared in Example 1 and Comparative Example 2 were tested, and the test results are shown in Table 1:

[0121] In this study, the boron-nitrogen-containing carbide powder prepared in Example 1 and the boron-containing carbide powder prepared in Comparative Example 2 were sintered under vacuum conditions (<5 Pa) at a heating rate of 100℃ / min to 1900℃, and held at 50 MPa for 10 min to obtain bulk ceramics with a relative density >95%. The ablation performance of the bulk ceramics was tested in a plasma ablation apparatus, and the mass ablation rate (%) was calculated based on the mass change of the ceramics before and after ablation. The ablation temperature was 2500℃, and the ablation time was 60 s. A lower mass ablation rate indicates better ablation resistance of the product.

[0122] The antioxidant properties of the products prepared in Example 1 and Comparative Example 2 were tested using TG-DSC in an air atmosphere. The heating rate was 10 °C / min, the product particle size was 5 μm, and the initial oxidation temperature was read from the DSC heating curves. A higher initial oxidation temperature indicates better antioxidant properties of the product.

[0123] Table 1

[0124]

[0125] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A boron- and nitrogen-containing carbide, characterized in that, The molecular formula of the boron- and nitrogen-containing carbide 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 boron-nitrogen-containing carbide is a single-phase solid solution with a face-centered cubic structure; wherein, the preparation method of the boron-nitrogen-containing carbide includes: (1) The metal powder and carbon powder are mixed and then ground 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) The mixed powder is subjected to pressureless discharge plasma sintering to obtain carbide powder; (3) Under vacuum conditions, the carbide powder is mixed with B2O3 powder and then calcined to obtain boron-containing carbide powder; (4) Under vacuum conditions, the boron-containing carbide powder is mixed with g-C3N4 powder and then subjected to high-temperature heat treatment to obtain boron-nitrogen-containing carbides; wherein the temperature of the high-temperature heat treatment is 1500-1800℃.

2. The boron- and nitrogen-containing carbide according to claim 1, wherein, X can be any 4 or 5 of Zr, Hf, Ti, Ta, Nb, V, and W.

3. The boron- and nitrogen-containing carbides according to claim 2, wherein, X can be Zr, Hf, Ti, or Ta, or X can be Zr, Hf, Ti, Ta, or Nb.

4. The boron- and nitrogen-containing carbide 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 boron- and nitrogen-containing carbide according to claim 1, wherein, The molecular formula of the boron- and nitrogen-containing carbide 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 One or more of the following.

6. A method for preparing boron- and nitrogen-containing carbides, characterized in that, The method includes the following steps: (1) The metal powder and carbon powder are mixed and then ground 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) The mixed powder is subjected to pressureless discharge plasma sintering to obtain carbide powder; (3) Under vacuum conditions, the carbide powder is mixed with B2O3 powder and then calcined to obtain boron-containing carbide powder; (4) Under vacuum conditions, the boron-containing carbide powder is mixed with g-C3N4 powder and then subjected to high-temperature heat treatment to obtain boron-nitrogen-containing carbides; wherein the temperature of the high-temperature heat treatment is 1500-1800℃.

7. The preparation method according to claim 6, wherein, The metal powder is selected from four or five of the following: 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 h, 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 for the pressureless discharge plasma sintering include: vacuum degree ≤10Pa, heating rate of 50-150℃ / min, temperature of 1300-1800℃, and holding time of 15-60min.

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

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

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

14. The preparation method according to claim 6, wherein, The high-temperature heat treatment temperature is 1600-1700℃.

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℃ / min; and the holding 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℃ / min; and the holding time is 20-40min.

Images