Non-stoichiometric high-entropy boron-containing carbide powder, preparation method therefor and use thereof

Abstract

Provided in the present application are a non-stoichiometric high-entropy boron-containing carbide powder, a preparation method therefor and the use thereof. The powder comprises a substance having a molecular formula of XCyBz, wherein the X element is selected from at least four of Zr, Hf, Ti, Ta, Nb, V and W, 0.6≤y＜1.0, 0＜z＜0.4 and y+z≤0.96. The powder has a single-phase face-centered cubic structure, a particle size of ≤1μm, and an oxygen content of not more than 0.2 wt%. The powder provided by the present application has the characteristics of high-temperature resistance and high oxidation resistance, and thus can be used for preparing high-density, oxidation-resistant and ablation-resistant ceramic blocks or coatings.

Description

Non-stoichiometric high-entropy boride-containing carbide powder, preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202411246802.0 filed on September 5, 2024, and entitled "Non-stoichiometric high-entropy boride-containing carbide powder, preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to a non-stoichiometric high-entropy boride-containing carbide powder, in particular to a non-stoichiometric high-entropy boride-containing carbide powder, a preparation method and an application thereof, and belongs to the technical field of ceramic materials. BACKGROUND

[0003] In the petroleum and petrochemical industry, the surface of downhole drill bits and high-temperature corrosion components needs to face extreme high temperatures and strong corrosive media, etc. Carbide ceramics have high melting points, high stability and high-temperature strength, and the use life of key equipment can be extended by forming a protective coating with carbide ceramics. At the same time, the high melting point of carbide ceramics also makes it an important candidate material for extreme environment thermal protection systems in aerospace. However, the poor oxidation resistance of traditional binary carbide ceramics has affected their potential applications. For example, ZrC will be oxidized into a loose and porous zirconia layer below 1200℃, which has poor oxygen barrier ability.

[0004] Boron-containing carbide is a new type of carbide formed by boron atoms dissolving into carbide to occupy carbon vacancies, which has a stable face-centered cubic structure. It has both the temperature-resistant properties of carbide with ultra-high melting point and the oxidation-resistant properties of boride, which can well solve the problem of poor oxidation resistance of carbide and has important potential applications in high-temperature thermal protection. Currently, there are few reports on boron-containing carbide. Zeng et al. (Zeng Y, Wang D, Xiong X, et al. Ablation-resistant carbide Zr 0.8 Ti 0.2 C 0.74 B 0.26 for oxidizing environments up to 3,000℃. Nature Communications, 2017, 8: 15836.) reported a C / C-(Zr 0.8 Ti 0.2 )(C 0.74 B 0.26 ) composite material. The ceramic phase (Zr 0.8 Ti 0.2 )(C 0.74 B 0.26This material is a boron-containing carbide solid solution in which Ti atoms replace some Zr atoms and B atoms fill carbon vacancies. It exhibits excellent ablation resistance and thermal shock resistance under oxidation conditions up to 3000℃, making it a very promising ultra-high temperature thermal protection material. However, this report does not involve the preparation of high-purity boron-containing carbide ceramic materials.

[0005] Transition metal carbides possess non-stoichiometric structural characteristics, enabling them to maintain a high concentration of anion vacancies while retaining their original face-centered cubic structure. The presence of anion vacancies promotes atomic diffusion during sintering and lowers the sintering temperature. Furthermore, previous research (Lun H, Yuan J, Zeng Y, et al. Mechanisms responsible for enhancing low-temperature oxidation resistance of non-stoichiometric (Zr,Ti)C. Journal of the American Ceramic Society, 2022, 105(8): 5309-5324.) indicates that when the molar ratio of carbon to metal atoms is 0.8, (Zr... 0.8 Ti 0.2 C 0.8 Compared to the stoichiometric ratio (Zr) 0.8 Ti 0.2 C 0.8 It exhibits superior antioxidant properties due to the formation of a denser t-(Zr,Ti)O2 solid solution oxide layer, which effectively slows down the internal diffusion of oxygen and protects the internal carbide matrix from further oxidation. It is foreseeable that non-stoichiometric boron-containing carbides will effectively improve antioxidant properties. Patent CN109180188 invented a high-entropy boron-containing carbide ultra-high temperature ceramic powder and its preparation method. The boron-containing carbide is prepared by solid-phase diffusion method. The process involves ball milling and mixing metal powder and carbon powder, followed by pressureless plasma sintering and crushing to obtain carbide powder. The powder is then mixed with B2O3 powder and carbon source, sintered at high temperature, and crushed into powder. The powder particle size is above the micron level. Subsequent sintering conditions are required to densify the powder to form a ceramic bulk material. The powder preparation cycle is long and the process is relatively complex.

[0006] The particle size and carbon content of boron carbide powders affect the difficulty of subsequent sintering. In order to reduce the densification conditions of boron carbide ceramics, simplify the current boron carbide preparation process, and improve the oxidation resistance of boron carbides, there is an urgent need for a simple method to prepare non-stoichiometric boron carbide ultrafine powders. Summary of the Invention

[0007] The application provides a non-stoichiometric high-entropy boride-carbide powder, which has the characteristics of high-temperature resistance, strong oxidation resistance, and can be used for preparing a high-density, ablation-resistant and oxidation-resistant ceramic bulk or coating.

[0008] The application also provides a preparation method of the non-stoichiometric high-entropy boride-carbide powder, and the non-stoichiometric high-entropy boride-carbide powder can be prepared by the method.

[0009] The application also provides a ceramic material, which has the characteristics of high density, ablation resistance and strong oxidation resistance.

[0010] The application provides a non-stoichiometric high-entropy boride-carbide powder, wherein the powder comprises a substance with a molecular formula of XC y B z ;

[0011] wherein X elements are selected from at least four of Zr, Hf, Ti, Ta, Nb, V and W, 0.6≤y<1.0, 0

[0012] The powder has a single-phase face-centered cubic structure, a particle size of ≤1 μm, and an oxygen content of not higher than 0.2 wt%.

[0013] The powder as described above, wherein the X elements are selected from four or five of Zr, Hf, Ti, Ta, Nb, V and W.

[0014] The powder as described above, wherein the X elements consist of Zr, Hf, Ti and Ta; or,

[0015] The X elements consist of Zr, Hf, Ti, Ta and Nb.

[0016] The powder as described above, wherein 0.65≤y≤0.95, y+z≤0.95.

[0017] The powder as described above, wherein 0.20

[0018] The application also provides a preparation method of the high-entropy boride-carbide powder, and any of the high-entropy boride-carbide powders described above can be prepared by the method.

[0019] 1) mixing a salt solution comprising X elements with an alkaline substance to obtain a mixture system with a pH value of 7-8, and obtaining a precipitate comprising X elements;

[0020] 2) mixing the precipitate comprising X elements with a first carbon source, and performing carbonization treatment to obtain a carbide powder.

[0021] 3) mixing the carbide powder with a second carbon source in an organic solvent to obtain a second carbon source-carbide powder composite; mixing the second carbon source-carbide powder composite with boric acid to obtain a second carbon source-boric acid-carbide powder composite;

[0022] 4) sintering the second carbon source-boric acid-carbide powder composite to obtain a non-stoichiometric high-entropy boron-containing carbide powder;

[0023] The first carbon source is any one of phenolic resin and epoxy resin;

[0024] The second carbon source is any one of phenolic resin and epoxy resin;

[0025] The molar ratio of boron element in the boric acid to the X element is less than 0.4;

[0026] The ratio p of the mass of the boric acid to the mass of the carbide powder satisfies: 0 < p ≤ 0.2;

[0027] The molar ratio of carbon atoms in the first carbon source to metal atoms of the X element is (1+y):1.

[0028] The preparation method as described above, wherein the mass of the second carbon source is 0-2.5wt% of the mass of the carbide powder.

[0029] The preparation method as described above, wherein the molar ratio of carbon element in the second carbon source to boron element in the boric acid is 0.75:1-1:1.

[0030] The preparation method as described above, wherein the salt solution comprising the X element comprises a nitrate salt of the X element and / or a chloride salt of the X element;

[0031] The nitrate salt of the X element is selected from at least one of Zr(NO3)4, Hf(NO3)4, Ti(NO3)4, Ta(NO3)5 and Nb(NO3)5;

[0032] The chloride salt of the X element is selected from at least one of ZrCl4, HfCl4, TiCl4, TaCl5 and NbCl5.

[0033] The preparation method as described above, wherein the alkaline substance comprises at least one of NaOH, KOH and ammonia water.

[0034] The preparation method as described above, wherein the treatment temperature of the carbonization treatment is 1600-1900℃, the holding time is 20-40min, the vacuum degree is ≤5Pa, and the heating rate is 20-50℃ / min.

[0035] The preparation method as described above, wherein the sintering treatment is a pressureless spark plasma sintering treatment, the treatment temperature is 1300-1800℃, the holding time is 15-60min, the heating rate is 50-150℃ / min, and the vacuum degree is ≤10Pa.

[0036] The application further provides a ceramic material, wherein the ceramic material comprises any of the above non-stoichiometric high-entropy boride-containing carbide powders; and / or, the ceramic material is prepared from any of the above non-stoichiometric high-entropy boride-containing carbide powders.

[0037] The non-stoichiometric high-entropy boride-containing carbide powder provided by the application has the characteristics of high-temperature resistance, strong oxidation resistance, and can be used to prepare a high-density, ablation-resistant and oxidation-resistant ceramic bulk or coating. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments described in the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0039] Fig. 1 is an X-ray diffraction spectrum of high-entropy boride-containing carbide powder A1 prepared in Example 1;

[0040] Fig. 2 is a surface morphology of high-entropy boride-containing carbide powder A1;

[0041] Fig. 3 is an X-ray diffraction spectrum of high-entropy boride-containing carbide powder A2 prepared in Example 2;

[0042] Fig. 4 is an X-ray diffraction spectrum of powder B1;

[0043] Fig. 5 is a macroscopic morphology diagram of a high-entropy boride-containing carbide ceramic bulk prepared by sintering with powder A1 as raw material. DETAILED DESCRIPTION

[0044] In order to make those skilled in the art better understand the technical solutions of the application, the application will be further described in detail below. The following specific embodiments are only used to describe the principles and characteristics of the application, and the examples are used to explain the application, not to limit the scope of the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0045] The first aspect of the application provides a non-stoichiometric high-entropy boride-containing carbide powder, which comprises a molecular formula of XCB y B za substance of formula XC

[0046] wherein the X element is selected from at least four of Zr, Hf, Ti, Ta, Nb, V and W, 0.6≤y<1.0, 0

[0047] The powder has a single-phase face-centered cubic structure, a particle size of ≤1 μm, and an oxygen content of <0.2 wt%.

[0048] The powder provided in the present application is a boride, and the non-stoichiometric ratio means that the atoms (or ions) of each element constituting the powder can fluctuate within a certain range of proportion. The composition described above does not comply with the valence rule and is not subject to the law of composition, and can only be described by a decimal number, not a small integer.

[0049] The powder includes a substance of formula XC y B z That is, the powder can be composed of a substance of formula XC y B z , or can include multiple substances, but each substance satisfies the formula XC y B z .

[0050] Specifically, in the formula, the X element is selected from at least four of Zr, Hf, Ti, Ta, Nb, V and W. In the powder provided in the present application, the X element can be selected from four, five, six or seven of the above-mentioned elements. Further, in the powder provided in the present application, 0.6≤y<1.0, 0

[0051] The non-stoichiometric high-entropy boride powder provided in the present application has a non-stoichiometric ratio, a low particle size, a certain carbon vacancy in the crystal lattice, high stability of the compound structure, a dense oxidation layer generated by oxidation, a reduced oxygen inward diffusion speed, and the characteristics of high-temperature resistance, strong oxidation resistance, and being capable of being used to prepare a high-density, ablation-resistant and oxidation-resistant ceramic bulk or coating.

[0052] Further, in the non-stoichiometric high-entropy boride powder provided in the present application, the X element is selected from four or five of Zr, Hf, Ti, Ta, Nb, V and W; further, in the non-stoichiometric high-entropy boride powder provided in the present application, the X element is composed of Zr, Hf, Ti and Ta; or, the X element is composed of Zr, Hf, Ti, Ta and Nb. The powder with the above-mentioned properties has more prominent characteristics of high-temperature resistance and oxidation resistance.

[0053] Furthermore, in the non-stoichiometric high-entropy boron-containing carbide powder provided in this application, 0.65≤y≤0.95, y+z≤0.95. Due to the presence of certain carbon vacancies in the crystal lattice, the compound structure has high stability, and the reduced stoichiometry of carbon leads to a denser oxide layer formed by oxidation. Therefore, the powder possessing the above properties exhibits more prominent characteristics of high-temperature resistance and oxidation resistance.

[0054] Furthermore, in the non-stoichiometric high-entropy boron-containing carbide powder provided in this application, 0.20 < z < 0.40. Powders with higher boron content exhibit more prominent characteristics of high-temperature resistance and oxidation resistance.

[0055] In one embodiment, the non-stoichiometric high-entropy boron-containing carbide powder provided in this application is composed of any substance having the following molecular formula:

[0056] (Zr 0.3 Hf 0.3 Ti 0.3 Ta 0.1 (C) 0.70 B 0.15 ), (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 (C) 0.80 B 0.10 ), (Zr 0.4 Hf 0.4 Ti 0.1 Ta 0.1 (C) 0.65 B 0.20 ), (Zr 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 (C) 0.90 B 0.05 Powders possessing the above properties are characterized by high temperature resistance and strong antioxidant properties.

[0057] A second aspect of this application provides a method for preparing non-stoichiometric high-entropy boron-containing carbide powder, which can be used to obtain any of the aforementioned non-stoichiometric high-entropy boron-containing carbide powders. The method includes the following steps:

[0058] 1) Mix a salt solution containing element X with an alkaline substance to make the pH of the resulting mixture 7-8, and obtain a precipitate containing element X.

[0059] 2) The precipitate containing element X is mixed with the first carbon source and subjected to carbonization treatment to obtain carbide powder;

[0060] 3) mixing the carbide powder with a second carbon source in an organic solvent to obtain a second carbon source-carbide powder composite; mixing the second carbon source-carbide powder composite with boric acid to obtain a second carbon source-boric acid-carbide powder composite;

[0061] 4) sintering the second carbon source-boric acid-carbide powder composite to obtain a non-stoichiometric high-entropy boron-containing carbide powder;

[0062] The first carbon source is at least one of phenolic resin and epoxy resin; the second carbon source is any one of phenolic resin and epoxy resin;

[0063] The molar ratio of boron in the boric acid to the X element is less than 0.4;

[0064] The ratio p of the mass of the boric acid to the mass of the carbide powder satisfies 0 < p ≤ 0.2.

[0065] The molar ratio of carbon atoms in the first carbon source to metal atoms of the X element is (1+y):1.

[0066] In the above description, the X element is the same as described above, i.e., the X element is selected from at least four of Zr, Hf, Ti, Ta, Nb, V, and W, i.e., the X element is a mixture of at least four elements, so that the salt solution including the X element in step 1) is an aqueous solution containing salts of at least four of the above-mentioned elements, and the precipitate including the X element prepared is an oxide, a hydroxide, or both of the above-mentioned substances of at least four elements. Since the oxide or the hydroxide of the above-mentioned elements are both insoluble in water, the precipitate including the X element in step 1) is separated from the liquid phase.

[0067] The basic substance is a substance that exhibits basicity in an aqueous solution. The application does not limit the specific selection of the basic substance, as long as it exhibits basicity in an aqueous solution. In an embodiment, the basic substance is selected from at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and ammonia water.

[0068] In the method provided by the application, the pH value of the mixing system is controlled to be 7-8 when the aqueous solution including the X element is mixed with the basic substance. The above-mentioned pH value can prepare the precipitate including the X element.

[0069] The first carbon source provides a carbon source for the carbonization process. In the method provided by the application, the first carbon source is any one of phenolic resin and epoxy resin. The carbonization process reacts the first carbon source with the X element hydroxide at high temperature to generate a carbide powder with carbon vacancies. The application does not make specific limitations on the conditions of the carbonization process, and common processing conditions in the art can be used. In an embodiment, the processing temperature of the carbonization process is not lower than 1600℃, and the holding time is not less than 20 min.

[0070] The second carbon source has two effects: one is that the second carbon source can coat the carbide powder to avoid the contact reaction between the carbide and boric acid to generate boride at high temperature; the other is that the second carbon source reduces and diffuses the boron element in the boric acid into the carbide crystal lattice, and reacts with excess oxygen to form CO / CO2 gas, and no second-phase oxide impurities are formed in the high-entropy boride-containing carbide powder, so that a high-entropy boride-containing carbide powder with high-temperature resistance and strong oxidation resistance can be prepared. In the method provided in the application, the second carbon source is any one of phenolic resin and epoxy resin.

[0071] The organic solvent is used for dissolving the boric acid. The method provided in the application does not specifically limit the type of the organic solvent in step 3), and in an embodiment, the organic solvent is ethanol.

[0072] It is worth noting that for the mixing of the second carbon source-carbide powder composite and the boric acid in step 3), the application does not limit the specific mixing method of the above process. In an embodiment, the second carbon source-carbide powder composite and the boric acid solid can be mixed and then dissolved in water, and in another embodiment, the second carbon source-carbide powder composite can be added to the prepared boric acid aqueous solution.

[0073] The sintering treatment can boronize the second carbon source-boric acid-carbide powder composite at high temperature. Specifically, the second carbon source reacts with the boric acid to reduce the boron in the boric acid to generate boron atoms, and because the coated carbide is a non-stoichiometric ratio, the crystal lattice contains carbon vacancies, and the boron atoms diffuse into the carbide to occupy a part of the carbon vacancies at high temperature, and finally generate a non-stoichiometric ratio boron-containing carbide.

[0074] The application does not limit the specific treatment conditions of the sintering treatment, and the commonly used treatment conditions in the art can be used. In an embodiment, the sintering treatment is pressureless discharge plasma sintering, the treatment temperature is not lower than 1300°C, and the holding time is not less than 15 min.

[0075] Further, in the method provided in the application, the molar ratio of the boron element to the X element in the boric acid is less than 0.4, the mass ratio p of the boric acid to the mass of the carbide powder satisfies 0

[0076] The application provides a preparation method of a non-stoichiometric high-entropy boron-containing carbide powder. The method comprises the following steps: synthesizing more than four transition metal cation hydroxides with similar particle sizes by a co-precipitation method; and preparing a non-stoichiometric high-entropy carbide superfine powder by high-temperature carbonization. On this basis, by adding boric acid as a boron source, boron atoms fill the designed carbon vacancies without changing the crystal structure of the carbide. Meanwhile, phenolic resin is selected as a carbon source to coat the surface of the carbide powder, and the interface between the carbide and the boric acid precipitate eliminates the excess oxygen brought by the boric acid and changes the high-temperature boronization reaction sequence to avoid the formation of boride impurities in high-temperature reaction. Finally, a single-phase high-entropy boron-containing carbide powder is formed, and the method has the characteristics of short preparation period and simple process.

[0077] Further, in the method provided in the application, the second carbon source is added in an amount of 0-2.5wt% (not including 0wt%) of the carbide powder. When the amount of the second carbon source is too much, after the elimination of excess oxygen, the excessive carbon will occupy the anion lattice in the carbide, so that the boron atoms can occupy fewer vacancy lattices in the carbide, and it is difficult to form a non-stoichiometric boron-containing carbide. However, when the amount of the carbon source is too low, the prepared powder contains a certain amount of oxide impurities, and it is difficult to form a single-phase boron-containing carbide.

[0078] Further, in an embodiment, the molar ratio of carbon elements in the second carbon source to boron elements in boric acid is 0.75:1-1:1. The appropriate molar ratio of boron elements to carbon elements in the second carbon source makes the prepared powder have higher high-temperature resistance and oxidation resistance.

[0079] In an embodiment, the salt solution containing the X element comprises at least one of a nitrate salt of the X element and / or a chloride salt of the X element, wherein the nitrate salt of the X element is selected from at least one of Zr(NO3)4, Hf(NO3)4, Ti(NO3)4, Ta(NO3)5 and Nb(NO3)5, and the chloride salt of the X element is selected from at least one of ZrCl4, HfCl4, TiCl4, TaCl5 and NbCl5. The above-mentioned salts have good water solubility, and can effectively introduce the X element into the powder synthesis system, so that the preparation method of the powder provided in the application has higher efficiency. The application does not limit the concentration of the above-mentioned X element salts in the salt solution containing the X element, as long as the powder can be prepared. Further, in an embodiment, the alkaline substance comprises at least one of NaOH, KOH and ammonia water.

[0080] In an embodiment, the carbonization treatment has a temperature of 1600-1900℃, a holding time of 20-40min, a vacuum degree of ≤5Pa, and a heating rate of 20-50℃ / min. The suitable carbonization treatment conditions can make the reaction between the first carbon source and the X element hydroxide have a higher reaction rate, and generate carbide powder with carbon vacancies. The efficiency of the powder preparation method provided in the present application is further improved.

[0081] Further, in an embodiment, the sintering treatment is a pressureless spark plasma sintering treatment, the sintering treatment has a temperature of 1300-1800℃, a holding time of 15-60min, a heating rate of 50-150℃ / min, and a vacuum degree of ≤10Pa. The above conditions can make the prepared non-stoichiometric high-entropy boride carbide powder have more prominent high-temperature resistance and strong oxidation resistance.

[0082] The third aspect of the present application provides a ceramic material, which comprises any of the non-stoichiometric high-entropy boride carbide powders described above; and / or, the ceramic material is prepared from any of the non-stoichiometric high-entropy boride carbide powders described above.

[0083] In an embodiment, the ceramic material comprises any of the non-stoichiometric high-entropy boride carbide powders provided in the first aspect of the present application. Since the above powder has the characteristics of high-temperature resistance and strong oxidation resistance, the prepared ceramic material also has the characteristics of high density, ablation resistance, and strong oxidation resistance. The ceramic material includes ceramic bulk and ceramic coating, and the product form can be selected according to actual needs. The present application does not limit the preparation method of the ceramic material, as long as the above requirements are met.

[0084] Further, in an embodiment, the ceramic material provided in the present application is prepared from any of the non-stoichiometric high-entropy boride carbide powders provided in the first aspect of the present application. The present application does not limit the specific preparation method, and in an embodiment, the ceramic material can be prepared by using the following method:

[0085] Preparation method of ceramic bulk material: XC y B z The ceramic powder is used as raw material, and pressure sintering is performed using a spark plasma sintering furnace. The sintering process parameters are as follows: vacuum condition (<5Pa), heating to 1900℃ at a rate of 100℃ / min, and holding pressure at 50-60MPa for 10-30min. The sintered bulk ceramic has a relative density of >95%.

[0086] Preparation method of ceramic coating: XC y B zThe ceramic powder is used as raw material, and the powder is sprayed on a C / C composite material or a graphite substrate by using an atmospheric plasma spraying device to form a ceramic coating on the surface of the substrate. The spraying gas is N2, the powder feeding gas is Ar, the spraying voltage is 50-60 V, the current is 500-600 A, the spraying distance is 100 mm, and the spraying angle is 90°.

[0087] The ceramic material provided by the application has the characteristics of compactness, high ablation resistance and strong oxidation resistance.

[0088] The non-stoichiometric high-entropy boride carbide powder, the preparation method and the application thereof provided by the application will be further described in detail below in combination with specific examples.

[0089] Example 1

[0090] 1) ZrCl4, HfCl4, TiCl4 and TaCl4 are weighed in sequence respectively. 5， The molar ratio of Zr, Hf, Ti and Ta is 0.3:0.3:0.3:0.1. The above-mentioned substances are dissolved in deionized water, NH3·H2O solution is added to the obtained mixed system, the pH of the solution is 7-8, and a precipitate is generated by reaction. After the precipitate is completely generated, the solid phase material is filtered, washed with distilled water and ethanol, and then dried at 40℃ to obtain the precipitate, which is the precipitate containing X elements.

[0091] 2) Phenolic resin (first carbon source) is added to the precipitate containing X elements, the molar ratio of carbon atoms in the added phenolic resin to the total amount of X element metal atoms is 1.7:1, and the mixed system obtained after drying is carbonized at 1600℃ for 30 min to obtain carbide powder.

[0092] 3) 1.5wt% of phenolic resin (second carbon source) is added to the obtained carbide powder, mixed in ethanol, and then dried to obtain a mixture. Subsequently, boric acid is added to the mixture and mixed in water, the molar ratio of boron atoms in the added boric acid to the total amount of X element metal atoms is 0.16:1, the ratio p of the mass of boric acid to the mass of carbide powder is 0.08, and the molar ratio of carbon elements in the second carbon source to boron elements in boric acid is 0.75:1. The mixed and dried mixture is a second carbon source-boric acid-carbide powder composite.

[0093] 4) The second carbon source-boric acid-carbide powder composite is subjected to high-temperature boronization under pressureless discharge plasma sintering treatment conditions, the vacuum degree in the furnace is less than 5 Pa, the temperature is raised to 1700℃ at a heating rate of 50℃ / min, and then the temperature is maintained for 30 min. Subsequently, the temperature is cooled to room temperature to obtain non-stoichiometric high-entropy boride carbide powder A1.

[0094] Figure 1 is an X-ray diffraction spectrum of the high-entropy boride- containing carbide powder A1 prepared in Example 1, showing that the prepared high-entropy boride-containing carbide powder A1 has a single phase and no second phase is generated. Figure 2 is a micro-morphology diagram of the high-entropy boride- containing carbide powder A1 prepared in Example 1. As shown in Figure 2, the non-stoichiometric high-entropy boride-containing carbide powder has a particle size of <1 μm. The atomic ratio of Zr, Hf, Ti and Ta is 0.3:0.3:0.3:0.1, and the atomic ratio of C and B is 0.7:0.15, according to the ICP-OES element content analysis. The molecular formula of the high-entropy boride-containing carbide powder A1 is (Zr 0.3 Hf 0.3 Ti 0.3 Ta 0.1 )(C 0.70 B 0.15 ), and the oxygen content thereof is 0.05 wt% according to the nitrogen-hydrogen-oxygen analyzer test.

[0095] Figure 5 is a macro-morphology diagram of the high-entropy boride- containing carbide ceramic bulk prepared by sintering the powder A1 as the raw material.

[0096] Example 2

[0097] 1) ZrCl4, HfCl4, TiCl4, TaCl5 and NbCl5 are weighed in sequence, respectively, wherein the molar ratio of Zr element, Hf element, Ti element, Ta element and Nb element is 0.2:0.2:0.2:0.2:0.2. The above substances are dissolved in deionized water, and NaOH solution is added to the obtained mixed system to make the pH of the solution be 7-8, and a precipitate is generated by reaction. After the precipitate is completely generated, the solid phase substance is filtered, washed by distilled water and ethanol, and dried at 40°C to obtain the precipitate, which is the precipitate containing X element.

[0098] 2) Phenolic resin (first carbon source) is added to the precipitate containing X element, and the molar ratio of carbon atoms of the added phenolic resin to the total amount of X element metal atoms is 1.9:1. The mixed system obtained after drying is carbonized at 1900°C for 20 min to obtain carbide powder.

[0099] 3) 0.5 wt% phenolic resin (second carbon source) is added to the obtained carbide powder, mixed in ethanol, and the mixture is dried after being uniformly mixed. Subsequently, boric acid is added to the mixture and mixed in water, and the molar ratio of boron atoms of the added boric acid to the total amount of X element metal atoms is 0.05:1. The ratio p of the mass of boric acid to the mass of carbide powder is 0.08, and the molar ratio of carbon element in the second carbon source to boron element in boric acid is 0.8:1. The mixed system obtained after drying is the second carbon source-boric acid-carbide powder composite.

[0100] 4) The second carbon source-boric acid-carbide powder complex is subjected to high-temperature boronization under pressureless discharge plasma sintering treatment conditions, with a furnace vacuum of less than 5 Pa, and a heating rate of 150 °C / min to 1300 °C, and holding for 60 min, and then cooling to room temperature, to obtain a non-stoichiometric high-entropy boride-carbide powder A2.

[0101] Figure 3 is an X-ray diffraction spectrum of the high-entropy boride-carbide powder A2 prepared in Example 2, showing that the prepared high-entropy boride-carbide powder A2 has a single phase and no second phase is generated. According to ICP-OES elemental content analysis, in the powder A2, 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 and B is 0.90:0.05, and the non-stoichiometric high-entropy boride-carbide molecular formula is (Zr 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )(C 0.90 B 0.05 ), the powder particle size is about 500 nm (i.e. about 500 nm), and the oxygen content is 0.20 wt% as tested by a nitrogen-hydrogen-oxygen analyzer.

[0102] Example 3

[0103] 1) Zr(NO3)4, Hf(NO3)4, Ti(NO3)4, and Ta(NO3)5 are weighed in sequence, respectively, and the molar ratio of Zr, Hf, Ti, and Ta is 0.25:0.25:0.25:0.25. The above substances are dissolved in deionized water, and KOH solution is added to the obtained mixed system to make the solution pH 7-8, and a precipitate is generated by reaction. After the precipitate is completely generated, the solid phase material is filtered, washed with distilled water and ethanol, and dried at 40 °C to obtain a precipitate, which is a precipitate containing X elements.

[0104] 2) Phenolic resin (first carbon source) is added to the precipitate containing X elements, and the molar ratio of carbon atoms in the added phenolic resin to the total amount of X element metal atoms is 1.8:1. The mixed system obtained after drying is subjected to carbonization treatment at 1600 °C for 40 min to obtain a carbide powder.

[0105] 3) To the carbide powder obtained above, 1wt% of phenolic resin (second carbon source) was added and mixed in ethanol. After the mixture was mixed uniformly, it was dried to obtain a mixture. Subsequently, boric acid was added to the mixture and mixed in water. The molar ratio of boron atoms in the boric acid to the total amount of metal atoms of the X elements was 0.11:1. The mass ratio p of the boric acid to the mass of the carbide powder was 0.04. The molar ratio of carbon atoms in the second carbon source to boron atoms in the boric acid was 0.9:1. The mixture obtained after drying was the second carbon source-boric acid-carbide powder composite.

[0106] 4) The second carbon source-boric acid-carbide powder composite obtained above was subjected to high-temperature boronization under pressureless discharge plasma sintering treatment conditions. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1800°C at a rate of 100°C / min and held for 30 min. Subsequently, the temperature was cooled to room temperature to obtain a non-stoichiometric high-entropy boride carbide powder A3.

[0107] According to the ICP-OES element content analysis, in the powder A3, the atomic ratio of Zr, Hf, Ti and Ta was 0.25:0.25:0.25:0.25, and the atomic ratio of C and B was 0.80:0.10. The non-stoichiometric high-entropy boride carbide molecular formula was (Zr 0.25 Hf 0.25 Ti 0.25 Ta 0.25 )(C 0.80 B 0.10 ). The powder particle size was about 800 nm. The oxygen content was 0.11wt% as tested by a nitrogen-hydrogen-oxygen analyzer.

[0108] Example 4

[0109] 1) Zr(NO3)4, Hf(NO3)4, Ti(NO3)4 and Ta(NO3)5 were weighed in sequence, respectively. The molar ratio of Zr, Hf, Ti and Ta was 0.4:0.4:0.1:0.1. The above substances were dissolved in deionized water. NH3·H2O solution was added to the obtained mixed system to make the pH of the solution 7-8. The reaction generated a precipitate. After the precipitate was completely generated, the solid phase material was filtered, washed with distilled water and ethanol, and dried at 40°C to obtain a precipitate, which was the precipitate containing X elements.

[0110] 2) Phenolic resin (first carbon source) was added to the precipitate containing X elements. The molar ratio of carbon atoms in the phenolic resin to the total amount of metal atoms of the X elements was 1.65:1. The mixed system obtained after drying was subjected to carbonization treatment at 1600°C for 30 min to obtain a carbide powder.

[0111] 3) To the carbide powder obtained above, 2.5wt% phenolic resin (second carbon source) was added and mixed in ethanol. After mixing evenly, the mixture was dried to obtain a mixture. Then boric acid was added to the mixture and mixed in water. The molar ratio of boron atoms in the boric acid to the total amount of metal atoms of element X was 0.22:1. The mass ratio p of the mass of the boric acid to the mass of the carbide powder was 0.05. The molar ratio of carbon atoms in the second carbon source to boron atoms in the boric acid was 1:1. The mixture was dried to obtain a second carbon source-boric acid-carbide powder composite.

[0112] 4) The second carbon source-boric acid-carbide powder composite obtained above was subjected to high-temperature boronization under pressureless discharge plasma sintering treatment conditions. The vacuum degree in the furnace was less than 5 Pa. The temperature was raised to 1800°C at a rate of 100°C / min, and the temperature was maintained for 30 min. Then the temperature was cooled to room temperature to obtain a non-stoichiometric high-entropy boride carbide powder A4.

[0113] ICP-OES element content analysis showed that in the powder A4, the atomic ratio of Zr, Hf, Ti and Ta was 0.4:0.4:0.1:0.1, and the atomic ratio of C and B was 0.65:0.20. The molecular formula of the high-entropy ultrahigh-temperature ceramic material was (Zr 0.4 Hf 0.4 Ti 0.1 Ta 0.1 )(C 0.65 B 0.20 ), the powder particle size was about 500 nm, and the oxygen content was 0.16wt% as tested by a nitrogen-hydrogen-oxygen analyzer.

[0114] Example 5

[0115] This example is basically the same as Example 1, except that TaCl5 is replaced by WCl5, and the amount of substance of the metal elements in the two is kept equal, to obtain a non-stoichiometric high-entropy boride carbide powder A5.

[0116] ICP-OES element content analysis showed that in the powder A5, the atomic ratio of Zr, Hf, Ti and W was 0.3:0.3:0.3:0.1, and the atomic ratio of C and B was 0.7:0.15. The molecular formula of the non-stoichiometric high-entropy boride carbide was (Zr 0.3 Hf 0.3 Ti 0.3 W 0.1 )(C 0.70 B 0.15 ), the powder particle size was about 900 nm, and the oxygen content was 0.14wt% as tested by a nitrogen-hydrogen-oxygen analyzer.

[0117] Example 6

[0118] The embodiment is basically the same as embodiment 1, the difference is that TaCl5 is replaced by VCl3, and the amount of substance of metal elements in both is kept equal, to obtain non-stoichiometric ratio high-entropy boride carbide powder A6.

[0119] ICP-OES element content analysis shows that in powder A6, the atomic ratio of Zr, Hf, Ti and V is 0.3:0.3:0.3:0.1, and the atomic ratio of C and B is 0.7:0.15, and the non-stoichiometric ratio high-entropy boride carbide molecular formula is (Zr 0.3 Hf 0.3 Ti 0.3 V 0.1 )(C 0.70 B 0.15 ), the powder particle size is about 900 nm, and the oxygen content is 0.15wt% tested by nitrogen hydrogen oxygen analyzer.

[0120] Example 7

[0121] The embodiment is basically the same as embodiment 2, the difference is that,

[0122] The molar ratio of carbon atoms of the added phenolic resin (first carbon source) to the total amount of substance of X element metal atoms is 1.65:1.

[0123] The molar ratio of boron atoms of the added boric acid to the total amount of substance of X element metal atoms is 0.3:1, and the mass ratio of boric acid to carbide powder is 0.15.

[0124] Non-stoichiometric ratio high-entropy boride carbide powder A7 is obtained.

[0125] ICP-OES element content analysis shows that in powder A7, 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 and B is 0.65:0.3, and the non-stoichiometric ratio high-entropy boride carbide molecular formula is (Zr 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )(C 0.65 B 0.30 ), the powder particle size is about 500 nm (i.e. about 500 nm), and the oxygen content is 0.20wt% tested by nitrogen hydrogen oxygen analyzer.

[0126] Example 8

[0127] The embodiment is basically the same as embodiment 1, the difference is that,

[0128] The molar ratio of carbon atoms of the added phenolic resin (first carbon source) to the total amount of substance of X element metal atoms is 1.65:1.

[0129] The molar ratio of boron atoms of the added boric acid to the total amount of substance of X element metal atoms is 0.3:1, and the mass ratio of the boric acid to the mass of the carbide powder is 0.15, to obtain a non-stoichiometric ratio high-entropy boron-containing carbide powder A8.

[0130] According to ICP-OES element content analysis, in the powder A8, the atomic ratio of Zr, Hf, Ti and Ta is 0.3:0.3:0.3:0.1, and the atomic ratio of C and B is 0.65:0.3, and the molecular formula of the non-stoichiometric ratio high-entropy boron-containing carbide is (Zr 0.3 Hf 0.3 Ti 0.3 Ta 0.1 )(C 0.65 B 0.30 ), and the oxygen content thereof is 0.18wt% tested by a nitrogen-hydrogen-oxygen analyzer.

[0131] Comparative Example 1

[0132] This comparative example is basically the same as Example 4, except that in step 3), 2wt% phenolic resin (second carbon source) and boric acid are simultaneously added to the high-entropy carbide powder, mixed in ethanol, and after uniform mixing, the mixture is dried to obtain a mixture.

[0133] The molar ratio of boron atoms of the added boric acid to the total amount of substance of X element metal atoms is 0.22:1, and the mixture obtained by drying is a second carbon source-boric acid-carbide powder composite.

[0134] The powder B1 is prepared.

[0135] FIG. 4 is an X-ray diffraction spectrum of the powder B1 prepared in Comparative Example 1. As shown in FIG. 3, the diffraction peaks of Zr-Ti-Hf-Ta-C-B solid solution phase, TiB2, HfB2 and m-HfO2 appear in the powder B1, indicating that the powder is a mixture of the four substances, and the Zr-Hf-Ti-Ta-C-B solid solution shows a ZrC characteristic peak, indicating that the second carbon source and the boron source are simultaneously mixed with the high-entropy carbide powder in step 3), and a single-phase high-entropy boron-containing carbide solid solution powder cannot be formed.

[0136] Comparative Example 2

[0137] This comparative example is basically the same as Example 1, except that in step 2), the molar ratio of carbon atoms of the added phenolic resin to the total amount of substance of X element metal atoms is 2:1, and after the synthesis of the carbide powder, steps 3) and 4) are not performed, to prepare the powder B2. According to tests, the atomic ratio of Zr, Hf, Ti, Ta and C in the powder B2 is 0.3:0.3:0.3:0.1:0.98, and the molecular formula is (Zr 0.3 Hf0.3 Ti 0.3 Ta 0.1 )C 0.98 .

[0138] Test Example

[0139] The products prepared in Example 1 and Comparative Example 2 were subjected to oxidation resistance testing, and the results are shown in Table 1. The products prepared in Example 1 and Comparative Example 1 were subjected to oxidation resistance testing using TG-DSC in an air atmosphere, at a temperature increase rate of 10 min / °C, with a product particle size of 0.5-1 μm, and in an air atmosphere, and the initial oxidation temperature was read from the DSC temperature increase curve. The higher the initial oxidation temperature, the better the oxidation resistance of the product.

[0140] Table 1 Initial Oxidation Temperature Data

[0141] As can be seen from the data in Table 1, the oxidation resistance of the non-stoichiometric high-entropy borocarbide powders obtained in each of the examples is better than the oxidation resistance of the high-entropy carbides obtained in each of the comparative examples.

[0142] Finally, it should be noted that the above examples are merely used to illustrate the technical solutions of the present application, and are not intended to limit the same; even though the present application has been described in detail with reference to the above examples, those of ordinary skill in the art will understand that they can still modify the technical solutions described in the above examples, or make equivalent replacements for some or all of the technical features therein; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the examples of the present application.

Claims

1. A non-stoichiometric high-entropy boride-containing carbide powder, wherein, The powder comprises a substance of formula XC y B z ​ wherein the X element is selected from at least four of Zr, Hf, Ti, Ta, Nb, V and W, 0.6≤y<1.0, 0 The powder has a single-phase face-centered cubic structure, a particle size of ≤1 μm, and an oxygen content of not higher than 0.2 wt%.

2. The powder of claim 1, wherein, The X element is selected from four or five of Zr, Hf, Ti, Ta, Nb, V and W.

3. The powder according to claim 1 or 2, wherein The X element is composed of Zr, Hf, Ti and Ta; or, The X element is composed of Zr, Hf, Ti, Ta and Nb.

4. The powder according to any one of claims 1 to 3, wherein 0.65≤y≤0.95, y+z≤0.

95.

5. The powder according to any one of claims 1 to 4, wherein 0.20＜z＜0.40。 6. A method of producing the powder of any one of claims 1 to 5, wherein, The method comprises the following steps: 1) mixing a salt solution comprising an X element with an alkaline substance to obtain a mixture with a pH value of 7-8, thereby obtaining a precipitate comprising the X element; 2) mixing the precipitate comprising the X element with a first carbon source to perform carbonization treatment, thereby obtaining a carbide powder; 3) mixing the carbide powder with a second carbon source in an organic solvent to obtain a second carbon source-carbide powder composite; mixing the second carbon source-carbide powder composite with boric acid to obtain a second carbon source-boric acid-carbide powder composite; 4) performing sintering treatment on the second carbon source-boric acid-carbide powder composite to obtain a non-stoichiometric high-entropy boride carbide powder. The first carbon source is any one of phenolic resin and epoxy resin. The second carbon source is any one of phenolic resin and epoxy resin. The molar ratio of boron in the boric acid to the X element is less than 0.

4. The mass ratio p of the boric acid to the carbide powder satisfies 0 The molar ratio of carbon atoms in the first carbon source to metal atoms of the X element is (1+y):

1.

7. The method of claim 6, wherein, The mass of the second carbon source is 0-2.5 wt% of the mass of the carbide powder.

8. The method of claim 6 or 7, wherein, The molar ratio of carbon in the second carbon source to boron in the boric acid is 0.75:1-1:

1.

9. The method of any one of claims 6-8, wherein, The salt solution comprising the X element comprises a nitrate of the X element and / or a chloride of the X element. The nitrate of the X element is at least one of Zr(NO3)4, Hf(NO3)4, Ti(NO3)4, Ta(NO3)5 and Nb(NO3)5. The chloride of the X element is at least one of ZrCl4, HfCl4, TiCl4, TaCl5 and NbCl5.

10. The method of any one of claims 6-9, wherein, The alkaline substance comprises at least one of NaOH, KOH and ammonia.

11. The method of any one of claims 6-10, wherein, The carbonization treatment has a treatment temperature of 1600-1900°C, a holding time of 20-40 min, a vacuum degree of ≤5 Pa and a heating rate of 20-50°C / min.

12. The method of any one of claims 6-11, wherein, The sintering treatment is pressureless discharge plasma sintering treatment, has a treatment temperature of 1300-1800°C, a holding time of 15-60 min, a heating rate of 50-150°C / min and a vacuum degree of ≤10 Pa.

13. A ceramic material, wherein, The ceramic material comprises the non-stoichiometric high-entropy borocarbide powder of any one of claims 1-5; and / or, the material is prepared from the non-stoichiometric high-entropy borocarbide powder of any one of claims 1-5.

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