Non-stoichiometric high-entropy boron-containing carbide powder as well as preparation method and application thereof

Abstract

The invention provides non-stoichiometric high-entropy boron-containing carbide powder as well as a preparation method and application thereof, and the powder comprises a substance with a molecular formula of XCyBz, wherein the X element is selected from at least four of Zr, Hf, Ti, Ta, Nb, V and W elements, y is larger than or equal to 0.6 and smaller than 1.0, z is larger than 0 and smaller than 0.4, and y + z is smaller than or equal to 0.96; the powder has a single phase face-centered cubic structure, the particle size is less than or equal to 1 mu m, and the oxygen content is less than or equal to 0.2 wt%. The powder provided by the invention has the characteristics of high temperature resistance and high oxidation resistance, and can be used for preparing high-density, oxidation-resistant and ablation-resistant ceramic blocks or coatings.

Description

Technical Field

[0001] This invention relates to a non-stoichiometric high-entropy boron-containing carbide powder, and more particularly to a non-stoichiometric high-entropy boron-containing carbide powder, its preparation method, and its application, belonging to the field of ceramic materials technology. Background Technology

[0002] In the oil and petrochemical industries, downhole drill bits and high-temperature corrosive components face extreme temperatures and highly corrosive media. Carbide ceramics, with their high melting point, high stability, and high-temperature strength, can extend the service life of critical equipment by forming protective coatings. Furthermore, the high melting point of carbide ceramics makes them an important candidate material for thermal protection systems in extreme environments in aerospace. However, traditional binary carbide ceramics have poor oxidation resistance, limiting their potential applications. For example, ZrC oxidizes below 1200℃ into a loose, porous zirconium oxide layer, resulting in poor oxygen barrier properties.

[0003] Boron-containing carbides are a new type of carbide formed by the solid dissolution of boron atoms into the carbide, occupying carbon vacancies and creating a stable face-centered cubic structure. They combine the ultra-high melting point and temperature resistance of carbides with the oxidation resistance of boron compounds, effectively solving the problem of poor oxidation resistance in carbides and showing significant potential applications in high-temperature thermal protection. Currently, reports on boron-containing carbides include 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.) A C / C-(Zr) method is reported. 0.8 Ti 0.2 (C) 0.74 B 0.26 Composite materials, in which the ceramic phase (Zr) is present. 0.8 Ti 0.2 (C) 0.74 B 0.26 This 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.

[0004] 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.

[0005] 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

[0006] This invention provides a non-stoichiometric high-entropy boron-containing carbide powder, which has the characteristics of high temperature resistance, strong oxidation resistance, and can be used to prepare high-density, ablation-resistant, and oxidation-resistant ceramic blocks or coatings.

[0007] This invention also provides a method for preparing non-stoichiometric high-entropy boron-containing carbide powder, which can be obtained by the above-mentioned non-stoichiometric high-entropy boron-containing carbide powder. This method has the advantages of short preparation cycle and simple process.

[0008] The present invention also provides a ceramic material, which has the characteristics of high density, ablation resistance and strong oxidation resistance.

[0009] This invention provides a non-stoichiometric high-entropy boron-containing carbide powder, wherein the powder comprises a compound with the molecular formula XC. y B z Substances;

[0010] Among them, the element X is selected from at least four of the elements Zr, Hf, Ti, Ta, Nb, V, and W, and 0.6≤y<1.0, 0<z<0.4, and y+z≤0.96;

[0011] The powder has a single-phase face-centered cubic structure, a particle size ≤1μm, and an oxygen content not higher than 0.2wt%.

[0012] In the powder described above, the X element is selected from four or five of the elements Zr, Hf, Ti, Ta, Nb, V, and W.

[0013] The powder described above, wherein the X element is composed of Zr, Hf, Ti, and Ta elements; or,

[0014] The X element is composed of Zr, Hf, Ti, Ta and Nb elements.

[0015] The powder as described above, wherein 0.65≤y≤0.95, y+z≤0.95.

[0016] The powder as described above, wherein 0.20 < z < 0.40.

[0017] This invention also provides a method for preparing high-entropy boron-containing carbide powder, which can produce any of the aforementioned high-entropy boron-containing carbide powders. The method includes the following steps:

[0018] 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.

[0019] 2) The precipitate containing element X is mixed with a first carbon source and subjected to carbonization treatment to obtain carbide powder;

[0020] 3) The carbide powder is mixed with the second carbon source in an organic solvent to obtain a second carbon source-carbide powder composite; the second carbon source-carbide powder composite is mixed with boric acid to obtain a second carbon source-boric acid-carbide powder composite.

[0021] 4) The second carbon source-boric acid-carbide powder composite is sintered to obtain non-stoichiometric high-entropy boron-containing carbide powder.

[0022] The first carbon source is either phenolic resin or epoxy resin;

[0023] The second carbon source is either phenolic resin or epoxy resin;

[0024] The molar ratio of boron to X in the boric acid is less than 0.4;

[0025] The ratio p of the mass of boric acid to the mass of the carbide powder satisfies: 0 < p ≤ 0.2;

[0026] The molar ratio of carbon atoms in the first carbon source to metal atoms of element X is (1+y):1.

[0027] In the preparation method described above, the mass of the second carbon source is 0-2.5 wt% of the mass of the carbide powder.

[0028] In the preparation method described above, the molar ratio of carbon in the second carbon source to boron in boric acid is 0.75:1 to 1:1.

[0029] The preparation method described above, wherein the salt solution containing element X includes nitrate of element X and / or chloride of element X;

[0030] The nitrate of element X is selected from at least one of Zr(NO3)4, Hf(NO3)4, Ti(NO3)4, Ta(NO3)5 and Nb(NO3)5;

[0031] The chloride salt of element X is selected from at least one of ZrCl4, HfCl4, TiCl4, TaCl5 and NbCl5.

[0032] In the preparation method described above, the alkaline substance includes at least one of NaOH, KOH, and ammonia water.

[0033] In the preparation method described above, the carbonization treatment temperature is 1600-1900℃, the holding time is 20-40min, the vacuum degree is ≤5Pa, and the heating rate is 20-50℃ / min.

[0034] In the preparation method described above, the sintering treatment is a pressureless discharge plasma sintering treatment, with a treatment temperature of 1300-1800℃, a holding time of 15-60min, a heating rate of 50-150℃ / min, and a vacuum degree ≤10Pa.

[0035] The present invention also provides a ceramic material, wherein the ceramic material comprises any of the above-mentioned non-stoichiometric high-entropy boron-containing carbide powders; and / or, the ceramic material is prepared from any of the above-mentioned non-stoichiometric high-entropy boron-containing carbide powders.

[0036] The non-stoichiometric high-entropy boron-containing carbide powder provided by this invention has the characteristics of high temperature resistance, strong oxidation resistance, and can be used to prepare high-density, ablation-resistant, and oxidation-resistant ceramic blocks or coatings. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced one by one below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 X-ray diffraction pattern of high-entropy boron-containing carbide powder A1 prepared in Example 1;

[0039] Figure 2 The surface morphology of high-entropy boron-containing carbide powder A1;

[0040] Figure 3 X-ray diffraction pattern of high-entropy boron-containing carbide powder A2 prepared in Example 2;

[0041] Figure 4 The X-ray diffraction pattern of powder B1 is shown.

[0042] Figure 5 This is a macroscopic morphology image of a high-entropy boron-containing carbide ceramic block prepared by sintering powder Al. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The first aspect of this invention provides a non-stoichiometric high-entropy boron-containing carbide powder, the powder comprising a compound with the molecular formula XC y B z Substances;

[0045] Among them, the element X is selected from at least four of the elements Zr, Hf, Ti, Ta, Nb, V, and W, and 0.6≤y<1.0, 0<z<0.4, and y+z≤0.96;

[0046] The powder has a single-phase face-centered cubic structure, a particle size ≤1μm, and an oxygen content <0.2wt%.

[0047] The powder provided by this invention is a boron-containing carbide. Non-stoichiometry refers to the fact that the atomic (or ionic) composition of the elements constituting the powder can fluctuate within a certain proportional range. The aforementioned composition does not conform to the rules of valence, does not obey the law of composition, and cannot be expressed using small integers; it can only be described using decimals.

[0048] The powder contains particles with the molecular formula XC. y B z The substance, that is, the powder, can be made from a substance with the molecular formula XC. y B z The composition of matter can include multiple substances, but each substance must satisfy the molecular formula XC. y B z .

[0049] Specifically, in this molecular formula, element X is selected from at least four of the elements Zr, Hf, Ti, Ta, Nb, V, and W. In the powder provided by this invention, element X can be selected from four, five, six, or seven of the aforementioned elements. Furthermore, in the powder provided by this invention, 0.6 ≤ y < 1.0, 0 < z < 0.4, and y + z ≤ 0.96. Simultaneously, the powder has a single-phase face-centered cubic structure with a particle size not exceeding 1 μm.

[0050] The non-stoichiometric high-entropy boron-containing carbide powder provided by this invention is non-stoichiometric, has a low particle size, contains a certain number of carbon vacancies in the crystal lattice, has high structural stability of the compound, and the oxide layer generated by oxidation is dense, which reduces the internal diffusion rate of oxygen. It has the characteristics of high temperature resistance, strong oxidation resistance, and can be used to prepare high-density, ablation-resistant, and oxidation-resistant ceramic blocks or coatings.

[0051] Furthermore, in the non-stoichiometric high-entropy boron-containing carbide powder provided by the present invention, element X is selected from four or five elements chosen from Zr, Hf, Ti, Ta, Nb, V, and W; furthermore, in the non-stoichiometric high-entropy boron-containing carbide powder provided by the present invention, element X is composed of Zr, Hf, Ti, and Ta; or, element X is composed of Zr, Hf, Ti, Ta, and Nb. Powders possessing the above properties exhibit even more prominent characteristics of high-temperature resistance and oxidation resistance.

[0052] Furthermore, in the non-stoichiometric high-entropy boron-containing carbide powder provided by this invention, 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 aforementioned properties exhibits more prominent characteristics of high-temperature resistance and oxidation resistance.

[0053] Furthermore, in the non-stoichiometric high-entropy boron-containing carbide powder provided by this invention, 0.20 < z < 0.40. Powders with higher boron content exhibit more outstanding high-temperature resistance and oxidation resistance.

[0054] In one embodiment, the non-stoichiometric high-entropy boron-containing carbide powder provided by the present invention is composed of any substance having the following molecular formula:

[0055] (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.

[0056] A second aspect of this invention 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:

[0057] 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.

[0058] 2) The precipitate containing element X is mixed with the first carbon source and subjected to carbonization treatment to obtain carbide powder;

[0059] 3) The carbide powder and the second carbon source are mixed in an organic solvent to obtain a second carbon source-carbide powder composite; the second carbon source-carbide powder composite is mixed with boric acid to obtain a second carbon source-boric acid-carbide powder composite.

[0060] 4) The second carbon source-boric acid-carbide powder composite was sintered to obtain non-stoichiometric high-entropy boron-containing carbide powder.

[0061] 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.

[0062] The molar ratio of boron to element X in boric acid is less than 0.4;

[0063] The ratio p of the mass of boric acid to the mass of carbide powder satisfies: 0 < p ≤ 0.2.

[0064] The molar ratio of carbon atoms in the first carbon source to metal atoms of element X is (1+y):1.

[0065] In the above description, element X is the same as before, that is, element X is selected from at least four of the elements Zr, Hf, Ti, Ta, Nb, V, and W. In other words, element X is a mixture of at least four elements. Therefore, the salt solution containing element X in step 1) is an aqueous solution containing salts of at least four of the above elements. The precipitate containing element X obtained includes oxides, hydroxides, or both of the above four elements. Since the oxides or hydroxides of the above elements are insoluble in water, the precipitate containing element X in step 1) can be separated from the liquid phase.

[0066] An alkaline substance is one that exhibits alkalinity in an aqueous solution. This invention does not limit the specific selection of the alkaline substance, as long as it meets the requirement of exhibiting alkalinity in the aqueous solution. In one embodiment, the alkaline substance is selected from at least one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia solution.

[0067] In the method provided by this invention, the pH value of the mixture system, which includes an aqueous solution containing element X, is controlled at 7-8 when mixed with an alkaline substance. This pH value allows for the preparation of a precipitate containing element X.

[0068] The function of the first carbon source is to provide a carbon source for the carbonization process. In the method provided by this invention, the first carbon source is any one of phenolic resin and epoxy resin. The function of the carbonization process is to react the first carbon source with the hydroxide of element X at high temperature to generate carbide powder with carbon vacancies. This invention does not impose specific limitations on the conditions of the carbonization process, and commonly used processing conditions in the art can be used. In one embodiment, the processing temperature of the carbonization process is not lower than 1600°C, and the holding time is not lower than 20 minutes.

[0069] The second carbon source has two functions: firstly, it can coat the carbide powder, preventing the carbide from reacting with boric acid at high temperatures to form borate; secondly, it reduces the boron element in the boric acid and diffuses it into the carbide lattice, and reacts with excess oxygen to form CO / CO2 gas. This prevents the formation of a second-phase oxide impurity in the boron-containing carbide, thus producing high-entropy boron-containing carbide powder with strong high-temperature resistance and oxidation resistance. In the method provided by this invention, the second carbon source is either phenolic resin or epoxy resin.

[0070] Organic solvents are used to dissolve boric acid. The method provided by this invention does not specifically limit the type of organic solvent used in step 3). In one embodiment, the organic solvent is ethanol.

[0071] It is worth noting that, regarding step 3), the mixing of the second carbon source-carbide powder complex with boric acid, the present invention does not limit the specific mixing method of the above process. In one embodiment, the second carbon source-carbide powder complex can be mixed with solid boric acid and then dissolved in water; in another embodiment, the second carbon source-carbide powder complex can be added to a prepared aqueous boric acid solution.

[0072] Sintering can further boronize the second carbon source-boric acid-carbide powder composite at high temperatures. Specifically, the second carbon source reacts with boric acid, reducing the boron in the boric acid to generate boron atoms. Because the coated carbide is non-stoichiometric, its lattice contains carbon vacancies. Boron atoms diffuse into the carbide at high temperatures, occupying some of the carbon vacancies, ultimately generating non-stoichiometric boron-containing carbides.

[0073] This invention does not limit the specific processing conditions for sintering; commonly used processing conditions in the art can be used. In one embodiment, the sintering process is pressureless discharge plasma sintering, with a processing temperature of not less than 1300°C and a holding time of not less than 15 minutes.

[0074] Furthermore, in the method provided in this invention, the molar ratio of boron to element X in boric acid is less than 0.4, the ratio p of the mass of boric acid to the mass of carbide powder satisfies: 0 < p ≤ 0.2, and the molar ratio of carbon atoms in the first carbon source to metal atoms of element X is (1+y):1. With appropriate amounts of raw materials, the non-stoichiometric high-entropy boron-containing carbide powder provided in this invention can be obtained.

[0075] The present invention provides a method for preparing non-stoichiometric high-entropy boron-containing carbide powder. First, four or more transition metal cation hydroxides with similar particle sizes are synthesized using a co-precipitation method. These are then carbonized at high temperature to prepare non-stoichiometric high-entropy carbide ultrafine powder. Based on this, boric acid is added as a boron source, allowing boron atoms to fill designed carbon vacancies without altering the crystal structure of the carbide. Simultaneously, phenolic resin is selected as a carbon source, coating the surface of the carbide powder at the interface between the carbide and the boric acid precipitate. This eliminates excess oxygen introduced by the boric acid while altering the reaction sequence of the high-temperature boration, preventing the formation of boron impurities during the high-temperature reaction. Ultimately, a single-phase high-entropy boron-containing carbide powder is formed, featuring a short preparation cycle and a simple process.

[0076] Furthermore, in the method provided in this invention, the amount of the second carbon source added is 0-2.5 wt% (excluding 0 wt%) of the carbide powder. When the amount of the second carbon source added is too large, after eliminating excess oxygen, the addition of too much carbon will occupy the anionic lattice in the carbide, resulting in fewer vacancy lattices that boron atoms can occupy when dissolved in the carbide, making it difficult to form non-stoichiometric boron-containing carbides; however, when the amount of carbon source is too small, the powder obtained contains a certain amount of oxide impurities, making it difficult to form a single-phase boron-containing carbide.

[0077] Furthermore, in one embodiment, the molar ratio of carbon in the second carbon source to boron in boric acid is 0.75:1 to 1:1. A suitable molar ratio of boron to carbon in the second carbon source results in powders with enhanced high-temperature resistance and oxidation resistance.

[0078] In one embodiment, the salt solution containing element X includes a nitrate of element X and / or a chloride of element X, wherein the nitrate of element X 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 of element X 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 element X into the powder synthesis system, making the powder preparation method provided by this invention more efficient. This invention does not limit the concentration of the above-mentioned element X salts in the salt solution containing element X, as long as the requirement of obtaining powder is met. Further, in one embodiment, the alkaline substance includes at least one of NaOH, KOH, and ammonia water.

[0079] In one embodiment, the carbonization treatment temperature is 1600-1900℃, the holding time is 20-40 min, the vacuum degree is ≤5 Pa, and the heating rate is 20-50℃ / min. Suitable carbonization conditions can increase the reaction rate between the first carbon source and the hydroxide of element X, generating carbide powder with carbon vacancies. This further improves the efficiency of the powder preparation method provided by this invention.

[0080] Furthermore, in one embodiment, the sintering treatment is pressureless discharge plasma sintering, with a treatment temperature of 1300-1800℃, a holding time of 15-60 min, a heating rate of 50-150℃ / min, and a vacuum degree ≤10 Pa. These conditions further highlight the high-temperature resistance and strong oxidation resistance of the obtained non-stoichiometric high-entropy boron carbide powder.

[0081] A third aspect of the present invention provides a ceramic material comprising any of the above-mentioned non-stoichiometric high-entropy boron-containing carbide powders; and / or, the ceramic material is prepared from any of the above-mentioned non-stoichiometric high-entropy boron-containing carbide powders.

[0082] In one embodiment, the ceramic material comprises any of the non-stoichiometric high-entropy boron-containing carbide powders provided in the first aspect of this invention. Because the aforementioned powders possess characteristics of high temperature resistance and strong oxidation resistance, the resulting ceramic material also exhibits high density, ablation resistance, and strong oxidation resistance. The ceramic material includes a ceramic block and a ceramic coating, and the product form can be selected according to actual needs. This invention does not limit the preparation method of the ceramic material; as long as the above requirements are met, it is acceptable.

[0083] Furthermore, in one embodiment, the ceramic material provided by the present invention is prepared from any of the non-stoichiometric high-entropy boron-containing carbide powders provided in the first aspect of the present invention. The present invention does not limit the specific preparation method; in one embodiment, the ceramic material can be prepared using the following method:

[0084] Preparation method of ceramic bulk materials: using prepared XC y B z Ceramic powder was used as raw material and pressure sintered in a spark plasma sintering furnace. The sintering process parameters were: vacuum conditions (<5Pa), heating to 1900℃ at 100℃ / min, and holding at 50-60MPa for 10-30min to obtain bulk ceramics with a relative density >95%.

[0085] Preparation method of ceramic coating: using prepared XC y B zUsing ceramic powder as raw material, atmospheric plasma spraying equipment is used to spray the powder onto C / C composite material or graphite matrix to form a ceramic coating on the matrix surface. The spraying gas is N2, the powder feeding gas is Ar, the spraying voltage is 50-60V, the current is 500-600A, the spraying distance is 100mm, and the spraying angle is 90°.

[0086] The ceramic material provided by this invention has the characteristics of being dense, resistant to ablation, and having strong oxidation resistance.

[0087] The following will provide a more detailed description of the non-stoichiometric high-entropy boron-containing carbide powder, its preparation method, and its applications, with reference to specific embodiments.

[0088] Example 1

[0089] 1) Weigh out ZrCl4, HfCl4, TiCl4, and TaCl5 sequentially, with the molar ratio of Zr, Hf, Ti, and Ta being 0.3:0.3:0.3:0.1. Dissolve these substances in deionized water, and add NH3·H2O solution to the resulting mixture to adjust the pH to 7–8, causing a precipitate to form. After complete precipitate formation, filter the solid phase, wash with distilled water and ethanol, and dry at 40°C to obtain the precipitate, which contains element X.

[0090] 2) Add phenolic resin (first carbon source) to the precipitate containing element X. The molar ratio of the carbon atoms of the added phenolic resin to the total amount of metal atoms of element X is 1.7:1. After mixing and drying, the resulting mixture is subjected to carbonization treatment at 1600℃ for 30 min to obtain carbide powder.

[0091] 3) Add 1.5 wt% phenolic resin (second carbon source) to the carbide powder obtained above, mix in ethanol, and dry after uniform mixing to obtain a mixture. Then add boric acid to the mixture and mix in water. The molar ratio of boron atoms in the added boric acid to the total amount of metal atoms of element X is 0.16:1, the mass ratio of boric acid to carbide powder is p = 0.08, and the molar ratio of carbon in the second carbon source to boron in the boric acid is 0.75:1. The mixture obtained after mixing and drying is the second carbon source-boric acid-carbide powder composite.

[0092] 4) The aforementioned second carbon source-boric acid-carbide powder composite was subjected to high-temperature boronization under pressureless discharge plasma sintering conditions. The vacuum degree in the furnace was less than 5 Pa. The temperature was increased to 1700℃ at a heating rate of 50℃ / min and held for 30 min. Then it was cooled to room temperature to obtain non-stoichiometric high-entropy boron-containing carbide powder A1.

[0093] Figure 1The X-ray diffraction pattern of the high-entropy boron-containing carbide powder A1 prepared in Example 1 shows that the prepared high-entropy boron-containing carbide powder A1 has a single phase and no second phase is formed. Figure 2 This is a microstructure image of the high-entropy boron-containing carbide powder A1 prepared in Example 1. Figure 2 It can be seen that the particle size of the non-stoichiometric high-entropy boron-containing carbide powder is <1μm. ICP-OES elemental analysis shows that 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. The molecular formula of the high-entropy boron-containing carbide powder Al is (Zr... 0.3 Hf 0.3 Ti 0.3 Ta 0.1 (C) 0.70 B 0.15 The oxygen content of the sample was measured to be 0.05 wt% using a nitrogen, hydrogen, and oxygen analyzer.

[0094] Figure 5 This is a macroscopic morphology image of a high-entropy boron-containing carbide ceramic block prepared by sintering powder Al.

[0095] Example 2

[0096] 1) Weigh out ZrCl4, HfCl4, TiCl4, TaCl5, and NbCl5 sequentially, with the molar ratio of Zr, Hf, Ti, Ta, and Nb being 0.2:0.2:0.2:0.2:0.2. Dissolve these substances in deionized water, and add NaOH solution to the resulting mixture to adjust the pH to 7-8, causing a precipitate to form. After complete precipitate formation, filter the solid phase, wash with distilled water and ethanol, and dry at 40°C to obtain the precipitate, which contains element X.

[0097] 2) Add phenolic resin (first carbon source) to the precipitate containing element X. The molar ratio of the carbon atoms of the added phenolic resin to the total amount of metal atoms of element X is 1.9:1. After mixing and drying, the resulting mixture is subjected to carbonization treatment at 1900℃ for 20 min to obtain carbide powder.

[0098] 3) Add 0.5 wt% phenolic resin (second carbon source) to the carbide powder obtained above, mix in ethanol, and dry after uniform mixing to obtain a mixture. Then add boric acid to the mixture and mix in water. The molar ratio of boron atoms in the added boric acid to the total amount of metal atoms of element X is 0.05:1, the mass ratio of boric acid to carbide powder is p = 0.08, and the molar ratio of carbon in the second carbon source to boron in the boric acid is 0.8:1. The mixture obtained after mixing and drying is the second carbon source-boric acid-carbide powder composite.

[0099] 4) The aforementioned second carbon source-boric acid-carbide powder composite was subjected to high-temperature boronization under pressureless discharge plasma sintering conditions. The vacuum degree in the furnace was less than 5 Pa. The temperature was increased to 1300℃ at a heating rate of 150℃ / min and held for 60 min. Then it was cooled to room temperature to obtain non-stoichiometric high-entropy boron-containing carbide powder A2.

[0100] Figure 3 The image shows the X-ray diffraction pattern of the high-entropy boron-containing carbide powder A2 prepared in Example 2. The pattern indicates that the prepared high-entropy boron-containing carbide powder A2 has a single phase without the formation of a second phase. ICP-OES elemental analysis revealed that the atomic ratio of Zr, Hf, Ti, Ta, and Nb in powder A2 is 0.2:0.2:0.2:0.2:0.2, and the atomic ratio of C and B is 0.90:0.05. The non-stoichiometric high-entropy boron-containing 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 has a particle size of ~500nm (i.e., around 500nm), and its oxygen content is 0.20wt% as measured by a nitrogen, hydrogen, and oxygen analyzer.

[0101] Example 3

[0102] 1) Weigh out Zr(NO3)4, Hf(NO3)4, Ti(NO3)4, and Ta(NO3)5 sequentially, with a molar ratio of Zr:Hf:Ti:Ta of 0.25:0.25:0.25. Dissolve these substances in deionized water, and add KOH solution to the resulting mixture to adjust the pH to 7-8, causing a precipitate to form. After complete precipitate formation, filter the solid phase, wash with distilled water and ethanol, and dry at 40°C to obtain the precipitate containing element X.

[0103] 2) Add phenolic resin (first carbon source) to the precipitate containing element X. The molar ratio of the carbon atoms of the added phenolic resin to the total amount of metal atoms of element X is 1.8:1. After mixing and drying, the resulting mixture is subjected to carbonization treatment at 1600℃ for 40 min to obtain carbide powder.

[0104] 3) Add 1 wt% phenolic resin (second carbon source) to the carbide powder obtained above, mix in ethanol, and dry after uniform mixing to obtain a mixture. Then add boric acid to the mixture and mix in water. The molar ratio of boron atoms in the added boric acid to the total amount of metal atoms of element X is 0.11:1, the mass ratio of boric acid to carbide powder is p = 0.04, and the molar ratio of carbon in the second carbon source to boron in the boric acid is 0.9:1. The mixture obtained after mixing and drying is the second carbon source-boric acid-carbide powder composite.

[0105] 4) The aforementioned second carbon source-boric acid-carbide powder composite was subjected to high-temperature boronization under pressureless discharge plasma sintering conditions. The vacuum degree in the furnace was less than 5 Pa. The temperature was increased to 1800℃ at a heating rate of 100℃ / min and held for 30 min. Then it was cooled to room temperature to obtain non-stoichiometric high-entropy boron-containing carbide powder A3.

[0106] ICP-OES elemental analysis revealed that in powder A3, the atomic ratios of Zr, Hf, Ti, and Ta were 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 boron carbide molecular formula was (Zr... 0.25 Hf 0.25 Ti 0.25 Ta 0.25 (C) 0.80 B 0.10 The powder has a particle size of ~800nm, and its oxygen content is 0.11wt% as measured by a nitrogen, hydrogen and oxygen analyzer.

[0107] Example 4

[0108] 1) Weigh out Zr(NO3)4, Hf(NO3)4, Ti(NO3)4, and Ta(NO3)5 sequentially, with a molar ratio of Zr:Hf:Ti:Ta of 0.4:0.4:0.1:0.1. Dissolve the above substances in deionized water, and add NH3·H2O solution to the resulting mixture to adjust the pH to 7-8, causing a precipitate to form. After complete precipitation, filter the solid phase, wash with distilled water and ethanol, and dry at 40°C to obtain the precipitate, which contains element X.

[0109] 2) Add phenolic resin (first carbon source) to the precipitate containing element X. The molar ratio of the carbon atoms of the added phenolic resin to the total amount of metal atoms of element X is 1.65:1. After mixing and drying, the resulting mixture is subjected to carbonization treatment at 1600℃ for 30 min to obtain carbide powder.

[0110] 3) Add 2.5 wt% phenolic resin (second carbon source) to the carbide powder obtained above, mix in ethanol, and dry after uniform mixing to obtain a mixture. Then add boric acid to the mixture and mix in water. The molar ratio of boron atoms in the added boric acid to the total amount of metal atoms of element X is 0.22:1, the mass ratio of boric acid to carbide powder is p = 0.05, and the molar ratio of carbon in the second carbon source to boron in the boric acid is 1:1. The mixture obtained after mixing and drying is the second carbon source-boric acid-carbide powder composite.

[0111] 4) The aforementioned second carbon source-boric acid-carbide powder composite was subjected to high-temperature boronization under pressureless discharge plasma sintering conditions. The vacuum degree in the furnace was less than 5 Pa. The temperature was increased to 1800℃ at a heating rate of 100℃ / min and held for 30 min. Then it was cooled to room temperature to obtain non-stoichiometric high-entropy boron-containing carbide powder A4.

[0112] ICP-OES elemental analysis revealed that in 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 ultra-high temperature ceramic material is (Zr... 0.4 Hf 0.4 Ti 0.1 Ta 0.1 (C) 0.65 B 0.20 The powder has a particle size of ~500nm, and its oxygen content is 0.16wt% as determined by a nitrogen, hydrogen and oxygen analyzer.

[0113] Example 5

[0114] This embodiment is basically the same as Embodiment 1, except that TaCl5 is replaced with WCl5 while keeping the amount of metal elements in both equal, to obtain non-stoichiometric high-entropy boron carbide powder A5.

[0115] ICP-OES elemental analysis revealed that in 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 non-stoichiometric high-entropy boron carbide molecular formula was (Zr... 0.3 Hf 0.3 Ti 0.3 W 0.1 (C) 0.70 B 0.15 The powder has a particle size of ~900nm, and its oxygen content is 0.14wt% as measured by a nitrogen, hydrogen and oxygen analyzer.

[0116] Example 6

[0117] This embodiment is basically the same as Embodiment 1, except that TaCl5 is replaced with VCl3 while keeping the amount of metal elements in both equal, to obtain non-stoichiometric high-entropy boron carbide powder A6.

[0118] ICP-OES elemental analysis revealed that in powder A6, the atomic ratio of Zr, Hf, Ti, and V was 0.3:0.3:0.3:0.1, and the atomic ratio of C and B was 0.7:0.15. The non-stoichiometric high-entropy boron carbide molecular formula was (Zr... 0.3 Hf 0.3 Ti 0.3 V 0.1 (C) 0.70 B 0.15 The powder has a particle size of ~900nm, and its oxygen content is 0.15wt% as measured by a nitrogen, hydrogen and oxygen analyzer.

[0119] Example 7

[0120] This embodiment is basically the same as embodiment 2, except that...

[0121] The molar ratio of carbon atoms in the added phenolic resin (first carbon source) to the total amount of metal atoms of element X is 1.65:1.

[0122] The molar ratio of boron atoms to the total amount of metal atoms of element X in the added boric acid is 0.3:1, and the mass ratio of boric acid to carbide powder is 0.15.

[0123] A non-stoichiometric high-entropy boron carbide powder A7 was obtained.

[0124] ICP-OES elemental analysis revealed that in powder A7, the atomic ratios of Zr, Hf, Ti, Ta, and Nb were 0.2:0.2:0.2:0.2:0.2, and the atomic ratio of C and B was 0.65:0.3. The non-stoichiometric high-entropy boron carbide molecular formula was (Zr... 0.2 Hf 0.2 Ti 0.2 Ta 0.2 Nb 0.2 (C) 0.65 B 0.30 The powder has a particle size of ~500nm (i.e., around 500nm), and its oxygen content is 0.20wt% as measured by a nitrogen, hydrogen, and oxygen analyzer.

[0125] Example 8

[0126] This embodiment is basically the same as Embodiment 1, except that...

[0127] The molar ratio of carbon atoms in the added phenolic resin (first carbon source) to the total amount of metal atoms of element X is 1.65:1.

[0128] The molar ratio of boron atoms to the total amount of metal atoms of element X in the added boric acid is 0.3:1, and the mass ratio of boric acid to carbide powder is 0.15, resulting in non-stoichiometric high-entropy boron-containing carbide powder A8.

[0129] ICP-OES elemental analysis revealed that in powder A8, the atomic ratio of Zr, Hf, Ti, and Ta was 0.3:0.3:0.3:0.1, and the atomic ratio of C and B was 0.65:0.3. The non-stoichiometric high-entropy boron carbide molecular formula was (Zr... 0.3 Hf 0.3 Ti 0.3 Ta 0.1 (C) 0.65 B 0.30 The oxygen content of the sample was measured to be 0.18 wt% using a nitrogen, hydrogen, and oxygen analyzer.

[0130] Comparative Example 1

[0131] This comparative example is basically the same as Example 4, except that in step 3), 2 wt% phenolic resin (second carbon source) and boric acid are added to the high entropy carbide powder, mixed in ethanol, and dried after uniform mixing to obtain a mixture.

[0132] The molar ratio of boron atoms to the total amount of metal atoms of element X in the added boric acid is 0.22:1. The mixture obtained by mixing and drying is the second carbon source-boric acid-carbide powder composite.

[0133] Powder B1 was obtained.

[0134] Figure 4 The image shows the X-ray diffraction pattern of powder B1 prepared in Comparative Example 1. Figure 3 It can be seen that the diffraction peaks of Zr-Ti-Hf-Ta-CB solid solution phase, TiB2, HfB2 and m-HfO2 appear in powder B1, indicating that the powder is a mixture of these four substances. Among them, the Zr-Hf-Ti-Ta-CB solid solution shows the characteristic peak of ZrC, indicating that in step 3), the second carbon source and the boron source are mixed with the high-entropy carbide powder at the same time, and a single phase high-entropy boron-containing carbide solid solution powder cannot be formed.

[0135] Comparative Example 2

[0136] This comparative example is basically the same as Example 1, except that the molar ratio of carbon atoms to total metal atoms of element X in the phenolic resin added in step 2) is 2:1. After synthesizing the carbide powder, steps 3) and 4) are not performed, and powder B2 is obtained. Testing showed that the atomic ratio of Zr, Hf, Ti, Ta, and C in powder B2 is 0.3:0.3:0.3:0.1:0.98, and the molecular formula is (Zr...0.3 Hf 0.3 Ti 0.3 Ta 0.1 C 0.98 .

[0137] Test case

[0138] The antioxidant properties of the products prepared in Example 1 and Comparative Example 2 were tested, and the results are shown in Table 1. The antioxidant properties of the products prepared in Example 1 and Comparative Example 1 were tested using TG-DSC in an air atmosphere. The heating rate was 10 min / ℃, the product particle size was 0.5–1 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.

[0139] Table 1 Initial oxidation temperature data

[0140]

[0141]

[0142] As can be seen from the data in Table 1, the antioxidant properties of the non-stoichiometric high-entropy boron-containing carbide powders obtained in each embodiment are superior to those of the high-entropy carbides obtained in each comparative example.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A non-stoichiometric high-entropy boride carbide powder, characterized by, 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 according to claim 1, characterized in that, 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, characterized in that, 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, characterized in that, 0.65≤y≤0.95, y+z≤0.

95.

5. The powder according to any one of claims 1 to 4, characterized in that, 0.20＜z＜0.40。 6. A method for producing the powder according to any one of claims 1 to 5, characterized by, 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 according to claim 6 or 7, characterized in that, 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 according to any one of claims 6-8, characterized in that, 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 according to any one of claims 6-9, characterized in that, The alkaline substance comprises at least one of NaOH, KOH and ammonia.

11. The method according to any one of claims 6-10, characterized in that, 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 according to any one of claims 6-11, characterized in that, 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, characterized by, The ceramic material comprises the non-stoichiometric high-entropy borocarbide powder according to any one of claims 1-5; and / or, the material is prepared from the non-stoichiometric high-entropy borocarbide powder according to any one of claims 1-5.

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