(TiZrHfNbTa) C single-phase high-entropy ceramic powder and preparation method thereof

Abstract

The invention discloses (TiZrHfNbTa) C single-phase high-entropy ceramic powder and a preparation method thereof, relates to the technical field of ceramic powder, and solves the problem that an existing high-entropy carbide ceramic powder preparation process is difficult to be suitable for industrial mass production. Respectively carrying out pre-grinding activation treatment on the metal oxide and the carbon source; mixing the pre-ground and activated metal oxide and the carbon source with the mixed molten salt, and performing ball milling in a solvent to form mixed slurry; casting the mixed slurry into a graphite ark, and drying to obtain pretreated powder; the pretreated powder is subjected to glue discharging and then fired; a two-stage heat preservation process is adopted, heat preservation is conducted for 1-4 h at the temperature of 800-1000 DEG C in the first stage, and heat preservation is conducted for 1-2 h at the temperature of 1200- And carrying out ball-milling crushing on the fired powder, and carrying out acid pickling, water washing and drying. Mass production and low-cost preparation can be achieved, and the comprehensive performance meets the industrial production and application requirements.

Description

Technical Field

[0001] This invention relates to the field of ceramic powder technology, specifically to a (TiZrHfNbTa)C single-phase high-entropy ceramic powder and its preparation method. Background Technology

[0002] The concept of high-entropy ceramics originates from high-entropy alloys, specifically referring to multi-element ceramic materials composed of five or more metallic elements in equal proportions. (TiZrHfNbTa)C, as one of the first high-entropy carbide ceramics to be systematically studied, not only inherits the core advantages of traditional carbide ceramics such as high melting point, high hardness, high strength, excellent thermal stability, oxidation resistance, and corrosion resistance, but also exhibits a synergistic enhancement effect in mechanical properties, thermal properties, radiation resistance, and ablation resistance that is superior to the average value of each single-component carbide. This makes it show broad application potential in extreme service environments (such as high temperature, strong corrosion, and strong radiation).

[0003] The preparation of high-performance ceramic materials relies heavily on high-quality ceramic powders. Key technical indicators include high purity, fine particle size, narrow particle size distribution, and high reactivity, which directly determine the overall performance of subsequent ceramic products. Currently, the mainstream preparation methods for (TiZrHfNbTa)C powders include solid solution method, chemical reaction method, carbothermic reduction method, and precursor synthesis method. While each method possesses certain technical feasibility, they all have significant limitations. The solid solution method uses single-component carbide powders as raw materials, forming high-entropy carbide powders through high-temperature solid solution reactions. For example, the literature "High entropy carbide: a novel class of multicomponent ceramics" reports the preparation of (TiZrHfNbTa)C powder with a particle size of 2 μm at 1950℃. The core drawback of this method is the excessively high preparation temperature, and the powder purity and particle size are highly dependent on the quality of the raw material carbide, resulting in generally large particle sizes in the synthesized products, which is insufficient to meet the requirements of high-performance ceramics for fine powder preparation.

[0004] The chemical reaction method uses elemental metal powder and carbon powder as raw materials to prepare target powders through mechanochemical synthesis, high-temperature heating synthesis, or combustion self-propagating synthesis. The literature "Synthesis of all equiatomic five-transition metals high entropy carbides of the IVB(Ti, Zr, Hf) and VB(V, Nb,Ta)groups by a low temperature route" uses a ball milling process of 50-70 hours to synthesize (TiZrHfNbTa)C powder with a particle size of 100-300 nm. However, this method has obvious industrialization bottlenecks. The raw material cost of metal powder is high, and the high chemical reactivity of elemental metals makes them very easy to react with oxygen in the air during the preparation process, introducing oxygen impurities, which makes it difficult to control the purity of the powder and requires strict operation process.

[0005] The carbothermal reduction method uses metal oxides and graphite powder as raw materials to prepare high-entropy carbide powders through a high-temperature vacuum carbothermal reduction reaction. The literature "Synthesis of single-phase high-entropy carbide powders" adopts a two-step process, first performing carbothermal reduction at 1600℃ and then solution treatment at 2000℃ to synthesize (TiZrHfNbTa)C powder with a particle size of 0.55μm and an oxygen content of 0.2wt.%. However, because this method relies on a solid-phase reaction mechanism, it has the inherent defect of slow mass transfer rate, resulting in problems such as high preparation temperature and poor uniformity of powder composition and particle size that have not yet been effectively solved.

[0006] The precursor synthesis method involves polymerizing a polymer precursor solution with uniform molecular-level dispersion of elements through a polymerization reaction containing metal monomers. This precursor is then subjected to high-temperature heat treatment to decompose and chemically react, ultimately forming a single-phase high-entropy carbide powder. The literature "Liquid precursor-derived high-entropy carbide nanopowders" describes dissolving transition metal chlorides in ethanol, adding furfuryl alcohol, and polymerizing at 60°C to prepare a liquid-phase precursor. Subsequent vacuum carbothermal reduction at 1400°C and heat treatment at 2000°C yield (TiZrHfNbTa)C powder. The main drawbacks of this method are its lengthy process, high production cost, and the environmental impact of using organic solvents, making it unsuitable for mass production.

[0007] In summary, there is currently no mature industrial-scale mass production technology for high-entropy ceramic powders, either domestically or internationally. Existing preparation methods are all limited to small-batch synthesis in the laboratory and generally suffer from common problems such as complex preparation processes, cumbersome operations, low production capacity, high production costs, and difficulty in ensuring product uniformity. This makes it difficult to directly extend to industrial-scale mass production and seriously restricts the application and promotion of high-entropy ceramic materials in practical engineering fields. Summary of the Invention

[0008] To address the problem that existing high-entropy carbide ceramic powder preparation processes are difficult to apply to large-scale industrial production, this invention proposes a (TiZrHfNbTa)C single-phase high-entropy ceramic powder and its preparation method.

[0009] The specific technical solution of the present invention is as follows: A method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder includes the following steps: S1. The metal oxide and carbon source are pre-ground and activated respectively; the metal oxide includes TiO2, ZrO2, HfO2, Nb2O5 and Ta2O5; the carbon source is selected from carbon black, sucrose or flour; S2. The pre-ground and activated metal oxide and carbon source are mixed with the mixed molten salt and then ball-milled in a solvent to form a mixed slurry; the mixed molten salt is an equal mass mixture of at least two of NaCl, KCl and CaCl2. S3. The mixed slurry is cast in a graphite boat and dried to obtain pretreated powder. S4. The pretreated powder is first debinded and then fired. The firing process is a two-stage heat preservation process under vacuum or argon atmosphere. The first stage is heated to 800~1000℃ and held for 1~4h. The second stage is heated to 1200~1400℃ and held for 1~2h. The vacuum degree is less than 100Pa under vacuum atmosphere. S5. The sintered mixed powder is ball-milled and crushed, then acid-washed, water-washed, and vacuum-dried to obtain (TiZrHfNbTa)C single-phase high-entropy ceramic powder.

[0010] Preferably, the molar ratio of the metal oxide and the carbon source is TiO2:ZrO2:HfO2:Nb2O5:Ta2O5:C=6-10x-10y:10x:10y:1:1:32, where 0.05≤x≤0.2 and 0.05≤y≤0.2.

[0011] The reaction equation is as follows: (6-10x-10y)TiO2+(10x)ZrO2+(10y)HfO2+Nb2O5+Ta2O5+32C=10(Ti 0.6-x-y Zr x Hf y Nb 0.2 Ta 0.2 )C+22CO↑ (0.05≤x≤0.2, 0.05≤y≤0.2).

[0012] Preferably, the TiO2 has a purity of 99.9% and a particle size of 1 μm; the ZrO2 has a purity of 99.5% and a particle size of 10 μm; the HfO2 has a purity of 99.5% and a particle size of 5 μm; the Nb2O5 has a purity of 99.9% and a particle size of 1.5 μm; the Ta2O5 has a purity of 99.9% and a particle size of 5 μm; when the carbon source is carbon black, the purity is 99.9% and the particle size is 2.5 μm; when the carbon source is sucrose or flour, the purity is 99%.

[0013] Preferably, the pre-grinding and activation process is as follows: ZrO2 grinding ball size 0.2~5mm, ball-to-material mass ratio 2~8:1, ball milling speed 300~500rpm, and ball milling time 2~8h.

[0014] Preferably, the solvent is a mixture of anhydrous ethanol and PVA deionized aqueous solution, with a mass ratio of 1:(0.33~3); the mass fraction of PVA in the PVA deionized aqueous solution is 0.2~2%.

[0015] Preferably, the purity of the molten salts NaCl, KCl, and CaCl2 is 99.5%.

[0016] Preferably, in step S2, the ratio of the pre-milled and activated metal oxide and carbon source to the mixed molten salt is 1:2~8; the ball milling process is as follows: ZrO2 grinding ball size 0.2~5mm, ball-to-material mass ratio 2~8:1, ball milling speed 600~700rpm, and ball milling time 2~8h.

[0017] Preferably, the drying temperature in step S3 is 90~100℃, and the drying time is 1~2h.

[0018] Preferably, the adhesive removal process involves heating to 400-600°C under a vacuum or argon atmosphere and holding at that temperature for 1-4 hours; wherein the vacuum level under the vacuum atmosphere is less than 100 Pa.

[0019] Preferably, the ball milling process in step S5 is as follows: the ZrO2 grinding ball size is 0.2~5mm, the ball-to-material ratio is 2~8:1 by mass, the ball milling speed is 300~400rpm, and the ball milling time is 4~8h; the acid washing solution is 5~10 vol.% dilute HCl or dilute HNO3, and the acid washing time is 1~2h; the water washing uses deionized water at 80~90℃, and the number of water washings is 2~3 times; the drying temperature is 90~100℃, and the time is 2~4h.

[0020] The present invention also provides a (TiZrHfNbTa)C single-phase high-entropy ceramic powder, which is prepared by the above-described preparation method.

[0021] Compared with the prior art, the specific beneficial effects of the present invention are as follows: This invention combines a mixed molten salt-assisted carbothermic reduction process with a two-stage heat preservation process at medium and high temperatures, along with industrial-grade equipment and a refined pretreatment process. This effectively addresses the technical challenge of achieving large-scale industrial production of high-entropy ceramic powders, achieving synergistic optimization in quality improvement, quantity increase, and cost reduction, thus laying a core foundation for its industrial application.

[0022] In terms of mass production capacity, this invention uses large-scale industrial equipment such as sand mills to build a mass production system, which can produce more than 50 kg of high-entropy ceramic powder per batch, greatly improving the scale of mass production. Moreover, the process is simple and easy to operate, and can be directly connected to the industrial production process, completely solving the bottleneck of small-batch and low-efficiency mass production in existing technologies.

[0023] The introduction of mixed molten salts provides crucial enhancement to the reaction and powder properties. The reaction medium, formed by liquefaction at high temperatures, transforms traditional gas-phase mass transfer into liquid-phase mass transfer, significantly improving raw material flowability and reactivity, and accelerating carbothermic reduction and solid solution reactions. Furthermore, the scientific combination of low- and high-melting-point components in the mixed molten salts precisely adapts to the two-stage heat preservation process, further optimizing wettability and flowability, and enhancing powder activity and reaction efficiency. Simultaneously, the powder prepared by this process is a single solid solution phase without impurities, with five cations uniformly distributed in the crystal lattice without agglomeration, making it compatible with a wider range of material systems. It also reduces heat preservation temperature and shortens heat preservation time, effectively inhibiting grain growth while improving preparation efficiency, resulting in fine and uniform powder particle size.

[0024] The refined pretreatment process is highly compatible with the core technology, further enhancing overall efficiency: Raw materials are pre-ground to an activated state, effectively solving the problems of difficulty in mixing and low activity caused by differences in original particle size and surface condition. This allows for more uniform dispersion in the molten salt, fully leveraging the auxiliary role of the mixed molten salt and ensuring the subsequent reduction and solution reaction proceeds fully. The precise control of the raw material to molten salt ratio avoids both insufficient molten salt leading to ineffective auxiliary effects and excessive molten salt causing waste and exacerbating furnace corrosion. It also avoids the problem of excessively low raw material concentration extending the mass transfer path, ensuring efficient progress in both reaction and solution processing. Furthermore, the addition of PVA dispersant refines particles, prevents agglomeration, and improves powder uniformity and flowability. Its adhesive properties enhance particle bonding and structural stability, while its lubricating effect reduces equipment wear, extends service life, and improves grinding efficiency. Precise matching of sand mill speed and ball milling time ensures microscopic uniform mixing of raw materials, refines particle size, avoids elemental fluctuations or unreacted cores, and prevents excessive grinding leading to ball wear, impurity introduction, and increased time costs.

[0025] The technological innovations not only reduce energy consumption but also ensure powder purity: This invention breaks away from the traditional slow heating-long holding mode. The mid-temperature stage focuses on completing the carbothermic reduction reaction, while the high-temperature stage achieves carbide solidification. This allows the two-stage reaction to proceed efficiently at their respective suitable temperatures, optimizing the reaction process, improving powder quality, shortening the high-temperature holding time, reducing molten salt volatilization and equipment corrosion, lowering energy consumption and maintenance costs, and significantly saving production costs. The low-temperature debinding process can completely remove the PVA binder, avoiding organic residue contamination of the powder and ensuring powder purity and subsequent sintering performance. The crushing process makes the ceramic powder and solidified molten salt in a loose, deagglomerated state, facilitating cleaning and separation, further improving the final powder purity.

[0026] In summary, this invention has the advantages of fast reaction rate, high powder purity, uniform element distribution, and fine and uniform particle size, while achieving mass production and low-cost preparation. Its comprehensive performance is suitable for industrial production and application needs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation process of (TiZrHfNbTa)C high-entropy ceramic powder; Figure 2 In Example 6 (Ti) 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 Laser particle size distribution diagram of high-entropy ceramic powder; Figure 3 In Example 6 (Ti) 0.2 Zr 0.2 Hf 0.2 Nb0.2 Ta 0.2 XRD pattern of high-entropy ceramic powder; Figure 4 In Example 6 (Ti) 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 SEM images of high-entropy ceramic powder; Figure 5 The XRD pattern of the high-entropy ceramic powder in Comparative Example 1; Figure 6 The XRD pattern of the high-entropy ceramic powder in Comparative Example 2; Figure 7 The XRD pattern of the high-entropy ceramic powder in Comparative Example 3; Figure 8 This is a SEM image of the high-entropy ceramic powder in Comparative Example 4. Detailed Implementation

[0028] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as limiting the present invention.

[0029] The ceramic powder preparation method provided by this invention is as follows: Figure 1 As shown.

[0030] Example 1. In this embodiment, (TiZrHfNbTa)C single-phase high-entropy ceramic powder was prepared by the following operation: (1) 6.13 kg TiO2, 9.46 kg ZrO2, 16.15 kg HfO2, 10.20 kg Nb2O5, 16.96 kg Ta2O5 powder and 14.75 kg carbon black were used as raw materials for preparing high-entropy ceramic powder; among which, the purity of TiO2 powder was 99.9% and the particle size was 1 μm; the purity of ZrO2 powder was 99.5% and the particle size was 10 μm; the purity of HfO2 powder was 99.5% and the particle size was 5 μm; the purity of Nb2O5 powder was 99.9% and the particle size was 1.5 μm; the purity of Ta2O5 powder was 99.9% and the particle size was 5 μm; the purity of carbon black was 99.9% and the particle size was 2.5 μm; 73.65 kg NaCl and 73.65 kg CaCl2 were mixed into a molten salt; (2) The metal oxide and carbon black in step (1) were pre-milled using a ball milling process. The ball milling process was as follows: the size of the ZrO2 milling ball was 0.5 mm, the ball-to-material mass ratio was 4:1, the ball milling speed was 300 rpm, and the ball milling time was 4 h. (3) Add the pre-ground powder and mixed molten salt obtained in step (2) into a sand mill, use 0.5mm ZrO2 grinding balls, the ball-to-material (including raw materials and molten salt) ratio is 4:1 by mass, and use a mixed solution of 0.2% PVA deionized water and anhydrous ethanol in a mass ratio of 1:0.5 as the grinding medium; (4) The mixture in step (3) is ball-milled at 600 rpm for 8 hours to obtain a uniformly mixed slurry; (5) Cast the mixed slurry from step (4) into a graphite boat and dry it at 90°C for 1 hour; (6) Place the graphite boat containing the mixed powder from step (5) into an atmosphere sintering furnace, replace the air three times and evacuate to below 100 Pa, first heat up to 400℃ and hold for 2 hours to remove the binder, then heat up to 800℃ in the first stage of medium temperature holding and hold for 4 hours, heat up to 1200℃ in the second stage of high temperature holding and hold for 2 hours, cool to room temperature and take out to obtain the mixed powder containing the target ceramic powder; (7) The mixed powder containing the target ceramic powder in step (6) is crushed by ball milling with a ball-to-material ratio of 4:1 by mass, a ball milling speed of 300 rpm, and a crushing time of 6 h. (8) The crushed powder from step (7) is acid-washed in dilute acid and cleaned with deionized water at 80°C. It is then dried in a vacuum drying oven at 100°C for 2 hours to obtain (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 C High-entropy ceramic powder.

[0031] Example 2. In this embodiment, (TiZrHfNbTa)C single-phase high-entropy ceramic powder was prepared by the following operation: (1) 14.15 kg TiO2, 5.46 kg ZrO2, 9.32 kg HfO2, 11.77 kg Nb2O5, 19.57 kg Ta2O5 powder and 40.43 kg sucrose were used as raw materials for preparing high-entropy ceramic powder; among which, the purity of TiO2 powder was 99.9% and the particle size was 1 μm; the purity of ZrO2 powder was 99.5% and the particle size was 10 μm; the purity of HfO2 powder was 99.5% and the particle size was 5 μm; the purity of Nb2O5 powder was 99.9% and the particle size was 1.5 μm; the purity of Ta2O5 powder was 99.9% and the particle size was 5 μm; the purity of sucrose was 99%; 154.58 kg KCl and 154.58 kg CaCl2 were mixed into a molten salt; (2) The metal oxide and sucrose in step (1) were pre-milled using a ball milling process. The ball milling process was as follows: the size of the ZrO2 milling ball was 5 mm, the ball-to-material mass ratio was 4:1, the ball milling speed was 400 rpm, and the ball milling time was 6 h. (3) Add the pre-ground powder and mixed molten salt obtained in step (2) into a sand mill, use 5mm ZrO2 grinding balls, the ball-to-material (including raw materials and molten salt) ratio is 4:1 by mass, and use a mixed solution of 0.8% PVA deionized water and anhydrous ethanol by mass ratio of 1:2 as the grinding medium. (4) The mixture in step (3) is ball-milled at 650 rpm for 4 hours to obtain a uniformly mixed slurry; (5) Cast the mixed slurry from step (4) into a graphite boat and dry it at 100°C for 2 hours; (6) Place the graphite boat containing the mixed powder from step (5) into an atmosphere sintering furnace, replace the air three times and introduce flowing argon to maintain a continuous slight positive pressure, first heat up to 400℃ and hold for 2 hours to remove the binder, then heat up to 900℃ in the first stage of medium temperature holding and hold for 2 hours, then heat up to 1300℃ in the second stage of high temperature holding and hold for 1 hour, cool to room temperature and take out to obtain a mixed powder containing the target ceramic powder; (7) The mixed powder containing the target ceramic powder in step (6) is crushed by ball milling with a ball-to-material ratio of 4:1 by mass, a ball milling speed of 300 rpm, and a crushing time of 6 h. (8) The crushed powder from step (7) is acid-washed in dilute acid and cleaned with deionized water at 80°C. It is then dried in a vacuum drying oven at 100°C for 2 hours to obtain (Ti 0.4 Zr 0.1 Hf 0.1 Nb 0.2 Ta 0.2 C High-entropy ceramic powder.

[0032] Example 3. In this embodiment, (TiZrHfNbTa)C single-phase high-entropy ceramic powder was prepared by the following operation: (1) 11.29 kg TiO2, 2.49 kg ZrO2, 17.00 kg HfO2, 10.74 kg Nb2O5, 17.85 kg Ta2O5 powder and 15.52 kg carbon black were used as raw materials for preparing high-entropy ceramic powder; among which, the purity of TiO2 powder was 99.9% and the particle size was 1 μm; the purity of ZrO2 powder was 99.5% and the particle size was 10 μm; the purity of HfO2 powder was 99.5% and the particle size was 5 μm; the purity of Nb2O5 powder was 99.9% and the particle size was 1.5 μm; the purity of Ta2O5 powder was 99.9% and the particle size was 5 μm; the purity of carbon black was 99.9% and the particle size was 2.5 μm; 149.78 kg NaCl, 149.78 kg KCl and 149.78 kg CaCl2 were mixed into a molten salt; (2) The metal oxide and carbon black in step (1) were pre-milled using a ball milling process. The ball milling process was as follows: the size of the ZrO2 milling ball was 2 mm, the ball-to-material mass ratio was 2:1, the ball milling speed was 500 rpm, and the ball milling time was 8 h. (3) Add the pre-ground powder and mixed molten salt obtained in step (2) into a sand mill, use 2mm ZrO2 grinding balls, the ball-to-material ratio (including raw materials and molten salt) is 2:1 by mass, and use a mixed solution of 0.5% PVA deionized water and anhydrous ethanol by mass ratio of 1:3 as the grinding medium. (4) The mixture in step (3) is ball-milled at 700 rpm for 4 hours to obtain a uniformly mixed slurry; (5) Cast the mixed slurry from step (4) into a graphite boat and dry it at 100°C for 2 hours; (6) Place the graphite boat containing the mixed powder in step (5) into an atmosphere sintering furnace, replace the air three times and introduce flowing argon to maintain a continuous slight positive pressure, first heat up to 600℃ and hold for 2 hours to remove the glue, then heat up to 900℃ in the first stage of medium temperature holding and hold for 1 hour, heat up to 1400℃ in the second stage of high temperature holding and hold for 1 hour, cool to room temperature and take out to obtain the mixed powder containing the target ceramic powder; (7) The mixed powder containing the target ceramic powder in step (6) is crushed by ball milling with a ball-to-material ratio of 4:1 by mass, a ball milling speed of 350 rpm, and a crushing time of 6 h. (8) The crushed powder from step (7) is acid-washed in dilute acid and cleaned with deionized water at 80°C. It is then dried in a vacuum drying oven at 100°C for 2 hours to obtain (Ti 0.35 Zr 0.05 Hf 0.2 Nb 0.2 Ta 0.2 C High-entropy ceramic powder.

[0033] Example 4. In this embodiment, (TiZrHfNbTa)C single-phase high-entropy ceramic powder was prepared by the following operation: (1) 10.22 kg TiO2, 10.51 kg ZrO2, 8.98 kg HfO2, 11.34 kg Nb2O5, 18.85 kg Ta2O5 powder and 38.94 kg sucrose were used as raw materials for preparing high-entropy ceramic powder; among which, the purity of TiO2 powder was 99.9% and the particle size was 1 μm; the purity of ZrO2 powder was 99.5% and the particle size was 10 μm; the purity of HfO2 powder was 99.5% and the particle size was 5 μm; the purity of Nb2O5 powder was 99.9% and the particle size was 1.5 μm; the purity of Ta2O5 powder was 99.9% and the particle size was 5 μm; the purity of sucrose was 99%; 76.28 kg NaCl and 76.28 kg KCl were mixed into a powder; (2) The metal oxide and sucrose in step (1) were pre-milled using a ball milling process. The ball milling process was as follows: the size of the ZrO2 grinding balls was 0.2 mm, the ball-to-material mass ratio was 4:1, the ball milling speed was 400 rpm, and the ball milling time was 8 h. (3) Add the pre-ground powder and mixed molten salt obtained in step (2) into a sand mill, use 0.2mm ZrO2 grinding balls, the ball-to-material (including raw materials and molten salt) ratio is 4:1 by mass, and use a mixed solution of 1% PVA deionized water and anhydrous ethanol by mass ratio of 1:1 as the grinding medium. (4) The mixture in step (3) is ball-milled at 650 rpm for 4 hours to obtain a uniformly mixed slurry; (5) Cast the mixed slurry from step (4) into a graphite boat and dry it at 100°C for 1 hour; (6) Place the graphite boat containing the mixed powder from step (5) into an atmosphere sintering furnace, replace the air three times and introduce flowing argon to maintain a continuous slight positive pressure, first heat up to 400℃ and hold for 2 hours to remove the glue, then heat up to 1000℃ in the first stage of medium temperature holding and hold for 1 hour, heat up to 1300℃ in the second stage of high temperature holding and hold for 2 hours, cool to room temperature and take out to obtain a mixed powder containing the target ceramic powder; (7) The mixed powder containing the target ceramic powder in step (6) is crushed by ball milling with a ball-to-material ratio of 4:1 by mass, a ball milling speed of 300 rpm, and a crushing time of 6 h. (8) The crushed powder from step (7) is acid-washed in dilute acid and cleaned with deionized water at 80°C. It is then dried in a vacuum drying oven at 100°C for 2 hours to obtain (Ti 0.3 Zr 0.2 Hf 0.1 Nb 0.2 Ta 0.2 C High-entropy ceramic powder.

[0034] Example 5. In this embodiment, (TiZrHfNbTa)C single-phase high-entropy ceramic powder was prepared by the following operation: (1) 19.16 kg TiO2, 2.96 kg ZrO2, 5.05 kg HfO2, 12.75 kg Nb2O5, 21.20 kg Ta2O5 powder and 40.09 kg flour were used as raw materials for preparing high-entropy ceramic powder; among which, the purity of TiO2 powder was 99.9% and the particle size was 1 μm; the purity of ZrO2 powder was 99.5% and the particle size was 10 μm; the purity of HfO2 powder was 99.5% and the particle size was 5 μm; the purity of Nb2O5 powder was 99.9% and the particle size was 1.5 μm; the purity of Ta2O5 powder was 99.9% and the particle size was 5 μm; the purity of flour was 99%; 159.14 kg NaCl and 159.14 kg CaCl2 were mixed into a molten salt; (2) The metal oxide and flour in step (1) were pre-milled using a ball milling process. The ball milling process was as follows: the size of the ZrO2 grinding ball was 1 mm, the ball-to-material mass ratio was 8:1, the ball milling speed was 300 rpm, and the ball milling time was 6 h. (3) Add the pre-ground powder and mixed molten salt obtained in step (2) into a sand mill, use 1mm ZrO2 grinding balls, the ball-to-material (including raw materials and molten salt) ratio is 8:1 by mass, and use a mixed solution of 2% PVA deionized water and anhydrous ethanol by mass ratio of 1:0.33 as the grinding medium. (4) The mixture in step (3) is ball-milled at 700 rpm for 2 hours to obtain a uniformly mixed slurry; (5) Cast the mixed slurry from step (4) into a graphite boat and dry it at 90°C for 2 hours; (6) Place the graphite boat containing the mixed powder in step (5) into an atmosphere sintering furnace, replace the air three times and evacuate to below 100 Pa, first heat up to 500℃ and hold for 2 hours to remove the binder, then heat up to 800℃ in the first stage of medium temperature and hold for 4 hours, heat up to 1300℃ in the second stage of high temperature and hold for 2 hours, cool to room temperature and take out to obtain the mixed powder containing the target ceramic powder; (7) The mixed powder containing the target ceramic powder in step (6) is crushed by ball milling with a ball-to-material ratio of 4:1 by mass, a ball milling speed of 400 rpm, and a crushing time of 6 h. (8) The crushed powder from step (7) is acid-washed in dilute acid and cleaned with deionized water at 80°C. It is then dried in a vacuum drying oven at 100°C for 2 hours to obtain (Ti 0.5 Zr 0.05 Hf 0.05 Nb 0.2Ta 0.2 C High-entropy ceramic powder.

[0035] Example 6. In this embodiment, (TiZrHfNbTa)C single-phase high-entropy ceramic powder was prepared by the following operation: (1) 6.13 kg TiO2, 9.46 kg ZrO2, 16.15 kg HfO2, 10.20 kg Nb2O5, 16.96 kg Ta2O5 powder and 14.75 kg carbon black were used as raw materials for preparing high-entropy ceramic powder; among which, the purity of TiO2 powder was 99.9% and the particle size was 1 μm; the purity of ZrO2 powder was 99.5% and the particle size was 10 μm; the purity of HfO2 powder was 99.5% and the particle size was 5 μm; the purity of Nb2O5 powder was 99.9% and the particle size was 1.5 μm; the purity of Ta2O5 powder was 99.9% and the particle size was 5 μm; the purity of carbon black was 99.9% and the particle size was 2.5 μm; 49.10 kg NaCl, 49.10 kg KCl and 49.10 kg CaCl2 were mixed into a molten salt; (2) The metal oxide and carbon black in step (1) were pre-milled using a ball milling process. The ball milling process was as follows: the size of the ZrO2 milling ball was 0.5 mm, the ball-to-material mass ratio was 8:1, the ball milling speed was 400 rpm, and the ball milling time was 4 h. (3) Add the pre-ground powder and mixed molten salt obtained in step (2) into a sand mill, use 0.5mm ZrO2 grinding balls, the ball-to-material (including raw materials and molten salt) ratio is 8:1 by mass, and use a mixed solution containing 1% PVA deionized water and anhydrous ethanol in a mass ratio of 1:0.5 as the grinding medium; (4) The mixture in step (3) is ball-milled at 700 rpm for 8 hours to obtain a uniformly mixed slurry; (5) Cast the mixed slurry from step (4) into a graphite boat and dry it at 95°C for 2 hours; (6) Place the graphite boat containing the mixed powder from step (5) into an atmosphere sintering furnace, replace the air three times and introduce flowing argon to maintain a continuous slight positive pressure, first heat up to 600℃ and hold for 2 hours to remove the glue, then heat up to 900℃ in the first stage of medium temperature holding and hold for 2 hours, then heat up to 1400℃ in the second stage of high temperature holding and hold for 1 hour, cool to room temperature and take out to obtain the mixed powder containing the target ceramic powder; (7) The mixed powder containing the target ceramic powder in step (6) is crushed by ball milling with a ball-to-material ratio of 4:1 by mass, a ball milling speed of 300 rpm, and a crushing time of 6 h. (8) The crushed powder from step (7) is acid-washed in dilute acid and cleaned with deionized water at 80°C. It is then dried in a vacuum drying oven at 100°C for 2 hours to obtain (Ti0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 C High-entropy ceramic powder.

[0036] The ceramic powder obtained in Example 6 was characterized by its particle size, such as... Figure 2 As shown, the particle size distribution of the powder, as measured by a laser particle size analyzer, ranges from 50 to 800 nm, with an average particle size of 183 nm.

[0037] The powder obtained in Example 6 was characterized by its particle size and phase composition, such as... Figure 3 As shown, the XRD diffraction pattern indicates that the high-entropy powder is in a single-phase solid solution state.

[0038] The microstructure of the powder obtained in Example 6 was characterized, and its scanning electron microscope image is shown below. Figure 4 As shown, the powder particles exhibit uniform microstructure.

[0039] Comparative Example 1. The procedure is the same as in Example 2, but step (1) is changed to use 12.51 kg ZrO2, 21.38 kg HfO2, 9.00 kg Nb2O5, 14.96 kg Ta2O5 powder, and 13.01 kg carbon black as raw materials for preparing high-entropy ceramic powder. The raw material composition and target product ratio are changed, while the preparation process parameters remain consistent. The prepared powder is characterized by phase analysis, and the XRD pattern is shown below. Figure 5 As shown in the figure, two sets of face-centered cubic carbide diffraction peaks are present, and the diffraction lines are significantly broadened. Further morphological and energy dispersive spectroscopy analysis of the powder indicates the presence of abnormally large particles, and the uneven distribution of metal elements within the particles. This suggests that under different compositional conditions, this process cannot prepare single-phase high-entropy carbide solid solution powders with the corresponding composition.

[0040] Comparative Example 2. Similar to Example 5, but the second high-temperature holding reaction temperature in step (6) is omitted, and the first stage holding time at 900℃ is extended to 6 hours. The prepared powder is characterized by its phase composition, and the XRD pattern is shown below. Figure 6 As shown in the figure, the powder exhibits diffraction peaks of two sets of face-centered cubic carbide solid solutions, along with a small number of unreacted oxide diffraction peaks. This indicates that under the same process conditions, the lack of high-temperature insulation prevents the solid solution reaction from proceeding fully and completely. The powder contains a small amount of incompletely dissolved carbide phases and unreacted oxide phases, making it impossible to generate single-phase high-entropy ceramic powder under these conditions.

[0041] Comparative Example 3. Same as Example 6, but the mixed molten salt of NaCl, KCl and CaCl2 in step (1) was replaced with an equal amount of single CaCl2 molten salt. The phase characterization results of the prepared powder are as follows: Figure 7 As shown, the XRD pattern reveals a significant broadening of the powder diffraction lines, along with the appearance of undissolved second-phase diffraction lines. Under the same process, compared to powder with a single solid solution phase in a mixed molten salt system, the auxiliary effect of a single molten salt is significantly reduced. Although it can ensure the carbothermic reduction reaction, it cannot guarantee the full progress of the solid solution reaction and the uniformity of the product. The powder contains face-centered cubic phases with varying degrees of solid solution. This result indicates that the completeness of the solid solution reaction under a single CaCl2 molten salt is significantly lower than that under a mixed molten salt system.

[0042] Comparative Example 4. Same as Example 6, but in step (6), "the first stage of medium-temperature holding is raised to 900℃ and held for 2 hours, and the second stage of high-temperature holding is raised to 1400℃ and held for 1 hour" is changed to "raised to 1400℃ and held for 4 hours". The SEM characterization results of the microstructure of the prepared powder are as follows: Figure 8 As shown, some particles are significantly enlarged, with an average particle size approaching 500 nm. Simultaneously, particle size uniformity decreases, and sintering necking occurs between grains, reducing the sintering activity of the powder. This comparative example illustrates that while traditional high-temperature, long-time heat treatment processes can produce single-phase high-entropy powders, the resulting high energy also significantly increases the average particle size, reducing the quality of the high-entropy powder.

[0043]

[0044] In summary, this invention proposes a molten salt-assisted method for the mass production of (TiZrHfNbTa)C ceramic powder. The molten salt-assisted carbothermal reduction method combined with a two-stage medium-high temperature heat treatment process ensures that the carbothermal reduction reaction in the powder proceeds synchronously and uniformly throughout the furnace. Simultaneously, the liquid phase environment provided by the molten salt shortens the diffusion path during the solid-phase reaction, effectively reducing the reaction temperature and solution time. This invention first pre-activates the raw materials and molten salt separately using ball milling. Then, the activated raw material powder and molten salt are mixed during wet ball milling using a sand mill. The uniformly mixed slurry is then dried by casting and placed in a graphite boat. Finally, the pre-treated powder undergoes debinding and a two-stage medium-high temperature heat treatment to produce (TiZrHfNbTa)C ceramic powder. This method utilizes large-scale industrial equipment such as sand mills to successfully synthesize high-entropy ceramic powder in large quantities, with a single batch production capacity of up to 50 kg. Characterization methods have demonstrated that the industrially synthesized powder has a single-phase face-centered cubic structure, uniform element distribution, high purity, and fine particle size.

[0045] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder, characterized in that, Includes the following steps: S1. The metal oxide and carbon source are pre-ground and activated respectively; the metal oxide includes TiO2, ZrO2, HfO2, Nb2O5 and Ta2O5; the carbon source is selected from carbon black, sucrose or flour; S2. The pre-ground and activated metal oxide and carbon source are mixed with the mixed molten salt and then ball-milled in a solvent to form a mixed slurry; the mixed molten salt is an equal mass mixture of at least two of NaCl, KCl and CaCl2. S3. The mixed slurry is cast in a graphite boat and dried to obtain pretreated powder. S4. The pretreated powder is first debinded and then fired. The firing process is a two-stage heat preservation process under vacuum or argon atmosphere. The first stage is heated to 800~1000℃ and held for 1~4h. The second stage is heated to 1200~1400℃ and held for 1~2h. S5. The sintered mixed powder is ball-milled and crushed, then acid-washed, water-washed, and vacuum-dried to obtain (TiZrHfNbTa)C single-phase high-entropy ceramic powder.

2. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 1, characterized in that, The molar ratio of the metal oxide and the carbon source is TiO2:ZrO2:HfO2:Nb2O5:Ta2O5:C=6-10x-10y:10x:10y:1:1:32, where 0.05≤x≤0.2 and 0.05≤y≤0.

2.

3. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 2, characterized in that, The purity of TiO2 is 99.9% and the particle size is 1 μm; the purity of ZrO2 is 99.5% and the particle size is 10 μm; the purity of HfO2 is 99.5% and the particle size is 5 μm; the purity of Nb2O5 is 99.9% and the particle size is 1.5 μm; the purity of Ta2O5 is 99.9% and the particle size is 5 μm; when the carbon source is carbon black, the purity is 99.9% and the particle size is 2.5 μm; when the carbon source is sucrose or flour, the purity is 99%.

4. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 1, characterized in that, The pre-grinding and activation process is as follows: ZrO2 grinding balls with a size of 0.2~5mm, a ball-to-material mass ratio of 2~8:1, a grinding speed of 300~500rpm, and a grinding time of 2~8h.

5. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 1, characterized in that, The solvent is a mixture of anhydrous ethanol and PVA deionized water solution, with a mass ratio of 1:(0.33~3); the mass fraction of PVA in the PVA deionized water solution is 0.2~2%.

6. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 1, characterized in that, In step S2, the ratio of the pre-ground and activated metal oxide and carbon source to the mixed molten salt is 1:2~8; the ball milling process is as follows: ZrO2 grinding ball size is 0.2~5mm, ball-to-material mass ratio is 2~8:1, ball milling speed is 600~700rpm, and ball milling time is 2~8h.

7. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 1, characterized in that, The drying temperature in step S3 is 90~100℃, and the drying time is 1~2h.

8. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 1, characterized in that, The process of removing the adhesive involves heating the product to 400-600°C under a vacuum or argon atmosphere and holding it at that temperature for 1-4 hours.

9. The method for preparing (TiZrHfNbTa)C single-phase high-entropy ceramic powder according to claim 1, characterized in that, The ball milling process described in step S5 is as follows: the ZrO2 grinding ball size is 0.2~5mm, the ball-to-material ratio is 2~8:1 by mass, the ball milling speed is 300~400rpm, and the ball milling time is 4~8h; the acid washing solution is 5~10 vol.% dilute HCl or dilute HNO3, and the acid washing time is 1~2h; the water washing uses deionized water at 80~90℃, and the water washing is performed 2~3 times; the drying temperature is 90~100℃, and the drying time is 2~4h.

10. A (TiZrHfNbTa)C single-phase high-entropy ceramic powder, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

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