A high thermal expansion coefficient and high entropy ceramic material and its preparation method

Abstract

This invention relates to the field of high-entropy ceramic materials technology, specifically to a high-entropy ceramic material with a high thermal expansion coefficient and its preparation method. High-entropy ceramic powder is prepared using trivalent rare earth element oxides and cerium oxide as raw materials through mechanical activation and a segmented sintering reaction method. The high-entropy ceramic powder is then pressed into discs, and the ceramic blanks are calcined in a muffle furnace. After calcination, the blanks are cooled with the furnace. The prepared high-entropy ceramic material is in the fluorite phase and exhibits lower thermal conductivity, good high-temperature phase stability, and a higher coefficient of thermal expansion.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy ceramic materials technology, specifically relating to a high thermal expansion coefficient high-entropy ceramic material and its preparation method. Background Technology

[0002] Thermal barrier coatings (TBCs) are crucial materials for providing thermal protection to aero-engines and gas turbines, extending their service life. They can increase inlet temperatures and reduce cooling requirements, thereby improving engine efficiency and the lifespan of hot components. Selecting a TBC requires meeting several important requirements, including low thermal conductivity, a coefficient of thermal expansion (CTE) that matches the metal substrate, high melting point, resistance to sintering, and high-temperature phase stability. Strong corrosion resistance is also essential. Among these, thermal conductivity and CTE are paramount; typically, the CTE of the coating is required to be >10 × 10⁻⁶. -6 K -1 .

[0003] Rare earth cerates are considered candidate materials for thermal barrier coatings due to their high thermal expansion coefficient and low thermal conductivity. They also exhibit good high-temperature phase stability. However, single-component cerates experience thermal shrinkage at 200-400℃. Past studies have used high-valence cations, such as Ta... 5+ W 6+ To replace Ce 4+ To mitigate the thermal expansion and contraction phenomenon, the effect was not ideal. With the introduction of the high-entropy concept into the ceramics field, the focus of solving this problem was on the high-entropy design of cerate, using high-entropy ceramics to alleviate this phenomenon. However, as the number of components increases, the configuration entropy of high-entropy ceramic materials increases, which means that the synthesis of high-entropy ceramics requires greater formation energy, so higher temperatures or longer holding times are needed. This means that the synthesis of high-entropy ceramics consumes more energy, takes longer, and requires higher sintering temperatures, which limits the synthesis of high-entropy ceramics.

[0004] Common powder preparation methods include solid-phase and liquid-phase methods. Solid-phase methods involve the direct reaction of raw materials in a solid state to obtain the desired solid compound. Based on processing characteristics, they can be further divided into mechanical pulverization and high-temperature solid-phase methods. Mechanical pulverization uses a pulverizer to directly grind and crush the raw materials into ultrafine powder, while high-temperature solid-phase methods involve thoroughly mixing metal salts or metal oxides according to a formula, grinding them, and then sintering them to undergo a solid-phase reaction, directly obtaining or further grinding ultrafine powder. The advantages of this method are low cost, simple process, no powder agglomeration, and good filling properties. The disadvantages are slower reaction rate, larger powder particle size, easy incorporation of impurities, and severe component segregation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-entropy ceramic material with a high thermal expansion coefficient, so as to solve the problems of low thermal expansion coefficient, high thermal conductivity, poor thermal stability and difficulty in forming high-entropy ceramic materials in thermal barrier coating materials.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high thermal expansion coefficient and high entropy ceramic material, which is prepared by the following steps:

[0007] Step A: Preparation of high-entropy ceramic powder: High-entropy ceramic powder is obtained by using oxides of trivalent rare earth elements and cerium oxide as raw materials, and by segmented sintering and mechanical activation.

[0008] Step (A-1): Using pure water as a solvent, the oxides of trivalent rare earth elements and cerium oxide are ball-milled and mixed to obtain slurry A;

[0009] The ratio of pure water to powder was 2:1, the ball milling speed was 400 rpm, the ball milling time was 12 hours, the ratio of large, medium and small grinding balls was 2:2:1, and the diameters of the grinding balls were 10 mm, 7 mm and 5 mm, respectively, to ensure that the powder was fully mixed.

[0010] Step (A-2): Filter slurry A through a standard sieve, dry it in an oven, and collect the dried powder after passing it through a standard sieve to obtain powder B;

[0011] The standard sieve is 200 mesh, and the sieve aperture size of the 200 mesh standard sieve is 0.0750 mm. The drying temperature of the oven is 80℃~100℃, and the drying time is 12 hours.

[0012] Step (A-3): Powder B is placed in a muffle furnace for segmented sintering. After each segment is sintered, it is mechanically activated and ball-milled. After sintering, it is cooled with the furnace to obtain high-entropy ceramic powder.

[0013] The muffle furnace sintering temperature is 1200–1500℃, and the sintering time for each segment is 1–4 hours. After each segment sintering, the powder is mixed with pure water for mechanical activation and ball milling. Repeated ball milling enhances the reaction effect of the solid powder, activates it, lowers the sintering temperature, and allows for better sample synthesis. The ball milling speed is 300–400 rpm, the milling time is 6–12 hours, the ball bead ratio is 2:2:1, and the bead diameters are 10 mm, 7 mm, and 5 mm. The powder is then dried in an oven at 80℃–100℃ for 8–12 hours.

[0014] Step B: Preparation of ceramic blocks: The sintered powder is crushed and sieved, and then pressed into round blocks in the pressing mold of a benchtop powder press. The ceramic blank is placed in a muffle furnace and sintered in sections with cerium oxide or high-entropy ceramic powder. After sintering, it is cooled with the furnace to obtain a high-entropy ceramic material with a high thermal expansion rate.

[0015] The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. The pressure of the benchtop powder press is 10-20 MPa, and the holding time is 2-5 min. The segmented sintering temperature is 1200-1500℃, and the sintering time at each temperature point is 2 hours. The block is embedded in cerium oxide or high-entropy ceramic powder for sintering to prevent the precipitation of elements in the block.

[0016] The chemical formula of the high-entropy ceramic powder prepared is (La 1 / 5 Sm 1 / 5 Er 1 / 5 Yb 1 / 5 Y 1 / 5 )2Ce2O7、(La 1 / 6 Sm 1 / 6Er 1 / 6 Yb 1 / 6 Y 1 / 6 Eu 1 / 6 )2Ce2O7 or (La 1 / 8 Sm 1 / 8 Er 1 / 8 Yb 1 / 8 Y 1 / 8 Eu 1 / 8 Gd 1 / 8 Nd 1 / 8 )2Ce2O7.

[0017] Beneficial effects:

[0018] This invention employs a mechanical activation and segmented sintering reaction method to synthesize high-entropy ceramic powder. This method inherits the advantages of the solid-state reaction method, such as its simplicity and low cost. The segmented ball milling and sintering makes the solid-state reaction more complete and reduces the activation energy, thus solving the disadvantages of high energy consumption and difficulty in synthesizing high-entropy ceramics. This makes it easier to form high-entropy ceramic powder and allows for better and faster production of high-entropy ceramic powder.

[0019] By comparing the phase composition XRD diffraction patterns of the powder prepared by the segmented solid-phase reaction and the high-entropy ceramic powder prepared by the direct solid-phase reaction at the same sintering time, it can be observed that the XRD diffraction pattern of the powder prepared by the direct solid-phase reaction method still has impurity peaks, indicating that the solid solution reaction is incomplete. However, the XRD diffraction peaks of the high-entropy ceramic powder prepared by the segmented solid-phase reaction method are clean and there are no impurity peaks, indicating that the solid solution reaction is complete. Fluorite characteristic peaks (111), (200), (220), (311), (222), (400), (331) and (420) can be detected in the XRD diffraction pattern. Therefore, the high-entropy ceramic thermal barrier coating material is a fluorite phase.

[0020] The high-entropy ceramics obtained by the method of this invention have higher thermal expansion coefficient, good high-temperature phase stability and low thermal conductivity, as well as higher Vickers hardness, Young's modulus and fracture toughness, which can meet the material selection requirements of thermal barrier coating materials. Attached image description:

[0021] Figure 1 SEM image (1 μm) of high-entropy ceramic powder in Example 1 of this invention;

[0022] Figure 2 XRD patterns of segmented ball milling sintered and direct sintered powders after four hours in Example 1 of this invention;

[0023] Figure 3 XRD pattern of the high-entropy ceramic bulk material in Embodiment 1 of the present invention;

[0024] Figure 4 Thermal conductivity curves of the high-entropy ceramic material prepared in Example 1 of this invention and Comparative Example 1;

[0025] Figure 5 Thermal expansion coefficient curves of the high-entropy ceramic material prepared in Example 1 of this invention and Comparative Example 1;

[0026] Figure 6 TG-DSC curve of the high-entropy ceramic material obtained in Example 1 of this invention;

[0027] Figure 7 The Vickers hardness, Young's modulus, and fracture toughness diagrams of the high-entropy ceramic materials prepared in the various embodiments of the present invention and Comparative Example 1. Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments.

[0029] Example 1

[0030] Step A: Preparation of high-entropy ceramic powder:

[0031] Step (A-1): Nine oxides, namely La2O3, Sm2O3, Er2O3, Yb2O3, Y2O3, Eu2O3, Nd2O3, Gd2O3 and CeO2, were mixed in a molar ratio of 1:1:1:1:1:1:1:1:16, using pure water as a solvent and a pure water to powder mass ratio of 2:1. The ball milling was performed with the ball milling beads in a ratio of large, medium and small sizes of 2:2:1, with ball milling bead diameters of 10mm:7mm:5mm, a rotation speed of 400 rpm, and a ball milling time of 12 hours to obtain slurry A.

[0032] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of the 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0033] Step (A-3): Sinter powder B at 1200℃ for 1 hour, cool to room temperature, mix the powder with pure water at a mass ratio of 1:2, and perform mechanical activation ball milling. The ratio of large, medium and small ball beads is 2:2:1, the diameter of the ball beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, and the ball milling time is 12 hours. Dry in an oven at 100℃ for 12 hours, then sinter at 1300℃ for 1 hour. Mix the powder with pure water at a mass ratio of 1:2, perform mechanical activation ball milling, and then dry (as above). Sinter the powder at 1400℃ for 1 hour, mix the powder with pure water at a mass ratio of 1:2, perform mechanical activation ball milling, and then dry (as above). Finally, sinter at 1500℃ for 1 hour to obtain high-entropy ceramic powder.

[0034] Step B: The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. 2g of powder is placed into the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa, and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace. It is held at 1200, 1300, 1400, and 1500℃ for two hours respectively, and then cooled with the furnace to obtain a single-phase high-entropy ceramic block with a fluorite structure.

[0035] Figure 1 This is a SEM image of the high-entropy ceramic bulk prepared by mechanical activation and segmented sintering in this embodiment. As can be seen from the image, the high-entropy ceramic bulk has obvious grain boundaries.

[0036] Figure 2The XRD patterns of high-entropy ceramic powder prepared by mechanical activation and segmented sintering reaction method are compared with those of high-entropy ceramic powder prepared by solid-state reaction method in Comparative Example 2. The figures show that the high-entropy ceramic powder sintered directly at 1500 degrees Celsius for four hours still has impurity peaks in its diffraction patterns, indicating that the solid-state reaction was incomplete. However, the high-entropy ceramic powder prepared by mechanical activation and segmented sintering gradually lost its impurity peaks as mechanical activation and ball milling sintering progressed, eventually resulting in clean diffraction peaks without any impurities. This indicates that the solid solution reaction was complete, and the desired high-entropy ceramic powder was fully generated. This demonstrates that the mechanical activation and segmented sintering reaction method can solve the problems of increased formation energy, long synthesis holding time, and high energy consumption associated with the increased number of components in high-entropy ceramics.

[0037] from Figure 3 As can be seen from the figure, the ceramic bulk synthesized by the segmented solid-state method in this embodiment has characteristic peaks of fluorite (111), (200), (220), (311), (222), (400), (331) and (420) detected in the phase composition XRD diffraction pattern. Therefore, the high-entropy ceramic thermal barrier coating material is a fluorite phase.

[0038] Figure 4 As can be seen from this, its thermal conductivity ranges from 1.34 to 0.94 W·m. –1 ·K –1 (200~1000℃);

[0039] Figure 5 Comparing the Chinese and comparative examples, it can be seen that the coefficient of thermal expansion is 11.27 × 10⁻⁶. -6 K -1 (25~850℃) and basically alleviates the thermal shrinkage phenomenon;

[0040] Figure 7 As can be seen from the data, its Vickers hardness is 9.91 GPa, its Young's modulus is 223.90 GPa, and its fracture toughness is 2.24 MPa·m. 1 / 2 This high-entropy ceramic block has the advantages of high stability, low thermal conductivity, high coefficient of thermal expansion, high hardness, Young's modulus, and high fracture toughness, and can be used as a thermal barrier coating material.

[0041] Example 2

[0042] Step A: Preparation of high-entropy ceramic powder:

[0043] Step (A-1): Seven oxides, La2O3, Sm2O3, Er2O3, Yb2O3, Y2O3, Eu2O3 and CeO2, were mixed by ball milling in a molar ratio of 1:1:1:1:1:1:12 with pure water as the solvent. The mass ratio of pure water to powder was 2:1. The ratio of large, medium and small ball mill beads was 2:2:1. The diameter of the ball mill beads was 10mm:7mm:5mm. The rotation speed was 400 rpm and the ball milling time was 12 hours to obtain slurry A.

[0044] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of a 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0045] Step (A-3): After sintering powder B at 1200℃ for 1 hour, mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation ball milling. The ratio of large, medium and small ball beads is 2:2:1, the diameter of the ball beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, and the ball milling time is 12 hours. Dry in an oven at 100℃ for 12 hours, then sinter at 1300℃ for 1 hour. Mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation, ball milling and drying (as above). Then sinter the powder at 1400℃ for 1 hour. Mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation, ball milling and drying (as above). Finally, sinter at 1500℃ for 1 hour to obtain high-entropy ceramic powder.

[0046] Step B: The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. 2g of powder is placed in the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa, and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace. It is held at 1200, 1300, 1400, and 1500℃ for two hours respectively, and then cooled with the furnace to obtain a single-phase high-entropy ceramic block with a fluorite structure.

[0047] The thermal conductivity of the high-entropy ceramic material prepared in this embodiment was measured to be 1.43–0.99 W·m. –1 ·K –1 (200~1000℃); coefficient of thermal expansion is 11.13×10 -6 K -1 (25~850℃). Its Vickers hardness is 9.77 GPa, Young's modulus is 209.67 GPa, and fracture toughness is 2.08 MPa·m. 1 / 2 ).

[0048] Example 3

[0049] Step A: Preparation of high-entropy ceramic powder:

[0050] Step (A-1): Six oxides, La2O3, Sm2O3, Er2O3, Yb2O3, Y2O3 and CeO2, were mixed by ball milling in a molar ratio of 1:1:1:1:1:10 with pure water as the solvent. The mass ratio of pure water to powder was 2:1. The ratio of large, medium and small ball mill beads was 2:2:1. The diameter of the ball mill beads was 10 mm, 7 mm and 5 mm. The rotation speed was 400 rpm and the ball milling time was 12 hours to obtain slurry A.

[0051] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of a 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0052] Step (A-3): After sintering powder B at 1200℃ for 1 hour, mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation ball milling. The ratio of large, medium and small ball beads is 2:2:1, the diameter of the ball beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, and the ball milling time is 12 hours. Dry in an oven at 100℃ for 12 hours, then sinter at 1300℃ for 1 hour. Mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation, ball milling and drying (as above). Then sinter the powder at 1400℃ for 1 hour. Mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation, ball milling and drying (as above). Finally, sinter at 1500℃ for 1 hour to obtain high-entropy ceramic powder.

[0053] Step B: The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. 2g of powder is placed into the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa, and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace at 1200-1500℃ in stages. It is held at 1200, 1300, 1400, and 1500℃ for two hours respectively, and then cooled with the furnace to obtain a single-phase high-entropy ceramic block with a fluorite structure.

[0054] The thermal conductivity of the high-entropy ceramic material prepared in this embodiment was measured to be 1.42–1.00 W·m. –1 ·K –1 (200~1000℃); coefficient of thermal expansion is 11.12×10 -6 K -1(25~850℃). Its Vickers hardness is 9.13 GPa, Young's modulus is 204.72 GPa, and fracture toughness is 1.97 MPa·m. 1 / 2 )

[0055] Example 4

[0056] Step A: Preparation of high-entropy ceramic powder:

[0057] Step (A-1): Nine oxides, namely La2O3, Sm2O3, Er2O3, Yb2O3, Y2O3, Eu2O3, Nd2O3, Gd2O3 and CeO2, were mixed by ball milling in a molar ratio of 1:1:1:1:1:1:1:1:16 with pure water as solvent. The ratio of large, medium and small ball beads was 2:2:1, the diameter of the ball beads was 10mm:7mm:5mm, the rotation speed was 400 rpm, and the ball milling time was 12 hours to obtain slurry A.

[0058] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of a 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0059] Step (A-3): After sintering powder B at 1200℃ for two hours, mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation ball milling. The ratio of large, medium and small ball beads is 2:2:1, the diameter of the ball beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, and the ball milling time is 12 hours. Dry in an oven at 100℃ for 12 hours, then sinter at 1300℃ for two hours. Mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation, ball milling and drying (as above). Then sinter the powder at 1400℃ for two hours. Mix the powder with pure water at a mass ratio of 1:2 and perform mechanical activation ball milling and drying (as above). Finally, sinter at 1500℃ for two hours to obtain high-entropy ceramic powder.

[0060] Step B: The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. 2g of powder is placed into the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa, and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace. It is held at 1200, 1300, 1400, and 1500℃ for two hours respectively, and then cooled with the furnace to obtain a single-phase high-entropy ceramic block with a fluorite structure.

[0061] The XRD patterns of high-entropy ceramic powder that was mechanically activated and sintered in sections for two hours showed the same trend as those of high-entropy ceramic powder that was mechanically activated and sintered in sections for one hour. Both could eventually produce high-entropy ceramic powder with complete reaction, but the sintering time was longer.

[0062] The thermal conductivity of the high-entropy ceramic material prepared in this embodiment was measured to be 1.35–

[0063] 0.95 W·m –1 ·K –1 (200~1000℃); coefficient of thermal expansion is 11.25×10 -6 K -1 (25~850℃). Its Vickers hardness is 9.85 GPa, Young's modulus is 219.42 GPa, and fracture toughness is 2.20 MPa·m. 1 / 2 )

[0064] Example 5

[0065] Step A: Preparation of high-entropy ceramic powder:

[0066] Step (A-1): Nine oxides, namely La2O3, Sm2O3, Er2O3, Yb2O3, Y2O3, Eu2O3, Nd2O3, Gd2O3 and CeO2, were mixed by ball milling in a molar ratio of 1:1:1:1:1:1:1:1:16 with pure water as solvent. The ratio of large, medium and small ball beads was 2:2:1, the diameter of the ball beads was 10mm:7mm:5mm, the rotation speed was 400 rpm, and the ball milling time was 12 hours to obtain slurry A.

[0067] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of a 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0068] Step (A-3): After sintering powder B at 1200℃ for 1 hour, the powder is mixed with pure water at a mass ratio of 1:2 and mechanically activated by ball milling. The ratio of large, medium and small ball beads is 2:2:1, the diameter of the ball beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, and the ball milling time is 12 hours. The powder is then dried in an oven at 100℃ for 12 hours, followed by sintering at 1350℃ for 2 hours. The powder is then mixed with pure water at a mass ratio of 1:2 and mechanically activated by ball milling, followed by drying (as above). Finally, the powder is sintered at 1500℃ for 1 hour. High-entropy ceramic powder is obtained through mechanically activated segmented sintering reaction method.

[0069] Step B: The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. 2g of powder is placed into the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa, and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace. It is held at 1200, 1300, 1400, and 1500℃ for two hours respectively, and then cooled with the furnace to obtain a single-phase high-entropy ceramic block with a fluorite structure.

[0070] The thermal conductivity of the high-entropy ceramic material prepared in this embodiment was measured to be 1.36–

[0071] 0.95 W·m –1 ·K –1 (200~1000℃); coefficient of thermal expansion is 11.22×10 -6 K -1 (25~850℃). Its Vickers hardness is 9.82 GPa, Young's modulus is 220.82 GPa, and fracture toughness is 2.19 MPa·m. 1 / 2 )

[0072] Example 6

[0073] Step A: Preparation of high-entropy ceramic powder:

[0074] Step (A-1): Nine oxides, namely La2O3, Sm2O3, Er2O3, Yb2O3, Y2O3, Eu2O3, Nd2O3, Gd2O3 and CeO2, were mixed by ball milling in a molar ratio of 1:1:1:1:1:1:1:1:16 with pure water as solvent. The ratio of large, medium and small ball beads was 2:2:1, the diameter of the ball beads was 10mm:7mm:5mm, the rotation speed was 400 rpm, and the ball milling time was 12 hours to obtain slurry A.

[0075] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of a 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0076] Step (A-3): After sintering powder B at 1200℃ for 2 hours, the powder is mixed with pure water at a mass ratio of 1:2 and mechanically activated by ball milling. The ratio of large, medium and small ball milling beads is 2:2:1, the diameter of the ball milling beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, the ball milling time is 12 hours, and the powder is dried in an oven at 100℃ for 12 hours. Then, it is sintered at 1500℃ for 2 hours to obtain high-entropy ceramic powder.

[0077] Step B: The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. 2g of powder is placed into the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa, and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace. It is held at 1200, 1300, 1400, and 1500℃ for two hours respectively, and then cooled with the furnace to obtain a single-phase high-entropy ceramic block with a fluorite structure.

[0078] The thermal conductivity of the high-entropy ceramic material prepared in this embodiment was measured to be 1.30–

[0079] 0.95 W·m –1 ·K –1 (200~1000℃); coefficient of thermal expansion is 11.20×10 -6 K -1 (25~850℃).

[0080] Comparative Example 1

[0081] Step A: Preparation of ceramic powder:

[0082] Step (A-1): Mix La2O3 and CeO2 oxides in a molar ratio of 1:2 with pure water as solvent by ball milling. The ratio of large, medium and small ball mill beads is 2:2:1, the diameter of the ball mill beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, and the ball milling time is 12 hours to obtain mixed dispersion system A.

[0083] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of a 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0084] Step (A-3): Place powder B in a muffle furnace for sintering in stages. After sintering powder B at 1200℃ for one hour, mix the powder with pure water at a mass ratio of 1:2 and mechanically activate it by ball milling. The ratio of large, medium, and small ball beads is 2:2:1, the diameter of the ball beads is 10mm:7mm:5mm, the rotation speed is 400 rpm, and the ball milling time is 12 hours. Dry the powder in an oven at 100℃ for 12 hours, then sinter at 1300℃ for one hour. Mix the powder with pure water at a mass ratio of 1:2 for mechanical activation, ball mill, and then dry (as above). Sinter the powder at 1400℃ for one hour, mix the powder with pure water at a mass ratio of 1:2 for mechanical activation, ball mill, and then dry (as above). Finally, sinter at 1500℃ for one hour to obtain ceramic powder.

[0085] Step B: The sintered ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the desired powder. 2g of powder is placed into the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa, and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace. The sintering is carried out in stages at 1200-1500℃, and the temperature is held at 1200, 1300, 1400, and 1500℃ for two hours respectively. The block is then cooled with the furnace to obtain a single-phase high-entropy ceramic block with a fluorite structure.

[0086] Figure 4 As can be seen from this, its thermal conductivity is 2.10–1.52 W·m. –1 ·K –1 (200~1000℃); Figure 5 The coefficient of thermal expansion can be seen to be 10.51 × 10⁻⁶. -6 K -1 (25~850℃) and exhibits significant thermal shrinkage. Its Vickers hardness is 4.36 GPa, Young's modulus is 159.61 GPa, and fracture toughness is 1.36 MPa·m. 1 / 2 .

[0087] Comparative Example 2

[0088] Step A: Preparation of high-entropy ceramic powder:

[0089] Step (A-1): Nine oxides, namely La2O3, Sm2O3, Er2O3, Yb2O3, Y2O3, Eu2O3, Nd2O3, Gd2O3 and CeO2, were mixed by ball milling in a molar ratio of 1:1:1:1:1:1:1:1:16 with pure water as solvent. The ratio of large, medium and small ball beads was 2:2:1, the diameter of the ball beads was 10mm:7mm:5mm, the rotation speed was 400 rpm, and the ball milling time was 12 hours to obtain slurry A.

[0090] Step (A-2): Pass slurry A through a 200-mesh sieve. The sieve aperture size of a 200-mesh standard sieve is 0.075mm. Place it in an oven to dry at a temperature of 100℃ for 12 hours. After drying, pass the powder through a 200-mesh sieve again to obtain powder B.

[0091] Step (A-3): After directly sintering powder B at 1500℃ for four hours, high-entropy ceramic powder is obtained by solid-state reaction method;

[0092] Step B: The sintered high-entropy ceramic powder is crushed, ground, and passed through a 200-mesh sieve to obtain the required powder. 2g of powder is placed in the tableting mold of a benchtop powder tablet press and pressed into a round block. The pressure of the benchtop powder tablet press is 15MPa and the holding time is 2min. The ceramic block is embedded with cerium dioxide and sintered in a muffle furnace. It is held at 1200, 1300, 1400, and 1500℃ for two hours respectively, and then cooled with the furnace to obtain the high-entropy ceramic block.

[0093] Observation of the XRD images revealed impurities in the XRD diffraction peaks, indicating that the high-entropy ceramic powder, which was directly sintered at 1500 degrees Celsius for 4 hours, did not react completely, and the desired product was not fully obtained.

[0094] 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 the claims of this patent application.

Claims

1. A method for preparing a high-entropy ceramic material, characterized in that, The chemical formula of the high-entropy ceramic material is: (La 1 / 6Sm 1 / 6 Er 1 / 6 Yb 1 / 6 Y 1 / 6 Eu 1 / 6 )2Ce2O7 or (La 1 / 8 Sm 1 / 8 Er 1 / 8 Yb 1 / 8 Y 1 / 8 Eu 1 / 8 Gd 1 / 8 Nd 1 / 8 The preparation method of the high-entropy ceramic material is as follows: 2Ce2O7; Step A: The preparation method of high-entropy ceramic powder is as follows: Step (A-1): Using pure water as a solvent, the oxides of trivalent rare earth elements and cerium oxide are ball-milled and mixed to obtain slurry A; Step (A-2): Filter slurry A through a standard sieve, dry it in an oven, and collect the dried powder after passing it through a standard sieve to obtain powder B; Step (A-3): Place powder B into a muffle furnace for sintering in sections. After each section is sintered, mix the powder with pure water, mechanically activate and ball mill it. After sintering, cool it with the furnace to obtain high-entropy ceramic powder. Among them, the ball milling speed for mechanical activation is 300-400 rpm, and the activation time is 6-12 hours; the segmented sintering is: chemical formula (La) 1 / 6 Sm 1 / 6 Er 1 / 6 Yb 1 / 6 Y 1 / 6 Eu 1 / 6 The high-entropy ceramic of 2Ce₂O₇ is made by sintering powder B in stages at 1200℃, 1300℃, 1400℃, and 1500℃; its chemical formula is (La₂O₇). 1 / 8 Sm 1 / 8 Er 1 / 8 Yb 1 / 8 Y 1 / 8 Eu 1 / 8 Gd 1 / 8 Nd 1 / 8 The high-entropy ceramic of 2Ce2O7 is made by sintering powder B in segments at 1200℃, 1300℃, 1400℃, and 1500℃, or sintering powder B in segments at 1200℃, 1350℃, and 1500℃, or sintering powder B in segments at 1200℃ and 1500℃; the sintering time for each segment is 1-2 hours, and the total sintering time is 4-8 hours. Step B: The high-entropy ceramic powder is crushed, ground, and sieved. The powder is assembled into a pressing mold and pressed into a block structure. The block structure is embedded in the powder and placed in a muffle furnace for sintering. The temperature is held at 1200℃, 1300℃, 1400℃, and 1500℃ for two hours respectively to obtain high-entropy structure ceramic. The powder used for embedding is cerium oxide or prepared high-entropy ceramic powder.

2. The method for preparing high-entropy ceramic materials according to claim 1, characterized in that, In step A, the ratio of mechanically activated ball milling beads is 2:2:1, and their sizes are 10mm, 7mm, and 5mm respectively. The mass ratio of pure water to powder is 2:

1.

3. The method for preparing high-entropy ceramic materials according to claim 1, characterized in that, In step B, when pressing the block material, the pressure of the benchtop powder tablet press is 10-20 MPa, and the holding time is 2-5 min.

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