A high-entropy rare earth hafnate ceramic coating material and a preparation method thereof

Abstract

The application relates to a high-entropy rare earth hafnate ceramic coating material and a preparation method thereof, and belongs to the technical field of high-entropy materials. The phase composition of the coating material is (Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 )2Hf2O7, which is a single-phase defect fluorite structure; the raw material powder is fully and uniformly mixed through wet ball milling, and then the raw material powder mixture is alloyed through a solid-phase sintering process to prepare the single-phase coating material, wherein the high-entropy rare earth hafnate ceramic element is uniformly distributed, the thermophysical performance is excellent, the high-temperature phase is stable, the coating material has low thermal conductivity and high thermal expansion coefficient, and has a wide application scene in the field of key high-end equipment thermal protection coating.

Description

Technical Field

[0001] This invention relates to a high-entropy rare-earth hafnium salt ceramic coating material and its preparation method, specifically, to a (Y) 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 The high-entropy rare earth hafnium salt ceramic coating material 2Hf2O7 and its preparation method belong to the field of high-entropy materials technology. Background Technology

[0002] Thermal protective coatings are widely used to protect aero-engine blades and high-temperature alloy components of gas turbines, shielding core metal components from harsh service environments such as high-temperature oxidation, gas erosion, and corrosion. With the increasing service temperatures of critical equipment like aero-engines, existing thermal protective coatings face challenges such as phase transformation at high temperatures and mismatches between their thermal expansion coefficients and the alloy substrate. To address these issues, researchers are actively developing novel thermal protective coatings that can meet and adapt to evolving needs.

[0003] Rare earth hafnium salts (RE₂Hf₂O₇, where RE represents rare earth elements) possess excellent properties such as high melting point and high-temperature phase stability, making them one of the most promising thermal protective coating material systems. RE₂Hf₂O₇ is an A₂B₂O₇ type rare earth oxide, typically exhibiting two crystal structures. When the ratio of the radius of the rare earth ion at the A site to the radius of the hafnium ion at the B site is 1.46–1.78, the crystal structure is a pyrochlore-type structure with ordered oxygen vacancies; when the ratio is <1.46, the crystal structure is a defect fluorite-type structure with disordered oxygen vacancies. The arrangement of oxygen vacancies in rare earth hafnium salts directly affects the crystal binding energy, i.e., the lattice energy, thus directly influencing the high-temperature structure and coefficient of thermal expansion. Therefore, exploring the correlation between the differences in crystal structure caused by variations in ion types in rare earth hafnium salts and their thermal properties provides a new method for improving the thermal performance of rare earth hafnium salts.

[0004] High-entropy rare-earth hafnium salts possess characteristics such as high-temperature structural stability and a high coefficient of thermal expansion. The alterations in crystal structure and thermal properties caused by differences in atomic radius have attracted widespread attention. Currently, research on (La...) 0.2 Ce 0.2 Pr 0.2 Sm 0.2 Eu 0.2 )2Hf2O7、(Y 0.25 Yb 0.25 Er 0.25 Lu 0.25 )2(Zr 0.5 Hf 0.5Studies of high-entropy rare-earth hafnium salts such as 2O7 have shown that the disorder of oxygen vacancies increases lattice distortion and thus enhances the anharmonic vibration of the lattice, thereby reducing the thermal conductivity. However, the coefficient of thermal expansion is low and the thermal expansion curve is not stable, which affects the service life of the thermal protective coating material and cannot efficiently solve the fundamental problem of matching the coefficient of thermal expansion with the substrate. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a high-entropy rare-earth hafnium salt ceramic coating material and its preparation method. The present invention introduces different types of rare-earth cations into the hafnium salt ceramic through a high-entropy treatment to form a single-phase solid solution with a defective fluorite structure. The different sizes of atoms in the crystal lattice cause atomic occupancy deviations, and the resulting lattice distortion effect increases phonon scattering, thereby reducing thermal conductivity. Simultaneously, the disordered arrangement of oxygen atom vacancies in the defective fluorite structure leads to a decrease in crystal binding energy. The lower the lattice energy, the higher the coefficient of thermal expansion. Therefore, the ceramic coating material exhibits very low thermal conductivity and a high coefficient of thermal expansion.

[0006] To achieve the objectives of this invention, the following technical solutions are provided.

[0007] A high-entropy rare-earth hafnium salt ceramic coating material, wherein the phase composition of the coating material is (Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 )2Hf2O7.

[0008] A method for preparing a high-entropy rare-earth hafnium oxide ceramic coating material according to the present invention comprises alloying powders of yttrium (Y), ytterbium (Yb), holmium (Ho), erbium (Er), thulium (Tm), and hafnium (Hf) oxides through a solid-state sintering process. The specific preparation steps are as follows:

[0009] (1) According to the phase composition of the coating material, each raw material powder is weighed according to the stoichiometric ratio, and mixed evenly by wet ball milling to form a slurry;

[0010] In step (1):

[0011] The raw material powder is an oxide of Y, an oxide of Yb, an oxide of Ho, an oxide of Er, an oxide of Tm, and an oxide of Hf.

[0012] The oxides of Y, Yb, Ho, Er, and Tm are preferably ≥99.5% pure, and the oxides of Hf are ≥99% pure.

[0013] Preferably, the particle size of the oxides of Y, Yb, Ho, Er, and Tm is ≤5μm, and the particle size of the oxide of Hf is ≤10μm.

[0014] Preferably, the mass ratio of the grinding balls to the raw material powder in the ball mill is 5:1.

[0015] Preferably, the milling medium for the ball mill is anhydrous ethanol.

[0016] Preferably, the ball milling speed is 200 r / min to 400 r / min, and the ball milling time is 10 h to 20 h.

[0017] (2) The slurry obtained in step (1) is dried to obtain powder, and the powder is heated to 1200-1600℃ and calcined at a constant temperature for 2-10 hours to obtain a high entropy rare earth hafnium salt ceramic coating material of the present invention.

[0018] In step (2):

[0019] Rotary evaporation is preferred for drying.

[0020] The preferred slurry is dried, then ground and sieved to obtain sieved powder, which is then heated and calcined.

[0021] Preferably, the powder is heated to 1200℃ to 1600℃ at a rate of 5℃ / min to 10℃ / min.

[0022] A high-entropy rare-earth hafnium salt ceramic coating is prepared by plasma spraying on a high-temperature nickel-based alloy substrate using a high-entropy rare-earth hafnium salt ceramic coating material as described in this invention as the spraying raw material.

[0023] Beneficial effects

[0024] (1) This invention provides a high-entropy rare-earth hafnium salt ceramic coating material, wherein the phase composition of the coating material is (Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 )2Hf2O7 is a single-phase defect fluorite structure; the coating material has excellent thermophysical properties, is stable at high temperatures, has low thermal conductivity and high thermal expansion coefficient, and has a wide range of applications in the field of thermal protection coatings for key high-end equipment.

[0025] (2) The present invention provides a high-entropy rare earth hafnium salt ceramic coating material. Each cation site in the sublattice of the coating material is surrounded by different metal atoms, thereby forming different bonds and lattice potential energies, increasing the diffusion activation energy and hindering atomic migration. This will greatly slow down the growth of grains, thereby increasing the high-temperature phase stability of the high-entropy material and solving the high-temperature phase transformation problem. After being heat-treated at 1500℃ for 18 hours, the average grain size increased from 0.64μm to 1.25μm (see Example 1). The high-temperature stability of the coating material is extremely high.

[0026] (3) This invention provides a high-entropy rare-earth hafnium salt ceramic coating material. The coating material forms a single-phase solid solution with a defective fluorite structure by introducing different types of rare-earth cations. These five rare-earth cations have similar radii. The high-entropy process does not change the crystal structure, but the lattice distortion effect caused by the atomic occupancy deviation in the crystal lattice can increase phonon scattering, thereby reducing the thermal conductivity. The average thermal conductivity of the coating material measured at 1200℃ can reach 0.826 W·m. -1 ·k -1 It is lower than most current heat-protective coating materials.

[0027] (4) This invention provides a high-entropy rare-earth hafnium salt ceramic coating material. The coating material has a defective fluorite structure, which is a highly symmetrical face-centered cubic structure. Due to the disordered arrangement of oxygen atom vacancies in the defective fluorite structure, the crystal binding energy is relatively low. The lower the lattice energy, the higher the coefficient of thermal expansion. Therefore, the coating material, which retains the defective fluorite structure after high-entropy treatment, has a high coefficient of thermal expansion. The average coefficient of thermal expansion of the coating material measured at 1200℃ can reach 12.6 × 10⁻⁶. -6 K -1 It is compatible with high-temperature nickel-based alloy substrates.

[0028] (5) The present invention provides a method for preparing a high-entropy rare earth hafnium salt ceramic coating material. In the preparation method, in step (1), the raw material powder is fully and uniformly mixed by wet ball milling, which can make the high-entropy rare earth hafnium salt ceramic element uniformly distributed and prevent the agglomeration and enrichment of a certain rare earth element.

[0029] (6) This invention provides a method for preparing a high-entropy rare earth hafnium salt ceramic coating material. In the preparation method, step (2) involves constant calcination at 1200-1600℃ for 2-10 hours. If the calcination conditions are not met, the final product obtained will contain RE2O3 (RE = Y, Yb, Ho, Er, Tm) and HfO2, in addition to the coating material described in this invention, which will affect the purity of the coating material and thus affect the thermal properties of the material.

[0030] The preferred method is to dry the slurry, then grind and sieve it to obtain sieved powder. This results in uniform calcined powder particles, which can make the coating material have a uniform particle size distribution and good particle morphology.

[0031] (7) The present invention provides a high-entropy rare earth hafnium salt ceramic coating. The coating material of the coating is a high-entropy rare earth hafnium salt ceramic coating material of the present invention, which is suitable for use on nickel-based high-temperature alloy substrates. The coating has excellent thermophysical properties, high-temperature phase stability, low thermal conductivity and high thermal expansion coefficient, and a smooth thermal expansion curve. The coating and the substrate are well matched, and it has a wide range of applications in the field of thermal protection coatings for key high-end equipment. Attached Figure Description

[0032] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the final product powder prepared in Example 1.

[0033] Figure 2 The image shows a scanning electron microscope (SEM) image of the bulk sample prepared in Example 1, and an elemental distribution map obtained from surface scanning elemental analysis of the image.

[0034] Figure 3 The image shows a scanning electron microscope (SEM) image of the bulk sample prepared in Example 1 after heat treatment at 1500℃ for 18 hours, and an elemental distribution map obtained by surface scanning elemental analysis of the image.

[0035] Figure 4 The thermal conductivity diagram is shown for the bulk sample prepared in Example 1.

[0036] Figure 5 The graph shows the coefficient of thermal expansion of the bulk sample prepared in Example 1. Detailed Implementation

[0037] To enable researchers in the field to better understand and implement the technical solution of the present invention, the present invention will be further illustrated below with reference to preferred embodiments and accompanying drawings. However, the embodiments are not intended to limit the present invention.

[0038] In the following embodiments:

[0039] The purity of Y2O3, Yb2O3, Ho2O3, Er2O3 and Tm2O3 is ≥99.5%, and the purity of HfO2 is ≥99%.

[0040] The particle size of Y2O3, Yb2O3, Ho2O3, Er2O3 and Tm2O3 is ≤5μm, and the particle size of HfO2 is ≤10μm.

[0041] The tests involved in the examples are as follows:

[0042] (1) X-ray diffraction (XRD)

[0043] Manufacturer: PANalytical (Netherlands); Instrument model: PANalytical Empyrean. Testing was performed using a Cu target. The operating voltage was 45KV, the current was 40mA, the scan rate was 10.2° / s, and the step size was 0.013°.

[0044] (2) Field emission scanning electron microscopy

[0045] Manufacturer: Carl Zeiss; Instrument model: Panaco EmpyreanZeiss / Auriga. The sample was ground and polished to a thickness of less than 0.5 mm, with the surface polished to a mirror finish and without significant imperfections. After gold sputtering, the surface morphology was measured. Compositional analysis of the sample was performed using an energy dispersive spectroscopy (EDS) instrument attached to a scanning electron microscope.

[0046] (3) Thermal conductivity

[0047] Manufacturer: Netzsch Instruments GmbH, Germany; Instrument Model: LFA-457. The thermal conductivity of the prepared high-entropy rare-earth hafnium oxide ceramic bulk was tested from room temperature to 1200℃ using a laser thermal conductivity meter. The sample was prepared into a 12.7mm diameter disc, and the discs were polished to a thickness of less than 2mm, with the surface polished to a glossy finish.

[0048] (4) Coefficient of thermal expansion

[0049] The thermal expansion rate of the sample was measured using a high-temperature thermal dilatometer, and the coefficient of thermal expansion of the sample at different temperatures was obtained using conventional calculation methods.

[0050] Manufacturer: Netzsch Instruments GmbH, Germany; Instrument Model: DIL402PC. The test block was cut to a size of 3mm × 3mm × 30mm, polished until both ends were parallel, and then placed in the instrument for testing.

[0051] It should be noted that, unless otherwise specified, all experimental materials described in this invention can be obtained commercially, and all experimental methods described are conventional methods unless otherwise specified.

[0052] Example 1

[0053] (1) According to the phase composition of the coating material (Y) 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 )2Hf2O7, weigh each raw material powder according to stoichiometry:

[0054] The powders of Y2O3, Yb2O3, Ho2O3, Er2O3, Tm2O3 and HfO2 were weighed in a molar ratio of 1:1:1:1:1:10.

[0055] The weighed raw material powder was added to a tetrafluoroethylene container, and zirconia grinding balls were added. The mass ratio of zirconia grinding balls to raw material powder was 5:1. Anhydrous ethanol was added to the ball milling media to cover the grinding balls and raw material powder. The ball mill speed was set to 300 r / min. The mixture was ball milled for 10 hours to form a slurry.

[0056] (2) The slurry obtained in step (1) is dried by a rotary evaporator at a drying temperature of 50°C for 1 hour to obtain powder. The powder is then ground and sieved through a 100-mesh sieve to obtain sieved powder. The sieved powder is placed in an alumina crucible and placed in the center of a muffle furnace. The temperature is raised to 1400°C at a rate of 5°C / min and calcined at a constant temperature for 2 hours to obtain the final product powder. The furnace is then cooled to room temperature.

[0057] In order to perform scanning electron microscopy observation, thermal conductivity and coefficient of thermal expansion testing, the powder after sieving in step (2) of this embodiment needs to be made into a block sample for testing. The specific method is as follows:

[0058] The sieved powder was initially compressed using a manual tablet press. The molds used were a 20mm diameter circular mold and a 5mm×5mm×50mm strip mold. The pressure was 8MPa, and the holding time was 1min. A second compression was then performed using cold isostatic pressing at a pressure of 250MPa for 5min, resulting in a green body.

[0059] The blank was placed in an alumina crucible and placed in the center of a muffle furnace. The temperature was increased to 1400℃ at a rate of 5℃ / min and calcined at a constant temperature for 2 hours to prepare a block sample for testing. The sample was then cooled to room temperature in the furnace.

[0060] The final product powder and bulk samples obtained in this embodiment were tested as follows:

[0061] (1) X-ray diffraction (XRD)

[0062] The cooled final product powder was then subjected to XRD analysis, and the test results are as follows: Figure 1 As shown, the positions of the diffraction peaks are consistent with the crystallographic characteristics of the defective fluorite structure, and there are almost no impurity peaks, indicating that the final product is a single phase.

[0063] (2) Field emission scanning electron microscopy

[0064] The cooled bulk sample was examined using an S-4800 field emission scanning electron microscope to observe its microstructure and elemental distribution. The results are as follows: Figure 2As shown, there are no obvious cracks on the surface of the bulk sample. The presence of some small pores indicates that the density of the bulk sample is not very high. The five metal elements are evenly distributed in the bulk sample, and there is no obvious element segregation.

[0065] In summary, the final product prepared in this embodiment is a high-entropy rare-earth hafnium salt ceramic coating material as described in this invention.

[0066] (3) High temperature stability test

[0067] The cooled bulk samples were treated at 1500℃ for 18 hours. After cooling, the microstructure and elemental distribution were observed using an S-4800 field emission scanning electron microscope. The results are as follows: Figure 3 As shown, after prolonged high-temperature treatment, the grain growth of the bulk sample is not obvious, and the element distribution is uniform, indicating that the high-entropy rare earth hafnium salt ceramic coating material prepared in this embodiment has good high-temperature stability.

[0068] (4) Thermal conductivity

[0069] The thermal conductivity test results of the cooled bulk sample are as follows: Figure 4 As shown, the thermal conductivity at 1200℃ is 0.826 W·m. -1 ·k -1 This demonstrates that the high-entropy rare-earth hafnium salt ceramic coating material prepared in this embodiment has good high-temperature thermal insulation performance.

[0070] (5) Coefficient of thermal expansion

[0071] The thermal expansion coefficient test results of the cooled block sample are as follows: Figure 5 As shown, the coefficient of thermal expansion at 1200℃ is 12.6 × 10⁻⁶. -6 K -1 This indicates that the high-entropy rare-earth hafnium salt ceramic coating material prepared in this embodiment has a high coefficient of thermal expansion and can be well adapted to high-temperature alloy substrates.

[0072] Example 2

[0073] (1) According to the phase composition of the coating material (Y) 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 )2Hf2O7, weigh each raw material powder according to stoichiometry:

[0074] The powders of Y2O3, Yb2O3, Ho2O3, Er2O3, Tm2O3 and HfO2 were weighed in a molar ratio of 1:1:1:1:1:10.

[0075] The weighed raw material powder was added to a tetrafluoroethylene container, and zirconia grinding balls were added. The mass ratio of zirconia grinding balls to raw material powder was 10:1. Anhydrous ethanol was added to the ball milling media to cover the grinding balls and raw material powder. The ball mill speed was set to 250 r / min. The mixture was ball milled for 15 hours to form a slurry.

[0076] (2) The slurry obtained in step (1) is dried by a rotary evaporator at a drying temperature of 50°C for 1 hour to obtain powder. The powder is then ground and sieved through a 100-mesh sieve to obtain sieved powder. The sieved powder is placed in an alumina crucible and placed in the center of a muffle furnace. The furnace is heated to 1300°C at a rate of 10°C / min and calcined for 4 hours to obtain the final product powder. The furnace is then cooled to room temperature.

[0077] In order to perform scanning electron microscopy observation, thermal conductivity and coefficient of thermal expansion testing, the powder after sieving in step (2) of this embodiment needs to be made into a block sample for testing. The specific method is as follows:

[0078] The sieved powder was initially compressed using a manual tablet press. The molds used were a 20mm diameter circular mold and a 5mm×5mm×50mm strip mold. The pressure was 8MPa, and the holding time was 1min. A second compression was then performed using cold isostatic pressing at a pressure of 250MPa for 5min, resulting in a green body.

[0079] The billet was placed in an alumina crucible and placed in the center of a muffle furnace. The temperature was increased to 1300℃ at a rate of 10℃ / min and calcined at a constant temperature for 4 hours to prepare a block sample for testing. The sample was then cooled to room temperature with the furnace.

[0080] The final product powder and bulk samples obtained in this embodiment were tested as follows:

[0081] (1) X-ray diffraction (XRD)

[0082] The cooled final product powder was then subjected to XRD analysis, and the test results are as follows: Figure 1 As shown, the positions of the diffraction peaks are consistent with the crystallographic characteristics of the defective fluorite structure, and there are almost no impurity peaks, indicating that the final product is a single phase.

[0083] (2) Field emission scanning electron microscopy

[0084] The cooled bulk sample was observed for its microstructure and elemental distribution using an S-4800 field emission scanning electron microscope. The results showed that there were no obvious cracks on the surface of the bulk sample. The presence of some small pores indicated that the density of the bulk sample was not very high. The five metal elements were evenly distributed in the bulk sample, and there was no obvious elemental segregation.

[0085] In summary, the final product prepared in this embodiment is a high-entropy rare-earth hafnium salt ceramic coating material as described in this invention.

[0086] (3) High temperature stability test

[0087] The cooled bulk sample was treated at 1500℃ for 18 hours. After cooling, the microstructure and elemental distribution were observed using an S-4800 field emission scanning electron microscope. The results showed that after long-term high-temperature treatment, the grain growth of the bulk sample was not obvious and the elemental distribution was uniform, indicating that the high-entropy rare earth hafnium salt ceramic coating material prepared in this embodiment has good high-temperature stability.

[0088] (4) Thermal conductivity

[0089] The thermal conductivity test results of the cooled bulk sample showed that the thermal conductivity was 0.82 W·m at 1200℃. -1 ·k -1 This demonstrates that the high-entropy rare-earth hafnium salt ceramic coating material prepared in this embodiment has good high-temperature thermal insulation performance.

[0090] (5) Coefficient of thermal expansion

[0091] The thermal expansion coefficient test results of the cooled block sample show that the thermal expansion coefficient at 1200℃ is 12.5×10⁻⁶. -6 K -1 This indicates that the high-entropy rare-earth hafnium salt ceramic coating material prepared in this embodiment has a high coefficient of thermal expansion and can be well adapted to high-temperature alloy substrates.

[0092] Example 3

[0093] (1) According to the phase composition of the coating material (Y) 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 )2Hf2O7, weigh each raw material powder according to stoichiometry:

[0094] The powders of Y2O3, Yb2O3, Ho2O3, Er2O3, Tm2O3 and HfO2 were weighed in a molar ratio of 1:1:1:1:1:10.

[0095] The weighed raw material powder was added to a tetrafluoroethylene container, and zirconia grinding balls were added. The mass ratio of zirconia grinding balls to raw material powder was 5:1. Anhydrous ethanol was added to the ball milling media to cover the grinding balls and raw material powder. The ball mill speed was set to 200 r / min. The mixture was ball milled for 20 hours to form a slurry.

[0096] (2) The slurry obtained in step (1) is dried by a rotary evaporator at a drying temperature of 50°C for 1 hour to obtain powder. The powder is then ground and sieved through a 100-mesh sieve to obtain sieved powder. The sieved powder is placed in an alumina crucible and placed in the center of a muffle furnace. The temperature is raised to 1200°C at a rate of 5°C / min and calcined at a constant temperature for 6 hours to obtain the final product powder. The furnace is then cooled to room temperature.

[0097] In order to perform scanning electron microscopy observation, thermal conductivity and coefficient of thermal expansion testing, the powder after sieving in step (2) of this embodiment needs to be made into a block sample for testing. The specific method is as follows:

[0098] The sieved powder was initially compressed using a manual tablet press. The molds used were a 20mm diameter circular mold and a 5mm×5mm×50mm strip mold. The pressure was 8MPa, and the holding time was 1min. A second compression was then performed using cold isostatic pressing at a pressure of 250MPa for 5min, resulting in a green body.

[0099] The billet was placed in an alumina crucible and then placed in the center of a muffle furnace. The temperature was increased to 1200℃ at a rate of 5℃ / min and calcined at a constant temperature for 6 hours to prepare a block sample for testing. The sample was then cooled to room temperature in the furnace.

[0100] The final product powder and bulk samples obtained in this embodiment were tested as follows:

[0101] (1) X-ray diffraction (XRD)

[0102] The cooled final product powder was then subjected to XRD analysis, and the test results are as follows: Figure 1 As shown, the positions of the diffraction peaks are consistent with the crystallographic characteristics of the defective fluorite structure, and there are almost no impurity peaks, indicating that the final product is a single phase.

[0103] (2) Field emission scanning electron microscopy

[0104] The cooled bulk sample was observed for its microstructure and elemental distribution using an S-4800 field emission scanning electron microscope. The results showed that there were no obvious cracks on the surface of the bulk sample. The presence of some small pores indicated that the density of the bulk sample was not very high. The five metal elements were evenly distributed in the bulk sample, and there was no obvious elemental segregation.

[0105] In summary, the final product prepared in this embodiment is a high-entropy rare-earth hafnium salt ceramic coating material as described in this invention.

[0106] (3) High temperature stability test

[0107] The cooled bulk sample was treated at 1500℃ for 18 hours. After cooling, the microstructure and elemental distribution were observed using an S-4800 field emission scanning electron microscope. The results showed that after long-term high-temperature treatment, the grain growth of the bulk sample was not obvious and the elemental distribution was uniform, indicating that the high-entropy rare earth hafnium salt ceramic coating material prepared in this embodiment has good high-temperature stability.

[0108] (4) Thermal conductivity

[0109] The thermal conductivity test results of the cooled bulk sample showed that the thermal conductivity at 1200℃ was 0.823 W·m. -1 ·k -1 This demonstrates that the high-entropy rare-earth hafnium salt ceramic coating material prepared in this embodiment has good high-temperature thermal insulation performance.

[0110] (5) Coefficient of thermal expansion

[0111] The thermal expansion coefficient test results of the cooled block sample showed that the thermal expansion coefficient was 12.7 × 10⁻⁶ at 1200℃. -6 K -1 This indicates that the high-entropy rare-earth hafnium salt ceramic coating material prepared in this embodiment has a high coefficient of thermal expansion and can be well adapted to high-temperature alloy substrates.

Claims

1. A high-entropy rare-earth hafnium salt ceramic coating material, characterized in that: The phase composition of the coating material is (Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 Tm 0.2 )2Hf2O7.

2. A method for preparing a high-entropy rare-earth hafnium salt ceramic coating material as described in claim 1, characterized in that: The coating material is prepared by alloying powders of yttrium oxide, ytterbium oxide, holmium oxide, erbium oxide, thulium oxide, and hafnium oxide through a solid-state sintering process.

3. The method for preparing a high-entropy rare-earth hafnium salt ceramic coating material according to claim 2, characterized in that: (1) According to the phase composition of the coating material, each raw material powder is weighed according to the stoichiometric ratio, and mixed evenly by wet ball milling to form a slurry; The raw material powder is an oxide of Y, an oxide of Yb, an oxide of Ho, an oxide of Er, an oxide of Tm, and an oxide of Hf; (2) The slurry is dried to obtain powder, and the powder is heated to 1200-1600℃ and calcined at a constant temperature for 2-10 hours to prepare a high-entropy rare earth hafnium salt ceramic coating material.

4. The method for preparing a high-entropy rare-earth hafnium salt ceramic coating material according to claim 3, characterized in that: In step (1), the purity of the oxides of Y, Yb, Ho, Er and Tm is ≥99.5%, and the purity of the oxide of Hf is ≥99%. The particle size of oxides of Y, Yb, Ho, Er, and Tm is ≤5μm, and the particle size of oxide of Hf is ≤10μm.

5. The method for preparing a high-entropy rare-earth hafnium salt ceramic coating material according to claim 3 or 4, characterized in that: In step (1), the mass ratio of grinding balls to raw material powder in the ball mill is 5:1; the grinding medium in the ball mill is anhydrous ethanol; the ball milling speed is 200 r / min to 400 r / min; and the ball milling time is 10 h to 20 h.

6. The method for preparing a high-entropy rare-earth hafnium salt ceramic coating material according to claim 3, characterized in that: In step (2), rotary evaporation is used for drying; the powder is heated to 1200℃~1600℃ at a rate of 5℃ / min~10℃ / min and calcined at a constant temperature for 2h~10h.

7. A method for preparing a high-entropy rare-earth hafnium salt ceramic coating material according to claim 3 or 6, characterized in that: In step (2), the slurry is dried, ground, sieved, and then heated and calcined to obtain sieved powder.

8. The method for preparing a high-entropy rare-earth hafnium salt ceramic coating material according to claim 5, characterized in that: In step (2), rotary evaporation is used for drying; after the slurry is dried, it is ground and sieved to obtain sieved powder; the powder is heated to 1200℃~1600℃ at a rate of 5℃ / min~10℃ / min and calcined at a constant temperature for 2h~10h.

9. A high-entropy rare-earth hafnium salt ceramic coating, characterized in that: The coating is prepared by using a high-entropy rare earth hafnium salt ceramic coating material as described in claim 1 as the spraying raw material and depositing it on a high-temperature nickel-based alloy substrate by plasma spraying.

Images