Thermal barrier coating material and preparation method thereof, thermal barrier coating and application thereof

Abstract

The present invention provides a thermal barrier coating material and a preparation method thereof, a thermal barrier coating and its application. The thermal barrier coating material includes Re-doped hafnium oxide, wherein Re is a trivalent Yb element and / or Lu element. In the present invention, after Re is doped into the hafnium oxide lattice, the trivalent Yb element and / or Lu element replaces the tetravalent hafnium ion. According to thermal conductivity theory, the difference between different types of ions forms point defects, which increases the asymmetry of the lattice and forms new phonon scattering centers. At the same time, a certain amount of oxygen vacancies is generated, which enhances phonon scattering, thereby reducing the phonon mean free path and reducing thermal conductivity. At the same time, the generation of oxygen vacancies also increases the ion spacing in the unit cell, promotes the elongation of Hf-O bonds, and thus leads to an increase in the thermal expansion coefficient. The thermal barrier coating material provided by the present invention has the advantages of good phase stability at high temperatures, low thermal conductivity, and high compatibility with the thermal expansion coefficient of the hot end components of aircraft engines.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal barrier coatings and relates to a thermal barrier coating material, in particular to a thermal barrier coating material and a preparation method thereof, a thermal barrier coating and applications thereof. Background Art

[0002] With the continuous advancement of modern aviation technology, the service temperature requirements for aircraft engines and gas turbines are becoming increasingly stringent. Thermal barrier coatings (TBCs) play a vital role in the industry because they combine high-temperature-resistant and highly insulating ceramic materials with substrates, reducing the surface temperature of hot-end components and improving the substrate's oxidation and corrosion resistance, thereby enhancing the engine's thrust-to-weight ratio and thermal efficiency. Traditional 8YSZ (6%-8% yttria-stabilized zirconia) TBCs are widely used in hot-end components in the aerospace industry due to their low thermal conductivity, high thermal expansion coefficient, and excellent impact resistance. However, 8YSZs are subject to phase transitions and severe sintering in service environments exceeding 1200°C, making them unsuitable for ultra-high-temperature applications.

[0003] CN108439977A discloses a high-temperature, low-thermal-conductivity hafnium oxide-based thermal barrier coating material and its preparation method, which belongs to the technical field of thermal barrier coating materials. The thermal barrier coating material is a yttrium oxide-stabilized hafnium oxide material system; the chemical composition of the material is Hf 1-x Y x O 2-0.5x , 0<x≤0.2. The material provided by this invention exhibits high-temperature phase stability and low radiative heat transfer at high temperatures. As a thermal barrier coating material, it can ensure that thermal conductivity does not increase significantly due to thermal radiation in the high-temperature service environment of the combustion chamber. However, the thermal expansion coefficient of this high-temperature, low-thermal-conductivity hafnium oxide-based thermal barrier coating material is poorly compatible with aircraft engine hot-end components, and the preparation method is relatively complex.

[0004] CN116535208A discloses a hafnium tantalum oxide ceramic powder, its preparation method, and application. The preparation method of the hafnium tantalum oxide ceramic powder of the invention comprises the following steps: 1) adding a strong metal ion coordinating agent to a hafnium source solution and a tantalum source solution, respectively, and heating and mixing them; then, mixing the two solutions, adding a weak metal ion coordinating agent; then, adding a mixture of an organic solvent and water, and heating and refluxing to obtain an HTO precursor solution; and 2) removing the solvent from the HTO precursor solution, solidifying and calcining the HTO ceramic powder. The preparation method of the hafnium tantalum oxide ceramic powder of the invention has the advantages of simple process, short cycle, wide source of raw materials, and low equipment requirements. The prepared hafnium tantalum oxide ceramic powder has metal element dispersion at the molecular level, high sintering activity, and can successfully sinter a single-phase Hf with a stable crystal structure at 800°C in a short time. However, the hafnium tantalum oxide ceramic powder has poor phase stability, strong thermal conductivity, and a thermal expansion coefficient that is less compatible with the hot end components of aircraft engines.

[0005] Therefore, there is an urgent need to develop and design a material with good phase stability, low thermal conductivity at high temperatures and compatible thermal expansion coefficient with the hot end components of aircraft engines as a thermal barrier coating material to meet the development needs of the next generation of high-performance aircraft engines. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a thermal barrier coating material and its preparation method, a thermal barrier coating and its application. The thermal barrier coating material provided in the present invention has the advantages of good phase stability at high temperatures, low thermal conductivity and high compatibility with the thermal expansion coefficient of the hot end components of aircraft engines.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a thermal barrier coating material, comprising Re-doped hafnium oxide, wherein Re is a trivalent Yb element and / or Lu element.

[0009] Since hafnium oxide and zirconium oxide have similar atomic structures and ionic radii, both exist in three phase structures: monoclinic, tetragonal and hexagonal. However, hafnium oxide has a higher melting point (about 2800°C) and a higher phase transition temperature (from monoclinic phase to tetragonal phase at 1750°C). Therefore, using hafnium oxide to replace zirconium oxide as an ultra-high temperature thermal barrier coating is a very promising research direction.

[0010] In the present invention, after Re is doped into the hafnium oxide lattice, trivalent Yb elements and / or Lu elements replace tetravalent hafnium ions. According to thermal conductivity theory, the differences between different types of ions form point defects, which increase the asymmetry of the lattice and form new phonon scattering centers. At the same time, a certain amount of oxygen vacancies are generated, which enhances phonon scattering, thereby reducing the phonon mean free path and reducing thermal conductivity. At the same time, the generation of oxygen vacancies also increases the ion spacing in the unit cell, promotes the elongation of the Hf-O bond, and thus leads to an increase in the thermal expansion coefficient. The thermal barrier coating material provided by the present invention has the advantages of good phase stability at high temperatures, low thermal conductivity, and high compatibility with the thermal expansion coefficient of the hot end components of aircraft engines.

[0011] Preferably, the chemical formula of the Re-doped hafnium oxide is: Hf x Re 1-x O 1.5+0.5x , wherein x is 0.8 to 0.95, for example, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94 or 0.95, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] In a second aspect, the present invention provides a method for preparing the thermal barrier coating material according to the first aspect, the method comprising:

[0013] A mixed solution containing Re oxide and Hf salt is mixed with a precipitant, and a precipitate is obtained after precipitation. The obtained precipitate is calcined in an air atmosphere to obtain Re-doped hafnium oxide.

[0014] Preferably, the method for preparing the mixed solution comprises:

[0015] Re oxide and Hf salt are preliminarily mixed according to the atomic stoichiometric ratio to obtain a mixture, and the obtained mixture is then mixed with water to obtain a mixed solution.

[0016] Preferably, the Hf salt includes any one of HfCl4, Hf(SO4)2 or Hf(NO)4 or a combination of at least two of them. Typical but non-limiting combinations include a combination of HfCl4 and Hf(SO4)2, a combination of Hf(SO4)2 and Hf(NO)4, or a combination of HfCl4, Hf(SO4)2 and Hf(NO)4.

[0017] Preferably, the Re oxide includes Yb2O3 and / or Lu2O3.

[0018] Preferably, said remixing comprises a first stirring, said first stirring being accompanied by heating.

[0019] Preferably, the first stirring speed is 700-900 rpm, and the time is 2-8 hours.

[0020] In the present invention, the first stirring speed is 700-900 rpm, for example, 700 rpm, 750 rpm, 800 rpm, 850 rpm or 900 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] The first stirring time described in the present invention is 2 to 8 hours, for example, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the heating temperature is 70-90°C, for example, it can be 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0023] Preferably, the remixing is stopped after the mixture of the mixture and water becomes clear, and then cooled to room temperature to obtain the mixed solution.

[0024] Preferably, the mixing comprises adding the mixed solution dropwise into the precipitant, accompanied by a second stirring.

[0025] Preferably, the precipitant comprises any one of aqueous ammonia, ammonium carbonate or ammonium bicarbonate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of aqueous ammonia and ammonium carbonate, a combination of ammonium carbonate and ammonium bicarbonate, or a combination of aqueous ammonia, ammonium carbonate and ammonium bicarbonate.

[0026] Preferably, the second stirring speed is 400-800 rpm.

[0027] The second stirring speed in the present invention is 400-800 rpm, for example, it can be 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm or 800 rpm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, when the precipitation stops, the pH value of the mixture of the mixed solution and the precipitant is 11 to 12, for example, it can be 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9 or 12, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, solid-liquid separation is further included between the precipitation and the calcination.

[0030] Preferably, the solid-liquid separation includes standing, filtering, first washing, suction filtration, second washing and drying performed in sequence.

[0031] Preferably, the liquid used in the first washing includes deionized water, and the pH of the washing liquid after the last washing is 8 to 9, for example, it can be 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9 or 9, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the drying temperature is 60-80° C. and the drying time is 6-8 hours.

[0033] The drying temperature in the present invention is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] The drying time in the present invention is 6 to 8 hours, for example, it can be 6 hours, 6.2 hours, 6.4 hours, 6.6 hours, 6.8 hours, 7 hours, 7.2 hours, 7.4 hours, 7.6 hours, 7.8 hours or 8 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the precipitate is crushed between the solid-liquid separation and the calcination.

[0036] Preferably, the particle size of the precipitate after crushing is less than 200 mesh, for example, it can be 199 mesh, 195 mesh, 190 mesh, 185 mesh, 180 mesh, 175 mesh, 170 mesh, 160 mesh, 150 mesh, 140 mesh, 130 mesh, 120 mesh, 110 mesh or 100 mesh, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the comminution method comprises grinding.

[0038] Preferably, the calcination temperature is 1000-1200° C., and the calcination time is 1-2 hours.

[0039] The calcination temperature in the present invention is 1000-1200°C, for example, 1000°C, 1050°C, 1100°C, 1150°C or 1200°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] The calcination time in the present invention is 1 to 2 hours, for example, it can be 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In a third aspect, the present invention provides a thermal barrier coating, which comprises the thermal barrier coating material described in the first aspect.

[0042] In a fourth aspect, the present invention provides an application of the thermal barrier coating described in the third aspect, wherein the thermal barrier coating is used for hot end components of an aircraft engine.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] In the present invention, after Re is doped into the hafnium oxide lattice, trivalent Yb elements and / or Lu elements replace tetravalent hafnium ions. According to thermal conductivity theory, the differences between different types of ions form point defects, which increase the asymmetry of the lattice and form new phonon scattering centers. At the same time, a certain amount of oxygen vacancies are generated, which enhances phonon scattering, thereby reducing the phonon mean free path and reducing thermal conductivity. At the same time, the generation of oxygen vacancies also increases the ion spacing in the unit cell, promotes the elongation of the Hf-O bond, and thus leads to an increase in the thermal expansion coefficient. The thermal barrier coating material provided by the present invention has the advantages of good phase stability at high temperatures, low thermal conductivity, and high compatibility with the thermal expansion coefficient of the hot end components of aircraft engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 1 and 2 are X-ray diffraction patterns of the thermal barrier coating materials in Examples 1 and 2.

[0046] Figure 2 This is the SEM image of the thermal barrier coating material in Example 1.

[0047] Figure 3 This is the SEM image of the thermal barrier coating material in Example 2. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0049] Example 1

[0050] This embodiment provides a thermal barrier coating material, which includes Re-doped hafnium oxide, where Re is a trivalent Yb element.

[0051] The chemical formula of the Re-doped hafnium oxide is: 0.9 Yb 0.1 O 1.95 .

[0052] The preparation method of the thermal barrier coating material is:

[0053] (1) Yb2O3 and HfCl4 were preliminarily mixed according to the atomic stoichiometric ratio to obtain a mixture, and the obtained mixture was remixed with water by first stirring at 800 rpm accompanied by heating at 90°C for 6 hours to obtain a mixed solution;

[0054] (2) A mixed solution containing Yb2O3 and HfCl4 was added dropwise to ammonia water, accompanied by a second stirring at a rotation speed of 600 rpm, and a precipitate was obtained after precipitation. When the precipitation stopped, the pH value of the mixed solution and ammonia water was 11.5. The mixture was allowed to stand and filtered in sequence, and then washed with deionized water until the pH of the last washing liquid was 8. Subsequently, it was filtered in sequence and washed with anhydrous ethanol, and then dried at 80°C for 6 hours to obtain a precipitate. The obtained precipitate was crushed to a particle size of less than 200 mesh and then sieved. It was then calcined at 1200°C in an air atmosphere for 2 hours to obtain Re-doped hafnium oxide powder.

[0055] The thermal barrier coating material is tested by an X-ray diffractometer, and its phase composition is analyzed by using an X-ray diffraction pattern. The diffraction angle 2θ range of 20° to 90° is selected for phase analysis to analyze its phase composition. Figure 1 It can be found that the XRD spectrum of the thermal barrier coating material in Example 1 does not contain any diffraction peaks of rare earth oxides, but only contains diffraction peaks of monoclinic and cubic hafnium oxide.

[0056] Example 2

[0057] This embodiment provides a thermal barrier coating material, which includes Re-doped hafnium oxide, where Re is a trivalent Lu element.

[0058] The chemical formula of the Re-doped hafnium oxide is: 0.9 Lu 0.1 O 1.95 .

[0059] The preparation method of the thermal barrier coating material is:

[0060] (1) Lu2O3 and HfCl4 were preliminarily mixed according to the atomic stoichiometric ratio to obtain a mixture, and the obtained mixture was remixed with water by first stirring at 750 rpm accompanied by heating at 90°C for 6 hours to obtain a mixed solution;

[0061] (2) A mixed solution containing Lu2O3 and HfCl4 was added dropwise to ammonia water, accompanied by a second stirring at a rotation speed of 600 rpm, and a precipitate was obtained after precipitation. When the precipitation stopped, the pH value of the mixed solution and ammonia water was 11.5. The mixture was allowed to stand and filtered in sequence, and then washed with deionized water until the pH of the last washing liquid was 8. Subsequently, it was filtered in sequence and washed with anhydrous ethanol, and then dried at 80°C for 6 hours to obtain a precipitate. The obtained precipitate was crushed to a particle size of less than 200 mesh and then sieved. It was then calcined at 1200°C in an air atmosphere for 1 hour to obtain Re-doped hafnium oxide powder.

[0062] The thermal barrier coating material is tested by an X-ray diffractometer, and its phase composition is analyzed by using an X-ray diffraction pattern. The diffraction angle 2θ range of 20° to 90° is selected for phase analysis to analyze its phase composition. Figure 1 It can be found that the XRD spectrum of the thermal barrier coating material in Example 1 does not contain any diffraction peaks of rare earth oxides, but only contains diffraction peaks of monoclinic and cubic hafnium oxide.

[0063] Example 3

[0064] This embodiment provides a thermal barrier coating material, which includes Re-doped hafnium oxide, where Re is a trivalent Yb element.

[0065] The chemical formula of the Re-doped hafnium oxide is: 0.8 Yb 0.2 O 1.9 .

[0066] The preparation method of the thermal barrier coating material is:

[0067] (1) Yb2O3 and HfCl4 were preliminarily mixed according to the atomic stoichiometric ratio to obtain a mixture, and the obtained mixture was remixed with water by first stirring at a speed of 900 rpm for 8 hours accompanied by heating at 70°C to obtain a mixed solution;

[0068] (2) A mixed solution containing Yb2O3 and HfCl4 was added dropwise to ammonia water, accompanied by a second stirring at a rotation speed of 400 rpm, and a precipitate was obtained after precipitation. When the precipitation stopped, the pH value of the mixed solution and ammonia water was 11. The mixture was allowed to stand and filtered in sequence, and then washed with deionized water until the pH of the last washing liquid was 8.5. Subsequently, it was filtered in sequence and washed with anhydrous ethanol, and then dried at 60°C for 8h to obtain a precipitate. The obtained precipitate was crushed to a particle size of less than 200 mesh and then sieved. It was then calcined at 1000°C in an air atmosphere for 2h to obtain Re-doped hafnium oxide powder.

[0069] Example 4

[0070] This embodiment provides a thermal barrier coating material, which includes Re-doped hafnium oxide, where Re is a trivalent Lu element.

[0071] The chemical formula of the Re-doped hafnium oxide is: 0.95 Lu 0.05 O 1.975 .

[0072] The preparation method of the thermal barrier coating material is:

[0073] (1) Lu2O3 and HfCl4 were preliminarily mixed according to the atomic stoichiometric ratio to obtain a mixture, and the obtained mixture was remixed with water by first stirring at 700 rpm accompanied by heating at 80°C for 5 hours to obtain a mixed solution;

[0074] (2) A mixed solution containing Lu2O3 and HfCl4 was added dropwise to ammonia water, accompanied by a second stirring at a rotation speed of 800 rpm, and a precipitate was obtained after precipitation. When the precipitation stopped, the pH value of the mixed solution and ammonia water was 12. The mixture was allowed to stand and filtered in sequence, and then washed with deionized water until the pH of the last washing liquid was 9. Subsequently, it was filtered in sequence and washed with anhydrous ethanol, and then dried at 70°C for 7 hours to obtain a precipitate. The obtained precipitate was crushed to a particle size of less than 200 mesh and then sieved. It was then calcined at 1100°C in an air atmosphere for 1.5 hours to obtain Re-doped hafnium oxide powder.

[0075] Example 5

[0076] This embodiment provides a thermal barrier coating material, except that the chemical formula of Re-doped hafnium oxide is Hf 0.7 Yb 0.3 O 1.85 Except for this, the rest are the same as in Example 1.

[0077] Example 6

[0078] This embodiment provides a thermal barrier coating material. The chemical formula of Re-doped hafnium oxide is: Hf 0.98 Yb 0.02 O 1.99 Except for this, the rest are the same as in Example 1.

[0079] Example 7

[0080] This embodiment provides a thermal barrier coating material, which is the same as that of embodiment 1 except that the pH value of the mixed solution and ammonia water is 10 when the precipitation stops.

[0081] Example 8

[0082] This embodiment provides a thermal barrier coating material, which is the same as that of embodiment 1 except that the pH value of the mixed solution and ammonia water is 13 when the precipitation stops.

[0083] Example 9

[0084] This embodiment provides a thermal barrier coating material, which is the same as that of embodiment 1 except that the calcination temperature is 800°C.

[0085] Example 10

[0086] This embodiment provides a thermal barrier coating material, which is the same as that of embodiment 1 except that the calcination temperature is 1600°C.

[0087] Comparative Example 1

[0088] This embodiment provides a thermal barrier coating material, which is the same as that of Example 1 except that Yb2O3 is replaced by La2O3 in an equal molar amount.

[0089] Comparative Example 2

[0090] This embodiment provides a thermal barrier coating material, which is the same as that of Example 1 except that Yb2O3 is replaced by an equal molar amount of Gd2O3.

[0091] Comparative Example 3

[0092] This embodiment provides a thermal barrier coating material, which is the same as that of Example 1 except that Yb2O3 is replaced by an equal molar amount of Dy2O3.

[0093] Synchronous thermal analysis TG-DSC was used to characterize whether the thermal barrier coating materials in Examples 1 to 10 and Comparative Examples 1 to 3 underwent phase change, decomposition, and other processes in the temperature range from room temperature to 1500°C. The phase change and decomposition of the thermal barrier coating materials obtained by the test are shown in Table 1.

[0094] Thermal barrier coating blocks were prepared using the thermal barrier coating materials of Examples 1-10 and Comparative Examples 1-3. The preparation method was as follows: pre-pressing the thermal barrier coating material at 20 MPa for 5 minutes, cold isostatically pressing the thermal barrier coating material at 180 MPa for 10 minutes, heating the material in a muffle furnace to 1200° C. at a heating rate of 10° C. / min, then heating the material to 1600° C. at a heating rate of 2° C. / min, holding the temperature for 6 hours, and then cooling the material to room temperature in the furnace to obtain a thermal barrier coating block. The surface morphology of the thermal barrier coating blocks obtained using the thermal barrier coating materials of Examples 1-10 and Comparative Examples 1-3 was analyzed using SEM. The microcracks on the surface of the thermal barrier coating material obtained by testing are shown in Table 1. Figure 2 This is an SEM image of the thermal barrier coating block obtained from the thermal barrier coating material in Example 1. Figure 3This is an SEM image of a thermal barrier coating block obtained from the thermal barrier coating material in Example 2;

[0095] The thermal barrier coating blocks obtained from the thermal barrier coating materials of Examples 1-10 and Comparative Examples 1-3 were processed into discs with a diameter of 12.7±0.2 mm. The density and porosity of the densified blocks were measured using the Archimedean drainage method. The heat capacity Cp of the solid solution was calculated using the Neumann-Kopp rule and the weighted average of the mass ratio based on the stoichiometric ratio. The thermal diffusivity measured by a laser thermal conductivity meter was calculated by multiplying the density and heat capacity to obtain the thermal conductivity. The intrinsic thermal conductivity was then calculated using the porosity correction formula. The room temperature thermal conductivity K1, thermal conductivity K2 at 1200°C, and thermal conductivity K3 in the range of 1400-1600°C of the thermal barrier coatings were measured and are shown in Table 2.

[0096] The thermal expansion curves of the thermal barrier coating blocks obtained from the thermal barrier coating materials in Examples 1 to 10 and Comparative Examples 1 to 3 were tested, and the average thermal expansion coefficient α of the thermal barrier coating at 200 to 1600° C. was shown in Table 2.

[0097] Table 1

[0098] Phase change and decomposition Microcracks Example 1 No phase change, no decomposition No microcracks Example 2 No phase change, no decomposition No microcracks Example 3 No phase change, no decomposition No microcracks Example 4 No phase change, no decomposition No microcracks Example 5 No phase change, no decomposition There are microcracks Example 6 No phase change, no decomposition There are microcracks Example 7 No phase change, no decomposition There are microcracks Example 8 No phase change, no decomposition No microcracks Example 9 Phase change, no decomposition There are microcracks Example 10 No phase change, no decomposition No microcracks Comparative Example 1 Phase change, no decomposition No microcracks Comparative Example 2 No phase change, no decomposition No microcracks Comparative Example 3 No phase change, no decomposition No microcracks

[0099] Table 2

[0100]

[0101]

[0102] From Table 1 and Table 2 and Figure 2 and Figure 3 We can get:

[0103] (1) It can be seen from the data in Table 1 and Table 2 that the thermal barrier coating materials in Examples 1 to 4 of the present invention have good phase stability at high temperatures, low thermal conductivity, and high compatibility with the thermal expansion coefficient of the hot end components of the aircraft engine; specifically, the TG curve of the thermal barrier coating material in Example 1 has no obvious weight loss, and the DSC curve has no endothermic or exothermic peak, indicating that there is no phase change during the heating process, and Yb 3+ Doped hafnium oxide exhibits good phase stability; the TG curve of the thermal barrier coating material in Example 2 shows no obvious weight loss, and the DSC curve has no endothermic or exothermic peaks, indicating that there is no phase change during the heating process. 3+ Doped hafnium oxide exhibits good phase stability; Figure 2 and Figure 3 No microcracks were found in the SEM images, indicating that Yb 3+ Doped Hafnium Oxide and Lu 3+ The structure of doped hafnium oxide is relatively dense, thus having higher stability; it is calculated that Yb 3+The average thermal expansion coefficient of hafnium oxide-doped ceramics at 200-1600°C is 13.07×10-6K -1 , has good thermal expansion compatibility with nickel-based high-temperature alloys, and Lu is obtained by calculation. 3+ The average thermal expansion coefficient of hafnium oxide-doped ceramics at 200-1600°C is 12.99×10 -6 K -1 , good thermal expansion compatibility with nickel-based high-temperature alloys;

[0104] (2) By comparing Example 1 with Examples 5 and 6, it can be seen that the chemical formula of Re-doped hafnium oxide in the present invention affects the phase change and decomposition, microcracks, K1, K2, K3 and α; when x in the chemical formula of Re-doped hafnium oxide is too small, microcracks will be generated, K1 will increase, K2 will increase, K3 will increase, and α will decrease. This is because the doped ytterbium oxide exceeds the solid solubility limit of hafnium oxide, so that excess ytterbium oxide precipitates at the grain boundaries, forming stress concentration, and also aggravates the element segregation in the system, increases thermal conductivity, and decreases thermal expansion coefficient; when x in the chemical formula of Re-doped hafnium oxide is too large, microcracks will be generated, K1 will increase, K2 will increase, K3 will increase, and α will decrease. This is because the doping content is too low, so that the lattice transformation of hafnium oxide is not significant, and the characteristics of monoclinic hafnium oxide such as low toughness, high thermal conductivity, and low thermal expansion coefficient are revealed;

[0105] (3) By comparing Example 1 with Examples 7 and 8, it can be seen that when the precipitation stops in the present invention, the low pH value of the mixed solution and ammonia water mixture will lead to the generation of microcracks, K1 becomes larger, K2 becomes larger, K3 becomes larger, and α becomes smaller. This is because the low pH value will make Yb 3+ ions failed to precipitate completely, and some Yb 3+ Ions will be lost during the subsequent washing process. When the pH value is high, it will not cause phase change and decomposition, nor will there be microcracks. The impact on K1, K2, K3, and α is also relatively small. However, the increase in the number of subsequent washings will increase the workload of waste liquid treatment, resulting in unnecessary waste.

[0106] (4) By comparing Example 1 with Examples 9 and 10, it can be seen that the calcination temperature in the present invention affects the phase change and decomposition, microcracks, K1, K2, K3 and α; when the calcination temperature is too low, it will lead to phase change, K1 becomes larger, K2 becomes larger, K3 becomes larger, and α becomes smaller. This is because the crystallinity of the powder is low at low calcination temperature, and Yb 3+ Ions diffuse into the monoclinic phase lattice, and the monoclinic phase transforms into the cubic phase. When the calcination temperature is too high, it will not cause phase change and decomposition, and there will be no microcracks. The impact on K1, K2, K3, and α is also relatively small, but too high a calcination temperature will also increase the preparation cost.

[0107] (5) By comparing Example 1 with Comparative Examples 1 to 3, it can be seen that the type of doping element Re in the present invention will affect the phase change and decomposition, microcracks, K1, K2, K3 and α; when the doping element Re is a trivalent La element, it will cause a phase change, K1 will increase, K2 will increase, K3 will increase, and α will decrease. This is because lanthanum oxide and hafnium oxide will react at high temperatures (above 1200°C) to form lanthanum hafnate, which will increase the difference in thermophysical properties from the hafnium oxide matrix; when the doping element Re is a trivalent Gd or Dy element, K1 will increase, K2 will increase, K3 will increase, and α will decrease. This is because the ionic radius of trivalent Gd and Dy elements is smaller than that of Yb element. After ion doping, the degree of change in the lattice potential energy of hafnium oxide is reduced, the degree of system disorder is reduced, and ultimately the thermal conductivity is increased and the thermal expansion coefficient is reduced.

[0108] In summary, after Re is doped into the hafnium oxide lattice in the present invention, trivalent Yb elements and / or Lu elements replace tetravalent hafnium ions. According to thermal conductivity theory, the differences between different types of ions form point defects, which increase the asymmetry of the lattice and form new phonon scattering centers. At the same time, a certain amount of oxygen vacancies are generated, which enhances phonon scattering, thereby reducing the phonon mean free path and reducing thermal conductivity. At the same time, the generation of oxygen vacancies will also increase the ion spacing in the unit cell, promote the elongation of the Hf-O bond, and thus lead to an increase in the thermal expansion coefficient. The thermal barrier coating material provided in the present invention has the advantages of good phase stability at high temperatures, low thermal conductivity, and high compatibility with the thermal expansion coefficient of the hot end components of aircraft engines.

[0109] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A thermal barrier coating material, characterized in that: The thermal barrier coating material includes Re-doped hafnium oxide, wherein the Re is a trivalent Yb element and / or a Lu element; The chemical formula of the Re-doped hafnium oxide is: x Re 1-x O 1.5+0.5x , where x is 0.8 to 0.

95.

2. A method for preparing the thermal barrier coating material according to claim 1, characterized in that: The preparation method comprises: A mixed solution containing Re oxide and Hf salt is mixed with a precipitant, and a precipitate is obtained after precipitation. The obtained precipitate is calcined in an air atmosphere to obtain Re-doped hafnium oxide.

3. The preparation method according to claim 2, characterized in that The method for preparing the mixed solution comprises: Re oxide and Hf salt are preliminarily mixed according to the atomic stoichiometric ratio to obtain a mixture, and the obtained mixture is then mixed with water to obtain a mixed solution.

4. The preparation method according to claim 2, characterized in that The Hf salt includes any one of HfCl4, Hf(SO4)2 or Hf(NO)4 or a combination of at least two of them.

5. The preparation method according to claim 2, characterized in that The Re oxide includes Yb2O3 and / or Lu2O3.

6. The preparation method according to claim 3, characterized in that The remixing includes a first stirring which is accompanied by heating.

7. The preparation method according to claim 6, characterized in that The first stirring speed is 700-900 rpm, and the time is 2-8 hours.

8. The preparation method according to claim 6, characterized in that The heating temperature is 70-90°C.

9. The preparation method according to claim 2, characterized in that The mixing includes adding the mixed solution dropwise into the precipitant, accompanied by a second stirring.

10. The preparation method according to claim 2, characterized in that The precipitant includes any one of ammonia water, ammonium carbonate or ammonium bicarbonate, or a combination of at least two of them.

11. The preparation method according to claim 9, characterized in that The second stirring speed is 400-800 rpm.

12. The preparation method according to claim 2, characterized in that When the precipitation stops, the pH value of the mixed solution and the precipitant is 11-12.

13. The preparation method according to claim 2, characterized in that Solid-liquid separation is also included between the precipitation and the calcination.

14. The preparation method according to claim 13, characterized in that The solid-liquid separation includes standing, filtering, first washing, suction filtration, second washing and drying performed in sequence.

15. The preparation method according to claim 14, characterized in that The liquid used in the first washing includes deionized water, and the pH of the washing liquid from the first washing to the last washing is 8-9.

16. The preparation method according to claim 14, characterized in that The drying temperature is 60-80° C. and the drying time is 6-8 hours.

17. The preparation method according to claim 13, characterized in that The precipitate is crushed between the solid-liquid separation and the calcination.

18. The preparation method according to claim 17, characterized in that: The crushing step is performed until the particle size of the precipitate is less than 200 meshes.

19. The preparation method according to claim 2, characterized in that: The calcination temperature is 1000-1200° C., and the calcination time is 1-2 hours.

20. A thermal barrier coating, characterized in that: The thermal barrier coating comprises the thermal barrier coating material according to claim 1.

21. An application of the thermal barrier coating according to claim 20, characterized in that: The thermal barrier coating is used for hot end components of aviation engines.

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