Yb-sc co-doped gdzoh superhigh-temperature low-thermal-conductivity hydrogen barrier coating material and preparation method thereof

Abstract

The application relates to a ytterbium-scandium co-doped gadolinium zirconate ultra-high-temperature low-thermal-conductivity hydrogen barrier coating material and a preparation method thereof. x at% Yb and y at% Sc are doped into a Gd2Zr2O7 matrix, wherein 2.5<=x<=15.5, 2.5<=y<=9.5, and at% represents the proportion of doped atoms in the total of Gd, Yb and Sc. A ytterbium-scandium co-doped gadolinium zirconate ceramic powder is prepared by using a chemical coprecipitation method and a calcination method. The powder prepared by the method has small particle size and uniform distribution, and the method is simple, low in energy consumption and suitable for large-scale production. The material performance is better through comparison of the phase stability, thermal conductivity and hydrogen permeation rate of the material with those of Gd2Zr2O7 and 12.5 at% Yb doped Gd2Zr2O7, so that the ultra-high-temperature and hydrogen permeation challenges faced by engine hot end components can be solved simultaneously in application, which is an indirect and powerful proof that the material can be applied as a high-temperature hydrogen barrier coating.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen-protective ceramic materials, specifically relating to a low-hydrogen-permeability ytterbium-scandium co-doped gadolinium zirconate ultra-high temperature low thermal conductivity hydrogen coating material and its preparation method. Background Technology

[0002] Under extreme operating conditions in aerospace engines, turbine blade metal substrates are subjected to ultra-high temperature environments exceeding 1000 ℃ for extended periods. Meanwhile, with the development of hydrogen energy, hydrogen-powered aero-engines are facing the negative impact of hydrogen on materials. Turbine blades and other hot-end components of engines face two major failure challenges: First, high-temperature heat transfer causes overheating of the substrate and weakening of structural strength, necessitating the use of low thermal conductivity insulating coatings to reduce the heat load; second, hydrogen readily penetrates the protective layer and seeps into the metal substrate, causing hydrogen embrittlement, bulging, and interlayer delamination, significantly shortening the service life of components.

[0003] Gadolinium zirconate (Gd₂Zr₂O₇) is a typical rare-earth zirconate ceramic, and its unique crystal structure makes it a top choice for ultra-high temperature thermal insulation coatings. Its crystals contain a large number of oxygen vacancies, resulting in a thermal conductivity at high temperatures far lower than that of traditional zirconia ceramics. Furthermore, it exhibits excellent high-temperature chemical stability, allowing it to stably perform its thermal insulation function under ultra-high temperature conditions for extended periods. After doping Gd₂Zr₂O₇ with ytterbium, Yb... 3+ Replacement Gd 3+ Inducing lattice distortion further reduces thermal conductivity and increases the coefficient of thermal expansion, alleviating thermal mismatch stress between the coating and the substrate; it also enhances fracture toughness, and the phase stability temperature exceeds 1600℃, exhibiting excellent resistance to CMAS corrosion from environmental deposits. However, the large number of oxygen vacancies in Gd₂Zr₂O₇ and Yb-doped Gd₂Zr₂O₇ also provides channels for hydrogen diffusion, resulting in weak hydrogen barrier performance. It can only achieve a single thermal insulation function, making it difficult to adapt to high-temperature hydrogen-containing operating conditions, thus limiting its engineering application in hydrogen-powered aero engines.

[0004] To address the high hydrogen permeability of Yb-doped Gd₂Zr₂O₇, it is proposed to introduce Sc for further modification of the material. Sc has a smaller radius than Yb and Gd, and during doping, it may enter oxygen vacancies, reducing the oxygen vacancy concentration in the system and simultaneously inducing lattice distortion, thereby decreasing the hydrogen permeation rate. This invention aims to modify Gd₂Zr₂O₇ through ytterbium-scandium co-doping, relying on the combined action of the two ions to simultaneously achieve low thermal conductivity and low hydrogen permeability, thus meeting the practical application requirements of high-temperature stability, low thermal conductivity, and low hydrogen permeability. Summary of the Invention

[0005] The purpose of this invention is to overcome the inherent defects of existing Gd2Zr2O7 coatings and single-doped modified coating materials, and to provide a low hydrogen permeability ytterbium-scandium co-doped Gd2Zr2O7 ultra-high temperature and low thermal conductivity coating material and its preparation method. By synergistic doping of ytterbium and scandium, the crystal structure parameters and defect characteristics of Gd2Zr2O7 are controlled, and the high temperature resistance and hydrogen barrier ability of the coating are improved simultaneously, so as to achieve long-term protection of engine hot-end components in high temperature and strong hydrogen environment.

[0006] This invention combines experimental and VASP first-principles calculations to characterize material properties: X-ray diffraction was used to scan raw materials and bulk materials heat-treated at 1400 °C for 300 h at 20°–85° to analyze phase composition and high-temperature stability; thermal conductivity was measured using laser scintillation to determine the thermal diffusivity of the material, while the specific heat capacity and density of the bulk were simultaneously tested. Thermal conductivity was calculated using the formula λ = k·C. p ·ρ is calculated (where λ is thermal conductivity, k is thermal diffusivity, and C is thermal diffusivity). p (where ρ is the specific heat capacity and ρ is the density) to compare the thermal insulation performance of different systems; a crystal model is constructed based on VASP, and the hydrogen migration energy barrier is calculated by CI-NEB method. The higher the energy barrier, the weaker the hydrogen permeation, the smaller the hydrogen diffusion coefficient, and the lower the hydrogen permeability, thus comprehensively evaluating the overall thermal insulation and hydrogen barrier performance of the material.

[0007] Technical solution

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A low-hydrogen-permeability ytterbium-scandium co-doped gadolinium zirconate ultra-high temperature low thermal conductivity hydrogen coating material is characterized by the addition of x at% Yb and y at% Sc to a Gd2Zr2O7 matrix, wherein 2.5≤x≤15.5, 2.5≤y≤9.5, and at% represents the proportion of doped atoms in the total number of Gd, Yb, and Sc atoms.

[0010] The present invention discloses a method for preparing a low hydrogen permeability ytterbium-scandium co-doped gadolinium zirconate ultra-high temperature low thermal conductivity hydrogen coating material, the specific steps of which are as follows:

[0011] (1) Heat-treat rare earth oxide powder with a purity ≥ 99.9% to remove adsorbed water, crystal water and other volatile impurities;

[0012] (2) Mix concentrated nitric acid with deionized water to prepare diluted nitric acid; calculate and weigh the pretreated rare earth oxide powder according to the ytterbium-scandium doping ratio, add it to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh zirconium oxychloride octahydrate, dissolve it in deionized water to obtain a zirconium oxychloride solution;

[0013] (3) Mix the rare earth nitrate solution and zirconium oxychloride solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to ammonia water at a uniform rate. A white precipitate will be generated during the reaction.

[0014] (4) After the addition is complete, continue stirring to ensure the reaction is complete. Then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral. Then wash with anhydrous ethanol to replace the water and improve the powder dispersibility. Place the obtained precipitate in an oven to dry and obtain the precursor powder.

[0015] (5) The dried precursor powder was placed in a crucible and calcined to obtain crystallized ytterbium-scandium co-doped Gd2Zr2O7 powder; then it was ground and sieved to obtain powder with uniform particle size, which was directly used as raw material for coating preparation.

[0016] In preferred step (1), heat treatment is performed at 800~1000 ℃ for 2~10 h.

[0017] In preferred step (1), the rare earth oxide powder includes gadolinium oxide, ytterbium oxide and scandium oxide powder.

[0018] In the preferred step (3), the titration rate of the mixed solution is 5 mL / min or less.

[0019] In the preferred step (5), the calcination temperature is 900~1100 ℃ and the calcination time is 3~10 h.

[0020] This invention provides a low-hydrogen-permeability ytterbium-scandium co-doped Gd₂Zr₂O₇ ultra-high temperature and low thermal conductivity coating material. The dopant is denoted as x at%Yb-doped and y at%Sc-doped Gd₂Zr₂O₇, where 2.5≤x≤15.5, 2.5≤y≤9.5, and at% represents the proportion of doped atoms in the total number of Gd, Yb, and Sc atoms.

[0021] The core innovation of this invention, involving ytterbium-scandium co-doped gadolinium zirconate material, lies in the introduction of Yb and Sc into a solid solution within a Gd₂Zr₂O₇ matrix. Yb and Sc co-doping regulates the oxygen vacancy concentration and distribution within the Gd₂Zr₂O₇ lattice, inducing lattice distortion. This lattice distortion at grain boundaries acts as hydrogen trapping sites, hindering hydrogen diffusion in the bulk lattice and reducing the effective hydrogen diffusion rate, thus significantly improving high-temperature hydrogen barrier performance.

[0022] This invention also provides a method for preparing ytterbium-scandium co-doped Gd₂Zr₂O₇ ceramic powder. The method uses chemical co-precipitation and calcination to prepare ytterbium-scandium co-doped gadolinium zirconate ceramic powder. The powder prepared by this method has a small particle size and uniform distribution. The process is simple, energy-efficient, and suitable for large-scale production. To facilitate the testing of the powder's performance, the obtained powder is further pressed into shape and calcined into ceramic blocks (simulating the state after coating densification). The application potential of the powder is verified by the performance test of the blocks.

[0023] To verify the core performance of the powder, the powder was pressed into a block, and the block was calcined to obtain a dense ytterbium-scandium co-doped Gd2Zr2O7 ceramic block, which was used for subsequent high-temperature hydrogen permeability performance testing.

[0024] The sample preparation method for performance testing adopts the conventional ceramic bulk preparation process in this field, including pressing and molding, and atmospheric pressure sintering. The relevant process parameters are common parameters in this field and are used for testing and characterization.

[0025] It should be noted that the ytterbium-scandium co-doped Gd₂Zr₂O₇ powder provided by this invention is primarily used as a raw material for preparing ultra-high temperature, low thermal conductivity, and hydrogen-barrier coatings. To demonstrate its excellent potential as a coating material, the specification tests its phase stability, thermal conductivity, hydrogen permeability, and other key properties by pressing and sintering the powder into a dense ceramic block (see examples). By comparing its performance with that of Gd₂Zr₂O₇ and 12.5 at% Yb-doped Gd₂Zr₂O₇, it is demonstrated that the material of this invention has superior performance. Therefore, in application, it can simultaneously address the ultra-high temperature and hydrogen permeation challenges faced by hot-end components of engines. This is indirect and compelling evidence that this material can be used as a hydrogen-barrier coating.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. The ytterbium-scandium co-doped Gd₂Zr₂O₇ material of this invention employs dual-element synergistic doping, significantly improving its thermal insulation and hydrogen barrier capabilities. Yb doping induces lattice distortion and mass fluctuations, enhances phonon scattering, and reduces the material's thermal conductivity. Sc ions, with their small radius, reduce the oxygen vacancy concentration after doping and simultaneously induce lattice distortion, inhibiting grain growth at high temperatures, refining the grains, reducing porosity, and enhancing hydrogen barrier capabilities. This dual-element synergistic effect results in lower thermal conductivity and stronger hydrogen barrier capabilities compared to Gd₂Zr₂O₇.

[0028] 2. This invention uses a chemical coprecipitation method to prepare powders, employing water as a solvent. This eliminates the need for highly toxic chemicals, making it environmentally friendly. Furthermore, the preparation process is simple and suitable for large-scale mass production. The chemical coprecipitation method involves relatively low synthesis temperatures, primarily using common inorganic salt reagents. It is simple to operate, consumes little energy, and produces powders with small and uniform particle sizes, meeting the raw material requirements for industrial coating production. Attached Figure Description

[0029] Figure 1 XRD patterns of Gd2Zr2O7, 12.5 at% Yb-doped Gd2Zr2O7, and Gd2Zr2O7 co-doped with 11.76 at% Yb and 5.88 at% Sc.

[0030] Figure 2 XRD patterns of Gd2Zr2O7, 12.5 at% Yb-doped Gd2Zr2O7, and 11.76 at% Yb and 5.88 at% Sc co-doped Gd2Zr2O7 ceramic blocks after heat treatment at 1400 ℃ for 300 h.

[0031] Figure 3 The thermal conductivity of Gd2Zr2O7 ceramic bulk materials doped with Gd2Zr2O7, 12.5 at% Yb, and 11.76 at% Yb and 5.88 at% Sc is measured.

[0032] Figure 4 Hydrogen diffusion barrier curves for Gd2Zr2O7, 12.5 at% Yb-doped Gd2Zr2O7, and Gd2Zr2O7 co-doped with 11.76 at% Yb and 5.88 at% Sc. Detailed Implementation

[0033] The present invention will be described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. The comparative materials Gd₂Zr₂O₇ (GZO) and 12.5 at% Yb-doped Gd₂Zr₂O₇ (GYb) ceramic powder were prepared by the chemical coprecipitation method reported in the literature [WANG K, WU J, PAN L, et al. Assessment criteria for the corrosion resistance of Gd₂Zr₂O₇-based thermal barrier coatings exposed to CMAS and CMAS + sea salt[J]. npj Materials Degradation, 2026]. High-purity rare earth oxides were weighed according to the target stoichiometric ratio, dissolved in dilute nitric acid to generate nitrates, and mixed with zirconium oxychloride to prepare a mixed metal ion solution. Ammonia was used as a precipitant, and the coprecipitation reaction was completed under continuous stirring. The precipitate was centrifuged, washed, and dried to obtain a hydroxide precursor, which was then calcined at high temperature to obtain GZO and GYb ceramic powders. The two types of powders were pressed into tablets and sintered at high temperature to obtain bulk samples. Their performance was tested and compared with that of ytterbium-scandium co-doped Gd2Zr2O7.

[0034] Example 1

[0035] Using Gd₂O₃, Yb₂O₃, Sc₂O₃, and ZrOCl₂·8H₂O as raw materials, a co-doped Gd₂Zr₂O₇ (GYbSc) ceramic material with 11.76 at% Yb and 5.88 at% Sc was prepared. The steps are as follows:

[0036] (1) Gd2O3, Yb2O3 and Sc2O3 powders with a purity ≥99.9% were heat-treated at 900 °C for 4 h to remove adsorbed water, crystal water and other volatile impurities;

[0037] (2) Mix concentrated nitric acid with deionized water at a ratio of 1:1 to prepare diluted nitric acid; weigh 0.07 mol of pretreated Gd2O3 powder, 0.01 mol of Yb2O3 powder and 0.005 mol of Sc2O3 powder and add them to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh 0.16 mol of ZrOCl2·8H2O powder and dissolve it in deionized water to obtain a ZrOCl2 solution;

[0038] (3) Mix the rare earth nitrate solution and ZrOCl2 solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to the ammonia water at a rate of 3 mL / min. A white precipitate will be generated during the reaction.

[0039] (4) After the addition is complete, continue stirring for 1 h to ensure the reaction is complete, then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral (pH≈7), then wash with anhydrous ethanol. Finally, place the obtained precipitate in an oven and dry at 120 °C for 10 h to obtain the precursor powder.

[0040] (5) The dried precursor powder was placed in a crucible and calcined at 900 °C for 4 h to obtain crystallized GYbSc ceramic material. Subsequently, it was ground and sieved to obtain powder with uniform particle size, which can be directly used as raw material for the preparation of heat protection layer.

[0041] (6) The sieved powder is loaded into a mold and held under pressure of 300 MPa for 5 min to obtain a green block; the green block is placed in a high-temperature furnace and sintered at 1600 °C for 10 h in air atmosphere, and then cooled with the furnace to obtain a dense GYbSc ceramic block.

[0042] XRD patterns of GZO, GYb, and GYbSc at 20° to 85° are as follows: Figure 1 As shown, the prepared ceramic material has a single phase and a defective fluorite structure. Figure 2 and Figure 1In contrast, the diffraction peaks of GYbSc showed no change, indicating that GYbSc did not undergo a phase transition after heat treatment at 1400 ℃ for 300 h, demonstrating its excellent high-temperature phase stability; the thermal conductivity of GZO, GYb, and GYbSc is as follows: Figure 3 As shown, the thermal conductivity of GYbSc is 0.94 W·m. -1 ·K -1 Its thermal conductivity is 1.56 W·m lower than that of GZO. -1 ·K -1 And the thermal conductivity of GYb is 0.99 W·m. -1 ·K -1 Meanwhile, it is clearly visible from the figure that the thermal conductivity of GYbSc is significantly lower than that of GYb. The hydrogen diffusion barrier curves of GZO, GYb, and GYbSc are shown below. Figure 4 As shown, the hydrogen diffusion barriers of GZO, GYb, and GYbSc are 0.61 eV, 0.65 eV, and 0.89 eV, respectively. The doping of Yb and Sc effectively increases the hydrogen diffusion barrier. The increase in diffusion barrier will inhibit the long-range diffusion of hydrogen atoms and reduce the hydrogen diffusion coefficient. The hydrogen permeability decreases synchronously with the diffusion coefficient, ultimately enhancing the hydrogen barrier performance of the material.

[0043] Example 2

[0044] Using Gd₂O₃, Yb₂O₃, Sc₂O₃, and ZrOCl₂·8H₂O as raw materials, a Gd₂Zr₂O₇ (GYbSc₁) ceramic material with 9.09 at% Yb and 3.03 at% Sc was prepared. The steps are as follows:

[0045] (1) Gd2O3, Yb2O3 and Sc2O3 powders with a purity ≥99.9% were heat-treated at 800 °C for 10 h to remove adsorbed water, crystal water and other volatile impurities;

[0046] (2) Mix concentrated nitric acid and deionized water in a 1:1 ratio to prepare diluted nitric acid; weigh 0.0725 mol of pretreated Gd2O3 powder, 0.0075 mol of Yb2O3 powder and 0.0025 mol of Sc2O3 powder and add them to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh 0.16 mol of ZrOCl2·8H2O powder and dissolve it in deionized water to obtain a ZrOCl2 solution;

[0047] (3) Mix the rare earth nitrate solution and ZrOCl2 solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to the ammonia water at a rate of 3 mL / min. A white precipitate will be generated during the reaction.

[0048] (4) After the addition is complete, continue stirring for 1 h to ensure the reaction is complete, then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral (pH≈7), then wash with anhydrous ethanol. Finally, place the obtained precipitate in an oven and dry at 120 °C for 10 h to obtain the precursor powder.

[0049] (5) The dried precursor powder was placed in a crucible and calcined at 1000 °C for 10 h to obtain crystallized GYbSc1 ceramic material. Subsequently, it was ground and sieved to obtain powder with uniform particle size, which can be directly used as raw material for the preparation of heat protection layer.

[0050] (6) The sieved powder is loaded into a mold and held under pressure of 300 MPa for 5 min to obtain a green block; the green block is placed in a high-temperature furnace and sintered at 1600 °C for 10 h in air atmosphere, and then cooled with the furnace to obtain a dense GYbSc1 ceramic block.

[0051] GYbSc1 exhibits a defective fluorite structure. After heat treatment at 1400 ℃ for 300 h, the sample showed no phase transformation, demonstrating excellent high-temperature phase stability. The thermal conductivity of GYbSc1 is 1.01 W·m. -1 ·K -1 It is far lower than GZO's 1.56 W·m -1 ·K -1 Slightly greater than 0.99 W·m of GYb -1 ·K -1 The hydrogen diffusion barrier of GYbSc1 is 0.66 eV, which is greater than that of GZO and GYb. It also has a smaller hydrogen diffusion coefficient, lower hydrogen permeability, and stronger hydrogen barrier performance.

[0052] Example 3

[0053] Using Gd₂O₃, Yb₂O₃, Sc₂O₃, and ZrOCl₂·8H₂O as raw materials, a 5.88 at% Yb and 5.88 at% Sc co-doped Gd₂Zr₂O₇ (GYbSc₂) ceramic material was prepared. The steps are as follows:

[0054] (1) Gd2O3, Yb2O3 and Sc2O3 powders with a purity ≥99.9% were heat-treated at 1000 °C for 2 h to remove adsorbed water, crystal water and other volatile impurities;

[0055] (2) Mix concentrated nitric acid with deionized water at a ratio of 1:1 to prepare diluted nitric acid; weigh 0.075 mol of pretreated Gd2O3 powder, 0.005 mol of Yb2O3 powder and 0.005 mol of Sc2O3 powder and add them to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh 0.16 mol of ZrOCl2·8H2O powder and dissolve it in deionized water to obtain a ZrOCl2 solution;

[0056] (3) Mix the rare earth nitrate solution and ZrOCl2 solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to the ammonia water at a rate of 3 mL / min. A white precipitate will be generated during the reaction.

[0057] (4) After the addition is complete, continue stirring for 1 h to ensure the reaction is complete, then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral (pH≈7), then wash with anhydrous ethanol. Finally, place the obtained precipitate in an oven and dry at 120 °C for 10 h to obtain the precursor powder.

[0058] (5) The dried precursor powder was placed in a crucible and calcined at 1100 °C for 3 h to obtain crystallized GYbSc2 ceramic material. Subsequently, it was ground and sieved to obtain powder with uniform particle size, which can be directly used as raw material for the preparation of heat protection layer.

[0059] (6) The sieved powder is loaded into a mold and held under pressure of 300 MPa for 5 min to obtain a green block; the green block is placed in a high-temperature furnace and sintered at 1600 °C for 10 h in air atmosphere, and then cooled with the furnace to obtain a dense GYbSc2 ceramic block.

[0060] GYbSc2 exhibits a defective fluorite structure. After heat treatment at 1400 ℃ for 300 h, the sample showed no phase transformation, demonstrating excellent high-temperature phase stability. The thermal conductivity of GYbSc2 is 1.08 W·m. -1 ·K -1 It is far lower than the 1.56 W·m of gadolinium zirconate. -1 ·K -1 Slightly higher than GYb at 0.99 W·m -1 ·K -1 The hydrogen diffusion barrier of GYbSc2 is 0.77 eV, which is greater than that of GZO and GYb. It also has a smaller hydrogen diffusion coefficient, lower hydrogen permeability, and stronger hydrogen barrier performance.

[0061] Example 4

[0062] Using Gd₂O₃, Yb₂O₃, Sc₂O₃, and ZrOCl₂·8H₂O as raw materials, a co-doped Gd₂Zr₂O₇ (GYbSc₃) ceramic material with 2.94 at% Yb and 8.82 at% Sc was prepared. The steps are as follows:

[0063] (1) Gd2O3, Yb2O3 and Sc2O3 powders with a purity ≥99.9% were heat-treated at 800 °C for 10 h to remove adsorbed water, crystal water and other volatile impurities;

[0064] (2) Mix concentrated nitric acid and deionized water in a 1:1 ratio to prepare diluted nitric acid; weigh 0.075 mol of pretreated Gd2O3 powder, 0.0025 mol of Yb2O3 powder and 0.0075 mol of Sc2O3 powder and add them to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh 0.16 mol of ZrOCl2·8H2O powder and dissolve it in deionized water to obtain a ZrOCl2 solution;

[0065] (3) Mix the rare earth nitrate solution and ZrOCl2 solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to the ammonia water at a rate of 3 mL / min. A white precipitate will be generated during the reaction.

[0066] (4) After the addition is complete, continue stirring for 1 h to ensure the reaction is complete, then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral (pH≈7), then wash with anhydrous ethanol. Finally, place the obtained precipitate in an oven and dry at 120 °C for 10 h to obtain the precursor powder.

[0067] (5) The dried precursor powder was placed in a crucible and calcined at 900 °C for 8 h to obtain crystallized GYbSc3 ceramic material. Subsequently, it was ground and sieved to obtain powder with uniform particle size, which can be directly used as raw material for the preparation of heat protection layer.

[0068] (6) The sieved powder is loaded into a mold and held under pressure of 300 MPa for 5 min to obtain a green block; the green block is placed in a high-temperature furnace and sintered at 1600 ℃ for 10 h in air atmosphere, and then cooled with the furnace to obtain a dense GYbSc3 ceramic block.

[0069] GYbSc3 exhibits a defective fluorite structure. After heat treatment at 1400 ℃ for 300 h, the sample showed no phase transformation, demonstrating excellent high-temperature phase stability. The thermal conductivity of GYbSc3 is 1.12 W·m. -1 ·K -1 It is far lower than the 1.56 W·m of gadolinium zirconate. -1 ·K -1Slightly higher than GYb at 0.99 W·m -1 ·K -1 The hydrogen diffusion barrier of GYbSc3 is 0.83 eV, which is greater than that of GZO and GYb. It also has a smaller hydrogen diffusion coefficient, lower hydrogen permeability, and stronger hydrogen barrier performance.

[0070] Example 5

[0071] Using Gd₂O₃, Yb₂O₃, Sc₂O₃, and ZrOCl₂·8H₂O as raw materials, a co-doped Gd₂Zr₂O₇ (GYbSc₄) ceramic material with 3.03 at% Yb and 9.09 at% Sc was prepared. The steps are as follows:

[0072] (1) Gd2O3, Yb2O3 and Sc2O3 powders with a purity ≥99.9% were heat-treated at 900 °C for 6 h to remove adsorbed water, crystal water and other volatile impurities;

[0073] (2) Mix concentrated nitric acid and deionized water in a 1:1 ratio to prepare diluted nitric acid; weigh 0.0725 mol of pretreated Gd2O3 powder, 0.0025 mol of Yb2O3 powder and 0.0075 mol of Sc2O3 powder and add them to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh 0.16 mol of ZrOCl2·8H2O powder and dissolve it in deionized water to obtain a ZrOCl2 solution;

[0074] (3) Mix the rare earth nitrate solution and ZrOCl2 solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to the ammonia water at a rate of 3 mL / min. A white precipitate will be generated during the reaction.

[0075] (4) After the addition is complete, continue stirring for 1 h to ensure the reaction is complete, then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral (pH≈7), then wash with anhydrous ethanol. Finally, place the obtained precipitate in an oven and dry at 120 °C for 10 h to obtain the precursor powder.

[0076] (5) The dried precursor powder was placed in a crucible and calcined at 1000 °C for 4 h to obtain crystallized GYbSc4 ceramic material. Subsequently, it was ground and sieved to obtain powder with uniform particle size, which can be directly used as raw material for the preparation of heat protection layer.

[0077] (6) The sieved powder is loaded into a mold and held under pressure of 300 MPa for 5 min to obtain a green block; the green block is placed in a high-temperature furnace and sintered at 1600 °C for 10 h in air atmosphere, and then cooled with the furnace to obtain a dense GYbSc4 ceramic block.

[0078] GYbSc4 exhibits a defective fluorite structure. After heat treatment at 1400 ℃ for 300 h, the sample showed no phase transformation, demonstrating excellent high-temperature phase stability. The thermal conductivity of GYbSc4 is 1.15 W·m. -1 ·K -1 It is far lower than the 1.56 W·m of gadolinium zirconate. -1 ·K -1 Slightly higher than GYb at 0.99 W·m -1 ·K -1 The hydrogen diffusion barrier of GYbSc4 is 0.87 eV, which is greater than that of GZO and GYb. It also has a smaller hydrogen diffusion coefficient, lower hydrogen permeability, and stronger hydrogen barrier performance.

[0079] Example 6

[0080] Using Gd₂O₃, Yb₂O₃, Sc₂O₃, and ZrOCl₂·8H₂O as raw materials, a co-doped Gd₂Zr₂O₇ (GYbSc₄) ceramic material with 12.5 at% Yb and 6.25 at% Sc was prepared. The steps are as follows:

[0081] (1) Gd2O3, Yb2O3 and Sc2O3 powders with a purity ≥99.9% were heat-treated at 900 °C for 8 h to remove adsorbed water, crystal water and other volatile impurities;

[0082] (2) Mix concentrated nitric acid and deionized water in a 1:1 ratio to prepare diluted nitric acid; weigh 0.065 mol of pretreated Gd2O3 powder, 0.01 mol of Yb2O3 powder and 0.005 mol of Sc2O3 powder and add them to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh 0.16 mol of ZrOCl2·8H2O powder and dissolve it in deionized water to obtain a ZrOCl2 solution;

[0083] (3) Mix the rare earth nitrate solution and ZrOCl2 solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to the ammonia water at a rate of 3 mL / min. A white precipitate will be generated during the reaction.

[0084] (4) After the addition is complete, continue stirring for 1 h to ensure the reaction is complete, then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral (pH≈7), then wash with anhydrous ethanol. Finally, place the obtained precipitate in an oven and dry at 120 °C for 10 h to obtain the precursor powder.

[0085] (5) The dried precursor powder was placed in a crucible and calcined at 1100 °C for 4 h to obtain crystallized GYbSc4 ceramic material. Subsequently, it was ground and sieved to obtain powder with uniform particle size, which can be directly used as raw material for the preparation of heat protection layer.

[0086] (6) The sieved powder is loaded into a mold and held under pressure of 300 MPa for 5 min to obtain a green block; the green block is placed in a high-temperature furnace and sintered at 1600 °C for 10 h in air atmosphere, and then cooled with the furnace to obtain a dense GYbSc4 ceramic block.

[0087] GYbSc4 exhibits a defective fluorite structure. After heat treatment at 1400 ℃ for 300 h, the sample showed no phase transformation, demonstrating excellent high-temperature phase stability. The thermal conductivity of GYbSc4 is 1.01 W·m. -1 ·K -1 It is far lower than the 1.56 W·m of gadolinium zirconate. -1 ·K -1 Slightly higher than GYb at 0.99 W·m -1 ·K -1 The hydrogen diffusion barrier of GYbSc4 is 0.84 eV, which is greater than that of GZO and GYb. It also has a smaller hydrogen diffusion coefficient, lower hydrogen permeability, and stronger hydrogen barrier performance.

[0088] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A low-hydrogen-permeability ytterbium-scandium co-doped gadolinium zirconate ultra-high temperature low thermal conductivity hydrogen coating material, characterized in that, x at% Yb and y at% Sc are doped into the Gd2Zr2O7 matrix, where 2.5≤x≤15.5, 2.5≤y≤9.5, and at% represents the proportion of the doped atom in the total number of Gd, Yb, and Sc atoms.

2. The preparation method of the low hydrogen permeability ytterbium-scandium co-doped gadolinium zirconate ultra-high temperature low thermal conductivity hydrogen coating material according to claim 1, the specific steps are as follows: (1) Heat-treat rare earth oxide powder with a purity ≥ 99.9% to remove adsorbed water, crystal water and other volatile impurities; (2) Mix concentrated nitric acid with deionized water to prepare diluted nitric acid; calculate and weigh the pretreated rare earth oxide powder according to the ytterbium-scandium doping ratio, add it to the diluted nitric acid, heat and stir until completely dissolved to obtain a rare earth nitrate solution; weigh zirconium oxychloride octahydrate, dissolve it in deionized water to obtain a zirconium oxychloride solution; (3) Mix the rare earth nitrate solution and zirconium oxychloride solution evenly, and use ammonia water as a precipitant. Under continuous mechanical stirring, add the mixed solution dropwise to ammonia water at a uniform rate. A white precipitate will be generated during the reaction. (4) After the addition is complete, continue stirring to ensure the reaction is complete. Then filter and collect the white precipitate. Wash the precipitate repeatedly with deionized water until the filtrate is neutral. Then wash with anhydrous ethanol to replace the water and improve the powder dispersibility. Place the obtained precipitate in an oven to dry and obtain the precursor powder. (5) The dried precursor powder was placed in a crucible and calcined to obtain crystallized ytterbium-scandium co-doped Gd2Zr2O7 powder; then it was ground and sieved to obtain powder with uniform particle size, which was directly used as raw material for coating preparation.

3. The preparation method according to claim 2, characterized in that, In step (1), heat treatment is carried out at 800~1000 ℃ for 2~10h.

4. The preparation method according to claim 2, characterized in that, In step (1), the rare earth oxide powder includes gadolinium oxide, ytterbium oxide and scandium oxide powder.

5. The preparation method according to claim 2, characterized in that, In step (3), the titration rate of the mixed solution is 5 mL / min or less.

6. The preparation method according to claim 2, characterized in that, In step (5), the calcination temperature is 900~1100 ℃ and the calcination time is 3~10 h.

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