High-entropy rare earth oxide diffusion-resistant layer material for refractory metal and preparation method of high-entropy rare earth oxide diffusion-resistant layer material

Abstract

The invention discloses a high-entropy rare earth oxide diffusion-resistant layer material for refractory metal and a preparation method thereof, the high-entropy rare earth oxide (Dy0. 2Ho0. 2Er0. 2Tm0. 2Yb0. 2) 2O3 powder with ultrafine grains and a porous communication structure is prepared by using multi-component soluble salts of Dy, Ho, Er, Tm and Yb as raw materials through a liquid-phase combustion driving reaction, the powder is prepared into slurry, the slurry is spin-coated on the surface of a Mo or Nb matrix to form a diffusion-resistant layer, and the diffusion-resistant layer material is prepared into a high-entropy rare earth oxide (Dy0. 2Ho0. 2Er0. 2Tm0. 2Yb0. 2). And finally, synchronous spark plasma sintering is carried out on the base body, the diffusion-resistant layer and the coating, so that compact solid phase combination is achieved, and an integrated double-layer protection structure is constructed. The prepared diffusion-resistant layer has ultra-fine grains and structural thermal stability, the deep diffusion of the Si element in the outer layer coating to the refractory metal matrix at the temperature of 1600 DEG C can be remarkably inhibited, silicification embrittlement, matrix pulverization and structural failure are effectively avoided, and the diffusion-resistant layer has the advantages that the diffusion-resistant performance is good; the invention provides a refractory metal surface long-term protection technology which is controllable in structure, stable in interface and suitable for an extreme high-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of surface protection technology for high-temperature structural materials, specifically to a high-entropy rare earth oxide diffusion barrier layer material for refractory metals and its preparation method. Background Technology

[0002] Refractory metals (Mo, Nb, Ta, W, Re, etc.) and their alloys possess advantages such as high melting point, high high-temperature strength, good resistance to liquid metal corrosion, plasticity, and good machinability, making them important high-temperature structural materials in the aerospace and nuclear industries. However, refractory metals and their alloys are extremely prone to oxidation at high temperatures (above 700°C), severely damaging the high-temperature properties of the materials. Therefore, effective high-temperature oxidation protection is essential. Antioxidant coatings are a widely used technology for protecting refractory metals from oxidation. Among them, MoSi2-based multiphase ceramic coatings (such as MoSi2-SiC, MoSi2-ZrSi2, and MoSi2-HfSi2) have good film-forming properties, excellent antioxidation performance, and a thermal expansion coefficient similar to that of the refractory metal matrix. They can provide good long-term high-temperature oxidation protection for the matrix in the temperature range of 1400-1600℃. However, a large amount of free Si elements are generated during the preparation and service of MoSi2-based multiphase ceramic coatings at high temperatures of 1400-1600℃. The generated Si elements will rapidly diffuse into the refractory metal matrix, resulting in silanization embrittlement, pulverization, and structural failure of the matrix.

[0003] Introducing a diffusion barrier layer between a refractory metal matrix and a MoSi2-based multiphase ceramic coating can effectively suppress the excessive diffusion of Si into the matrix, thereby improving the oxidation protection performance of the coating. Reference 1, “YQQiao, T.Chen, XPGuo, Diffusion barrier effect of Al2O3 layer at the interface between Mo-Si-Bcoating and Nb-Si based alloy. Corrosion Communications, 2021, 4:45-46,” discloses a MoSi2-based multiphase ceramic coating with a single-phase Al2O3 diffusion barrier layer on the surface of an Nb-Si based alloy. This coating provides good high-temperature oxidation protection for the Nb-Si based alloy, and the Al2O3 diffusion barrier layer effectively suppresses the diffusion of Si into the substrate. Reference 2, "H.Jiang, YQQiao, XPGuo et al, Effect of Al2O3-SiO2 film at the interface on the microstructure formation and oxidation resistance of MoSi2 coating on Nb-Si based alloy via slurry sintering method. Journal of Alloy and Compounds. 2025, 1010: 177720," discloses a MoSi2-based multiphase ceramic coating with an Al2O3-SiO2 dual-phase diffusion barrier layer on the surface of the refractory metal Nb. This coating can provide good high-temperature oxidation protection for the Nb substrate. The introduced Al2O3-SiO2 dual-phase diffusion barrier layer not only effectively inhibits the excessive diffusion of Si into the Nb substrate, but also improves the density of the MoSi2 outer layer, greatly enhancing the high-temperature oxidation protection performance of the substrate.

[0004] Currently, the main materials used for resisting diffusion layers on refractory metal surfaces are oxides such as Al2O3 and SiO2, which are prepared through processes such as slurry preparation, magnetron sputtering, and in-situ reaction. However, the reported resisting diffusion layers on refractory metal surfaces have limited effect on inhibiting Si penetration. After the coating is put into service, a small amount of Si still diffuses into the substrate. Furthermore, the existing resisting diffusion layers still have significant shortcomings in terms of matching thermal expansion coefficients, thermal shock resistance, diffusion blocking efficiency, and ultra-high temperature structural stability. It is difficult to effectively inhibit the deep penetration of free Si in MoSi2-based coatings into the refractory metal matrix for a long time at 1400-1600℃.

[0005] In recent years, high-entropy rare-earth oxides have attracted widespread attention in the field of high-temperature structural materials due to their combined high entropy mixing effect, lattice distortion effect, slow diffusion effect, and rich tunable defect chemistry. Compared with single-component Al2O3 or SiO2 diffusion barrier layers, high-entropy rare-earth oxides exhibit significant advantages in thermal property matching, phase stability, and diffusion blocking ability. Therefore, it is of great significance to develop a novel diffusion barrier material that simultaneously possesses a high-entropy solid solution structure, ultrafine-grained porous morphology, good thermal expansion matching with refractory metal matrices, and the ability to stably block Si diffusion under ultra-high temperature environments. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-entropy rare earth oxide diffusion barrier layer material for refractory metals and its preparation method, thereby solving the problem that existing MoSi2-based ceramic coatings easily generate a large amount of free Si elements under high temperature conditions of 1400–1600℃. The generated Si elements will rapidly diffuse into the refractory metal matrix, leading to silicification, embrittlement, pulverization, and structural failure of the matrix.

[0007] The technical solution provided by this invention is as follows:

[0008] This invention provides a method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals, characterized by comprising the following steps:

[0009] ①. Preparation of precursor solution

[0010] Metal nitrates Dy(NO3)3·5H2O, Ho(NO3)3·5H2O, Er(NO3)3·5H2O, Tm(NO3)3·5H2O and Yb(NO3)3·5H2O are dissolved in deionized water, and then fuel is added and mixed evenly to form a precursor solution.

[0011] ②. Preparation of high-entropy rare earth oxide diffusion barrier layer materials by liquid-phase combustion driven reaction

[0012] The precursor solution obtained in step ① was heated and stirred at 80–130°C until it reached a colloidal state. It was then transferred to a furnace filled with inert gas and held at 300–700°C until a liquid-phase combustion-driven reaction occurred, yielding ultrafine-grained porous (Dy) materials. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder, that is, to prepare a high-entropy rare earth oxide diffusion barrier layer material.

[0013] Furthermore, in step S1, the total molar ratio of fuel to metal nitrate is (1.25-3.75):1, and the molar amounts of Dy(NO3)3·5H2O, Ho(NO3)3·5H2O, Er(NO3)3·5H2O, Tm(NO3)3·5H2O and Yb(NO3)3·5H2O are equal.

[0014] Furthermore, in step S1, the fuel is selected from at least one of glycine, urea, and ethylenediaminetetraacetic acid.

[0015] Furthermore, by controlling the fuel composition, the molar ratio of fuel to metal nitrate, and the liquid-phase combustion-driven reaction time and temperature, the prepared high-entropy rare earth oxide diffusion barrier layer material can have a sponge-like porous structure composed of irregular nanoparticles or a porous structure composed of stacked short columnar nanoparticles.

[0016] Based on the same inventive concept, this invention provides a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals, prepared by any of the above-mentioned methods for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals. The chemical composition of the high-entropy rare-earth oxide diffusion barrier layer material is (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3, with a grain size of 10-70nm.

[0017] Based on the same inventive concept, this invention provides a method for preparing a double-layer protective structure for refractory metals, comprising the following steps:

[0018] (1) Preparation of diffusion barrier layer

[0019] The organic binder and solvent are mixed and heated and stirred until a transparent colloid is formed. The above-mentioned high entropy rare earth oxide diffusion barrier layer material and the transparent colloid are then mixed at a mass ratio of (1-1.5):2 to form a slurry. The slurry is then applied to the surface of a refractory metal substrate by spin coating to form a diffusion barrier layer.

[0020] (2) Preparation of MoSi2-SiC coating

[0021] MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and then pressed with a mold to form a MoSi2-SiC coating, which was then applied to the surface of the diffusion barrier layer.

[0022] (3) Preparation of double-layer protective structure

[0023] A refractory metal substrate with a diffusion barrier layer and a MoSi2-SiC coating is subjected to spark plasma sintering to solidify the refractory metal substrate, the diffusion barrier layer, and the MoSi2-SiC coating, thus preparing a double-layer protective structure.

[0024] Furthermore, in step (1), the organic binder is selected from at least one of polybutyl acrylate or polyvinyl butyral, and the solvent is selected from at least one of butanol or diethylene glycol monobutyl ether, with a mass ratio of organic binder to solvent of 1:9.

[0025] Furthermore, in step (1), the refractory metal matrix is ​​Nb or Mo.

[0026] Furthermore, the thickness of the diffusion barrier layer in step (1) is 0.35-0.75 mm, and the thickness of the MoSi2-SiC coating in step (2) is 50-300 μm.

[0027] Furthermore, in step (3), the temperature of the discharge plasma sintering is 1300-1700℃, the heating rate is 50-200℃ / min, and the holding time is 3-20min.

[0028] Based on the same inventive concept, the present invention provides a double-layer protective structure for refractory metals, which is prepared by any of the above-mentioned methods for preparing a double-layer protective structure for refractory metals.

[0029] The beneficial effects of this invention are:

[0030] 1. This invention uses liquid-phase combustion-driven reaction to prepare ultrafine-grained porous high-entropy rare earth oxide powder. The entire reaction is completed within 1 to 3 seconds, which has the advantages of fast reaction speed, high energy utilization rate and strong structural controllability. During the liquid-phase combustion process, rapid exothermic reaction and release of a large amount of gas form a transient high temperature and strong turbulent environment, which can simultaneously complete the rapid solid-phase mixing of multiple components and the generation of uniform crystal nuclei at the nanoscale. As a result, the obtained ultrafine-grained porous high-entropy rare earth oxide powder has the structural characteristics of small grain size (below 40 nm) and good pore connectivity.

[0031] 2. The liquid-phase combustion-driven reaction method avoids the long-term diffusion limitations of traditional solid-phase reactions and the component segregation that may occur in sol-gel processes. This allows high-entropy rare earth oxide powders to form a stable multi-component solid solution structure in a one-step reaction, which is beneficial for the subsequent formation of a dense and continuous diffusion-blocking layer. In addition, the liquid-phase combustion-driven reaction is highly sensitive to the composition of the precursor and the fuel ratio. By adjusting the parameters, it is possible to design and construct different morphologies such as sheet-like or particulate aggregates, giving it the significant advantages of both process simplification and structural engineering.

[0032] 3. The high-entropy rare-earth oxide diffusion barrier layer prepared in this invention relies on a multi-component solid solution structure of Dy, Ho, Er, Tm, and Yb, exhibiting high mixing entropy, high defect concentration, and low diffusion driving force. It demonstrates excellent microstructural stability and chemical inertness at high temperatures. The high melting point and low oxidation reactivity of the multi-component rare-earth oxides enable them to maintain phase composition stability at 1600℃, while the high-entropy effect significantly enhances the energy barrier for grain growth and phase decomposition, making it difficult for the diffusion barrier layer to undergo grain coarsening and structural collapse. The ultrafine grains and porous interconnected framework together form a tortuous multi-level diffusion path, significantly extending the Si element migration path and reducing the diffusion flux.

[0033] 4. The high-entropy rare earth oxide (Dy) prepared by this invention 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The coefficient of thermal expansion of O₂ is 7.3–8.1 × 10⁻⁶. -6 K -1 It exhibits good thermal expansion matching with Nb or Mo matrices (the thermal expansion coefficient of the Mo matrix is ​​5.0–5.8 × 10⁻⁶). -6 K -1 The coefficient of thermal expansion of the Nb matrix is ​​7.0–7.5 × 10⁻⁶. -6 K -1 It can effectively reduce interfacial stress during thermal cycling, enabling the diffusion barrier layer to maintain its integrity and density under long-term service conditions, and has the function of achieving both high-temperature stability and diffusion barrier that is difficult to achieve simultaneously in traditional ceramic systems. Attached Figure Description

[0034] Figure 1 (a) The (Dy) prepared in Examples 1 and 2 of this invention 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 X-ray diffraction pattern of 2O3 powder, where S1 is the sponge-like porous (Dy) powder composed of irregular nanoparticles prepared in Example 1 of this invention. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 S2 is a porous (Dy) powder composed of short columnar nanoparticles prepared in Example 2 of this invention. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder; Figure 1(b) A porous (Dy) nanoparticle-based material prepared according to Example 2 of the present invention, consisting of stacked short columnar nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 XRD slow scan refinement image of )2O3 powder (S2).

[0035] Figure 2 (a) A sponge-like porous structure composed of irregular nanoparticles prepared in Example 1 (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 Low-magnification FE-SEM of O2 powder, Figure 2 (b) A sponge-like porous structure composed of irregular nanoparticles prepared in Example 1 (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 High-magnification FE-SEM of O2 powder; Figure 2 (c) A porous (Dy) material prepared in Example 2, consisting of stacked short columnar nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 Low-magnification FE-SEM of O2 powder, Figure 2 (d) shows the porous (Dy) material prepared in Example 2, composed of stacked short columnar nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 High-magnification FE-SEM of 2O3 powder.

[0036] Figure 3 The porous (Dy) nanoparticles prepared in this invention are composed of stacked short columnar nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 (a) TEM image (inset is SAD image) and energy spectrum distribution of )2O3 powder (S2), (b) HRTEM image.

[0037] Figure 4 The SEM images and energy dispersive spectroscopy distributions of the S1 powder prepared in this invention as a diffusion barrier layer for Nb matrix after oxidation at 1600℃ for 100h are shown.

[0038] Figure 5The SEM images and energy dispersive spectroscopy distributions of the S2 powder prepared in this invention as a diffusion barrier layer on a Nb matrix after oxidation at 1600℃ for 100 h are shown.

[0039] Figure 6 The SEM images and energy dispersive spectroscopy distributions of the S1 powder prepared in this invention as a diffusion barrier layer on a Mo matrix after oxidation at 1600℃ for 100 h are shown.

[0040] Figure 7 SEM images and energy dispersive spectroscopy distribution of the S2 powder prepared in this invention as a diffusion barrier layer on a Mo matrix after oxidation at 1600℃ for 100 h.

[0041] Figure 8 SEM image and energy spectrum distribution of the Nb matrix without diffusion barrier layer prepared for Comparative Example 1 after oxidation at 1600℃ for 100h.

[0042] Figure 9 SEM image and energy spectrum distribution of the Mo matrix without diffusion barrier layer prepared for Comparative Example 2 after oxidation at 1600℃ for 100h. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. It should be noted that, unless otherwise specified, all chemical reagents involved in this invention are purchased through commercial channels.

[0044] Polybutyl acrylate (CAS No.: 9003-49-0), item number: P767446, molecular weight: ~80kDa, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Polyvinyl butyral (CAS No.: 63148-65-2), item number: B501389, molecular weight: 120,000~150,000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0045] Example 1:

[0046] A method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals includes the following steps:

[0047] ①. Preparation of precursor solution

[0048] Dissolve 0.8771g of Dy(NO3)3·5H2O, 0.8820g of Ho(NO3)3·5H2O, 0.8867g of Er(NO3)3·5H2O, 0.8901g of Tm(NO3)3·5H2O and 0.8983g of Yb(NO3)3·5H2O in 20ml of deionized water, then add 0.37g of urea and 2.32g of ethylenediaminetetraacetic acid, and mix well to form a precursor solution;

[0049] ②. Preparation of high-entropy rare earth oxide diffusion barrier layer materials by liquid-phase combustion driven reaction

[0050] The precursor solution obtained in step ① was heated at 100°C for 12 min using a magnetic stirrer until it reached a colloidal state. It was then transferred to a furnace filled with N2 atmosphere and held at 600°C for 8 min until a liquid-phase combustion-driven reaction occurred, yielding a sponge-like porous (Dy) structure composed of irregular nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder (S1) is used to prepare a high-entropy rare earth oxide diffusion barrier layer material.

[0051] Figure 1 In (a), S1 is the porous (Dy) material prepared in Example 1. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The X-ray diffraction pattern of the 2O3 powder shows that the synthesized sample S1 has good crystallinity. Based on this pattern and the Scherrer formula, the average grain size is calculated to be 39.1 nm.

[0052] Figure 2 (a) is a sponge-like porous structure composed of irregular nanoparticles (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 Low-magnification FE-SEM of 2O3 powder (S1) Figure 2 (b) is a sponge-like porous structure composed of irregular nanoparticles (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2The high-magnification FE-SEM of 2O3 powder (S1) shows that S1 powder is a sponge-like porous structure composed of irregular nanoparticles with well-developed pores and looser interparticle bonding. Due to its higher defect density and larger specific surface area, this type of structure is more likely to form a continuous and dense three-dimensional skeleton during spin coating and sintering, and has a stronger bending and elongation effect on the diffusion path of Si.

[0053] A method for preparing a double-layer protective structure for refractory metals includes the following steps:

[0054] (1) Preparation of diffusion barrier layer

[0055] Polybutyl acrylate and butanol were mixed at a mass ratio of 1:9 and heated to 60°C, then stirred until a transparent colloid was formed. The (Dy) prepared above was then added... 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder and transparent colloid were mixed at a mass ratio of 1.2:2 to prepare a slurry, and the slurry was applied to the surface of Nb substrate by spin coating at a spin coating speed of 1500 rpm to form a diffusion barrier layer, with the thickness of the resulting diffusion barrier layer controlled at about 0.4 mm.

[0056] (2) Preparation of MoSi2-SiC coating

[0057] MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and then a MoSi2-SiC coating with a thickness of about 150 μm was formed by pressing with a mold and covering the surface of the diffusion barrier layer.

[0058] (3) Preparation of double-layer protective structure

[0059] A sandwich structure of Nb matrix with diffusion barrier layer and MoSi2-SiC coating is placed in an SPS device and heated at a rate of 100℃ / min. It is then held at 1500℃ and 40MPa for 10 min to achieve solid-phase bonding, so that Nb matrix / diffusion barrier layer / antioxidant coating form an integral structure, thus preparing a double-layer protective structure for refractory metals.

[0060] Figure 4SEM images and energy dispersive spectroscopy (EDS) of the S1 powder prepared in this embodiment as a diffusion barrier layer for Nb matrix after oxidation at 1600℃ for 100 h (outer layer is MoSi2-SiC) were obtained. Cross-sectional SEM observation showed that the diffusion barrier layer had an intact structure without through cracks. The diffusion depth of free Si in the upper anti-oxidation coating into the Nb matrix was significantly hindered, and the diffusion layer thickness was only 10.91 μm. The interface was intact, and the Nb matrix did not show silanization embrittlement. A continuous and dense solid-state metallurgical interface was formed between the diffusion barrier layer and the matrix. The diffusion barrier layer maintained a three-dimensional skeleton-like pore-wall structure, but the whole structure was densified. Mechanical locking and local metallurgical diffusion coupling were formed between the upper MoSi2-SiC coating and the diffusion barrier layer. There were no debonding, pores, or unsintered areas at the interface.

[0061] Example 2:

[0062] A method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals includes the following steps:

[0063] ①. Preparation of precursor solution

[0064] Dissolve 0.8771g of Dy(NO3)3·5H2O, 0.8820g of Ho(NO3)3·5H2O, 0.8867g of Er(NO3)3·5H2O, 0.8901g of Tm(NO3)3·5H2O and 0.8983g of Yb(NO3)3·5H2O in 20ml of deionized water, then add 0.75g of urea and 0.94g of glycine, and mix well to form a precursor solution;

[0065] ②. Preparation of high-entropy rare earth oxide diffusion barrier layer materials by liquid-phase combustion driven reaction

[0066] The precursor solution obtained in step ① was heated at 80°C for 10 min using a magnetic stirrer until it reached a colloidal state. It was then transferred to a furnace filled with N2 atmosphere and held at 500°C for 10 min until a liquid-phase combustion-driven reaction occurred, yielding a porous (Dy) structure composed of stacked short columnar nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The high-entropy rare earth oxide diffusion barrier layer material was prepared by using 2O3 powder (S2).

[0067] Figure 1 In (a), S2 is the porous (Dy) material prepared in Example 2. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2The X-ray diffraction pattern of S2O3 powder shows that the synthesized sample S2 has good crystallinity. Based on this pattern and the Scherrer formula, the average grain size is calculated to be 34.9 nm. Figure 1 (b) Porous (Dy) material prepared in Example 2 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The refined XRD pattern of the 2O3 powder shows that the synthesized powder is a single crystal phase, which is a typical NaCl type structure, without other impurities, indicating that the high entropy rare earth oxide powder prepared by the liquid-phase combustion-driven reaction method is pure.

[0068] Figure 2 (c) is a porous structure composed of stacked short columnar nanoparticles (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 Low-magnification FE-SEM of 2O3 powder (S2), Figure 2 (d) is a porous structure composed of stacked short columnar nanoparticles (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The high-magnification FE-SEM image of S2O3 powder (S2) shows that the S2 powder has a porous structure of short columnar nanoparticles with a large number of micropores between the particles. This is beneficial for forming good wettability and mechanical interlocking during spin coating, and improves the density of the diffusion barrier layer and the interfacial adhesion.

[0069] Figure 3 The porous (Dy) nanoparticles prepared in this embodiment are composed of stacked short columnar nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The TEM image and energy dispersive spectroscopy (EDS) distribution of S2O3 powder (inset: SAD image) and HRTEM image (b) show that the average grain size is mostly around 32.7 nm, consistent with the "fine particle and hierarchical pore" structure observed by FE-SEM. The annular diffraction spot (SAD) indicates a solid solution-type single-phase cubic structure, and no two-phase precipitation was observed, indicating that the liquid-phase combustion-driven reaction can achieve highly uniform solid solution of multi-component cations. The EDS distribution results show that Dy, Ho, Er, Tm, and Yb elements are uniformly distributed.

[0070] A method for preparing a double-layer protective structure for refractory metals includes the following steps:

[0071] (1) Preparation of diffusion barrier layer

[0072] Polybutyl acrylate and butanol were mixed at a mass ratio of 1:9 and heated to 60°C, then stirred until a transparent colloid was obtained. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder and transparent colloid were mixed at a mass ratio of 1.2:2 to prepare a slurry, and the slurry was applied to the surface of Nb substrate by spin coating at a spin coating speed of 1500 rpm to form a diffusion barrier layer, with the thickness of the resulting diffusion barrier layer controlled at about 0.4 mm.

[0073] (2) Preparation of MoSi2-SiC coating

[0074] MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and then a MoSi2-SiC coating with a thickness of about 150 μm was formed by pressing with a mold and covering the surface of the diffusion barrier layer.

[0075] (3) Preparation of double-layer protective structure

[0076] A sandwich structure of Nb matrix with diffusion barrier layer and MoSi2-SiC coating is placed in an SPS device and heated at a rate of 100℃ / min. It is then held at 1500℃ and 40MPa for 10 min to achieve solid-phase bonding, so that Nb matrix / diffusion barrier layer / antioxidant coating form an integral structure, thus preparing a double-layer protective structure for refractory metals.

[0077] The steps for constructing the Nb-based diffusion barrier layer using the high-entropy rare earth oxide powder prepared in this embodiment are the same as those for constructing the Nb-based diffusion barrier layer in Example 1.

[0078] Figure 5 To illustrate the SEM images and energy dispersive spectroscopy (EDS) distribution of the S2 powder prepared in this embodiment as a diffusion barrier layer on a Nb matrix after oxidation at 1600℃ for 100 h (outer layer is MoSi2-SiC), cross-sectional SEM observation showed that the diffusion barrier layer had an intact structure without through cracks, and the Si diffusion depth was 9.44 μm. This indicates that the porous (Dy) nanoparticles composed of short columnar nanoparticles synthesized in this embodiment... 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 S2O3 powder has a stronger barrier effect on Si migration on Nb matrix.

[0079] Example 3:

[0080] A method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals includes the following steps:

[0081] ①. Preparation of precursor solution

[0082] Dissolve 0.8771g of Dy(NO3)3·5H2O, 0.8820g of Ho(NO3)3·5H2O, 0.8867g of Er(NO3)3·5H2O, 0.8901g of Tm(NO3)3·5H2O and 0.8983g of Yb(NO3)3·5H2O in 20ml of deionized water, then add 0.37g of urea and 2.32g of ethylenediaminetetraacetic acid, and mix well to form a precursor solution;

[0083] ②. Preparation of high-entropy rare earth oxide diffusion barrier layer materials by liquid-phase combustion driven reaction

[0084] The precursor solution obtained in step ① was heated at 100°C for 12 min using a magnetic stirrer until it reached a colloidal state. It was then transferred to a furnace filled with N2 atmosphere and held at 600°C for 8 min until a liquid-phase combustion-driven reaction occurred, yielding a sponge-like porous (Dy) structure composed of irregular nanoparticles. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder (S1) is used to prepare a high-entropy rare earth oxide diffusion barrier layer material.

[0085] The preparation method of the high-entropy rare earth oxide diffusion barrier layer material in this embodiment is the same as that in Example 1.

[0086] A method for preparing a double-layer protective structure for refractory metals includes the following steps:

[0087] (1) Preparation of diffusion barrier layer

[0088] Polyvinyl butyral and diethylene glycol monobutyl ether were mixed at a mass ratio of 1:9 and heated to 70°C, stirred until a transparent colloid was formed. The (Dy) prepared above was then added... 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder and transparent colloid were mixed at a mass ratio of 1.2:2 to prepare a slurry, and the slurry was applied to the surface of the Mo substrate by spin coating at a spin coating speed of 2000 rpm to form a diffusion barrier layer, and the thickness of the resulting diffusion barrier layer was controlled at about 0.4 mm.

[0089] (2) Preparation of MoSi2-SiC coating

[0090] MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and then a MoSi2-SiC coating with a thickness of about 150 μm was formed by pressing with a mold and covering the surface of the diffusion barrier layer.

[0091] (3) Preparation of double-layer protective structure

[0092] A sandwich structure of a Mo matrix with a diffusion barrier layer and a MoSi2-SiC coating was placed in an SPS device and heated at a rate of 120 °C / min. The temperature was then maintained at 1500 °C and 40 MPa for 12 min to achieve solid-phase bonding, so that the Mo matrix / diffusion barrier layer / antioxidant coating formed an integral structure, thus preparing a double-layer protective structure for refractory metals.

[0093] Figure 6 To obtain the SEM images and energy dispersive spectroscopy (EDS) distribution of the S1 powder prepared in this embodiment as a diffusion barrier layer on a Mo matrix after oxidation at 1600℃ for 100 h (outer layer is MoSi2-SiC), cross-sectional SEM observation showed that the diffusion barrier layer had an intact structure without through cracks. The diffusion depth of free Si in the upper anti-oxidation coating into the Mo matrix was hindered, and the diffusion layer thickness was only 13.13 μm. No through-silicide layer was observed in the Mo matrix. A continuous and dense solid-state metallurgical interface was formed between the diffusion barrier layer and the matrix, with no debonding, pores, or unsintered areas.

[0094] Example 4

[0095] A method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals includes the following steps:

[0096] ①. Preparation of precursor solution

[0097] Dissolve 0.8771g of Dy(NO3)3·5H2O, 0.8820g of Ho(NO3)3·5H2O, 0.8867g of Er(NO3)3·5H2O, 0.8901g of Tm(NO3)3·5H2O and 0.8983g of Yb(NO3)3·5H2O in 20ml of deionized water, then add 0.75g of urea and 0.94g of glycine, and mix well to form a precursor solution;

[0098] ②. Preparation of high-entropy rare earth oxide diffusion barrier layer materials by liquid-phase combustion driven reaction

[0099] The precursor solution obtained in step ① was heated at 80°C for 10 min using a magnetic stirrer until it reached a colloidal state. It was then transferred to a furnace filled with N2 atmosphere and held at 500°C for 10 min until a liquid-phase combustion-driven reaction occurred, yielding a porous (Dy) structure composed of stacked short columnar nanoparticles. 0.2 Ho 0.2 Er0.2 Tm 0.2 Yb 0.2 The high-entropy rare earth oxide diffusion barrier layer material was prepared by using 2O3 powder (S2).

[0100] The preparation method of the high-entropy rare earth oxide diffusion barrier layer material in this embodiment is the same as that in Example 2.

[0101] A method for preparing a double-layer protective structure for refractory metals includes the following steps:

[0102] (1) Preparation of diffusion barrier layer

[0103] Polyvinyl butyral and diethylene glycol monobutyl ether were mixed at a mass ratio of 1:9 and heated to 70°C, stirred until a transparent colloid was formed. The (Dy) prepared above was then added... 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder and transparent colloid were mixed at a mass ratio of 1.2:2 to prepare a slurry, and the slurry was applied to the surface of the Mo substrate by spin coating at a spin coating speed of 2000 rpm to form a diffusion barrier layer, and the thickness of the resulting diffusion barrier layer was controlled at about 0.4 mm.

[0104] (2) Preparation of MoSi2-SiC coating

[0105] MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and then a MoSi2-SiC coating with a thickness of about 150 μm was formed by pressing with a mold and covering the surface of the diffusion barrier layer.

[0106] (3) Preparation of double-layer protective structure

[0107] A sandwich structure of a Mo matrix with a diffusion barrier layer and a MoSi2-SiC coating was placed in an SPS device and heated at a rate of 120 °C / min. The temperature was then maintained at 1500 °C and 40 MPa for 12 min to achieve solid-phase bonding, so that the Mo matrix / diffusion barrier layer / antioxidant coating formed an integral structure, thus preparing a double-layer protective structure for refractory metals.

[0108] Figure 7 To obtain the SEM image and energy spectrum distribution of the S2 powder prepared in this embodiment as a diffusion barrier layer on the Mo matrix after oxidation at 1600℃ for 100h (outer layer is MoSi2-SiC), cross-sectional SEM observation showed that the diffusion barrier layer structure was intact and no through cracks appeared. The diffusion depth of free Si in the upper anti-oxidation coating to the Mo matrix was significantly hindered, and the diffusion layer thickness was only 11.48μm.

[0109] Comparative Example 1

[0110] This comparative example provides a Nb substrate control sample that does not employ the diffusion barrier layer of the present invention, i.e., only a MoSi2-SiC anti-oxidation coating is directly covered on the surface of the Nb substrate, without constructing a high-entropy rare earth oxide diffusion barrier layer.

[0111] A method for preparing a single-layer protective structure for refractory metals includes the following steps:

[0112] (1) Preparation of MoSi2-SiC coating

[0113] MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and a MoSi2-SiC coating with a thickness of about 150 μm was formed by pressing with a mold to cover the surface of the Nb substrate.

[0114] (2) Preparation of a single-layer protective structure

[0115] The Nb substrate sample with MoSi2-SiC coating was placed in an SPS device and heated at a rate of 100℃ / min. It was then held at 1500℃ and 40MPa for 10 min to achieve solid-phase bonding, so that the Nb substrate / antioxidant coating formed an integral structure, thus preparing a single-layer protective structure for refractory metals.

[0116] Figure 8 The image shows the SEM image and energy dispersive spectroscopy (EDS) distribution of a Nb substrate without a diffusion barrier layer after oxidation at 1600℃ for 100 h (outer layer is MoSi2-SiC). As can be seen from the image, without the diffusion barrier layer, a distinct deep silicide layer forms on the surface of the Nb substrate, with an average diffusion thickness of approximately 41.26 μm. Point analysis reveals a significantly increased Si content in this region, with continuous silicide distribution accompanied by localized pores, cracks, and brittle spalling, indicating that the silicide layer has severely damaged the integrity of the substrate. Furthermore, the interface transition band is wide and irregular, and multiple debonding phenomena occur between the coating and the substrate, suggesting that free Si readily diffuses rapidly into the Nb substrate at 1600℃ and generates a vigorous silicide reaction.

[0117] The oxidation results of this comparative example are in stark contrast to those of Examples 1 and 2: In Examples 1 and 2 of this invention, when powders S1 and S2 are used as diffusion barrier layers, the diffusion thickness of the Nb matrix is ​​approximately 10.91 μm and 9.44 μm, respectively, which is much lower than the diffusion thickness of 41.26 μm in this comparative example without a diffusion barrier layer. This fully demonstrates that the diffusion barrier layer prepared by this invention plays an irreplaceable role in inhibiting Si penetration and maintaining interface stability under long-term high-temperature conditions.

[0118] Comparative Example 2

[0119] This comparative example further provides a Mo substrate control sample that does not employ the diffusion barrier layer of the present invention, i.e., only a MoSi2-SiC anti-oxidation coating is directly covered on the surface of the Mo substrate, without constructing a high-entropy rare earth oxide diffusion barrier layer.

[0120] A method for preparing a single-layer protective structure for refractory metals includes the following steps:

[0121] (1) Preparation of MoSi2-SiC coating

[0122] MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and then a MoSi2-SiC coating with a thickness of about 150 μm was formed by pressing with a mold to cover the surface of the Mo substrate.

[0123] (2) Preparation of a single-layer protective structure

[0124] The Mo matrix sample with the MoSi2-SiC coating was placed in an SPS device and heated at a rate of 120℃ / min. It was then held at 1500℃ and 40MPa for 12 min to achieve solid-phase bonding, so that the Mo matrix / antioxidant coating formed an integral structure, thus preparing a single-layer protective structure for refractory metals.

[0125] Figure 9 The images show the SEM images and energy dispersive spectroscopy (EDS) distribution of a Mo substrate without a diffusion barrier layer after oxidation at 1600℃ for 100 h (outer layer is MoSi2-SiC). The images reveal more intense Si diffusion behavior in the Mo substrate, with an average silicide layer thickness of 54.93 μm. Numerous continuous silicide phases are present within the diffusion layer, exhibiting a loose and brittle structure with a tendency to pulverize both the surface and interior. Simultaneously, the Si diffusion channels in the Mo substrate are more interconnected, indicating that the interaction between the Mo-Si system is more intense at 1600℃, allowing free Si generated in the coating to rapidly penetrate deep into the Mo substrate.

[0126] The oxidation results of this comparative example are in stark contrast to those of Examples 3 and 4: In Examples 3 and 4 of this invention, when powders S1 and S2 are used as diffusion barrier layers, the diffusion thickness of the Mo matrix is ​​approximately 13.13 μm and 11.48 μm, respectively, which is much lower than the diffusion thickness of 54.93 μm in this comparative example without a diffusion barrier layer. This fully demonstrates that the high-entropy rare earth oxide diffusion barrier layer of this invention can significantly improve the diffusion barrier at the interface, effectively block the deep penetration of Si, inhibit severe silanization of the Mo matrix, and greatly improve the structural stability and protective life of the coating system under extreme high temperature conditions.

[0127] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals, characterized in that, Includes the following steps: ①. Preparation of precursor solution Metal nitrates Dy(NO3)3·5H2O, Ho(NO3)3·5H2O, Er(NO3)3·5H2O, Tm(NO3)3·5H2O and Yb(NO3)3·5H2O are dissolved in deionized water, and then fuel is added and mixed evenly to form a precursor solution. ②. Preparation of high-entropy rare earth oxide diffusion barrier layer materials by liquid-phase combustion driven reaction The precursor solution obtained in step ① was heated and stirred at 80–130°C until it reached a colloidal state. It was then transferred to a furnace filled with inert gas and held at 300–700°C until a liquid-phase combustion-driven reaction occurred, yielding ultrafine-grained porous (Dy) materials. 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3 powder, that is, to prepare a high-entropy rare earth oxide diffusion barrier layer material.

2. The method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals according to claim 1, characterized in that, In step S1, the total molar ratio of fuel to metal nitrate is (1.25-3.75):1, and the molar amounts of Dy(NO3)3·5H2O, Ho(NO3)3·5H2O, Er(NO3)3·5H2O, Tm(NO3)3·5H2O and Yb(NO3)3·5H2O are equal.

3. The method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals according to claim 2, characterized in that, In step S1, the fuel is selected from at least one of glycine, urea, and ethylenediaminetetraacetic acid.

4. The high-entropy rare-earth oxide diffusion barrier layer material prepared by the method for preparing a high-entropy rare-earth oxide diffusion barrier layer material for refractory metals according to any one of claims 1 to 3, characterized in that, The chemical composition is (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )2O3, with a grain size of 10-70nm.

5. A method for preparing a double-layer protective structure for refractory metals, characterized in that, Includes the following steps: (1) Preparation of diffusion barrier layer The organic binder and solvent are mixed and heated and stirred until a transparent colloid is formed. Then, the high entropy rare earth oxide diffusion barrier layer material described in claim 4 is mixed with the transparent colloid at a mass ratio of (1-1.5):2 to form a slurry. The slurry is then applied to the surface of a refractory metal substrate by spin coating to form a diffusion barrier layer. (2) Preparation of MoSi2-SiC coating MoSi2 and SiC were mixed at a volume ratio of 8:2 to prepare powder, and then a MoSi2-SiC coating was formed by pressing with a mold and covering the surface of the diffusion barrier layer. (3) Preparation of double-layer protective structure A refractory metal substrate with a diffusion barrier layer and a MoSi2-SiC coating is subjected to spark plasma sintering to solidify the refractory metal substrate, the diffusion barrier layer, and the MoSi2-SiC coating, thus preparing a double-layer protective structure.

6. The method for preparing a double-layer protective structure for refractory metals according to claim 5, characterized in that, In step (1), the organic binder is selected from at least one of polybutyl acrylate or polyvinyl butyral, and the solvent is selected from at least one of butanol or diethylene glycol monobutyl ether. The mass ratio of organic binder to solvent is 1:

9.

7. The method for preparing a double-layer protective structure for refractory metals according to claim 5, characterized in that, In step (1), the refractory metal matrix is ​​Nb or Mo.

8. The method for preparing a double-layer protective structure for refractory metals according to claim 5, characterized in that, In step (1), the thickness of the diffusion barrier layer is 0.35-0.75 mm, and in step (2), the thickness of the MoSi2-SiC coating is 50-300 μm.

9. The method for preparing a double-layer protective structure for refractory metals according to claim 5, characterized in that, In step (3), the temperature of the discharge plasma sintering is 1300-1700℃, the heating rate is 50-200℃ / min, and the holding time is 3-20min.

10. The double-layer protective structure prepared by any one of the preparation methods for a double-layer protective structure for refractory metals according to any one of claims 5-9.

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