A composite coating material based on two-dimensional structure MAX phase and a preparation method thereof

Abstract

The application discloses a kind of composite coating materials based on two-dimensional structure MAX phase and preparation method thereof.The composite coating material includes the reconstruction MAX phase as substrate and the continuous, dense ceramic coating that is tightly attached to its surface and its interlamination by chemical bonding.The reconstruction MAX phase is formed by structure reconstruction of original MAX phase, and has two-dimensional nanosheet structure.The structure reconstruction only changes the A atom layer in the original MAX phase, and the carbon titanium main structure is not damaged, so the reconstructed MAX phase has surface activity like MXene two-dimensional material, and also retains the high-temperature oxidation resistance of the original MAX phase, and the excellent heat insulation and protection performance of the surface and interlamination dense ceramic coating, so it has broad application prospects in aerospace engine thermal barrier coating, nuclear reactor material surface protection, high-temperature sensor and energy conversion device and other fields.

Description

Technical Field

[0001] This invention belongs to the field of new material preparation technology, specifically relating to a high-temperature protective coating material, and more particularly to a composite coating material based on a two-dimensional MAX phase and its preparation method. Background Technology

[0002] The general formula for MAX phase materials is M n+1 AX n In the MAX phase, M represents early transition metals, A mainly consists of Group IIIA and IVA elements, and X is C or N; it has attracted widespread attention due to its excellent properties combining those of metals and ceramics. Two-dimensional layered materials, MXene, can be obtained by selectively etching away the A atomic layer from the MAX phase. MXene possesses high specific surface area, abundant surface functional groups, and good electrical conductivity, but it is prone to structural degradation in high-temperature oxidizing environments, limiting its direct application as a high-temperature component.

[0003] Yttrium-stabilized zirconia (YSZ) is a recognized superior high-temperature thermal barrier coating material, possessing a high melting point, low thermal conductivity, and excellent high-temperature phase stability. Currently, fabricating uniform, dense, and strongly bonded YSZ coatings on complex-shaped or micro / nano-scale substrates remains a challenge. Traditional physical vapor deposition or thermal spraying techniques struggle to achieve uniform coating and strong adhesion on highly surface-active two-dimensional materials.

[0004] Currently, there is a lack of methods to effectively combine the intrinsic advantages of two-dimensional materials with the protective performance of high-performance ceramic coatings. In particular, how to construct a continuous, dense ceramic protective layer with good thermal compatibility for two-dimensional materials without damaging their unique structure is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a uniform and dense YSZ ceramic coating on a two-dimensional material substrate with advantages such as intrinsic thermal stability. This method first obtains a two-dimensional MAX phase intermediate with intrinsic thermal stability through a "molten salt etching-reduction reconstruction" process. Then, a YSZ coating is obtained by in-situ growth and sintering on its surface with ultrasonic assistance, thereby obtaining a novel composite coating material that combines the properties of two-dimensional materials with high-temperature protective performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] This invention provides a composite coating material based on a two-dimensional MAX phase structure, the composite coating material comprising: The reconstructed MAX phase serves as the substrate, formed by structural reconstruction of the original MAX phase to create a MAX phase with a two-dimensional nanosheet structure; wherein, the original MAX phase refers to the MAX phase conventionally referred to in this technical field as having an M n+1 AX n For ease of distinction, the MAX phase in the general formula is referred to as the "original MAX phase" in this invention; And a continuous, dense ceramic coating that is chemically bonded tightly to the surface of the reconstructed MAX phase and between its layers.

[0008] The microstructure of the reconstructed MAX phase is as follows: the surface functional group Tx in MXene is composed of A atoms replaced by the original MAX phase; wherein MXene corresponds to the original MAX phase, that is, the two-dimensional nanosheet material formed by selectively etching away the A atom layer of the original MAX phase.

[0009] Furthermore, the A atom in the original MAX phase is an aluminum (Al) atom.

[0010] Furthermore, the original MAX phase is selected from one or more of Ti3AlC2, Ti2AlC, V2AlC, and Cr2AlC.

[0011] The ceramic coating material is yttrium-stabilized zirconia (YSZ) ceramic.

[0012] This invention also provides a method for preparing the above-mentioned composite coating material based on the two-dimensional MAX phase, wherein the ceramic coating material in the composite coating material is YSZ ceramic, and the preparation method includes the following steps: Step S1: Obtain the MXene material corresponding to the original MAX phase, wherein the A atoms in the original MAX phase are Al atoms. Preferably, the MXene material is prepared from the original MAX phase raw material by molten salt etching.

[0013] More specifically, step S1 is as follows: the raw material powder of the original MAX phase is mixed with the molten salt etchant powder, and under the protection of an inert atmosphere, it is heated to above the melting point of the molten salt etchant to carry out the etching reaction. After cleaning and drying, a two-dimensional MXene material is obtained; wherein, the molten salt etchant contains metal chlorides and alkali metal chlorides.

[0014] Step S2, reconstruction of the two-dimensional MAX phase structure: The MXene material obtained in step S1 is uniformly mixed with an excess of aluminum source, and heat-treated under an inert or reducing atmosphere to allow aluminum atoms to re-insert into the MXene interlayer, thereby obtaining the reconstructed MAX phase with a two-dimensional nanosheet structure.

[0015] Step S3, in-situ growth of YSZ coating with ultrasound assistance: Using the reconstructed MAX phase material obtained in step S2 as a substrate, a sol-gel method is used to coat and grow a sol-YSZ precursor on its surface; during or after coating, the system is subjected to ultrasound treatment and dried to promote the penetration and uniform distribution of the precursor between the two-dimensional nanosheets of the reconstructed MAX phase.

[0016] Step S4, coating densification sintering: The substrate material coated with YSZ precursor obtained in step S3 is sintered in a protective atmosphere or vacuum to crystallize and densify the YSZ precursor, and finally obtain a composite coating material composed of a two-dimensional reconstructed MAX phase substrate and a continuous YSZ ceramic coating.

[0017] Further, in step S1, the original MAX phase raw material is selected from one or more of Ti3AlC2, Ti2AlC, V2AlC, and Cr2AlC.

[0018] Further, in step S1, the metal chloride in the molten salt etching agent is selected from one or more of CuCl2, FeCl2, and ZnCl2, and is prepared with the MAX phase at a molar ratio of 3:1; the alkali metal chloride is selected from one or more of KCl, NaCl, and LiCl. If it is a mixture of multiple alkali metal chlorides, each alkali metal chloride is prepared in any proportion to reduce the melting point of the mixed molten salt system and adjust its reactivity.

[0019] Further, in step S2, the aluminum source is an excess of aluminum powder, aluminum foil, or aluminum-containing compound; the heat treatment temperature is 700-1100℃, and the time is 1-6 hours; further, the MXene material is mixed with aluminum powder or aluminum foil at a mass ratio of 1:2.

[0020] Further, in step S3, the precursor used in the sol-gel method includes, but is not limited to, a mixed solution of zirconium oxychloride and yttrium nitrate, with citric acid as a complexing agent, wherein the doping amount of Y2O3 is 1-10 mol% YSZ; the ultrasonic treatment power is 100-500W, and the time is 10-60 minutes.

[0021] Furthermore, in step S4, the sintering treatment temperature is 1200-1500℃ and the time is 1-4 hours.

[0022] This invention obtains a new MAX phase with a two-dimensional nanosheet structure, namely the reconstructed MAX phase, through the reconstruction of the MAX phase. This reconstructed MAX phase simultaneously possesses the surface activity of two-dimensional materials and the high-temperature oxidation resistance of the original MAX phase. Furthermore, leveraging the large specific surface area of ​​the two-dimensional reconstructed MAX phase, a YSZ precursor is grown on its surface using a sol-gel method, and a strong bond between the two-dimensional material and YSZ ceramic is achieved through high-temperature sintering. In obtaining the reconstructed MAX phase, this invention uses a MAX phase with aluminum atoms as the atom layer, and subsequently, preferably, the atom layer is etched using a molten salt etching method to obtain MXene material. The MXene obtained by this method has surface functional groups with Cl... - The primary method is wet etching, rather than methods like hydrofluoric acid or lithium fluoride hydrochloride, which form more F on the surface. - And hydroxyl functional groups; then, under the protection of an inert or reducing atmosphere, heat treatment is used to fuse aluminum atoms with the surface functional groups Cl. - The aluminum chloride is formed by the combination and volatilized at the high temperature of the heat treatment, thereby removing the unstable functional groups on the MXene surface. At the same time, the excess Al atoms fill the gaps left by the removed Cl atoms. - The vacant spaces are re-inserted between MXene layers to obtain the reconstructed MAX phase with a two-dimensional nanosheet structure. This reconstruction only changes the aluminum atom layer in the original MAX phase, without destroying the carbon-titanium main structure. Therefore, the obtained reconstructed MAX phase has both the surface activity of MXene two-dimensional materials and the high-temperature oxidation resistance of the original MAX phase.

[0023] The beneficial effects of this invention are as follows: (1) The resulting composite coating material retains the surface activity of two-dimensional materials and the high-temperature oxidation resistance of the MAX phase, and the excellent thermal insulation and protection performance of the YSZ coating makes it have broad application prospects in the fields of thermal barrier coatings for aerospace engines, surface protection of nuclear reactor materials, high-temperature sensors and energy conversion devices.

[0024] (2) The molten salt etching system with adjustable components is adopted, which has a mild reaction and easy-to-control conditions. The introduction of ultrasonic-assisted sol-gel process effectively solves the problem that the precursor solution is difficult to fully wet and penetrate into the interlayer of two-dimensional materials by traditional methods, and greatly improves the uniformity of YSZ coating in three-dimensional direction and the bonding strength with the substrate.

[0025] (3) Enhanced reliability: By reconstructing the MAX phase as a transition substrate, its structure has better thermal matching with YSZ; ultrasonic assistance ensures the in-situ continuous and dense growth of YSZ on the surface and gaps of the sheets, forming a three-dimensional interlocked composite structure, which improves the coating adhesion and the anti-stripping performance under harsh conditions such as thermal cycling, and enhances the reliability of the composite coating material.

[0026] (4) The reduction and reconstruction and in-situ growth process parameters of ceramic coating used in this invention are easy to control precisely, and the coating composition, thickness and microstructure can be effectively regulated with good repeatability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the original MAX, MXene phase and reconstructed MAX phase structure during the process of preparing the composite coating material according to the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the composite coating material based on the two-dimensional MAX phase prepared in this invention before and after densification of the YSZ coating.

[0029] Figure 3 The images show the XRD patterns of the original MAX phase, MXene, and the two-dimensional reconstructed MAX phase in Embodiment 1 of the present invention.

[0030] Figure 4 This is a scanning electron microscope (SEM) image of the composite coating material based on the two-dimensional MAX phase obtained in Example 1 of the present invention before densification sintering. Detailed Implementation

[0031] To make the objectives and technical solutions of this invention clearer and more complete, the invention will be further described in detail below with reference to embodiments. Unless otherwise specified, the reagents and materials involved in the embodiments of this invention are all commercially available products and can be purchased through commercial channels.

[0032] Example 1

[0033] In this embodiment, the original MAX phase is Ti3AlC2, and a method is provided for in-situ growth of YSZ ceramic coating based on two-dimensional reconstruction of Ti3AlC2 phase and using the reconstructed Ti3AlC2 phase as substrate.

[0034] (1) Preparation of MXene by molten salt etching: Ti3AlC2 and CuCl2 were prepared in a molar ratio of 1:3 and thoroughly ground and mixed with appropriate amounts of etching agent NaCl and KCl powder. The NaCl and KCl powders could be prepared in any ratio. In this example, the molar ratio of NaCl to KCl powder was 1:1. The mixture was placed in a tube furnace and protected with argon gas. It was heated to 550°C (higher than the eutectic melting point of the mixed molten salt) at a conventional heating rate (e.g., 5-10°C / min) and held at this temperature for 4 hours for etching reaction. After the reaction, the product was repeatedly centrifuged and washed with dilute hydrochloric acid and deionized water until neutral. After freeze-drying, multilayer Ti3C2T was obtained. x MXene powder.

[0035] like Figure 1Figure a shows a schematic diagram of the original MAX phase Ti3AlC2 structure as described in this embodiment, which presents a three-dimensional bulk shape. Through the molten salt etching process in this step, the A atom layer (Al atoms) in the bulk Ti3AlC2 is etched away, forming a structure as shown in Figure a. Figure 1 Figure b shows Ti3C2T with a two-dimensional nanosheet structure. x (MXene), in which the nanosheets are stacked in an accordion-like manner. In this embodiment, the MXene material Ti3C2T was prepared by etching the A atomic layer using molten salt etching. x Its surface functional group Tx is Cl - Mainly.

[0036] (2) Aluminum reduction to obtain two-dimensional reconstruction MAX: The Ti3C2T obtained above was used to reduce the aluminum content of ... x (MXene) powder and excess aluminum powder were mixed uniformly at a mass ratio of 1:2 and placed in a tube furnace. The mixture was heated to 950℃ at a rate of 5℃ / min under argon protection and held for 3 hours. After natural cooling, a two-dimensional reconstructed Ti3AlC2 material was obtained. During this process, under an inert atmosphere, aluminum atoms and surface functional groups Cl... - The combination forms aluminum chloride, which volatilizes and removes the surface functional groups Tx from the MXene structure at high temperatures during heat treatment; simultaneously, as... Figure 1 Figure c shows that excess Al atoms are inserted into the dispersed carbon-titanium sheets, filling the gaps left by the removed Cl atoms. - The remaining vacancies, and the insertion of Al atoms, allow the titanium carbon sheets to remain dispersed and non-agglomerated, resulting in a reconstructed MAX phase with a two-dimensional nanosheet structure. This reconstructed MAX phase is as follows: Figure 1 As shown in Figure d, it has an open two-dimensional structure between the layers. Obviously, this reconstruction only changed the structure of the aluminum atom layers in the original MAX phase, and the main carbon-titanium structure was not destroyed.

[0037] Characterized by XRD, such as Figure 3 As shown, this embodiment contains the original MAX phase Ti3AlC2 (labeled "MAX" in the figure) and the MXene phase Ti3C2T. x (Identified as “MXene” in the figure) and the XRD pattern of the reconstructed MAX Ti3AlC2 phase (identified as “2D-MAX” in the figure). It can be seen from the figure that the (002) peak shifts to the left after etching. After Al reduction, it appears as a broad peak due to the difference in interlayer spacing. The Al peak at about 39° shows obvious disappearance and recovery after etching and reconstruction, and the characteristic peak of the MAX phase reappears. This confirms that the phase structure of the reconstructed MAX Ti3AlC2 phase has been successfully restored. Like the original MAX Ti3AlC2 phase, its main carbon-titanium structure has not changed.

[0038] (3) Ultrasonic-assisted sol-gel in-situ growth of YSZ: 8 mol% Y2O3-doped YSZ sol was prepared. The reconstructed two-dimensional Ti3AlC2 powder was dispersed in the sol at a ratio of 10 wt%, and ultrasonically treated at 200 W for 30 minutes to allow the sol to fully penetrate the interlamellar gaps. Subsequently, a film was formed on the substrate using the dip-coating method, and then heat-treated in air at 400℃ for 1 hour to decompose the precursor. This step uses the reconstructed MAX phase material as a substrate, and forms a YSZ precursor film on it using the sol-gel method, such as... Figure 2 The left image shows that, under ultrasonic treatment, the YSZ precursor film not only coats the surface of the reconstructed MAX phase, but also permeates between the two-dimensional nanosheets of the reconstructed MAX phase and exhibits a uniform distribution.

[0039] (4) Coating sintering densification: The sample was placed in a vacuum sintering furnace and sintered at 1400℃ for 2 hours, then cooled with the furnace to obtain the final composite coating material, such as Figure 2 As shown in the right figure, the composite coating material is based on the reconstructed MAX phase. The YSZ precursor film coated on its surface and between the layers is sintered in this step to form a dense YSZ ceramic film continuously distributed on the surface and between the layers. This results in a composite coating material with a three-dimensional interlocking structure of the reconstructed MAX phase and YSZ ceramic, which improves the coating adhesion and anti-peeling performance under harsh conditions such as thermal cycling.

[0040] like Figure 4 The image shows a scanning electron microscope (SEM) image of the composite coating material based on the two-dimensional structure of the MAX phase prepared in this embodiment before densification sintering. The image shows that the reconstructed Ti3AlC2MAX phase on the substrate presents a two-dimensional structure of nanosheets. The gaps between the sheets and the surface of the sheets are uniformly covered with YSZ ceramic precursor. After sintering, the YSZ ceramic and the MAX phase of the substrate form a three-dimensional interlocked composite structure.

[0041] Example 2

[0042] In this embodiment, the original MAX phase is Ti2AlC, and a method is provided for in-situ growth of YSZ ceramic coating based on two-dimensional reconstruction of Ti2AlC phase and using the reconstructed Ti2AlC phase as substrate.

[0043] Compared to Example 1, this example also uses a different etchant (ZnCl2-based molten salt), and the preparation steps are as follows.

[0044] (1) Preparation of MXene by molten salt etching: Ti2AlC powder and ZnCl2 powder were mixed in a molar ratio of 1:3 with an appropriate amount of NaCl and KCl powder in a molar ratio of 1:1, and thoroughly ground in a mortar for 30 minutes. The mixed powder was placed in an alumina crucible and then placed in a tube furnace. Under continuous argon (Ar) protection, the temperature was increased to 520℃ at a rate of 8℃ / min (based on the ZnCl2-NaCl-KCl ternary phase diagram, this temperature is higher than its lowest eutectic point), and held at this temperature for 5 hours for etching reaction. After the reaction was completed, the furnace temperature was allowed to drop to room temperature, and the product was taken out. The product was ground and washed with 1M hydrochloric acid solution in a 60℃ water bath for 2 hours to remove zinc oxide and by-products. Then, it was repeatedly centrifuged and washed with deionized water until the conductivity of the supernatant was less than 50 μS / cm. Finally, it was freeze-dried to obtain Ti2CCl. x MXene powder.

[0045] (2) Aluminum reduction and reconstruction of two-dimensional MAX: The above Ti2CCl x MXene powder was mixed with an excess of 200-mesh aluminum powder at a mass ratio of 1:2. The mixture was placed in a tube furnace and heated to 900°C at a rate of 5°C / min under flowing argon protection, and held at that temperature for 4 hours. After natural cooling, the reconstructed two-dimensional Ti2AlC material was obtained. X-ray diffraction (XRD) analysis and comparison with a standard Ti2AlC card confirmed the successful recovery of its MAX phase crystal structure, and scanning electron microscopy (SEM) showed that it still maintained its two-dimensional lamellar morphology.

[0046] (3) In-situ growth of YSZ using ultrasound-assisted sol-gel method: 8YSZ sol was prepared using the same formulation as in Example 1. The reconstructed two-dimensional Ti2AlC powder was dispersed in the sol at a ratio of 5 wt%. The suspension was placed in an ultrasonic processor and ultrasonically treated in an ice-water bath for 40 minutes at a power of 250W and a frequency of 40kHz to prevent overheating of the sol and promote penetration. Subsequently, a film was formed on a clean Al2O3 substrate by spin coating (2000 rpm, 30 seconds). After drying the wet film at 80°C for 10 minutes, it was placed in a muffle furnace and heat-treated in an air atmosphere at 450°C for 1 hour to allow the organic components to fully decompose.

[0047] (4) Coating densification by sintering: The heat-treated sample was placed in an atmosphere sintering furnace and heated to 1350℃ at a rate of 3℃ / min under the protection of flowing high-purity nitrogen. The temperature was held for 2.5 hours and then cooled with the furnace. The obtained Ti2AlC / YSZ composite coating was observed by cross-sectional SEM, which showed that the YSZ coating had a uniform thickness (about 500nm), was dense, and was tightly bonded to the two-dimensional Ti2AlC substrate.

[0048] Example 3

[0049] (1) Preparation of MXene by molten salt etching: Similar to Example 1, Ti3AlC2 powder was etched using a CuCl2 / NaCl / KCl mixed molten salt system to obtain multilayer Ti3C2T x MXene.

[0050] (2) Two-dimensional MAX phase structure reconstruction: The MXene powder was mixed with excess aluminum powder. Under argon protection, the temperature was increased to 700°C at 5°C / min and held for 1 hour. After cooling, the reconstructed two-dimensional Ti3AlC2 material was obtained. XRD characterization showed that after treatment at 700°C for 1 hour, the characteristic peaks of MXene basically disappeared, while the characteristic peaks of Ti3AlC2 reappeared, indicating that aluminum atoms were successfully inserted and the structure was reconstructed. However, the peak intensity was slightly weaker than that of Example 1, indicating that the crystallinity was slightly lower than that of Example 1, mainly due to the influence of processing temperature and time.

[0051] (3) Ultrasonic-assisted sol-gel in situ growth of YSZ: Prepare 8YSZ sol. Disperse the reconstituted Ti3AlC2 powder obtained in step (2) in the sol, and perform ultrasonic treatment in an ice-water bath at 500W for 10 minutes to allow the precursor to penetrate rapidly. Then, heat treat at 400℃ for 1 hour to obtain a dry mixed powder.

[0052] (4) Coating densification by sintering: The sample was placed in a vacuum furnace and sintered at 1400℃ for 2 hours. The resulting coating was observed by SEM. The YSZ ceramic was uniformly distributed on the surface and between the layers. Due to the slightly lower crystallinity of the reconstructed phase in step (2), the bonding strength between the coating and the substrate was slightly lower than that in Example 1, but it was still significantly better than the uncoated MXene material. This indicates that the composite coating can still be successfully prepared and has basic protective properties under the process parameters.

[0053] Example 4

[0054] (1) Preparation of MXene by molten salt etching: Referring to Example 1, the raw material was replaced with V2AlC powder, and V2CT was prepared using a molten salt etching method with a FeCl2 / NaCl / KCl mixed molten salt system. x MXene.

[0055] (2) Two-dimensional MAX phase structure reconstruction: V2CT xMXene was mixed with excess aluminum powder. Under argon protection, the mixture was heated to 1100℃ and held for 6 hours. After cooling, the reconstructed two-dimensional V2AlC material was obtained. XRD and SEM characterization showed that after high-temperature and long-term treatment, the reconstructed V2AlC phase had very high crystallinity, the two-dimensional lamellar structure remained intact, and the lamellar size slightly increased, indicating good thermal stability.

[0056] (3) Ultrasonic-assisted sol-gel in situ growth of YSZ: A 5 mol% Y2O3-doped YSZ sol was prepared. Reconstructed V2AlC powder was dispersed in the sol and subjected to mild ultrasonic treatment at 100 W for 60 minutes. This embodiment achieves sufficient precursor penetration even with lower energy input by extending the treatment time. Subsequent heat treatment steps are the same as in Example 1.

[0057] (4) Coating densification by sintering: The substrate was sintered at 1500℃ under vacuum for 2 hours. Cross-sectional SEM revealed that the YSZ coating was very dense, forming a well-defined three-dimensional interlocking structure with the reconstructed V2AlC substrate. Due to the high-temperature, long-term reconstruction of the substrate, it exhibited excellent thermal stability and good thermal compatibility with the high-temperature sintered YSZ coating, demonstrating superior high-temperature resistance to spalling.

[0058] Example 5

[0059] The reconstructed Ti3AlC2 sample coated with YSZ precursor, processed in steps (1)(2)(3) of Example 1, was used as the unified initial material.

[0060] Sample preparation and processing: The reconstructed Ti3AlC2 samples coated with YSZ precursor from the same batch were divided into two parts, sample A and sample B. Sample A was placed in a vacuum sintering furnace and sintered at 1200℃ for 4 hours; sample B was placed in a vacuum sintering furnace and sintered at 1500℃ for 1 hour.

[0061] Results and characterization: XRD analysis: Both samples showed complete cubic phase YSZ diffraction peaks and Ti3AlC2 diffraction peaks, confirming that the coatings had crystallized.

[0062] SEM analysis: The YSZ coating of sample A is continuously distributed, but the grain size is small, about 50-100 nm, and the porosity is slightly higher than that of sample B. The YSZ coating of sample B is extremely dense, with significantly grown grains of about 200-500 nm and clear grain boundaries.

[0063] Performance comparison: Nanoindentation test shows that the coating hardness and modulus of sample B are higher than those of sample A. This is because the higher sintering temperature promotes grain growth and densification.

[0064] The above embodiments are merely examples of the present invention. Although the preferred embodiments and accompanying drawings have been disclosed for illustrative purposes, the present invention is not limited to the above embodiments. Any substitutions, variations, and modifications are possible by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the preferred embodiments and accompanying drawings.

Claims

1. A composite coating material based on a two-dimensional MAX phase, characterized in that, The composite coating material includes: The reconstructed MAX phase serves as the substrate, which is a MAX phase with a two-dimensional nanosheet structure formed by structural reconstruction of the original MAX phase. And, a continuous, dense ceramic coating that is tightly bonded to the surface of the reconstructed MAX phase and between its layers by chemical bonding; The microstructure of the reconstructed MAX phase is characterized by the surface functional group Tx in MXene being replaced by A atoms from the original MAX phase; wherein MXene corresponds to the original MAX phase, i.e., the two-dimensional nanosheet material formed by selectively etching away the A atom layer of the original MAX phase.

2. The composite coating material based on a two-dimensional MAX phase according to claim 1, characterized in that: The A atom in the original MAX phase is an aluminum atom.

3. The composite coating material based on a two-dimensional MAX phase according to claim 2, characterized in that: The original MAX phase is selected from one or more of Ti3AlC2, Ti2AlC, V2AlC, and Cr2AlC.

4. The composite coating material based on a two-dimensional MAX phase according to claim 1, characterized in that: The ceramic coating material is yttrium-stabilized zirconia ceramic.

5. A method for preparing a composite coating material based on a two-dimensional MAX phase according to any one of claims 1 to 4, wherein the ceramic coating material in the composite coating material is YSZ ceramic, and the preparation method includes the following steps: Step S1: Obtain the MXene material corresponding to the original MAX phase, wherein the A atom in the original MAX phase is an Al atom; Step S2, reconstruction of two-dimensional MAX phase structure: The MXene material obtained in step S1 is uniformly mixed with an excess of aluminum source, and heat-treated under an inert or reducing atmosphere to allow aluminum atoms to re-insert into the MXene interlayer, thereby obtaining the reconstructed MAX phase with a two-dimensional nanosheet structure; wherein the aluminum source is aluminum powder, aluminum foil or aluminum-containing compound. Step S3, in-situ growth of YSZ coating with ultrasound assistance: Using the reconstructed MAX phase material obtained in step S2 as the substrate, a sol-gel method is used to coat and grow a sol-YSZ precursor on its surface; during or after the sol coating process, the system is subjected to ultrasound treatment and dried to promote the penetration and uniform distribution of the precursor between the two-dimensional nanosheets of the reconstructed MAX phase. Step S4, coating densification sintering: The substrate material coated with YSZ precursor obtained in step S3 is sintered in a protective atmosphere or vacuum to crystallize and densify the YSZ precursor, and finally obtain a composite coating material composed of a two-dimensional reconstructed MAX phase substrate and a continuous YSZ ceramic coating.

6. The method for preparing a composite coating material based on a two-dimensional MAX phase according to claim 5, characterized in that: In step S1, the original MAX phase raw material is selected from one or more of Ti3AlC2, Ti2AlC, V2AlC, and Cr2AlC.

7. The method for preparing a composite coating material based on a two-dimensional MAX phase according to claim 5, characterized in that, Step S1, the MXene material is prepared from the original MAX phase raw material by molten salt etching: The raw material powder of the original MAX phase is mixed with the molten salt etchant powder, and the mixture is heated to above the melting point of the molten salt etchant under an inert atmosphere to carry out the etching reaction. After cleaning and drying, a two-dimensional MXene material is obtained. The molten salt etchant contains metal chlorides and alkali metal chlorides.

8. The method for preparing a composite coating material based on a two-dimensional MAX phase according to claim 7, characterized in that, In step S1, the molten salt etching agent contains a metal chloride selected from one or more of CuCl2, FeCl2, and ZnCl2; and an alkali metal chloride selected from one or more of KCl, NaCl, and LiCl.

9. The method for preparing a composite coating material based on a two-dimensional MAX phase according to claim 5, characterized in that, In step S2, the aluminum source is aluminum powder or aluminum foil, and the MXene material is mixed with aluminum powder or aluminum foil at a mass ratio of 1:2; the heat treatment temperature is 700-1100℃ and the time is 1-6 hours.

10. The method for preparing a composite coating material based on a two-dimensional MAX phase according to claim 5, characterized in that, In step S3, the precursor used in the sol-gel method is a mixed solution of zirconium oxychloride and yttrium nitrate, with citric acid as a complexing agent, wherein the doping amount of Y2O3 is 1-10 mol% YSZ; the reconstructed MAX phase is coated at a ratio of 5-10 wt% of sol-gel YSZ to form the YSZ precursor; the ultrasonic treatment power is 100-500W and the time is 10-60 minutes.

11. The method for preparing a composite coating material based on a two-dimensional MAX phase according to claim 5, characterized in that, In step S4, the sintering temperature is 1200-1500℃ and the time is 1-4 hours.

12. The application of a composite coating material based on a two-dimensional MAX phase according to any one of claims 1 to 4, characterized in that, The composite coating material is used in the preparation of aerospace thermal barrier coatings or nuclear reactor material protective layers.

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