Dual-force electric coupling microcrack self-healing high-temperature gas valve coating as well as preparation method and application thereof

Abstract

The invention discloses a dual-force electric coupling microcrack self-healing high-temperature gas valve coating and a preparation method and application thereof, and particularly relates to the field of high-temperature gas valve coatings. Comprising the following steps: performing cold press molding on a crystal material to obtain a sheet; wherein the crystal material can generate stress-induced reverse charges when the temperature is lower than a critical switching temperature, and can generate strain gradient-induced reverse charges when the temperature is higher than the critical switching temperature; the sheet serves as a solid material source, the solid material source is deposited on the high-temperature gas valve through a physical vapor deposition method, and an initial coating is obtained on the surface of the high-temperature gas valve; and carrying out polarization treatment on the initial coating to obtain the micro-crack self-healing coating. When cracks are healed, the phase change process does not occur, no new product is generated, the long-time stability of the mechanical property of the high-temperature gas valve material can be guaranteed, and spontaneous healing can be achieved without depending on external excitation.

Description

Technical Field

[0001] The present application relates to the field of high-temperature gas valve coatings, and in particular to a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating and its preparation method and application. Background Art

[0002] High-temperature gas valves are core components of solid-state attitude and orbit control propulsion systems. Their reliability and structural integrity determine their operational performance. High-temperature gas valves are prone to microcracks during molding, storage, transportation, and use. These microcracks are often difficult to detect and can quickly develop into pits under the impact of high-temperature gas erosion, causing damage, leakage, and even cracking in the valves. This reduces the quality stability and operational reliability of the system. Therefore, developing a novel coating and preparation method for high-temperature gas valves that can achieve self-healing microcracks is crucial.

[0003] Coating self-healing refers to the ability of a coating to automatically repair its own performance and structure after being damaged to restore its protective function. Compared with amorphous soft materials, hard materials are generally difficult to achieve self-healing. Existing hard coating self-healing functions are mostly based on the glassy flow material generated by high-temperature oxidation to fill and seal microcracks, achieving an oxidation isolation effect and preventing oxidation failure. However, this crack self-healing mode has two limitations: one is that it requires external stimulation; the other is that it will cause changes in the local material mechanical properties of the high-temperature gas valve, resulting in uneven stress distribution. Summary of the Invention

[0004] The main purpose of this application is to provide a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating and its preparation method and application, aiming to solve the problem that the existing crack self-healing high-temperature gas valve coating requires external excitation and causes uneven stress distribution of the high-temperature gas valve.

[0005] To achieve the above-mentioned objectives, the present application provides a method for preparing a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating, comprising: cold-pressing a crystalline material to obtain a sheet; wherein the crystalline material can generate stress-induced reverse charge below the critical switching temperature, and generate strain gradient-induced reverse charge above the critical switching temperature; using the sheet as a solid material source, and depositing the solid material source on the high-temperature gas valve through a physical vapor deposition method to obtain an initial coating on the surface of the high-temperature gas valve; wherein, during the deposition process, the deposition temperature is 300°C~500°C, and the deposition time is 60min~120min; and the initial coating is polarized to obtain a microcrack self-healing coating.

[0006] Optionally, the crystalline material is barium titanate or molybdenum disulfide powder.

[0007] Optionally, the preparation method of the sheet includes: placing the crystal material in a mold, cold pressing it under an axial stress of 200MPa~350MPa for 2min~4min to form a green body; sintering the green body in an environment of a temperature of 1000℃~1400℃ for 3h~5h to obtain the sheet.

[0008] Optionally, the particle size of the crystalline material is 200 nm to 500 nm.

[0009] Optionally, during the deposition process, the distance between the high-temperature gas valve and the sheet is 5 mm to 30 mm.

[0010] Optionally, the polarization electric field applied during the polarization process is 5 kV / cm to 15 kV / cm.

[0011] To achieve the above objectives, the present application also provides a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating, characterized in that it is obtained by the above preparation method; wherein the thickness of the coating is 0.005μm~5μm.

[0012] The microcrack self-healing coating generates a crack self-healing distance of less than or equal to 80 μm and a crack self-healing time of less than or equal to 3 ms through stress-induced reverse charge attraction.

[0013] The microcrack self-healing coating generates a crack self-healing distance of less than or equal to 5 μm and a crack self-healing time of less than or equal to 0.5 ms through the reverse charge attraction induced by the strain gradient.

[0014] To achieve the above objectives, the present application also provides an application of a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating in a solid attitude and orbit control engine.

[0015] Compared with the prior art, the present invention has the following advantages: The preparation method of the dual electromechanical coupling microcrack self-healing high-temperature gas valve coating of the present invention selects a crystal material that can generate stress-induced reverse charge in an environment below the critical switching temperature and generate strain gradient-induced reverse charge in an environment above the critical switching temperature, and deposits it on the surface of the high-temperature gas valve as the coating raw material. The crack self-healing function can be achieved both in a normal temperature environment and in a high-temperature working environment; and when the external ambient temperature is higher than the critical switching temperature, the crack self-healing function can be switched from the stress-induced reverse charge suction force to the strain gradient-induced reverse charge suction force, thereby realizing the dual electromechanical coupling microcrack self-healing function.

[0016] The dual electromechanical coupling microcrack self-healing high-temperature gas valve coating of the present invention does not undergo a phase change process and does not generate new products when the cracks heal, which can ensure the long-term stability of the mechanical properties of the high-temperature gas valve material and achieve spontaneous healing without relying on external excitation.

[0017] The application of the dual electromechanical coupling microcrack self-healing high-temperature gas valve coating of the present invention in high-temperature gas valves realizes the self-healing function of cracks within a critical distance by generating a mutual attractive force through the stress-induced reverse charges formed on the relative crack surfaces in normal temperature environments such as valve molding, storage and transportation; when the valve is in a high-temperature working environment, the strain gradient-induced reverse charges at the crack tip generate a mutual attractive force, realizing the self-healing function of cracks within a critical distance, avoiding the problem of microcracks expanding under the action of high-temperature gas scouring and then being destroyed and failing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of a method for preparing a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to the present application; Figure 2 This is a schematic diagram of the healing principle of a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating for this application; Figure 3 This is the test result diagram of Example 1; Figure 4 This is the test result diagram of Example 3.

[0019] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0021] The first embodiment of the present invention provides a method for preparing a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating, such as Figure 1 As shown, the specific steps include: Step S1: Cold-pressing a crystalline material to form a sheet. The crystalline material is capable of generating a stress-induced reverse charge below a critical switching temperature and a strain-gradient-induced reverse charge above a critical switching temperature. The crystalline material is barium titanate or semiconducting molybdenum disulfide powder, and the particle size of the crystalline material is between 200 nm and 500 nm. The particle size of the barium titanate or semiconducting molybdenum disulfide powder significantly affects the electric field strength generated by the stress-induced reverse charge and the electric field strength generated by the strain-gradient-induced reverse charge. Furthermore, the molybdenum disulfide powder can be semiconducting molybdenum disulfide powder.

[0022] It is worth noting that the critical switching temperature refers to the transition point where the crystal material switches from generating stress-induced reverse charge to generating strain gradient-induced reverse charge. Exemplarily, the critical switching temperature is 100°C~130°C.

[0023] Specifically, the preparation method of the sheet includes: placing the crystal material in a mold, cold pressing it under an axial stress of 200MPa~350MPa for 2min~4min to form a green body; sintering the green body in an environment of a temperature of 1000℃~1400℃ for 3h~5h, and obtaining the sheet after naturally cooling to room temperature.

[0024] In order to ensure the bonding between the coating and the high-temperature gas valve, the sheet and the high-temperature gas valve were treated in advance. The specific treatment method was to polish the sheet with 1000-grit sandpaper and rinse the polished sheet with high-pressure nitrogen for 1 minute to 3 minutes; the high-temperature gas valve was ultrasonically cleaned in deionized water for 10 seconds and then blown dry with high-pressure nitrogen for 3 minutes.

[0025] In step S2, the sheet is used as a solid material source and deposited on the high-temperature gas valve by physical vapor deposition to obtain an initial coating on the surface of the high-temperature gas valve. The deposition temperature is 300°C to 500°C and the deposition time is 60 minutes to 120 minutes. The distance between the high-temperature gas valve and the sheet is 5 mm to 30 mm.

[0026] Specifically, the sheet is fixed on the fixture in the vacuum chamber, and the high-temperature gas valve is fixed, and the vacuum degree in the chamber is pumped to 2×10 -5 Pa~1×10 -4 Pa, the chamber temperature was heated at a rate of 20°C / min to the deposition temperature. After the deposition time, heating was stopped and the chamber temperature was allowed to cool naturally to room temperature, forming an initial coating on the surface of the high-temperature gas valve. It is understood that the thickness of the initial coating can be controlled by adjusting preparation parameters such as the chamber temperature, evaporation time, and the distance between the high-temperature gas valve and the sheet.

[0027] Step S3: performing polarization treatment on the initial coating to obtain a microcrack self-healing coating.

[0028] Specifically, patch electrodes are set on the upper surface of the initial coating and the high-temperature gas valve material, and the positive and negative electrodes are led out for directional polarization. A polarization electric field of 5kV / cm~15kV / cm is applied along the thickness direction of the initial coating. After polarization is completed, the external electric field is removed and the patch electrodes are removed to obtain a micro-crack self-healing coating.

[0029] In this embodiment, a crystalline material is selected that can generate stress-induced reverse charge in an environment below the critical switching temperature and strain gradient-induced reverse charge in an environment above the critical switching temperature. After the crystalline material is prepared into a sheet, it is deposited on the surface of a high-temperature gas valve. Figure 2 As shown in the figure, when cracks appear on the coating surface, in a room temperature environment, stress-induced reverse charges will be formed on the relative crack surfaces to generate a mutual attractive force, thereby realizing the crack self-healing function; when the high-temperature gas valve is in a high-temperature working environment, strain gradient-induced reverse charges will be formed at the crack tip to generate a mutual attractive force, thereby realizing the crack self-healing function; and when the external environment temperature is higher than the critical switching temperature, the crack self-healing function generated by the stress-induced reverse charge attraction can be switched to the crack self-healing function generated by the strain gradient-induced reverse charge attraction, thereby realizing the dual electromechanical coupling microcrack self-healing function; crack healing does not undergo a phase change process and does not generate new products, which can ensure the long-term stability of the mechanical properties of the high-temperature gas valve material, and can achieve spontaneous healing without relying on external excitation, including changes in external conditions such as electric field, temperature change, magnetic field, and stress.

[0030] The reverse charge induced by the strain gradient refers to the inversion symmetry of the crystal destroyed by the non-uniform strain. The positive and negative charge centers inside the crystal no longer coincide, resulting in electric polarization, which can be expressed as , P i For electric polarization, f ijkl is the flexoelectric coefficient tensor component, is the strain gradient tensor component. The stress-induced reverse charge is the reverse charge distribution induced by the polarization phenomenon of non-centrosymmetric crystals under uniform stress, which can be expressed as P i = d ijk σ jk , P i For electric polarization, d ijk is the piezoelectric coefficient tensor component, σ jk are the stress tensor components.

[0031] A second embodiment of the present invention provides a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating, obtained by the above-mentioned preparation method; wherein the coating has a thickness of 0.005μm to 5μm. The coating generates a crack self-healing distance of less than or equal to 80μm and a crack self-healing time of less than or equal to 3ms due to stress-induced reverse charge attraction. The coating generates a crack self-healing distance of less than or equal to 5μm and a crack self-healing time of less than or equal to 0.5ms due to strain gradient-induced reverse charge attraction.

[0032] It is understandable that the high-temperature gas valve is a core component of the solid attitude and orbit control power system, and its reliability and structural integrity determine the service performance of the solid attitude and orbit control power system. High-temperature gas valves are very prone to microcracks during the molding, storage, transportation and use processes. These microcracks are usually difficult to detect and will quickly evolve into pits under the action of high-temperature gas scouring, causing damage, leakage and even cracking of the high-temperature gas valve, reducing the quality stability and service reliability of the solid attitude and orbit control power system. Therefore, the present invention applies the above-mentioned microcrack self-healing coating to high-temperature gas valves to solve the problem that the microcracks generated in the valves of the solid attitude and orbit control power system during the molding, storage, transportation and use processes are expanded under the action of high-temperature gas scouring and then damaged and failed. The details are as follows.

[0033] The third embodiment of the present invention provides an application of a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating in a solid attitude and orbit control engine.

[0034] In this embodiment, the high-temperature gas valve can be a high-temperature gas valve. In normal temperature environments such as valve molding, storage, and transportation, stress-induced opposing charges on opposing crack surfaces generate a mutual attractive force, enabling crack self-healing within a critical distance. In high-temperature operating environments, strain gradients induced by opposing charges at the crack tips generate a mutual attractive force, enabling crack self-healing within a critical distance. This prevents the expansion of the high-temperature gas valve's damage area due to crack propulsion, thereby ensuring thrust accuracy and valve reliability, and thereby improving the long-term operational stability and safety of the solid-state attitude and orbit control propulsion system.

[0035] Example 1 Barium titanate powder with a purity of 99.99% and a particle size of 200 nm was placed in a mold and cold-pressed under an axial stress of 350 MPa for 4 minutes using a cold press to form a green body. The green body was sintered at 1400°C for 5 hours and then naturally cooled to room temperature to obtain a sheet. The sheet was polished with 1000-grit sandpaper and rinsed with high-pressure nitrogen for 1 minute. The high-temperature gas valve was ultrasonically cleaned in deionized water for 10 seconds and then dried with high-pressure nitrogen for 3 minutes. The rinsed sheet was fixed to a fixture in a vacuum chamber, and the high-temperature gas valve was fixed 5 mm away from the sheet. The vacuum degree in the chamber was reduced to 1×10 -4 Pa, the temperature inside the cavity was heated to 500°C at a rate of 20°C / min, held at that temperature for 120 minutes, and then stopped heating and allowed to cool naturally to room temperature, resulting in an initial coating on the surface of the high-temperature gas valve. The thickness of the initial coating was measured at 50 locations using an energy-dispersive X-ray spectrometer, with a calculated average thickness of 4.96 μm. Chip electrodes were placed on the upper surface of the initial coating and on the high-temperature gas valve material, and positive and negative electrodes were introduced for directional polarization. A 15 kV / cm polarization electric field was applied along the thickness direction of the initial coating. After polarization was completed, the applied electric field was removed, and the patch electrodes were removed, resulting in a microcrack self-healing coating.

[0036] The high temperature gas valve coating obtained in this embodiment was simulated and tested, and the results are as follows: Figure 3 As shown in the figure, it can be seen that the cracks have been completely healed.

[0037] Example 2 Semiconducting molybdenum disulfide powder with a purity of 99.995% and a particle size of 500 nm was placed in a mold and cold-pressed for 2 minutes under an axial stress of 200 MPa using a cold press to form a green body. The green body was sintered at 1000°C for 3 hours and then naturally cooled to room temperature to obtain a sheet. The sheet was polished with 1000-grit sandpaper and rinsed with high-pressure nitrogen for 3 minutes. The high-temperature gas valve was ultrasonically cleaned in deionized water for 10 seconds and then dried with high-pressure nitrogen for 3 minutes. The rinsed sheet was fixed to a fixture in a vacuum chamber, and the high-temperature gas valve was fixed 30 mm away from the sheet. The vacuum degree in the chamber was reduced to 2×10 -5Pa, the temperature inside the cavity was heated to 300°C at a rate of 20°C / min, held at that temperature for 60 minutes, and then stopped heating and allowed to cool naturally to room temperature, resulting in an initial coating on the surface of the high-temperature gas valve. The thickness of the initial coating at 50 locations was measured using an energy-dispersive X-ray spectrometer, and the average coating thickness was calculated to be 0.01 μm. Patch electrodes were placed on the upper surface of the initial coating and on the high-temperature gas valve material, and positive and negative electrodes were drawn for directional polarization. A 5 kV / cm polarization electric field was applied along the thickness direction of the initial coating. After polarization was completed, the applied electric field was removed, and the patch electrodes were removed, resulting in a microcrack self-healing coating.

[0038] Example 3 Semiconducting molybdenum disulfide powder with a purity of 99.99% and a particle size of 300 nm was placed in a mold and cold-pressed under an axial stress of 300 MPa for 3 minutes using a cold press to form a green body. The green body was sintered at 1200°C for 4 hours and then naturally cooled to room temperature to obtain a sheet. The sheet was polished with 1000-grit sandpaper and rinsed with high-pressure nitrogen for 2 minutes. The high-temperature gas valve was ultrasonically cleaned in deionized water for 10 seconds and then dried with high-pressure nitrogen for 3 minutes. The rinsed sheet was fixed to a fixture in a vacuum chamber, and the high-temperature gas valve was fixed 20 mm away from the sheet. The vacuum level in the chamber was reduced to 7×10 -5 Pa, the temperature inside the cavity was heated to 400°C at a rate of 20°C / min, held at that temperature for 100 minutes, and then stopped heating and allowed to cool naturally to room temperature, resulting in an initial coating on the surface of the high-temperature gas valve. The thickness of the initial coating at 50 locations was measured using an energy-dispersive X-ray spectrometer, and the average coating thickness was calculated to be 1.98μm. Patch electrodes were placed on the upper surface of the initial coating and on the high-temperature gas valve material, and positive and negative electrodes were introduced for directional polarization. A 1kV / cm polarization electric field was applied along the thickness direction of the initial coating. After polarization was completed, the applied electric field was removed, and the patch electrodes were removed, resulting in a microcrack self-healing coating.

[0039] The high temperature gas valve coating obtained in this embodiment was simulated and tested, and the results are as follows: Figure 4 As shown in the figure, it can be seen that the crack cannot achieve self-healing function and the crack still exists. This is because the polarization electric field strength in this embodiment does not meet the technical requirements, resulting in the inability to generate stress-induced reverse charges on the opposite crack surface.

[0040] Example 4 Semiconducting molybdenum disulfide powder with a purity of 99.995% and a particle size of 400 nm was placed in a mold and cold-pressed under an axial stress of 250 MPa for 4 minutes using a cold press to form a green body. The green body was sintered at 1300°C for 5 hours and then naturally cooled to room temperature to obtain a sheet. The sheet was polished with 1000-grit sandpaper and rinsed with high-pressure nitrogen for 2 minutes. The high-temperature gas valve was ultrasonically cleaned in deionized water for 10 seconds and then dried with high-pressure nitrogen for 3 minutes. The rinsed sheet was fixed to a fixture in a vacuum chamber, and the high-temperature gas valve was fixed 25 mm away from the sheet. The vacuum level in the chamber was reduced to 4×10 -5 Pa, the temperature inside the cavity was heated to 360°C at a rate of 20°C / min, held at that temperature for 10 minutes, and then stopped heating and allowed to cool naturally to room temperature, resulting in an initial coating on the surface of the high-temperature gas valve. The thickness of the initial coating at 50 locations was measured using an energy-dispersive X-ray spectrometer, with a calculated average thickness of 0.003μm. Chip electrodes were placed on the upper surface of the initial coating and on the high-temperature gas valve material, and positive and negative electrodes were introduced for directional polarization. A 15kV / cm polarization electric field was applied along the thickness direction of the initial coating. After polarization was completed, the applied electric field was removed, and the patch electrodes were removed, resulting in a microcrack self-healing coating.

[0041] Since the holding time in this embodiment did not meet the technical requirements, the coating thickness was only 0.003 μm. After the polarization electric field was applied, the coating was broken down and failed, and the dual electromechanical coupling microcrack self-healing function could not be achieved.

[0042] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating, characterized in that: include: Cold pressing a crystalline material to obtain a sheet; wherein the crystalline material can generate a stress-induced reverse charge below a critical switching temperature and a strain gradient-induced reverse charge above a critical switching temperature; Using the sheet as a solid material source, depositing the solid material source on a high-temperature gas valve by a physical vapor deposition method, thereby obtaining an initial coating on the surface of the high-temperature gas valve; Wherein, during the deposition process, the deposition temperature is 300°C to 500°C, and the deposition time is 60min to 120min; The initial coating is subjected to polarization treatment to obtain a micro-crack self-healing coating.

2. The preparation method of the dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to claim 1 is characterized in that: The crystal material is barium titanate or molybdenum disulfide powder.

3. The preparation method of the dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to claim 1 or 2, characterized in that: The preparation method of the sheet comprises: Placing the crystal material in a mold, and cold pressing it under an axial stress of 200 MPa to 350 MPa for 2 to 4 minutes to form a green body; The green body is sintered in an environment with a temperature of 1000° C. to 1400° C. for 3 h to 5 h to obtain a sheet.

4. The preparation method of the dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to claim 1 is characterized in that: The particle size of the crystalline material is 200nm~500nm.

5. The preparation method of the dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to claim 1 is characterized in that: During the deposition process, the distance between the high-temperature gas valve and the sheet is 5 mm to 30 mm.

6. The method for preparing a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to claim 1, characterized in that: The polarization electric field applied during the polarization process is 5 kV / cm to 15 kV / cm.

7. A dual electromechanical coupling microcrack self-healing high-temperature gas valve coating, characterized in that: The coating is obtained by the preparation method according to any one of claims 1 to 6; wherein the thickness of the coating is 0.005 μm to 5 μm.

8. The dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to claim 7 is characterized in that: The microcrack self-healing coating generates a crack self-healing distance of less than or equal to 80 μm and a crack self-healing time of less than or equal to 3 ms through stress-induced reverse charge attraction.

9. The dual electromechanical coupling microcrack self-healing high-temperature gas valve coating according to claim 7, characterized in that: The microcrack self-healing coating generates a crack self-healing distance of less than or equal to 5 μm and a crack self-healing time of less than or equal to 0.5 ms through the reverse charge attraction induced by the strain gradient.

10. Application of a dual electromechanical coupling microcrack self-healing high-temperature gas valve coating in solid attitude and orbit control engines.

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