Multi-layer composite film for aerospace wire and preparation method of multi-layer composite film

Abstract

The invention provides a multi-layer composite film for an aerospace wire and a preparation method of the multi-layer composite film, and relates to the technical field of surface film layers. The preparation method comprises the following steps: placing a wire base material in an electrolyte for micro-arc oxidation treatment so as to form an insulating film on the surface of the wire base material; spraying nano dispersion liquid on the surface of the insulating film to form an intermediate layer; carrying out curing treatment on the middle layer to form a hydrophobic membrane; wherein the electrolyte comprises 5-30 g / L of sodium silicate, 0.1-2 g / L of cubic boron nitride, 2-20 g / L of sodium hexametaphosphate, 0.1-1 g / L of titanium aluminum nitride, 0.1-10 g / L of aluminum nitride and 0.1-2 g / L of sodium hydroxide. The performance of the film layer for the aerospace wire can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of surface film technology, and more specifically, to a multilayer composite film for aerospace wires and a method for preparing the same. Background Technology

[0002] As aerospace vehicles evolve towards lighter weight, higher power density, and higher reliability, aluminum, aluminum alloys, and titanium alloys are gradually becoming alternatives to copper conductors in the cable and wire industry due to their advantages such as light weight, high electrical conductivity, and low price. However, aerospace wires typically operate in extreme service environments, including high altitude and low temperature, humid and hot cycling, radiation, and vibration, which places stringent requirements on the wires' electrical insulation performance, thermal management capabilities, and environmental adaptability.

[0003] Forming dense films on aerospace-grade wires is considered a good way to solve the above problems. However, the films currently prepared have poor performance, and in severe cases, film failure may occur.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this disclosure is to provide a multilayer composite film for aerospace wires and a method for preparing the same, thereby overcoming, at least to some extent, the problem of poor film performance for aerospace wires.

[0006] According to a first aspect of this disclosure, a method for preparing a multilayer composite film for aerospace conductors is provided. The multilayer composite film includes an insulating film on a conductor substrate and a hydrophobic film on the insulating film. The preparation method includes: placing the conductor substrate in an electrolyte for micro-arc oxidation treatment to form an insulating film on the surface of the conductor substrate; spraying a nano-dispersion liquid onto the surface of the insulating film to form an intermediate layer; and curing the intermediate layer to form a hydrophobic film. The electrolyte includes 5-30 g / L sodium silicate, 0.1-2 g / L cubic boron nitride, 2-20 g / L sodium hexametaphosphate, 0.1-1 g / L aluminum titanium nitride, 0.1-10 g / L aluminum nitride, and 0.1-2 g / L sodium hydroxide.

[0007] Optionally, the material of the conductor substrate includes one or more of aluminum-magnesium-silicon alloy, aluminum alloy, aluminum-zirconium alloy, and titanium alloy.

[0008] Optionally, the process parameters for micro-arc oxidation treatment include: voltage of 400~550V, pulse frequency of 50~1000Hz, and treatment time of 5~30min.

[0009] Optionally, the nano-dispersion is an sPTFE nano-dispersion; wherein, in the sPTFE nano-dispersion, polytetrafluoroethylene is suspended in the liquid in a nano-form.

[0010] Optionally, the intermediate layer is cured to form a hydrophobic film, including: placing the intermediate layer at 120~150℃ for 0.5~1h to form a hydrophobic film.

[0011] Optionally, the preparation method further includes cleaning the surface of the wire substrate before placing it in the electrolyte.

[0012] Optionally, the surface cleaning treatment of the conductor substrate includes: ultrasonically cleaning the conductor substrate in anhydrous ethanol for 5-15 minutes; rinsing the ultrasonically cleaned conductor substrate with deionized water; and drying the conductor substrate at 35-60°C after rinsing.

[0013] Optionally, the ultrasonic cleaning frequency is 20~200kHz.

[0014] Optionally, before placing the wire substrate in the electrolyte, the preparation method further includes: subjecting the electrolyte to ultrasonic treatment at a frequency of 20~200kHz for 2~15min.

[0015] According to a second aspect of this disclosure, a multilayer composite film for aerospace wires is provided, prepared using any of the above-described preparation methods.

[0016] According to a third aspect of this disclosure, an aerospace wire having a multilayer composite film is provided, the multilayer composite film being prepared using any of the above-described preparation methods.

[0017] In the exemplary embodiments of this disclosure, cubic boron nitride (cBN), titanium aluminum nitride (Ti4AlN3), and aluminum nitride (AlN) nanofillers are introduced into the micro-arc oxidation process to achieve in-situ composite reinforcement of the ceramic film. Specifically, the electrolyte is composed of sodium silicate (Na2SiO3), cubic boron nitride, sodium hexametaphosphate (NaPO3)6, titanium aluminum nitride, aluminum nitride, and sodium hydroxide (NaOH). Each component is generated synchronously with the oxide layer in the discharge channel and embedded in the film to form a structurally continuous composite layer. Cubic boron nitride provides high hardness and crack resistance to the insulating film, the addition of titanium aluminum nitride improves the toughness and thermal stability of the insulating film, and the addition of aluminum nitride improves the thermal conductivity and insulation of the insulating film. This gives the film a combination of strength, toughness, and heat dissipation capacity, improving the problems of traditional micro-arc oxidation films being hard and brittle with poor thermal conductivity. Specifically, cubic boron nitride has extremely high hardness and thermal stability, and its crystal structure is stable and chemically inert. During micro-arc oxidation, cubic boron nitride particles mechanically embed and partially chemically bond with the alumina matrix under the high-temperature transient environment of the discharge channel, thus acting as a reinforcing skeleton in the film. The high modulus of cubic boron nitride effectively disperses local stress, inhibits microcrack initiation and propagation, and significantly improves the crack resistance and mechanical integrity of the coating. For titanium aluminum nitride, a MAX phase material, it combines the electrical and thermal conductivity of metals with the high-temperature stability of ceramics. Its layered crystal structure provides stress buffering and crack passivation at the microscale, thereby improving the toughness and thermal shock resistance of the film. Simultaneously, titanium aluminum nitride exhibits good interfacial compatibility with the alumina matrix, forming a continuous thermal conductivity pathway and improving the overall thermal conductivity and structural stability of the film. Furthermore, aluminum nitride possesses high thermal conductivity (approximately 200 W·m). -1 ·K -1This is a ceramic material with excellent insulation properties. During discharge, the aluminum nitride precursor can co-grow with alumina to form an Al–O–N transition phase, effectively improving the thermal conductivity and dielectric stability of the film. Its high chemical stability enhances the film's moisture resistance and corrosion resistance, preventing insulation performance degradation during long-term service. Furthermore, spraying a nano-dispersion onto the insulating film forms an outer modified coating, utilizing its low surface energy to create a stable hydrophobic interface, effectively improving the conductor's moisture resistance, anti-icing properties, and insulation stability. The inner in-situ reinforcement (insulating film) and the outer hydrophobic protection (hydrophobic film) work synergistically to construct a composite protection system with mechanical strength, thermal conductivity, and environmental adaptability. Furthermore, using the above technical solution, cubic boron nitride, titanium aluminum nitride, and aluminum nitride, three inorganic nanophases, exhibit significant synergistic enhancement during micro-arc oxidation. The layered structure of titanium aluminum nitride effectively releases thermal stress during partial discharge, alleviating the high-hardness stress concentration problem introduced by cubic boron nitride particles, enabling the film to maintain strength while possessing good toughness. The high thermal conductivity of aluminum nitride fills the space between cubic boron nitride and titanium aluminum nitride, forming a continuous heat conduction network that effectively reduces the thermal resistance of the film and improves heat dissipation. The combined effect of these three elements creates a multi-scale composite structure, achieving a balance and improvement in the coating's strength, toughness, thermal conductivity, and insulation properties. This significantly improves the inherent defects of traditional micro-arc oxidation films, such as brittleness and poor thermal conductivity. Furthermore, the in-situ multiphase doped layer (i.e., the insulating film) provides mechanical and thermal support, while the hydrophobic film provides surface environmental protection. These two layers are compatible at the interface, constructing a composite system of internal reinforcement and external protection. This synergistic structure ensures both the lightweight and flexible requirements of the conductor (or cable) and enhances its safety and reliability under complex service conditions. It solves the technical problems of existing micro-arc oxidation films being prone to cracking under conductor bending, vibration, or thermal cycling loads, thus reducing insulation reliability, and the tendency for conductors to experience localized overheating and insulation breakdown under high power density conditions.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] Figure 1 A flowchart illustrating a method for preparing a multilayer composite film for aerospace wires according to an embodiment of the present disclosure is shown.

[0021] Figure 2 The diagram illustrates a cross-sectional SEM (Scanning Electron Microscope) image of the multilayer composite film prepared in Embodiment 1 of this disclosure.

[0022] Figure 3 A schematic diagram of the surface hydrophobic angle of the multilayer composite membrane prepared according to Embodiment 1 of this disclosure is shown.

[0023] Figure 4 A cross-sectional SEM image of the multilayer composite film prepared according to Embodiment 2 of this disclosure is shown schematically.

[0024] Figure 5 A schematic diagram of the surface hydrophobic angle of the multilayer composite membrane prepared according to Embodiment 2 of this disclosure is shown.

[0025] Figure 6 A cross-sectional SEM image of the multilayer composite film prepared according to Embodiment 3 of this disclosure is shown schematically.

[0026] Figure 7 A schematic diagram of the surface hydrophobic angle of the multilayer composite membrane prepared in Embodiment 3 of this disclosure is shown.

[0027] Figure 8 A cross-sectional SEM image of a conventional micro-arc oxidation film in Comparative Example 1 is shown schematically.

[0028] Figure 9 A schematic diagram of the surface hydrophobic angle of the unmodified membrane layer in Comparative Example 2 is shown. Detailed Implementation

[0029] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced with one or more of these specific details omitted, or other methods, processes, steps, etc., can be employed. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0030] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. The flowcharts shown in the drawings are merely exemplary illustrations and do not necessarily include all steps. For example, some steps may be broken down, while others may be combined or partially combined; therefore, the actual order of execution may change depending on the actual situation. Additionally, all terms such as "first," "second," etc., used below are for distinction purposes only and should not be construed as limiting the content of this disclosure.

[0031] Currently, although organic polymer insulating materials have good flexibility and high temperature resistance, their long-term heat aging resistance is limited, they are flammable or produce harmful gases, and they are prone to moisture absorption or performance degradation in low temperature and humid environments, making it difficult to fully meet the needs of aerospace applications.

[0032] Plasma Electrolytic Oxidation (PEO) technology can form a dense ceramic film in situ on the surface of aluminum and titanium alloys, possessing both corrosion resistance and electrical insulation properties, and is considered a green and efficient method for conductor insulation. However, traditional PEO films still have many problems in aerospace cable applications. Because the film is mainly composed of alumina ceramic phase, which is hard and brittle, the conductor is prone to cracking under bending, vibration, or thermal cycling loads, thereby reducing insulation reliability. At the same time, conventional alumina films have limited thermal conductivity, and the conductor is prone to local overheating under high power density conditions, which can easily lead to insulation breakdown.

[0033] To address or at least mitigate the technical problems of micro-arc oxide film layers cracking easily under conductor bending, vibration, or thermal cycling loads, thereby reducing insulation reliability, and conductors being prone to local overheating and insulation breakdown under high power density conditions, this disclosure provides a novel multilayer composite film for aerospace conductors and its preparation method.

[0034] In an exemplary embodiment of this disclosure, a multilayer composite film for aerospace conductors may include an insulating film on a conductor substrate and a hydrophobic film on the insulating film.

[0035] Figure 1 A flowchart illustrating a method for preparing a multilayer composite film for aerospace conductors according to an embodiment of this disclosure is shown schematically. (Reference) Figure 1 The method for preparing a multilayer composite film for aerospace wires according to the present disclosure may include the following steps: S12. The conductor substrate is placed in an electrolyte for micro-arc oxidation treatment to form an insulating film on the surface of the conductor substrate.

[0036] In exemplary embodiments of this disclosure, the material of the conductor substrate includes one or more of aluminum-magnesium-silicon alloy, aluminum alloy, aluminum-zirconium alloy, and titanium alloy.

[0037] The electrolyte can be composed of sodium silicate, cubic boron nitride, sodium hexametaphosphate, aluminum titanium nitride, aluminum nitride, and sodium hydroxide. Specifically, the electrolyte includes 5-30 g / L sodium silicate, 0.1-2 g / L cubic boron nitride, 2-20 g / L sodium hexametaphosphate, 0.1-1 g / L aluminum titanium nitride, 0.1-10 g / L aluminum nitride, and 0.1-2 g / L sodium hydroxide.

[0038] For example, the content of sodium silicate can be 5 g / L, 20 g / L or 30 g / L, the content of cubic boron nitride can be 0.1 g / L, 1 g / L or 2 g / L, the content of sodium hexametaphosphate can be 2 g / L, 15 g / L or 20 g / L, the content of aluminum titanium nitride can be 0.1 g / L, 0.5 g / L or 1 g / L, the content of aluminum nitride can be 0.1 g / L, 5 g / L or 10 g / L, and the content of sodium hydroxide can be 0.1 g / L, 1 g / L or 2 g / L.

[0039] The process parameters for micro-arc oxidation treatment may include: voltage of 400~550V, pulse frequency of 50~1000Hz, and treatment time of 5~30min.

[0040] For example, the voltage can be 400V, 480V or 550V, the pulse frequency can be 50Hz, 500Hz or 1000Hz, and the processing time can be 5min, 20min or 30min.

[0041] The insulating film prepared in this embodiment has a thickness of 5-30 μm. This effectively balances the film's insulation, mechanical toughness, and thermal conductivity. It avoids the risks of pinholes and breakdown that are common with thinner films, while also preventing the increased brittleness, decreased flexibility, and impeded heat dissipation that can occur with thicker films.

[0042] S14. Spray a nano-dispersion onto the surface of the insulating film to form an intermediate layer.

[0043] In an exemplary embodiment of this disclosure, the nanodispersion can be an sPTFE nanodispersion. In this sPTFE nanodispersion, polytetrafluoroethylene is suspended in the liquid in a nano-form.

[0044] The thickness of the intermediate layer is 0.2~5μm.

[0045] S16. The intermediate layer is cured to form a hydrophobic film.

[0046] In an exemplary embodiment of this disclosure, the intermediate layer can be kept at 120~150°C for 0.5~1h to form a hydrophobic film. For example, the curing temperature can be 120°C, 135°C or 150°C, and the holding time can be 0.5h, 0.8h or 1h.

[0047] According to some embodiments of this disclosure, the surface of the wire substrate may be cleaned before placing it in the electrolyte.

[0048] First, the conductor substrate is ultrasonically cleaned in anhydrous ethanol for 5-15 minutes. Next, the ultrasonically cleaned conductor substrate is rinsed with deionized water and then dried at 35-60°C. Specifically, the ultrasonic cleaning frequency can be 20-200 kHz.

[0049] According to some embodiments of this disclosure, before placing the wire substrate in the electrolyte, the electrolyte can be ultrasonically treated at a frequency of 20-200 kHz for 2-15 minutes. This avoids or prevents the agglomeration of nanoparticles in the electrolyte, thereby preparing a uniform multilayer composite film with better insulation on the surface of the alloy substrate. For example, the ultrasonic treatment time of the electrolyte can be 2 minutes, 10 minutes, or 15 minutes, and the ultrasonic treatment frequency can be 20 kHz, 100 kHz, or 200 kHz.

[0050] The static contact angle of the surface after coating with the nano-dispersion is greater than 120°. The resistivity of the final multilayer composite film is greater than 100MΩ.

[0051] Furthermore, this disclosure also provides a multilayer composite film for aerospace wires, which is prepared using the above-described preparation method.

[0052] Furthermore, this disclosure also provides an aerospace wire with a multilayer composite film, which is prepared using the above-described preparation method.

[0053] The scheme of Embodiment 1 of this disclosure will be described below.

[0054] Step 1, Substrate pretreatment.

[0055] In this embodiment, aluminum-magnesium-silicon alloy is selected as the conductor substrate. The conductor substrate is placed in an ultrasonic cleaning tank and cleaned with anhydrous ethanol for 15 minutes. Then it is rinsed with deionized water to remove residual ethanol. It is then ultrasonically cleaned with ethanol for 5 minutes to remove surface impurities and oil. The substrate is then taken out and placed in an oven at 50°C for 10 minutes to dry for later use.

[0056] Step 2: Micro-arc oxidation to prepare functional coatings.

[0057] First, the electrolyte is prepared. Specifically, it is mainly based on a silicate system, with nanofiller precursors added as needed. The electrolyte formulation in this embodiment is as follows: sodium silicate 5 g / L, cubic boron nitride 0.1 g / L, sodium hexametaphosphate 2 g / L, titanium aluminum nitride 0.1 g / L, aluminum nitride 0.1 g / L, and sodium hydroxide 0.1 g / L.

[0058] Next, micro-arc oxidation is performed. Specific process parameters include: voltage of 400V, pulse frequency of 50Hz, and processing time of 5 minutes. The thickness of the micro-arc oxidation layer obtained in this embodiment is controlled at 5μm. After the micro-arc oxidation treatment, the layer is rinsed with deionized water and dried with compressed air.

[0059] Step 3: Hydrophobic modified outer layer coating and low-temperature curing.

[0060] First, an sPTFE nano-dispersion was prepared and applied to the surface of the insulating film prepared above by spraying. The outer layer thickness was 0.2 μm.

[0061] Next, the hydrophobic layer is cured at 120°C for 0.5 hours.

[0062] See Figure 2 The multilayer composite film prepared in this embodiment exhibits discharge pores and cracks on its surface, with relatively continuous film layers in localized areas and good interfacial bonding. The insulation resistance of the corresponding sample at room temperature is approximately 160 MΩ. The results indicate that the film layer formed under low-energy discharge exhibits good uniformity and meets insulation performance standards, satisfying the requirements for long-term aerospace service.

[0063] refer to Figure 3 The surface hydrophobic angle of the multilayer composite film obtained in this embodiment is about 140°, which shows a strong hydrophobic state.

[0064] The scheme of Embodiment 2 of this disclosure will be described below.

[0065] Step 1, Substrate pretreatment.

[0066] In this embodiment, aluminum-magnesium-silicon alloy is selected as the conductor substrate. The conductor substrate is placed in an ultrasonic cleaning tank and cleaned with anhydrous ethanol for 15 minutes. Then it is rinsed with deionized water to remove residual ethanol. It is then ultrasonically cleaned with ethanol for 5 minutes to remove surface impurities and oil. The substrate is then taken out and placed in an oven at 45°C for 10 minutes to dry for later use.

[0067] Step 2: Micro-arc oxidation to prepare functional coatings.

[0068] First, the electrolyte is prepared. Specifically, it is mainly based on a silicate system, with nanofiller precursors added as needed. The electrolyte formulation in this embodiment is as follows: sodium silicate 20 g / L, cubic boron nitride 1 g / L, sodium hexametaphosphate 10 g / L, aluminum titanium nitride 0.5 g / L, aluminum nitride 5 g / L, and sodium hydroxide 1 g / L.

[0069] Next, micro-arc oxidation is performed. Specific process parameters include: voltage of 500V, pulse frequency of 500Hz, and processing time of 15 minutes. The thickness of the micro-arc oxidation layer obtained in this embodiment is controlled at 15μm. After the micro-arc oxidation treatment, the layer is rinsed with deionized water and dried with compressed air.

[0070] Step 3: Hydrophobic modified outer layer coating and low-temperature curing.

[0071] First, an sPTFE nano-dispersion was prepared and applied to the surface of the insulating film prepared above by spraying. The outer layer thickness was 3 μm.

[0072] Next, the hydrophobic layer was cured at 130°C for 0.8 hours.

[0073] See Figure 4 The multilayer composite membrane prepared in this embodiment has continuous and uniform thickness, and tight interfacial bonding. The uniformly distributed cubic boron nitride and titanium aluminum nitride particles in the membrane significantly improve the toughness and crack resistance of the membrane. The insulation resistance of the corresponding sample at room temperature is approximately 220 MΩ. After damp heat cycling, it remains above 180 MΩ, indicating stable electrical performance.

[0074] refer to Figure 5 The surface hydrophobic angle of the multilayer composite film obtained in this embodiment is about 151°, which shows a strong hydrophobic state.

[0075] The scheme of Embodiment 3 of this disclosure will be described below.

[0076] Step 1, Substrate pretreatment.

[0077] In this embodiment, aluminum-magnesium-silicon alloy is selected as the conductor substrate. The conductor substrate is placed in an ultrasonic cleaning tank and cleaned with anhydrous ethanol for 15 minutes. Then it is rinsed with deionized water to remove residual ethanol. It is then ultrasonically cleaned with ethanol for 5 minutes to remove surface impurities and oil. The substrate is then taken out and placed in an oven at 45°C for 10 minutes to dry for later use.

[0078] Step 2: Micro-arc oxidation to prepare functional coatings.

[0079] First, the electrolyte is prepared. Specifically, it is mainly based on a silicate system, with nanofiller precursors added as needed. The electrolyte formulation in this embodiment is as follows: sodium silicate 30 g / L, cubic boron nitride 2 g / L, sodium hexametaphosphate 20 g / L, aluminum titanium nitride 1 g / L, aluminum nitride 10 g / L, and sodium hydroxide 2 g / L.

[0080] Next, micro-arc oxidation is performed. Specific process parameters include: voltage 500V, pulse frequency 1000Hz, and processing time 30 minutes. After micro-arc oxidation, the sample is rinsed with deionized water and dried with compressed air.

[0081] Step 3: Hydrophobic modified outer layer coating and low-temperature curing.

[0082] First, an sPTFE nano-dispersion was prepared and applied to the surface of the insulating film prepared above by spraying. The outer layer thickness was 3 μm.

[0083] Next, the hydrophobic layer is cured at 150°C for 1 hour.

[0084] See Figure 6 The multilayer composite film prepared in this embodiment has an increased pore size and a slightly rougher surface, corresponding to an insulation resistance of approximately 200 MΩ at room temperature. Increasing the discharge energy to thicken the film layer is beneficial for improving the surface insulation resistance.

[0085] refer to Figure 7 The surface hydrophobic angle of the multilayer composite film obtained in this embodiment is about 156°, which shows a strong hydrophobic state.

[0086] The scheme of Comparative Example 1 of this disclosure is described below.

[0087] Step 1, Substrate pretreatment.

[0088] Aluminum-magnesium-silicon alloy was selected as the conductor substrate. The conductor substrate was placed in an ultrasonic cleaning tank and cleaned with anhydrous ethanol for 15 minutes. It was then rinsed with deionized water to remove residual ethanol, and then ultrasonically cleaned with ethanol for 5 minutes to remove surface impurities and oil. The substrate was then removed and placed in an oven at 50°C for 10 minutes to dry for later use.

[0089] Step 2: Micro-arc oxidation to prepare functional coatings.

[0090] First, prepare the electrolyte. Specifically, the electrolyte formula is as follows: sodium silicate 30g / L, sodium hexametaphosphate 20g / L, sodium hydroxide 2g / L.

[0091] Next, micro-arc oxidation is performed. Specific process parameters include: voltage 550V, pulse frequency 1000Hz, and processing time 30 minutes. After micro-arc oxidation, the sample is rinsed with deionized water and dried with compressed air.

[0092] Step 3: Hydrophobic modified outer layer coating and low-temperature curing.

[0093] First, an sPTFE nano-dispersion was prepared and applied to the surface of the insulating film prepared above by spraying. The outer layer thickness was 5 μm.

[0094] Next, the hydrophobic layer is cured at 150°C for 1 hour.

[0095] See Figure 8 The film prepared in Comparative Example 1 has obvious pores and cracks, and large-area defects and peeling occur in local areas. The coating is discontinuous and uneven. Delamination / interface fracture traces can be seen at the interface between the coating and the substrate.

[0096] The scheme of Comparative Example 2 of this disclosure is described below.

[0097] Step 1, Substrate pretreatment.

[0098] Aluminum-magnesium-silicon alloy was selected as the conductor substrate. The conductor substrate was placed in an ultrasonic cleaning tank and cleaned with anhydrous ethanol for 15 minutes. It was then rinsed with deionized water to remove residual ethanol, and then ultrasonically cleaned with ethanol for 5 minutes to remove surface impurities and oil. The substrate was then removed and placed in an oven at 50°C for 10 minutes to dry for later use.

[0099] Step 2: Micro-arc oxidation to prepare functional coatings.

[0100] First, prepare the electrolyte. Specifically, the electrolyte formula is as follows: sodium silicate 30g / L, cubic boron nitride 2g / L, sodium hexametaphosphate 20g / L, aluminum titanium nitride 1g / L, aluminum nitride 10g / L, and sodium hydroxide 2g / L.

[0101] Next, micro-arc oxidation is performed. Specific process parameters include: voltage 550V, pulse frequency 1000Hz, and processing time 30 minutes. After micro-arc oxidation, the sample is rinsed with deionized water and dried with compressed air.

[0102] See Figure 9 The static water contact angle of the membrane prepared in Comparative Example 2 is significantly smaller than that of the sPTFE-coated sample in the above-described embodiments of this disclosure. The contact angle of Comparative Example 2 is <40°, which is significantly lower than the hydrophobic threshold of 120°, indicating that the surface of the sample in Comparative Example 2 is hydrophilic or has a hydrophilic tendency and is prone to forming a water film.

[0103] It should be noted that although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0104] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of this disclosure and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0105] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0106] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for preparing a multilayer composite film for aerospace conductors, characterized in that, The multilayer composite film includes an insulating film on a conductor substrate and a hydrophobic film on the insulating film; wherein, the preparation method includes: The conductor substrate is placed in an electrolyte for micro-arc oxidation treatment to form an insulating film on the surface of the conductor substrate. A nano-dispersion liquid is sprayed onto the surface of the insulating film to form an intermediate layer; The intermediate layer is cured to form a hydrophobic film; The electrolyte comprises 5-30 g / L sodium silicate, 0.1-2 g / L cubic boron nitride, 2-20 g / L sodium hexametaphosphate, 0.1-1 g / L aluminum titanium nitride, 0.1-10 g / L aluminum nitride, and 0.1-2 g / L sodium hydroxide.

2. The preparation method according to claim 1, characterized in that, The material of the conductor substrate includes one or more of aluminum-magnesium-silicon alloy, aluminum alloy, aluminum-zirconium alloy, and titanium alloy.

3. The preparation method according to claim 1, characterized in that, The process parameters for micro-arc oxidation include: voltage of 400~550V, pulse frequency of 50~1000Hz, and processing time of 5~30min.

4. The preparation method according to claim 1, characterized in that, The nano-dispersion is an sPTFE nano-dispersion; In the sPTFE nanodispersion, polytetrafluoroethylene is suspended in the liquid in a nano-form.

5. The preparation method according to claim 1, characterized in that, The intermediate layer is cured to form a hydrophobic film, comprising: The intermediate layer is kept at 120~150℃ for 0.5~1h to form a hydrophobic film.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The preparation method further includes, prior to placing the wire substrate in the electrolyte: The surface of the conductor substrate is cleaned.

7. The preparation method according to claim 6, characterized in that, The surface cleaning process for the conductor substrate includes: The conductor substrate was ultrasonically cleaned in anhydrous ethanol for 5-15 minutes. The conductive substrate after ultrasonic cleaning was rinsed with deionized water and then dried at 35~60℃.

8. The preparation method according to claim 7, characterized in that, The frequency of ultrasonic cleaning is 20~200kHz.

9. The preparation method according to any one of claims 1 to 5, characterized in that, The preparation method further includes, prior to placing the wire substrate in the electrolyte: The electrolyte is subjected to ultrasonic treatment at a frequency of 20~200kHz for 2~15 minutes.

10. A multilayer composite film for aerospace conductors, characterized in that, The multilayer composite film for aerospace conductors was prepared using the method described in any one of claims 1 to 9.

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